Internal combustion engine

Abstract

A gas fuelled internal combustion engine comprising an engine structure defining one or more cylinders; a piston mounted for reciprocating motion in the or each of the one or more cylinders; a crankcase; a gas pressure source configured to transport gas along a ventilation path to remove blow-by from the crankcase; wherein the ventilation path comprises at least one ventilation passage having an opening proximate a lowest extent of the one or more cylinders.

Description

[0001] INTERNAL COMBUSTION ENGINE

[0002] FIELD

[0003] The present teachings relate to an internal combustion engine. In particular, the present teachings relate to a gas fuelled internal combustion engine, such as those powered by hydrogen.

[0004] BACKGROUND

[0005] In order to reduce emissions from internal combustion engines, as well as potentially to reduce greenhouse gases, hydrogen is being proposed as an alternative to diesel or gasoline as a fuel for such engines. In addition, other gas fuels, such as compressed natural gas, are known as fuels for internal combustion engines and may provide environmental benefits over liquid fuels such as diesel and gasoline.

[0006] In internal combustion engines, it is common for air and fuel in the combustion chamber of a cylinder, as well as combustion gases formed in the combustion chamber, to leak to a degree from the combustion chamber past the piston and into the engine's crankcase. The leaking gases are commonly known as blow-by gases.

[0007] In engines powered by a gas fuel such as hydrogen, accumulation of the gas fuel component of the blow-by gases in the crankcase can pose a problem if not adequately ventilated. This is due to the relatively high flammable range of some gas fuels (e.g. hydrogen is flammable in air in concentrations of between 4 and 75%). Unless the blowby gases are ventilated such that the concentration of gas fuel in the crankcase is below its lower flammability limit, there is a risk that the gas fuel in the crankcase could ignite, potentially damaging the engine and its surroundings. It is also possible for the gas fuel to then ignite the lubricating oil in the crankcase, causing further combustion to occur.

[0008] Crankcase ventilation systems are known to be configured to ventilate blow-by gases from the crankcase of gas fuel internal combustion engines. Typically, such systems provide a flow path for the blow-by gases to rise from the crankcase and through the engine, to an outlet at an upper portion of the engine such as a cylinder head or rocker cover. The blowby gases rise due to their high temperature but may also be naturally buoyant when the gas fuel has a lower density than air (e.g. hydrogen).

[0009] There may, however, be locations in engines where blow-by gases may accumulate and may not readily be diluted by the ventilation system, leading to an elevated risk of combustion in the crankcase. This risk may be greater in higher specific output engines due to greater blow-by gas generation, and longer engines - such as inline six-cylinder or eight-cylinder engines - where the ventilation path within the engine may be longer and dilution may therefore be less effective.

[0010] The present teachings seek to overcome or at least mitigate the problems of the prior art.

[0011] SUMMARY

[0012] A first aspect of the present teachings provides a gas fuelled internal combustion engine comprising an engine structure defining one or more cylinders; a piston mounted for reciprocating motion in the or each of the one or more cylinders; a crankcase; a gas pressure source configured to transport gas along a ventilation path to remove blow-by from the crankcase; wherein the ventilation path comprises at least one ventilation passage having an opening proximate a lowest extent of the one or more cylinders.

[0013] Advantageously, this arrangement allows ventilation gas to be introduced into the crankcase in the region where blow-by gas first enters the crankcase, thereby diluting it where it is generated such that the ventilation gas is less likely to reach its lower flammability limit.

[0014] Optionally, the opening is at substantially the same level as the lowest extent of the one or more cylinders.

[0015] Advantageously, this ensures that the ventilating gas is delivered directly where it will dilute blow-by gases as they exit the cylinder.

[0016] Optionally, the engine structure comprises a plurality of cylinders.

[0017] Optionally, at least two of the plurality of cylinders are provided with corresponding ventilation passages having openings proximate the lowest extent of the corresponding cylinders.

[0018] Advantageously, by providing multiple passages on multi-cylinder engines, the risk of gaseous fuel reaching its ignition concentration is further reduced.

[0019] Optionally, the engine further comprises a manifold arranged to connect the at least two ventilation passages. Advantageously, providing a manifold provides a convenient way of constructing a ventilation path that ensures the flow of ventilation gas to or from the crankcase in multiple locations.

[0020] Optionally, the manifold extends longitudinally along the engine.

[0021] Advantageously, this allows the manifold to be relatively short with respect to the passages to be connected and to be simple to manufacture.

[0022] Optionally, the manifold is integral with the engine structure.

[0023] By integral we mean the rail is formed unitarily with the engine structure - e.g. as part of the same cast structure as the engine structure in embodiments where the structure is cast. Advantageously, this may simplify the assembly of the ventilation system and reduce the risk of leaks.

[0024] The manifold may be provided in a side wall of the engine structure, e.g. in a side wall of the cylinder block or crankcase.

[0025] Optionally, the manifold is a linear rail provided within the engine structure.

[0026] Advantageously, this may simplify the inclusion of the manifold by allowing it to be formed as a cast structure with a suitable core or a linear machined feature.

[0027] Optionally, the engine further comprises a gearcase and a further ventilation passage connects the ventilation path to the gear case.

[0028] Advantageously, by providing this additional passage, any gas fuel in the gearcase is able to be diluted, reducing the risk of combustion.

[0029] Optionally, the further ventilation passage connects the gearcase to the manifold.

[0030] Advantageously, this may further simplify assembly.

[0031] Optionally, the further ventilation passage connects to an upper part of the gear case. Advantageously, for gas fuels which are lighter than air, providing the ventilation passage in this location ensures that a high concentration of fuel is not trapped within the gear case.

[0032] Optionally, the at least two cylinders are arranged in line.

[0033] Optionally, a wall extends downwardly intermediate two cylinders from a bottom of the cylinders towards a crankshaft journal bearing seat, thereby separating an under piston area of the crankcase into two separate bays.

[0034] Advantageously, such an arrangement assists in supporting the crank shaft by reacting transverse loadings during running of the engine.

[0035] Optionally, an aperture is provided in the wall.

[0036] Advantageously, this allows ventilation gas to flow longitudinally along the engine from one bay to another whilst retaining the strength of the wall.

[0037] Optionally, the gas pressure source is a pump.

[0038] Optionally, the gas pressure source is configured to draw ventilation gas into the crankcase via the one or more ventilation passages.

[0039] Optionally, at least one of the one or more ventilation passages comprises a nozzle mounted thereto and arranged to direct ventilation gas towards an underside of a piston adjacent thereto.

[0040] Advantageously this may assist in diluting blow-by gases that may be accumulating within space at the underside of the piston.

[0041] Optionally, the or each cylinder has a displacement in a range of 0.75 and 1.5 litres.

[0042] Optionally, the engine having a maximum power output in a range of lOkW to 35kW per cylinder, optionally 12kW to 33kW per cylinder.

[0043] Optionally, the engine is a hydrogen powered engine and comprises a hydrogen fuel delivery system. Optionally the engine may be fuelled solely by hydrogen, or by hydrogen in combination with other fuels, such as compressed natural gas. Optionally, the engine further comprises an air inlet passage upstream of the cylinder and the hydrogen fuel delivery system injects hydrogen into the inlet passage.

[0044] Optionally, the hydrogen fuel delivery system injects hydrogen directly into the cylinder.

[0045] Optionally, the engine further comprises a nozzle arranged to direct a jet of oil towards the underside of the or each piston, optionally wherein the nozzle arranged to direct a jet of oil is located on the opposite side of the cylinder from the at least one ventilation passage.

[0046] Advantageously this may improve the cooling of the engine, and if located away from the ventilation passage, may minimise the mist of oil that may be generated, and thus oil carry-over that may need to be dealt with.

[0047] A second aspect of the teachings provides a working machine or genset comprising an internal combustion engine of the first aspect and a fuel tank storing a gaseous fuel such as hydrogen, the fuel tank being in fluid flow communication with a fuel delivery system.

[0048] A third aspect of the teachings provides an engine structure defining a plurality of adjacent cylinders; each of the cylinders being arranged to receive a corresponding piston; a crankcase; a wall extending downwardly intermediate two adjacent cylinders from a bottom of the cylinders towards a crankshaft journal bearing seat for receiving a crankshaft, the wall thereby separating an under piston area of the crankcase into two separate bays; wherein an aperture is provided in the wall to permit fluid communication between the bays.

[0049] Advantageously this permits a longitudinal flow of blow-by gases to occur from one bay to the next, reducing the risk of concentrated pockets of blow-by gases being generated in the bays, particularly if the blow-by gas is buoyant, for example is hydrogen.

[0050] Optionally, the aperture is above a midpoint of the crankshaft bearing journal.

[0051] Advantageously, this location further reduces the risk of pockets of concentrated blow-by gas being generated.

[0052] Optionally, the aperture is closer to the bottom of the cylinders than to the midpoint of the crankshaft journal bearing. The third aspect of the teachings may further comprise the optional features of the first aspect of the teachings.

[0053] Advantageously, this location further reduces the risk of pockets of concentrated blow-by gas being generated.

[0054] A further aspect of the present teachings provides a gas fuelled internal combustion engine comprising: an engine structure defining one or more cylinders; a piston mounted for reciprocating motion in the or each of the one or more cylinders; a crankcase; a gas pressure source configured to transport gas along a ventilation path to remove blowby from the crankcase; wherein the ventilation path comprises at least two discrete openings to permit the entry of ventilation gas directly into the crankcase or at least two discrete openings to permit the exit of expelled gas directly from the crankcase.

[0055] Advantageously, this reduces the risk of high concentrations of gas fuel accumulating in particular locations where it may reach its lower flammability limit.

[0056] The openings may be spaced longitudinally along the engine.

[0057] Advantageously, this may further limit high concentrations of gas fuel accumulating, in particular for inline eight, six and four cylinder engines, where uniform dilution along the length of the engine may otherwise be difficult to achieve.

[0058] The openings may be connected to a common manifold.

[0059] Advantageously, providing a manifold provides a convenient way of constructing a ventilation path that ensures the flow of ventilation gas to or from the crankcase in multiple locations.

[0060] The gas fuelled engine may further comprise a gearcase and the ventilation path may further comprise a separate opening to permit the entry of ventilation gas into the gearcase.

[0061] Advantageously, by providing this additional passage, any gas fuel in the gearcase is able to be diluted, reducing the risk of combustion. The gas fuelled engine may further comprise a rocker cover and the ventilation path may further comprise a separate opening to permit entry of ventilation gas to the rocker cover.

[0062] The gas fuelled engine may further comprise a rocker cover and the ventilation path may further comprise a separate opening to permit the exit of expelled gas from the rocker cover.

[0063] BRIEF DESCRIPTION OF DRAWINGS

[0064] Embodiments are now disclosed by way of example only with reference to the drawings, in which:

[0065] Figure 1 is a schematic view of a gas fuelled internal combustion engine according to an embodiment of the present teachings;

[0066] Figure 2 is a perspective view of the gas fuelled internal combustion engine of Figure 1 with various ancillary components removed;

[0067] Figure 3 is a reverse perspective view of a cylinder block of the internal combustion engine of Figure 2;

[0068] Figures 4 and 5 are perspective and side cross-sectional views of the cylinder block shown in Figure 3 on the inclined plane W-W;

[0069] Figure 6 is a cross-sectional view of the cylinder block shown in Figure 3 vertically on the plane Y-Y;

[0070] Figure 7 is an underside view of the cylinder block of Figure 3;

[0071] Figure 8 is a perspective view of a gas fuelled internal combustion engine of a second embodiment with various ancillary components removed;

[0072] Figure 9 is a perspective view of a cylinder block of the internal combustion engine of Figure 8;

[0073] Figure 10 is an enlarged view of a portion A of the cylinder block of Figure 9;

[0074] Figure 11 is a perspective view of an underside of the cylinder block of Figure 9;

[0075] Figure 12 is a cross-section on the plane Z-Z of Figure 9; and

[0076] Figure 13 is a side view of an exemplary working machine incorporating an internal combustion engine of Figure 1. DETAILED DESCRIPTION

[0077] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of various embodiments and the inventive concept. However, those skilled in the art will understand that: the present teachings may be practiced without these specific details or with known equivalents of these specific details; that the present teachings is not limited to the described embodiments; and, that the present teachings may be practiced in a variety of alternative embodiments. It will also be appreciated that well known methods, procedures, components, and systems may not have been described in detail.

[0078] Referring firstly to Figures 1 to 7, an embodiment includes an internal combustion engine 100.

[0079] The engine 100 is a four-stroke gas fuelled IC engine configured to be powered by hydrogen, hereafter referred to as a hydrogen fuelled IC engine.

[0080] The engine 100 may be suitable for use as the prime mover in a working machine 10 - see Figure 13 which depicts a backhoe loader - but may also be a telescopic handler, a forklift truck, a wheeled loading shovel, a dumper, an excavator or a tractor, for example. Such working machines 10 are suitable for use in off-highway applications such as agriculture, forestry and construction. In these industries they are generally configured to perform tasks such as excavation, load handling, harvesting or planting crops. The engine 100 may also be utilised in a genset - a self-contained unit to provide electrical power at off-grid locations.

[0081] As such the engine 100 is typically required to have certain characteristics such as a high torque output over a wide engine speed band, with peak torque occurring at a relatively low engine speed, which differ from light passenger vehicles, for example. In off-highway applications, this provides "torque backup" that enables working machines 10 to continue to carry out working operations when encountering increased loads, or resistance to a working operation - e.g. an excavator encountering a particularly solid piece of earth to be excavated.

[0082] In this embodiment, the engine 100 has four cylinders 112. As configured the engine has a maximum power output of around 129kW, although it will be appreciated that the present teachings are applicable to engines with a wide range of power outputs. In the present embodiment the engine has a total displacement of 4.8 litres (i.e. 1.2 litres per cylinder). In engines used in off-highway applications each cylinder may typically have a displacement of between 0.75 and 1.5 litres. Such a displacement is relatively high by comparison with passenger vehicle engines, but is suited to providing the operating characteristics described above.

[0083] In this embodiment the engine 100 is fuelled solely by hydrogen. In other embodiments, the engine 100 may be fuelled by hydrogen in combination with other fuels, such as natural gas.

[0084] The engine 100 includes an engine structure 102. The engine structure 102 comprises fixed components arranged to absorb and withstand the major stresses generated by the engine principally from the combustion of hydrogen and loads generated by motion of the piston, crankshaft, camshaft, and valvetrain. The engine structure 102 is also used to mount ancillary engine components such as pumps, turbochargers etc. thereto. The engine structure 102 comprises, in this embodiment a crankcase 104, a cylinder head 106, a cylinder block 108, and a gearcase 109.

[0085] The cylinder block 108 includes one or more cylinders 112; four in the present embodiment (see Figure 3). The cylinder head 106 is mounted to the cylinder block 108 so as to be coupled to the one or more cylinders 112. The cylinder head 106 includes one or more inlet 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 this embodiment the engine includes a hydrogen fuel delivery system by which hydrogen fuel may be directly injected into each cylinder 112 from a pressurised fuel tank 12 (Figure 13). The rated pressure of the fuel tank 12 is typically in excess of 35MPa and the hydrogen pressure may be stepped down before being introduced into the cylinders 112.

[0086] In other embodiments, the engine 100 is a port fuel injection (PFI) engine, and the one or more inlet ports also supply hydrogen fuel to each cylinder 112.

[0087] In alternative embodiments (not shown), the engine 100 may have more or fewer cylinder assemblies 19, e.g. 2, 3, 6, or 8. In addition, in other embodiments the cylinders 112 may be oriented in a "V" or boxer configuration rather than inline as in the disclosed embodiment.

[0088] The engine 100 includes a valvetrain (not shown) including a camshaft (not shown), and rocker arms (not shown) arranged to open and close inlet and outlet valves (not shown) as is well known. The camshaft is mounted to the cylinder block 108. The rocker arms are mounted to the cylinder head 106. Motion of the camshaft is transferred to the rocker arms via pushrods (not shown) extending between the cylinder block 108 and the cylinder head 106. The rocker cover 107 is mounted to the cylinder head 106 and houses the rocker arms. Each cylinder 112 receives a piston 113, which is translationally movable within the cylinder 112. The space enclosed by the cylinder 112, piston 113 and cylinder head 106 defines a combustion chamber 126. During operation of the engine 100, translational movement of each piston 113 is converted into rotational movement of a crankshaft 111. The crankcase 104 houses the crankshaft 111.

[0089] The gearcase 109 is mounted to one or both of the cylinder block 108 and the crankcase 104. The gearcase 109 projects laterally from said one or both of the cylinder block 108 and the crankcase 104. The gearcase 109 houses a gear assembly (not shown) configured to transmit rotary motion of the crankshaft to the camshaft for operation of the rocker arms. The gearcase 109 is in fluid communication with the crankcase 104.

[0090] With reference in particular to Figures 2 and 3 at least the cylinder head 106, cylinder block 108, gear case 109 and crankcase 104 of the engine structure 102 of the engine 100 of this embodiment are components manufactured by casting of metal.

[0091] In this embodiment, the cylinder block 108 and crankcase 104 are partially integrated. Specifically, the engine is of the bedplate type in which an upper portion 104a of the crankcase 104 is cast integrally and monolithically with the cylinder block 108. A lower portion 104b is manufactured as a separate casting, with the joint between the upper and lower portions 104a, 104b being at the midpoint of the crankshaft bearing journals. In other embodiments the cylinder block 108 and the crankcase 104 are a wholly single casting (not shown), i.e. as a single integral and monolithic material, or as two or more wholly separate castings (not shown). In these cases, separate bearing caps may be used to mount the crankshaft to the crankcase.

[0092] The cylinder head 106 is manufactured as a separate casting in this embodiment. In other embodiments the cylinder block and crankcase may be separate components and / or the cylinder block may be integrally cast with the cylinder head. The gearcase 109 is manufactured as two separate castings, which are themselves distinct from the crankcase 104 and cylinder block 108.

[0093] With further reference to Figure 1, the engine 100 includes an intake system 115 configured to supply air to the 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 the respective inlet ports.

[0094] With further reference to Figure 1, the intake system 115 includes an intake passage 140 (represented by a solid double line in Figure 1) arranged to transport air from an air filter 118 upstream to the cylinders 112 downstream. The cylinder head 106 is mounted to the cylinder block 108. An intake manifold (not shown) forming part of the intake passage 140 is mounted to the cylinder head 106.

[0095] As the engine 100 utilises hydrogen as fuel, a spark is required to initiate combustion. Thus, each cylinder 112 has a spark plug (not shown).

[0096] During operation of the engine 100, some of the gas fuel and air introduced into each cylinder 112, as well as combustion gases formed within the cylinder 112, flow out of the combustion chamber past the piston 113 and into the crankcase 104 following the path indicated by arrow 105 as "blow-by" gas.

[0097] The engine 100 includes a ventilation system 110 configured to ventilate the blow-by gas from the crankcase 104.

[0098] Figure 1 shows a simplified diagram of the ventilation system 110 according to an embodiment. The ventilation system 110 comprises a ventilation path 116 (indicated by a dash-dot line in Figure 1) to transport ventilation gas (air in this embodiment) from a ventilation path inlet from the air intake system 115 to the crankcase 104 so as to dilute the concentration of blow-by gas in the crankcase 104. This portion of the ventilation path 116 is referred to as an inflow portion 125, being upstream of the crankcase 104. The wording "ventilation gas" is used to differentiate from air supplied to the one or more cylinders 112 for combustion.

[0099] In this embodiment, the ventilation system 110 is configured to draw air as the ventilation gas into the ventilation path 116 from the intake passage 140 at a first location 140a which defines the ventilation path inlet.

[0100] The ventilation system 110 is further configured to transport the diluted blow-by gas 105 from the crankcase 104 (hereinafter "expelled gas") via the ventilation path 116 to an outlet. This portion of the ventilation path 116 is referred to as the outflow portion 126, being downstream of the crankcase 104 and gearcase 109.

[0101] In this embodiment, the ventilation system 110 is configured to exhaust the expelled gas from the crankcase 104 to a second location 140b of the intake passage 140 which defines a ventilation path outlet. The second location 140b is downstream of the first location 140a with respect to the intake passage 140.

[0102] The ventilation system 110 further includes a gas pressure source 114 within the ventilation path 116. The gas pressure source 114 is configured to transport ventilation gas along the inflow portion 125 of the ventilation path 116 from the first location 140a to a location proximate the bottom of the cylinder, i.e. proximate a lowest extent of the piston 113 during its reciprocating motion.

[0103] The gas pressure source 114 is further configured to transport a combination of the ventilation gas and the blow-by gas 105, which includes the gas fuel, from the crankcase

[0104] 104 and gearcase 109 and along the outflow portion 126 of the ventilation path 116 to the section location 140b as expelled gas.

[0105] It will be appreciated that the flowrate of expelled gas out of the crankcase 104 in the outflow portion 126 of the ventilation path 116 is substantially equal to the sum of the flowrate of blow-by gas entering the crankcase past the piston 113 as indicated by arrow

[0106] 105 and the ventilation gas entering the into the crankcase 104 via the inflow portion 125. The flowrate of expelled gas is significantly higher than is usual in a comparable diesel engine. For example the flowrate of expelled gas may be in excess of 30 litres per minute, per litre of engine displacement, potentially in excess of 60 litres per minute, per litre of engine displacement when operating at its maximum flow rate (which is typically when the engine operates at its maximum load).

[0107] In the illustrated embodiment, the gas pressure source 114 is a pump 114 or 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.

[0108] In the illustrated embodiment, the pump 114 is arranged downstream of the crankcase 104 in the outflow portion 126 of the ventilation path 116 and thus induces a below- atmospheric pressure in the crankcase 104.

[0109] In alternative embodiments (not shown), the pump 114 or other gas pressure source may be configured to induce an above-atmospheric pressure in the crankcase 104. For example, the pump 114 may be arranged upstream of the crankcase 104 in the inflow portion 125 of the ventilation path 126.

[0110] In alternative embodiments the ventilation path and / or direction may be changed.

[0111] With reference to Figure 1, 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. The controller 150 may comprise any suitable circuitry to achieve control of pump 114 and follow the control methods described herein. The controller may comprise: 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 single or multi-processor architectures; and / or sequential / parallel architectures; and / or at least one programmable logic controllers (PLCs); 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 an associated memory or the memory may be located locally to the controller or remotely. The memory may be a non-volatile flash memory.

[0112] In this embodiment, the controller 150 is configured to control the pump 114 based on the one or more determined operating parameters via a look-up table or a map stored in the memory. The look-up table incorporates a suitable number of values in a matrix of load, engine speed and corresponding setpoint flowrate. The controller 150 may be configured to interpolate to obtain setpoint flowrates for intermediate values of engine load and engine speed.

[0113] Where the determined operating parameters are engine speed and engine torque, these may be determined or obtained by the engine ECU for the operation of the engine 100 and supplied to the controller 150 via a signal line 152 (e.g. a CAN bus line as shown in Figure 1).

[0114] In alternative embodiments (not shown), the controller 150 may be configured to control the pump 114 via any suitable means, such as via a physics-based model of the engine 100 for example, or by directly sensing the concentration of hydrogen in the crankcase 104 or the outflow portion. In other embodiments the pump may be fixed speed or the pump may have a fixed relationship to engine speed, for example.

[0115] 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 a speed of the electric motor, and therefore the pump 114, based on the one or more determined operating parameters. For example, in embodiments in which the pump 150 includes a revolving element, such as an impeller, to pump fluid, the controller 150 may be configured to control the rotational speed of the revolving element by providing suitable control signals to the electric motor based on the impeller speed required to achieve a particular setpoint flowrate and the gear ratio (if any) between the electric motor and the impeller. The setpoint flowrate in turn is determined so as to maintain the hydrogen concentration below a certain predetermined level for the prevailing engine 100 operating parameters.

[0116] In alternative embodiments (not shown), the controller 150 may be configured to additionally or alternatively control an output of the pump 114 by mechanisms other than by adjusting pump speed. For example, the controller 150 may be configured to control a position of one or more rotational vanes or blades within the pump 114, or a position of an output valve of the pump 114. In such embodiments, the pump 114 may not be a variable speed pump.

[0117] Referring now in particular to Figures 4 to 7, a portion of the ventilation path 116 within the engine structure 102 is discussed in more detail. The ventilation path 116 of this embodiment provides multiple inlets into the crankcase 104.

[0118] In this embodiment, the ventilation gas enters the side of the engine block 108 via a suitable interface such as a spigot 160. The spigot may be cast integrally with the engine structure 102, or be connected by welding, swaging etc.. The spigot 160 is in communication with a manifold 162 in the form of a rail, which runs longitudinally within the engine block above the upper portion 104a of the crankcase 104. The manifold 162 is isolated from oil galleries 163 within the structure 102 which allows oil to flow from the cylinder head down into the crankcase 104, and is also isolated from cooling galleries (not shown) in the engine 100 through which coolant (not shown) flows before circulating to a heat exchanger (not shown), as is well known.

[0119] A plurality of ventilation passages 164 extend generally downwardly from the manifold 162 and terminate with an opening within the upper portion of the crankcase 104a to define ventilation gas inlets. The ventilation passages 164 allow the ventilation gas to be distributed from the manifold 162 into an interior space 165 of the crankcase 104.

[0120] The manifold 162 and ventilation passages 164 are formed using cores in the casting in this embodiment. In other embodiments, the manifold 162 and / or ventilation passages 164 may be formed by machining the casting, or by a combination of cores and machining. In alternative embodiments the manifold may be separate from the engine structure 102, and may for example be a rail or other vessel mounted to an exterior of the cylinder block 108 or crankcase 104.

[0121] As can be seen most clearly in Figures 6 and 7, a lowermost extent of each of the cylinders 112 is defined by a generally downwardly facing, generally horizontal wall 166. This wall 166 also defines the boundary between the cylinder block 108 and the upper portion of the crankcase 104a. It further represents the approximate lowest extent of motion of each piston 113 during operation of the engine 100 (the skirt of the pistons may be exposed to some extent below the wall at bottom dead centre). As such, any blow-by gases 105 that are able to pass between the pistons 113 and the wall of the cylinder 112 first enter the crankcase 104 proximate the bottom of the cylinder 112 adjacent the horizontal wall 166, and therefore adjacent openings of the ventilation passages 164.

[0122] It can be seen that in this embodiment one ventilation passage is provided for cylinder one (at the front of the engine 100) and two ventilation passages are provided for each of cylinders two, three and four. This is due other features of the structure 102 resulting in a lack of space being available for a further passage 164 for cylinder one 112. However, in this embodiment the ventilation passage 164 for cylinder one has twice the cross sectional area of the ventilation passages for cylinders two, three and four such that their flow of ventilation gas from each is substantially equal. In other embodiments the number of ventilation passages 164 for each cylinder 112 may be equal, e.g. with two or one provided for all cylinders 112, or adjusted as required.

[0123] In addition, a rear end 168 of the manifold 162, is in fluid communication with the interior of the gear case 109 such that ventilation gas may flow from the manifold 162 into the gear case and dilute any blow-by gases 105 that may have entered the gearcase 109. An advantage of the location of the manifold 162 is that it can enter the gear case 109 proximate an upper end thereof so that buoyant blow-by gases 105 (in particular hydrogen) are diluted fully within the gear case.

[0124] The manifold 162 provides a location for the mounting of a burst disc 176 at port in the side of the engine that may be an alternative pipe connection point of the inflow portion 125. The burst disc 176 may be used as a preferential pressure relief location in the event combustion of the blow-by gas does occur, to minimise the risk of other parts of the engine being damaged.

[0125] A generally U-shaped nozzle 178 forming part of a separate oil circulation system of the engine 100 is mounted to a port in the wall 166 adjacent each cylinder 112 and directs a jet of oil towards the underside of each piston 113 to cool the pistons. These nozzles 178 are located on the opposite side of the cylinder 112 from the ventilation passages 164. This may be beneficial as the spacing reduces the risk of the ventilation gas creating an oil mist by impinging on the oil jet. In turn, this may reduce the amount of oil carry-over in the expelled gas that may then require separation before the expelled gas is introduced into the inlet passage 140.

[0126] Referring to Figures 4 and 6 it can be seen that walls 170 extend downwardly from the bottom of the cylinder block 108 between adjacent cylinders 112 into the upper crankshaft region 104a parallel to axis Y, forming discrete bays corresponding to each cylinder. These walls 170 are part of the casting of the upper crankshaft region 104a and define a seat 172 of a crankshaft journal bearing at their lowest extent. As such they support the crankshaft 111 during operation of the engine 100 when eccentric loads are imposed on it due to the reciprocating motion of the pistons 113. The other seat is provided by the lower portion 104b of the crankcase 104.

[0127] However, such walls 170 may restrict the circulation of the ventilation gas and allow concentrated pockets of blow-by gas 105 to form. Therefore, in this embodiment, apertures 174 are provided in the walls 170 to aid circulation of the ventilation gas along the crankcase parallel to axis X. In this embodiment three apertures 174 are provided in each wall, but it will be appreciated that the number, size, shape and position may be adjusted in other embodiments to retain the strength of the wall, whilst permitting a suitable amount of flow of gas.

[0128] In the present embodiment the apertures 174 are cast into the walls 170, but in other embodiments, may instead be machined into a wall that is an uninterrupted casting.

[0129] In this embodiment, when the ventilation system is operating, the pump 114 draws air as the ventilation gas from the air intake passage 140 at point 140a, along the inflow portion 125 of the ventilation path 116 into the manifold 162, where it flows into the crankcase 104 interior space 165 through the ventilation passages 164. Blow-by gases 105 entering the crankcase interior 165 are thereby diluted upon entry and can be maintained below the lower flammability limit. In addition, the ventilation gas is introduced into the gearcase 109 via the rear end 168 of the manifold 162 and dilutes any blow-by gases 105 that may otherwise accumulate there. In this embodiment, the pump 114 withdraws the expelled gas from the rocker cover 107 at the top of the engine having passed from the crankcase up through the oil drain galleries 163 and into the rocker cover. The expelled gas is reintroduced into the air intake passage at point 140b, downstream of point 140a.

[0130] This configuration of the ventilation system 110 dilutes and flushes hydrogen and / or other gas fuels from substantially all parts of the engine 100, counteracting the tendency of hydrogen or other gas fuels to accumulate in pockets of high concentration such as under the piston and / or at the top of the engine (assuming it is installed in a normal upright orientation) due to its natural buoyancy. It also generates a negative pressure within the crankcase 104 and other internal spaces of the engine 100.

[0131] However, in other embodiments, the flow direction may be reversed, such that expelled gases are withdrawn from the crankcase 104 via the ventilation passages 164 and the manifold 162, with ventilation gas having been introduced elsewhere into the engine 100 (e.g. the rocker cover 107) and / or a positive pressure may be generated in the crankcase 104. Further, instead of connecting an external pipe to the spigot 160, a passage may be formed in the engine structure 102 that connects to the manifold 162 and enables a shorter run of pipe to be used from the air intake passage 140.

[0132] Figures 8 to 12 illustrate a second embodiment of the present teachings. Similar features in this embodiment are denoted by the same reference numerals, but with the prefix "2" rather than "1". Only differences between the two embodiments are discussed in detail.

[0133] The engine 200 of this embodiment has six cylinders inline, but is of the same basic construction as the engine 200.

[0134] In this embodiment a manifold 262 external to the engine 100 and illustrated schematically in Figure 8 supplies the ventilation gas to three locations, these being into the rocker cover 207 at the top of the engine, and to ventilation passages 264 at two locations proximate the lowermost extent of two of the cylinders 212. The first ventilation passage 264 is at the front of the upper crankcase portion 204a adjacent to cylinder one 212and the second ventilation passage 264 re-purposes an existing turbo oil drain port that enters the upper crankcase portion proximate to cylinder two 212 at the side of the engine 200.

[0135] As can be seen from Figures 11 and 12 apertures 274 are provided in the walls 170 between cylinders in a similar way to the first embodiment. However in this embodiment the apertures 274 have been machined from below at an angle after casting as an adaptation of an existing engine structure 202.

[0136] The expelled gas is removed from a gearcase (not shown) at the rear of the engine 100.

[0137] The combination of the inlets and outlet in these locations, and the apertures 274 in the wall allows the ventilation gas to flow from front to back of the engine under each of the cylinders 212 without blow-by gas 105 accumulating in the under-piston locations. In addition, introducing ventilation gas at the top of the rocker cover 207 dilutes any blowby gas accumulating in pockets at the top of the engine 200 and the outlet in the gearcase draws the ventilation gas downwardly and towards the rear of the engine 200 where it meets the ventilation gas introduced through the ventilation passages 264.

[0138] In addition, by utilising a CCV system 110, 210 that adjusts the rate of ventilation in accordance with the amount of blow-by hydrogen being generated, as described above, it is ensured that the concentration of gas fuel stays low across all operating conditions of the engine. In this embodiment the ventilation system is configured to maintain a hydrogen concentration below 4%, optionally below 3%, for example below 2% - i.e. below the lower flammability limit thereof. The one or more embodiments are described above by way of example only and it will be appreciated that the variations are possible without departing from the scope of protection afforded by the appended claims. For example, whilst near vertical ventilation passages 164 are shown in the first embodiment, it will be appreciated that in other embodiments the openings to the passages may be directed in other orientations, such as at or near horizontal and the location of the manifold may be adjusted accordingly. In some embodiments a nozzle may be fitted to the passages 164, 264 in the engine structure to extend the passages, e.g. to direct ventilation gas to blow upwardly under the pistons.

Claims

Claims1. A gas fuelled internal combustion engine comprising: an engine structure defining one or more cylinders; a piston mounted for reciprocating motion in the or each of the one or more cylinders; a crankcase; a gas pressure source configured to transport gas along a ventilation path to remove blow-by from the crankcase; wherein the ventilation path comprises at least one ventilation passage having an opening proximate a lowest extent of the one or more cylinders.

2. The engine of claim 1, wherein the opening is at substantially the same level as the lowest extent of the one or more cylinders.

3. The engine of claim 1 or claim 2, wherein the engine structure comprises a plurality of cylinders.

4. The engine of claim 3, wherein at least two of the plurality of cylinders are provided with corresponding ventilation passages having openings proximate the lowest extent of the corresponding cylinders.

5. The engine of claim 4, further comprising a manifold arranged to connect the at least two ventilation passages.

6. The engine of claim 5, wherein the manifold extends longitudinally along the engine.

7. The engine of claim 5 or claim 6, wherein the manifold is integral with the engine structure.

8. The engine of claim 7, wherein the manifold is a linear rail provided within the engine structure.

9. The engine of any preceding claim, wherein the engine further comprises a gear case and a further ventilation passage connects the ventilation path to the gear case.

10. The engine of claim 9, wherein the further ventilation passage connects the gearcase to the manifold.

11. The engine of claim 9 or claim 10, wherein the further ventilation passage connects to an upper part of the gear case.

12. The engine of claim 3 or any of claims 4 to 11 when dependent on claim 3, wherein the at least two cylinders are arranged in line.

13. The engine of claim 12, wherein a wall extends downwardly intermediate two cylinders from a bottom of the cylinders towards a crankshaft journal bearing seat, thereby separating an under piston area of the crankcase into two separate bays.

14. The engine of claim 13, wherein an aperture is provided in the wall.

15. The engine of any preceding claim, wherein the gas pressure source is a pump.

16. The engine of any preceding claim, wherein the gas pressure source is configured to draw ventilation gas into the crankcase via the one or more ventilation passages.

17. The engine of any preceding claim, wherein at least one of the one or more ventilation passages comprises a nozzle mounted thereto and arranged to direct ventilation gas towards an underside of a piston adjacent thereto.

18. The engine of any preceding claim, wherein the or each cylinder has a displacement in a range of 0.75 and 1.5 litres.

19. The engine of claim 18, having a maximum power output in a range of lOkW to 35kW per cylinder, optionally 12kW to 33kW per cylinder.20 The engine of any preceding claim, wherein the engine is a hydrogen powered engine and comprises a hydrogen fuel delivery system.

21. The engine of claim 20, further comprising an air inlet passage upstream of the cylinder and the hydrogen fuel delivery system injects hydrogen into the inlet passage.

22. The engine of claim 20, wherein the hydrogen fuel delivery system injects hydrogen directly into the cylinder.

23. The engine of any preceding claim, further comprising a nozzle arranged to direct a jet of oil towards the underside of the or each piston, optionally wherein the nozzle arranged to direct a jet of oil is located on the opposite side of the cylinder from the at least one ventilation passage.

24. A working machine or genset comprising an internal combustion engine according to any of claims 1 to 23 and a fuel tank storing a gaseous fuel such as hydrogen, the fuel tank being in fluid flow communication with a fuel delivery system.

25. An engine structure defining a plurality of adjacent cylinders; each of the cylinders being arranged to receive a corresponding piston; a crankcase; a wall extending downwardly intermediate two adjacent cylinders from a bottom of the cylinders towards a crankshaft journal bearing seat for receiving a crankshaft, the wall thereby separating an under piston area of the crankcase into two separate bays; wherein an aperture is provided in the wall to permit fluid communication between the bays.

26. The engine structure of claim 25, wherein the aperture is above a midpoint of the crankshaft bearing journal.

27. The engine structure of claim 26, wherein the aperture is closer to the bottom of the cylinders than to the midpoint of the crankshaft journal bearing.

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