Internal combustion engine system, and method for providing kinetic energy

Abstract

The invention relates to an internal combustion engine system (1) for providing kinetic energy by combusting a gaseous fuel, preferably molecular hydrogen (H₂), in an internal combustion engine (2). The system comprises: - the internal combustion engine (2); - a fuel line (34) which supplies the gaseous fuel at an output pressure; - a fuel preheating device (13) which heats the fuel to the required supply temperature; - a fuel supply element (3) which injects the preheated fuel into the internal combustion engine; - a combustion air supply element which carries an oxygen-containing gas into the internal combustion engine; - a fuel compression device (16) which compresses the gaseous fuel to a defined supply pressure before the fuel is supplied.

Description

[0001] Internal combustion engine system and method for providing kinetic energy

[0002] The invention relates to an internal combustion engine system for providing kinetic energy by combustion of a gaseous fuel, preferably molecular hydrogen (H2), in an internal combustion engine, comprising:

[0003] the internal combustion engine,

[0004] a fuel line for supplying the gaseous fuel at an outlet pressure,

[0005] a fuel preheating device for preheating the gaseous fuel to a supply temperature,

[0006] a fuel supply element for supplying the gaseous fuel to the internal combustion engine and

[0007] a combustion air supply element for supplying an oxygen-containing gas to the internal combustion engine.

[0008] The invention also relates to a device for providing electrical energy, containing the internal combustion engine system, and a vehicle containing the internal combustion engine system.

[0009] Furthermore, the invention relates to a method for providing kinetic energy by combustion of a gaseous fuel, preferably molecular hydrogen (H2), using the internal combustion engine system.

[0010] Prior art has shown heat engine processes with injection systems which increase efficiency or power output by preheating a liquid or gaseous fuel.

[0011] WO 2004 / 046535 Al, for example, discloses the preheating of hydrogen to increase the efficiency of hydrogen-powered combustion engines. The preheated hydrogen is injected into the combustion engine at an injection pressure between 100 bar and 500 bar. In WO 2004 / 046535 Al, the hydrogen is provided in a hydrogen storage tank and is primarily in liquid form, which allows the necessary injection pressure to be built up relatively easily directly in the hydrogen storage tank. However, storing hydrogen in liquid form has many disadvantages, as extremely low temperatures are required for liquefaction. This results in high energy consumption during liquefaction and also necessitates extremely good thermal insulation of the tank.

[0012] Building up the injection pressure directly in the storage tank, especially when the fuel is in gaseous form, has the further disadvantage that the pressure in the storage tank decreases as its fill level decreases. If the pressure in the storage tank drops, the maximum possible injection pressure also decreases, resulting in less fuel being delivered to the engine in a single injection cycle and consequently a reduction in engine power.

[0013] In contrast, the object of the present invention is to alleviate or eliminate at least some disadvantages of the prior art. The invention preferably aims to provide an internal combustion engine system for gaseous fuels in which the power output of the internal combustion engine does not depend on the outlet pressure of the gaseous fuel.

[0014] Therefore, in the internal combustion engine system according to the invention, a fuel compression device is provided for compressing the gaseous fuel to a supply pressure before the gaseous fuel is supplied to the internal combustion engine.

[0015] The fuel compression device can compensate for a drop in fuel outlet pressure, thus enabling the fuel to be delivered to the internal combustion engine at the desired supply pressure even when the fuel outlet pressure is below the required or desired supply pressure. This allows for a consistently high power output from the internal combustion engine, regardless of the outlet pressure, particularly the fuel tank level. Without the fuel compression device, the supply pressure would always be at most equal to the outlet pressure, for example, the pressure in a fuel tank. However, a lower supply pressure means that less fuel can be delivered per combustion cycle of the internal combustion engine.Therefore, the maximum possible power output of the internal combustion engine would steadily decrease as the fuel tank level drops, as soon as the pressure in the fuel tank falls below the desired supply pressure.

[0016] The internal combustion engine is preferably an internal combustion engine, more preferably a reciprocating piston engine. The gaseous fuel is preferably molecular hydrogen, but can also be another gas, for example a hydrocarbon-containing gas such as methane, compressed natural gas (CNG) or liquefied petroleum gas (LPG).

[0017] Preheating the fuel in the fuel preheating system can be achieved, for example, by heat exchange with an existing heat flow, such as waste heat from the exhaust gas of an internal combustion engine, or by electrical heating. Preheating the fuel can increase the power output of the internal combustion engine.

[0018] The combustion air supply element is preferably a suction valve. The oxygen-containing gas is preferably air, for example ambient air. The fuel supply element is preferably an injection nozzle. The gaseous fuel is preferably supplied to the internal combustion engine by direct injection.

[0019] Preferably, the fuel is stored in a fuel tank. The fuel is preferably in gaseous form in the fuel tank, but can also be in liquefied form; for example, a hydrocarbon mixture containing butane and propane can be stored under pressure as liquefied petroleum gas (LPG). Molecular hydrogen can also be stored in liquid form with appropriate cooling. Preferably, the pressure of the fuel in the fuel tank is a maximum of 1000 bar, more preferably a maximum of 875 bar.

[0020] The supply pressure at which the fuel is fed to the internal combustion engine is preferably between 200 bar and 400 bar, more preferably between 250 bar and 350 bar, and most preferably essentially at 300 bar. If the pressure in the fuel tank is higher than the desired supply pressure, the fuel pressure can be reduced to the supply pressure, for example by a pressure regulating valve, before the fuel is transferred from the fuel tank via the fuel line and the fuel supply element to the internal combustion engine.

[0021] As long as the pressure in the fuel tank is at least equal to the desired supply pressure, the fuel compression device does not need to perform any compression work. However, if the pressure in the fuel tank – and therefore also the outlet pressure – drops below the desired supply pressure, the fuel compression device can be activated to compress the fuel to the desired supply pressure.

[0022] The fuel compression device preferably includes a compressor that can compress the gaseous fuel from the outlet pressure to the supply pressure. The fuel compression device can be driven, for example, by the internal combustion engine, perhaps via a mechanical power transmission. The fuel compression device can also draw energy from a recuperation unit. The recuperation unit can, for example, recover energy when a vehicle brakes.

[0023] In a preferred embodiment, the fuel compression device is arranged in the direction of fuel flow upstream of the fuel preheating device.

[0024] This arrangement can increase the energy efficiency of the internal combustion engine system. Due to the decreasing gas density with increasing temperature, the energy consumption for compressing the gaseous fuel increases preferentially with increasing temperature of the fuel being compressed. Therefore, from an energy efficiency perspective, it is advantageous to heat the gaseous fuel to the supply temperature only after compression.

[0025] For the purposes of this disclosure, the term "fuel flow direction" shall be understood to mean the flow direction of the fuel when the fuel is transferred from the fuel line via the fuel supply element into the internal combustion engine.

[0026] In a preferred embodiment, the fuel compression device comprises a fuel tank, a working fluid tank, and a working fluid pump, wherein the working fluid pump is configured to pump a working fluid from the working fluid tank into the fuel tank so that the gaseous fuel in the fuel tank can be compressed to the supply pressure. Preferably, the fuel in the fuel tank is continuously maintained at a target pressure. The target pressure is preferably at least equal to or higher than the supply pressure. Pumping liquids, especially essentially incompressible liquids, can be carried out more energy-efficiently than compressing gases. The working fluid is preferably essentially incompressible. Therefore, this embodiment can increase the energy efficiency of the internal combustion engine system.

[0027] Preferably, in this embodiment, the working fluid pump is activated when the pressure in the fuel tank falls below the desired supply pressure. The working fluid pump then preferably pumps working fluid from the working fluid tank into the fuel tank until the fuel pressure in the fuel tank again equals or exceeds the desired supply pressure. Alternatively, the working fluid pump can also be activated before the pressure in the fuel tank falls below the supply pressure, so that the pressure in the fuel tank is always higher than the supply pressure. Preferably, the working fluid pump is operated in a hysteresis circuit.

[0028] In this embodiment, the working fluid is preferably in direct contact with the fuel in the fuel tank. Therefore, the working fluid preferably has low solubility for the fuel, especially hydrogen. The working fluid preferably exhibits low foaming tendency, good wear properties, and / or low vapor pressure.

[0029] The working fluid preferably contains a polyalphaolefin. A "polyalphaolefin" is understood to be a poly-l-olefin produced by the polymerization of alpha olefins. The term "polyalphaolefin" encompasses polyalphaolefin homopolymers, polymers composed of two or more different monomer units (e.g., polyalphaolefin copolymers, polyalphaolefin terpolymers), and mixtures thereof. The advantages of polyalphaolefins for these and similar applications are described in detail in document WO 2024 / 194178 Al.

[0030] In a preferred embodiment, a computing unit is provided which is designed to control and / or regulate the power consumption of the fuel compression device, so that the supply pressure can be kept essentially constant despite varying outlet pressure.

[0031] By controlling or regulating the power consumption of the fuel compression unit, a drop in performance as the fuel tank level decreases can be avoided. Thanks to this control or regulation, the internal combustion engine system can preferably provide a substantially constant power output. This is particularly advantageous when the internal combustion engine system is used to power a vehicle, as the same maximum power is always available to the driver. The driver therefore preferably does not need to adjust their driving style to the fuel tank level.

[0032] Preferably, the power input of the fuel compression device and / or the power output of the internal combustion engine is controlled or regulated by the control unit based on the outlet pressure and / or the supply pressure, preferably based on the pressure difference between the outlet pressure and the supply pressure. The outlet pressure is preferably measured in the fuel line, preferably directly after the fuel tank. Alternatively, the outlet pressure can also be measured in the fuel tank. The supply pressure is preferably measured in the fuel supply element or directly upstream of the fuel supply element. The power output of the internal combustion engine can be controlled or regulated by the amount of fuel supplied to the internal combustion engine and / or the amount of oxygen-containing gas supplied to the internal combustion engine.

[0033] Depending on the design, the power input of the fuel compression device and / or the power output of the internal combustion engine can be controlled and / or regulated, for example, via the power input of the compressor that compresses the gaseous fuel or via the power input of the working fluid pump.

[0034] The power made available to the driver of a vehicle powered by the internal combustion engine system according to the invention is preferably independent of the output pressure and, in particular, of the pressure in the fuel tank by regulating the power output of the internal combustion engine and / or the power input of the compressor.

[0035] Preferably, the power consumption of the fuel compression device is increased by the control unit when the difference between the outlet pressure and the supply pressure increases or when the pressure in the fuel tank decreases. The control unit preferably reduces the power consumption of the fuel compression device to a minimum at maximum tank pressure and preferably increases the power consumption of the fuel compression device when the tank pressure decreases. The power output of the internal combustion engine is preferably adjusted to the same extent as the power requirement of the pump, so that the power available to the driver of the vehicle, which is powered by the internal combustion engine system according to the invention, remains essentially constant.Preferably, the power output of the internal combustion engine is controlled or regulated such that it corresponds to the difference between the maximum possible power output of the internal combustion engine and the maximum power input of the fuel compression device. The energy required by the fuel compression device is preferably supplied at least partially by the internal combustion engine.

[0036] The "essentially constant power" provided to the driver means, in particular, that the power output is constant at a given engine speed, especially independent of fuel tank pressure. In other words, the power output is preferably dependent on engine speed, providing the driver with a power-speed curve that is independent of fuel tank pressure.

[0037] According to a preferred embodiment, the fuel preheating device includes a heat exchanger with which heat from the exhaust gas of the internal combustion engine can be transferred to the fuel. This allows the waste heat from the internal combustion engine to be used for fuel preheating, thereby increasing the overall efficiency of the internal combustion engine system.

[0038] Preferably, the fuel is heated by the fuel preheating device to a temperature of at least 250 °C, more preferably to a temperature between 250 °C and 500 °C. The exhaust gas is preferably cooled to a temperature between 250 °C and 400 °C, more preferably between 250 °C and 300 °C. In principle, the highest possible fuel temperature is desirable, as this allows for higher engine power. However, the maximum temperature is limited by the temperature resistance of the materials. Furthermore, it is desirable for a certain amount of heat to remain in the exhaust gas, which is then available for further heat recovery in a subsequent low-temperature cycle.In a preferred embodiment, a bypass line is provided through which the fuel can be supplied to the internal combustion engine without first being preheated in the fuel preheating device.

[0039] The bypass line allows the direct introduction of fuel into the internal combustion engine without further preheating in the event of an increased compression temperature, for example, due to high pressure conditions in the fuel compression unit. This is particularly advantageous in situations where the final compression temperature of the fuel after the fuel compression unit is higher than the exhaust gas temperature. If heat exchange between the exhaust gas and the fuel is provided in the fuel preheating unit, heat will be transferred from the fuel to the exhaust gas stream in such situations if no bypass line is provided. Heat transfer in this direction should be avoided for reasons of energy efficiency.

[0040] Preferably, the bypass line can be opened and closed by at least one bypass valve, so that the fuel can be routed either via the fuel preheating device or via the bypass line.

[0041] According to a preferred embodiment, a turbocharger is provided to extract energy from the exhaust gas of the internal combustion engine and to use the energy, at least partially, to compress the oxygen-containing gas before it is fed into the internal combustion engine.

[0042] By compressing the oxygen-containing gas, more oxygen-containing gas can be introduced into the internal combustion engine per operating cycle, thereby increasing the engine's power output. Since energy is extracted from the exhaust gas for compression, the turbocharger can improve the overall efficiency of the internal combustion engine system. The turbocharger preferably has an expansion turbine driven by the exhaust gas. This preferably reduces the exhaust gas temperature to between 300°C and 500°C. The expansion turbine is preferably arranged upstream of a heat exchanger in the fuel preheating system, which extracts heat from the exhaust gas and transfers it to the fuel.

[0043] In a preferred embodiment, a low-temperature heat engine is provided which is designed to obtain kinetic energy from waste heat of the exhaust gas of the internal combustion engine.

[0044] The low-temperature heat engine utilizes a low-temperature cycle, preferably an Organic Rankine Cycle (ORC), to extract heat from the exhaust gas and convert it into kinetic energy. A low-temperature cycle makes it possible to extract a particularly large amount of heat from the exhaust gas and use it to generate kinetic energy despite the comparatively low temperature level. This increases the overall efficiency of the internal combustion engine system.

[0045] The exhaust gas is preferably fed to the low-temperature heat engine at temperatures between 250 °C and 500 °C, more preferably between 250 °C and 400 °C.

[0046] Through the low-temperature cycle process, the exhaust gas is preferably cooled to a temperature of a maximum of 100 °C, more preferably a maximum of 80 °C, and even more preferably a maximum of 60 °C.

[0047] The low-temperature heat engine is preferably arranged in the direction of exhaust gas flow downstream of the heat exchanger of the fuel preheating device, which can extract heat from the exhaust gas in order to transfer it to the fuel.

[0048] In a preferred embodiment, a power transfer unit is provided to utilize kinetic energy generated in the low-temperature heat engine for the operation of the internal combustion engine and / or the fuel compression device. This allows the power output of the internal combustion engine and / or the overall efficiency of the internal combustion engine system to be increased.

[0049] The power transmission unit transmits the power of the low-temperature heat engine, preferably at least partially, to the internal combustion engine and / or the fuel compression unit via mechanical power transmission. The power is preferably supplied to the internal combustion engine at the crankshaft.

[0050] In a preferred embodiment, a cooling device is provided which is designed to cool the oxygen-containing gas before it is fed into the internal combustion engine.

[0051] Cooling the oxygen-containing gas allows more oxygen to be introduced into the internal combustion engine at the same pressure. Consequently, more fuel can be burned in the engine per combustion cycle. This increases the engine's power output per displacement, particularly in a reciprocating engine. Due to reduced friction losses, the higher power output per displacement leads to increased efficiency of the internal combustion engine.

[0052] In a preferred embodiment, a heat transfer device is provided which is configured to supply waste heat from the cooling device to the low-temperature engine. This allows the waste heat from the cooling device to be utilized, which in turn increases the overall efficiency of the internal combustion engine system.

[0053] The device according to the invention for providing electrical energy comprises at least the following elements:

[0054] an internal combustion engine system according to one of the above-described design forms and

[0055] a generator for at least partially converting kinetic energy produced in the internal combustion engine into electrical energy.

[0056] By using the internal combustion engine system according to the invention, the overall efficiency of the device for providing electrical energy can be improved.

[0057] The device for providing electrical energy can, for example, be part of a grid storage system. The grid storage system can be configured to draw electrical energy from a power grid, store the drawn electrical energy in chemical form, and convert the stored energy back into electrical energy as needed, which can then be fed back into the power grid.

[0058] Extracting electrical energy from the power grid is preferably carried out using an electrolysis unit configured to produce hydrogen (H2) using electrical energy, preferably consuming water (H2O). The produced hydrogen is preferably stored in a pressure tank. The pressure tank can correspond to the fuel tank of the internal combustion engine system according to the invention. In the internal combustion engine system according to the invention, kinetic energy can be provided by burning hydrogen, which can be converted into electrical energy by the generator. The electrical energy can be fed back into the power grid or used elsewhere, for example, for an industrial process.The pressure tank can also be configured to extract hydrogen for other purposes, for example, to fill a hydrogen tanker for transporting hydrogen and / or to refuel a hydrogen-powered vehicle. The electrical energy supply device can be configured to feed waste heat, generated, for example, in the internal combustion engine, into a district heating network.

[0059] By using the internal combustion engine system according to the invention, the overall efficiency of a grid storage system can be improved.

[0060] The vehicle according to the invention has at least the following elements:

[0061] an internal combustion engine system according to one of the above described forms; a drive system designed to use at least some of the kinetic energy generated in the internal combustion engine for the movement of the vehicle.

[0062] The vehicle according to the invention preferably has a fuel tank, which can preferably be filled with gaseous hydrogen. The internal combustion engine system according to the invention makes it possible to provide the driver with a driving experience in which the maximum achievable power, for example, by fully depressing the accelerator pedal, does not depend on the fuel tank level. This can also increase the vehicle's safety, since the driver can preferably always rely on being able to access the familiar maximum power of the internal combustion engine system during an overtaking maneuver. This, for example, helps to avoid dangerous misjudgments of the overtaking distance.

[0063] The inventive method for providing kinetic energy by combustion of a gaseous fuel, preferably molecular hydrogen (H2), comprises the following steps:

[0064] - Provision of an internal combustion engine system according to one of the embodiments described above,

[0065] - Providing the gaseous fuel at the output pressure,

[0066] - Preheating the gaseous fuel to the supply temperature,

[0067] - Feeding the preheated gaseous fuel into the combustion engine,

[0068] - Supplying the oxygen-containing gas to the internal combustion engine,

[0069] - Providing kinetic energy by burning the gaseous fuel in the internal combustion engine and

[0070] - Compression of the gaseous fuel by the fuel compression device to the supply pressure before the fuel is supplied to the internal combustion engine, if the outlet pressure is lower than the supply pressure. All features, effects and advantages described above in connection with the device are also transferable analogously to the method according to the invention.

[0071] Preheating can take place before or after compaction. Preferably, preheating takes place after compaction.

[0072] In a preferred embodiment, the power consumption of the fuel compression device is controlled or regulated in such a way that the supply pressure remains essentially constant despite varying output pressure.

[0073] In a preferred embodiment, kinetic energy is obtained from the waste heat of the exhaust gas of the internal combustion engine via a low-temperature cycle.

[0074] The low-temperature cycle process can be, for example, a Sterling cycle, a Kalina cycle, or preferably an Organic Rankine Cycle (ORC).

[0075] In a preferred embodiment, kinetic energy obtained in the low-temperature cycle process is used to operate the internal combustion engine and / or the fuel compression device.

[0076] Unless otherwise stated, all pressures mentioned in this disclosure are to be understood as absolute pressures.

[0077] The terms "before" and "after" refer - when used in a spatial context - to the direction of flow of the flowing medium, for example a fuel, an exhaust gas, combustion air or the like.

[0078] The invention is further explained below with reference to the embodiments shown in the drawings.

[0079] Fig. 1 shows a schematic representation of an exemplary internal combustion engine system according to the invention. Fig. 2 shows an alternative embodiment of a fuel compression device of an internal combustion engine system according to the invention.

[0080] The internal combustion engine system 1 according to the invention, as shown in Fig. 1, comprises an internal combustion engine 2 which is designed to burn a gaseous fuel, preferably hydrogen (H2). The fuel is introduced into the internal combustion engine 2 by means of direct injection via an injection valve 3. An intake air stream 4 is supplied to the internal combustion engine 2 through a suction valve 5. The intake air stream 4 is pre-compressed by an air compressor 6, and a charge air cooler 7 cools the intake air stream 4. In the internal combustion engine 2, the fuel is burned, performing work, and expelled via the exhaust valve 8. The hot exhaust gas 9 is fed to an expansion turbine 10 and performs work there, thereby reducing the temperature of the expansion turbine outlet exhaust gas 11 to between 300 °C and 500 °C. The work performed in the expansion turbine 10 drives the air compressor 6 by means of a power transmission 12.A heat exchanger 13 transfers residual heat from the expansion turbine exhaust gas 11 to the fuel as the fuel flows through the heat exchanger 13 in a preheating line 14. This transfers a portion of the thermal energy from the expansion turbine exhaust gas 11 to the fuel, thereby increasing the power output of the internal combustion engine 2.

[0081] The fuel stored in a fuel tank 15 is initially fed into the fuel tank 15 at a pressure of up to 875 bar. As the internal combustion engine 2 consumes the fuel, the pressure in the fuel tank 15 decreases. A fuel compressor 16 increases the fuel pressure so that the injection valve 3 is always supplied with fuel at the highest possible injection pressure, which can be measured by an injection pressure transmitter 17.

[0082] In the embodiment shown in Fig. 1, which is particularly advantageous for vehicles, a computing unit 18 regulates the power provided by the internal combustion engine system. The fuel compressor 16, the injection pressure transmitter 17, and a tank pressure transmitter 19 are connected to the computing unit 18 via data links 35, 36, 37. The computing unit 18 regulates the power provided by the internal combustion engine system by appropriately controlling the injection pressure measured by the injection pressure transmitter 17, such that it is independent of the tank pressure determined by the tank pressure transmitter 19 and also independent of the power drawn by the fuel compressor 16. The fuel compressor 16 preferably draws power from the internal combustion engine 2, and this power is preferably transmitted by a power transmission 25.

[0083] In the embodiment shown in Fig. 1, residual heat remaining in the heat exchanger outlet exhaust gas 20 is supplied to a low-temperature cycle 21, for example, an Organic Rankine Cycle (ORC). The power provided by the low-temperature cycle 21 is preferably supplied to the internal combustion engine 2 at a crankshaft 23 via a power transmission 22. In this case, the low-temperature cycle 21 is connected to the processing unit 18 via a data link 38, and the processing unit 18 also takes into account the additional power from the low-temperature cycle 21 when controlling the power supplied by the internal combustion engine system 1. The control is such that the power available at the crankshaft 23, for example, for moving a vehicle, is essentially independent of the tank pressure at a specific speed of the internal combustion engine 2.In the embodiment shown in Fig. 1, heat preferably removed from the charge air cooler 7 is supplied to the low-temperature cycle process 21 via a heat transfer line 24.

[0084] A bypass valve 26 allows the fuel to be routed through a bypass line 27 instead of through the preheating line 14, thus bypassing the heat exchanger 13. This allows, in the case of an increased compression end temperature, for example due to high pressure conditions in the fuel compressor 16, the direct introduction of the fuel into the injection valve 3 without prior preheating in the heat exchanger 13. Situations are conceivable in which the compression end temperature is higher than the temperature of the expansion turbine exhaust gas 11. In this case, heat would be transferred from the fuel to the exhaust gas stream. This should be avoided. The compression end temperature is preferably measured by a temperature transmitter 28. The position of the bypass valve 26 is preferably controlled or regulated by measuring the compression end temperature.

[0085] Figure 2 shows an alternative embodiment of a fuel compression device. This embodiment corresponds to that shown in Figure 1, except that the fuel tank 15 and the fuel compressor 16 are replaced by the arrangement shown in Figure 2. In this embodiment, in addition to a fuel tank 33 filled with gaseous fuel, in particular hydrogen, a working fluid tank 29 is provided. The working fluid tank 29 contains a working fluid 30, which is in a liquid state. The working fluid tank 29 is connected to the fuel tank 33 via a working fluid line 31. A working fluid pump 32 is arranged in the working fluid line 31. The working fluid pump 32 can pump working fluid 30 from the working fluid tank 29 to the fuel tank 33.From the fuel tank 33, the fuel can be fed directly into the preheating line 14 and / or the bypass line 27 via the temperature transmitter 28. During operation, as the fuel level in the fuel tank 33 continuously decreases, essentially enough working fluid 30 is always pumped from the working fluid tank 29 into the fuel tank 33 to maintain a substantially constant pressure in the fuel tank 33. In this embodiment, the pressure in the fuel tank 33 is preferably at least as high as the injection pressure measured by the injection pressure transmitter 17. In this embodiment, the working fluid 30 is in direct contact with the fuel, particularly the hydrogen, in the fuel tank 33. The working fluid 30 is characterized by low solubility in the fuel, especially hydrogen, low foaming tendency, sufficiently good wear resistance, and low vapor pressure.

[0086] For example, the pressure of hydrogen (H2) in the fuel tank 15, 33 is a maximum of 875 bar. The injection pressure into the internal combustion engine 2 is, for example, 300 bar. Before the pressure in the fuel tank falls below 300 bar, the fuel compressor 16 is started in the embodiment shown in Fig. 1 and increases the pressure of the hydrogen in the fuel line 34 to at least 300 bar. In the embodiment shown in Fig.

[0087] 2. Instead of the fuel compressor 16, the working fluid pump 32 is started to maintain the pressure in the fuel tank 33 at a minimum of 300 bar. The hydrogen is then heated by the heat exchanger 13 to 250 °C to 500 °C, provided it has not already reached this temperature through compression and is therefore routed through the bypass line 27, and supplied to the internal combustion engine 2 through the injection valve 3. The residual heat of the heat exchanger outlet exhaust gas 20 is supplied to a low-temperature cycle 21, in particular an ORC process, at heat exchanger outlet exhaust gas temperatures 20 of 250 °C to 400 °C.

Claims

Patent claims:

1. Internal combustion engine system ( 1 ) for providing kinetic energy by combustion of a gaseous fuel, preferably molecular hydrogen (H2) , in an internal combustion engine (2 ) , comprising: the internal combustion engine (2 ) , a fuel line (34 ) for supplying the gaseous fuel at an outlet pressure, a fuel preheating device for preheating the gaseous fuel to a supply temperature, a fuel supply element for supplying the gaseous fuel to the internal combustion engine and a combustion air supply element for supplying an oxygen-containing gas to the internal combustion engine (2 ) , characterized in that a fuel compression device is provided for compressing the gaseous fuel to a supply pressure before the gaseous fuel is supplied to the internal combustion engine (2 ).

2. Internal combustion engine system ( 1 ) according to claim 1, characterized in that the fuel compression device is arranged in the direction of fuel flow upstream of the fuel preheating device .

3. Internal combustion engine system ( 1 ) according to claim 1 or 2, characterized in that the fuel compression device comprises a fuel tank (33) , a working fluid tank (29) and a working fluid pump (32 ), wherein the working fluid pump (32 ) is configured to pump a working fluid (30) from the working fluid tank (29) into the fuel tank (33) so that the gaseous fuel in the fuel tank (33) can be compressed to the supply pressure.

4. Internal combustion engine system ( 1 ) according to one of claims 1 to 3, characterized in that a computing unit ( 18 ) is provided which is equipped to control and / or regulate a power input of the fuel compression device, so that the supply pressure can be kept essentially constant with varying output pressure.

5. Internal combustion engine system ( 1 ) according to one of claims 1 to 4, characterized in that a bypass line (27 ) is provided with which the fuel can be supplied to the internal combustion engine (2 ) without having to be preheated in the fuel preheating device.

6. Internal combustion engine system ( 1 ) according to one of claims 1 to 5, characterized in that a low-temperature heat engine is provided which is designed to obtain kinetic energy from waste heat of the exhaust gas of the internal combustion engine (2 ).

7. Internal combustion engine system ( 1 ) according to claim 6, characterized in that a power transmission unit is provided in order to be able to use kinetic energy obtained in the low-temperature heat engine for the operation of the internal combustion engine (2 ) and / or the fuel compression device.

8. Internal combustion engine system ( 1 ) according to one of claims 1 to 7, characterized in that a cooling device is provided which is configured to cool the oxygen-containing gas before it is supplied to the internal combustion engine (2 ).

9. Internal combustion engine system ( 1 ) according to claim 8 in conjunction with claim 6, characterized in that a heat transfer device is provided which is configured to supply waste heat from the cooling device to the low-temperature engine.

10. Device for providing electrical energy, comprising: an internal combustion engine system ( 1 ) according to any one of claims 1 to 9 and a generator for at least partial conversion of kinetic energy produced in the internal combustion engine (2) into electrical energy .

11. Vehicle, exhibiting an internal combustion engine system ( 1 ) according to any one of claims 1 to 9 and a propulsion system designed to utilize at least some of the kinetic energy generated in the internal combustion engine (2) for the movement of the vehicle.

12. Method for providing kinetic energy by combustion of a gaseous fuel, preferably molecular hydrogen (H2), comprising the steps: - Provision of an internal combustion engine system ( 1 ) according to any one of claims 1 to 9, - Providing the gaseous fuel at the output pressure, - Preheating the gaseous fuel to the supply temperature, - Supplying the preheated gaseous fuel to the internal combustion engine (2 ) , - Supplying the oxygen-containing gas to the internal combustion engine (2 ) , - Providing kinetic energy by burning the gaseous fuel in the internal combustion engine (2 ) , characterized in that The gaseous fuel is compressed to the supply pressure by the fuel compression device before being fed into the internal combustion engine (2 ) if the outlet pressure is lower than the supply pressure.

13. Method according to claim 12, characterized in that the power input of the fuel compression device is controlled or regulated in such a way that the supply pressure remains essentially constant despite varying output pressure.

14. Method according to claim 12 or 13, characterized in that kinetic energy is obtained from the waste heat of the exhaust gas of the internal combustion engine (2 ) via a low-temperature cycle process (21 ).

15. Method according to one of claims 12 to 14, characterized in that kinetic energy obtained in the low-temperature cycle process (21) is used to operate the internal combustion engine (2) and / or the fuel compression device.

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