INTERNAL COMBUSTION ENGINE AND A METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE

Abstract

A controller configured to control a gas mixing device and/or a port injection valve and a direct fuel injector of an internal combustion engine in order to: in a first operation mode, supply a first gaseous fuel to at least one main combustion chamber of the internal combustion engine via at least one intake valve, in a second operation mode, supply a second gaseous fuel to the at least one main combustion chamber of the internal combustion engine by use of the direct fuel injector, wherein a supply system for providing flushing gas to the direct fuel injector is provided and the controller is configured to activate the direct fuel injector during operation according to the first operation mode, such that the flushing gas is injected into the at least one main combustion chamber.

Claims

1. A system, comprising: a controller configured to control a supply of fluids to at least one main combustion chamber of an internal combustion engine to: in a first operation mode, supply a first fuel to at least one main combustion chamber of the internal combustion engine via at least one intake valve; in a second operation mode, supply a second fuel to the at least one main combustion chamber of the internal combustion engine via a fuel injector; and activate the fuel injector in the first operation mode to supply a flushing gas into the at least one main combustion chamber during an exhaust stroke of the internal combustion engine.

2. The system of claim 1, wherein the controller is configured to supply the flushing gas comprising fuel during the exhaust stroke to cause combustion of the fuel in an exhaust manifold to increase an exhaust temperature of an exhaust gas.

3. The system of claim 2, wherein the combustion of the fuel in the exhaust manifold is configured to increase the exhaust temperature of the exhaust gas for a selective catalytic reduction (SCR) converter.

4. The system of claim 2, wherein the controller is configured to supply the flushing gas comprising the fuel that provides maximally 30% of the overall energy released during the combustion cycle during the first operation mode.

5. The system of claim 1, wherein the controller is configured to supply the flushing gas via the fuel injector only during a cycle when the fuel injector is not used for fuel injection.

6. The system of claim 5, wherein the controller is configured to supply the flushing gas via the fuel injector only during the first operation mode when the fuel injector is not used for fuel injection of the second fuel.

7. The system of claim 5, wherein the flushing gas excludes fuel.

8. The system of claim 7, wherein the controller is configured to supply the flushing gas that excludes fuel in a mass that is maximally 50% of an overall fuel mass supplied to the at least one main combustion chamber during a combustion cycle during operation according to the first operation mode.

9. The system of claim 8, wherein the flushing gas comprises an inert gas, air, or a combination thereof.

10. The system of claim 1, wherein the controller is configured to supply the flushing gas via the fuel injector for cooling and removing deposits from the fuel injector during the first operation mode when first fuel is used for combustion, after the fuel injector previously injected the second fuel for combustion in an earlier cycle.

11. The system of claim 10, wherein the second fuel comprises hydrogen.

12. The system of claim 1, comprising the internal combustion engine coupled to the controller.

13. The system of claim 1, comprising a mixer, an injection valve, or a combination thereof, configured to supply the first fuel to the at least one main combustion chamber via the at least one intake valve.

14. The system of claim 1, wherein the first fuel comprises natural gas and the second fuel comprises hydrogen.

15. A system, comprising: a controller configured to control a supply of fluids to at least one main combustion chamber of an internal combustion engine to: in a first operation mode, supply a first fuel to at least one main combustion chamber of the internal combustion engine via at least one intake valve; in a second operation mode, supply a second fuel to the at least one main combustion chamber of the internal combustion engine via a fuel injector; and activate the fuel injector in the first operation mode to supply a flushing gas into the at least one main combustion chamber only during a cycle when the fuel injector is not used for fuel injection.

16. The system of claim 15, wherein the controller is configured to supply the flushing gas via the fuel injector only during the first operation mode when the fuel injector is not used for fuel injection of the second fuel.

17. The system of claim 15, wherein the flushing gas excludes fuel, and wherein the flushing gas comprises an inert gas, air, or a combination thereof.

18. A system, comprising: a controller configured to control a supply of fluids to at least one main combustion chamber of an internal combustion engine to: in a first operation mode, supply a first fuel to at least one main combustion chamber of the internal combustion engine via at least one intake valve; in a second operation mode, supply a second fuel to the at least one main combustion chamber of the internal combustion engine via a fuel injector; and activate the fuel injector in the first operation mode to supply a flushing gas into the at least one main combustion chamber for cooling and removing deposits from the fuel injector during the first operation mode when first fuel is used for combustion, after the fuel injector previously injected the second fuel for combustion in an earlier cycle.

19. The system of claim 18, wherein the second fuel comprises hydrogen.

20. The system of claim 19, wherein the controller is configured to supply only the first fuel and air to the at least one main combustion chamber via the at least one intake valve and only the flushing gas to the at least one main combustion chamber via the fuel injector during the first operation mode, wherein the controller is configured to supply only the second fuel to the at least one main combustion chamber via the fuel injector during the second operation mode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Further details and advantages of the invention are apparent from the accompanying figures and the following description of the figures. The figures show:

[0054] FIG. 1 schematically illustrates a piston-cylinder unit of an internal combustion engine according to a first embodiment of the invention,

[0055] FIG. 2 schematically illustrates a piston-cylinder unit of an internal combustion engine according to a second embodiment of the invention,

[0056] FIG. 3 illustrates a schematic representation of the parts of an internal combustion engine, and

[0057] FIG. 4 illustrates a schematically diagram of a cylinder pressure during the combustion phases of an internal combustion engine.

DETAILED DESCRIPTION

[0058] FIG. 1 schematically shows a piston-cylinder unit of an internal combustion engine 1, wherein a reciprocating piston 3 is arranged in a cylinder 2 so as to be movable along an axis of the cylinder 2, whereby a main combustion chamber 4 is formed between the piston 3, the cylinder head 5 and the cylinder 2. At its top dead center, the piston 3 with the cylinder 2 forms the so-called compression volume.

[0059] The cylinder 2 may comprise a cylinder liner and/or a crank case. For the purpose of the present invention, such components are collectively referred to as cylinder 2.

[0060] The intake port 6 is arranged at an interface between the main combustion chamber 4 and at least one intake valve 7.

[0061] The exhaust manifold 8 is arranged at an interface between the main combustion chamber 4 and at least one exhaust valve 9.

[0062] The at least one intake valve 7 and the at least one exhaust valve 9 can be actuated by the actuators 10. Example actuators 10 for the at least one intake valve 7 and the at least one exhaust valve 9 are a camshaft or hydraulic devices.

[0063] The actuators 10 may optionally be connected by a signal line to the control unit 11, wherein opening and closing of the at least one intake valve 7 and the at least one exhaust valve 9 can be controlled by the control unit 11, e.g., in connection with a variable valve train.

[0064] A main combustion intake system 20 including a gas mixing device 12 (see FIG. 3) is arranged upstream of the intake port 6, wherein by use of the gas mixing device 12 a fuel-air-mixture (e.g., a mixture of air and natural gas) can be provided for the intake port 6. Also the gas mixing device 12 is connected by a signal line to the control unit 11, wherein the function of the gas mixing device 12 can be controlled by control unit 11.

[0065] Furthermore, at least one compressor can be arranged upstream of the intake port 6, wherein the provided air or air-fuel mixture for the intake port 6 can be charged.

[0066] The ignition source is in this embodiment a spark plug 13.

[0067] Directly at the main combustion chamber 4, two direct fuel injectors 14 are arrangedhere provided as a hydrogen injectorswherein the direct fuel injectors 14 are configured to directly inject a second gaseous fuel, preferably hydrogen, into the main combustion chamber 4. Alternatively or additionally, second fuels in the form of, e.g., e-fuels, methanol and so on are in principle conceivable.

[0068] The direct fuel injectors 14 are supplied by a second fuel by the second gaseous fuel (hydrogen) source 15, wherein the second gaseous fuel source 15 is also connected to the control unit 11 by a signal line.

[0069] The direct fuel injectors 14 are also connected by signal lines with the control unit 11, wherein the control unit 11 is configured to control an injection of the direct fuel injectors 14.

[0070] The control unit 11 of this embodiment is configured to control the gas mixing device 12 and the direct fuel injector 14 in order to: [0071] in a first operation mode, supply the first gaseous fuel to the at least one main combustion chamber 4 of the internal combustion engine 1 via the at least one intake valve 7, and to [0072] in a second operation mode, supply a second gaseous fuel to the at least one main combustion chamber by use of the direct fuel injectors 14.

[0073] During operation according to the first operation mode, the control unit 11 is configured to control the gas mixing device 12 (or a port injection valve) in order to supply an air-fuel-mixture comprising air and the first fuel (e.g., natural gas) into the at least main combustion chamber 4 via the at least one intake valve 7.

[0074] Alternatively or additionally, it can be provided that the first fuel is supplied by an port injection valve upstream of the intake valve 7 into the intake port 6 and/or the intake manifold 21, wherein the first fuel is mixed at the intake port 6 and/or the intake manifold 21 with anpreferably chargedair mass to provide the air-fuel-mixture which is supplied via the intake valve 7 into the main combustion chamber 4 during an operation according to the first operation mode.

[0075] Furthermore, the control unit 11 is configured topreferably intermittentlyactivate the direct fuel injectors 14 during operation according to the first operation mode, such that the flushing gas is injected into the at least one main combustion chamber 4. The flushing gas of this embodiment is provided to the direct fuel injectors 14 by the second gaseous fuel source 15, which also serves as a supply system of flushing gas 16 and is capable to provide the direct fuel injectors 14 during operation according to the first operation mode by the control of the control unit 11 with second fuel as flushing gas.

[0076] Therefore, during operation according to first operation mode, the air-fuel-mixture supplied via the at least one intake valve 7 to the main combustion chamber 4 of the internal combustion engine 1 is combusted, wherein the air-fuel-mixture in the main combustion chamber 4 ispreferably intermittentlyadmixed by a small second fuel mass injected via the direct fuel injectors 14.

[0077] The small second fuel mass flushing the direct fuel injectors 14 cools the direct fuel injectors 14 and removes unwanted deposits in the direct fuel injectors 14, in particular their tip portions which are directly adjacent to the main combustion chamber 4 or protrude into the main combustion chamber 4.

[0078] During operation according to the second operation mode, the control unit 11 is configured to supply a second gaseous fuel to the at least one main combustion chamber 4 of the internal combustion engine 1 by use of the direct fuel injector 14 and to supply air to the at least one main combustion chamber 4 of the internal combustion engine 1 via the at least one intake valve 7, such that an air-fuel-mixture is provided by mixing of the supplied air and the supplied second fuel in the at least one main combustion chamber 4.

[0079] The control unit 11 is configured control the direct fuel injectors 14 such that a time of injection, a time of activation of the direct fuel injector 14 and/or an amount of injected flushing gas differs from the time of injection, the time of activation of the direct fuel injector 14 and/or the amount of injected second fuel.

[0080] FIG. 2 discloses schematically a piston-cylinder unit of an internal combustion engine 1 according to a second embodiment of the invention.

[0081] The embodiment of FIG. 2 comprises [0082] a first source for the first gaseous fuel connected to the gas mixing device 12 (providing an air-fuel mixture using natural gas as fuel), and/or [0083] a second gaseous fuel source 15 for the second gaseous fuel (e.g., hydrogen) connected to the direct fuel injector 14, wherein there is furthermore provided a switching valve 18 such that the direct fuel injector 14 can be supplied with the second gaseous fuel by the second gaseous fuel source 15 during operation according to the second operation mode and can be supplied by the supply system of flushing gas 16 for providing flushing gas (e.g., air or an inert gas) during operation according to the first operation mode.

[0084] The switching valve 18, the second gaseous fuel source 15 and the supply system of flushing gas 16 are connected by a signal line with the control unit 11, wherein the control unit 11 is configured to control the gas mixing device 12 and the direct fuel injector 14 in order to: [0085] during operation according to a first operation mode, supply the first gaseous fuel to the at least one main combustion chamber 4 of the internal combustion engine 1 via the at least one intake valve 7 andpreferably intermittentlyactivate the direct fuel injector 14, such that the flushing gas provided by the supply system of flushing gas 16 is injected into the at least one main combustion chamber 4, and [0086] during operation according to a second operation mode, supply a second gaseous fuel to the at least one main combustion chamber 4 of the internal combustion engine 1 by use of the direct fuel injector 14.

[0087] A switching over of the supply with flushing and the second fuel for the direct fuel injector 14 between the first operation mode and the second operation mode, respectively, as mentioned can be achieved by use of the control unit 11 controlling the switching valve 18 accordingly.

[0088] FIG. 3 shows a schematic representation of the parts of an internal combustion engine 1 according to the invention. In the embodiment shown in FIG. 3, the internal combustion engine 1 is represented by six main combustion chambers 4, wherein each main combustion chamber 4 is fluidically coupled by transfer passages (not shown) with a pre-chamber 19.

[0089] In the embodiment of FIG. 3, the main combustion chambers 4 of the internal combustion engine 1 can be directly supplied by an air or air-fuel-mixture by use of the main combustion intake system 20.

[0090] The main combustion intake system 20 shown by the embodiment of FIG. 3 comprises intake ports 6 providing the air or air-fuel-mixture which is supplied via intake valves 7 (not shown here for reasons of clarity) to the main combustion chambers 4.

[0091] The intake ports 6 are connected to an intake manifold 21, wherein by using the intake manifold 21 the air or air-fuel-mixture (e.g., a mixture of air and natural gas) can be provided for the intake port 6.

[0092] The intake manifold 21 is used to provide air or an air-fuel-mixture for more than one main combustion chamber 4 (as can be seen in FIG. 3). In most cases, the intake manifold 21 fluidically connects the intake ports 6 with an air or air-fuel-mixture source, e.g., a gas mixing device 12.

[0093] The shown main combustion intake system 20 further comprises a turbocharger 22, wherein a compressor 23 of the turbocharger 22 is driven by the turbine 24 arranged in the exhaust line 25.

[0094] The exhaust gases after combustion in the main combustion chambers 4 are passed via the exhaust manifold 8 into the exhaust line 25 to the exhaust turbine 24 of the turbocharger 22, wherein the exhaust turbine 24 is driven by the exhaust flow.

[0095] The exhaust turbine 24 is coupled by a shaft with the compressor 23, wherein the compressor 23 is driven by the turbine 24.

[0096] The turbocharger 22 can be controlled by controlling the wastegate 26 and the compressor bypass valve 27, wherein by use of the wastegate 26 an exhaust flow bypassing the turbine 24 can be varied and by use of the compressor bypass valve 27 an air-fuel-mixture flow bypassing the compressor 23 can be controlled for controlling a boost pressure generated by the turbocharger 22.

[0097] The compressor 23 is arranged in the main combustion intake system 20 in a flow direction downstream of the gas mixing device 12 and charges the air-fuel-mixture provided by the gas mixing device 12 according to a desired boost pressure.

[0098] The gas mixing device 12 mixes an air provided by an air filter 28 with a fuel, e.g., a natural gas. The gas mixing device 12 shown by this embodiment is a gas mixing device 12 working according to the venturi principle.

[0099] In a flow direction downstream of the compressor 23 and the compressor bypass line, an intercooler 29 is provided for cooling down the charged air or air-fuel-mixture to increase the combustion efficiency.

[0100] Between the intercooler 29 and the main combustion chambers 4 (or the branches of the intake ports 6), a throttle valve 30 is provided for controlling the air or air-fuel-flow passed to the main combustion chambers 4.

[0101] Furthermore, flame arrestors 31 can be arranged between the throttle valve 30 and the intercooler 29 or the compressor bypass valve 27.

[0102] The pre-chambers 19 can be supplied by the pre-chamber intake system 32, wherein an air-fuel mixture or a second fuel (hydrogen) can be provided by the pre-chamber intake system 32 for the pre-chambers 19.

[0103] The pre-chamber intake system 32 comprises active pre-chamber 19 gas valves which are arranged at each pre-chamber 19 for controlling the supply to the pre-chambers 19 during an intake stroke and/or partially during compression stroke.

[0104] It can be provided that a single active pre-chamber 19 gas valve for at least one or each pre-chamber 19 is arranged in a spark plug sleeve, in a pre-chamber 19 or in a cylinder head 5 directly (not shown in detail).

[0105] Via the pre-chamber 19 gas valves, a fuel or air-fuel mixture can be supplied by use of the pre-chamber supply line 32.

[0106] The pre-chamber intake system 32 comprises a control valve 33, wherein the pre-chamber intake system 32 can be switched between two different fuel sources.

[0107] The pre-chamber intake system 32 can be supplied by a first fuel source via the first fuel supply line 34 (e.g., first supply line). It can be provided that the first fuel supply line 34 provides hydrogen to the pre-chambers 19.

[0108] Optionally, a pressurizing device 35 and/or a compressor 37 and/or temperature regulating device 36 can be arranged in the first fuel supply line 34. Preferably, it can be provided, that a unidirectional valve 38 is arranged in the first fuel supply line 34.

[0109] Furthermore, a second supply line 39 is provided in the pre-chamber intake system 32, wherein by controlling the control valve 33 the fuel source for the pre-chambers 19 can be changed by choosing the first supply line 34 or the second supply line 39.

[0110] The second supply line 39 can provide pre-chambers 19 by a different fuel as the first supply line 34 or by the same fuel but with a different pressure level.

[0111] Pre-chambers 19 usually serve as ignition intensifiers, in which the fuel-air mixture (that is highly compressed at the end of the compression stroke) is ignited in a relatively small secondary space separate from the main combustion chamber 4 of the cylinders 2. In this case, a main combustion chamber 4 is delimited by the working piston 3, the cylinder liner, and (a flame plate of) the cylinder head 5, wherein the secondary space (the pre-chamber 19) is connected via one or a plurality of transfer passages with the main combustion chamber 4.

[0112] As described above, these pre-chambers 19 are scavenged or filled with fuel gas, air-fuel mixture or air-fuel mixture together with an exhaust gas recirculation (EGR) content during the gas exchange phase in order to improve the ignition and combustion properties in the pre-chamber 19.

[0113] The small second fuel mass flushing the direct fuel injectors 14 cools the direct fuel injectors 14 and removes unwanted deposits in the direct fuel injectors 14, in particular their tip portions which are directly adjacent to the main combustion chamber 4 or protrude into the main combustion chamber 4.

[0114] At full load, large gas engines are usually run lean, at lambda of approx. 1.6 to 2.2, i.e., the amount of air in the mixture corresponds to about twice the stoichiometric amount of air.

[0115] A direct fuel injector 14 is provided to supply a second fuel (e.g., hydrogen) provided by a second gaseous fuel source 15 directly into the main combustion chamber 4.

[0116] In the second operation mode of the internal combustion engine 1, the gas mixing device 12 and/or port injection valve(s) is (are) turned off by a control signal of the control unit 11, wherein only air is passed to the compressor 23.

[0117] The charged air is supplied via the intake manifold 21, the intake ports 6, and the intake valves 7 directly to the main combustion chambers 4, wherein fuel (more precisely hydrogen) is passed to the main combustion chambers 4 via the direct fuel injector 14 by use of the second gaseous fuel source 15 during intake stroke and/or the compression stroke.

[0118] During the compression stroke, the hydrogen and the charged air are mixed in the main combustion chamber 4 at the second operation mode.

[0119] During operation according to first operation mode, the air-fuel-mixture supplied via the at least one intake valve 7 to the main combustion chamber 4 of the internal combustion engine 1 is combusted, wherein the air-fuel-mixture in the main combustion chamber 4 is-preferably intermittently-admixed by a small second fuel mass injected via the direct fuel injectors 14.

[0120] FIG. 4 discloses a schematic diagram of a cylinder pressure during the combustion phases of an internal combustion engine 1, wherein the pressure variation can be seen during the intake, compression, combustion, and exhaust phases.

[0121] Furthermore, the top dead center (TDC) positions and the bottom dead center (BDC) positions of the piston 3 during the combustion cycle are indicated.

[0122] The time windows 17 shown in this diagram indicate possible injection times for the flushing gas via the direct fuel injector 14 during the combustion cycle, wherein it can be seen that an injection of flushing gas preferably takes place during exhaust and/or an intake and/or a compression stroke of the at least one main combustion chamber 4 during operation according to the first operation mode.

[0123] Preferably, it is provided that the control unit 11 is configured to activate the direct fuel injector 14 to supply flushing gas during a period of time in the combustion cycle during operation according to the first operation mode, when a pressure level in the at least one main combustion chamber 4 is below a pressure level upstream of the direct fuel injector 14 in the supply system of flushing gas.

LIST OF USED REFERENCE SIGNS

[0124] 1 internal combustion engine [0125] 2 cylinder [0126] 3 piston [0127] 4 main combustion chamber [0128] 5 cylinder head [0129] 6 intake port [0130] 7 intake valve [0131] 8 exhaust manifold [0132] 9 exhaust valve [0133] 10 actuators [0134] 11 control unit [0135] 12 gas mixing device [0136] 13 spark plug [0137] 14 direct fuel injector [0138] 15 second gaseous fuel source [0139] 16 supply system of flushing gas [0140] 17 time window [0141] 18 switching valve [0142] 19 pre-chamber [0143] 20 main combustion intake system [0144] 21 intake manifold [0145] 22 turbocharger [0146] 23 compressor [0147] 24 turbine [0148] 25 exhaust line [0149] 26 wastegate [0150] 27 compressor bypass valve [0151] 28 air filter [0152] 29 intercooler [0153] 30 throttle valve [0154] 31 flame arrestor [0155] 32 pre-chamber intake system [0156] 33 control valve [0157] 34 first supply line [0158] 35 pressurizing device [0159] 36 temperature regulating device [0160] 37 compressor [0161] 38 unidirectional valve [0162] 39 second supply line