Internal combustion engine

Abstract

A gaseous fuel internal combustion engine includes: an engine structure including a cylinder block, a crankcase, and a gearbox; a pump for discharging blow-by gas contained in the crankcase and positioned adjacent to the engine structure; and a passage extending from one of the crankcase and the gearbox to the pump such that the pump is in fluid flow communication with the crankcase.

Description

Technical Field

[0001] The present teachings relate to internal combustion engines, in particular gaseous fuel internal combustion engines. Additionally, the present teachings relate to oil pre-separators and oil separation systems. Background Art

[0002] In an internal combustion engine, the air and fuel in the combustion chamber of a cylinder, as well as the combustion gases formed therein, typically escape from the combustion chamber to a limited extent, flow past the piston and into the engine's crankcase. This gas is commonly referred to as blow-by gas.

[0003] In engines powered by gaseous fuels, such as hydrogen, the accumulation of the gaseous fuel component of blowby gases in the crankcase can cause problems if ventilation is inadequate. This is because some gaseous fuels have a relatively high flammability range (for example, the flammable concentration of hydrogen in air is between 4% and 75%). Unless the blowby gases are ventilated to bring the concentration of gaseous fuel in the crankcase below its lower flammability limit, there is a risk that the gaseous fuel in the crankcase could ignite, potentially damaging the engine and its surroundings. The gaseous fuel could then also ignite the lubricating oil in the crankcase, initiating further combustion.

[0004] The transition to low-carbon or zero-carbon fuel sources is underway to meet environmental legislation. The present inventors have recognized that during this transition, in certain applications, such as off-highway machinery (such as construction and agricultural work machines) and generators, conventional fuel (typically diesel) internal combustion engine versions of the work machines will be manufactured alongside alternative fuel machines (such as those fueled by hydrogen). Manufacturing multiple versions of a machine can be expensive and inefficient if the overall structure of the engines differs and the engines have different spatial envelopes and need to be packaged differently within the machine during assembly.

[0005] Diesel-powered engines have lower ventilation requirements for blowby gases. Therefore, if a base engine is designed to run on either diesel or hydrogen, packaging a crankcase ventilation system (CCV) that meets the requirements of hydrogen fuel without making the entire engine heavier than a diesel-fueled engine can be problematic.

[0006] The present teachings attempt to overcome or at least alleviate one or more problems associated with the prior art. Summary of the Invention

[0007] According to a first aspect of the present teachings, there is provided a gaseous fuel internal combustion engine comprising: a crankcase; and a ventilation system or pump configured to vent blow-by gases contained within the crankcase.

[0008] An engine may include an engine structure. The engine structure may include a crankcase and a cylinder head coupled to one or more cylinders. A ventilation system may include a gas pressure source and a ventilation path. The gas pressure source may be configured to deliver ventilation gas from a gas inlet along the ventilation path to the crankcase, and to deliver a combination of the ventilation gas and blowby gas including gaseous fuel as expelled gas from the crankcase via a separate outlet.

[0009] The ventilation path may be configured to deliver ventilation gas from the gas inlet to the cylinder head and then to the crankcase.

[0010] Advantageously, routing ventilation gas from the gas inlet to the crankcase via the cylinder head helps reduce the concentration of blowby gases in the cylinder head, thereby reducing exposure of components in the cylinder head to the blowby gases. By reducing exposure of components in the cylinder head to the blowby gases, the risk of exposure-related damage to these components (e.g., damage caused by hydrogen embrittlement) is reduced.

[0011] The gas pressure source may be a pump.

[0012] Advantageously, using a pump as the gas pressure source can enable better control of the flow rate of the exhaust gas. In addition, providing the gas pressure source as a pump can enable greater flexibility in the location where the pump can be positioned in the engine.

[0013] The pump may include an impeller rotatable about an axis. The axis may be arranged to be substantially vertical in the normal operating orientation of the engine. For example, the axis of the impeller may be substantially parallel to the axis of one or more cylinders.

[0014] Advantageously, this orientation of the impeller may assist in draining oil from the pump.

[0015] The gas pressure source may include two pumps.

[0016] The two pumps can be arranged in parallel.

[0017] Advantageously, this can ensure that the gas flow through the pump is shared substantially equally and therefore the pump loading is substantially uniform.

[0018] The two pumps may be arranged symmetrically with respect to the flow divider upstream thereof.

[0019] The ventilation path may include one or more gas flow passages in the engine structure for delivering ventilation gas from the cylinder head to the crankcase.

[0020] Advantageously, such a ventilation path can help reduce the concentration of blowby gases in the engine structure.In addition, such a ventilation path eliminates the need to deliver ventilation gases to the crankcase using a conduit located outside the engine which may have a greater risk of damage.

[0021] The ventilation path may include a plurality of gas flow passages distributed across the crankcase.

[0022] Advantageously, such a ventilation path helps to increase the flow rate of ventilation gas that can be delivered to the crankcase.In addition, distributing the gas flow passage across the crankcase helps to distribute the ventilation gas throughout the crankcase.

[0023] The one or more gas flow passages may include one or more oil drain passages for draining oil from the cylinder head to the crankcase.

[0024] Advantageously, using one or more oil drain passages as gas flow passages helps flush blowby gases from the increased volume of the engine structure. Additionally, it helps simplify engine manufacture because the engine may not need to be designed to include a dedicated gas flow passage between the cylinder head and the crankcase.

[0025] The one or more gas flow passages may include all oil drain passages in the cylinder head.

[0026] Advantageously, including all oil drain passages in the cylinder head helps increase the flow of ventilation gases that can be delivered to the crankcase and avoids the build-up of pockets of combustible blow-by gases.

[0027] The engine structure may further include a cylinder block (cylinder group) including one or more cylinders. The cylinder block may include an oil drain passage. The one or more gas flow passages may include an oil drain passage of the cylinder block located downstream of the cylinder head and upstream of the crankcase.

[0028] The engine may further include a rocker cover mounted to the cylinder head. A ventilation path may pass through the rocker cover to reach the cylinder head.

[0029] Advantageously, having a ventilation path through the rocker cover may help reduce the concentration of blowby gases between the rocker cover and the cylinder head.

[0030] The rocker cover may include a baffle configured to substantially span the cylinder head to disperse the flow of ventilation gas routed along the ventilation path.

[0031] Advantageously, the baffles can help distribute the ventilation gases to a gas flow path distributed across the cylinder head leading to the crankcase. In addition, the baffles can help inhibit the ventilation gases from interfering with the lubrication of components housed in the rocker cover.

[0032] The rocker cover may include a single rocker cover inlet in the ventilation path.The gas pressure source may be configured to deliver ventilation gas along the ventilation path from the gas inlet to the rocker cover inlet and then to the cylinder head.

[0033] Advantageously, this configuration of the rocker cover and ventilation paths helps to simplify the manufacture of the engine.

[0034] The outlet may comprise an outflow portion of the ventilation path. Sections of the outflow portion may be arranged in the engine structure.

[0035] Advantageously, this configuration of the outflow portion can help inhibit freezing of the blowby gases due to the elevated temperatures of the engine structure during operation. This is particularly beneficial when the gaseous fuel is hydrogen, as the blowby gases may include a relatively high concentration of water vapor as a byproduct of hydrogen combustion.

[0036] The outflow portion may terminate above one or more cylinders.

[0037] The engine structure may further include a gearbox, a cylinder block and a rocker cover. The outflow portion may pass through one or more of the gearbox, the cylinder block, the cylinder head and the rocker cover.

[0038] Advantageously, such a configuration may help improve packaging of the outflow portion and may avoid the need for ductwork external to the engine, which may be susceptible to damage.

[0039] The outflow portion may pass in series (continuously) through at least the cylinder block, the cylinder head, and the rocker cover.

[0040] Advantageously, such a configuration may help to improve the packaging of the outflow portion.

[0041] The outflow can pass through the cylinder head.

[0042] Advantageously, such a configuration may help to improve the packaging of the outflow portion.

[0043] The gas pressure source may be configured to generate a subatmospheric pressure in the crankcase; optionally, in the range of -100 to -10 millibars (mbar) relative to atmospheric pressure; for example, in the range of -80 to -20 mbar relative to atmospheric pressure.

[0044] Advantageously, creating a sub-atmospheric pressure in the crankcase helps inhibit blow-by gases from flowing from the crankcase to other components of the engine via a path separate from the outlet.

[0045] The gas pressure source may be located downstream of the crankcase.

[0046] The ventilation system may include an oil separator configured to reduce the concentration of oil in the exhaust gases delivered from the crankcase.

[0047] Advantageously, an oil separator can help remove oil from the exhaust gas before it is exhausted to the atmosphere or supplied to one or more cylinders of the engine. This can have environmental and / or emissions benefits and can also reduce the amount of oil consumed by the engine, thereby saving replacement costs.

[0048] The engine may further comprise an oil passage arranged to deliver oil removed from the exhaust gas by the oil separator to the crankcase.

[0049] The oil separator may be a passive oil separator.

[0050] Advantageously, such an oil separator may help reduce parasitic losses in the engine.

[0051] The oil separator may be a cyclonic oil separator.

[0052] The oil separator may be a labyrinth oil separator.

[0053] An oil separator may be arranged downstream of the gas pressure source.

[0054] Advantageously, this arrangement of the oil separator and gas pressure source may assist in returning oil removed from the exhaust gas by the oil separator to the crankcase.

[0055] An oil separator can be installed to the gas pressure source.

[0056] The inlet of the oil separator may be arranged below the outlet of the gas pressure source.

[0057] Advantageously, this may assist in separating the oil from the exhaust gases.

[0058] The outlet of the oil separator may be above the inlet of the oil separator.

[0059] Advantageously, this may assist in separating the oil from the exhaust gases.

[0060] The gas pressure source may be located downstream of the crankcase. The ventilation system may include an oil pre-separator located upstream of the gas pressure source and / or the oil separator. The oil pre-separator may be configured to reduce the concentration of oil in exhaust gas delivered from the crankcase to the gas pressure source and / or the oil separator.

[0061] Advantageously, the oil pre-separator may help reduce the amount of oil in the exhaust gas flowing through the gas air pressure source, which may help improve the efficiency of the gas pressure source and / or reduce damage to the gas pressure source.

[0062] Additionally, some oil separators may operate more efficiently when the oil concentration at their inlet is below a certain level, so a combination of a pre-separator and a separator may be particularly effective in removing oil.

[0063] The oil pre-separator may be a passive oil pre-separator.

[0064] The oil pre-separator may include one or more baffles.

[0065] The engine may further include an intake system configured to supply air to one or more cylinders. The ventilation system may be configured to deliver exhaust gas to the intake system for supply to the one or more cylinders via an outlet (eg, via an outflow portion of the ventilation path).

[0066] Advantageously, this configuration of the intake and ventilation systems may help improve the fuel efficiency of the engine and / or reduce emissions.

[0067] The gas inlet may be in fluid communication with an air supply source. The air intake system may include an air intake passage arranged to deliver air from the gas inlet to the one or more cylinders. The ventilation system may be configured to draw air from the air intake passage into the ventilation path as ventilation gas at a first location.

[0068] Advantageously, this configuration of the air intake system and the ventilation system eliminates the need for a separate dedicated gas inlet for the ventilation system.

[0069] In embodiments where the engine includes a rocker cover mounted to the cylinder head, the first location of the intake passage may be located adjacent the rocker cover.The ventilation path may pass through the rocker cover.

[0070] Advantageously, this configuration of the rocker cover and intake passage may help reduce the length of exposed ducting external to the engine structure between the first location and the rocker cover, which may otherwise be at higher risk of damage and / or freezing at low ambient temperatures.

[0071] The engine may further comprise a compressor along the intake passage. The first position may be upstream of the compressor.

[0072] Advantageously, this configuration of the compressor and ventilation system may help reduce the pressure of the ventilation air flowing along the ventilation path toward the crankcase, and may therefore help the gas pressure source generate a sub-atmospheric pressure in the crankcase.

[0073] The compressor may be a turbocharger or a supercharger.

[0074] The gas pressure source may be configured to generate a lower pressure in the crankcase relative to the pressure at the compressor inlet.

[0075] The compressor may be configured to generate a pressure of -60 to 0 mbar relative to atmospheric pressure at the compressor inlet.

[0076] The ventilation system may be configured to exhaust the exhaust gas from the outlet to a second location in the intake passage, such as via an outflow portion of the ventilation path. The second location may be downstream of the first location relative to the intake passage.

[0077] Advantageously, this configuration of the intake system and the ventilation system suppresses exhaust gas discharged into the intake passage from flowing along the ventilation path to the crankcase.

[0078] The second location may be upstream of the compressor relative to the intake passage.

[0079] In embodiments where the engine includes a rocker cover mounted to the cylinder head, the second location of the intake passage may be located adjacent the rocker cover.The outlet may include an outlet passage through the rocker cover.

[0080] Advantageously, this configuration of the rocker cover and intake passage may help reduce the length of exposed ducting external to the engine structure between the second location and the rocker cover, which may otherwise be at higher risk of damage and / or freezing at low ambient temperatures.

[0081] The gas inlet may include a filter.

[0082] Advantageously, the filter helps prevent dust, debris, etc. from entering the cylinder head and crankcase.

[0083] The gaseous fuel may be hydrogen. The internal combustion engine may be fueled substantially only by hydrogen.

[0084] Advantageously, hydrogen produces fewer harmful emissions than some other gaseous fuels.

[0085] The ventilation system may include a gas pressure source configured to deliver ventilation gas from the gas inlet to the crankcase via the ventilation path.The gas pressure source may be configured to generate a sub-atmospheric pressure in the crankcase.

[0086] The negative pressure may be in the range of -100 to -10 mbar relative to atmospheric pressure; alternatively, in the range of -80 to -20 mbar relative to atmospheric pressure.

[0087] The gas pressure source may be located downstream of the crankcase.

[0088] The gas pressure source may be a pump.

[0089] An engine may include an engine structure. The engine structure may include a crankcase. The ventilation system may include a gas pressure source and a ventilation path. The gas pressure source may be configured to deliver ventilation gas from a gas inlet to the crankcase along an inflow portion of the ventilation path, and to deliver a combination of the ventilation gas and blowby gases including gaseous fuel as exhaust gas from the crankcase via a separate outlet. The outlet may include an outflow portion of the ventilation path. At least one section of the inflow portion and / or at least one section of the outflow portion may be received within the engine structure.

[0090] The engine structure may include a cylinder head coupled to one or more cylinders. A section of the inflow portion and / or a section of the outflow portion may pass through the cylinder head.

[0091] The engine structure may include a cylinder block including one or more cylinders. A cylinder head may be mounted to the cylinder block. A section of the inflow portion and / or a section of the outflow portion may pass through the cylinder block.

[0092] The engine structure may further include a rocker cover mounted to the cylinder head. A section of the inflow portion and / or a section of the outflow portion may pass through the rocker cover.

[0093] The engine may further comprise a gearbox.The outflow portion may begin at the gearbox.

[0094] In embodiments where the gas pressure source is a pump, the pump may be configured to convey blowby gases comprising gaseous fuel contained within the crankcase therefrom to the outlet. The engine may include a controller configured to control the pump output based on one or more determined operating parameters of the engine.

[0095] Advantageously, controlling the pump output based on one or more determined operating parameters of the engine enables control of the flow of blowby gases so that the concentration of gaseous fuel in the crankcase is below its lower flammability limit within the engine's operating range while minimizing engine parasitic losses.

[0096] The one or more determined operating parameters may include one or more of engine speed and engine torque.

[0097] Advantageously, it has been found that this operating parameter of the engine is indicative of the flow rate of blowby gases into the crankcase.

[0098] The controller may be configured to control the pump based on one or more determined operating parameters via a lookup table or map stored in memory.

[0099] Advantageously, controlling the pump via a lookup table or map helps to simplify control of the pump by the controller.

[0100] The pump may be a variable speed pump.The controller may be configured to control the speed of the pump based on one or more determined operating parameters.

[0101] Advantageously, controlling the speed of the pump can help ensure that the flow of the leaked gas is accurately controlled.

[0102] The controller may be configured to determine a set-point pump speed based on the one or more determined operating parameters.The controller may be configured to control the speed of the pump to substantially correspond to the set-point pump speed.

[0103] Advantageously, this configuration of the controller enables a pump speed to be achieved by the controller which helps to ensure that the concentration of gaseous fuel in the crankcase is below its lower flammability limit.

[0104] The controller may be configured to control the pump output based on a setpoint flow of exhaust gas downstream of the crankcase or ventilation gas upstream of the crankcase, or based on a setpoint parameter representing the flow of exhaust gas downstream of the crankcase or ventilation gas upstream of the crankcase.

[0105] Advantageously, controlling the pump output based on a determined flow rate of exhaust gas or ventilation gas, or based on a parameter representative of the exhaust gas or ventilation gas, can help provide more accurate control of the flow rate of exhaust gas / ventilation gas, and therefore provide more accurate control of the hydrogen concentration in the crankcase.

[0106] The controller may be configured to determine a setpoint parameter representing a flow rate of exhaust gas downstream of the crankcase or ventilation gas upstream of the crankcase. The controller may be configured to monitor an actual parameter representing a flow rate of exhaust gas downstream of the crankcase or ventilation gas upstream of the crankcase. The controller may be configured to control the pump output such that the actual parameter representing the flow rate substantially corresponds to the setpoint parameter representing the flow rate.

[0107] Advantageously, by feeding back the monitored actual parameter representative of flow to the controller in a closed loop manner, the controller may help provide more accurate control of the exhaust / ventilation gas flow, and therefore the hydrogen concentration in the crankcase.

[0108] The controller can be configured to output an alarm signal when the difference between the actual value and the set point value exceeds a predetermined threshold, for example, when the difference between the actual value of the flow rate and the set point value of the flow rate is greater than a predetermined threshold, or when the difference between the actual parameter representing the flow rate and the set point parameter representing the flow rate is greater than a predetermined threshold.

[0109] Advantageously, this configuration of the controller may help monitor for obstructions or blockages (eg, due to ice formation) in the flow path of the blowby gas.

[0110] The engine may be configured to shut down when the controller outputs an alarm signal.

[0111] The parameter representing the flow rate may correspond to the pressure difference of the exhaust gas or the ventilation gas.

[0112] Advantageously, the differential pressure of the exhaust or ventilation gases may be determined via relatively low-cost sensors (eg, pressure transducers).

[0113] The pressure differential of the exhaust gas or ventilation gas may correspond to a pressure differential across a flow restrictor in the flow path of the ventilation gas upstream of the crankcase or the exhaust gas downstream of the crankcase.

[0114] Advantageously, determining the pressure difference of the exhaust or ventilation gas across the flow restrictor enables the exact flow rate of said gas to be determined.

[0115] The flow restrictor may be located downstream of the pump.

[0116] The engine may further include a first pressure take-off point and a second pressure take-off point. The pressure differential may correspond to a pressure difference between the first pressure take-off point and the second pressure take-off point. The first pressure take-off point may be spaced upstream from the flow restrictor. The second pressure take-off point may be spaced downstream from the flow restrictor.

[0117] Advantageously, this configuration of the first and second pressure extraction points may help increase the measured pressure differential, which may help determine a more accurate flow rate.

[0118] The flow restrictor may be located downstream of the pump.The first pressure extraction point may be adjacent to the outlet of the pump.

[0119] The distance along the flow path between the first and second pressure extraction points may be at least twice (eg, three or more times, or four or more times) the distance along the flow path between the inlet and outlet of the restrictor.

[0120] The flow restrictor may be an oil separator configured to reduce the concentration of oil in the exhaust gas downstream of the crankcase.

[0121] Advantageously, using the oil separator as a flow restrictor eliminates the need for a separate flow restrictor in the flow path of the exhaust gas.

[0122] The oil separator may include an inlet and an outlet. The inlet may include a first pressure extraction point, and the outlet may include a second pressure extraction point. The pressure differential may correspond to a pressure difference between the first pressure extraction point and the second pressure extraction point.

[0123] The controller may determine a maximum set-point pump speed or a maximum set-point flow rate when the one or more determined operating conditions correspond to a maximum output torque of the engine and / or a (maximum) speed of the engine.

[0124] Advantageously, it has been found that the maximum flow of blow-by gases into the crankcase substantially corresponds to the maximum output torque and / or speed of the engine. Therefore, determining such a maximum set-point pump speed helps provide effective control of the exhaust gas flow rate across the entire operating envelope of the engine.

[0125] The maximum output torque of the engine may be at an engine speed within the range of 1000 to 2500 RPM, optionally within the range of 1100 to 1400 RPM, for example approximately 1150 to 1200 RPM.

[0126] The pump may be an electric pump.

[0127] The pump may be a side channel pump.

[0128] The pump may be positioned downstream of the crankcase such that the pump creates a sub-atmospheric pressure in the crankcase.

[0129] The pump may be configured to generate a pressure in the crankcase in the range of -100 to -10 mbar relative to atmospheric pressure, alternatively in the range of -80 to -20 mbar relative to atmospheric pressure.

[0130] Advantageously, creating a sub-atmospheric pressure in the crankcase helps inhibit blow-by gases from flowing from the crankcase to other components of the engine via a path separate from the outlet.

[0131] The ventilation system may include a gas pressure source and a ventilation path. The gas pressure source may be configured to convey blowby gas, including gaseous fuel, contained within the crankcase, out of the crankcase via the ventilation path as exhaust gas. The ventilation system may also include a monitoring system configured to monitor an actual parameter representing the flow rate of the exhaust gas. The monitoring system may be configured to provide one or more outputs based on the monitored actual parameter.

[0132] Advantageously, monitoring the flow rate of exhaust gas may enable a determination of whether the concentration of gaseous fuel in the crankcase is above its lower flammability limit without requiring a gas concentration sensor in the crankcase.

[0133] Furthermore, by monitoring the flow of exhaust gases, it may be determined whether there are any blockages or obstructions in the ventilation path (eg, due to ice formation) that could result in an unintended increase in the concentration of gaseous fuel in the crankcase.

[0134] The monitored actual parameter may correspond to a pressure difference between the first portion and the second portion of the ventilation path.The first portion and the second portion may both be in the inflow portion, or both in the outflow portion.

[0135] Advantageously, this pressure differential can be determined via a relatively low-cost sensor (eg, a pressure transducer).

[0136] The ventilation path may include a flow restrictor configured to create a pressure differential.

[0137] Advantageously, using a flow restrictor to create a pressure differential may enable the exact flow rate of the exhaust gas to be determined.

[0138] The monitoring system may include a first pressure extraction point and a second pressure extraction point in the ventilation path. The pressure differential may correspond to a pressure difference between the first pressure extraction point and the second pressure extraction point. The first pressure extraction point may be spaced upstream from the flow restrictor. The second pressure extraction point may be spaced downstream from the flow restrictor.

[0139] Advantageously, this configuration of the first and second pressure extraction points may help increase the measured pressure differential, which may help determine a more accurate flow rate.

[0140] The flow restrictor may be located downstream of the gas pressure source.The first pressure extraction point may be adjacent to an outlet of the gas pressure source.

[0141] The distance along the ventilation path between the first and second pressure extraction points may be at least twice (eg, three or more times, or four or more times) the distance along the ventilation path between the inlet and outlet of the restrictor.

[0142] The flow restrictor may be an oil separator configured to reduce the concentration of oil in the exhaust gas in the ventilation path.

[0143] Advantageously, using the oil separator as a flow restrictor eliminates the need for a separate flow restrictor in the ventilation path.

[0144] The oil separator may be a passive oil separator.

[0145] Advantageously, such an oil separator may help reduce parasitic losses in the engine.Furthermore, using a passive oil separator may help simplify the determination of the flow rate of the exhaust gas based on the pressure differential, as compared to an active oil separator.

[0146] The oil separator may be a cyclonic oil separator configured to form a vortex in the exhaust gas traveling between its inlet and outlet portions so that oil carried by the exhaust gas is separated therefrom. The cyclonic oil separator may generate a pressure drop between the inlet and outlet portions.

[0147] Advantageously, the use of a cyclonic oil separator to reduce the concentration of oil in the exhaust gas to be provided allows the oil separator to be a passive component, thereby reducing system complexity and avoiding the need for an external power source. Cyclonic oil separators are particularly effective when used in gaseous fuel engines due to the higher ventilation gas flow rates of gaseous fuel engines compared to, for example, diesel engines.

[0148] The cyclonic oil separator may include a chamber having a frustoconical portion. The inlet portion may include an inlet conduit leading to the chamber in a substantially tangential direction. The monitoring system may include a first pressure extraction point in fluid flow communication with the inlet conduit.

[0149] The outlet portion may comprise a tube extending within the chamber, the tube extending to an outlet conduit located outside the chamber.The monitoring system may comprise a second pressure extraction point in fluid flow communication with the outlet conduit.

[0150] The first pressure extraction point and the second pressure extraction point may be located adjacent to each other.

[0151] Advantageously, positioning the first and second pressure extraction points adjacent to each other may help simplify connecting the pressure extraction points to one or more pressure sensors.

[0152] The monitoring system may include at least one pressure transducer in fluid flow communication with the first pressure extraction point and the second pressure extraction point.

[0153] The gas pressure source may be a pump.

[0154] Advantageously, the pump may enable more precise control of the flow rate of exhaust gas.

[0155] The pump may be located downstream of the crankcase such that the pump creates a sub-atmospheric pressure in the crankcase.

[0156] Advantageously, creating a sub-atmospheric pressure in the crankcase helps inhibit blow-by gases from flowing from the crankcase to other parts of the engine via a path separate from the ventilation path.

[0157] An oil separator may be arranged downstream of the pump.

[0158] Advantageously, this configuration of the oil separator and pump may facilitate delivery of oil removed from the exhaust gas by the oil separator to the crankcase.

[0159] An oil separator may be mounted to the pump.

[0160] Advantageously, mounting the oil separator to the pump may enable the oil separator and pump to be pre-assembled, which may increase the speed of assembly of the engine overall.

[0161] The one or more outputs may include a control output.The monitoring system may be configured to control the pump output via the control output.

[0162] Advantageously, controlling the pump output based on the monitored parameters may enable closed-loop control of the flow rate of exhaust gas.

[0163] The pump may be a variable speed pump.The monitoring system may be configured to control the speed of the pump via the control output.

[0164] Advantageously, controlling the speed of the pump can help ensure accurate control of the flow rate of exhaust gas.

[0165] The one or more outputs may include an alarm output. The monitoring system may provide an alarm output when the difference between the actual value and the set point value exceeds a predetermined threshold, for example, when the difference between the actual value of the flow rate and the set point value of the flow rate is greater than a predetermined threshold, or when the actual parameter representing the flow rate and the set point parameter representing the flow rate are greater than a predetermined threshold.

[0166] Advantageously, such a configuration of the monitoring system may help prevent the concentration of gaseous fuel in the crankcase from rising above its lower flammability limit, for example due to a blockage or obstruction in the ventilation path (eg, due to ice formation).

[0167] The monitoring system may be configured to determine a setpoint parameter representing a flow threshold value based on one or more determined operating parameters of the engine.

[0168] Advantageously, such a configuration of the monitoring system may enable the parameter representing the flow rate threshold to be based on the expected flow rate of the exhaust gas in accordance with one or more determined operating parameters.

[0169] The one or more determined operating parameters may include one or more of engine speed and engine torque.

[0170] Advantageously, these operating parameters of the engine have been found to be indicative of the flow rate of blow-by gases (including gaseous fuel) flowing into the crankcase.

[0171] The engine may be configured to shut down when the monitoring system provides an alarm output.

[0172] Advantageously, this configuration of the engine may help prevent the concentration of gaseous fuel in the crankcase from rising above its lower flammability limit.

[0173] The engine may include an engine structure including a cylinder block, a crankcase, and optionally a gearbox. The pump may be positioned adjacent the engine structure. The engine may include a passage extending from one of the crankcase and the gearbox to the pump, such that the pump is in fluid flow communication with the crankcase.

[0174] Advantageously, this arrangement minimizes the spatial extent required for the engine as a whole, if equipped with a crankcase ventilation system.

[0175] The pump may be positioned adjacent to a side of the engine structure.

[0176] Advantageously, if a crankcase ventilation (CCV) system is included, this arrangement further minimizes the space required for the entire engine. In particular, gaseous fuel engines (such as hydrogen-fueled engines) typically do not require a fuel injection pump because the gas is already supplied at a pressure greater than the fuel injection pressure, so a pump is not needed to pressurize it. This location is typically where such a pump is installed on liquid fuel engines, thus becoming available for other uses in gaseous fuel engines.

[0177] The pump can be positioned to the side of the cylinder block in front of the gearbox.

[0178] The pump may be mounted to the engine structure.

[0179] Advantageously, this simplifies installation of the CCV system since the pump is supplied with the engine as a single unit.

[0180] The gearbox may extend laterally at least a greater distance than the cylinder block.The pump may be positioned at least partially within a spatial extent defined by an imaginary longitudinal projection of the front of the gearbox.

[0181] This arrangement further minimizes the overall spatial extent required for the pump.

[0182] The pump can be installed completely within this range.

[0183] The engine may further comprise one or more auxiliary components mounted to the engine structure, such as one or more of a lubricating oil filler, a lubricating oil cooler, an inlet manifold and / or an electronic control unit. The pump may project laterally less than or equal to the maximum width of one or more of the auxiliary components.

[0184] This arrangement may result in an engine that does not require a different installation envelope than an equivalent engine fueled by liquid (eg, diesel).

[0185] The pump may occupy a spatial extent of less than or equal to 200 mm in the longitudinal direction (x), and / or (less than or equal to) 240 mm in the vertical direction (z), and / or (less than or equal to) 175 mm in the transverse direction (y).

[0186] The passage may include an oil pre-separator upstream of the pump.

[0187] The oil pre-separator may be mounted adjacent to the engine structure (eg, the gearbox).

[0188] Advantageously, this mounting arrangement of the oil pre-separator may help improve packaging of the engine.

[0189] A passage may extend between the pump and an aperture in the gearbox.

[0190] Advantageously, the outlet passage in this configuration can be shorter, thereby reducing material usage and cost.

[0191] The aperture may be located in a forward facing wall of the gearbox.

[0192] In a liquid fuel engine, the orifice is generally provided in a location for transmitting driving force from a gearbox to a fuel injection pump, and thus the orifice can be reused without rebuilding the engine.

[0193] The aperture may be located above a cam gear mounted to a camshaft of the engine.

[0194] This position may minimize the amount of lubricating oil that splashes toward the orifice and, therefore, the amount that is carried into the pump and potentially exhausted with the exhaust gases.

[0195] The passage may terminate in an oil pre-separator located within the gearbox.

[0196] This further minimizes oil that flows into the pump and potentially escapes with the exhaust gases.

[0197] The pre-separator may comprise an extraction duct defining a mouth for extracting gas from the gearbox.The pre-separator may comprise a plate axially spaced from and covering an opening of the extraction duct.

[0198] This pre-separator arrangement has been found to be effective for removing oil from the exhaust gas.

[0199] The plate may include an angled portion arranged to extend from an axially spaced position and terminate at an edge that is at least axially aligned with or axially overlaps the mouth, the edge being laterally spaced from the mouth.

[0200] This pre-separator arrangement has been found to be effective for removing oil from the exhaust gas.

[0201] The plate may include a flat portion covering the mouth. The angled portion may extend around the periphery of the flat portion.

[0202] The mouth may terminate in outward-turned lips.

[0203] This separator arrangement has been found to be effective for removing oil from the exhaust gas.

[0204] The pre-separator may comprise a flow diverter extending around at least a portion of the extraction conduit to divert oil flowing down the wall of the gearbox away from an opening of the extraction conduit.

[0205] The ratio between the diameter or minimum width of the plate and the diameter of the extraction conduit can be between about 4:1 and 2.5:1, for example about 3:1. For example, the diameter of the plate can be about 66 mm and the diameter of the extraction conduit can be about 22 mm. The angled portion of the plate can terminate at an axial spacing of about 5-6 mm from an adjacent wall (e.g., a wall of a diverter). The outwardly turned lip can have a larger spacing from the corresponding wall, for example at least 8 mm. The lip can extend beyond the inner diameter of the extraction conduit by about at least 6 mm, for example 9 mm, to define a lip of at least 2 mm, for example 4 mm.

[0206] The pump inlet may face laterally outward.

[0207] It has been found that this provides a compact arrangement for the pump.

[0208] The pump may include an impeller. The impeller may rotate about an impeller rotation axis.

[0209] The impeller rotation axis may be arranged substantially in the longitudinal direction of the engine.

[0210] It has been found that this provides a compact arrangement for the pump.

[0211] The impeller axis of rotation may be substantially vertical in the normal operating orientation of the engine.

[0212] Advantageously, this orientation of the impeller may aid in draining oil from the pump.

[0213] The impeller axis of rotation may be substantially parallel to the axis of one or more cylinders of the engine.

[0214] The pump may be a side channel pump.

[0215] The pump may include a first inlet and a second inlet with corresponding first and second vortex generators immediately upstream of the first and second inlets.

[0216] Advantageously, it has been found that the use of a vortex generator immediately upstream of the pump inlet makes the pump operate more efficiently.

[0217] The pump may include a substantially right angle flow turn in the conduit immediately upstream of the inlet.

[0218] Vortex generators may be located at the ends of the passages.

[0219] The engine may further include an oil separator in fluid flow communication with the pump and located downstream of the pump.

[0220] An oil separator is provided to enable a reduction in oil consumption of the engine, which has environmental and cost benefits.

[0221] The oil separator may be located longitudinally between the forward facing wall of the gearbox and the pump.

[0222] This positioning provides a compact arrangement of the oil separator and pump and minimizes the length and complexity of the interconnecting pipe-runs.

[0223] The longitudinal dimension of the spatial extent occupied by the pump and the oil separator may be less than or equal to 200 mm.

[0224] The oil separator may include a gas outlet. A conduit may extend from the gas outlet to a separate chamber in the gearbox.

[0225] Using part of the gearbox as the outlet further minimises pipe runs and may mean that the risk of heat generated in the engine freezing the liquid and restricting gas flow is minimised. The oil separator is positioned close to the gearbox to allow easy access to this chamber.

[0226] The oil separator may further comprise an oil outlet. A conduit may extend from the oil outlet back to the crankcase or gearbox.

[0227] Advantageously, this positioning places the oil separator close to the crankcase and gearbox, allowing for short piping from the oil outlet.

[0228] The pump may be a self-contained unit having a drive motor, such as an electric drive motor.

[0229] This arrangement further minimizes the required spatial extent.

[0230] The gaseous fuel may be hydrogen.

[0231] The inherent properties of hydrogen as a fuel tend to carry a greater risk of its lower flammability limit being exceeded, with a consequent high ventilation requirement to avoid this happening. Therefore, the present ventilation arrangement enables this to be achieved in a space-saving manner while ensuring safety.

[0232] The engine may be a hydrogen-fueled internal combustion engine. The ventilation system may include a cyclonic oil separator arranged to receive exhaust gas including blowby gas. The cyclonic oil separator may be configured to cause a flow of exhaust gas therethrough to form a vortex, and oil carried by the exhaust gas is separated from the exhaust gas by the vortex.

[0233] Advantageously, a cyclonic oil separator is used to reduce the concentration of oil in the exhaust gas to be supplied, and since the oil separator is a passive component, the complexity of the system is reduced and the need for an external power source is avoided. Cyclonic oil separators are particularly effective when used in gaseous fuel engines, as these have inherently higher gas flows than, for example, diesel engines to keep unburned fuel below its lower flammability limit.

[0234] The cyclonic oil separator may include a chamber having a truncated cone portion. The truncated cone portion may define a longitudinal axis of the truncated cone portion. The truncated cone portion may include an apex and a roof distal to the apex. The roof may define a roof plane. The cyclonic oil separator may include a separator inlet through which exhaust gas is introduced into the chamber, the inlet defining an inlet longitudinal axis. The inlet longitudinal axis may be oriented to form a non-zero angle with the roof plane. The inlet longitudinal axis may be oriented toward the apex so that a flow of exhaust gas flowing through the inlet is directed toward the apex.

[0235] It has been found that orienting the inlet of the cyclonic oil separator towards the apex of the separator advantageously improves the flow of exhaust gas through the separator.

[0236] The inlet longitudinal axis may be oriented at an angle of between 1° and 45° to the plane of the roof.

[0237] The inlet longitudinal axis may be oriented at an angle of between 10° and 35° to the plane of the roof.

[0238] It has been found that orienting the inlet at an angle within these ranges advantageously results in improved turbulence and, therefore, improved separation of the oil from the exhaust gases.

[0239] The separator may comprise an exhaust gas outlet through which the exhaust gas exits the chamber downstream of the vortex.

[0240] The ventilation system may include an extraction point for the pressure transducer at the inlet and an extraction point for the pressure transducer at the outlet.

[0241] Providing extraction points for pressure transducers at the inlet and outlet allows monitoring of the pressure differential between the inlet and outlet of the cyclonic oil separator.

[0242] The inlet pressure transducer extraction point and the outlet pressure transducer extraction point may be located at the first end of the separator.

[0243] Locating the inlet and outlet pressure transducer extraction points together at the first end of the separator allows for a more compact arrangement and more easily allows a single pressure transducer to be used if required.

[0244] The inlet pressure transducer extraction point and the outlet pressure transducer extraction point may each define a transducer extraction longitudinal axis.The transducer extraction longitudinal axes may be substantially parallel to each other.

[0245] Having the inlet and outlet pressure transducer extraction points parallel to each other also advantageously results in a compact arrangement.

[0246] The inlet pressure transducer extraction point and the outlet pressure transducer extraction point may be adjacent to each other.

[0247] The inlet and outlet pressure transducer extraction points being adjacent to each other again advantageously allows for a compact arrangement. This is particularly important in systems of this type where the available space is limited.

[0248] The ventilation system may include one or more pressure transducers for determining the difference between the pressure of the exhaust gas at the inlet and the pressure of the exhaust gas at the gas outlet.

[0249] The or each transducer may be mounted to a separator.

[0250] Mounting the or each transducer to the separator advantageously provides a compact arrangement and may reduce the number of components required.

[0251] The or each transducer may be mounted to a component remote from the separator.

[0252] Thus, the or each transducer may advantageously be mounted to a component that is less exposed to vibrations.

[0253] The chamber may include a cylindrical portion adjacent to the frustoconical portion and defining a cylindrical portion longitudinal axis. The cylindrical portion may be distal to the apex. The gas outlet may include a tube extending within the chamber.

[0254] The tube may define a tube longitudinal axis. The tube longitudinal axis may be at an angle of 10° or less to the cylindrical portion longitudinal axis.

[0255] The tube longitudinal axis may make an angle of 5° or less with the cylindrical portion longitudinal axis.

[0256] The tube longitudinal axis may be substantially parallel to the cylindrical portion longitudinal axis.

[0257] The tube longitudinal axis may be coaxial with the cylindrical portion longitudinal axis.

[0258] The tube may be a substantially cylindrical tube.

[0259] The outer tube diameter may be in the range of 17 mm to 45 mm.

[0260] A tube of this shape and size improves the flow of exhaust gases through the chamber and facilitates the exit of exhaust gases from the chamber. In particular, the corresponding shape of the outside of the tube and the inside of the cylindrical portion of the chamber improves vortex flow.

[0261] The tube may extend within the chamber for between one quarter and one third of the length of the cylindrical portion.

[0262] The tube may extend within the chamber for between one quarter and one third of the length of the chamber.

[0263] Advantageously, this relative length of the tube facilitates the exit of exhaust gas from the cyclonic oil separator.

[0264] The gas outlet may comprise an outlet orifice defined by the chamber.The outlet orifice may be located at an upper end of the chamber, distal from the apex.

[0265] This location of the outlet orifice advantageously assists the exit of exhaust gases from the chamber.

[0266] The frustoconical portion of the oil separator may have a maximum inner diameter in the range of 30 mm to 80 mm.

[0267] The frustoconical portion may have a height in the range of 50 mm to 200 mm.

[0268] It has been found that the cyclonic oil separator is effective while being relatively compact, as indicated by the above dimensions. Thus, the cyclonic oil separator can be advantageously installed in a compact space while providing effective and useful separation of oil from the exhaust gas.

[0269] The truncated cone portion may be a right circular truncated cone portion.

[0270] The truncated cone portion may be an oblique circular truncated cone portion.

[0271] It has been found that either conical shape provides effective vortex flow.The shape of the truncated cone portion can be adjusted to suit the available space.

[0272] The chamber may include a cylindrical portion adjoining the truncated cone portion and defining a longitudinal axis of the cylindrical portion. The truncated cone portion may be defined by a wall. The angle between the wall and the longitudinal axis of the cylindrical portion may be in the range of 0° to 30°.

[0273] The maximum angle of the wall with the longitudinal axis of the cylindrical portion may be in the range of 15° to 30°. The minimum angle of the wall with the longitudinal axis of the cylindrical portion may be in the range of 0° to 25°.

[0274] The longitudinal axis of the frustoconical portion may make an angle of 0° to 30° with the longitudinal axis of the cylindrical portion.

[0275] Such dimensions have been found to provide an effective separator whilst allowing the separator to fit into the relatively small spatial dimensions required.

[0276] The oil separator may include an oil outlet. The oil outlet may be located at the apex.

[0277] The oil outlet may define an oil longitudinal axis. The oil outlet longitudinal axis may make an angle of 0° to 45° with the longitudinal axis of the frustoconical portion.

[0278] This position and angle of the oil outlet allows the oil to leave the separator by gravity and thus return to the crankcase for reuse. The angle of the oil outlet and the angle of the frustoconical portion allow the separator to fit into the required spatial confines while remaining effective.

[0279] The ventilation system may comprise a controller arranged to control the variable output pump, thereby controlling the flow rate of exhaust gas.

[0280] Controlling the flow rate of the exhaust gas allows the concentration of the gaseous fuel to be controlled to be below the lower flammability limit of the exhaust gas throughout the operating range of the engine.

[0281] The controller may be configured to control the output of the pump based on operating parameters of the engine.

[0282] The controller may be configured to control the output of the pump based on load / output torque and / or engine speed.

[0283] Advantageously, it has been found that both engine speed and engine torque provide a good indication of the flow of blowby gases into the crankcase.

[0284] The controller may be configured to control the pump such that a maximum flow rate of exhaust gas is at an engine speed of 1000 rpm to 2500 rpm.

[0285] The controller may be configured to control the pump such that a maximum flow rate of exhaust gas is at an engine speed of 1100 rpm to 1400 rpm.

[0286] The controller may be configured to control the pump such that a maximum flow rate of exhaust gas is at an engine speed of 1150 rpm to 1200 rpm.

[0287] For engines of the type described herein, the maximum output torque of the engine is typically at engine speeds within this range.

[0288] At an exhaust gas flow rate of at least 30 l / min per liter of engine displacement through the oil separator, a reduction in oil concentration of at least a factor of 10 can be achieved.

[0289] At an exhaust gas flow rate of at least 60 l / min per liter of engine displacement through the oil separator, a reduction in oil concentration of at least a factor of 10 can be achieved.

[0290] At an exhaust gas flow rate of at least 30 l / min per liter of engine displacement through the oil separator, a reduction in oil concentration of at least 20 times can be achieved.

[0291] At an exhaust gas flow rate of at least 60 l / min per liter of engine displacement through the oil separator, a reduction in oil concentration of at least 20 times can be achieved.

[0292] Such flow rates per litre of engine displacement are typical for engines of the type described herein.

[0293] Engine displacement can range from 0.75L to 1.5L per cylinder.

[0294] This engine displacement per cylinder is typical for engines of the type described herein for off-highway / work machine applications.

[0295] The oil separator may include a first molded portion and a second molded portion.

[0296] Advantageously, the oil separator can be molded into the desired shape and size and is easy to assemble.

[0297] The separator may be made of a plastic material.

[0298] Plastic materials are easily molded into desired shapes.

[0299] The separator may be made of a composite material of plastic material and conductive material.

[0300] Advantageously, such a composite material allows for insulation of components while still providing electrical conductivity to avoid electrostatic differences between components connected to the oil separator.

[0301] The engine may be a hydrogen-fueled internal combustion engine. The engine may include an engine structure comprising at least a cylinder head, a cylinder block, and a crankcase. The ventilation system may include at least one auxiliary component mounted directly or indirectly to the engine structure. The at least one auxiliary component may be formed from a composite material. The composite material may include a plastic material and a conductive material, such that the composite material is configured to dissipate electrical charge.

[0302] Advantageously, this composite material allows for insulation of components while still providing electrical conductivity to avoid static differences between components connected to the oil separator, thereby reducing the likelihood of sparks from static discharge.

[0303] The at least one auxiliary component may include an oil pre-separator, an oil separator, a manifold, a conduit and / or a pump housing.

[0304] Making one or more of these components from composite materials improves electrical conductivity while providing insulation, thereby reducing the potential for sparking.

[0305] Composite materials can be conductive materials embedded in plastic materials.

[0306] This material can be molded to provide the required components. This material has the required degree of inherent conductivity while providing insulation. Advantageously, no additional steps are required to provide conductivity.

[0307] The composite material may comprise between 20% and 40% conductive material.

[0308] The composite material may comprise between 25% and 35% conductive material.

[0309] The composite material may comprise substantially 30% electrically conductive material.

[0310] This percentage range of conductive material has been found to provide the desired conductivity while also providing insulation.

[0311] The conductive material may be formed from strands, for example, where the conductive material is a filamentary or wire portion.

[0312] Conductive material, such as carbon fibres, may be embedded in the plastic material in such strand form to provide a composite material.

[0313] The conductive material may be in the form of a powder.

[0314] For conductive materials such as, for example, graphite, a powder form may be advantageously used to embed the conductive material within the plastic material.

[0315] The plastic material may be at least partially coated with an electrically conductive material.

[0316] The plastic material may be at least partially coated with an electrically conductive material at its inner surface.

[0317] At least partially coated plastics material provides an alternative means of providing electrical conductivity as well as insulation.

[0318] The conductive material may be carbon fiber.

[0319] The conductive material may be graphite.

[0320] The conductive material may be a metallic conductive material.

[0321] A range of conductive materials can be embedded within plastic materials or used to coat plastic materials to provide composite materials.

[0322] The ventilation system may have electrical continuity throughout the ventilation system.

[0323] Advantageously, the likelihood of sparks due to electrostatic discharge is reduced.

[0324] An internal combustion engine may include an electrical conductivity monitoring system configured to monitor the conductivity of a ventilation system.

[0325] The conductivity monitoring system may include at least one sensor.

[0326] Providing a conductivity monitoring system advantageously allows the conductivity of the entire system to be monitored so that a warning can be provided if static charge buildup occurs at a certain point in the system and the likelihood of sparking increases.

[0327] According to a second aspect of the present teachings, there is provided a crankcase ventilation system for an internal combustion engine including a crankcase, the system optionally comprising: an inlet for supplying ventilation gas to dilute blow-by gases entering the crankcase from one or more combustion chambers of the engine; and / or an electrically driven pump for moving gas through the system to an outlet; and / or a pump control system for regulating the flow of gas through the system in dependence on the level of blow-by generation by the engine to maintain the concentration of flammable blow-by gases below a lower flammability limit; and / or an oil separator for removing oil from the blow-by gases upstream of the outlet; and / or a pressure differential measuring device for pump control and / or system diagnosis and / or system function monitoring.

[0328] A pump may be located in the system downstream of the crankcase to create a negative pressure in the crankcase relative to atmospheric pressure.

[0329] A pump may be located in the system upstream of the crankcase to create a positive pressure in the crankcase relative to atmospheric pressure.

[0330] The outlet may be in fluid flow communication with an air inlet leading to one or more combustion chambers of the engine such that exhaust gases including ventilation gases and blowby gases are introduced into the air inlet.

[0331] The vent may release exhaust gases, including ventilation gases and blowby gases, to the atmosphere.

[0332] The pump control system may include a controller configured to derive the blowby gas generation level from one or more determined operating parameters of the engine.

[0333] The one or more determined operating parameters may include one or more of engine speed and engine torque.

[0334] The controller may be configured to determine a setpoint pump output based on the one or more determined operating parameters, and to control the output of the pump to substantially correspond to the setpoint pump speed.

[0335] The controller may be configured to control the pump output based on a setpoint flow of exhaust gas downstream of the crankcase or ventilation gas upstream of the crankcase, or based on a setpoint parameter representing the flow of exhaust gas downstream of the crankcase or ventilation gas upstream of the crankcase.

[0336] The differential pressure measuring device may be arranged to measure the differential pressure across the oil separator.

[0337] The pump may be a side channel pump.

[0338] The side channel pump may have a first inlet and a second inlet, and the first and second vortex generators may be positioned immediately upstream of the respective first and second inlets.

[0339] The crankcase ventilation system may further include a ventilation path including an inflow portion extending between the inlet and the crankcase. The inflow portion may extend from the inlet via the cylinder head to the crankcase.

[0340] The inflow portion may include one or more air flow passages in the cylinder head and / or crankcase for conveying ventilation air from the cylinder head to the crankcase.

[0341] The inflow portion may include a plurality of airflow passages distributed across the crankcase.

[0342] The crankcase ventilation system may further include a rocker cover mounted to the cylinder head. A ventilation path may pass through the rocker cover to reach the cylinder head.

[0343] The outlet may comprise an outflow portion of the ventilation path, and sections of the outflow portion may be arranged in one or more of a gearbox, a cylinder block, a cylinder head and a rocker cover of the engine.

[0344] The outflow portion may terminate above one or more cylinders of the engine.

[0345] The oil separator may be a cyclonic oil separator.

[0346] The oil separator may include a chamber having a truncated cone portion. The truncated cone portion may define a longitudinal axis of the truncated cone portion. The truncated cone portion may include an apex and a cap distal to the apex. The cap may define a cap plane. The oil separator may include a separator inlet through which exhaust gas is introduced into the chamber. The inlet may define an inlet longitudinal axis. The inlet longitudinal axis may be oriented at a non-zero angle relative to the cap plane. The inlet longitudinal axis may be oriented toward the apex such that exhaust gas flow through the inlet is directed toward the apex.

[0347] The crankcase ventilation system may further include an oil pre-separator located upstream of the oil separator.

[0348] The oil pre-separator may be mounted to the wall of the crankcase.

[0349] The engine may further include a gearbox, and the oil pre-separator may be mounted to a wall of the gearbox.

[0350] The oil pre-separator may comprise a mouth for extracting gas from the crankcase or gearbox through a wall of the crankcase or gearbox.The oil pre-separator may comprise a plate axially spaced from and covering the mouth.

[0351] The pump may be positioned upstream of the oil separator and downstream of the oil pre-separator.

[0352] The crankcase ventilation system may further include an engine structure. The engine structure may include at least a crankcase, a cylinder block, and a gearbox. The pump may be positioned adjacent to the engine structure. The outlet passage may include a conduit extending from one of the crankcase and the gearbox to the pump.

[0353] The pump may be positioned adjacent a side of the engine structure, such as a side of the cylinder block, forward of the gearbox.

[0354] The gearbox may extend laterally a greater distance than at least the cylinder block.The pump may be positioned at least partially within a spatial extent defined by an imaginary longitudinal projection of the front of the gearbox.

[0355] The pump can be installed completely within this range.

[0356] The pump may occupy a spatial extent of less than or equal to 200 mm in the longitudinal direction (x), and / or (less than or equal to) 240 mm in the vertical direction (z), and / or (less than or equal to) 175 mm in the transverse direction (y).

[0357] The crankcase ventilation system may include at least one component formed from a composite material. The composite material may be composed of a plastic material and a conductive material, such that the composite material is configured to dissipate electrical charge.

[0358] According to a third aspect of the present teachings, there is provided a hydrogen fueled internal combustion engine comprising a crankcase ventilation system according to the second aspect.

[0359] According to a fourth aspect of the present teachings, there is provided a method of controlling the flow of exhaust gas delivered from a crankcase of a gaseous fuel internal combustion engine, the exhaust gas comprising gaseous fuel, the engine comprising a pump arranged to deliver the exhaust gas from the crankcase to an outlet, the method comprising the steps of:

[0360] determining one or more operating parameters of the engine; and optionally

[0361] The pump output is controlled based on the one or more determined operating parameters.

[0362] The method may further comprise the following steps:

[0363] determining an actual parameter representing the flow rate of exhaust gas downstream of the crankcase or ventilation gas upstream of the crankcase;

[0364] determining a set point parameter representing a flow rate of exhaust gas downstream of the crankcase or ventilation gas upstream of the crankcase based on the one or more determined operating parameters; and

[0365] The pump output is controlled such that an actual parameter representative of flow rate substantially corresponds to a set point parameter representative of flow rate.

[0366] According to a fifth aspect of the present teachings, there is provided a pump assembly, the pump assembly comprising:

[0367] Side channel pump, comprising:

[0368] a housing comprising a first inlet, a second inlet, and an outlet; and

[0369] an impeller capable of rotating within the housing about an axis of rotation to move fluid at an inlet to an outlet;

[0370] The first and second inlets are arranged on either side of a plane of rotation of the impeller, wherein the pump assembly further comprises a vortex generator in fluid communication with the inlets. The vortex generator may be configured to generate at least a first counter-rotating vortex and optionally a second counter-rotating vortex in the fluid moving into the first and second inlets, respectively. If there are two vortices, these vortices may be counter-rotating vortices.

[0371] Advantageously, generating counter-rotating vortices in the fluid moving into the first and second inlets of the pump may help to improve the efficiency of the pump by reducing the work required by the pump to induce the counter-rotating vortices in the fluid moving from the inlet to the outlet.

[0372] The vortex generator may include first and second vortex chambers configured to generate first and second vortexes, respectively. The vortex generator may include an inlet in fluid communication with the vortex chambers. The vortex generator may be configured such that fluid travels from the inlet to the first and second inlets of the pump via the first and second vortex chambers, respectively.

[0373] Advantageously, this configuration of the vortex generator enables the generation of the first vortex and the second vortex from a single fluid flow received at the inlet.

[0374] The vortex generator may be configured such that the first vortex chamber and the second vortex chamber receive a circumferential inlet flow from the inlet.

[0375] Advantageously, this configuration of the vortex generator may enable the vortex chamber to generate the first vortex and the second vortex without requiring any moving parts.

[0376] The vortex generator may include a first outlet and a second outlet fluidly connecting the respective first and second vortex chambers to the respective first and second inlets of the pump. The vortex generator may be configured such that the first and second vortex flows travel through the first and second outlets, respectively.

[0377] Advantageously, the first outlet and the second outlet may enable the first vortex and the second vortex to separate before entering the respective inlets of the pump.

[0378] The outlet may be substantially orthogonal to the direction of the circumferential inlet flow.

[0379] Advantageously, this configuration of the outlets may help to maximise the intensity of the first and second vortices flowing into respective inlets of the pump.

[0380] Each of the first vortex chamber and the second vortex chamber may be substantially bowl-shaped.

[0381] Advantageously, this configuration of the vortex chamber may help maximize the intensity of the first and second vortexes generated therein.

[0382] The vortex generator may include a wall common to the first and second vortex chambers, the wall being shaped to separate a fluid flowing from the inlet toward the wall into two counter-rotating vortices corresponding to the first and second vortexes.

[0383] Advantageously, this configuration of the vortex generator may enable the vortex chamber to generate the first vortex and the second vortex without requiring any moving parts.

[0384] The wall may include two arcuate portions joined via a ridge portion. An apex of the ridge portion may divide the first vortex chamber and the second vortex chamber.

[0385] The first inlet and the second inlet may be adjacent to each other.

[0386] Advantageously, this configuration of the pump may help to minimize the size of the vortex generators.

[0387] The vortex generators may be mounted to the housing of the pump.

[0388] Advantageously, mounting the vortex generator to the pump enables pre-assembly of the pump assembly.

[0389] The impeller may be rotated via an electric motor.

[0390] Advantageously, rotating the impeller via an electric motor may facilitate precise control of the speed of the impeller.

[0391] According to a sixth aspect of the present teachings, there is provided a work machine comprising the engine according to the first aspect.

[0392] The work machine may be configured to generate a visual and / or audible warning to an operator of the work machine when the monitoring system provides an alert output.

[0393] Advantageously, this configuration of the engine may help prevent the concentration of gaseous fuel in the crankcase from rising above its lower flammability limit.

[0394] According to a seventh aspect of the present teachings, a cyclonic oil separator is provided. The cyclonic oil separator is configured to form a vortex in gas traveling between an inlet portion and an outlet portion thereof to reduce the concentration of oil therein, the cyclonic oil separator generating a pressure drop between the inlet portion and the outlet portion. The inlet portion may include a pressure extraction point for a pressure transducer, and the outlet portion may include a pressure extraction point for a pressure transducer, so that a pressure differential can be determined.

[0395] According to an eighth aspect of the present teachings, an internal combustion engine is provided that is capable of operating in a selected one of a first configuration according to the first aspect as a gaseous fuel (e.g., a hydrogen-powered engine) and a second configuration as a liquid fuel (e.g., a diesel or gasoline-powered engine). In the second configuration, instead of a pump for discharging exhaust gases, including ventilation gases and blow-by gases, from the crankcase, a fuel injection pump is mounted adjacent to the engine structure, in the space originally occupied by the pump for delivering exhaust gases.

[0396] By providing an internal combustion engine that can be configured for use with both gaseous and liquid fuels with space for a fuel injection pump required for liquid fuel, but with the fuel injection pump being redundant for gaseous fuel so that the space is instead used for a crankcase ventilation pump, parts inventory can be minimized, both engines can potentially be built on the same production line, and / or require the same mounting space on a work machine, thereby saving costs.

[0397] Apertures may be provided in the wall of the gearbox for connecting a conduit to a pump for conveying exhaust gas in a first configuration and for driving from the gearbox to a fuel injection pump in a second configuration.

[0398] Providing the orifice in a single location useful in both configurations may further simplify the construction of the engine.

[0399] According to a ninth aspect of the present teachings, an oil pre-separator for installation within an oil and gas containing chamber of an internal combustion engine is provided. The pre-separator may include an extraction conduit defining a mouth for extracting gas from the chamber through a wall of the chamber, and a plate axially spaced from and covering the mouth.

[0400] The use of a pre-separator minimizes the amount of oil that flows downstream and potentially exits with the exhaust gases.

[0401] The plate may include an angled portion arranged to extend from an axially spaced position and terminate at an edge that is at least axially aligned with or axially overlaps the mouth.The edge may be laterally spaced from the mouth.

[0402] This arrangement has been found to be particularly effective in separating oil from gas.

[0403] The plate may include a flat portion covering the mouth. The angled portion may extend around the periphery of the flat portion.

[0404] The mouth may terminate in outward-turned lips.

[0405] This further enhances the separation of oil from the exhaust gases.

[0406] The pre-separator may comprise a flow diverter extending around at least a portion of the extraction conduit to divert oil flowing down the wall of the chamber away from the mouth of the extraction conduit.

[0407] This further enhances the separation of oil from the exhaust gases.

[0408] The ratio between the diameter or minimum width of the plate and the diameter of the extraction conduit may be between about 4:1 and 2.5:1, for example about 3:1.

[0409] This arrangement has been found to be effective in separating oil from the exhaust gas.

[0410] The angled portion of the plate may terminate approximately 5-6 mm axially from an adjacent wall (eg, a wall of the diverter).

[0411] The outwardly turned lip may be spaced further apart from the corresponding wall than the angled portion, for example at least 8 mm.

[0412] The outwardly turned lip may project laterally by at least 2 mm, for example about 4 mm.

[0413] According to a tenth aspect of the present teachings, there is provided an oil pre-separator for installation in an oil and gas containing chamber of a hydrogen powered internal combustion engine. The pre-separator comprises an extraction conduit defining a mouth for extracting exhaust gas from the chamber and a baffle arrangement.

[0414] The pre-separator may be configured to reduce the oil concentration in the exhaust gas by at least 2.5 times, preferably at least 4 times, at a flow rate of at least 30 l / min per litre of displacement of the internal combustion engine, for example at a flow rate of 30 l / min-80 l / min.

[0415] According to an eleventh aspect of the present teachings, an oil separation system for installation in an exhaust gas outflow path of a crankcase ventilation system of a hydrogen internal combustion engine is provided. The oil separation system comprises an oil pre-separator according to the ninth aspect and a cyclonic oil separator located downstream of the pre-separator.

[0416] The pre-separator and separator may reduce oil carryover in the exhaust gas flow path downstream of the separator to less than or equal to 1 g / hr of engine operation, optionally less than or equal to 0.5 g / hr of engine operation.

[0417] According to a twelfth aspect of the present teachings, a cyclonic oil separator for a crankcase ventilation system configured to remove blowby gases contained therein from a crankcase is provided. The separator receives exhaust gases including the blowby gases and is configured to cause a flow of exhaust gases therethrough to form a vortex, through which oil carried by the exhaust gases is separated from the exhaust gases. The oil separator may include a chamber having a truncated cone portion, wherein the truncated cone portion defines a longitudinal axis of the truncated cone portion. The maximum inner diameter of the truncated cone portion may be in the range of 30 mm to 80 mm.

[0418] Advantageously, to reduce the concentration of oil in the exhaust gas to be supplied, a cyclonic oil separator is used, and since the oil separator is a passive component, the complexity of the system is reduced and the need for an external power supply is avoided. Cyclonic oil separators are particularly effective when used in gaseous fuel engines, due to the higher gas flow rates of gaseous fuel engines compared to, for example, diesel engines.

[0419] In an exemplary embodiment, the frustoconical portion includes an apex and a cap distal to the apex, wherein the cap defines a cap plane. The cyclonic oil separator includes a separator inlet through which exhaust gas is introduced into the chamber, the inlet defining an inlet longitudinal axis. The inlet longitudinal axis is oriented at a non-zero angle to the cap plane, and wherein the inlet longitudinal axis is oriented toward the apex such that a flow of gas through the inlet is directed toward the apex.

[0420] It has been found that orienting the inlet of the cyclonic oil separator towards the apex of the separator advantageously improves the flow of exhaust gas through the separator.

[0421] In an exemplary embodiment, the inlet longitudinal axis of the cyclonic oil separator is oriented at an angle of between 1° and 45° to the plane.

[0422] In an exemplary embodiment, the inlet longitudinal axis is oriented at an angle of between 10° and 35° to the plane.

[0423] It has been found that orienting the inlet at an angle within these ranges advantageously results in improved turbulence and, therefore, improved separation of the oil from the exhaust gases.

[0424] In an exemplary embodiment, the cyclonic oil separator includes a gas outlet through which exhaust gas exits the chamber downstream of the vortex.

[0425] In an exemplary embodiment, the cyclonic oil separator of the chamber includes a cylindrical portion adjoining the frustoconical portion and defining a cylindrical portion longitudinal axis, wherein the cylindrical portion is distal to the apex. The gas outlet includes a tube extending within the chamber.

[0426] In an exemplary embodiment, the tube defines a tube longitudinal axis, and the tube longitudinal axis is at an angle of 10° or less to the cylindrical portion longitudinal axis.

[0427] In an exemplary embodiment, the tube longitudinal axis makes an angle of 5° or less with the cylindrical portion longitudinal axis.

[0428] In an exemplary embodiment, the tube longitudinal axis is substantially parallel to the cylindrical portion longitudinal axis.

[0429] In an exemplary embodiment, the tube longitudinal axis is coaxial with the cylindrical portion longitudinal axis.

[0430] In an exemplary embodiment, the tube is a substantially cylindrical tube.

[0431] In an exemplary embodiment, the tube outer diameter is in the range of 17 mm to 45 mm.

[0432] A tube of this shape and size improves the flow of exhaust gas through the chamber and assists the exit of exhaust gas from the chamber. In particular, the corresponding shape of the outside of the tube and the inside of the cylindrical portion of the chamber improves vortex flow.

[0433] In an exemplary embodiment, the tube extends within the chamber for between one quarter and one third of the length of the cylindrical portion.

[0434] In an exemplary embodiment, the tube extends within the chamber for between one quarter and one third of the length of the chamber.

[0435] Advantageously, this relative length of the tube facilitates the exit of exhaust gas from the cyclonic oil separator.

[0436] In an exemplary embodiment, the gas outlet of the cyclonic oil separator includes an outlet orifice defined by the chamber, and the outlet orifice is located at an upper end of the chamber, distal from the apex.

[0437] This location of the outlet orifice advantageously assists the exit of exhaust gases from the chamber.

[0438] In an exemplary embodiment, the height of any one separator truncated cone portion of the cyclonic oil separator is in the range of 50 mm to 200 mm.

[0439] It has been found that the cyclonic oil separator is effective while being relatively compact, as indicated by the above dimensions. Thus, the cyclonic oil separator can be advantageously installed in a compact space while providing effective and useful separation of oil from the exhaust gas.

[0440] In an exemplary embodiment, the truncated cone portion of the cyclonic oil separator is a true circular truncated cone portion.

[0441] In an exemplary embodiment, the truncated cone portion is an inclined circular truncated cone portion.

[0442] It has been found that either conical shape provides effective vortex flow.The shape of the truncated cone portion can be adjusted to suit the available space.

[0443] In an exemplary embodiment, any one chamber of the cyclonic oil separator includes a cylindrical portion adjoining a truncated conical portion and defining a cylindrical portion longitudinal axis, wherein the truncated conical portion is defined by a wall, and wherein an angle of the wall to the cylindrical portion longitudinal axis is in the range of 0° to 30°.

[0444] In an exemplary embodiment, the maximum angle of the wall with the longitudinal axis of the cylindrical portion is in the range of 15° to 30°, and the minimum angle of the wall with the longitudinal axis of the cylindrical portion is in the range of 0° to 25°.

[0445] In an exemplary embodiment, the frustoconical portion longitudinal axis makes an angle of 0° to 30° with the cylindrical portion longitudinal axis.

[0446] Such dimensions have been found to provide an effective separator whilst allowing the separator to be fitted into the relatively small space required.

[0447] In an exemplary embodiment, the cyclonic oil separator includes an oil outlet, and the oil outlet is located at the apex.

[0448] In an exemplary embodiment, the oil outlet defines an oil outlet longitudinal axis, and the oil outlet longitudinal axis makes an angle of 0° to 45° with the frusto-conical portion longitudinal axis.

[0449] This position and angle of the oil outlet allows the oil to leave the separator by gravity and thus return to the sump for reuse. The angle of the oil outlet and the angle of the frustum allow the separator to fit into the required space while remaining effective.

[0450] In an exemplary embodiment, a cyclonic oil separator of a separator includes a first molded portion and a second molded portion.

[0451] Advantageously, the oil separator can be molded into the desired shape and size and is easy to assemble.

[0452] In an exemplary embodiment, the separator is made of a plastic material.

[0453] Plastic materials are easily molded into desired shapes.

[0454] In an exemplary embodiment, the separator is made of a composite material of plastic material and conductive material.

[0455] Advantageously, such composite materials allow for insulation of components while still providing electrical conductivity to avoid static differences between components connected to the oil separator.

[0456] In an exemplary embodiment, a reduction in oil concentration of at least a factor of 10 is achieved at a flow rate of exhaust gas through the oil separator of at least 30 1 / min per liter of engine displacement.

[0457] In an exemplary embodiment, a reduction in oil concentration of at least a factor of 10 is achieved at a flow rate of exhaust gas through the oil separator of at least 60 1 / min per liter of engine displacement.

[0458] In an exemplary embodiment, a reduction in oil concentration of at least 20 times is achieved at a flow rate of exhaust gas through the oil separator of at least 30 1 / min per liter of engine displacement.

[0459] In an exemplary embodiment, a reduction in oil concentration of at least 20 times is achieved at a flow rate of exhaust gas through the oil separator of at least 60 1 / min per liter of engine displacement.

[0460] The flow rate may be in the range of 30 l / min to 80 l / min per litre of engine displacement, at which flow rate a reduction in oil concentration of at least a factor of 10, optionally at least a factor of 20, is achieved.

[0461] Such flow rates per litre of engine displacement are typical for engines of the type described herein.

[0462] At an exhaust gas flow rate through the separator of at least 130 l / min; optionally at a flow rate of 260 l / min, a reduction in oil concentration of at least 10 times can be achieved; optionally at least a reduction in oil concentration of 20 times can be achieved.

[0463] According to a thirteenth aspect of the present teachings, there is provided a conductivity monitoring system configured to monitor the conductivity of a ventilation system of an internal combustion engine according to the first aspect.

[0464] According to a fourteenth aspect of the present teachings, there is provided a gaseous fuel internal combustion engine comprising a pump assembly according to the fifth aspect.

[0465] The engine may comprise at least two of the pump assemblies according to the fifth aspect.

[0466] The axis of rotation of the impeller may be arranged to be substantially vertical in the normal operating orientation of the engine.

[0467] Advantageously, this orientation of the impeller may assist in draining oil from the pump.

[0468] The axis of rotation of the impeller may be substantially parallel to the axis of one or more cylinders of the engine.

[0469] It will be appreciated that features of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth and / or fourteenth aspects may be combined with features of other aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0470] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0471] Figure 1 shows an isometric view of an internal combustion engine according to an embodiment;

[0472] Figure 2 shows a simplified block diagram of an internal combustion engine crankcase ventilation system;

[0473] Figure 3 Shown is a diagram including an intake system Figure 1 Isometric view of an internal combustion engine;

[0474] Figure 4 Shown by Figure 1 A cross-sectional view of the internal combustion engine taken through section WW in FIG.

[0475] Figure 5 Shown by Figure 1 a cross-sectional view of the internal combustion engine taken at section XX in FIG.

[0476] Figure 6 Shown by Figure 1 a cross-sectional view of the internal combustion engine taken at section YY in FIG.

[0477] Figure 7 Shown by Figure 1 a cross-sectional view of the internal combustion engine taken at section ZZ in FIG.

[0478] Figure 8 shows exemplary graphs of set point flow versus engine speed for different engine load conditions;

[0479] Figure 9A and Figure 9B It is a flow chart of the control method of the ventilation system;

[0480] Figure 10Shown Figure 1 An isometric view of a crankcase ventilation system pump assembly of an internal combustion engine;

[0481] Figure 11 Shown Figure 10 An isometric view of a vortex generator of a pump assembly;

[0482] Figure 12 Shown Figure 11 A cross-sectional view of a vortex generator shown in ;

[0483] Figure 13 Shown Figure 1 Isometric view of an oil pre-separator for an internal combustion engine;

[0484] Figure 14 yes Figure 13 A side view of an oil pre-separator;

[0485] Figure 15 yes Figure 13 A cross-sectional view of an oil pre-separator;

[0486] Figure 16 yes Figure 1 An internal view of a gearbox of an internal combustion engine;

[0487] Figure 17 The pump assembly and oil pre-separator are installed in Figure 1 Detailed view of an internal combustion engine;

[0488] Figure 18 yes Figure 1 A side view of an oil separator of an internal combustion engine;

[0489] Figure 19 yes Figure 18 A cross-sectional view of an oil separator;

[0490] Figure 20 yes Figure 18 The oil separator is in Figure 19 another cross-sectional view in the opposite direction;

[0491] Figure 21 yes Figure 18 A plan view of the oil separator; and

[0492] Figure 22 is included Figure 1 a side view of an exemplary work machine equipped with an internal combustion engine;

[0493] Figure 23 is a perspective view of an internal combustion engine according to another embodiment;

[0494] Figure 24 Shown Figure 23 A block diagram of the crankcase ventilation system of an internal combustion engine, which is similar to Figure 2 ,but;

[0495] Figure 25 yes Figure 23 A perspective view of a crankcase ventilation system pump assembly of an internal combustion engine; and

[0496] Figures 26 to 28 Passing through different planes Figure 24 Vertical cross-sectional view of the oil separator of the crankcase ventilation system. DETAILED DESCRIPTION

[0497] In the following detailed description, numerous specific details are set forth to provide a thorough understanding of various embodiments and inventive concepts. However, those skilled in the art will appreciate that the present teachings may be practiced without these specific details or with known equivalents thereof; that the present teachings are not limited to the described embodiments; and that the present teachings may be practiced in various alternative embodiments. It should also be appreciated that well-known methods, processes, components, and systems may not be described in detail.

[0498] Figure 1 An internal combustion engine 100 is shown according to an embodiment. The engine 100 is a gaseous fuel engine configured to be powered by a gaseous fuel, such as hydrogen, compressed natural gas (CNG), biogas, etc. In the embodiment shown, the engine 100 is powered by hydrogen.

[0499] The engine 100 may be suitably used in a work machine 10 (see Figure 22 , which depicts a backhoe loader, but could also be the prime mover of, for example, a telescopic handler, forklift, wheel loader shovel, dump truck, excavator, or tractor. Such work machines 10 are suitable for use in off-highway industries such as agriculture and construction. In these industries, they are typically configured to perform tasks such as digging, load handling, harvesting, or planting crops. The engine 100 may also be used in a generator set (genset), which is a self-sufficient unit that provides electrical power in an off-grid location. Therefore, the engine 100 is typically required to have certain characteristics, such as high torque output over a wide range of engine speeds, with peak torque occurring at relatively low engine speeds, unlike, for example, a light passenger car. In off-highway applications, this provides a "torque reserve" that enables the work machine 10 to continue performing work operations when encountering increased loads or resistance to work operations (e.g., an excavator encountering a particularly solid patch of dirt to be excavated).

[0500] The engine 100 includes an engine structure 102 including a crankcase 104 , a cylinder head 106 , a rocker cover 107 , a cylinder block 108 , and a gearbox 109 .

[0501] The cylinder block 108 includes one or more cylinders 112; in this embodiment, four (see Figure 6 ). Cylinder head 106 is mounted to cylinder block 108 to couple to one or more cylinders 112. Cylinder head 106 includes one or more intake ports (not shown) for supplying air to each cylinder 112, and one or more exhaust ports (not shown) for exhausting combustion gases from each cylinder 112. In embodiments where engine 100 is a port fuel injection engine, one or more intake ports also receive fuel from pressurized fuel tank 12 ( Figure 22 ) supplies fuel to each cylinder 112. Each intake port is selectively opened and closed by an intake valve (not shown), and each exhaust port is selectively opened and closed by an exhaust valve (not shown). In other embodiments, gaseous fuel can be directly injected into each cylinder 112.

[0502] Engine 100 includes a valvetrain (not shown) comprising a camshaft (not shown) and rocker arms (not shown) arranged to open and close each intake valve and each exhaust valve via rotation of the camshaft (not shown). The camshaft is mounted to cylinder block 108. The rocker arms are mounted to cylinder head 106. The movement of the camshaft is transmitted to the rocker arms via push rods (not shown) extending between cylinder block 108 and cylinder head 106. Rocker covers 107 are mounted to cylinder head 106 and house the rocker arms.

[0503] Each cylinder 112 receives a piston 113 (at Figure 2 1 ), the pistons 113 are capable of translational movement within cylinders 112. During operation of the engine 100, the translational movement of each piston 113 is converted into rotational movement of a crankshaft (not shown). The crankcase 104 houses the crankshaft.

[0504] In this embodiment, the total displacement of the engine is 4.4 liters (i.e., 1.1 liters per cylinder). In engines used in off-highway applications, each cylinder may typically have a displacement between 0.75 liters and 1.5 liters. This displacement is relatively high compared to passenger car engines, but is suitable for providing the above-mentioned operating characteristics.

[0505] The gearbox 109 is mounted to one or both of the cylinder block 108 and the crankcase 104. The gearbox 109 projects laterally from one or both of the cylinder block 108 and the crankcase 104. The gearbox 109 houses the gear assembly 339 (in Figure 16 ), the gear assembly is configured to transfer the rotational motion of the crankshaft to the camshaft for operation of the rocker arms. Gearbox 109 is in fluid communication with crankcase 104 and, for purposes of this description, may be considered an extension of the crankcase.

[0506] Further references Figure 2 and Figure 3 The engine 100 includes an intake system 115 configured to supply air to one or more cylinders 112 for combustion. In the illustrated embodiment, the intake system 115 is configured to supply air to the cylinder head 106 for delivery to the cylinders 112 via corresponding intake ports.

[0507] Further references Figure 3 The intake system 115 includes an intake passage 140 (composed of Figure 2 ), the intake passage is arranged to deliver air from the upstream air filter 118 to the downstream cylinder 112.

[0508] During operation of engine 100 , gaseous fuel and air introduced into each cylinder 112 and combustion gases formed within cylinder 112 flow as “blow-by gases” from the combustion chamber along a path indicated by arrow 105 , past piston 113 , and into crankcase 104 .

[0509] The engine 100 includes a ventilation system 110 configured to vent blow-by gases from the crankcase 104 .

[0510] Figure 2 A simplified diagram of a ventilation system 110 according to an embodiment is shown. The ventilation system 110 includes a ventilation path 116 (at Figure 2 1 (indicated by a dashed line in FIG) to deliver ventilation gas (in this embodiment, air) from the intake system 115 to the crankcase 104 from the ventilation path inlet to dilute the concentration of blowby gas in the crankcase 104. This portion of the ventilation path 116 located upstream of the crankcase 104 is referred to as an inflow portion 125. The term "ventilation gas" is used to distinguish it from air supplied to one or more cylinders 112 for combustion.

[0511] The ventilation system 110 is configured to define a first location 140a of the ventilation path inlet (see Figure 2 and Figure 3 ) draws air from the intake passage 140 into the ventilation path 116 as ventilation gas.

[0512] The ventilation system 110 is further configured to convey diluted blowby gases (hereinafter referred to as "exhaust gases") from the crankcase 104 to an outlet via a ventilation path 116. The portion of the ventilation path 116 downstream of the crankcase 104 and the gearbox 109 is referred to as an outflow portion 126.

[0513] The ventilation system 110 is configured to exhaust exhaust gas from the crankcase 104 to a second location 140b of the intake passage 140 that defines a ventilation path outlet. The second location 140b is located downstream from the first location 140a relative to the intake passage 140.

[0514] The ventilation system 110 also includes a gas pressure source 114 located within the ventilation path 116. The gas pressure source 114 is configured to deliver ventilation gas from a first location 140a to the rocker cover 107 and then to the crankcase 104 along an inflow portion 125 of the ventilation path 116. The gas pressure source 114 is further configured to deliver a combination of the ventilation gas and blowby gases 105 (which include gaseous fuel) as exhaust gas from the crankcase 104 and the gearbox 109 and along an outflow portion 126 of the ventilation path 116 to a segment location 140b.

[0515] It will be appreciated that the flow rate of exhaust gas exhausted from the crankcase 104 in the outflow portion 126 of the ventilation path 116 is substantially equal to the sum of the flow rate of blowby gas entering the crankcase past the piston 113 as indicated by arrow 105 and the flow rate of ventilation gas entering the crankcase 104 via the inflow portion 125 .

[0516] Advantageously, routing ventilation gases from the first location 140 a to the crankcase 104 via the rocker cover 107 and the cylinder head 106 helps flush the blowby gases out and away from the cylinder head 106. Thus, exposure of components in the cylinder head 106 (e.g., rocker arms) to the blowby gases is reduced, which can reduce damage to such components due to exposure to blowby gases containing hydrogen (e.g., via hydrogen embrittlement).

[0517] In the illustrated embodiment, the gas pressure source 114 is a pump 114 or a blower. In alternative embodiments (not shown), any suitable gas pressure source may be used. For example, in some embodiments, the gas pressure source 114 may be provided by a compressor or turbine (e.g., a compressor or turbine stage of a turbocharger) in the intake system 115 / exhaust system, which is in fluid communication with the ventilation system 110.

[0518] The pump 114 is configured to induce a subatmospheric pressure in the crankcase 104 within a range of -100 mbar to -10 mbar relative to atmospheric pressure; for example, a subatmospheric pressure within a range of -80 mbar to -20 mbar relative to atmospheric pressure. In the illustrated embodiment, the pump 114 is disposed downstream of the crankcase 104 in an outflow portion 126 of the ventilation path 116.

[0519] In alternative embodiments (not shown), the pump 114 may be configured to induce any suitable subatmospheric pressure in the crankcase 104. In other embodiments, the pump 114 may be configured to induce a superatmospheric pressure in the crankcase 104. For example, the pump 114 may be positioned upstream of the crankcase 104 in the inflow portion 125 of the ventilation path 116.

[0520] The ventilation system 110 includes an oil separator 130 that is configured to reduce the concentration of oil in the exhaust gases delivered from the crankcase 104. The oil separator 130 is a passive oil separator. A "passive oil separator" is defined as an oil separator that does not require an external power source to reduce the concentration of oil in the exhaust gases flowing through the oil separator. In the illustrated embodiment, the oil separator 130 is a cyclonic oil separator, which will be discussed further below. In alternative embodiments (not shown), the oil separator 130 can be any suitable active or passive oil separator. For example, the oil separator 130 can be a labyrinth oil separator, similar to the one described below with respect to Figure 26 and Figure 27 The oil separator 130 is located in the outflow portion 126 .

[0521] The oil separator 130 is arranged downstream of the pump 114. In the illustrated embodiment, the oil separator 130 is mounted to the pump 114.

[0522] The engine 100 includes an oil passage 129 (at Figure 2 (Indicated by a dashed line in FIG), this oil passage is arranged to deliver oil removed from the exhaust gas by oil separator 130 to crankcase 104. The removed oil drains toward crankcase 104 along oil passage 129 due to gravity. The pressure in crankcase 104 is lower than the pressure downstream of pump 114. Therefore, this pressure differential helps to draw the removed oil from oil separator 130 along oil passage 129 to crankcase 104.

[0523] The ventilation system 110 also includes an oil pre-separator 128 located upstream of the pump 114. The oil pre-separator 128 is configured to reduce the concentration of oil in the exhaust gas delivered from the crankcase 104 to the pump 114. The oil pre-separator 128 is a passive oil pre-separator. In the illustrated embodiment, the oil pre-separator 128 includes one or more baffles, as will be discussed in more detail below. In alternative embodiments (not shown), the oil pre-separator 128 can be any suitable active or passive oil separator. The oil pre-separator 128 is located in the outflow portion 126, specifically, in this embodiment, at the beginning of the outflow portion, i.e., where the outflow portion meets the crankcase 104 / gearbox 109.

[0524] In the illustrated embodiment, the ventilation system 110 is configured to deliver exhaust gas to the intake system 115 for supply to one or more cylinders 112 via outflow portion 126. Thus, the ventilation system 110 can be considered a closed-loop system. In the illustrated embodiment, exhaust gas is delivered from the crankcase 104 to the intake system 115 via outflow portion 126.

[0525] In an alternative embodiment (not shown), ventilation system 110 may not be configured to deliver exhaust gas to intake system 115. In such an embodiment, ventilation system 110 may be configured to exhaust exhaust gas to atmosphere (e.g., downstream of pump 114) and may be considered an open-loop system.

[0526] In an alternative embodiment (not shown), the ventilation system 110 is configured to draw any suitable gas (eg, exhaust gas from combustion in one or more cylinders 112 ) into the ventilation path 116 .

[0527] The intake passage 140 is configured to supply air for combustion to the cylinder 112 via the cylinder head 106. The intake passage 140 in the cylinder head 106 is separated from the ventilation path 116 in the cylinder head 106 and is sealed from each other.

[0528] The intake system 115 includes a compressor 142 along an intake passage 140. A first location 140a is located upstream of the compressor 142. A second location 140b is located upstream of the compressor 142. The compressor 142 may be a turbocharger, a supercharger, or any device suitable for compressing engine intake air.

[0529] Pump 114 is configured to generate a lower pressure in crankcase 104 relative to the pressure at inlet 144 of compressor 142, which may contribute to reduced fuel consumption and reduced emissions. In the illustrated embodiment, compressor 142 generates a pressure at inlet 144 of -60 to 0 mbar relative to atmospheric pressure.

[0530] As will be discussed in greater detail below, ventilation path 116 passes through rocker cover 107 to reach cylinder head 106. Outflow portion 126 also passes through rocker cover 107. First location 140a and second location 140b of intake passage 140 are positioned adjacent to rocker cover 107. This reduces the length of conduits 146a, 146b used to fluidly connect first location 140a and second location 140b to rocker cover 107. Advantageously, this helps minimize the exposed portion of ventilation path 116 and outflow portion 126 (i.e., the portion thereof located outside of engine structure 102). In alternative embodiments (not shown), one or both of first location 140a and second location 140b may not be positioned adjacent to rocker cover 107.

[0531] The outflow portion 126 terminates above the cylinders 112. As used herein, the term "above" is intended to include any location above any horizontal plane located at the top of the cylinders 112. In the illustrated embodiment, the outflow portion 126 terminates at a second location 140b of the intake passage 140. Advantageously, terminating the outflow portion 126 above one or more cylinders 112 can help ensure that, during use, at least a section of the outflow portion 126 is heated by combustion within the one or more cylinders 112, thereby helping to prevent exhaust gases from freezing in the outflow portion 126.

[0532] In the following, reference will be made to Figures 4 to 7 Describing the ventilation path 116 in further detail, Figures 4 to 7 are respectively along Figure 1 The views are taken at sections WW, XX, YY and ZZ shown in FIG.

[0533] like Figure 4 As shown, rocker cover 107 includes a rocker cover inlet 119 located in ventilation path 116. Pump 114 is configured to deliver ventilation gas from a first location 140a to rocker cover inlet 119 and then to cylinder head 106. Conduit 146a fluidly connects rocker cover inlet 119 with first location 140a of intake passage 140.

[0534] The rocker cover 107 includes a baffle 121 that is configured to disperse the flow of ventilation gas delivered along the ventilation path 116 substantially across the cylinder head 106. As will be discussed below, this helps distribute the ventilation gas to the gas flow passages in the cylinder head 106, as well as helps inhibit the ventilation gas from interfering with lubrication of valvetrain components housed in the rocker cover 107, such as the rocker arms.

[0535] In the illustrated embodiment, the baffle 121 is disposed adjacent the rocker cover inlet 119. The baffle 121 is substantially perpendicular to the longitudinal axis of the rocker cover inlet 119. In alternative embodiments (not shown), the baffle 121 may have any suitable configuration.

[0536] In the illustrated embodiment, the rocker cover 107 includes a single rocker cover inlet 119 located in the ventilation path 116. In an alternative embodiment (not shown), the rocker cover 107 may include more than one rocker cover inlet 119 located in the ventilation path 116.

[0537] The ventilation path 116 includes one or more gas flow passages 120 located in the engine structure 102 for delivering ventilation gas from the cylinder head 106 to the crankcase 104. In the illustrated embodiment, the ventilation path 116 includes a plurality of gas flow passages 120 distributed across and along the crankcase 104. "Distributed across and along the crankcase" is intended to mean that the outlets of the gas flow passages 120 in the crankcase 104 are distributed within the crankcase 104 in any suitable configuration.

[0538] In the illustrated embodiment, the gas flow passage 120 includes a plurality of oil drain passages for draining oil from the cylinder head 106 to the crankcase 104. During operation of the engine 100, oil sprayed onto components of the valve train housed in the rocker cover 107 (e.g., rocker arms) for lubrication is delivered via the oil drain passages 120 to an oil sump 122 disposed in or below the crankcase 104. Figure 4 Only one oil drain passage 120 is shown in FIG, but the engine 100 includes a plurality of oil drain passages 120 distributed across the crankcase 104.

[0539] In the illustrated embodiment, the gas flow passage 120 includes all of the oil drain passages in the cylinder head 106. In an alternative embodiment (not shown), the gas flow passage 120 may include only one or more of the oil drain passages in the cylinder head 106. In some embodiments, the gas flow passage 120 may additionally or alternatively include one or more pushrod passages (not shown), each of which is arranged to receive one of the pushrods of the valve train. Each pushrod passage may extend through the cylinder block 108 and the cylinder head 106 and be in fluid communication with the crankcase 104.

[0540] like Figure 4 As shown, an oil drain passage 120 extends from the rocker cover 107 through the cylinder head 106, the cylinder block 108, and the crankcase 104 to the oil sump 122. The gas flow passage 120 includes the oil drain passage 120 of the cylinder block 108 downstream of the cylinder head 106 and upstream of the crankcase 104.

[0541] The oil drain passages 120 may form an oil drain passage network including one or more inlets in the cylinder head 106 and one or more outlets in the crankcase 104. The number of inlets in the cylinder head 106 may be greater, less than, or equal to the number of outlets in the crankcase 104.

[0542] Advantageously, routing ventilation gases from the cylinder head 106 to the crankcase 104 via the oil drain passages 120 helps flush blowby gases from the increased volume of the engine structure 102. Utilizing all of the oil drain passages 120 provides a more uniform airflow and pressure distribution for flushing crankcase gases and also reduces the chance of hydrogen, which has a lower density than air, rising into the rocker cover or elsewhere. Furthermore, using the oil drain passages eliminates the need for providing a separate, dedicated gas flow path for ventilation gases between the cylinder head 106 and the crankcase 104, instead utilizing pre-existing paths within the engine structure 102.

[0543] refer to Figures 5 to 7 , a portion of the outflow portion 126 is disposed in the engine structure 102. The outflow portion 126 passes through one or more of the gearbox 109, the cylinder block 108, the cylinder head 106, and the rocker cover 107.

[0544] As described below, in the illustrated embodiment, the outflow portion 126 passes through the gearbox 109 , the cylinder block 108 , the cylinder head 106 , and the rocker cover 107 in series.

[0545] Figure 5 The general flow direction of ventilation gases and blow-by gases through the crankcase 104 and the gearbox 109 is shown. The blow-by gases and ventilation gases mix and flow along the Figure 5 The direction indicated by the dashed arrow in FIG. 1 is toward the outlet oil pre-separator 128 .

[0546] An oil pre-separator 128 is located upstream of the pump 114 at the upstream end of the outflow portion 126. In the illustrated embodiment, the oil pre-separator 128 is mounted to the gearbox 109, as described in more detail below.

[0547] Further references Figure 16 Ventilation gases and blowby gases flowing through gearbox 109 to oil pre-separator 128 are exposed to gear assembly 339. During operation of engine 100, as the gears rotate, gear assembly 339 sprays oil throughout gearbox 109. Thus, as exhaust gases flow through gearbox 109, they entrain a portion of this oil. Oil pre-separator 128 advantageously reduces the oil content of the exhaust gas before it flows downstream to pump 114.

[0548] As will be discussed in greater detail below, the oil pre-separator 128 includes one or more baffles. The oil pre-separator 128 is configured such that the one or more baffles divert the flow of the exhaust gas in the outflow portion 126, thereby causing oil and other liquids (e.g., water produced as a byproduct of hydrogen combustion) entrained with the exhaust gas to settle in the oil pre-separator 128.

[0549] Figure 6A first section 126a of the outflow portion 126 is shown, arranged to deliver exhaust gas from the oil pre-separator 128 sequentially to the pump 114, the oil separator 130 and the gearbox inlet 133. In this embodiment, the first section 126a is located external to the engine structure 102.

[0550] Figure 6 Also shown is a second section 126b of the outflow portion 126, which is arranged to convey exhaust gas from the oil separator 130 through the gearbox 109 to the cylinder inlet 132. The second section 126b is sealed relative to the rest of the gearbox 109 so that exhaust gas in the second section 126b cannot mix with gas in the rest of the gearbox 109.

[0551] Figure 7 A third section 126c of the outflow portion 126 is shown, which is arranged to convey exhaust gas from the cylinder block inlet 132 through the cylinder block 108, the cylinder head 106 and the rocker cover 107 in sequence to the rocker cover outlet 134 in the rocker cover 107. A conduit 146b connects the rocker cover outlet 134 to a second location 140b of the intake passage 140 (see FIG. Figure 3 ) are fluidly connected.

[0552] The third section 126c passes through a passage 127 in the rocker cover 107. The passage 127 is formed between the rocker cover 107 and a plate 131 that is secured to the interior of the rocker cover 107 (e.g., via one or more fasteners, such as bolts). In the illustrated embodiment, the body of the rocker cover 107 is formed as a single, unitary piece of material (e.g., via a casting process). The passage 127 leads to a rocker cover outlet 134.

[0553] The second section 126b and the third section 126c of the outflow portion 126 that pass through the gearbox 109, the engine block 108, the cylinder head, and the rocker cover 107 are sealed from the rest of the engine structure 102. In this way, exhaust gas is prevented from flowing into the portion of the cylinder head 106 or the rocker cover 107 that is located outside the outflow portion 126.

[0554] The second section 126b and the third section 126c of the outflow portion 126 that pass through the gearbox 109, the engine block 108 and the cylinder head are primarily formed by a casting process, although some components may require machining operations after the casting process.

[0555] In alternative embodiments (not shown), outflow portion 126 may have any suitable configuration.

[0556] The flow rate of blowby gases, and therefore gaseous fuel, into the crankcase 104 depends on the operating state of the engine 100. For example, when the engine 100 is operating at a high torque output (load), the flow rate of blowby gases into the crankcase 104 is higher due to the larger volumes of air and gaseous fuel being injected into the cylinders 112 compared to relatively low torque (load).

[0557] Therefore, because the volume of blowby gases to be discharged from the crankcase 104 varies with the operating state of the engine 100, operating the pump 114 to provide a constant pump output would be inefficient, thereby resulting in unnecessary engine parasitic losses at least when the engine 100 is operating at low torque (load).

[0558] In this embodiment, the output of the pump 114 is controlled based on one or more determined operating parameters of the engine 100. This enables the flow of exhaust gas to be controlled so that the concentration of the gaseous fuel in the crankcase 104 is below its lower flammability limit throughout the operating range of the engine 100 while minimizing engine parasitic losses.

[0559] In this embodiment, the determined operating parameters are engine speed and engine torque (load).In other embodiments, the determined one or more operating parameters may include additional and / or alternative operating parameters of engine 100.

[0560] It has been found that engine speed and engine torque (load) provide a reliable representation of the blowby gas flow rate into the crankcase 104. Once this representation of the blowby gas flow rate is established, it can be used to determine the ventilation gas flow rate and / or exhaust gas flow rate (i.e., the sum of the blowby gas flow rate and the ventilation gas flow rate) required to dilute the blowby gases to below their lower flammability limit. The exhaust gas flow rate derived from the operating parameters is hereinafter referred to as the setpoint flow rate.

[0561] Figure 8 Three exemplary graphs 500, 502, 504 of exhaust gas setpoint flow versus engine speed for engine 100 for three different engine torque (load) conditions are shown. Such graphs may be generated via calibration testing of exemplary engine 100.

[0562] The first curve 500 corresponds to the maximum torque (load) condition of the engine 100, where the engine 100 outputs the maximum torque (load) at each engine speed. Figure 8 As shown, the maximum set point flow for the maximum torque (load) condition is at an engine speed of approximately 1150 RPM-1200 RPM, which corresponds to the overall maximum output torque of the engine 100 in this embodiment.

[0563] The second curve 502 corresponds to a 50% maximum torque (load) condition of the engine 100, wherein the engine 100 outputs half of the maximum torque (load) at each engine speed. The third curve 504 corresponds to a parasitic load condition, wherein the engine 100 outputs the minimum load required to power the engine's auxiliary devices at each engine speed.

[0564] refer to Figure 2 The ventilation system 110 includes a controller 150 configured to control the output of the pump 114 based on one or more determined operating parameters of the engine 100. The controller 150 may form part of an engine control unit (ECU) of the engine 100 or may be a standalone controller.

[0565] The controller 150 may include any suitable circuitry to implement control of the pump 114 and follow the control methods described herein. The controller may include: control circuitry; and / or processor circuitry; and / or at least one application-specific integrated circuit (ASIC); and / or at least one field-programmable gate array (FPGA); and / or a single or multi-processor architecture; and / or a sequential / parallel architecture; and / or at least one programmable logic controller (PLC); and / or at least one microprocessor; and / or at least one microcontroller; and / or a central processing unit (CPU) to perform the described methods. The controller 150 may include associated memory, or the memory may be located locally or remotely from the controller. The memory may be non-volatile flash memory.

[0566] In this embodiment, the controller 150 is configured to control the pump 114 based on the determined one or more operating parameters via a lookup table or map stored in memory. The lookup table contains Figure 8 The controller 150 may be configured to interpolate to obtain set point flows for intermediate values ​​of engine load and engine speed.

[0567] In the case where the determined operating parameters are engine speed and engine torque, these operating parameters may be determined or obtained by an engine ECU for operating the engine 100 and transmitted via signal line 152 (e.g., as Figure 2 The CAN bus shown) is supplied to the controller 150.

[0568] In an alternative embodiment (not shown), controller 150 may be configured to control pump 114 via any suitable means, such as, for example, via a physics-based model of engine 100 .

[0569] In the illustrated embodiment, the pump 114 is a variable speed pump driven in a fixed relationship by an electric motor (e.g., a variable speed DC electric motor). The controller 150 is configured to control the speed of the electric motor, and therefore the speed of the pump 114, based on one or more determined operating parameters. For example, in embodiments where the pump 114 includes a rotating element (such as an impeller) for pumping fluid, the controller 150 can be configured to control the rotational speed of the rotating element by providing an appropriate control signal to the electric motor based on the impeller speed required to achieve a specific set point flow rate and the gear ratio (if any) between the electric motor and the impeller.

[0570] In alternative embodiments (not shown), the controller 150 may be configured to additionally or alternatively control the output of the pump 114 by a mechanism other than by adjusting the pump speed. For example, the controller 150 may be configured to control the position of one or more rotating blades or paddles within the pump 114, or the position of an output valve of the pump 114. In such embodiments, the pump 114 may not be a variable speed pump.

[0571] refer to Figure 9A , which describes one embodiment of a ventilation control method. In this embodiment, the controller 150 monitors engine torque (load) and engine speed at step S510 and consults a lookup table at step S512 to determine a setpoint pump speed based on the torque and speed values ​​of the engine 100 (and the resulting setpoint flow rate). The controller 150 then signals the electric motor to operate the pump 114 at the setpoint speed (e.g., via a pulse width modulated signal) at step S514.

[0572] In this embodiment, the electric motor is of a type that provides feedback of its actual speed to the controller 150, for example, via the use of a position encoder, a Hall effect sensor, or by monitoring back EMF (back electromotive force). This enables the controller 150 to check the set point pump speed being achieved at step S516. If the speed error is zero (or within a suitable range), the process returns to monitoring the engine speed and load at step S510. If the speed error is not zero (or not within a suitable range), the controller 150 determines at step S518 that a correction is required for the signal and adjusts the signal sent to the electric motor accordingly at step S520. The controller 150 may determine the correction using any suitable control logic. For example, the controller 150 may determine the correction using Proportional-Integral-Derivative (PID) control.

[0573] Thus, in this embodiment, the controller 150 controls the speed of the pump 114 in a closed loop. However, in this embodiment, the control of the flow rate of the exhaust gas is open loop because other factors such as restrictions in the ventilation path 116 may affect the flow rate and are not considered in this embodiment.

[0574] Calibration using the representative ventilation system 110 may be required to correlate the pump speed to a set point flow rate of exhaust gas to ensure that the concentration of gaseous fuel in the crankcase 104 is below its lower flammability limit.

[0575] A maximum set-point pump speed is generally desired when one or more determined operating parameters correspond to a maximum output torque (load) of the engine 100 and / or a speed of the engine 100 .

[0576] It has been found that the maximum flow of blowby gases into the crankcase 104 substantially corresponds to the maximum output torque (load) and / or speed of the engine 100. Therefore, determining such a maximum set point pump speed helps provide effective control of the flow of exhaust gases throughout the entire operating range of the engine 100.

[0577] For off-highway engines of the type described herein, the maximum output torque (load) of engine 100 is in the range of 1000 to 2500 RPM, preferably in the range of 1100 to 1400 RPM, for example, approximately 1150-1200 RPM. Figure 8 As can be seen from the graph of FIG1 , above 1150-1200 rpm, the set point flow rate decreases as the engine speed increases because the engine can produce a lower maximum torque (load) at higher engine speeds. In alternative embodiments, the maximum output torque (load) of the engine 100 can be at any suitable engine speed.

[0578] In this embodiment, controller 150 is configured to control the pump output based on a setpoint flow rate of the exhaust gas, i.e., a flow rate that has been determined to maintain the concentration of the gaseous fuel in crankcase 104 below its lower flammability limit (4% for hydrogen). However, in other embodiments, the controller may directly derive the speed of electric motor / pump 114 from the determined operating parameters, without requiring the controller to determine the setpoint flow rate as an intermediate step. In other words, the lookup table has the setpoint pump speed directly as a determined output value for a given engine load and engine speed.

[0579] refer to Figure 9B , describes another embodiment of a ventilation control method. In this embodiment, the set point flow is controlled in a closed loop rather than an open loop.

[0580] In step S530, the controller 150 determines the engine torque (load) and the engine speed. At step S532 and at step S532, the lookup table is queried to obtain the set point flow rate. Then, at step S534, the controller 150 sends a signal to the pump 114, thereby operating at the set point speed with which it is expected, thereby providing the set point flow rate. At step S536, the controller 150 uses a suitable measurement method to monitor the actual parameter representing the flow rate. This can be a sensor that measures the pressure difference across the restrictor as described in more detail below, or any other suitable air flow measurement method. If necessary, the controller 150 converts the parameter representing the flow rate into actual flow rate, and at step S536, the controller 150 compares the actual flow rate with the set point flow rate to obtain a flow error. If the flow error is zero (or within a suitable range), the process returns to monitoring the engine speed and load at step S530.

[0581] If the flow error is not zero (or not within the appropriate range), the controller 150 determines at step S538 that a correction is required to the pump speed signal. At step S540, the controller 150 determines whether the error correction is below a predetermined threshold. A large correction (i.e., a large increase or decrease in pump speed) exceeding the predetermined threshold may indicate a malfunction of the ventilation system 110, such as a blockage or obstruction due to ice formation, a gas leak, or a pump or sensor malfunction.

[0582] If not within the allowable amount, then at step S542, the controller 150 outputs an alarm. For example, the alarm output may be to an audio / visual device 154 ( Figure 2 ) (such as a warning light, buzzer, or display). In some embodiments, the engine 100 can be configured to shut down when the controller 150 outputs the alarm signal. In other embodiments, the alarm can additionally or alternatively be sent to a remote location by a suitable telematics system.

[0583] In other embodiments, the controller 150 may determine that an alarm signal is issued based on, for example, the actual and expected pump speeds after the pump speed has been corrected, rather than the correction itself. Furthermore, the controller 150 may impose a delay on issuing an alarm. This may be advantageous if flow is obstructed by ice and running the engine for a period of time may melt the ice and clear the obstruction.

[0584] If the correction is below the allowable threshold, the controller 150 adjusts the signal sent to the pump 114 at step S544 so that the actual flow rate substantially corresponds to the set point flow rate. The controller 150 may use any suitable control logic to determine the correction.

[0585] Thus, in this embodiment, the controller 150 controls the flow rate of the exhaust gas in a closed loop by controlling the pump output (via speed as described, but in other embodiments by changing the vane position, etc.) Advantageously, by feeding the actual flow rate back to the controller 150 and adjusting the pump speed, more accurate control of the flow rate of the exhaust gas can be achieved, particularly for varying operating conditions, such as due to wear of components over the life of the engine or if there is an unexpected blockage or obstruction in the ventilation path 116 (e.g., due to ice formation).

[0586] For example, initially when the engine 100 is first started, the controller 150 may operate in open loop mode and then in closed loop mode after a predetermined time has passed since the engine started. In alternative embodiments, the controller 150 may be configured to operate in only open loop mode or closed loop mode.

[0587] In other embodiments, the controller 150 may control the pump 114 in open loop, ie, signaling a setpoint pump speed for a particular combination of engine speed and engine speed without monitoring the pump 114 to achieve that speed.

[0588] In other embodiments, the set point flow rate may be a set point flow rate for ventilation gas rather than an exhaust gas set point flow rate.

[0589] In practice, where the amount of blowby gas is modeled or mapped as described above, the flow rate may be set to achieve a gaseous fuel concentration lower than the lower flammability limit to maintain an appropriate safety margin.

[0590] Ventilation system 110( Figure 2 ) includes a monitoring system 167 configured to monitor a parameter representing the flow rate of the exhaust gas. The monitoring system 167 is configured to provide one or more outputs based on the monitored parameter.

[0591] Advantageously, monitoring the exhaust gas flow rate can make it possible to determine whether the concentration of the gaseous fuel in the crankcase 104 is above its lower flammability limit without requiring a gas concentration sensor in the crankcase 104 or as a backup to a gas concentration sensor. Such sensors tend to be relatively costly and susceptible to damage (e.g., due to exposure to heat and blowby gases within the crankcase 104). Furthermore, by monitoring the exhaust gas flow rate, it can be determined whether there are any blockages or obstructions in the ventilation path 116 (e.g., due to ice formation) or other operational anomalies that could cause an unexpected increase in the concentration of the gaseous fuel in the crankcase 104.

[0592] In the illustrated embodiment, the monitoring system 167 includes the controller 150. In alternative embodiments (not shown), the monitoring system 167 may include additional or alternative controllers or processors.

[0593] The monitored parameter indicative of flow corresponds to the differential pressure ΔP of the exhaust gas. In an alternative embodiment (not shown), the monitored parameter indicative of flow may be the flow rate of the exhaust gas (e.g., as measured via a flow meter). In the illustrated embodiment, the monitored parameter corresponds to the differential pressure between a first location and a second location of the ventilation path 116. Advantageously, the differential pressure ΔP of the ventilation or exhaust gas can be determined via a relatively low-cost sensor (e.g., a pressure transducer).

[0594] The flowing ventilation / exhaust gas creates a pressure drop across each component of the ventilation system 110. This pressure drop is proportional to the flow rate and can be used to measure the ventilation / exhaust gas flow rate of the ventilation system 110.

[0595] In the illustrated embodiment, as described in more detail below, the pressure drop is measured across the oil separator 130. In alternative embodiments (not shown), the pressure drop across any suitable component of the ventilation system 110 may be measured.

[0596] refer to Figure 10 , oil separator 130 includes an inlet 160 and an outlet 162. Inlet 160 includes a first pressure extraction point 164. The outlet includes a second pressure extraction point 166. A pressure differential ΔP corresponds to the pressure difference between first pressure extraction point 164 and second pressure extraction point 166. First pressure extraction point 164 and second pressure extraction point 166 are located adjacent to each other.

[0597] Further references Figure 2 , monitoring system 167 includes at least one pressure transducer 169 in fluid flow communication with first pressure extraction point 164 and second pressure extraction point 166 .

[0598] In the illustrated embodiment, the monitoring system 167 includes a single pressure transducer 169 in fluid flow communication with the first pressure extraction point 164 and the second pressure extraction point 166. In an alternative embodiment (not shown), the monitoring system 167 may include two pressure transducers 169, each in fluid flow communication with one of the pressure extraction points 164, 166. The difference between the pressures measured by the two transducers is the measured ΔP.

[0599] In the illustrated embodiment, the controller 150 receives a parameter representative of the pressure differential ΔP (eg, pressure differential ΔP) from the at least one pressure transducer 169 .

[0600] In an alternative embodiment (not shown), the first pressure extraction point 164 may be spaced upstream from the oil separator 130, and / or the second pressure extraction point 166 may be spaced downstream from the oil separator 130. This facilitates increasing the distance along the vent path 116 between the first pressure extraction point 164 and the second pressure extraction point 166, thereby increasing the measured pressure differential, which enables a more accurate flow rate to be determined.

[0601] For example, reference Figure 10 , the first pressure extraction point 164 can be adjacent to the outlet 178 of the pump 114 (e.g., the outlet chamber 177 of the pump 114 (discussed in more detail below), or a manifold connected to the outlet 178, can include the first pressure extraction point 164). Additionally or alternatively, the second pressure extraction point 166 can be closer to the gearbox inlet 133 than to the oil separator 130 relative to the ventilation path 116.

[0602] In some embodiments, the distance along the ventilation path 116 between the first pressure extraction point 164 and the second pressure extraction point 166 may be at least two times (e.g., three times or more, or four times or more) the distance along the ventilation path 116 between the oil separator inlet 160 and the oil separator outlet 162 .

[0603] The one or more outputs provided by the monitoring system 167 include a control output. The monitoring system 167 is configured to control the output of the pump 114 via the control output. In the illustrated embodiment, the monitoring system 167 is configured to control the pump output (e.g., based on a parameter representing the pressure differential ΔP) via the controller 150 as previously described. The control output is a control signal (e.g., a pulse width modulated signal) sent from the controller 150 to the pump 114.

[0604] One or more outputs provided by the monitoring system 167 include an alarm output. When the monitored parameter indicates that the flow rate of the exhaust gas is above the set point flow error threshold (e.g., as described above with respect to Figure 9B The monitoring system 167 provides an alarm output when the alarm is detected. The monitoring system can also be combined with Figure 9A The open loop flow controls described operate together to provide an alarm in the absence of a feedback loop to regulate the pump output.

[0605] Advantageously, this configuration of the monitoring system 167 may help prevent the concentration of gaseous fuel in the crankcase 104 from rising above its lower flammability limit, for example due to a blockage or obstruction in the ventilation path 116 (eg, due to ice formation).

[0606] The monitoring system 167 is configured to determine a parameter representing a flow threshold value based on one or more determined operating parameters of the engine, such as the engine speed and / or the engine torque of the engine 100. Advantageously, this can enable the parameter representing the flow threshold value to be based on a set point flow rate of the exhaust gas according to the one or more determined operating parameters.

[0607] In the illustrated embodiment, the engine 100 is configured to shut down when the monitoring system 167 provides an alarm output. Advantageously, this can help prevent the concentration of gaseous fuel in the crankcase 104 from rising above its lower flammability limit.

[0608] In embodiments where the engine 100 is used as a prime mover in the work machine 10, the work machine can be configured to generate a visual and / or audible warning to the operator of the work machine and / or remotely via a suitable telematics system when the monitoring system 167 provides an alert output. Advantageously, this can indicate to the operator that they need to take action (e.g., shut down the engine 100) to prevent the gaseous fuel in the crankcase 104 from rising above its lower flammability limit.

[0609] In an alternative embodiment, monitoring system 167 may be configured to provide only one of a control output and an alarm output.

[0610] In the illustrated embodiment, pump 114 is a side channel pump (also known as a side channel blower).

[0611] Figure 10 A pump assembly 170 including the pump 114 is shown.

[0612] The pump 114 includes a housing 172 including a first inlet 174, a second inlet 176, and an outlet 178. The pump 114 includes an impeller (not shown) rotatable about an axis of rotation within the housing 172 to move fluid at the inlets 174, 176 to the outlet 178. The first inlet 174 and the second inlet 176 are disposed on either side of the plane of rotation of the impeller.

[0613] In the illustrated embodiment, the first inlet 174 and the second inlet 176 are adjacent to each other. Figure 10 As shown, the pump 114 includes an outlet chamber 177 including an outlet 178. Fluid flowing into the inlets 174, 176 flows around the circumference of the housing 172 on respective sides of the impeller's plane of rotation, then merges in the outlet chamber 177 and flows through the outlet 178. The outlet chamber 177 is interposed between the first inlet 174 and the second inlet 176.

[0614] Pump 114 is configured such that rotation of the impeller about its axis of rotation generates first and second counter-rotating vortices in the fluid moving from first and second inlets 174, 176, respectively, to outlet 178. The counter-rotating vortices flow on opposite sides of the impeller's plane of rotation.

[0615] In the embodiment shown, the impeller is rotated via an electric motor. In alternative embodiments (not shown), the impeller may be rotated via any suitable power source.

[0616] The pump assembly 170 further includes a vortex generator 190 in fluid communication with the first inlet 174 and the second inlet 176. The vortex generator 190 is configured to generate first and second counter-rotating inlet vortices Vi1, Vi2 ( Figure 13 ).

[0617] Advantageously, generating counter-rotating inlet vortices Vi1 , Vi2 in the fluid moving into the first and second inlets 174 , 176 helps improve the efficiency of the pump 114 because the work required by the pump 114 to induce counter-rotating vortices in the fluid moving from the inlets 174 , 176 to the outlet 178 is reduced.

[0618] refer to Figure 11 and Figure 12 The vortex generator 190 includes a first vortex chamber 192 and a second vortex chamber 194 configured to generate a first inlet vortex Vi1 and a second inlet vortex Vi2, respectively. The vortex generator 190 includes an inlet 196 in fluid communication with the vortex chambers 192 and 194. The vortex generator 190 is configured such that the fluid travels from the inlet 196 to the first inlet 174 and the second inlet 176 of the pump 114 via the first vortex chamber 192 and the second vortex chamber 194, respectively.

[0619] The vortex generator 190 is configured such that the first vortex chamber 192 and the second vortex chamber 194 receive a circumferential inlet flow F from the inlet 196. The circumferential inlet flow F (formed by Figure 12 The circumferential inlet flow F (indicated by the dashed arrows in FIG) is arranged to flow along the circumference of the first vortex chamber 192 and the second vortex chamber 194 so as to form counter-rotating inlet vortices Vi1 and Vi2. Advantageously, the circumferential inlet flow F enables the vortex chambers 192 and 194 to generate the first inlet vortex Vi1 and the second inlet vortex Vi2 without the need for any moving parts.

[0620] like Figure 11As shown, the vortex generator 190 includes a first outlet 200 and a second outlet 202. The outlets 200, 202 fluidly connect the respective first and second vortex chambers 192, 194 to the respective first and second inlets 174, 176 of the pump 114. The vortex generator 190 is configured such that a first inlet vortex Vi1 and a second inlet vortex Vi2 travel through the first outlet 200 and the second outlet 202, respectively.

[0621] In the illustrated embodiment, the outlets 200 , 202 are substantially orthogonal to the direction of the circumferential inlet flow F. In alternative embodiments (not shown), the outlets 200 , 202 may extend at any suitable angle to the direction of the circumferential inlet flow F.

[0622] like Figure 11 As shown, each of the first vortex chamber 192 and the second vortex chamber 194 is substantially bowl-shaped. Such a shape can help maximize the intensity of the first inlet vortex Vi1 and the second inlet vortex Vi2 generated therein. In alternative embodiments (not shown), the vortex chambers 192, 194 can have any suitable shape and configuration.

[0623] like Figure 12 As shown, the vortex generator 190 includes a wall 204 shared by the first vortex chamber 192 and the second vortex chamber 194. The wall is shaped to separate the fluid flowing from the inlet 196 toward the wall 204 into two counter-rotating inlet vortices corresponding to the first inlet vortex Vi1 and the second inlet vortex Vi2. The wall 204 includes two arcuate portions 204a and 204b connected by a ridge portion 204c. The vertex 206 of the ridge portion 204c separates the first vortex chamber 192 and the second vortex chamber 194.

[0624] like Figure 10 As shown, vortex generator 190 is mounted to housing 172 of pump 114. In the illustrated embodiment, fasteners, such as bolts, are used to mount vortex generator 190 to housing 172. In alternative embodiments (not shown), vortex generator 190 may be mounted to pump 114 via any suitable means or may be part of the inlet casting of pump 114.

[0625] It should be understood that while the vortex generator 190 has been described with respect to its use in a side channel pump in a particular internal combustion engine application, it is not limited to such use and may also benefit side channel pumps in other industrial applications. While in this embodiment the pump is electrically driven, in other embodiments it may instead be mechanically or hydraulically driven, for example.

[0626] Now refer to Figure 13 、 Figure 14 and Figure 15, the oil pre-separator 128 can be seen in greater detail. The oil pre-separator 128 is arranged to be mounted within the crankcase 104 of the internal combustion engine 100, or in this embodiment, within the gearbox 109 of the internal combustion engine 100. In an alternative embodiment (not shown), the oil pre-separator 128 can be mounted near the engine structure 102 (i.e., external to the engine structure 102). For example, the oil pre-separator 128 can be mounted adjacent to the gearbox 109 or the crankcase 104.

[0627] The pre-separator 128 includes an extraction conduit 310 defining a mouth 312 for extracting gas from the gearbox 109 through an aperture 315 in a wall 314 of the gearbox 109 .

[0628] In this embodiment, the mouth 312 terminates in an outwardly turned lip 332 .

[0629] In this embodiment, the pre-separator 128 is a self-contained unit that is mounted to the wall 314 of the gearbox 109 via a mounting flange 318. The mounting flange 318 is arranged so that it can be mounted to the outer surface of the wall 314 via suitable fasteners, with the mouth 312 protruding into the gearbox 109. The extraction conduit defines an axis C, and the mounting flange 318 is substantially perpendicular to the axis. In another embodiment (not shown), the flange 318 can be inclined at any suitable angle relative to the axis C.

[0630] The downstream end of the extraction conduit 310 terminates in a spigot 320 to which a suitable hose may be connected, such as a Figure 10 shown.

[0631] A plate 316 is axially spaced from and covers the mouth 312 to act as a baffle.

[0632] Special References Figure 15 , plate 316 includes an angled portion 322 that is arranged to extend from an axially spaced position and terminate at an edge 324 that is axially aligned with or axially overlaps at least the mouth. In this embodiment, edge 324 axially overlaps mouth 312. Edge 324 is laterally spaced from the mouth. Plate 316 also includes a flat portion 326 that covers mouth 312, and angled portion 322 extends around the periphery of the flat portion. It can be seen that flat portion 326 is circular and angled portion 322 is arranged concentrically around the circular portion. In other embodiments, flat portion 326 can be omitted, or, for example, be square or triangular, and angled portion 322 can form a truncated pyramid shape.

[0633] The pre-separator 128 includes a flow diverter 328 extending around the extraction conduit to divert oil flowing down the wall 314 of the gearbox 109 away from the mouth 312 of the extraction conduit 310. In this embodiment, the mouth 312 having an outwardly turned lip 332 and protruding from the flange 318 serves as the flow diverter 328.

[0634] A series of legs 330 support the plate 316 on the flange 318 while providing a path for the exhaust gas to enter the pre-separator 128 and flow into the mouth 312 via a tortuous path indicated by the dashed arrows.

[0635] The dimensions of the various components described above have been carefully selected to reduce oil entrainment into the pump 114 and the oil separator 130 .

[0636] The ratio between the diameter or minimum width of the plate and the inner diameter of the extraction conduit 310 can be between about 4:1 and 2.5:1, for example, about 3:1. For example, the diameter of the plate 316 can be about 66 mm and the diameter of the extraction conduit can be about 22 mm. The angled portion of the plate 316 can terminate axially about 5-6 mm from an adjacent wall (e.g., the wall of the flange 318). In other words, the length of the leg is 5-6 mm. The outward-turned lip 332 can be spaced further from the wall of the diverter 328 than the edge 324, for example, at least 8 mm. The outward-turned lip 332 can extend at least 6 mm, for example 9 mm, beyond the inner diameter of the extraction conduit 310 to define a lip of at least 2 mm, for example 4 mm, thereby providing a further barrier to the flow of oil into the mouth 312.

[0637] Figure 16 An oil pre-separator 128 is shown mounted in-situ within the gearbox 109, positioned above and laterally offset from the camshaft gear 340, which is itself driven by the crankshaft gear 342. It will be appreciated that when the engine 100 is in operation, these gears will splash oil within the gearbox 109 and create a mist suspended within the gases of the gearbox 109. The tortuous, indirect path for the exhaust gases through the pre-separator 128 prevents splashed oil from entering the extraction conduit 310 and also creates flow conditions that cause the suspended oil to precipitate out of the gases.

[0638] It has been found that the pre-separator 128 as described above reduces the oil concentration in the gas by a factor of at least 2.5, more typically by a factor of at least 4, when operated at a flow rate required to ventilate the crankcase of a hydrogen fueled engine, which is at least 30 l / min per litre of displacement of the internal combustion engine, and typically in the range of 30 l / min to 80 l / min per litre of displacement of the internal combustion engine.

[0639] It has been found that the pre-separator 128 in combination with the oil separator 130 can reduce oil carryover in the exhaust gas flow path downstream of the separator to less than or equal to 1 g / hr of engine operation, typically less than or equal to 0.5 g / hr of engine operation.

[0640] As mentioned above, the engine 100 includes an engine structure 102. The engine structure is typically formed from one or more cast components that provide structural strength to the engine 100 and mount various moving parts, such as one or more pistons, as is well known. Specifically, in this embodiment, the engine structure 102 includes at least a cylinder block 108, a crankcase 104, and a gearbox 109.

[0641] In the drawings, the engine structure 102 is depicted such that the axes of the cylinders 112 arranged vertically within the cylinder block 108 are aligned with the axis z (in FIG. Figure 1 10). The crankcase 104 is located directly below the cylinder block 108 on axis z. In this embodiment, the engine structure 102 includes four cylinders 112 arranged inline along an axis x that is orthogonal to axis z. The gearbox 109 is located at one end of the cylinder block 108 and crankcase 104 along axis x. Conventionally, the gearbox 109 is considered to be located at the rear of the cylinder block 108 / crankcase 104, reflecting the conventional installation of the engine 100 in the work machine 10, wherein the axis x is aligned fore-aft with the work machine 10 and the engine output is located at the rear. It should be understood that in practice, the engine 100 can actually be oriented differently, for example, laterally oriented and / or tilted relative to the work machine 10 so that the cylinders 112 have axes that are tilted relative to axis z.

[0642] Furthermore, a portion of the gearbox 109 projects laterally beyond the side of the cylinder block 108 / crankcase 104 on another axis y that is orthogonal to both the axes z and x. In this embodiment, the gearbox 109 projects from the left-hand side of the cylinder block 108 / crankcase 104, but in other embodiments the gearbox could project from the right-hand side.

[0643] Pump 114 is arranged to exhaust blowby gases contained within crankcase 104 and is positioned adjacent to engine structure 102. A passage extends from gearbox 109 to pump 114, placing pump 114 in fluid flow communication with crankcase 104. In this embodiment, the passage is an outflow portion 126 for extracting blowby gases, but in other embodiments, the passage may be an inlet passage for blowing ventilation gases into crankcase 104. The passage includes an oil pre-separator 128 located upstream of pump 114.

[0644] The pump 114 is positioned adjacent to a side of the engine structure 102, such as a side of the cylinder block 108, in front of the gearbox 109. In this embodiment, the pump 114 is mounted to the engine structure 102 as an "on-engine" component. That is, it is assembled to the engine structure 102 at the engine assembly plant and then installed in situ in the work machine 10 with the pump 114 at the machine assembly plant. The engine assembly plant may be located remotely from the work machine 10 assembly plant, or it may be co-located. In either case, it is generally more efficient to locate the pump 114 "on-engine" because it is generally accessible to mount these components to the exterior of the engine. In contrast, separately mounting the pump to the engine compartment of the work machine 10 and connecting the various hoses and power supply after the engine 100 is assembled is generally less accessible and therefore more time-consuming and costly. Figure 17 The pump 114 is shown mounted to the engine structure 102 via an adapter bracket 348 so that it can be bolted to a pre-existing mount on the engine structure 102. In other embodiments, the pump 114 may be directly mounted, further enhancing the compactness of the installation.

[0645] Furthermore, gaseous fuel engines, such as hydrogen fuel engines, generally do not require a fuel injection pump because the gas is stored under pressure in tanks 12 on the machine 10 ( Figure 22 ) and is supplied at a pressure greater than the fuel injection pressure, so no pump is required to pressurize it. The installation location of pump 114 is generally the location where the fuel injection pump is installed on a liquid (e.g., diesel) fuel engine. Therefore, if the base engine for conversion to a gaseous fuel engine is a diesel engine, the location of the fuel injection pump becomes available for other uses in the gaseous fuel engine.

[0646] Pump 114 is positioned at least partially within the spatial envelope defined by the virtual longitudinal projection forward of gearbox 109. In some embodiments, pump 114 can be mounted entirely within the envelope. This arrangement further minimizes the overall spatial envelope required for pump 114 and engine 100 as a whole. For example, if a machine were to receive a gaseous fuel engine instead of a conventional diesel-fueled engine, this could eliminate the need to reconfigure the engine compartment or nacelle on a particular machine.

[0647] One or more auxiliary components are typically mounted to the engine structure 102 in the area surrounding the pump 114. In this embodiment, these components include a lubricating oil filler 341, a lubricating oil cooler 343, an inlet manifold 344, and / or an electronic control unit 346 (see FIG. Figure 3). The pump 114 projects laterally less than or equal to the maximum width of one or more auxiliary components. This further increases the likelihood that the engine 100 will not require a different installation envelope than an equivalent engine running on liquid fuel (e.g., diesel).

[0648] In this embodiment, the auxiliary components limit the available space in the x- and z-directions. Thus, the pump occupies a space of less than or equal to 200 mm in the longitudinal direction (x), less than or equal to 240 mm in the vertical direction, and less than or equal to 175 mm in the transverse direction (y).

[0649] The first section 126a of the outflow portion 126 extends between the pump 114 and the orifice 315 in the gearbox. Specifically, in this embodiment, the first section 126a is connected to the sleeve 320 of the oil pre-separator 128, which is mounted to the orifice 315, as shown in FIG. Figure 14 and Figure 17 shown.

[0650] A port 315 is located in the forward facing wall 314 of the gearbox 109. In embodiments where the engine is derived from a liquid fuel engine, a port is typically provided at this location for carrying the drive shaft from the gearbox 109 to the fuel injection pump, so this port can be reused without reconfiguring the engine.

[0651] As mentioned above, the pump 114 in this embodiment is a side channel pump.The pump 114 is mounted so that the axis of rotation of the impeller is substantially parallel to the longitudinal axis x.

[0652] In an alternative embodiment, the impeller's axis of rotation may be substantially vertical in the normal operating orientation of engine 100. For example, the impeller's axis of rotation may be substantially parallel to the axis of cylinder 112. This orientation of the impeller may assist in draining oil from pump 114.

[0653] The pump 114 is a self-contained unit having an electric drive motor positioned toward the front of the engine 100 with the impeller toward the rear. The first and second inlets 174, 176 face laterally outward, and the outlet 178 faces rearward. This arrangement can further minimize the required space.

[0654] refer to Figure 10 and Figure 17 , the downstream oil separator 130 is located longitudinally between the forward-facing wall 314 of the gearbox 109 and the pump 114. This location enables the first section 126a of the outflow portion 126 from the oil pre-separator 128 to be routed around the oil separator 130 to the first inlet 174 and the second inlet 176 of the pump 114.

[0655] In addition, this allows the pump outlet 178 to be directly connected to the oil separator inlet 160, and the oil separator gas outlet 162 can be directed back into the second section 126b of the outflow portion 126 in the gearbox 109. The oil passage 129 from the oil separator 130 back to the crankcase 104 can also be short and run under gravity. In this embodiment, the oil separator 130 is mounted to the pump 114 via fasteners.

[0656] This arrangement enables the longitudinal dimension of the spatial extent occupied by the pump 114 and the oil separator 130 to be less than or equal to 200 mm.

[0657] In one embodiment, the oil pre-separator 128, pump 114, and oil separator 130 are provided as a pre-assembled unit to be installed to the engine 100. The pre-assembled unit may also include hoses for exhausting gas from the oil separator and returning oil.

[0658] In the illustrated embodiment, the oil separator inlet 160 is disposed substantially at the same level as the outlet 178 of the pump 114. In alternative embodiments, the oil separator inlet 160 may be disposed lower than the pump outlet 178. Advantageously, this may assist in separating the oil from the exhaust gases.

[0659] Now refer to Figures 18 to 21 The oil separator is indicated at 130. The oil separator 130 is arranged to receive exhaust gas from the crankcase 104. As mentioned above, in this embodiment, the oil separator 130 is a cyclonic oil separator. The cyclonic oil separator 130 causes the exhaust gas to flow through it to form a vortex. The flow of the exhaust gas through the separator 130 is Figure 19 As shown in FIG, indicated by arrow 400. Figure 19 As shown, exhaust gas enters the separator 130 through the inlet 160 and forms a vortex 402. The exhaust gas then exits the oil separator 130 via the outlet 162.

[0660] The centrifugal action of the vortex 402 separates the oil from the exhaust gas, causing the separated oil to be thrown to the wall 409 of the separator 130. The separated oil flows downward along the wall 409 to exit the separator through the oil outlet 404, as shown. Figure 19 As shown by arrow 406 in FIG. The oil is then returned to the oil tank 122 for reuse.

[0661] The use of a cyclonic oil separator allows the oil separator 130 to function as a passive component. Such a passive component is inherently simple and advantageously does not require an external power source to reduce the concentration of oil in the exhaust gas. A cyclonic oil separator, such as the oil separator 130, is more effective when used in a gaseous fuel engine of the type of this embodiment due to the higher gas flow rates when compared to, for example, a diesel engine, as described in further detail below.

[0662] The oil separator 130 has a first upper end 411 and a second lower end 413. The terms "upper" and "lower" refer to the relative positions of the separator ends 411, 413 when the separator 130 is installed in the ventilation system 110.

[0663] The oil separator 130 defines an internal chamber 408. Figure 20 As shown, chamber 408 has a truncated cone portion 410. The truncated cone portion 410 defines a truncated cone portion longitudinal axis X. The truncated cone portion 410 has an apex 412 positioned toward a second end 413. Chamber 408 has a cap 414 positioned toward a first end 411 of separator 130. The cap defines a cap plane Y, as shown in FIG. Figure 18 shown.

[0664] The inlet 160 defines an inlet longitudinal axis Z. The inlet longitudinal axis Z is oriented at a non-zero angle to the roof plane Y at the point where the inlet 160 meets the chamber 408. That is, the inlet longitudinal axis Z is not parallel to the roof plane Y at the point where the inlet 160 meets the chamber 408, as shown in FIG. Figure 18 The angle k is shown in FIG.

[0665] The inlet longitudinal axis Z is oriented toward the apex 412, i.e., toward the second end 413 of the chamber 408. This orientation of the inlet 160 directs the exhaust gas flow toward the apex 412. It has been discovered that orienting the inlet 160 toward the apex 412 of the chamber 408 improves the flow of exhaust gas through the chamber 408 by directing the gas flow toward the apex. Additionally, this angle enables the oil separator 130 to be packaged between the pump 114, associated hoses, and the engine structure 102 and gearbox 109, as described above.

[0666] In this embodiment, the inlet longitudinal axis Z is oriented at an angle k between 1° and 45° to the roof plane Y. In one embodiment, the inlet longitudinal axis Z is oriented at an angle k between 10° and 35° to the roof plane Y. It has been found that an angle of the inlet longitudinal axis Z to the roof plane Y within this range advantageously provides a reduction in cyclone pressure drop while maintaining oil separation efficiency, thereby improving separation of oil from the exhaust gas.

[0667] In this embodiment, the oil outlet 404 is substantially cylindrical and defines an outlet longitudinal axis A (see Figure 20 The oil outlet 404 is located at the second end 413 of the separator 130. Thus, gravity causes the separated oil to leave the chamber 408 via the outlet 404. In this embodiment, the outlet longitudinal axis A makes an angle j with the truncated cone longitudinal axis X in the range of 0° to 45° (see Figure 20 In this embodiment, the length of the outlet 404 is between 10 mm and 50 mm.

[0668] Figure 19 A first pressure extraction point 164 and a second pressure extraction point 166 are shown. In this embodiment, Figure 19 As shown, first and second transducer extraction points 164, 166 are located at first end 411 of separator 130. In this embodiment, both first and second transducer extraction points 164, 166 define an extraction point longitudinal axis B. In this embodiment, the extraction point longitudinal axes B are substantially parallel to one another. As described above, first extraction point 164 and second extraction point 166 are adjacent to one another. That is, first extraction point 164 and second pressure extraction point 166 are located at the same end of separator 130 and are not separated by any other components.

[0669] As mentioned above Figure 2 As discussed, monitoring system 167 includes at least one pressure transducer 169 in fluid flow communication with first pressure extraction point 164 and second pressure extraction point 166. In this embodiment, single pressure transducer 169 is mounted remotely relative to the separator. That is, in this embodiment, transducer 169 is mounted to inlet 344 where it may be less exposed to vibrations.

[0670] In an alternative embodiment, monitoring system 167 includes two pressure transducers, both mounted to inlet manifold 344. In an alternative embodiment, one or more pressure transducers 169 are mounted to oil separator 130. Advantageously, this arrangement is compact and reduces the number of components required.

[0671] refer to Figure 19 and Figure 20 , chamber 408 includes a cylindrical portion 416. Cylindrical portion 416 is adjacent to truncated cone portion 410. Cylindrical portion 416 and truncated cone portion 410 together define chamber 408. Cylindrical portion 416 is distal to apex 412, i.e., cylindrical portion 416 is proximal to first end 411 of separator 130.

[0672] The cylindrical portion 416 defines a cylindrical portion longitudinal axis C. In this embodiment, the angle between the frusto-conical section longitudinal axis X and the cylindrical portion longitudinal axis C is in the range of 0° to 30°. This angle also aids in spatially enclosing the oil separator 130, as described above. It has been found that this angle does not significantly reduce the separation efficiency of the oil separator.

[0673] In this embodiment, the length of the cylindrical portion 416 is in the range of 50 mm to 200 mm. The inner diameter of the cylindrical portion 416 is in the range of 30 mm to 80 mm. That is, the maximum inner diameter of the chamber 408 is in the range of 30 mm to 80 mm.

[0674] In this embodiment, the length of the frustoconical portion 410 is in the range of 50 mm to 200 mm. "Length" is used to refer to the distance in the direction of the respective longitudinal axis of each feature.

[0675] In this embodiment, the gas outlet 162 includes a tube 418 extending within the chamber 408. The tube 418 defines a tube longitudinal axis D (at Figure 20 ). In this embodiment, the tube longitudinal axis D is coaxial with the cylindrical portion longitudinal axis C. In an alternative embodiment, the tube longitudinal axis D is at an angle of 10 degrees or less to the cylindrical portion longitudinal axis C. In an alternative embodiment, the tube longitudinal axis D is at an angle of 5 degrees or less to the cylindrical portion longitudinal axis C. In an alternative embodiment, as in this embodiment, the tube longitudinal axis D is substantially parallel to the cylindrical portion longitudinal axis C, but when parallel to the cylindrical portion longitudinal axis C, the tube longitudinal axis D is not necessarily coaxial with the cylindrical portion longitudinal axis C.

[0676] In this embodiment, tube 418 is a substantially cylindrical tube. In alternative embodiments, the tube has some other cross-sectional profiles. In this embodiment, the tube outer diameter m is in the range of 17-45 mm.

[0677] In this embodiment, tube 418 has a length between 25 mm and 75 mm. In this embodiment, tube 418 extends within chamber 408 for between one-quarter and one-third of the length of chamber 408. In an alternative embodiment (not shown), tube 418 may extend within chamber 408 for between one-quarter and one-third of the length of cylindrical portion 416.

[0678] In this embodiment, the outlet 162 comprises an outlet orifice 420 defined by the chamber 408, i.e., the outlet orifice 420 is located at a wall of the chamber 408. In this embodiment, the outlet orifice 420 is located at the first end 411 of the separator 130, i.e., at the upper end of the chamber 408, away from the apex 412.

[0679] In this embodiment, Figure 18 、 Figure 19 、 Figure 20 and Figure 21 As shown, the frustoconical portion longitudinal axis X passes through the plane defined by the maximum diameter of the frustoconical portion 410 at a non-right angle to further improve packaging in the aforementioned position. In an alternative embodiment, the frustoconical portion is a true circular frustoconical portion.

[0680] The frustoconical portion 410 has a wall 422. The angle of the conical portion wall 422 relative to the cylindrical portion longitudinal axis C is in the range of 0° to 30°.

[0681] As described above, ventilation system 110 includes controller 150 arranged to control the output of pump 114 based on one or more determined operating parameters of engine 100. Thus, by controlling pump 114, the flow of exhaust gas (and hence ventilation gas) can be controlled.

[0682] In this embodiment, the controller 150 is configured to control the pump 114 so that the maximum flow rate of exhaust gas is at an engine speed of 1000 to 2500 rpm. In one embodiment, the controller is configured to control the pump so that the maximum flow rate of exhaust gas is at an engine speed of 1100 to 1400 rpm. In this embodiment, the controller 150 is configured to control the pump 114 so that the maximum flow rate of exhaust gas is at an engine speed of 1150-1200 rpm.

[0683] At a flow rate of exhaust gas through separator 130 of at least 30 liters per minute per liter of engine displacement (i.e., at least about 130 liters / min for the 4.4 liter engine of this embodiment), a reduction in oil concentration in the exhaust gas of at least a factor of 10 is achieved. In an alternative embodiment, at such an exhaust gas flow rate, a reduction in oil concentration in the exhaust gas of at least a factor of 20 is achieved. In an alternative embodiment, at a flow rate of at least 60 liters per minute per liter of engine displacement, a reduction in oil concentration in the exhaust gas of at least a factor of 10 is achieved. In one embodiment, at such an exhaust gas flow rate, a reduction in oil concentration in the exhaust gas of at least a factor of 20 is achieved.

[0684] The specific geometry of the cyclonic separator 130 allows these multiples of reduction in oil concentration to be achieved at these flow rates. As demonstrated above by the size of the chamber 408, the separator 130 is surprisingly able to achieve such reductions in oil concentration despite its relatively small size.

[0685] The small size facilitates packaging the oil separator 130 with the pump 114 in the aforementioned location.

[0686] In this embodiment, the engine displacement is within the range of 0.75-1.50 L per cylinder. That is, as described above, the above-described engine 100 is generally suitable for use as a prime mover in a working machine.

[0687] In this embodiment, the separator 130 is formed of a plastic material. In this embodiment, the separator 130 is formed by molded parts of a material (plastic or other material) assembled together. In this embodiment, the separator 130 has a first molded part and a second molded part assembled together.

[0688] In this embodiment, the separator 130 is made of a plastic composite material having conductive properties.

[0689] In this embodiment, in addition to separator 130 being made of a conductive plastic composite material, one or more or all auxiliary components of ventilation system 110 are also made of the same conductive plastic composite material. The composite material is configured to dissipate static charge. The composite material's conductive properties allow static charge to be dissipated through ventilation system 110, thereby minimizing the potential for sparks. By forming components from this composite material, electrical connections are provided, allowing all components of system 110 to maintain the same static charge while advantageously avoiding the need for external wiring.

[0690] In this embodiment, one or more of the following auxiliary components are made of composite material: oil pre-separator 128 , oil separator 130 , manifolds (such as vortex generators 190 ), conduits 146 a , 146 b , and pump housing 172 .

[0691] In this embodiment, the composite material is formed by embedding a conductive material within a plastic material. In alternative embodiments, the plastic material is at least partially coated with the conductive material. That is, the plastic material may be completely coated internally with the conductive material, or the plastic material may be partially coated with the conductive material on its inner surfaces (as well as surfaces that contact adjacent components to maintain continuity) to provide electrical continuity between the components. In this embodiment, the composite material comprises between 20% and 40% conductive material. In an alternative embodiment, the composite material comprises between 25% and 35% conductive material. In one embodiment, the composite material comprises substantially 30% conductive material. In this embodiment, the composite material is a composite material known as PA66CF30, i.e., PA66 polyamide with 30% carbon fiber. In alternative embodiments, the conductive material is some material other than carbon fiber. In some other embodiments, the conductive material is some other percentage of carbon fiber. In one embodiment, the conductive material is graphite. In one embodiment, the conductive material is a metallic conductive material.

[0692] In this embodiment, the conductive material is formed from strands of wire. That is, the conductive material has a wire portion. In an alternative embodiment, the conductive material is in the form of a powder. In one embodiment, the conductive material is in the form of graphite powder.

[0693] Such composite materials provide some electrical insulation to the component, but the insulation is reduced to the point where the material is sufficiently conductive to avoid static charge buildup. That is, the insulation is reduced to the point where static electricity can be dissipated.

[0694] The use of composite plastic materials advantageously allows for variable wall thicknesses, as well as desired wall thicknesses for auxiliary components.

[0695] In this embodiment, with all auxiliary components comprising the described composite material, the ventilation system 110 has electrical continuity throughout the entire system 110 .

[0696] The engine 100 may also include a conductivity monitoring system for monitoring the conductivity of the ventilation system 110. In this embodiment, the conductivity monitoring system includes at least one sensor for detecting conductivity. In this embodiment, the conductivity monitoring system (not shown) includes a series of conductivity sensors throughout the system 110.

[0697] Figures 23 to 28 Another embodiment of a ventilation system 1110 is shown in which like components are labeled with like reference numerals, but with the prefix "1." Only those components that differ from the ventilation system 110 of the first embodiment will be discussed in more detail.

[0698] Figure 23 An engine 1100 is shown including a ventilation system 1110. Compared to the engine 100 of the first embodiment, the engine 1100 is an in-line six-cylinder engine rather than a four-cylinder engine, but its basic layout and construction are similar to those of the engine 100.

[0699] Due to having a greater number of cylinders and, in some embodiments, a greater specific output, engine 1100 may produce a greater volume of blowby gases under similar operating conditions than engine 100. Therefore, a larger capacity ventilation system 1110 is required to dilute and convey the blowby gases away from engine 1100.

[0700] Additionally, greater separation capacity may be desired to minimize oil (and water) entrainment back into the intake system 115 .

[0701] Figure 24 With Figure 2 The ventilation system 1110 of this embodiment is shown in a similar manner to the first embodiment in FIG, except that the engine 1100 and the intake system 1115 are shown in a more simplified form. Figure 25 The physical layout of ventilation system 1110 mounted on engine 1100 is shown.

[0702] from Figure 24 and Figure 25 As can be seen, to increase the flow of ventilation gas, the ventilation system includes two pumps 1114a and 1114b arranged in parallel downstream of the pre-separator 1128. The outflow path 1126 includes a flow splitter 1180 in the form of a Y-piece 1180 to evenly distribute the exhaust gas flow to each pump 1114a, 1114b.

[0703] In this embodiment, the exhaust gas then flows from the pump outlets 1178a, 1178b into the corresponding oil separator inlets 1160a, 1160b and rejoins in the oil separator 1130. Downstream of the oil separator 1130, the exhaust gas is returned to the intake passage 1140 via a pipe external to the engine 1100, rather than being directed back through a passage within the engine 1100.

[0704] refer to Figure 25 As can be seen, the outflow portion is substantially symmetrical, providing substantially equal flow to each pump. Furthermore, it should be noted that the path descends to reach the Y-piece 1180, ascends before entering each pump 1114a, 1114b, descends from the pump into the bottom of the oil separator 1130, and then ascends again through the oil separator and back into the intake passage 1140. It has been discovered that the multiple changes in direction naturally aid in the separation of oil from the exhaust gases.

[0705] In this embodiment, pumps 1114a, 1114b are identical to the single pump 114 of the first embodiment and also include vortex generators 1190a, 1190b identical to generator 190 of the first embodiment. However, pumps 1114a, 1114b are oriented so that their axes of rotation are vertical rather than horizontal (i.e., substantially parallel to the axis along which the pistons of engine 1100 move in their respective cylinders). This results in the impellers of the pumps being substantially horizontal, which has been found to facilitate the removal of oil that has settled from the gas discharged from pumps 1114a, 1114b.

[0706] from Figure 25 As can be seen in FIG, the Y-piece 1180 further comprises an oil drain outlet 1181 at its bottom, so that oil that settles in the pumps 1114a, 1114b, the pump piping, and between the pre-separator 1128 and the Y-piece 1180 can be drained.

[0707] Compared with the first embodiment, the oil separator 1130 of this embodiment is a labyrinth separator.

[0708] Figure 26 、 Figure 27 and Figure 28 A vertical cross section through the oil separator 1130 is depicted, which is identical for the upper portion of the oil separator (which passes through the center), but deviates into separate but parallel planes in the lower portion. Figure 26 The lower part also passes through the center, but Figure 27 The portion below the horizontal dotted line is parallel to Figure 26 on the plane of the paper, but offset from the paper, and Figure 28 The middle and lower parts are parallel but offset from the paper.

[0709] The oil separator 1130 is substantially cylindrical, with its axis being substantially vertical. In this embodiment, the oil separator 1130 is mounted midway between the pumps 1114a and 1114b. The oil separator comprises an outer shell 1417 and an inner wall 1416 spaced apart therefrom. The inner wall defines an internal chamber 1408 therein and an annular space 1415 between the inner wall and the outer shell 1417. The oil separator inlets 1160a and 1160b are located near the bottom of the oil separator 1130, and a single gas outlet 1162 is provided at the top of the internal chamber 1408, so that, in use, the flow of exhaust gas is directed generally upward.

[0710] An array of baffles 1419 is located within the interior chamber 1408, extending in an alternating pattern from opposite sides of the interior wall 1416. Each baffle 1419 slopes upward to its free end, and each free end overlaps with those above and / or below extending from the opposite side and diverts the exhaust gas flow into a labyrinthine path.

[0711] The drain holes 1421 are provided just above the location where each baffle 1419 meets the inner wall 1416, so that the oil impinging on the baffle 1419 and the inner wall 1416 is drained into the annular space 1415 between the inner wall and the housing. It should be understood that in other embodiments, the number, shape, and configuration may be changed as desired.

[0712] Oil accumulated in the annular space can drain under gravity via drain outlet 1404a.A second drain outlet 1404b allows oil accumulated in the interior chamber 1408 and the piping between the pumps 1114a and 1114b and the separator inlets 1160a and 1160b to also drain under gravity.

[0713] Similar to the oil separator 130 of the first embodiment, separator 1130 has pressure extraction points 1164 and 1166 near inlets 1160a and 1160b and gas outlet 1162 respectively, so that the pressure drop across the oil separator can be measured as a way to determine the flow rate of the exhaust gas.

[0714] In this embodiment, the oil separator operates by a combination of reducing the velocity of the exhaust gas, changing its flow direction, and having a large surface area so that oil droplets tend to fall out of suspension and settle on the baffle 1419 and inner wall 1416.

[0715] refer to Figure 23 、 Figure 24 and Figure 25 The oil discharge outlets 1181 , 1404 a , and 1404 b supply the oil return passage 1129 , which returns the oil to the crankcase 1104 .

[0716] In other embodiments, it should be understood that the pump 114 of the first embodiment can be used in combination with the above-described labyrinth separator 1130 , and the above-described pumps 1114 a , 1114 b can be used in combination with the oil separator 130 of the first embodiment.

[0717] It should be understood that the outputs of the pumps 1114a, 1114b may be controlled by the controller 1150 in a manner consistent with the above referenced Figure 9A and Figure 9B The controller 150 controls the pump 114 in a similar manner and utilizes the pressure drop across the oil separator 1130 .

[0718] One or more embodiments have been described above by way of example only, and it should be understood that variations are possible without departing from the scope of protection offered by the appended claims.

Claims

1. A gas fuel internal combustion engine comprising: An engine structure, comprising: Cylinder body, crankcase, and Gearbox; a pump for venting blowby gases contained within the crankcase and positioned adjacent the engine structure; and A passage extends from one of the crankcase and the gearbox to the pump, placing the pump in fluid flow communication with the crankcase.

2. The engine according to claim 1, wherein The pump is positioned forward of the gearbox adjacent a side of the engine structure, such as a side of the cylinder block.

3. The engine according to claim 2, wherein: The pump is mounted to the engine structure.

4. The engine according to claim 2 or claim 3, wherein: The gearbox extends transversely a greater distance than at least the cylinder block, and the pump is at least partially positioned within a spatial extent defined by an imaginary longitudinal projection of the front of the gearbox, optionally wherein the pump is fully mounted within said extent.

5. The engine according to any one of claims 2 to 4, further comprising one or more auxiliary components mounted to the engine structure, such as one or more of a lubricating oil filler, a lubricating oil cooler, an inlet manifold and / or an electronic control unit, and wherein the pump protrudes laterally by less than or equal to the maximum width of one or more of the auxiliary components.

6. The engine according to any one of claims 2 to 5, wherein: The pump occupies a spatial extent of less than or equal to 200 mm in the longitudinal direction (x), and / or less than or equal to 240 mm in the vertical direction (z), and / or less than or equal to 175 mm in the transverse direction (y).

7. An engine according to any one of the preceding claims, wherein The passage includes an oil pre-separator upstream of the pump.

8. The engine according to claim 7, wherein: The oil pre-separator is mounted adjacent to the engine structure (eg, the gearbox).

9. An engine according to any one of the preceding claims, wherein The passage extends between the pump and an aperture in the gearbox.

10. The engine according to claim 9, wherein The aperture is located in a forward facing wall of the gear case.

11. An engine according to claim 9 or claim 10, wherein: The aperture is located above a cam gear mounted to a camshaft of an engine.

12. An engine according to any one of claims 9 to 11, wherein The passage terminates in an oil pre-separator located within the gearbox.

13. The engine according to claim 12, wherein: The pre-separator includes an extraction duct defining a mouth for extracting gas from the gearbox, and a plate axially spaced from and covering the opening of the extraction duct.

14. The engine according to claim 13, wherein: The plate includes an angled portion arranged to extend from an axially spaced position and terminate at an edge, the edge being at least axially aligned with or axially overlapping the mouth, and the edge being laterally spaced from the mouth, optionally wherein the plate includes a flat portion covering the mouth, and the angled portion extends around the periphery of the flat portion.

15. An engine according to claim 13 or claim 14, wherein The mouth terminates in an outwardly turned lip.

16. An engine according to any one of claims 12 to 15, wherein The pre-separator includes a flow diverter extending around at least a portion of the extraction conduit to divert oil flowing down the wall of the gearbox away from the opening of the extraction conduit.

17. An engine according to any one of the preceding claims, wherein The pump inlet faces laterally outward.

18. An engine according to any one of the preceding claims, wherein The pump includes an impeller and an impeller rotation axis, which is arranged substantially in the longitudinal direction of the engine.

19. An engine according to any one of the preceding claims, wherein The pump is a side channel pump.

20. The engine of claim 19, wherein: The pump comprises first and second inlets with corresponding first and second vortex generators immediately upstream of the first and second inlets, and / or the pump comprises a substantially right-angled flow turn in the conduit immediately upstream of the inlets.

21. The engine according to claim 20, wherein The vortex generator is located at an end of the passage.

22. An engine according to any preceding claim, further comprising an oil separator in fluid flow communication with and downstream of the pump.

23. The engine of claim 22, wherein: The oil separator is located longitudinally between the forward-facing wall of the gearbox and the pump; optionally, wherein the longitudinal dimension of the spatial extent occupied by the pump and the oil separator is less than or equal to 200 mm.

24. An engine according to claim 22 or claim 23, wherein The oil separator comprises a gas outlet, and wherein a conduit extends from the gas outlet to a separate chamber in the gearbox.

25. An engine according to any one of claims 22 to 24, wherein The oil separator further comprises an oil outlet, and wherein a conduit extends from the oil outlet back to the crankcase or the gearbox.

26. An engine according to any one of the preceding claims, wherein The pump is a self-contained unit having a drive motor, for example an electric drive motor.

27. An engine according to any one of the preceding claims, wherein The gaseous fuel is hydrogen.

28. An internal combustion engine operable in a selected one of a first configuration as a gaseous fuel, such as a hydrogen powered engine, and a second configuration as a liquid fuel, such as a diesel or gasoline powered engine, according to any one of the preceding claims, wherein In the second configuration, instead of a pump for discharging exhaust gases including ventilation gases and blow-by gases from the crankcase, a fuel injection pump is mounted adjacent to the engine structure in the space otherwise occupied by the pump for delivering exhaust gases.

29. The engine of claim 28, wherein An aperture is provided in the wall of the gearbox for connecting a conduit to the pump for conveying blow-by gases in the first configuration and for driving from the gearbox to the fuel injection pump in the second configuration.

30. An oil pre-separator for installation in an oil and gas containing chamber of an internal combustion engine, the pre-separator comprising: an extraction conduit defining a mouth for extracting gas from the chamber through a wall of the chamber; and a plate axially spaced from and covering the mouth.

31. The pre-separator according to claim 30, wherein The plate includes an angled portion arranged to extend from an axially spaced position and terminate at an edge, the edge being at least axially aligned with or axially overlapping the mouth, and the edge being laterally spaced from the mouth, optionally wherein the plate includes a flat portion covering the mouth, and the angled portion extends around the periphery of the flat portion.

32. A pre-separator according to claim 30 or claim 31, wherein The mouth terminates in an outwardly turned lip.

33. A pre-separator according to any one of claims 30 to 32, wherein The pre-separator includes a flow diverter extending around at least a portion of the extraction conduit to divert oil flowing down the wall of the chamber away from the mouth of the extraction conduit.

34. A pre-separator according to any one of claims 30 to 33, wherein The ratio between the diameter or minimum width of the plate and the diameter of the extraction conduit is between about 4:1 and 2.5:1, for example about 3:

1.

35. The pre-separator according to claim 33 or 34, wherein The angled portion of the plate terminates at an axial spacing of approximately 5-6 mm from an adjacent wall, such as a wall of the diverter.

36. The pre-separator according to claim 35, wherein The outwardly turned lip has a greater spacing from the corresponding wall than the angled portion, for example at least 8 mm.

37. A pre-separator according to any one of claims 30 to 35, wherein The outwardly turned lip protrudes laterally by at least 2 mm, for example 4 mm.

38. An oil pre-separator for installation in an oil and gas containing chamber of a hydrogen powered internal combustion engine, the pre-separator comprising an extraction conduit defining a mouth for extracting exhaust gas from the chamber and a baffle arrangement, the pre-separator optionally being configured to reduce the oil concentration in the exhaust gas by at least 2.5 times, preferably by at least 4 times, at a flow rate of at least 30 l / min per liter of displacement of the internal combustion engine.

39. An oil separation system for installation in an outflow path of exhaust gas from a crankcase ventilation system of a hydrogen internal combustion engine, the oil separation system comprising an oil pre-separator according to any one of claims 30 to 38 and a cyclonic oil separator located downstream of the pre-separator.

40. The oil separation system according to claim 39, wherein: The pre-separator and the separator reduce oil carryover in the exhaust gas flow path downstream of the separator to less than or equal to 1 g / hr of engine operation, optionally less than or equal to 0.5 g / hr of engine operation.

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