Internal combustion engine for gaseous fuels, and method for operating the internal combustion engine

Abstract

The invention relates to an internal combustion engine (10; 10a; 10b; 10c) for gaseous fuels, comprising: at least one combustion chamber (26) in which the gaseous fuel is combusted; a gas tank (12) in which the gaseous fuel is held available at an operating pressure and can be fed in the direction of the at least one combustion chamber (26) via a supply line (14); an exhaust system (42) which comprises an exhaust pipe (44) and a catalytic converter (46), wherein the exhaust pipe (44) is connected to the at least one combustion chamber (26); and an intake tract (34) which comprises an intake pipe (32) via which fresh air can be fed into the at least one combustion chamber (26).

Description

[0001] Description

[0002] Internal combustion engine for gaseous fuels and method for operating the internal combustion engine

[0003] Technical area

[0004] The invention relates to an internal combustion engine for gaseous fuels, which, when the internal combustion engine is shut down, is characterized by a particularly advantageous release of combustible gas still present in the internal combustion engine to the atmosphere. Furthermore, the invention relates to a method for operating such an internal combustion engine.

[0005] State of the art

[0006] Internal combustion engines for the combustion of gaseous fuel, in particular for the combustion of hydrogen, are known from the prior art. For example, DE 102020 214697 A1, owned by the applicant, shows an internal combustion engine designed according to the preamble of claim 1, in which the gaseous fuel is stored in high-pressure tanks. The highly pressurized hydrogen is supplied to the internal combustion engine from the high-pressure tanks via a supply line and burned in the combustion chambers of the internal combustion engine, with mechanical energy being generated from the combustion energy. The exhaust gases are directed to the outside via a catalytic converter in the exhaust system, where, in particular, nitrogen oxides, but also unburned hydrogen, are broken down.The hydrogen can either be introduced directly into the respective combustion chamber of the internal combustion engine (so-called direct injection), whereby the mixing with the supplied fresh air takes place in the combustion chamber.

[0007] Alternatively, the hydrogen can be mixed with the air in an inlet line and the hydrogen-air mixture can then be introduced into the combustion chamber (intake manifold injection). In the area of ​​the internal combustion engine, which in addition to the actual cylinders also includes an intake tract for supplying fresh air and the exhaust system, there is typically still combustible gas after the internal combustion engine has been switched off. This combustible gas can only be kept in the area of ​​the internal combustion engine with very great technical effort and appropriate sealing measures. To avoid this effort, it is also known from the prior art to introduce gas present in the intake or supply tract into the exhaust tract during the shutdown phase of the internal combustion engine by means of a process known as "purging". This process then releases it into the environment via the exhaust gas catalyst.

[0008] Disclosure of the invention

[0009] The inventive internal combustion engine for gaseous fuels with the features of claim 1 has the advantage that, even under unfavorable circumstances, for example, if the engine stalls during a purging process, the risk of an undesired release of gas or hydrogen from the injection system into the environment while the engine is stopped is avoided. This also makes it possible to avoid restarting the engine to perform the purging process, particularly in such cases.

[0010] The invention is based on the idea of ​​purging the injection system with the aid of an additional air flow from the intake manifold into the exhaust system, at least partially or completely, while the engine is stopped. This additional air flow from the intake manifold into the engine's exhaust system can be generated, for example, using a secondary air pump or a compressor. This creates a system for conveying and discharging unburned gas that is independent of engine operation.

[0011] Against the background of the above explanations, it is therefore provided in an internal combustion engine according to the invention for gaseous fuels with the features of claim 1 that said engine is designed such that the intake tract is coupled to a device for generating an air flow from the intake tract into the exhaust system, wherein a control device is further provided which is designed to operate the device for generating the air flow during a shutdown phase and / or a standstill phase of the internal combustion engine.

[0012] Advantageous further developments of the internal combustion engine according to the invention for gaseous fuels are listed in the subclaims.

[0013] In a first design embodiment of the internal combustion engine used for intake manifold injection, the device for generating the air flow has an intake line that opens into a region of the intake manifold near the combustion chamber. The region near the combustion chamber refers to the area where the injector for injecting the fuel is located in the intake manifold or opens into the intake manifold.

[0014] In a preferred development of the last proposal, an additional or further intake line is provided, which opens into a region of the intake manifold or an air filter remote from the combustion chamber, and a switching device is provided that enables control of the air flow from one of the two intake lines. Such a design of the internal combustion engine enables optimal extraction of air or combustible gas from different areas of the intake tract.

[0015] In order to also free the area of ​​the internal combustion engine which supplies the combustion chambers with the combustible gas from the gas in the event of the engine being switched off, a further variant of the internal combustion engine has a supply line coupled to a rail, from which a branch line branches off for each combustion chamber to a gas injector which is designed to inject the gaseous fuel into the combustion chamber or the intake manifold in a region close to the combustion chamber, wherein the rail is coupled to a discharge valve which can be controlled by the control device and which releases the gaseous fuel from the rail at least indirectly into the exhaust system. In this case, the gaseous fuel located in the rail is thus discharged directly into the exhaust system (upstream of the catalytic converter) in the event of the engine being switched off, the gaseous fuel being displaced or drawn into the catalytic converter via the device for generating the air flow.and from there discharged into the environment. In a first design development of this variant, the drain valve is connected directly to the exhaust system via a connecting line. This design is characterized by its particularly simple and minimal implementation.

[0016] In a solution involving greater design complexity, the drain valve can instead be coupled to a collecting tank designed to discharge the gaseous fuel contained in the collecting tank into the intake tract via a connecting line by means of a conveying device controlled by the control device. This design has the advantage that the gaseous fuel is initially collected in the collecting tank during engine shutdown and can then be combusted by being discharged into the intake tract during a restart. This thus minimizes the consumption of gaseous fuel and the release of gaseous fuel into the environment.

[0017] Furthermore, the invention comprises a method for operating an internal combustion engine designed according to the invention as described so far, wherein the method is characterized in that in order to discharge the gaseous fuel from the intake tract and the exhaust system during an engine stop and / or a run-on phase of the engine, the device for generating an air flow from the intake tract into the exhaust system is activated by means of the control device.

[0018] A further development of this general method provides that by actuating the switching device, suction takes place from one of two suction lines.

[0019] A preferred development of the methods described so far provides for additional gaseous fuel to be diverted from the rail into the exhaust system via the discharge valve. It is also advantageous that, when the engine is restarted, gaseous fuel contained in a collecting container is injected into the intake tract. Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments of the invention and from the drawings.

[0020] Short description of the drawings

[0021] Fig. 1 shows a first embodiment of the internal combustion engine according to the invention in a schematic representation,

[0022] Fig. 2 to

[0023] Fig. 4 also shows, in schematic representations, different embodiments of modified internal combustion engines and

[0024] Fig. 5 is a schematic representation of a gas collecting container used in Fig. 4.

[0025] Embodiments of the invention

[0026] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0027] The internal combustion engine 10 schematically illustrated in Fig. 1 preferably uses hydrogen as the gaseous fuel or gas for operation. The internal combustion engine or engine 10 can be designed for both commercial vehicle and passenger car applications. Stationary engines, range extender engines for hybrid drives, rail propulsion, marine engines, or combined heat and power plants can also utilize the invention.

[0028] The internal combustion engine 10 comprises a gas tank 12, in which the gaseous fuel is stored at operating pressure in a conventional manner. The gas tank 12 is connected to a (gas) rail 16 via a supply line 14. A pressure sensor 17 serves to detect the pressure of the gas in the rail 16. A tank valve 18 and a pressure control valve 20, which can be controlled by a control device 25, can be interposed in the connecting line 14.

[0029] In the illustrated embodiment, the internal combustion engine 10 has an engine block with four combustion chambers 26 in which the gaseous fuel or gas is burned, thereby generating mechanical energy in a manner known per se. In what is known as direct injection, a supply line 28 extends from the rail 16 for each combustion chamber 26 and is connected to a gas injector 30. The gas injector 30 injects the gas directly into the respective combustion chamber 26. In what is known as intake manifold injection, a supply line 28a, shown in dashed lines, extends from the rail 16 and is also connected to a gas injector 30a, although the gas injector 30a injects the gas into an intake manifold 32 in a region of the combustion chamber 26 close to the combustion chamber, i.e. outside the respective combustion chamber 26.

[0030] It should be noted that, for the sake of simplicity, only one supply line 28, 28a and one gas injector 30, 30a are shown in the illustration in Fig. 1. However, a corresponding supply line 28, 28a and one gas injector 30, 30a are naturally provided for each of the combustion chambers 26.

[0031] The intake manifold 32 is part of an intake tract 34 for supplying fresh air to the combustion chambers 26. The intake tract 34 includes an air filter 36 through which ambient air is drawn in. A branch 38 branches off from the intake manifold 32 to the respective combustion chamber 26. In the case of intake manifold injection, the injector 30a injects the gas in the region of the respective branch 38, close to the combustion chamber.

[0032] Furthermore, each combustion chamber 26 is connected via an exhaust manifold 40, which is part of an exhaust system 42, to an exhaust line 44. The exhaust pipe 44 opens into an (exhaust gas) catalyst 46. Near the catalyst 46, a gas sensor 48 (a hydrogen sensor when hydrogen is used) is also arranged in the exhaust pipe 44, the signals of which are fed to the control device 25 as an input variable. Furthermore, the internal combustion engine 10 has a speed sensor 50, the signals of which are also fed to the control device 25 as an input variable.

[0033] The intake tract 34 is connected to the exhaust system 42 via a device 55 for generating an air flow from the intake tract 34. For this purpose, the device 55 has, for example, a secondary air pump 56 and a secondary air valve 58, both of which can be controlled by the control device 25. The secondary air pump 56 is connected via a switching device in the form of a switching flap 60, which can be controlled by the control device 25, to a first intake line 62, which draws in air from the area of ​​the air filter 36. A second intake line 64, which also opens in the area of ​​the deflection flap 60, is connected, with the interposition of a check valve 66, to each of the branches 38 in the area of ​​the junction or injection of the gas injector 30a.

[0034] Furthermore, the internal combustion engine 10 has, in a manner known per se, an inlet valve (not shown) and an exhaust valve in the region of the respective combustion chamber 26. The function of the internal combustion engine 10 for discharging (unburned) gas when the internal combustion engine 10 is stationary is described as follows:

[0035] In a first alternative, using direct-injection gas injectors 30 and knowing the crankshaft position of the internal combustion engine 10, the control device 25 detects the position of the crankshaft when the engine is stopped and thus knows which of the cylinders or combustion chambers 26 have an open exhaust valve. The excess gas from the combustion chamber 26 is then released into the exhaust pipe 44 via these cylinders or combustion chambers 26 when the device 55 is activated, and is released into the environment via the catalytic converter 46.

[0036] In the event that the control device 25 does not know the crankshaft position of the internal combustion engine 10, the deflection flap 60 is switched such that air is drawn in from the region of the second intake line 64. By opening or activating the gas injectors 30 by the control device 25, excess gas is discharged via all gas injectors 30. From the cylinders or combustion chambers 26 with an open exhaust valve, the gas flows directly into the exhaust pipe 44; from the cylinders or combustion chambers 26 with an open intake valve, in contrast, the gas flows into the intake manifold 32; and in the cylinders or combustion chambers 26 with closed intake and exhaust valves, the gas remains enclosed in the combustion chamber 26. By activating the device 55, both the gas from the intake manifold 32 and from the exhaust pipe 44 is released into the environment via the exhaust tract 42 and the catalytic converter 46.The control device 25 can thereby carry out flow control by appropriately controlling the device 55, so that optimal cleaning or dilution of the gas is possible.

[0037] If the internal combustion engine 10 has intake manifold injection or when using gas injectors 30a, the control device 25 sets the switching valve 60 such that air is drawn in from the region of the second intake line 64. Furthermore, the control device 25 can then discharge the excess gas via the gas injectors 30a. The gas flows from the intake manifold 32 via the second intake line 64 into the exhaust pipe 44 and is flushed out of the exhaust system 42 by means of the device 55 via the catalyst 46.

[0038] Fig. 2 shows an internal combustion engine 10a which is designed as a direct-injection internal combustion engine 10a using gas injectors 30. For the sake of simplicity, only a single combustion chamber 26 or a single gas injector 30 is shown in Fig. 2. Furthermore, the secondary air pump 56 and the secondary air valve 58 or the device 55 are shown in a simplified or schematic manner. In addition, in contrast to the internal combustion engine 10, the internal combustion engine 10a has a drain valve in the form of a purge valve 70 connected to the rail 16. The purge valve 70 is connected directly to the exhaust pipe 44 via a connecting line 72. The internal combustion engine 10a has the advantage that the gas from the region of the rail 16 can be introduced directly into the exhaust system 42, past the respective combustion chamber 26. This gas is also released into the environment by means of the device 55 via the catalyst 46.

[0039] The internal combustion engine 10b shown in Fig. 3 differs from the

[0040] Internal combustion engine 10a differs only in that it is designed as an intake manifold injection system with a gas injector 30a provided for the respective combustion chamber 26. However, the two internal combustion engines 10a and 10b do not differ in terms of their functionality.

[0041] Finally, Figs. 4 and 5 show an internal combustion engine 10c in which, using the example of intake manifold injection corresponding to internal combustion engine 10a, the purge valve 70 introduces the gas into a collecting tank 74. The collecting tank 74 is in turn connected to the intake manifold 32 via a supply line 76. It should also be noted that the internal combustion engine 10c can also be designed as a direct-injection internal combustion engine 10c.

[0042] The area of ​​the collecting container 74 shown in more detail in Fig. 5 has a check valve 78 on the side facing the rail 16. A control valve 80 is also provided in the supply line 76 to the intake manifold 32. The interior of the collecting container 74 is divided by a membrane 82. The membrane 82 seals off a first sub-chamber 84 for receiving the gas from a second sub-chamber 86 in which inert gas, in particular nitrogen, is stored. The second sub-chamber 86 is divided by a partition wall 88 into two sub-chambers 90, 92, which are connected to one another by a pressure pump 94. The pressure in the second sub-chamber 92 is lower than in the first sub-chamber 90.

[0043] Since a relatively high pressure prevails in the rail 16, the gas from the rail 16 can flow into the collection tank 74 via the check valve 78 until pressure equilibrium is established. To actively pump the gas into the collection tank 74, the pressure pump 90 can pump the inert (compensation) gas located in the second sub-chamber 86 from the second sub-area 92 into the first sub-area 90. When the engine is restarted, the gas from the collection tank 74 is then released into the intake manifold 32 via the control valve 80.

[0044] The internal combustion engine 10, 10a to 10c described so far can be modified or altered in a variety of ways without deviating from the inventive concept. In particular, the device 55 can be operated during the shutdown phase, ie, upon initiation of the engine shutdown of the internal combustion engine 10, 10a to 10c.

Claims

Claims 1. Internal combustion engine (10; 10a; 10b; 10c) for gaseous fuels, with at least one combustion chamber (26) in which the gaseous fuel is burned, with a gas tank (12) in which the gaseous fuel is stored at an operating pressure and can be supplied via a supply line (14) in the direction of the at least one combustion chamber (26), with an exhaust system (42) which comprises an exhaust line (44) and an exhaust gas catalyst (46), wherein the exhaust line (44) is connected to the at least one combustion chamber (26), and with an intake tract (34) which comprises an intake manifold (32) via which fresh air can be supplied into the at least one combustion chamber (26), characterized in that the intake tract (34) is coupled to a device (55) for generating an air flow from the intake tract (34) into the exhaust system (42), and with a control device (25) which is is trained,to operate the device for generating the air flow during a shutdown phase and / or a standstill phase of the internal combustion engine (10; 10a; 10b; 10c).

2. Internal combustion engine according to claim 1, characterized in that the device (55) for generating the air flow has an intake line (64) which opens into a region of the intake manifold (32) near the combustion chamber.

3. Internal combustion engine according to claim 2, characterized in that a further intake line (62) is provided, which opens into a region of the intake manifold (32) remote from the combustion chamber or at an air filter (36), and in that a switching device (60) is provided, which Control of the air flow from one of the two intake lines (62, 64) is possible.

4. Internal combustion engine according to one of claims 1 to 3, characterized in that the supply line (14) is coupled to a rail (16), from which a feed line (28; 28a) with a gas injector (30; 30a) branches off for each combustion chamber (26), which is designed to blow the gaseous fuel into the combustion chamber (26) or the intake manifold (32) in a region close to the combustion chamber, and in that the rail (16) is coupled to a discharge valve (70) which can be controlled by the control device (25) and which releases the gaseous fuel from the rail (16) at least indirectly into the exhaust system (42).

5. Internal combustion engine according to claim 4, characterized in that the drain valve (70) is connected to the exhaust system (42) via a connecting line (72).

6. Internal combustion engine according to claim 4, characterized in that the drain valve (70) is coupled to a collecting container (74) which is designed to release the gaseous fuel located in the collecting container (74) into the intake tract (34) via a supply line (76) in the event of an engine start.

7. Method for operating an internal combustion engine (10; 10a; 10b; 10c) which is designed according to one of claims 1 to 6, characterized in that in order to discharge the gaseous fuel from the intake tract (34) and the exhaust system (42) during an engine stop and / or a run-on phase, the device (55) for generating the air flow from the intake tract (34) into the exhaust system (42) is activated by means of the control device (25).

8. Method according to claim 7, characterized in that actuation of the switching device (60) results in intake from one of two intake lines (62, 64).

9. The method according to claim 7 or 8, characterized in that additional gaseous fuel is introduced from the rail (16) via the discharge valve (70) into the exhaust system (42).

10. The method according to one of claims 7 to 9, characterized in that, upon a renewed engine start, gaseous fuel located in the collecting container (74) is blown into the intake tract (34).

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