DE102019004189A1 - Method for operating an internal combustion engine with hydrogen, hydrogen internal combustion engine and motor vehicle - Google Patents

Abstract

The invention relates to u. a. a method for operating an internal combustion engine (10) with hydrogen. The method includes generating hydrogen auto-ignition conditions in a combustion chamber (16) of the internal combustion engine (10) by load-dependent adaptation of at least one parameter of a combustion air ratio of the internal combustion engine (10), a hydrogen supply time, a valve control curve, preferably a closing time, an air inlet valve (22) to the combustion chamber (16) and a compression ratio of the combustion chamber (16). 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 under different load conditions.

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 replaced by “clean” engines today. According to the currently planned CO2 EU legislation, a reduction in CO2 emissions of at least 20% by 2025 and at least 35% by 2030 compared to a value of 2019 is to be achieved. This forces manufacturers of motor vehicles such. B. bus and truck manufacturers to develop other technologies. One of these technologies is based on the combustion of hydrogen in the engine. Since hydrogen fuel has no carbon atom, burning it does not cause any CO2 emissions. The EU target can thus 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 present in the combustion chamber. However, this requires complex systems with a diesel tank and a diesel injection system. In addition, the injected pilot quantity of diesel again causes CO2.

The US 7,162,994 B2 discloses a method of creating an autoignition environment in a combustion chamber for a gaseous fuel, e.g. B. hydrogen. The auto-ignition environment is created by a glow plug towards which a pilot amount of gas fuel is injected.

The invention is based on the object of creating an alternative and / or improved technique for operating an internal combustion engine with hydrogen.

The object is achieved by the features of the independent claims. Advantageous 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 include a combustion air ratio of the internal combustion engine and a feed time (e.g. injection time or injection time) of the hydrogen. The parameters can include 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 include (for example high-pressure) direct feeding (for example direct blowing in or direct injection) of the hydrogen into the combustion chamber, preferably in a compression stroke (e.g. at one end of the compression stroke). The method may include autoignition of the directly supplied hydrogen in the combustion chamber by the generated hydrogen autoignition conditions.

The method can offer the advantage that by constantly changing one or more predetermined parameters as a function of the load 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 adapted, it is accordingly possible to set the desired hydrogen auto-ignition conditions even more precisely and quickly 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 added towards the end of the compression stroke so that combustion takes place according to the diesel principle and the associated high degree of efficiency. The invention can take advantage of an environmentally friendly fuel (hydrogen) with the most efficient Combine combustion process. This enables maximum utilization of the chemical energies bound in hydrogen. Ignition does not require the injection of a pilot amount of diesel fuel. 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 reduced by the late supply 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 be set values of at least one, preferably at least two or three, the parameters or combinations of parameters provides. 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 exemplary embodiment, the load-dependent adaptation takes place continuously or continuously during operation of the internal combustion engine, preferably when a load on 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 or take place 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 further comprises spark 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 avoided in a simple manner by the spark ignition. The spark plug can, for example, only be used to ignite the hydrogen in the low-load range of the internal combustion engine. This can extend the service life of the spark plug.

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 service 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 decreasing.

The hydrogen self-ignition conditions can preferably be adapted to hydrogen self-ignition conditions that are less prone 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 additionally, 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 readily by means of the combustion air ratio and / or a load on the internal combustion engine is reduced. As an alternative or in addition, 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 supply time can be 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 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 auto-ignition conditions are to be adapted 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. 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 if the hydrogen self-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. As an alternative or in addition, 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 stroke 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 another embodiment, a compression ratio is within a range between 15 and 26th , preferably between 20th and 23. Preferably, the compression ratio is adjustable within this range.

In one embodiment variant, the combustion air ratio can be adjusted by adapting the operation of a hydrogen fuel injector. The metering of the directly supplied hydrogen can 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 of 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 of an electrical control of the air inlet valve, by means of a variable valve drive and / or by means of a camshaft phaser.

In a further exemplary 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 / or displaceable 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). The hydrogen can expediently be fed directly into the compressed air, preferably at the end of the compression stroke, e.g. 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 in order 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 duct and an arrangement of an orifice opening of the air inlet duct 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 reinforced 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 utility vehicle (e.g. truck or bus), with a hydrogen internal combustion engine. The hydrogen internal combustion engine is expediently set up to carry out a method 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 feeding 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 tumble flow, of the air fed into the combustion chamber, preferably greater than or equal to approx. 30 Hz the hydrogen internal combustion 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 approx. 30 Hz. The hydrogen internal combustion engine can achieve the same advantages 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 microprocessor (s) and data memory) and / or a mechanical controller which, depending on its design, can take on control tasks and / or regulation 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 cars, large engines, all-terrain vehicles, stationary engines, marine engines, etc.

• 1 eine schematische Darstellung einer Brennkraftmaschine gemäß einem Ausführungsbeispiel der vorliegenden Offenbarung.

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:

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

The 1 shows an internal combustion engine 10 . The 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 in 1 shown. The internal combustion engine 10 is expediently designed as a single-fuel internal combustion engine for operation 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 watercraft to drive the vehicle. The internal combustion engine is preferred 10 in a commercial vehicle, e.g. B. a truck or omnibus, for driving the commercial vehicle. It is also possible to use the internal combustion engine 10 in a stationary system z. B. to be used to drive a generator.

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

The air inlet duct 12 opens into the combustion chamber 16 . Via the air inlet duct 12 can (charge) air to the combustion chamber 16 are fed. The air inlet duct 12 is arranged in a cylinder head. The cylinder head delimits the combustion chamber 16 from above. Upstream of the air inlet duct 12 an air supply system can be arranged. 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 feed the air with a rotary flow into the combustion chamber 16 feed. 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 tumble flow (rotation around a transverse axis of the cylinder). For example, the air inlet duct 12 be designed as a tangential channel, which supplies the air tangentially to the cylinder wall, or as a spiral channel (spirally wound inlet channel) for generating the rotary flow. It is also possible, for example, that the air inlet duct 12 Has fixed or adjustable air guide flaps to generate the rotary flow.

An orifice of the air inlet duct 12 into the combustion chamber 16 is by means of an air inlet valve 22nd can be opened and closed. The air inlet valve 22nd is preferably designed as a poppet valve. The air inlet valve 22nd can be operated using any technology. A valve control curve of the air inlet valve is useful 22nd changeable or variable. For example, the air inlet valve 22nd by means of a variable valve train 24 be operated. The variable valve train 24 can be a power transmission device such. B. have a tappet, a rocker arm or a rocker arm, and a camshaft. The power transmission device can have an operative connection between the camshaft and the air inlet valve 22nd produce. An adjustment of the valve control curve of the air inlet valve 22nd can be effected, 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 can preferably be 22nd 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 inlet valve 22nd can be used in an advantageous manner to set auto-ignition conditions for the hydrogen as a function of a load on the internal combustion engine 10 to create.

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

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

The piston crown 32 is expediently designed to have a rotary flow, preferably a swirl flow, in the combustion chamber 16 to favor. The piston crown can do this 32 for example one to the geometry of the at least one air inlet channel 12 have adapted piston bowl and / or surface contour. The optimized design of the piston crown 32 allows the existing flow in the combustion chamber during the compression phase 16 To force in a desired (turning) direction and thus to increase the turbulence.

A rotational flow-generating, preferably swirl-generating, geometry of the air inlet channel expediently acts 12 and a rotational flow-retaining, preferably swirl-retaining, or rotational flow-reinforcing, preferably swirl-reinforcing, geometry of the piston head 32 together in such a way that a swirl flow of at least 30 Hz, i.e. 30 revolutions per second, results. Such a high level of turbulence in the combustion chamber 16 favors the creation of auto-ignition conditions for the hydrogen.

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

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

Expediently, a feed time can be made by the hydrogen fuel injector 20th supplied hydrogen into the combustion chamber 16 be adjustable. For example, the feed time can be determined by means of the variable valve drive 24 or a changed control of the hydrogen fuel injector 20th be effected. The time at which the hydrogen is supplied 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 advantageously be used to set auto-ignition conditions for the hydrogen as a function of a load on the internal combustion engine 10 to create.

It is possible to get one through the hydrogen fuel injector 20th The amount of fuel supplied is adjustable. The metering of the amount of fuel can be done, for example, by changing an opening time of the hydrogen fuel injector 20th be effected. For example, the amount of fuel supplied can be changed by means of a variable valve drive or a changed control of the hydrogen fuel injector 20th be effected. By changing the amount of fuel, a combustion air ratio λ or an air-fuel ratio AFR (for air-fuel ratio) can expediently be adapted. The combustion air ratio λ 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 λ can also advantageously be used to set auto-ignition conditions for the hydrogen as a function of a load on the internal combustion engine 10 to create.

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

In an intake stroke, air is drawn through the air intake duct 12 and the open air inlet valve 22nd into the combustion chamber 16 fed. The piston 18th moves from top dead center to bottom dead center. In the compression stroke, the air supplied is in the combustion chamber 16 condensed. The piston 18th 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 injected directly through the hydrogen fuel injector 20th into the combustion chamber 16 fed. Shortly after being fed in, the hydrogen ignites by itself. The hydrogen burns according to the diffusion principle known for diesel engines, which for thermodynamic reasons is associated with a high degree of efficiency. In doing so, the piston 18th accelerates from top dead center to bottom dead center and thereby drives the crankshaft 30th at. In the subsequent exhaust stroke, the resulting exhaust gas is discharged from the combustion chamber 16 through the open exhaust gas outlet valve 26th into the exhaust outlet duct 14th pushed out. The piston 18th moves from bottom dead center to top dead center.

This is due to the geometry of the air inlet duct 12 and the piston crown 32 caused high levels of turbulence in the combustion chamber 16 favors auto-ignition and combustion of the hydrogen. Additionally or alternatively, a high basic compression ratio, e.g. B. in a range between 20th and 23 also favor the auto-ignition of the hydrogen.

The internal combustion engine 10 can also from the control unit 36 operated so that in the combustion chamber 16 supplied hydrogen is made to auto-ignite. The control unit 36 is designed for this purpose in such a way that during operation of the internal combustion engine 10 as a function of a load on the internal combustion engine 10 constantly one or more parameters related to the air inlet valve 22nd , the hydrogen fuel injector 20th and / or the variable compression ratio system 34 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 guaranteed. The control unit 36 for example, one or more maps, for example in the form of coordinate systems, diagrams, formulas, tables, etc. have. The at least one map can be any load or any operating point of the internal combustion engine 10 a parameter to be set in relation to a valve control curve of the air inlet valve 22nd , a supply timing of hydrogen by the hydrogen fuel injector 20th , a supply amount of hydrogen by the hydrogen fuel injector 20th and / or the compression ratio ε through the variable compression ratio system 34 assign.

With regard to the combustion air ratio λ, z. B. increasing it lead to the auto-ignition conditions for the hydrogen in the combustion chamber 16 become more prone to spontaneous ignition. However, z. B. a reduction in the combustion air ratio λ lead to the auto-ignition conditions for the hydrogen in the combustion chamber 16 become less prone to spontaneous ignition. The effects can be a function of further operating parameters of the internal combustion engine 10 and be different depending on the current combustion air ratio λ.

With regard to the hydrogen supply timing, an earlier adjustment can result in the auto-ignition conditions in the combustion chamber 16 become more prone to spontaneous ignition. This can be done, for example, when the load on the internal combustion engine is reduced 10 to be necessary. Adjusting the timing of the supply of hydrogen later can lead to the auto-ignition conditions in the combustion chamber 16 become less prone to spontaneous ignition. A later point in time for the hydrogen to be supplied can favor earlier auto-ignition. Depending on the design of the hydrogen fuel injector 20th It is advisable to take into account that the desired fuel quantity for the desired engine torque is achieved.

Regarding the closing timing of the air intake valve 22nd Adjustment later to maximize the degree of delivery can lead to the auto-ignition conditions for the hydrogen in the combustion chamber 16 become more prone to spontaneous ignition. On the other hand, an earlier adjustment to minimize the degree of delivery can lead to the auto-ignition conditions for the hydrogen in the combustion chamber 16 become less prone to spontaneous ignition. 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 also to the amount of air in the combustion chamber 16 is limited. A small amount of air in the combustion chamber 16 leads to the fact that the air combustion ratio. becomes lower. This inhibits self-ignition.

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

For example, the load on the internal combustion engine can be reduced 10 cause the control unit 36 the closing time of the air inlet valve 22nd adjusted after later, the combustion air ratio λ is reduced, the compression ratio ε increased and / or the feed time of the hydrogen adjusted earlier in order to continue to have sufficient auto-ignition conditions for the hydrogen in the combustion chamber 16 to create.

It goes without saying that the measures specified herein (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) are implemented individually, partially in any combination with one another or completely can adjust the auto-ignition conditions for the hydrogen in the combustion chamber 16 to create.

Depending on the design of the internal combustion engine 10 it may be possible to have auto-ignition conditions for hydrogen in the combustion chamber in every load range, including at low loads 16 to create. 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 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 the respectively preferred narrower outer boundaries of the respective area.

List of reference symbols

10

Internal combustion engine

12

Air inlet duct

14th

Exhaust outlet duct

16

Combustion chamber

18th

piston

20th

Hydrogen fuel injector

22nd

Air inlet valve

24

Variable valve train

26th

Exhaust outlet valve

28

Connecting rod

30th

crankshaft

32

Piston crown

34

Variable compression ratio system

36

Control unit

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 7162994 B2 [0004]

Claims (15)

Method for operating an internal combustion engine (10) with hydrogen as, preferably the only 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 hydrogen supply time, - 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. Procedure according to 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. Procedure according to Claim 1 or Claim 2 wherein: the generation of the hydrogen auto-ignition conditions is performed 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). Method according to 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. Method according to one of the preceding claims, wherein: the combustion air ratio is increased when the hydrogen auto-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 auto-ignition conditions are to be adapted less readily by means of the combustion air ratio and / or a load on the internal combustion engine (10) is increased. Method according to one of the preceding claims, wherein: the feed time of the hydrogen 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 (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. Method according to one of the preceding claims, wherein: a closing point in time of the air inlet valve (22) is adjusted to later when the hydrogen self-ignition conditions are to be adapted more readily by means of the closing point in 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 auto-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. Method according to 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 more readily 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 if 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. Method according to one of the preceding claims, wherein: the combustion air ratio is adjustable within a range between 1.2 and 3, preferably between 1.8 and 2.2; and / or the time at which the hydrogen is supplied in the compression stroke within a range between 60 ° CA before TDC and 0 ° CA before TDC, preferably between 40 ° CA before TDC and 10 ° CA before TDC, is adjustable; 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 can be adjusted within a range between 15 and 26, preferably between 20 and 23. Method according to one of the preceding claims, wherein: the combustion air ratio is adjustable by adjusting an operation of a hydrogen fuel injector (20); and or the feed time can be adjusted by adjusting 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 can be adjusted by means of a variable compression ratio system (34) of the internal combustion engine (10), preferably by adjusting 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). Method according to 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), the hydrogen being supplied directly into the compressed air. Procedure according to Claim 11 , wherein: a rotary flow, preferably a swirl flow or a tumble flow, of the supplied air is generated in the combustion chamber (16). Procedure according to Claim 12 , wherein: the rotary flow in the combustion chamber (16) is greater than or equal to approximately 30 Hz. Procedure according to Claim 12 or Claim 13 wherein: the rotary flow is generated by 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 intensified by an adapted geometry of a piston head (32) of a piston (18). 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 generate a rotary flow, preferably a swirl flow or a tumble flow, of the air fed into the combustion chamber (16) , 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 or maintain a rotary flow, preferably a swirl flow or a tumble flow, of the air supplied into the combustion chamber (16) to be amplified, preferably greater than or equal to about 30 Hz.

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