WO2020249277A1

WO2020249277A1 - Method for operating an internal combustion engine with hydrogen, hydrogen internal combustion engine, and motor vehicle

Info

Publication number: WO2020249277A1
Application number: PCT/EP2020/058192
Authority: WO
Inventors: Bruno Barciela Díaz-Blanco; Thomas Malischewski
Original assignee: Man Truck & Bus Se
Priority date: 2019-06-13
Filing date: 2020-03-24
Publication date: 2020-12-17
Also published as: DE102019004189A1

Abstract

The invention relates, inter alia, to a method for operating an internal combustion engine (10) with hydrogen. The method comprises producing of hydrogen autoignition conditions in a combustion chamber (16) of the internal combustion engine (10) by way of load-dependent adaptation of at least one parameter of a combustion air ratio of the internal combustion engine (10), a feed time of the hydrogen, a valve control cam, preferably a closing time, of an air inlet valve (22) to the combustion chamber (16), and a compression ratio of the combustion chamber (16). The method can afford the advantage that autoignition of the hydrogen is made possible in the case of different load conditions by way of constant load-dependent changing of one or more predefined parameters during the operation of the internal combustion engine.

Description

Method for operating an internal combustion engine with hydrogen, hydrogen internal combustion engine and motor vehicle

description

The invention relates to a method for operating an internal combustion engine with hydrogen as, preferably the only fuel, an internal combustion engine operated with hydrogen and a motor vehicle with an internal combustion engine operated with hydrogen.

The diesel engine has been the most efficient internal combustion engine since its invention. For several reasons, the diesel engine is being substituted by "clean" engines today. According to the currently planned C02 EU legislation, a reduction in C02 emissions of at least 20% by 2025 and at least 35% by 2030 compared to a 2019 value This is forcing automobile manufacturers, such as bus and truck manufacturers, to develop other technologies, one of which is based on the combustion of hydrogen in engines, and since hydrogen does not have a carbon atom, it does not burn C02 emissions, so the EU target can be achieved.

One possible solution for the combustion of hydrogen in the engine is based on the Otto engine principle. However, this principle is less efficient than the principle of the diesel engine. Another solution is to burn hydrogen using the diesel principle. By injecting hydrogen fuel in the top dead center area, the engine can achieve a level of efficiency similar to that of the diesel engine. Since the hydrogen is converted faster than the diesel fuel during combustion, a hydrogen engine with high-pressure direct injection can theoretically even achieve a higher degree of efficiency than a diesel engine. A disadvantage with this type of combustion is the ignition of the hydrogen fuel. To solve this problem, diesel fuel can be injected as an ignition source. The self-ignition of the diesel fuel ignites the hydrogen fuel in the combustion chamber. However, this requires complex systems with a diesel tank and a diesel injection system. In addition, the injected pilot quantity causes diesel such as C02.

US Pat. No. 7,162,994 B2 discloses a method for generating a compression ignition environment in a combustion chamber for a gas fuel, e.g. B. hydrogen. The compression ignition environment is created by a glow plug, in the direction of which a pilot quantity of gas fuel is injected. The invention is based on the object of creating an alternative and / or improved technology for operating an internal combustion engine with hydrogen.

The object is achieved by the features of the independent claims. Advantageous further developments are given in the dependent claims and the description.

The invention created a method for operating an internal combustion engine with hydrogen as, preferably the only, fuel. The method includes generating hydrogen auto-ignition conditions in a combustion chamber of the internal combustion engine by load-dependent adaptation of at least one, preferably at least two or three parameters. The parameters can have a combustion air ratio of the internal combustion engine and a feed time (z. B. injection time or injection time) of the hydrogen. The parameters can have a valve control curve, preferably a closing time, an air inlet valve to the combustion chamber and a compression ratio of the combustion chamber. The method can furthermore have a (z. B. high pressure) direct feeding (z. B. direct blowing or direct injection) of the hydrogen into the combustion chamber, preferably in a compression cycle (eg at one end of the compression cycle). The method can include self-ignition of the directly supplied hydrogen in the combustion chamber as a result of the hydrogen self-ignition conditions generated.

The method can offer the advantage that, through constant load-dependent changing of one or more predetermined parameters during operation of the internal combustion engine, auto-ignition of the hydrogen is made possible for each or at least a plurality of engine operating points. It is preferred that at least two parameters are adapted, since in this way a comparatively precise and rapid setting of the desired hydrogen auto-ignition conditions is possible within a comparatively large range. When three or even four parameters are adjusted, even more precise and faster settings of the desired hydrogen auto-ignition conditions can accordingly be made possible within a particularly large range. When adapting two or more parameters, specific couplings between the parameters can also be used, e.g. B. Influences of the valve control curve of the intake valve and the supply of hydrogen on the combustion air ratio.

In contrast to the Otto combustion process, the hydrogen can be supplied towards the end of the compression cycle, so that combustion according to the diesel principle and the associated high efficiency takes place. The invention can combine the advantages of an environmentally friendly fuel (hydrogen) with the most efficient combustion process. This allows maximum utilization of the chemical energies bound in hydrogen. Ignition does not require a pilot amount of diesel fuel to be injected. This means that there are actually no CO2 emissions and the system can be structured more simply. Compared to other technologies for hydrogen combustion, the direct supply and auto-ignition of the hydrogen can prevent knocking problems because the fuel is supplied towards the end of the compression phase. Due to the high turbulence in the combustion chamber, which is not broken down by the late addition of hydrogen, the subsequent diffusion combustion can take place even faster and more efficiently.

The method can expediently be carried out without a pre-injection, without using a glow plug, without using a spark plug and / or without supplying other fuels.

Preferably, the hydrogen can be fed into the combustion chamber at high pressure, e.g. B. with a pressure in a range between 150 bar and 500 bar.

It is possible that the hydrogen is supplied by means of a hydrogen fuel injector which expediently opens into the combustion chamber.

In one exemplary embodiment, the load-dependent adaptation is carried out based on a (e.g. predetermined) characteristic field (e.g. coordinate system, diagram, formula, tables, etc.) that is available for a large number (e.g. at least two, three, four, etc.) .) of different load points and / or different load ranges to set values of at least one, preferably at least two or three, the parameters or combinations of the parameters. Thus, it is possible to react very precisely to different load conditions and to continue to generate hydrogen auto-ignition conditions in the combustion chamber.

In one embodiment, the load-dependent adaptation takes place continuously or continuously during the operation of the internal combustion engine, preferably when a load of the internal combustion engine changes. It can thus be ensured, for example, that hydrogen auto-ignition conditions are present in the combustion chamber at all times during the operation of the internal combustion engine. In one embodiment, the hydrogen auto-ignition conditions are generated in a load range above a low load range of the internal combustion engine, preferably up to and including a full load range of the internal combustion engine. If necessary, ignition of the hydrogen can thus be promoted in an additional and / or alternative manner in the low-load range.

The low load range can expediently have a range between 0% and 30% of a nominal load or maximum load of the internal combustion engine.

In a further embodiment, the method also includes an external ignition of the directly supplied hydrogen in a low-load range of the internal combustion engine, preferably by means of a spark plug. It is possible that, for example, depending on the design of the internal combustion engine, the generation of hydrogen auto-ignition conditions in the low-load range is only possible with great effort and with the most varied of disadvantages, or not at all. Such difficulties can be easily circumvented by the Fremdzün training. The spark plug can for example only be used in the low load range of the internal combustion engine to ignite the hydrogen. Since the service life of the spark plug can be extended.

In a further embodiment, the method includes auto-ignition of the directly supplied hydrogen in a low-load range of the internal combustion engine, preferably supported by a glow plug. The glow plug can, for example, only be used to increase the temperature in the low-load range of the internal combustion engine. This can extend the life of the glow plug.

The hydrogen self-ignition conditions can expediently be adapted to hydrogen self-ignition conditions that are more favorable for self-ignition when a load on the internal combustion engine is reduced. Self-ignition of the hydrogen can thus be ensured even when the load is lower.

The hydrogen self-ignition conditions can preferably be adapted to hydrogen self-ignition conditions that are less favorable to self-ignition when a load on the internal combustion engine is increased. A high load can favor spontaneous ignition anyway. The adaptation made can thus have the effect that thermal and / or mechanical stress on the components is reduced. Alternatively or in addition, depending on the design, the internal combustion engine can be operated in an area with higher efficiency or closer to the respective design point.

In one embodiment variant, the combustion air ratio is increased if the hydrogen auto-ignition conditions are to be adapted more easily by means of the combustion air ratio and / or a load on the internal combustion engine is reduced. Alternatively or additionally, the combustion air ratio can be reduced if the hydrogen auto-ignition conditions are to be adjusted less readily by means of the combustion air ratio and / or a load on the internal combustion engine is increased.

In a further embodiment variant, the hydrogen feed time is adjusted earlier if the hydrogen auto-ignition conditions are to be adapted more readily by means of the feed time and / or a load on the internal combustion engine is reduced. As an alternative or in addition, the hydrogen feed time can be adjusted later if the hydrogen auto-ignition conditions are to be adjusted less readily by means of the feed time and / or a load on the internal combustion engine is increased.

In a further embodiment variant, a closing time of the air inlet valve is adjusted later (e.g. in order to maximize the degree of delivery) when the hydrogen self-ignition conditions are to be adjusted more easily by means of the closing time and / or a load on the internal combustion engine is reduced. Alternatively or additionally, a closing time of the air inlet valve can be adjusted earlier (e.g. in order to minimize the degree of delivery) if the hydrogen auto-ignition conditions are to be adjusted less readily by means of the closing time and / or a load on the internal combustion engine is increased.

In a further embodiment variant, the compression ratio of the combustion chamber is increased when the hydrogen auto-ignition conditions are to be adapted more readily by means of the compression ratio and / or a load on the internal combustion engine is reduced. Alternatively or additionally, the compression ratio of the combustion chamber can be reduced if the hydrogen auto-ignition conditions are to be adjusted less readily by means of the compression ratio and / or a load on the internal combustion engine is increased. In one embodiment, a combustion air ratio is within a range between 1.2 and 3, preferably between 1.8 and 2.2. The combustion air ratio is preferably adjustable within this range.

In a further exemplary embodiment, a hydrogen feed time in the compression cycle is within a range between 60 ° CA before TDC (top dead center of a piston movement of the piston) and 0 ° CA before TDC, preferably between 40 ° CA before TDC and 10 ° CA before TDC . The feed time can preferably be adjusted within this range. The late supply of hydrogen can significantly reduce the risk of knocking problems. High turbulence in the combustion chamber is not reduced by the late supply of hydrogen.

In one embodiment, a closing time of the air inlet valve with respect to the intake stroke is within a range between 20 ° CA before BDC (bottom dead center of a piston movement of the piston) and 80 ° CA after BDC, preferably between 0 ° CA before BDC and 60 ° CA after BDC . The closing time can preferably be adjusted within this range.

In a further embodiment, a compression ratio is within a range between 15 and 26, preferably between 20 and 23. The compression ratio is preferably adjustable within this range.

In one embodiment, the combustion air ratio can be adjusted by adapting the operation of a hydrogen fuel injector. The metering of the directly supplied hydrogen can thus be adjustable.

In a further embodiment variant, the feed time can be adjusted by adapting an operation of a hydrogen fuel injector.

Operation of the hydrogen fuel injector can expediently be adaptable by adapting a control to an electrical control of the hydrogen fuel injector, by means of a variable valve drive and / or by means of a camshaft phaser.

In one embodiment, the valve control curve is adjustable by adjusting an operation of the air inlet valve, e.g. B. by adapting a control to an electrical control of the air inlet valve, by means of a variable valve train and / or by means of a camshaft phaser. In a further embodiment, the compression ratio can be adjusted by means of a variable compression ratio system of the internal combustion engine, preferably by adjusting a piston position at top dead center, for example by means of an adjustable and / or displaceable piston, an adjustable connecting rod and / or an adjustable and / o the movable crankshaft.

In one embodiment, the method further comprises feeding air into a combustion chamber of the internal combustion engine (expediently in an intake stroke) and compressing the air fed in in the combustion chamber (expediently in a compression stroke). Appropriately, the hydrogen can be fed directly into the compressed air, preferably before the end of the compression stroke, for. B. between 60 ° CA before TDC and 0 ° CA before TDC, preferably between 40 ° CA before TDC and 10 ° CA before TDC.

In a further embodiment, a rotary flow, preferably a swirl flow or a tumble flow, is generated for the supplied air in the combustion chamber. The generation of turbulence associated with the rotary flow can generally favor the self-ignition of the hydrogen.

In a further development, the rotary flow in the combustion chamber is greater than or equal to approximately 30 Hz (30 revolutions per second). It was recognized that, in particular from this threshold value (with tolerance), there is a sufficiently high level of turbulence in the combustion chamber to contribute sufficiently to reliable self-ignition of the hydrogen.

In one embodiment, the rotary flow is generated by a duct geometry of at least one air inlet duct which is arranged for supplying air to the combustion chamber. For example, a course of the air inlet channel and an arrangement of an orifice opening of the air inlet channel can lead to the generation of the rotary flow. It is also possible, for example, for fixed or adjustable guide flaps to be arranged in the air inlet duct, which lead to the generation of the rotary flow.

In a further exemplary embodiment, the rotary flow is generated, maintained or intensified by an adapted geometry of the piston head of a piston.

The invention also relates to a hydrogen internal combustion engine or a motor vehicle, preferably a commercial vehicle (for example a truck or bus), with a hydrogen internal combustion engine. The hydrogen internal combustion engine is expedient for carrying out a Method set up as disclosed herein. The hydrogen internal combustion engine expediently has a control unit which is set up to carry out a method as disclosed herein. Optionally, the hydrogen internal combustion engine can have at least one air inlet duct for supplying air into a combustion chamber of the hydrogen internal combustion engine. The at least one air inlet duct is designed to generate a rotary flow, preferably a swirl flow or a turbulent flow, of the air fed into the combustion chamber, preferably greater than or equal to about 30 Hz. Alternatively or additionally, the hydrogen internal combustion engine has a piston for limiting a combustion chamber on the hydrogen engine. The piston is designed to generate, maintain or intensify a rotary flow, preferably a swirl flow or a tumble flow, of the air fed into the combustion chamber, preferably greater than or equal to about 30 Hz. The hydrogen internal combustion engine can achieve the same advantages such as the method disclosed herein for operating an internal combustion engine with hydrogen.

The term “control unit” can preferably refer to electronics (e.g. with microprocessors and data storage) and / or a mechanical controller which, depending on the training, can take on control tasks and / or regulating tasks. Even if the term “control” is used here, it can also expediently include “regulation” or “control with feedback”.

It is also possible to use the method and the internal combustion engine as disclosed herein for passenger vehicles, large engines, all-terrain vehicles, stationary engines, marine engines, and the like.

The preferred embodiments and features of the invention described above can be combined with one another as desired. Further details and advantages of the invention are described below with reference to the accompanying drawing. It shows:

FIG. 1 shows a schematic illustration of an internal combustion engine according to an exemplary embodiment of the present disclosure.

FIG. 1 shows an internal combustion engine 10. Internal combustion engine 10 is designed as a reciprocating internal combustion engine. The internal combustion engine 10 has one or more cylinders. To improve clarity, only one cylinder is shown in FIG. 1. The internal combustion engine 10 is expedient as a single-fuel internal combustion engine designed to operate using hydrogen as fuel. The internal combustion engine 10 can be in a vehicle, e.g. B. a motor vehicle, a rail vehicle or a water vehicle to be included for driving the vehicle. Preferably, the Brennkraftma machine 10 is in a utility vehicle, e.g. B. a truck or bus for driving the utility vehicle. It is also possible, the internal combustion engine 10 in a stationary Ren system z. B. to be used to drive a generator.

The internal combustion engine 10 has at least one air inlet duct 12, at least one exhaust gas outlet duct 14, a combustion chamber 16, a piston 18 and a hydrogen fuel injector 20 for each cylinder.

The air inlet duct 12 opens into the combustion chamber 16. (Charge) air can be supplied to the combustion chamber 16 via the air inlet duct 12. The air inlet duct 12 is arranged in a cylinder head. The cylinder head delimits the combustion chamber 16 from above. An air supply system can be arranged upstream of the air inlet duct 12. Depending on the requirement, the air supply system can, for example, have one or more compressors of a turbocharger assembly, a charge air cooler and / or an exhaust gas recirculation line.

The air inlet duct 12 is expediently designed to supply the air with a rotary flow into the combustion chamber 16. The rotary flow is preferably a swirl flow (rotation about a longitudinal axis of the cylinder). However, it is also possible that the rotary flow is implemented as a T umbleströmung (rotation around a transverse axis of the cylinder). For example, the air inlet channel 12 can be designed as a tangential channel that supplies the air tangentially to the cylinder wall, or as a spiral channel (helically wound inlet channel) for generating the rotary flow. It is also possible, for example, for the air inlet duct 12 to have fixed or adjustable air guide flaps for generating the rotary flow.

An opening of the air inlet channel 12 into the combustion chamber 16 can be opened and closed by means of an air inlet valve 22. The air inlet valve 22 is preferably designed as a poppet valve. The air inlet valve 22 can be operated using any technique. A valve control curve of the air inlet valve 22 is expediently changeable or variable. For example, the air inlet valve 22 can be actuated by means of a variable valve drive 24. The variable valve train 24 may be a power transmission device such. B. a plunger, ok

have a rocker arm or a rocker arm, and a camshaft. The power transmission device can establish an operative connection between the camshaft and the air inlet valve 22. The valve control curve of the air inlet valve 22 can be adjusted, for example, by means of a camshaft phaser for the camshaft and / or a sliding cam system for the camshaft. A closing time of the air inlet valve 22 can preferably be adjustable within a range between 20 ° CA before UT and 80 ° CA after UT, preferably between 0 ° CA before UT and 60 ° CA after UT. The adjustability of the valve control curve of the air intake valve 22 can advantageously be used to generate auto-ignition conditions for the hydrogen as a function of a load on the internal combustion engine 10.

After the combustion, the exhaust gas leaves the combustion chamber 16 through the exhaust gas outlet channel 14, which is opened by means of an exhaust gas outlet valve 26. The exhaust gas outlet valve 26 can be designed, for example, as a poppet valve. The exhaust outlet channel 14 is arranged in the cylinder head. An exhaust system can be arranged downstream of the exhaust gas outlet duct 14. The exhaust system can have, for example, one or more exhaust gas turbines of a turbocharger assembly.

The piston 18 is arranged to be movable back and forth in the cylinder. The piston 18 is connected to a crankshaft 30 via a connecting rod 28. The piston 18 limits the combustion chamber 16 downward. In detail, a piston head 32 of the piston 18 delimits the combustion chamber 16 downwards.

The piston head 32 is expediently designed to promote a rotary flow, preferably a swirl flow, in the combustion chamber 16. For this purpose, the piston crown 32 can for example have a piston recess and / or surface contour that is adapted to the geometry of the at least one air inlet channel 12. The optimized design of the piston crown 32 allows the existing flow in the combustion chamber 16 to be forced in a desired (rotational) direction during the compression phase and thus to increase the turbulence.

A rotational flow-generating, preferably swirl-generating, geometry of the air inlet duct 12 and a rotational flow-maintaining, preferably swirling, or rotational flow-enhancing, preferably swirl-enhancing, geometry of the piston bottom 32 work together in such a way that a swirl flow of at least 30 Hz, that is 30 revolutions per second, results. Such a high level of turbulence in the combustion chamber 16 favors the generation of auto-ignition conditions for the hydrogen.

The internal combustion engine 10 can furthermore have a variable compression ratio system 34 (also called VCR system: variable compression ratio system). Expediently, the variable compression ratio system 34 enables a discrete or continuous change in the compression ratio e by adapting a piston position of the piston 18 at top dead center. For example, the variable compression ratio system 34 may be implemented by adjustability of the connecting rod 28. The connecting rod 28 can be changeable in length. For example, the connecting rod 28 can be designed as a telescopic connecting rod. The variable compression ratio system 34 can also be implemented differently. For example, an adjustment and / or a displacement of the piston 18 may be possible. Alternatively, for example, an adjustment and / or displacement of the crankshaft 30 may be possible. The compression ratio e can preferably be adjustable within a range between 15 and 26, preferably between 18 and 23. The adjustability of the compression ratio e can advantageously be used to generate self-ignition conditions for the hydrogen as a function of a load on the internal combustion engine 10.

The hydrogen fuel injector 20 is designed to supply hydrogen as fuel directly into the combustion chamber 16, preferably to inject it. The feed takes place at a high pressure, for example in a range between 150 and 500 bar. The what hydrogen fuel injector 20 can be operated in any way, for example by means of an electromagnet or mechanically z. B. by means of a cam control of the variable valve drive 24.

Expediently, a feed time of the hydrogen fed by the hydrogen fuel injector 20 into the combustion chamber 16 can be adjusted. For example, the feed time can be brought about by means of the variable valve drive 24 or a changed control of the hydrogen fuel injector 20. The hydrogen feed time can preferably be adjusted within a range between 60 ° CA before TDC and 0 ° CA before TDC, preferably between 40 ° CA before TDC and 10 ° CA before TDC. The adjustability of the feed time can be used in an advantageous manner to generate self-ignition conditions for the hydrogen as a function of a load on the internal combustion engine 10. It is possible for an amount of fuel supplied by the hydrogen fuel injector 20 to be adjustable. The metering of the amount of fuel can be effected, for example, by changing an opening duration of the hydrogen fuel injector 20. For example, the change in the amount of fuel supplied can be brought about by means of a variable valve drive or a changed control of the hydrogen fuel injector 20. By changing the amount of fuel, a combustion air ratio l or an air-fuel ratio AFR can be adjusted appropriately. The combustion air ratio l can preferably be adjustable within a range between 1, 2 and 3, preferably between 1.8 and 2.2. The adjustability of the combustion air ratio l can also advantageously be used to generate self-ignition conditions for the hydrogen as a function of a load on the internal combustion engine 10.

The internal combustion engine 10 can also have an expedient electronic control unit 36. The control unit 36 is designed to operate the internal combustion engine 10. The control unit 36 may be in communication with the variable valve train 24, the hydrogen fuel injector 20, and / or the variable compression ratio system 34.

In an intake stroke, air is fed into the combustion chamber 16 through the air intake duct 12 and the open air intake valve 22. The piston 18 moves from top dead center to bottom dead center. In the compression stroke, the air supplied in the combustion chamber 16 is compressed. The piston 18 moves from bottom dead center to top dead center. In contrast to an Otto combustion process, the hydrogen is supplied towards the end of the compression cycle. The hydrogen is fed directly into the combustion chamber 16 through the hydrogen fuel injector 20. Shortly after the supply, the hydrogen ignites by self-ignition. The hydrogen burns according to the diffusion principle known for diesel engines, which for thermodynamic reasons is associated with a high degree of efficiency. The piston 18 is accelerated from top dead center to bottom dead center and drives the crankshaft 30. In the subsequent exhaust stroke, the resulting exhaust gas is pushed out of the combustion chamber 16 through the opened exhaust gas outlet valve 26 into the exhaust gas outlet duct 14. The piston 18 moves from bottom dead point to top dead center. The high level of turbulence in the combustion chamber 16 brought about by the geometry of the air inlet duct 12 and the piston crown 32 promotes auto-ignition and the combustion of the hydrogen. Additionally or alternatively, a high basic compression ratio, e.g. B. in a range between 20 and 23 also favor the auto-ignition of hydrogen.

The internal combustion engine 10 can furthermore be operated by the control unit 36 such that hydrogen supplied into the combustion chamber 16 is caused to self-ignite. For this purpose, the control unit 36 is designed in such a way that, during operation of the internal combustion engine 10, depending on a load on the internal combustion engine 10, one or more parameters relating to the air inlet valve 22, the hydrogen fuel injector 20 and / or the variable compression ratio system 34 are always present be adjusted. The parameter or parameters are adapted in such a way that the generation of auto-ignition conditions for the hydrogen in the combustion chamber 16 is ensured. For this purpose, the control unit 36 can have one or more characteristic maps, for example in the form of coordinate systems, diagrams, formulas, tables, etc., for example. The at least one map can each load or each operating point of the internal combustion engine 10 a parameter to be set with respect to a valve control curve of the air inlet valve 22, a supply time of hydrogen by the hydrogen fuel injector 20, a supply amount of hydrogen by the hydrogen fuel injector 20 and / or the Assign compression ratio e by the variable compression ratio system 34.

With regard to the combustion air ratio l can, for. B. its increase lead to the fact that the auto-ignition conditions for the hydrogen in the combustion chamber 16 are more favorable to auto-ignition. However, z. B. a reduction in the combustion air ratio l lead to the fact that the auto-ignition conditions for the hydrogen in the combustion chamber 16 are less likely to auto-ignite. The effects can be different depending on other operating parameters of the internal combustion engine 10 and from the current combustion air ratio l.

With regard to the point in time at which the hydrogen is supplied, an earlier adjustment can mean that the auto-ignition conditions in the combustion chamber 16 become more easily ignitable. This may be necessary for example when the load on the internal combustion engine 10 is reduced. Adjusting the time at which the hydrogen is supplied to later can result in the auto-ignition conditions in the combustion chamber 16 becoming less favorable for auto-ignition. A later point in time for the hydrogen to be added can promote earlier spontaneous ignition. Depending on the design of the hydrogen fuel injector 20, it is useful to take into account that the desired amount of fuel for the desired engine torque is achieved.

With regard to the closing time of the air inlet valve 22, an adjustment to later in order to maximize the degree of delivery can lead to the self-ignition conditions for the hydrogen in the combustion chamber 16 becoming more readily self-igniting. By contrast, an earlier adjustment to minimize the degree of delivery can lead to the self-ignition conditions for the hydrogen in the combustion chamber 16 becoming less readily self-igniting. In principle, control times with a very early closing time of the air inlet valve before bottom dead center (up to 20 ° CA before BDC) can lead to a rapid reduction in turbulence during the compression stroke (the compression phase takes longer) and the amount of air in the Combustion chamber 16 is limited. A small amount of air in the combustion chamber 16 causes the air combustion ratio to become lower. This inhibits self-ignition.

With regard to the change in the compression ratio e, an increase in the compression ratio e favors auto-ignition by positively influencing the auto-ignition conditions in the combustion chamber 16. A reduction in the compression ratio e, on the other hand, leads to less auto-ignition-friendly auto-ignition conditions in the combustion chamber 16.

For example, reducing the load on the internal combustion engine 10 can lead to the control unit 36 adjusting the closing time of the air inlet valve 22 later, reducing the combustion air ratio l, increasing the compression ratio e and / or adjusting the hydrogen feed time earlier in order to continue to provide adequate auto-ignition conditions for the hydrogen in the combustion chamber 16 to be generated.

It goes without saying that the measures specified here (high rotary flow generation in the combustion chamber, high basic compression ratio, adaptability of the valve control curve of the intake valve, adaptability of the combustion air ratio, adaptability of the time of direct hydrogen supply and adaptability of the compression ratio) individually, partly in any combination with one another or can be fully implemented to produce the auto-ignition conditions for the hydrogen in the combustion chamber 16. Depending on the design of the internal combustion engine 10, it may be possible to generate auto-ignition conditions for hydrogen in the combustion chamber 16 in any load range, that is to say even at low loads. However, it is possible that the auto-ignition conditions are only generated in a load range above a low-load range of the internal combustion engine. For example, in the low-load range, the supplied hydrogen can be spark-ignited, for example by means of a spark plug. It is also possible for the hydrogen to auto-ignite even in the low-load range, for example with the help of a glow plug.

The invention is not restricted to the preferred exemplary embodiments described above. Rather, a large number of variants and modifications are possible which also make use of the inventive concept and therefore fall within the scope of protection. In particular, the invention also claims protection for the subject matter and the features of the subclaims independently of the claims referred to. In particular, the individual features of independent claim 1 are disclosed independently of one another. In addition, the features of the subclaims are also disclosed independently of all the features of independent claim 1. All range specifications herein are to be understood as disclosed in such a way that all values falling within the respective range are disclosed individually, e.g. B. also as each preferred narrower external borders of the respective Be rich.

List of reference symbols

10 internal combustion engine

12 air inlet duct

14 Exhaust outlet duct

16 combustion chamber

18 pistons

20 Hydrogen fuel! nj e ktor

22 Air inlet valve

24 Variable valve train

26 Exhaust outlet valve

28 connecting rods

30 crankshaft

32 piston crown

34 Variable Compression Ratio System

36 control unit

Claims

1. A method for operating an internal combustion engine (10) with hydrogen as, preferably single, fuel, comprising:

Generation of hydrogen auto-ignition conditions in a combustion chamber (16) of the internal combustion engine (10) by load-dependent adaptation of at least one, preferably at least two or three, parameters of:

a combustion air ratio of the internal combustion engine (10), a supply time of the hydrogen,

a valve control curve, preferably a closing time, of an air inlet valve (22) to the combustion chamber (16),

a compression ratio of the combustion chamber (16);

Feeding the hydrogen directly into the combustion chamber (16), preferably in a compression stroke; and

Autoignition of the directly supplied hydrogen in the combustion chamber (16) by the generated hydrogen autoignition conditions.

2. The method of claim 1, wherein:

the load-dependent adaptation takes place based on a characteristic map which provides different values to be set of at least one, preferably at least two or three, of the parameters or combinations of the parameters for a plurality of different load points and / or different load ranges; and / or the load-dependent adaptation takes place continuously or continuously during operation of the internal combustion engine (10), preferably when a load on the internal combustion engine (10) changes.

3. The method of claim 1 or claim 2, wherein:

the generation of the hydrogen auto-ignition conditions is carried out in a load range above a low load range of the internal combustion engine (10), preferably up to and including a full load range of the internal combustion engine (10).

4. The method according to any one of the preceding claims, further comprising:

External ignition of the directly supplied hydrogen in a low-load range of the internal combustion engine (10), preferably by means of a spark plug, or

Auto-ignition of the directly supplied hydrogen in a low-load range of the internal combustion engine (10), preferably supported by a glow plug.

5. The method according to any one of the preceding claims, wherein:

the combustion air ratio is increased when the hydrogen self-ignition conditions are to be adapted more readily by means of the combustion air ratio and / or a load on the internal combustion engine (10) is reduced; and or

the combustion air ratio is reduced when the hydrogen self-ignition conditions are to be adjusted less readily by means of the combustion air ratio and / or a load on the internal combustion engine (10) is increased.

6. The method according to any one of the preceding claims, wherein:

the supply time of the hydrogen is adjusted earlier if the hydrogen auto-ignition conditions are to be adapted more readily by means of the supply time and / or a load on the internal combustion engine (10) is reduced; and or

the supply time of the hydrogen is adjusted later if the hydrogen auto-ignition conditions are to be adjusted less readily by means of the supply time and / or a load on the internal combustion engine (10) is increased.

7. The method according to any one of the preceding claims, wherein:

a closing time of the air inlet valve (22) is adjusted to later when the hydrogen auto-ignition conditions are to be adapted more readily by means of the closing time and / or a load on the internal combustion engine (10) is reduced; and or

a closing time of the air inlet valve (22) is adjusted earlier if the hydrogen self-ignition conditions are to be adjusted less readily by means of the closing time and / or a load on the internal combustion engine (10) is increased.

8. The method according to any one of the preceding claims, wherein:

the compression ratio of the combustion chamber (16) is increased when the hydrogen auto-ignition conditions are to be adapted to be more readily ignition-friendly by means of the compression ratio and / or a load on the internal combustion engine (10) is reduced; and or the compression ratio of the combustion chamber (16) is reduced when the hydrogen auto-ignition conditions are to be adapted less readily by means of the compression ratio and / or a load on the internal combustion engine (10) is increased.

9. The method according to any one of the preceding claims, wherein:

the combustion air ratio is within a range between 1, 2 and 3, preferably between 1, 8 and 2.2, adjustable; and or

the time at which the hydrogen is fed in in the compression stroke can be adjusted within a range between 60 ° CA before TDC and 0 ° CA before TDC, preferably between 40 ° CA before TDC and 10 ° CA before TDC; and or

a closing time of the air inlet valve (22) can be adjusted within a range between 20 ° CA before UT and 80 ° CA after UT, preferably between 0 ° CA before UT and 60 ° CA after UT; and or

the compression ratio within a range between 15 and 26, preferably between 20 and 23, is adjustable.

10. The method according to any one of the preceding claims, wherein:

the combustion air ratio is adjustable by adapting an operation of a hydrogen fuel injector (20); and or

the feed time can be adjusted by adapting an operation of a hydrogen fuel injector (20); and or

the valve control curve is adjustable by adjusting an operation of the air inlet valve (22); and or

the compression ratio is adjustable by means of a variable compression ratio system (34) of the internal combustion engine (10), preferably by adapting a piston position at top dead center, for example by means of an adjustable or displaceable piston (18), an adjustable connecting rod (28) and / or an adjustable or displaceable crankshaft (30).

11. The method according to any one of the preceding claims, further comprising:

Supplying air into a combustion chamber (16) of the internal combustion engine (10); Compressing the supplied air in the combustion chamber (16),

whereby the hydrogen is fed directly into the compressed air.

12. The method of claim 11, wherein: a rotary flow, preferably a swirl flow or a tumble flow, is generated for the supplied air in the combustion chamber (16).

13. The method of claim 12, wherein:

the rotary flow in the combustion chamber (16) is greater than or equal to approximately 30 Hz.

14. The method of claim 12 or claim 13, wherein:

the rotary flow is generated through a duct geometry of at least one air inlet duct (12) which is arranged for supplying air to the combustion chamber (16); and or

the rotary flow is generated, maintained or amplified by an adapted geometry of a piston head (32) egg nes piston (18).

15. Hydrogen internal combustion engine (10) or motor vehicle, preferably a commercial vehicle, with a hydrogen internal combustion engine (10), wherein:

wherein the hydrogen internal combustion engine (10) and / or a control unit (36) of the hydrogen internal combustion engine (10) is set up to carry out a method according to one of the preceding claims;

wherein the hydrogen internal combustion engine (10) optionally has:

at least one air inlet duct (12) for feeding air into a combustion chamber (16) of the hydrogen internal combustion engine (10), which is designed to supply a rotary flow, preferably a swirl flow or a tumble flow, to the air fed into the combustion chamber (16) generate, preferably greater than or equal to about 30 Hz; and or

a piston (18) for delimiting a combustion chamber (16) of the hydrogen internal combustion engine (10), which is designed to generate a rotary flow, preferably a swirl flow or a tumble flow, of the air to be fed into the combustion chamber (16), to hold or to amplify, preferably greater than or equal to approx. 30 Hz.