Internal combustion engine

Abstract

To improve engine efficiency, in an internal combustion engine 100 having at least one cylinder 1 having an inner diameter of at least 200 mm, being a low pressure fuel fluid engine, or a duel-fuel engine 1 having at least one fluid admission valve 29 for providing a fuel fluid.SOLUTION: A cylinder has a plurality of scavenging ports 10 which fluid-communicate with a scavenging chamber 4 surrounding a first end side 6a of the cylinder. An internal combustion engine has at least one mixing chamber 11 which is arranged in the scavenging chamber, and provides a mixing volume 12. The mixing chamber has at least one inlet port 13, at least one feed nozzle 14 arranged in each of the inlet ports 13, and introducing a fuel fluid into the mixing chamber, and at least one outlet 15. Each outlet 15 faces at least one scavenging port 10, and preferably, up to four adjacent scavenging ports 10.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an internal combustion engine according to the preamble of the independent claim and a method for operating an internal combustion engine.

[0002] The present invention preferably relates to an internal combustion engine such as a large marine engine, a marine engine or a stationary engine, the cylinder of which has an inner diameter of at least 200 mm. The engine is preferably a two-stroke engine or a two-stroke crosshead engine. The engine may be a gas engine, a dual fuel engine or a multi-fuel engine. It is possible to burn liquid fuel or gaseous fuel in such an engine, and furthermore, self-ignition or forced ignition is also possible.

[0003] The internal combustion engine may be a longitudinally scavenged two-stroke engine.

Background Art

[0004] The term internal combustion engine also means a large engine that can be operated not only in the diesel mode characterized by self-ignition of fuel, but also in the Otto mode characterized by spark ignition of fuel or a mixture of two fuels. Furthermore, the term internal combustion engine particularly includes dual fuel engines and large engines in which self-ignition of fuel is used for spark ignition of another fuel.

[0005] The engine speed is preferably less than 800 RPM, more preferably less than 200 RPM, particularly in a two-stroke engine, which indicates the designation of a low-speed engine.

[0006] The fuel may be diesel oil or marine diesel oil, heavy oil, emulsion, slurry, methanol, or ethanol, or even gases such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG).

[0007] Other possible fuels that may be added upon request include: liquefied biogas (LBG), biofuels (e.g., oil made from raw algae or seaweed), ammonia, hydrogen, and synthetic fuels from CO2 (e.g., made by power-to-gas or power-to-liquid).

[0008] Large ships, especially those used for transporting cargo, are typically powered by internal combustion engines, often diesel and / or gas engines, most of which are two-stroke cross-head engines.

[0009] It is known that high-pressure or low-pressure fuel is injected directly into a pressure cylinder. The timing can be selected to allow the passage and ejection of the air-fuel mixture to be reduced or avoided. Insufficient mixing of the fuel fluid and the active fluid may occur, potentially leading to localized high concentrations of the fuel fluid, which can cause problems such as premature ignition or the release of unburned fluid.

[0010] The admission hole located within the cylinder liner can disrupt the pressure within the piston's ring package.

[0011] WO2018135191A1 discloses a two-stroke engine in which fuel is delivered through a nozzle into the space in front of the scavenging port. Fuel injection begins after the scavenging port is released from the piston and ends before the scavenging port is closed again.

[0012] EP3296557B1 represents a two-stroke engine, where fuel is delivered into a scavenging air chamber surrounding the cylinder. Fuel is delivered from the main supply source through a valve into the ring line. Fuel lines branch off from the ring line and have holes through which fuel can enter the scavenging chamber, where it is mixed with the scavenging air. As with mixing in the cylinder, insufficient mixing can occur, resulting in an uneven distribution of fuel-gas concentrations, which can further lead to misfiring events such as premature ignition or knocking. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] International Publication No. 2018 / 135191(A1) Pamphlet [Patent Document 2] European Patent No. 3296557(B1) [Overview of the project] [Problems that the invention aims to solve]

[0014] The object of the present invention is to avoid the drawbacks of the prior art and, in particular, to provide an internal combustion engine and a method for operating an internal combustion engine that enable improved engine efficiency. [Means for solving the problem]

[0015] This objective is achieved by an internal combustion engine and a method for operating an internal combustion engine, as defined in the independent claims.

[0016] The internal combustion engine has at least one cylinder, preferably having a bore of at least 200 mm.

[0017] The internal combustion engine is a low pressure fuel gas engine or a dual fuel engine, and preferably a large two-stroke internal combustion engine.

[0018] The internal combustion engine has at least one fluid inlet valve for providing a fuel fluid. In the present application, the fuel fluid may be a fuel gas or a fuel liquid.

[0019] The cylinder has a plurality of scavenging ports fluidly connected to a scavenging chamber. The scavenging chamber surrounds at least a portion of the first end side of the cylinder in the piston stroke direction, and scavenging can be introduced into the scavenging chamber.

[0020] The scavenging may be an example of an active gas that is compressed, cooled, dehydrated, and contains an oxidizing agent such as oxygen or ozone or a mixture thereof (e.g., air). The scavenging may further contain recirculated exhaust gas or different types of inert gas.

[0021] The scavenging port may be a hole passing from the inner circumferential surface, which is the inner circumferential surface of the cylinder liner on the first end side of the cylinder, to its outer circumferential surface, and a plurality of scavenging ports may be provided around the entire circumference of the cylinder.

[0022] The scavenging port can be opened and closed by the piston movement in the cylinder.

[0023] The internal combustion engine has at least one mixing chamber that provides a mixing volume portion disposed in the scavenging chamber.

[0024] The mixing chamber has at least one inlet port for introducing scavenging, at least one supply nozzle for introducing the fuel fluid into the mixing chamber, and at least one outlet.

[0025] At least one mixing chamber can be arranged in the scavenging chamber, so that scavenging can enter the cylinder only through the mixing chamber. Therefore, the scavenging needs to enter the mixing chamber through the inlet port, pass through the mixing volume part, and leave the mixing chamber through the outlet to reach the scavenging port. In addition to the mixing chamber, there may not be a direct fluid connection between the scavenging chamber and the scavenging port. The scavenging does not need to bypass the mixing chamber to be sucked into the cylinder. By doing so, the fuel fluid can be optimally mixed with the scavenging regardless of the amount of fuel fluid supplied.

[0026] At least one lambda value (air-fuel ratio) can be reached within the mixing volume part. In the case of an engine that does not use exhaust gas recirculation, at least two lambda values can be achieved.

[0027] Preferably, at least one supply nozzle is arranged in the inlet port, and more preferably in each inlet port. The fuel fluid can enter the mixing volume part together with the scavenging. The fuel fluid can be supplied to the scavenging so that a uniformly distributed mixture is formed.

[0028] Each outlet faces (i.e., faces) at least one scavenging port.

[0029] The mixing chamber can have one outlet for each scavenging port, or can have one outlet for up to 8 adjacent scavenging ports, preferably up to 4 adjacent scavenging ports.

[0030] The fluid inlet valve can supply pressurized fuel gas or pressurized fuel liquid. Inside the mixing chamber, the fuel gas or fuel liquid expands and mixes well with the scavenging, resulting in a fuel / air mixture being provided.

[0031] By pre-mixing the fuel and air, the fuel enters the cylinder and mixes well with the scavenging gas, thus enabling a uniform distribution within the cylinder. Regions with very low fuel-ratio and very high fuel-ratio mixtures within the combustion chamber are reduced. In addition, by optimizing the start and end of gas entry to allow natural gas to enter the mixing chamber, fuel is prevented from entering, for example, the gap in the combustion chamber between the piston and the liner, thereby reducing direct fuel loss from the cylinder during the scavenging process.

[0032] Specifically, the percentage of unburned fuels such as methane is reduced, the tendency for ignition to occur before the desired ignition timing and the tendency for knocking combustion are reduced, and therefore engine efficiency is improved and the engine operating cycle in dual-fuel-gas mode is improved.

[0033] The required fuel pressure can be reduced because the fuel fluid is premixed with scavenging outside the cylinder, resulting in a well-prepared fuel / air mixture entering the cylinder.

[0034] Furthermore, the mixing chamber becomes suitable for the fuel gas, and even more so for the fuel liquid.

[0035] The internal combustion engine may be a single-flow scavenging two-stroke engine that can be used as a ship's engine. The scavenging chamber may be located on the first end side of the cylinder, while the exhaust port may be located on the second end side in the stroke direction of the piston within the cylinder.

[0036] The exhaust port may be an opening located at the second end, for example, within the cylinder head, and situated above the top dead center of the piston, and is opened and closed to discharge exhaust gases generated in the cylinder after combustion. When the exhaust port is opened, exhaust gases are discharged from the cylinder through the exhaust port.

[0037] At least one mixing chamber may be coaxially positioned around at least a portion of the cylinder, specifically corresponding to a scavenging port coaxially located within the cylinder wall. The mixing chamber may be positioned at the same axial level as the scavenging port, that is, at the same level as the scavenging port between top dead center and bottom dead center. Thus, the path of the fuel / air mixture to the cylinder volume portion is shortened.

[0038] At least one of the mixing chambers can supply a mixture of fuel and scavenging to one scavenging port, and further to multiple adjacent scavenging ports, or even to all scavenging ports.

[0039] An internal combustion engine may have exactly one mixing chamber, which may extend in an annular manner around the entire cylinder, providing an annular mixing volume.

[0040] An annular mixing chamber may have an annular inlet port and / or an annular outlet. The annular outlet may function for all scavenging ports. Alternatively, an annular mixing chamber may have multiple inlet ports and / or multiple outlets.

[0041] Instead of one annular mixing chamber, at least two mixing chambers may be arranged on a coaxial ring around the cylinder. Multiple mixing chambers may be arranged in an annular pattern around the cylinder. Each mixing chamber can function for up to eight, preferably four, adjacent scavenging ports.

[0042] Each of the multiple mixing chambers may have one inlet port and one supply nozzle. Alternatively, each of the multiple mixing chambers may have multiple inlet ports and / or multiple outlets.

[0043] The mixing chamber may have a neck adjacent to and / or surrounding the outlet, the neck preferably in contact with the outer wall of the cylinder. The neck may be positioned such that the outlet covers one or more adjacent scavenging ports and the outlet guides the flow of the fuel / air mixture so that the fuel / air mixture simply enters the cylinder and does not return to the scavenging chamber.

[0044] The neck section can prevent the scavenging air form from entering the scavenging port without passing through the mixing chamber.

[0045] Each inlet port may have an inlet pipe. At least a portion of the inlet pipe may have an axis, preferably parallel or perpendicular to the cylinder axis. Thus, scavenging can be supplied to the mixing chamber in the axial or radial direction.

[0046] At least one supply nozzle may be located within the inlet pipe, preferably positioned to supply the fuel liquid primarily in the direction of the pipe axis. Mixing of the fuel fluid and scavenging may be initiated in the inlet pipe.

[0047] The inlet pipe may be formed as a venturi mixer, with a supply nozzle located coaxially with respect to the pipe axis within the wall of the intermediate section of the pipe. The intermediate section of the pipe has a smaller diameter than the upstream and downstream sections of the pipe.

[0048] In the intermediate section, the fuel fluid must increase its velocity while its pressure decreases. As the fluid leaves the intermediate section, its pressure increases back to the pipe level. Furthermore, the pressure change in the intermediate section alters the flow of the supplied fuel so that it merges with and mixes with the main airflow at the required rate. The fuel fluid can be supplied without a pump, or at least with reduced pump power.

[0049] Alternatively, the inlet pipe may have an intermediate section having a larger diameter compared to the upstream and downstream sections of the inlet pipe. At least one supply nozzle may be located within the intermediate section. The fuel fluid and scavenging are mixed under turbulent conditions.

[0050] A static mixer may be placed in the inlet pipe downstream of the supply nozzle. The static mixer can improve the mixing of the combined fuel fluid and scavenging. Therefore, the flow path within the mixing chamber for mixing can be reduced.

[0051] A throttle valve may be located in the inlet pipe downstream of the supply nozzle.

[0052] By setting a throttle valve, the entry of scavenging air into the mixing chamber can be controlled. Therefore, especially in combustion engines with multiple cylinders, the entry of scavenging air can be equalized with other mixing chambers. Furthermore, under low load conditions, the supply of scavenging air can be reduced. The throttle can also be used to further improve the mixture of fuel gas and scavenging air.

[0053] An internal combustion engine may have a control device for setting a throttle valve.

[0054] An internal combustion engine may have a control device that allows the supply nozzle to open to inject fuel into the mixture chamber after the scavenging port has begun to open, and to stop the injection before the scavenging port closes.

[0055] Therefore, the risk of injecting unburned fuel through the exhaust outlet is reduced.

[0056] In another embodiment, the internal combustion engine has at least one gas inlet valve for providing fuel fluid, and further has at least one fuel supply chamber located downstream of the at least one gas inlet valve and upstream of the cylinder volume. Preferably, the fuel supply chamber is located upstream of a plurality of supply nozzles and is fluidly connected to the plurality of supply nozzles. Preferably, the internal combustion engine has one to three fuel supply chambers which may be located at various axial levels. Each fuel supply chamber may be located downstream of one to five fluid inlet valves.

[0057] Preferably, the fuel supply chamber does not have an inlet port for introducing scavenging air, and scavenging air is not allowed to enter the fuel supply chamber. The fuel supply chamber can then realize the distribution of fuel fluid around the cylinder.

[0058] The combustion engine is a low-pressure fuel gas engine or a dual-fuel engine having at least one cylinder, preferably with an inner diameter of at least 200 mm, and preferably a large longitudinal scavenging two-stroke internal combustion engine. Specifically, the combustion engine is the combustion engine described above.

[0059] One or more fluid inlet valves may be installed on the fuel supply chamber. The fluid inlet valves may be actuated to allow pressurized fluid to enter the fuel supply chamber. Preferably, four to sixteen fluid inlet valves are installed around the cylinder.

[0060] The supply nozzle may be positioned to supply fuel fluid to the mixing chamber or directly to the cylinder. The cylinder may have nozzle openings within the cylinder wall defining the supply nozzle, and may have, for example, 40 to 50 nozzle openings. The nozzle openings may have axes that are radially oriented or that have a certain angle with respect to the radial direction. The axes of the nozzle openings may be perpendicular to the cylinder axis or that have a certain angle with respect to a horizontal plane perpendicular to the cylinder axis.

[0061] One or more such fuel supply chambers may be mounted on a single cylinder such that they have an axial distance that optimizes fuel fresh charge mixing.

[0062] The fuel supply chamber may be coaxially arranged around at least a portion of the cylinder. Preferably, one supply chamber may extend annularly around the cylinder and may be fluidly connected to all the supply nozzles.

[0063] The location of such a fuel supply chamber is preferably within the lower half of the piston stroke. A location that allows the new fuel input flowing into the cylinder through the scavenging port to enter a region of high turbulence is advantageous.

[0064] The fuel supply chamber may be positioned at the same axial level as the mixing chamber, above the axial level of the mixing chamber, or below the axial level of the mixing chamber.

[0065] In another embodiment, an internal combustion engine has at least one fluid inlet valve for supplying fuel fluid. A check valve is located in the flow path between the at least one fluid inlet valve and the cylinder volume portion, preferably located in a supply nozzle.

[0066] The combustion engine is a low-pressure fuel gas engine or a dual-fuel engine having at least one cylinder, preferably with an inner diameter of at least 200 mm, and preferably a large longitudinal scavenging two-stroke internal combustion engine. Specifically, the combustion engine is the combustion engine described above.

[0067] Check valves reduce dead volume. Dead volume is the volume from which fuel can enter the cylinder after the fluid inlet valve is closed. Check valves can further improve the fuel dynamics within the system. Because check valves reduce dead volume, response to change requests can be made more quickly. Smaller volume also reduces the inertia of the system.

[0068] Preferably, the check valve is positioned such that it reduces dead volume by at least 70% to 80% compared to a configuration without a check valve.

[0069] In another embodiment, a method is provided for operating the above-described internal combustion engine having a cylinder with a scavenging port, a mixing chamber, and a supply nozzle. The method includes the steps of opening the supply nozzle to inject fuel into the mixing chamber after the scavenging port has been opened, and stopping the injection before the scavenging port is closed.

[0070] In this context, as soon as the scavenging port is opened, a mixture of scavenging gas and fuel fluid can enter the cylinder. Similarly, the scavenging port is closed when the gas cannot enter the cylinder, i.e., when the piston is above the scavenging port.

[0071] To scavenge the cylinder, a first pure scavenging gas can be introduced into the cylinder. Then, a supply nozzle is opened to allow a mixture of the scavenging gas and fuel fluid to enter the cylinder.

[0072] Preferably, the internal combustion engine has control devices for setting valves, and more specifically, for enabling the opening of supply nozzles and stopping injection.

[0073] The present invention will be further described below with reference to the figures. The same reference numerals indicate functionally corresponding structural parts. [Brief explanation of the drawing]

[0074] [Figure 1] This is a schematic diagram illustrating an internal combustion engine. [Figure 2] This is a schematic side view showing a first example of the first end side of a cylinder. [Figure 3] This is a schematic top cross-sectional view showing the first example. [Figure 4] This is a schematic side view showing a second example of the first end side of the cylinder. [Figure 5] This is a schematic side view showing a cylinder using a second example of the first end side of the cylinder. [Figure 6] This is a schematic diagram showing the first example of an inlet pipe. [Figure 7] This is a schematic diagram showing a second example of an inlet pipe. [Figure 8] This is a schematic diagram showing a third example of an inlet pipe. [Figure 9] This is a schematic diagram showing a fourth example of an inlet pipe. [Figure 10] This is a schematic graph showing valve settings according to crank position / time. [Figure 11a] This is a schematic side cross-sectional view showing another example of an internal combustion engine. [Figure 11b] This is a schematic top cross-sectional view showing another example of an internal combustion engine. [Figure 12] This is a schematic side cross-sectional view showing a cylinder liner of another example of an internal combustion engine. [Modes for carrying out the invention]

[0075] Figure 1 shows a schematic diagram of an internal combustion engine 100. The internal combustion engine is a large two-stroke internal combustion engine having at least one cylinder 1 with a bore diameter 7 of at least 200 mm. A reciprocating piston 2 is connected to a crosshead, which is not shown in the figure.

[0076] Cylinder 1 has a plurality of scavenging ports 10, for example, 32 scavenging ports, and the plurality of scavenging ports 10 are in fluid communication with a scavenging chamber 4. The scavenging chamber 4 surrounds the first end side 6a of cylinder 1. An exhaust port 3 is located on the second end side 6b of cylinder 2.

[0077] The internal combustion engine 100 has at least one mixing chamber 11 located within the scavenging chamber 4. In the mixing chamber 11, the fuel fluid and scavenging are mixed before they enter the cylinder through the scavenging port 10.

[0078] Figure 2 shows a schematic side view of a first example of the first end side 6a of cylinder 1. At the first end side 6a, a plurality of mixing chambers 11 are arranged around cylinder 1.

[0079] Each mixing chamber 11 has an inlet port 13 for introducing scavenging air into the mixing chamber 11. A supply nozzle 14 for introducing fuel fluid into the mixing chamber is located within each inlet port 13.

[0080] Each mixing chamber 11 has an outlet 15 facing at least one scavenging port 10.

[0081] Each mixing chamber 11 provides a mixing volume section 12, in which the scavenging and fuel fluids form a mixture as uniformly as possible before entering the cylinder 1.

[0082] Figure 3 shows a schematic diagram of the first example in a top-down cross-sectional view. The mixing chamber 11 is arranged as a circle around the cylinder 1. Fuel fluid is supplied to the supply nozzles 14 via the fuel supply chamber 28. Each fuel supply chamber is fluidly connected to a fluid inlet valve 29. Thus, each fluid inlet valve 29 can supply fuel fluid to all the supply nozzles 14 connected to their respective fuel supply chambers 28.

[0083] Instead of using a fuel supply chamber 28 with fewer fuel inlet valves 29 than supply nozzles 14, the fuel inlet valves 29 may be integrated with the supply nozzles 14, thereby resulting in an equal number of fuel inlet valves 29 and supply nozzles 14.

[0084] Figure 4 shows a schematic side view of a second example of the first end side 6a of the cylinder, and Figure 5 shows a schematic side view of the second example.

[0085] In this example, one mixing chamber 11 is arranged in an annular manner around the cylinder 1. The mixing chamber 11 may have multiple inlet ports 3 (see Figure 5) or it may have an annular inlet port. The mixing chamber 11 may have multiple supply nozzles 14. The supply nozzles 14 receive a supply through a single common fuel supply chamber 28, and the supply to the fuel supply chamber 28 is provided by four fluid inlet valves 29.

[0086] Furthermore, in the case of one annular mixing chamber 11, the fluid inlet valve 29 may be integrated with the supply nozzle 14, resulting in the installation of the same number of fuel inlet valves 29 and supply nozzles 14.

[0087] As can be seen in Figure 5, the inlet port 13 may be formed as a separate inlet tube 17 having an axis 18 parallel to the axis 9 of the cylinder 1, or the inlet port 13 may be formed as an annular collar having a single annular opening.

[0088] The mixing chamber 11 has a neck portion 16 adjacent to the outlet 15, and the neck portion 16 is in contact with the outer wall 8 of the cylinder 1. Therefore, the mixture of fuel fluid and scavenging is reliably guided into the cylinder.

[0089] Figure 6 shows a schematic diagram of a first example of the inlet pipe 17. The inlet pipe 17 has an intermediate section 21' having a larger diameter 25 compared to the upstream section 22' and downstream section 23' of the inlet pipe 17. The supply nozzle 14 is located within the intermediate section 21'.

[0090] At the upstream section 22', the scavenging air entering the inlet pipe 17 forms turbulence within the intermediate section 21', thereby promoting uniform mixing with the incoming fuel fluid.

[0091] Figure 7 shows a schematic diagram of a second example of the inlet pipe 17, along the axis 18 (top) and perpendicular to the axis 18 (bottom).

[0092] In this example, the inlet pipe 17 is formed as a venturi mixer 19, which includes a supply nozzle 14 coaxially positioned within the wall 20 of the intermediate portion 21 of the inlet pipe 17. In this example, the intermediate portion 21 has a smaller diameter 24 than the upstream portion 22 and the downstream portion 23 of the inlet pipe 17.

[0093] The scavenging flow in the intermediate section 21 is accelerated, drawing the fuel fluid into the inlet pipe 17.

[0094] Figure 8 shows a schematic diagram of a third example of the inlet pipe 17. A supply nozzle 14 is located inside the inlet pipe 17, and a static mixer 27 is located downstream of the supply nozzle 14. The flow path is determined by the static mixer 27, which generates turbulence and thereby enables mixing of the scavenging gas and fuel fluid.

[0095] Figure 9 shows a schematic diagram of a fourth example of the inlet pipe 17. The throttle valve 26 is located inside the inlet pipe 17 downstream of the supply nozzle 14.

[0096] By setting a throttle valve, the inflow of scavenging air that is well mixed with the fuel fluid can be equalized, which may be necessary when not all inlet pipes 17 are supplied with scavenging air and / or fuel fluid at the same pressure, for example, when the distance between the scavenging reservoir 5 (see Figure 1) and the inlet pipe 17 and / or the distance between the fluid inlet valve 29 (see Figures 3 and 4) and the supply nozzle 14 differs in each inlet pipe 17.

[0097] Figure 10 shows a schematic graph of valve settings according to crank angle. The dashed line schematically shows the setting of exhaust port 3 (see Figure 1), the dotted line shows the setting of fluid inlet valve 29 (see Figures 3 and 4), and the solid line shows the state of scavenging port 10 (see Figure 1).

[0098] The fuel needs to be allowed to be introduced at a specific crank angle interval, with the objective of preventing some of the fuel from leaving the cylinder during the scavenging process, and on the other hand, with the objective of obtaining the best possible mixture result.

[0099] As piston 2 (see Figure 1) moves downward during the power stroke, exhaust port 3 (see Figure 1) opens, and then the piston opens scavenging port 10.

[0100] The initiation of fuel entry into the mixing chamber 11 should be timed so that the cylinder is scavenged by the new fuel input, but the amount of fuel exiting the cylinder 1 through the exhaust port 3 during the scavenging process is minimized or eliminated. Direct methane slip will be prevented. To optimize the mixing of the fuel with the new fuel input, the entry duration and the timing of the fuel fluid entering the new scavenging chamber need to be optimized. During the compression stroke, the entry of fuel fluid should stop before the piston 2 closes the scavenging port 10.

[0101] Typically, the scavenging port 10 opens at a crank angle (CA) of approximately 40° before the piston reaches bottom dead center, or at a CA of 140° after the piston has passed top dead center.

[0102] Typically, the scavenging port 10 closes at a CA of approximately 40° after the piston has passed bottom dead center, or at a CA of 220° after the piston has passed top dead center.

[0103] The exhaust port closes at a CA of 240° to 280°, where the actual closure of the exhaust valve is determined by the engine load.

[0104] Gas entry typically begins at a CA of 20° after the scavenging port opens, or at a CA of 160° after the piston has passed top dead center. Gas entry typically ends at a CA of approximately 5° before the scavenging port 10 closes, or at a CA of 215° after the piston has passed top dead center.

[0105] Figure 11a shows a schematic diagram of another example of the internal combustion engine 100 in a side cross-sectional view, and Figure 11b shows a schematic diagram of the same example in a top cross-sectional view.

[0106] Two fuel supply chambers 28, spaced apart in the axial direction, are arranged around the cylinder 1. Each fuel supply chamber 28 is positioned downstream of four fluid inlet valves 29 and upstream of the volume 31 of the cylinder 1. Alternatively, one to ten fluid inlet valves 29 may be fitted to each fuel supply chamber.

[0107] In this example, a fuel fluid nozzle 14' is positioned within the wall 20 of the cylinder 1 and provides a directed fluid stream 32, the directed fluid stream 32 having a first angle γ between -45° and 45°, preferably between -25° and 25°, with respect to a horizontal plane 33 perpendicular to the cylinder axis 9, and a second angle β between -70° and 70°, preferably between -45° and 45°, with respect to a radial direction 34 in the horizontal plane 33.

[0108] The fluid nozzles 14' are positioned at the same axial level and evenly spaced apart.

[0109] Generally, one or more fluid inlet valves 29 may be installed on each fuel supply chamber 29. The fuel inlet valves 29 may be operated to allow pressurized fuel to enter the fuel supply chamber 29. Generally, one or more such fuel supply chambers 29 may be mounted on a single cylinder to optimize the mixing of fuel with fresh input.

[0110] Figure 12 shows a schematic diagram of a cylinder wall 20 of another example for an internal combustion engine, in a lateral cross-sectional view.

[0111] In this example, a fuel inlet valve 29 (not shown in the figure) is installed on the outside of the wall 20 of cylinder 1. The nozzle volume 35 of the fluid inlet valve 29 is directly connected to the supply nozzle 14', thereby forming a flow path between the fluid inlet valve 29 and the cylinder volume portion 31.

[0112] A check valve 30 is positioned within each supply nozzle 14'. The check valve 30 remains closed without pressure from the fluid inlet valve 29. After the fluid inlet valve 29 is closed, the dead volume downstream of the fluid inlet valve 29, from which the fuel fluid can enter the cylinder volume portion, is reduced.

[0113] Generally, the check valve 30 can be placed anywhere in the flow path between the gas inlet valve 29 and the cylinder volume portion 31, and preferably it can be placed close to the cylinder volume portion 31.

Claims

1. An internal combustion engine (100) having at least one cylinder (1) with an internal diameter of at least 200 mm, i.e. a large two-stroke internal combustion engine, i.e. a low pressure fuel fluid engine or dual fuel engine (1) having at least one fluid inlet valve (29) for providing a fuel fluid, wherein the cylinder (1) has a plurality of scavenging ports (10) in fluid communication with a scavenging chamber (4), the scavenging chamber (4) surrounding a first end side (6a) of the cylinder (1), the internal combustion engine (100) has at least one mixing chamber (11) arranged in the scavenging chamber (4) and providing a mixing volume (12); and The mixing chamber (11) at least one inlet port (13) for introducing scavenging air; at least one supply nozzle (14) for introducing fuel fluid into said mixing chamber; at least one outlet (15), each outlet (15) facing at least one scavenging port (10); An internal combustion engine (100) comprising:

2. At least one supply nozzle (14) is disposed within each inlet port (13); and Each outlet (15) faces up to four adjacent scavenging ports (10).

10. The internal combustion engine (100) of claim 1, characterized by at least one of:

3. 2. The internal combustion engine (100) of claim 1, wherein the mixing chamber (11) is arranged coaxially around at least a portion of the cylinder (1).

4. 4. An internal combustion engine (100) according to claim 3, wherein one mixing chamber (11) extends annularly around the cylinder (1) to provide an annular mixing volume (12).

5. 4. An internal combustion engine (100) according to claim 3, wherein a plurality of mixing chambers (11) are arranged annularly around the cylinder (1).

6. 2. The internal combustion engine (100) of claim 1, wherein the mixing chamber (11) has a neck (16) adjacent the outlet (15), the neck (16) contacting the outer wall (8) of the cylinder (1).

7. 2. An internal combustion engine (100) according to claim 1, wherein each inlet port (13) has an inlet pipe (17) with an axis (18) that is parallel or perpendicular to the axis (9) of the cylinder (1).

8. 8. The internal combustion engine (100) of claim 7, wherein the inlet pipe (17) is formed as a venturi mixer (19) comprising a plurality of supply nozzles (14) arranged coaxially in a wall (20) of an intermediate section (21) of the inlet pipe (17), the intermediate section (21) having a smaller diameter (24) than the upstream and downstream sections (22 and 23) of the inlet pipe (17).

9. 8. The internal combustion engine (100) of claim 7, wherein the inlet pipe (17) has an intermediate portion (21′) with an enlarged diameter (25) compared to the upstream portion (22′) and the downstream portion (23′) of the inlet pipe (17), and wherein at least one supply nozzle (14) is arranged in the intermediate portion (21′).

10. 8. The internal combustion engine (100) of claim 7, wherein a throttle valve (26) is arranged in the inlet pipe (17) downstream of the supply nozzle (14).

11. The internal combustion engine (100) of claim 7, wherein a static mixer (27) is disposed in the inlet pipe (17) downstream of the supply nozzle (14).

12. 2. The internal combustion engine (100) of claim 1, further comprising a control device for enabling the supply nozzle (14) to open to inject fuel into the mixing chamber (11) after the scavenging ports (10) have started to open, and for stopping injection before the scavenging ports (10) are closed.

13. An internal combustion engine (100) having at least one cylinder (1) with an internal diameter of at least 200 mm, i.e. a large longitudinally scavenged two-stroke internal combustion engine, i.e. a low-pressure fuel fluid engine or dual-fuel engine (1) having at least one fluid inlet valve (29) for providing a fuel fluid, The internal combustion engine (100) is characterized in that it has at least one fuel supply chamber (28) arranged downstream of the at least one fluid admission valve (29) and upstream of a cylinder volume portion (31).

14. An internal combustion engine (100) as described in claim 13, wherein the at least one fuel supply chamber (28) is positioned upstream of a plurality of supply nozzles (14; 14') and fluidly connected to the plurality of supply nozzles (14; 14').

15. 14. The internal combustion engine (100) of claim 13, wherein the fuel supply chamber (28) is coaxially disposed around at least a portion of the cylinder (1).

16. An internal combustion engine (100) as claimed in claim 15, wherein one supply chamber (28) extends annularly around the cylinder (1) and is fluidly connected to all supply nozzles (14; 14').

17. An internal combustion engine (100) having at least one cylinder (1) with an internal diameter of at least 200 mm, i.e. a large longitudinally scavenged two-stroke internal combustion engine, i.e. a low pressure fuel fluid engine or dual fuel engine (1) having at least one fluid inlet valve (29) for providing a fuel fluid, An internal combustion engine (100), characterized in that a check valve (30) is arranged in the flow path between said at least one fluid admission valve (29) and the cylinder volume (31).

18. 18. A method of operating an internal combustion engine according to any one of claims 1, 13 and 17, comprising the steps of: opening the delivery nozzle to inject fuel into the mixing chamber after the scavenge port is opened; stopping injection before the scavenging port is closed; A method comprising:

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