Method for operating a gas internal combustion engine, and gas internal combustion engine

Abstract

The present invention relates to a method for operating a gas internal combustion engine during a switching-off operation of the gas internal combustion engine, comprising the steps of: closing a safety valve (3), which interrupts a connection to a gas tank (2), opening a valve (5) at a first combustion chamber (11) of the gas internal combustion engine in order to release a connection to an exhaust gas tract (6) in order to produce a throttle loss when the gas internal combustion engine is switched off and to increase a load of the gas internal combustion engine, with no combustion gas from a line region (4), which connects the safety valve (3) to the first combustion chamber (11), being supplied to the first combustion chamber (11), and burning combustion gas in a second combustion chamber (12), with an increased amount of combustion gas being used by the increased load generated in the first combustion chamber (11).

Description

[0001] Description

[0002] title

[0003] Method for operating a gas internal combustion engine and gas internal combustion engine

[0004] State of the art

[0005] The present invention relates to a method for operating a gas internal combustion engine, in particular a hydrogen internal combustion engine, during a shutdown process of the gas internal combustion engine, as well as to a gas internal combustion engine.

[0006] In hydrogen combustion engines, the hydrogen is kept under very high pressure. A problem arises after the engine is switched off: hydrogen, still under high pressure, remains in a section of the line between the gas tank and the engine. Due to the large pressure difference compared to atmospheric pressure, leaks in this line can cause hydrogen to escape, leading to undesirable accumulations of hydrogen outside the engine's hydrogen system and posing corresponding hazards.

[0007] Disclosure of the invention

[0008] The inventive method for operating a gas-powered internal combustion engine, in particular a hydrogen-powered internal combustion engine, during a shutdown process, with the features of claim 1, has the advantage that it enables a pressure reduction in a section of the line between a gas tank and a combustion chamber of the gas-powered internal combustion engine. This prevents gas located in the section of the line downstream of the gas tank from escaping into the environment after the gas-powered internal combustion engine is shut down. Thus, a safety-related measure of reducing the gas pressure in the section of the line downstream of the gas tank can be implemented, preferably without requiring any additional components on the gas-powered internal combustion engine.The method according to the invention is particularly useful for hydrogen gas combustion engines, since hydrogen is highly explosive and could accumulate in large quantities if it were to escape unintentionally from the pipe area, potentially posing a safety risk.

[0009] According to the invention, this is achieved by first closing a safety valve, located on or near a gas tank in a pipe section between the gas tank and a first combustion chamber of the gas engine, during the shutdown process of the gas engine. In a next step, a valve on the first combustion chamber of the gas engine is opened to allow a connection to the exhaust system of the gas engine. This allows throttling losses to be generated during the shutdown process of the gas engine and increases the load on the gas engine. No more fuel gas is supplied to the first combustion chamber. Fuel gas continues to be supplied and burned in a second combustion chamber from the closed pipe section, whereby fuel gas consumption in the second combustion chamber is also increased due to the increased load in the first combustion chamber.The increased consumption of fuel gas can achieve a rapid pressure drop in the enclosed pipeline area.

[0010] Thus, when the gas engine is switched off, a pressure reduction can be achieved in the enclosed pipe area with only a few combustion cycles, thereby preventing the risk of fuel gas leakage from the enclosed pipe area when the gas engine is switched off.

[0011] The dependent claims describe preferred embodiments of the invention.

[0012] Preferably, the valve on the first combustion chamber is opened until a predetermined pressure value is reached in the closed section of the pipe between the safety valve and the combustion chambers. Preferably, the predetermined pressure value corresponds to atmospheric pressure or is only slightly higher than atmospheric pressure.

[0013] In the inventive method, it is further preferred that the valve of the first combustion chamber is only partially opened. This allows the throttling losses to be maximized and thus a further increased load during the shutdown process to be achieved through the measures in the first combustion chamber.

[0014] The method according to the invention is preferably carried out only on exactly one combustion chamber of the gas internal combustion engine.

[0015] According to a preferred embodiment of the invention, the gas internal combustion engine has an even number of combustion chambers, wherein the method is carried out on only half of the combustion chambers or on less than half of the combustion chambers. If the gas internal combustion engine has, for example, six combustion chambers, the increased load described above is generated on a maximum of three combustion chambers in order to achieve a rapid shutdown of the gas internal combustion engine.

[0016] Particularly preferred is the valve that opens at the first combustion chamber, the exhaust valve. Preferably, the gas-powered internal combustion engine has an exhaust camshaft for actuating the exhaust valve with an additional profile, which is activated when the gas-powered internal combustion engine is switched off in order to actuate the exhaust valve of the first combustion chamber.

[0017] Alternatively, the valve on the first combustion chamber is an additional decompression valve that connects to the exhaust system. This additional decompression valve is preferably actuated by a control unit during the shutdown process of the gas-powered engine. It should be noted that the decompression valve and the exhaust valve can also be opened simultaneously.

[0018] A further preference is a constant valve opening stroke during a cycle. This results in particularly simple valve control.

[0019] Furthermore, the present invention relates to a gas-powered internal combustion engine, in particular a hydrogen-powered internal combustion engine, which is configured to carry out the method according to the invention. The gas-powered internal combustion engine preferably has more than two cylinders, in particular six or eight cylinders.

[0020] Brief description of the drawings

[0021] A preferred embodiment of the invention is described in detail below with reference to the accompanying drawings. The drawing shows:

[0022] Figure 1 shows a schematic view of a gas combustion engine for

[0023] Execution of the method according to the invention.

[0024] Description of the exemplary embodiment

[0025] With reference to Figure 1, a gas combustion engine 1 and a method for operating the gas combustion engine according to a preferred embodiment of the invention are described in detail below.

[0026] Figure 1 schematically shows a gas-fired internal combustion engine 1, which uses hydrogen as fuel gas. The hydrogen is stored under high pressure in a gas tank 2.

[0027] The gas tank 2 is connected via a line section 4 to a first combustion chamber 11 and a second combustion chamber 12 of the gas combustion engine.

[0028] In section 4 of the pipeline, a safety valve 3 is located directly adjacent to the gas tank 2. The safety valve 3 closes when the gas-powered engine 1 is switched off, ensuring that the fuel gas is safely stored in the gas tank 2. The safety valve 3 can be located directly at the gas tank 2 or at a distance, but nearby, with a short pipeline connection to the gas tank 2.

[0029] The hydrogen from gas tank 2 is typically fed via a pressure reducer into line section 4 and from there, as indicated by arrow A, to the first and second combustion chambers 11 and 12. The pressure in line section 4 is significantly higher than ambient pressure. During normal operation, hydrogen is injected into the first combustion chamber 11 and the second combustion chamber 12 via gas injectors 8 connected to line section 4. The safety valve 3 is open, allowing fuel gas from gas tank 2 to flow to the gas injectors 8 via line section 4.

[0030] When the gas-powered engine is to be shut down, the shutdown method according to the invention is used. In a first step, the safety valve 3 is closed by a signal from a control unit 10. This isolates the gas tank 2 from the line section 4. However, at the time of shutdown, despite the pressure reducer, a very high pressure still prevails in the line section 4, which is significantly higher than the ambient pressure. If the gas-powered engine is shut down in this condition, a very high pressure would therefore prevail in the line section 4. This creates a risk of hydrogen leakage from the line section 4. In unfavorable cases, a leak from the line section 4 could occur, for example at sealing points or the like, and accumulate to form a flammable mixture.However, this would pose a danger to users of the internal combustion engine as well as to the area surrounding the engine, since the ignitable mixture could pose a risk of explosion at any time.

[0031] Therefore, in the method according to the invention, after the gas-fired internal combustion engine has been shut down and the safety valve 3 has closed, a strategy for pressure reduction in the line section 4 is proposed. Here, the injection of fuel grass into the first combustion chamber 11 by the control unit 10 is prevented. That is, during the shutdown process, the first combustion chamber 11 is no longer supplied with fuel gas. The second combustion chamber 12, however, continues to be supplied with gaseous fuel in normal operation.

[0032] However, by decoupling the first combustion chamber 11 from the gas injection, additional work loss is generated there during the shutdown process, thereby increasing the load on the gas-fired engine and consequently the consumption of fuel gas in the second combustion chamber 12. Here, an exhaust valve 5 on the first combustion chamber 11 is opened by the control unit 10, so that the additional work loss is generated without combustion. Specifically, the exhaust valve 5 is opened shortly before the end of the compression stroke, allowing compressed air to be released into the exhaust tract 6. Thus, the compressed air in the first combustion chamber 11, which is not ignitable due to the absence of hydrogen injection, cannot deliver any work to the piston; instead, the work loss must be compensated for by the work generated in the second combustion chamber 12.However, this increases the fuel gas demand in the second combustion chamber 12, so that within a short time a pressure can be used in line section 4, in which a certain quantity of gas is still present at high pressure. This causes the pressure in line section 4 to preferably drop to ambient pressure.

[0033] Thus, when the gas-fired internal combustion engine 1 is switched off, at least one cylinder operates in a decompression process, and at least one other cylinder is supplied with fuel gas normally, although this second cylinder requires more fuel gas due to the additional work loss. This results in rapid emptying and therefore a pressure drop in line section 4.

[0034] It should be noted that instead of directly controlling the exhaust valve 5 via the control unit 10, an exhaust camshaft can also be provided which actuates the exhaust valve 5 by means of an additional profile on the exhaust camshaft, which is activated when the gas-powered internal combustion engine is switched off. This can be activated, for example, by an axial displacement of the exhaust camshaft. It should also be noted that it is possible to arrange an additional valve (decompression valve) on the first combustion chamber 11, which is specifically controlled by the control unit 10 during the shutdown process in order to connect the first combustion chamber 11 to the exhaust tract 6 for pressure reduction in the first combustion chamber 11.

[0035] Thus, an increase in work loss in combustion chamber 11 of the gas-fired engine during a shutdown process can generate an increased power demand in one or more other combustion chambers, leading to increased fuel gas consumption and consequently a rapid pressure drop in line section 4. This allows line section 4 to be emptied as quickly as possible, ideally down to ambient pressure, during the shutdown process, eliminating the risk of leakage from line section 4 into the environment when the gas-fired engine is shut down.

Claims

Claims 1. Method for operating a gas-powered internal combustion engine during a shutdown process of the gas-powered internal combustion engine, comprising the steps of: closing a safety valve (3) which interrupts a connection to a gas tank (2), Opening a valve (5) on a first combustion chamber (11) of the gas engine to release a connection to an exhaust tract (6) in order to generate a throttling loss when the gas engine is switched off and to increase the load on the gas engine, wherein no fuel gas is supplied to the first combustion chamber (11) from a line section (4) connecting the safety valve (3) to the first combustion chamber (11), and combustion of fuel gas in a second combustion chamber (12), wherein fuel gas consumption is increased by the increased load generated in the first combustion chamber (11).

2. Method according to claim 1, wherein the valve (5) on the first combustion chamber (11) is opened until a predetermined pressure value, in particular atmospheric pressure, is reached in the line area (4).

3. Method according to one of the preceding claims, wherein the valve (5) on the first combustion chamber (11) is only partially opened.

4. Method according to one of the preceding claims, wherein the valve (5) is opened shortly before reaching top dead center in the first combustion chamber (11).

5. Method according to one of the preceding claims, wherein the gas internal combustion engine has an even number of combustion chambers (11, 12), wherein only half of the combustion chambers or less than half of the combustion chambers are deprived of fuel gas so that they can provide the additional load.

6. Method according to any of the preceding claims, wherein the valve (5) is an exhaust valve of the first combustion chamber (11).

7. Method according to claim 6, wherein the gas internal combustion engine has an exhaust camshaft for actuating the exhaust valve (5), which is provided with an additional profile which is activated when the gas internal combustion engine is switched off in order to actuate the exhaust valve (5) on the first combustion chamber (11).

8. Method according to any one of claims 1 to 5, wherein the valve is an additional decompression valve which is arranged on the first combustion chamber (11) and is actuated by the control unit (10) when the gas internal combustion engine is switched off.

9. Method according to one of the preceding claims, wherein the opening stroke of the valve (5) remains constant during a working cycle.

10. Gas internal combustion engine, in particular hydrogen internal combustion engine, configured for carrying out a method according to one of the preceding claims.

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