Internal combustion engine which burns at least ammonia as fuel, and methods for operating the same.

Abstract

internal combustion engine (10) which is designed to burn at least a portion of ammonia as fuel, with a fuel tank (11) which is designed to hold the fuel which is at least partly composed of ammonia, with a fuel supply system (13) designed to supply the fuel held in the fuel tank (11) to the cylinders (34) of the internal combustion engine (10) for combustion, with an SCR exhaust aftertreatment system (19), characterized by a purge gas system (16) which is designed to discharge the fuel via purge gas from the fuel supply system (13) after the combustion of the fuel has ceased, a collection tank (14) which is designed to collect and store fuel from the fuel supply system (13) with the purge gas, namely fuel which is discharged from the fuel supply system (13) via the purge gas after the combustion of the fuel has ceased, wherein the collection tank (14) is further designed to supply the fuel collected in the collection tank (14) to the exhaust gas of the internal combustion engine (10) as a reducing agent, an ammonia sensor (29) which is configured to measure an ammonia content in the exhaust gas of the internal combustion engine (10) upstream of the SCR exhaust aftertreatment system (19), a first nitrogen oxide sensor (30) which is set up to measure a nitrogen oxide content in the exhaust gas of the internal combustion engine (10) upstream of the SCR exhaust aftertreatment system (19), a second nitrogen oxide sensor (31) which is configured to measure a nitrogen oxide content in the exhaust gas of the internal combustion engine (10) downstream of the SCR exhaust aftertreatment system (19), a control unit (25) which is set up to adjust a mass flow or volume flow rate, depending on the measured ammonia content in the exhaust gas and further depending on the measured nitrogen oxide content in the exhaust gas, which is supplied to the exhaust gas from the collection tank (14) as a reducing agent.

Description

[0001] The invention relates to an internal combustion engine. Furthermore, the invention relates to a method for operating an internal combustion engine.

[0002] Large engines, such as those used as internal combustion engines on ships, are increasingly being designed as gas engines or dual-fuel engines. Gas engines burn a gaseous fuel, such as natural gas. Dual-fuel engines can burn a gaseous fuel, such as natural gas, in a gas-fuel operating mode and a liquid fuel, such as diesel, in a liquid-fuel operating mode.

[0003] In practice, there are also attempts to operate internal combustion engines with ammonia as fuel. The fuel is formed at least partially from ammonia. Using a fuel that is formed at least partially from ammonia can reduce CO2 emissions compared to internal combustion engines that use natural gas or diesel as fuel. However, due to the toxicity of ammonia, particularly its corrosive effects, reliable measures must be taken to prevent ammonia from entering the environment.

[0004] US 2011 / 0 265 463 A1 discloses an internal combustion engine according to the preamble of claim 1.

[0005] DE 23 60 255 A1 discloses further prior art.

[0006] KR 10 2021 0 145 029 A1 discloses an internal combustion engine according to the preamble of claim 1.

[0007] KR 10 2021 0 145 044 A, KR 10 2021 0 145 031 A and WO 2022 / 045 184 A1 disclose further prior art.

[0008] Based on this, the invention is based on the object of creating a novel internal combustion engine and a method for operating the internal combustion engine.

[0009] This object is achieved by an internal combustion engine according to claim 1.

[0010] The internal combustion engine according to the invention is designed to burn at least a proportion of ammonia as fuel.

[0011] The internal combustion engine according to the invention has a fuel tank which is designed to hold the fuel which is at least partially formed from ammonia.

[0012] The internal combustion engine according to the invention has a fuel supply system which is designed to supply the fuel held in the fuel tank, which is at least partially formed by ammonia, to cylinders of the internal combustion engine for combustion.

[0013] The internal combustion engine according to the invention has a purge gas system which is designed to remove the fuel from the fuel supply system via purge gas after the end of the combustion of the fuel.

[0014] The internal combustion engine according to the invention further comprises a collecting tank configured to collect and store fuel with the purge gas from the fuel supply system. This is fuel that is discharged from the fuel supply system via the purge gas after the end of fuel combustion, which is formed at least partially from ammonia, and optionally additional fuel from the fuel supply system that escapes from the fuel supply system due to leaks that may occur intentionally or unintentionally.

[0015] The collecting tank of the internal combustion engine according to the invention is further configured to supply the fuel removed from the internal combustion engine and collected in the collecting tank, which fuel is at least partially formed by ammonia, to the exhaust gas of the internal combustion engine as a reducing agent.

[0016] The internal combustion engine according to the invention burns a fuel that is at least partially composed of ammonia. This allows CO2 emissions to be significantly reduced.

[0017] The fuel, which is at least partially formed by ammonia and which is removed, for example, from the fuel supply system of the internal combustion engine according to the invention after the end of combustion, is collected in a collecting tank of the internal combustion engine. The fuel, which is at least partially formed by ammonia, is not only collected in the collecting tank but is also fed from the collecting tank to the exhaust gas of the internal combustion engine as a reducing agent.

[0018] Ammonia, which is removed from the fuel supply system of the internal combustion engine according to the invention after the end of combustion, can thus be put to secondary use, namely as a reducing agent in the exhaust gas.

[0019] Preferably, the fuel tank is further configured to supply ammonia from the fuel tank as a reducing agent to the exhaust gas of the internal combustion engine, namely in the form of the fuel stored in the fuel tank. If a sufficient amount of ammonia is not available in the collection tank to ensure adequate nitrogen oxide reduction in the exhaust gas, ammonia can also be supplied to the exhaust gas from the fuel tank as a reducing agent.

[0020] The internal combustion engine according to the invention has an ammonia sensor which is configured to measure an ammonia content in the exhaust gas of the internal combustion engine upstream of an SCR exhaust aftertreatment system.

[0021] Furthermore, the internal combustion engine according to the invention has a control unit which is designed to set a mass flow or volume flow depending on the measured ammonia content in the exhaust gas, which is supplied to the exhaust gas as a reducing agent from the collecting container and optionally from the fuel tank.

[0022] The ammonia sensor can measure the ammonia content in the exhaust gas. Depending on the measured ammonia content in the exhaust gas, the volumetric flow or mass flow is determined. This flow is added to the exhaust gas as a reducing agent from the collection tank and, if applicable, from the fuel tank. This is done to provide the exhaust gas with a sufficient amount of ammonia to reduce nitrogen oxides in the exhaust gas.

[0023] The internal combustion engine according to the invention further comprises a first nitrogen oxide sensor and a second nitrogen oxide sensor, wherein the first nitrogen oxide sensor is configured to measure a nitrogen oxide content in the exhaust gas of the internal combustion engine upstream of the SCR exhaust gas aftertreatment system, and wherein the second nitrogen oxide sensor is configured to measure a nitrogen oxide content in the exhaust gas of the internal combustion engine downstream of the SCR exhaust gas aftertreatment system, and wherein the control unit is configured to adjust the mass flow or volume flow, which is supplied to the exhaust gas from the collecting container and optionally from the fuel tank as a reducing agent, also as a function of the measured nitrogen oxide contents in the exhaust gas.

[0024] If, in addition to the measured ammonia content, the nitrogen oxide content measured by the nitrogen oxide sensors upstream and downstream of the SCR exhaust gas aftertreatment system is also used to determine the mass flow or volume flow that is added to the exhaust gas from the collection container and / or from the fuel tank as a reducing agent, a particularly advantageous reduction of nitrogen oxide in the exhaust gas can be ensured.

[0025] The method according to the invention for operating the internal combustion engine is defined in claim 4.

[0026] Preferred developments of the invention will become apparent from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail, without being limited thereto, with reference to the drawings. Herein: Fig. 1 a first internal combustion engine according to the invention, Fig. 2 a second internal combustion engine according to the invention.

[0027] Fig. Figure 1 shows a block diagram of an internal combustion engine 10 according to the invention, which is configured to burn at least a portion of ammonia as fuel. The internal combustion engine 10 has a fuel tank 11 in which the fuel to be burned is stored, the fuel to be burned being formed at least partially from ammonia.

[0028] For combustion of the fuel, the fuel can be taken from the fuel tank 11 and supplied to cylinders 34 of the internal combustion engine 10 via a fuel line 12 of a fuel supply system 13.

[0029] The fuel tank 11 is therefore configured to hold the fuel, which is at least partially formed by ammonia, for combustion in the internal combustion engine 13. The fuel supply system 13 is configured to supply the fuel held in the fuel tank 11, which is at least partially formed by ammonia, to the cylinders 34 of the internal combustion engine 10 for combustion.

[0030] The internal combustion engine 10 further comprises a collecting tank 14. The collecting tank 14 is configured to collect the fuel to be removed or discharged from the fuel supply system 13 after the end of the combustion of the fuel, which fuel is formed at least partially from ammonia.

[0031] The removal or discharge of the fuel, which is at least partially formed by ammonia, from the fuel supply system 13 can be achieved, for example, by purging the fuel supply system 13 using purge gas, which is supplied to the fuel supply system 13 via a purge gas line 15 of a purge gas system 16. The purge gas then enters the area of ​​the collecting tank 14 together with the fuel, which is at least partially formed by ammonia and is discharged from the fuel supply system 13 using the purge gas.

[0032] Preferably, a pump 17 leads the mixture of purge gas and fuel, which is at least partially formed by ammonia, from the fuel supply system 13 and to the collecting container 14, wherein between the pump 17 and the collecting container 14 in Fig. 1 a valve 18 is switched.

[0033] Fig. 1 further shows an exhaust aftertreatment system embodied as an SCR exhaust aftertreatment system 19. Exhaust gas generated during the combustion of the fuel, which is at least partially formed from ammonia, in the cylinders 34 of the internal combustion engine 10 is fed to the SCR exhaust aftertreatment system 19 via an exhaust line 20 extending between the cylinders 34 of the internal combustion engine 10 and the SCR exhaust aftertreatment system 19.

[0034] In an exhaust aftertreatment system designed as an SCR exhaust aftertreatment system 19, a selective catalytic reduction of nitrogen oxides in the exhaust gas takes place with the aid of a reducing agent. The functioning of an SCR exhaust aftertreatment system 19 is generally known and requires no further explanation. The purified exhaust gas is discharged into the environment via another exhaust line 21.

[0035] The collecting container 14 is not only designed to collect the fuel which is discharged from the fuel supply system 13 after the end of the combustion of the fuel and which is at least partially formed by ammonia, but rather the collecting container 14 is also designed to supply the fuel previously discharged from the fuel supply system 13 to the exhaust gas of the internal combustion engine 10 as a reducing agent when the combustion of the fuel is subsequently resumed, namely in Fig. 1 upstream of the SCR exhaust aftertreatment system 19 in the area of ​​the exhaust line 20. For this purpose, a line 22 leads from the collecting tank 14 to the exhaust line 20, into which a valve 23 is connected. The valve 23 can be opened and closed in a controlled manner via an actuator 24, namely from a control device 25.

[0036] Furthermore, the fuel tank 11 is configured to supply ammonia as a reducing agent to the exhaust gas of the internal combustion engine 10 via a line 26, namely in the form of the ammonia-containing fuel that is stored in the fuel tank 11 and is at least partially formed by ammonia. A valve 27 is connected to this line 26. The valve 27 is opened and closed by an actuator 28 controlled by the control unit 25. Via the line 26, fuel, and thus ammonia as a reducing agent, can be supplied to the exhaust gas of the internal combustion engine 10 in the region of the exhaust line 20.

[0037] Fig. 1 shows that in the preferred embodiment, the internal combustion engine 10 has an ammonia sensor 29 and two nitrogen oxide sensors 30 and 31.

[0038] With the aid of the ammonia sensor 29, the ammonia content in the exhaust gas of the internal combustion engine 10, namely in the exhaust gas of the cylinders 34, can be measured upstream of the SCR exhaust aftertreatment system 19.

[0039] The first nitrogen oxide sensor 30 can measure the nitrogen oxide content in the exhaust gas upstream of the SCR exhaust aftertreatment system 19. The second nitrogen oxide sensor 31 can measure the nitrogen oxide content in the exhaust gas downstream of the SCR exhaust aftertreatment system 19.

[0040] It is provided that the control unit 25 determines a mass flow or volume flow depending on the ammonia content in the exhaust gas measured by means of the ammonia sensor 29 upstream of the SCR exhaust aftertreatment system 19, which is supplied to the exhaust gas via the line 26 starting from the collecting tank 14 and optionally starting from the fuel tank 11 via the line 22, in order to provide the amount of ammonia in the exhaust gas upstream of the SCR exhaust aftertreatment system 19 that is required for a desired catalytic conversion of the nitrogen oxide in the exhaust gas.

[0041] If an ammonia content is already present in the exhaust gas of the internal combustion engine 10 leaving the cylinders 34, in particular as a result of incomplete combustion of the ammonia, the mass flow or volume flow which is supplied to the exhaust gas from the collecting container 14 and optionally from the fuel tank 11 can be reduced.

[0042] The control unit 25 controls the actuators 24, 28 of the valves 23, 27 to provide the corresponding mass flow or volume flow.

[0043] Preferably, the control unit 25 determines the mass flow or volume flow which is supplied to the exhaust gas upstream of the SCR exhaust aftertreatment system 19 from the collection container 14 and optionally from the fuel tank 11 as a reducing agent, not only as a function of the ammonia content in the exhaust gas measured by means of the ammonia sensor 29, but preferably also as a function of the nitrogen oxide content in the exhaust gas, which is measured by means of the nitrogen oxide sensors 30, 31.

[0044] Fig. 2 shows a modification of the internal combustion engine 10 of Fig. 1, whereby in order to avoid unnecessary repetition, only those details are discussed below, through which the embodiment of the Fig. 2 of the embodiment of the Fig. 1. The same reference numbers are used for the same assemblies, so that with regard to the assemblies used with the same reference numbers for the internal combustion engine 10 of the Fig. 2 to the statements on the internal combustion engine 10 of Fig. 1 is referred to.

[0045] Fig. 2 differs from Fig. 1 in that the fuel 17 discharged from the fuel supply system 13 by means of the pump 17 after combustion has ended is first stored in an intermediate tank 32 before the fuel then flows from the intermediate tank 32 into the area of ​​the collecting tank 14. In the intermediate tank 32, the fuel discharged from the fuel supply system 13 is mixed with water, which is supplied to the intermediate tank 32 from a water tank 33. The water from the water tank 33 can also be supplied to the collecting tank 14 from the water tank 33.

[0046] The collection tank 14 is preferably associated with an ammonia sensor (not shown), by means of which the ammonia content of the aqueous solution in the collection tank 14 can be measured in order to adjust the amount of ammonia which is supplied to the collection tank 14 from the fuel tank 11 via the line 26 and the valve 27 so that the aqueous solution in the collection tank 14 has a desired ammonia content.

[0047] Starting from the collecting tank 14, an ammonia-containing aqueous solution can be supplied to the exhaust gas upstream of the SCR exhaust aftertreatment system 19 via the line 22 and the valve 23. With regard to all other details, the embodiment of the Fig. 2 with the embodiment of the Fig. 1, so that to avoid unnecessary repetition for the embodiment of the Fig. 2 on the embodiment of the Fig. 1 is referred to.

[0048] The invention accordingly relates to an internal combustion engine 10 and a method for operating the internal combustion engine 10, wherein the internal combustion engine 10 combusts a fuel that is at least partially formed from ammonia. This fuel is supplied to the cylinders 34 of the internal combustion engine 10 from a fuel tank 11.

[0049] Exhaust gas leaving the cylinders 34 of the internal combustion engine 10 enters the area of ​​an SCR exhaust aftertreatment system 19. Ammonia is added to the exhaust gas, starting from the collection tank 14 and, if applicable, from the fuel tank 11.

[0050] The volume flow or mass flow of ammonia added to the exhaust gas from the collection tank 14 and, if applicable, from the fuel tank 11 is determined based on the measured ammonia content and the measured nitrogen oxide content in the exhaust gas. A nitrogen oxide content upstream of the SCR exhaust aftertreatment system 19 and downstream of the SCR exhaust aftertreatment system 19 is taken into account.

[0051] The invention is based on the idea of ​​using the fuel collected in a collecting tank 14 after combustion has ended in an internal combustion engine 10 in which the combusted fuel is at least partially formed by ammonia as a reducing agent during a subsequently resumed fuel combustion and supplying it to the exhaust gas of the internal combustion engine 10. This occurs depending on the ammonia content in the exhaust gas, possibly in combination with a supply of fuel into the exhaust gas from the fuel tank 11.

Claims

[1] Internal combustion engine (10) which is designed to burn at least ammonia as fuel, with a fuel tank (11) which is designed to hold the fuel which is at least partly formed from ammonia, with a fuel supply system (13) which is designed to supply the fuel held in the fuel tank (11) to cylinders (34) of the internal combustion engine (10) for combustion, with an SCR exhaust aftertreatment system (19), characterized by a purge gas system (16) which is designed to remove the fuel from the fuel supply system (13) via purge gas after the end of the combustion of the fuel, a collecting tank (14) which is designed to collect and store fuel from the fuel supply system (13) with the purge gas, namely fuel which is discharged from the fuel supply system (13) via the purge gas after the combustion of the fuel has ended, wherein the collecting tank (14) is further designed to supply the fuel collected in the collecting tank (14) to the exhaust gas of the internal combustion engine (10) as a reducing agent, an ammonia sensor (29) which is designed to measure an ammonia content in the exhaust gas of the internal combustion engine (10) upstream of the SCR exhaust gas aftertreatment system (19), a first nitrogen oxide sensor (30) which is designed to measure a nitrogen oxide content in the exhaust gas of the internal combustion engine (10) upstream of the SCR exhaust gas aftertreatment system (19), a second nitrogen oxide sensor (31) which is designed to measure a nitrogen oxide content in the exhaust gas of the internal combustion engine (10) downstream of the SCR exhaust gas aftertreatment system (19), a control unit (25) which is designed to set a mass flow or volume flow depending on the measured ammonia content in the exhaust gas and further depending on the measured nitrogen oxide content in the exhaust gas, which is supplied to the exhaust gas from the collecting container (14) as a reducing agent. [2] Internal combustion engine according to claim 1, characterized byin that the fuel tank (11) is designed to supply ammonia as a reducing agent to the exhaust gas of the internal combustion engine (10) from the fuel tank (11), wherein the control unit (25) is designed to set a mass flow or volume flow depending on the measured ammonia content in the exhaust gas and further depending on the measured nitrogen oxide content in the exhaust gas, which is supplied to the exhaust gas from the fuel tank (11) as a reducing agent. [3] Internal combustion engine according to one of claims 1 to 2, characterized by in that the collecting container (14) is designed to store the collected fuel in the form of an aqueous solution, wherein water can be supplied to the collecting container (14) from a water tank (33), and wherein the collecting container (14) is designed to supply the aqueous solution to the exhaust gas of the internal combustion engine (10) as a reducing agent. [4] Method for operating an internal combustion engine (10) according to one of claims 1 to 3, wherein, when the fuel which is at least partly formed by ammonia is burned in the internal combustion engine (10), the fuel is supplied to the cylinders (34) of the internal combustion engine (10) from the fuel tank (11), with the aid of the purge gas system (16) after the combustion of the fuel from the fuel supply system (13) has ended, fuel is removed from the fuel supply system (13) via purge gas, and wherein the fuel removed from the fuel supply system (13) via the purge gas is collected and stored with the purge gas in the collecting container (14), an ammonia content in the exhaust gas of the internal combustion engine (10) is measured upstream of the SCR exhaust gas aftertreatment system (19), a nitrogen oxide content in the exhaust gas of the internal combustion engine (10) upstream of the SCR exhaust gas aftertreatment system (19) and a nitrogen oxide content in the exhaust gas of the internal combustion engine downstream of the SCR exhaust gas aftertreatment system (19) is measured, wherein, when the fuel which is at least partially formed by ammonia is burned in the internal combustion engine (10), ammonia is supplied to the exhaust gas from the collecting tank (14) as a reducing agent, in such a way that a mass flow or volume flow is set as a function of the measured ammonia content and also as a function of the measured nitrogen oxide content, which is supplied to the exhaust gas from the collecting tank (14) as a reducing agent. [5] Method according to claim 4, characterized bythat, depending on the measured ammonia content and also depending on the measured nitrogen oxide content, a mass flow or volume flow is set which is supplied to the exhaust gas from the fuel tank (11) as a reducing agent.

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