Method for determining the hydrogen content in the exhaust gas of a hydrogen internal combustion engine and hydrogen internal combustion engine

Abstract

The present invention relates to a method for determining the hydrogen content in an exhaust tract (130) of a hydrogen internal combustion engine (100) and to a hydrogen internal combustion engine (100) which has combustion chambers (110) and an oxygen sensor (140) arranged in the exhaust tract (130) of the hydrogen internal combustion engine (100), which oxygen sensor is designed to generate an oxygen signal which is representative of the oxygen content in the exhaust gas of the hydrogen internal combustion engine (100).The method according to the invention comprises determining a predetermined operating mode of the hydrogen internal combustion engine (100) during which substantially no combustion of an air-hydrogen mixture takes place within the combustion chambers (110), receiving an oxygen signal from the oxygen sensor (140) during the predetermined operating mode of the internal combustion engine (100), and determining the hydrogen content in the exhaust gas of the hydrogen internal combustion engine (100) based at least partially on the oxygen signal received from the oxygen sensor (140).

Description

[0001] The present invention relates to a method for determining the hydrogen content in the exhaust gas of a hydrogen internal combustion engine and hydrogen internal combustion engine, in particular a hydrogen internal combustion engine with crankcase ventilation, as well as a method for monitoring the crankcase ventilation.

[0002] In (piston) internal combustion engines with a closed crankcase, deviations from atmospheric pressure occur not only in the working chambers but also below the pistons. These are caused, on the one hand, by the volume changes caused by the rotating pistons and, on the other hand, by the gases accumulating in the crankcase from the working process.

[0003] In combustion engines, so-called blowby gases always occur in the crankcase. Since the crankcase is a closed space, the pressure would constantly increase without ventilation. To prevent this, the blowby gases, which contain combustion products and unburned hydrogen, can be specifically removed from the crankcase. The ideal relative crankcase pressure is in the slightly negative range of around -2 mbar, since under these conditions the engine does not tend to "sweat out" lubricating oil. If the negative pressure is significantly greater (the value is engine-specific and depends on the design of the sealing systems), there is a risk that air contaminated with dirt particles and / or pure hydrogen will be sucked in via the shaft seals and gaskets on the crankcase. This would lead to increased wear on internal components.During venting, oil droplets generated by rotating components are inevitably carried out of the crankcase.

[0004] During operation of the hydrogen internal combustion engine, in particular during overrun fuel cut-off phases of the hydrogen internal combustion engine, high pressure in the intake manifold can cause the gases trapped in the crankcase (in particular pure hydrogen present there) to at least partially pass past the pistons into the combustion chambers and thus into the exhaust tract of the hydrogen internal combustion engine.

[0005] Furthermore, the ventilation line can become blocked, torn off, or the connection to the intake tract can be missing. This restricts crankcase ventilation, allowing pollutants and pure hydrogen to escape unhindered from the crankcase into the environment. Therefore, the hydrogen content in the exhaust gas of the hydrogen internal combustion engine and / or in the crankcase, as well as the proper functioning of the crankcase ventilation, should be monitored. If the crankcase ventilation is not functioning properly, pure hydrogen will accumulate in the crankcase and / or be released unhindered into the environment in the event of a leak. If temperature-dependent explosion limits regarding the hydrogen content in the exhaust gas and / or in the crankcase of the hydrogen internal combustion engine are exceeded, there is also a risk of ignition of the air-hydrogen mixture.

[0006] DE 10 2021 213 901 B3 discloses a method for monitoring the ventilation of a crankcase of a fossil internal combustion engine. The method known therefrom comprises determining a predetermined operating mode of the internal combustion engine during which substantially no combustion of an air-fuel mixture takes place within the combustion chambers, determining a nitrogen oxide content in the exhaust gas of the internal combustion engine during the predetermined operating mode of the internal combustion engine by means of an exhaust gas sensor and determining a functional ventilation of the crankcase if the nitrogen oxide value determined during the predetermined operating mode of the internal combustion engine exceeds a predetermined nitrogen oxide threshold value.

[0007] DE 10 2021 005 095 A1 discloses a control unit for a powertrain comprising a hydrogen engine and an exhaust gas aftertreatment system. The exhaust gas aftertreatment system has a first DeNOx system. The control unit is configured to detect a content of a component of an exhaust gas upstream or downstream of the first DeNOx system and to control the hydrogen engine such that an H2 content of the exhaust gas is adjusted based on the detected content.

[0008] DE 10 2007 021 827 A1 relates to an exhaust gas purification system for a hydrogen engine and in particular to an exhaust gas purification system for a hydrogen engine which makes it possible to free hydrogen gases from certain components which are contained in the exhaust gas after combustion in the hydrogen engine.

[0009] DE 10 2021 005 649 A1 discloses a hydrogen engine with at least one combustion chamber, which is associated with at least one intake valve, through which at least fresh air can be introduced into the combustion chamber, and an injection valve, by means of which hydrogen can be injected directly into the combustion chamber as a gaseous fuel. The injection valve is arranged off-center with respect to the combustion chamber, and the hydrogen engine is designed to cause a swirling flow of fresh air flowing into the combustion chamber via the open intake valve when the intake valve opens.

[0010] The present invention is essentially based on the object of determining and monitoring the hydrogen content in the exhaust gas of a hydrogen internal combustion engine in a simple and cost-effective manner.

[0011] This object is achieved by a method according to independent claim 1 and a hydrogen internal combustion engine according to independent claim 14. Advantageous embodiments are specified in the subclaims.

[0012] The present invention is essentially based on the idea that during predetermined operating modes during which no combustion of an air-hydrogen mixture occurs in the combustion chambers of the hydrogen internal combustion engine, for example during an overrun fuel cut-off phase, the hydrogen content in the exhaust gas of the hydrogen internal combustion engine is determined. The determined hydrogen content in the exhaust gas can then be an indication of the hydrogen content in the crankcase, where excessively high hydrogen contents can lead to an increased risk of explosion. This can make a hydrogen sensor in the crankcase superfluous, and the oxygen sensor, which is usually already installed, can be used instead. Furthermore, by determining the hydrogen content in the exhaust gas of the hydrogen internal combustion engine, the functionality of the crankcase ventilation can be monitored.In particular, during the aforementioned predetermined operating modes, the exhaust gases trapped in the crankcase return to the combustion chambers and thus the exhaust tract via the ventilation line and / or as so-called blow-by exhaust gases and can thus be detected by the oxygen sensor arranged in the exhaust tract.

[0013] Consequently, according to a first aspect of the present invention, a method for determining the hydrogen content in an exhaust tract of a hydrogen internal combustion engine is disclosed, which has combustion chambers and an oxygen sensor arranged in the exhaust tract of the hydrogen internal combustion engine, which oxygen sensor is designed to generate an oxygen signal that is representative of the oxygen content in the exhaust gas of the hydrogen internal combustion engine.The method according to the invention comprises determining a predetermined operating mode of the hydrogen internal combustion engine during which substantially no combustion of an air-hydrogen mixture takes place within the combustion chambers, receiving an oxygen signal from the oxygen sensor during the predetermined operating mode of the internal combustion engine, and determining the hydrogen content in the exhaust gas of the hydrogen internal combustion engine based at least in part on the oxygen signal received from the oxygen sensor.

[0014] With the method according to the invention, a hydrogen sensor designed to directly determine the hydrogen content in the crankcase is not necessary. Instead, the oxygen sensor that is usually already present in the exhaust tract can be used to determine the hydrogen content in the exhaust gas and, in turn, to determine the hydrogen content in the crankcase. The oxygen sensor is designed to detect the oxygen content in the exhaust gas. The invention takes advantage of the fact that the hydrogen present in the exhaust gas acts as a rich gas. This means that the hydrogen reacts with the oxygen in the exhaust gas to form water on the electrodes and catalytic surfaces of the oxygen sensor. Consequently, the oxygen content indicated by the oxygen sensor is lower than the actual oxygen content because the hydrogen present in the exhaust gas reacts with a corresponding proportion of oxygen in the exhaust gas.The difference between the actual oxygen content and the oxygen content indicated by the oxygen sensor can be indicative of the hydrogen content in the exhaust gas, since there is a correlation between the change in the oxygen signal and the hydrogen concentration, from which the hydrogen content in the exhaust gas can subsequently be determined. However, since the actual oxygen content is known in the predetermined operating modes, for example, approximately 20.9% in air, the invention allows the hydrogen content in the exhaust gas to be determined based on the oxygen signal from the oxygen sensor. Taking into account the exhaust gas mass flow of the supplied intake air, the hydrogen concentration prevailing in the crankcase can then be determined or estimated.

[0015] In a preferred embodiment, the method according to the invention further comprises determining the oxygen content in the exhaust gas of the hydrogen internal combustion engine based on the oxygen signal received from the oxygen sensor. The determination of the hydrogen content in the exhaust gas of the hydrogen internal combustion engine is based at least partially on the determined oxygen content.

[0016] In an advantageous embodiment, the method according to the invention further comprises determining the actual oxygen content in the exhaust gas of the hydrogen internal combustion engine based on the determined predetermined operating mode of the hydrogen internal combustion engine and forming an oxygen content difference between the determined actual oxygen content and the oxygen content determined based on the oxygen signal received from the oxygen sensor. The determination of the hydrogen content in the exhaust gas of the hydrogen internal combustion engine is based at least partially on the determined oxygen content difference.

[0017] For example, the actual oxygen content during an overrun cut-off phase of the hydrogen internal combustion engine is approximately 20.9%, since only air flows through the hydrogen internal combustion engine during the overrun cut-off phase and the oxygen content in the air is approximately 20.9%.

[0018] Advantageously, the oxygen signal is received after a predetermined period of time has elapsed after the predetermined operating mode of the hydrogen internal combustion engine has been determined. The predetermined period of time is preferably approximately 3 seconds, preferably approximately 1 second. This can ensure, for example, that the exhaust gases generated during the combustion of the air-hydrogen mixture in the combustion chambers have been completely expelled from the combustion chambers and have already flowed past the oxygen sensor, so that during the predetermined operating mode, the exhaust gas measured by the oxygen sensor must originate from the crankcase and the intake manifold.

[0019] In an alternative embodiment, it may be preferable for the oxygen content to be determined only when an air mass integral in the exhaust tract exceeds a predetermined air mass integral threshold value. In particular, the time until the oxygen sensor can measure the exhaust gases originating from the crankcase depends on the mass flow rate and the volume of the exhaust tract. Consequently, in such an alternative embodiment, it is advantageous to determine the oxygen content only when the air mass integral in the exhaust tract exceeds the predetermined air mass integral threshold value. In addition, the oxygen sensor requires a certain amount of time to stabilize at the oxygen measurement value.

[0020] In a preferred embodiment of the method according to the invention, the predetermined operating mode of the hydrogen internal combustion engine includes an overrun fuel cut-off phase of the hydrogen internal combustion engine. In particular, the predetermined operating mode describes an operating mode of the internal combustion engine in which no hydrogen injection occurs and the hydrogen internal combustion engine is dragged by the inertia of its components.

[0021] In a further advantageous embodiment, the method according to the invention further comprises determining a functional ventilation of the crankcase if the hydrogen content in the exhaust gas of the hydrogen internal combustion engine determined during the predetermined operating mode of the hydrogen internal combustion engine exceeds a predetermined first hydrogen content threshold value.

[0022] In yet another preferred embodiment, the method according to the invention further comprises determining a malfunctioning crankcase ventilation system if the hydrogen content in the exhaust gas of the hydrogen internal combustion engine, determined during the predetermined operating mode of the hydrogen internal combustion engine, falls below a predetermined first hydrogen content threshold value. In such an embodiment, it may also be advantageous to issue a warning to the operator of the hydrogen internal combustion engine if a malfunctioning crankcase ventilation system has been detected.

[0023] Preferably, the predetermined first hydrogen content threshold is between about 0.3% and about 0.6%, and more preferably about 0.5%.

[0024] In a further preferred embodiment, the method according to the invention further comprises determining an exhaust gas mass flow through the exhaust tract of the hydrogen internal combustion engine and determining the hydrogen content in the crankcase of the hydrogen internal combustion engine at least partially based on the determined hydrogen content in the exhaust gas of the hydrogen internal combustion engine and at least partially based on the determined exhaust gas mass flow through the exhaust tract of the hydrogen internal combustion engine.

[0025] In yet another preferred embodiment, the method according to the invention further comprises determining that the hydrogen content in the crankcase of the hydrogen internal combustion engine exceeds a predetermined second hydrogen content threshold, and at least partially venting the crankcase if it has been determined that the hydrogen content in the crankcase of the hydrogen internal combustion engine exceeds the predetermined second hydrogen content threshold. During venting of the crankcase, the crankcase can be actively purged, for example by injecting fresh air, in order to reduce the hydrogen content in the crankcase in order to remain below the explosion limit.

[0026] By venting the crankcase, the excessive hydrogen content in the crankcase can be reduced and thus the risk of ignition of the hydrogen in the crankcase can be at least partially reduced.

[0027] In yet another preferred embodiment, the method according to the invention further comprises determining the temperature of the gas mixture in the crankcase. The predetermined second hydrogen content threshold is predetermined as a function of the determined temperature of the gas mixture in the crankcase.

[0028] According to a further aspect of the present invention, a hydrogen internal combustion engine is disclosed which is designed to be operated with hydrogen as fuel.The hydrogen internal combustion engine according to the invention has at least one combustion chamber which is formed by a piston which reciprocally moves back and forth within a cylinder, a crankcase in which the piston is at least partially arranged and which is at least partially fluidically connected to the combustion chamber via a gap between the piston and the cylinder, an exhaust tract which is fluidically connected to the at least one combustion chamber, an oxygen sensor arranged in the exhaust tract which is designed to generate an oxygen signal which is representative of the oxygen content in the exhaust gas of the hydrogen internal combustion engine, and a control unit which is designed to carry out a method according to the invention for determining the hydrogen content in the exhaust gas of the hydrogen internal combustion engine.

[0029] Preferably, the hydrogen internal combustion engine according to the invention further comprises an intake pipe which is fluidly connected to the at least one combustion chamber and is designed to supply air to the at least one combustion chamber for the combustion of an air-hydrogen mixture, and a vent line which fluidly connects the crankcase to the intake pipe.

[0030] Further features and objects of the invention will become apparent to those skilled in the art by practicing the present teachings and viewing the accompanying drawings in which: Fig. 1 shows a schematic view of a hydrogen internal combustion engine of a vehicle, and Fig. 2 an exemplary flow diagram of a method according to the invention for determining the hydrogen content in the exhaust gas of the hydrogen internal combustion engine of Fig. 1 and for monitoring the ventilation of the crankcase of the hydrogen internal combustion engine of the Fig. 1 shows.

[0031] In the context of this disclosure, the term "hydrogen internal combustion engine" describes an internal combustion engine that uses hydrogen as fuel. A hydrogen internal combustion engine converts chemical energy into mechanical work and heat. It is based on the oxyhydrogen reaction (combustion of hydrogen) in a reciprocating piston or rotary piston internal combustion engine. Reciprocating piston engines that operate according to the Otto principle (= spark ignition) are usually used. However, according to the invention, this also includes hydrogen internal combustion engines that operate according to the diesel principle (= compression ignition).

[0032] The Fig. Figure 1 shows a schematic view of a hydrogen internal combustion engine 100 of a vehicle. The hydrogen internal combustion engine 100 has an intake pipe (or air intake line) 102 and combustion chambers 110 connected thereto (in the Fig. 1 (only one of the four combustion chambers 110 is provided with a reference numeral). Intake air can enter the combustion chambers 110 via the intake pipe 102, where the intake air can be mixed with hydrogen as fuel and combusted in a known manner. The flow direction of the intake air is indicated by arrow 104.

[0033] The combustion chambers 110 are formed, in particular, by cylinders 112 and pistons 114 reciprocating therein, whereby the volume of the combustion chambers 110 varies over time. The pistons 114 are at least partially arranged in a crankcase 120 and mechanically coupled to a crankshaft 122 arranged therein, which is known from the prior art.

[0034] The combustion chambers 110 are fluidly connected to an exhaust tract 130, through which the exhaust gases generated by the combustion of the air-hydrogen mixture in the combustion chambers 110 can be discharged into the environment. The exhaust tract 130 describes only the section of the hydrogen internal combustion engine 100 that is designed exclusively for discharging the exhaust gases.

[0035] Arranged in the exhaust tract 130 is an oxygen sensor 140 which is designed to generate an oxygen signal that is representative of the oxygen content in the exhaust gas at the position downstream of the combustion chambers 110. The oxygen sensor 140 can be a binary lambda sensor, a linear lambda sensor, a nitrogen oxide sensor and any other sensor whose signal can be evaluated to determine the oxygen content.

[0036] The oxygen sensor 140 cannot detect the hydrogen content directly. Rather, the oxygen content measured by the oxygen sensor 140 is influenced by the prevailing hydrogen content, since the hydrogen present acts as a rich gas and reacts with the oxygen present in the exhaust gas to form water at the electrodes and catalytic surfaces of the oxygen sensor 140. Consequently, the oxygen content determined by the oxygen sensor 140 is lower than the actual oxygen content in the exhaust gas. The difference between the actual oxygen content, which can be assumed to be known in the predetermined operating mode, and the oxygen content determined by the oxygen sensor 140 can then be correlated with the hydrogen content in the exhaust gas. To determine the oxygen content difference, it is necessary that the actual oxygen content in the exhaust gas during the predetermined operating mode is known.This is the case, for example, during overrun fuel cut-off phases of the hydrogen internal combustion engine 100, since no fuel is metered during these overrun fuel cut-off phases; instead, only the intake air is forced through the combustion chambers 110 and the exhaust tract 130. Under these conditions, a hydrogen content of approximately 20.9% can be assumed, which corresponds to the oxygen content in the air. The determined oxygen content difference can be correlated with the hydrogen content.

[0037] Furthermore, a control unit 160 is provided, which is in communication with the oxygen sensor 140 and is designed to receive the oxygen signal generated by the oxygen sensor 140 and to at least partially control the operation of the hydrogen internal combustion engine 100.

[0038] During operation of the hydrogen internal combustion engine 100, deviations from atmospheric pressure occur not only in the combustion chambers 110, but also below the pistons 114. These are caused, on the one hand, by the volume changes caused by the rotating pistons 114 and, on the other hand, by the exhaust gases from the working process accumulating in the crankcase 120. In particular, exhaust gases from the combustion chambers 110 can enter the crankcase 120 through a gap between the cylinder 112 and the piston 114, which in the Fig. 1 is indicated by an arrow 106.

[0039] In order to prevent these so-called blow-by gases from being expelled unhindered into the atmosphere, a vent line 124 is provided, which fluidically connects the crankcase 120 to the intake manifold 102. A control valve 126 is provided in the vent line 124, with which an active venting of the crankcase 120 into the intake manifold 102 can be controlled. The control valve 126 is preferably a pressure control valve, which can automatically control or regulate the pressure within the crankcase 120. Additionally or alternatively, the pressure in the crankcase 120 can be controlled with the aid of a mechanical regulating valve (in the Fig. 1 not shown) in the intake manifold 102. In particular, the exhaust gases collected in the crankcase 120 can be fed to the combustion chambers 110 and thus also to the exhaust tract 130 for later working cycles, where they can then be released into the environment in a controlled manner.

[0040] The hydrogen internal combustion engine 100 has, in the Fig. 1, the exemplary embodiment also includes a ventilation line 128 that fluidically connects the crankcase 120 to the intake pipe 102. A ventilation pump 129 is provided in the ventilation line 128, with which active ventilation of the crankcase 120 from the intake pipe 102 can be controlled. The ventilation pump 129 is particularly designed to pump air from the intake pipe 102 into the crankcase 120 when it is determined that the hydrogen content within the crankcase 120 exceeds a predetermined hydrogen content threshold value and thus there is an increased risk of explosion. By blowing air into the crankcase 120, the hydrogen content therein can be reduced, thus also reducing the risk of explosion.

[0041] According to the Fig. In the embodiment shown in Figure 1, the blowby gases are introduced into the intake manifold 102 via the vent line 124. Due to the negative pressure in the intake manifold 102, a negative pressure is also created in the crankcase 120 in most operating states of the internal combustion engine 100.

[0042] With additional reference to the Fig. 2, an exemplary embodiment of a method according to the invention for determining the hydrogen content in the exhaust gas of the hydrogen internal combustion engine 100 and for monitoring the functionality of the crankcase ventilation of the hydrogen internal combustion engine 100 of the Fig. 1 described as an example.

[0043] The procedure of Fig. 2 starts at step 200 and then proceeds to step 210, where it is determined whether the hydrogen internal combustion engine 100 is in a predetermined operating mode during which no combustion of an air-hydrogen mixture takes place within the combustion chambers 110. For example, a predetermined operating mode may be in the form of an overrun fuel cut-off phase of the hydrogen internal combustion engine 100. The method remains at step 210 until a predetermined operating mode is determined.

[0044] If a predetermined operating mode of the hydrogen internal combustion engine 100 is determined in step 210, the method proceeds to step 220, at which the control device 160 receives an oxygen signal from the oxygen sensor 140.

[0045] In a subsequent step 230, the oxygen content in the exhaust gas of the hydrogen internal combustion engine 100 is determined based on the oxygen signal received from the oxygen sensor 140 in step 220. At the same time or in a separate step (in the Fig. 2 (not explicitly shown), the actual oxygen content in the exhaust gas of the hydrogen internal combustion engine 100 is determined based on the determined predetermined operating mode. For example, the actual oxygen content in the exhaust gas of the hydrogen internal combustion engine 100 in an overrun fuel cut-off phase is approximately 20.9%, which corresponds to the proportion of oxygen in the air.

[0046] In a subsequent step 240, an oxygen content difference is formed between the determined actual oxygen content and the oxygen content determined in step 240 based on the oxygen signal received from the oxygen sensor 140. In a subsequent step 250, the hydrogen content in the exhaust gas of the hydrogen internal combustion engine 100 is determined at least partially based on the oxygen content difference determined in step 240. In particular, the hydrogen content in the exhaust gas can be determined based on a correlation between hydrogen and oxygen using the determined oxygen content difference. Alternatively, step 230 can be omitted, so that the hydrogen content in the exhaust gas of the hydrogen internal combustion engine 100 is determined directly from the oxygen signal received from the oxygen sensor 140 in step 220.

[0047] It should be noted again that the oxygen content in the exhaust gas detected by the oxygen sensor 140 does not correspond to the actual oxygen content in the exhaust gas, since the hydrogen present in the exhaust gas reacts with the oxygen present in the exhaust gas to form water at the electrodes and catalytic surfaces of the oxygen sensor 140. Thus, the oxygen content indicated by the oxygen sensor is lower than the actual oxygen content, since the hydrogen present in the exhaust gas reacts with a corresponding proportion of oxygen in the exhaust gas.

[0048] In step 250, a hydrogen signal may also be sent that is representative of the hydrogen content in the exhaust gas of the hydrogen internal combustion engine.

[0049] In a subsequent step 260, it is determined whether the hydrogen content determined in step 250 exceeds a predetermined hydrogen content threshold, such as 0.5%. Preferably, after determining the predetermined operating mode of the internal combustion engine 100, a predetermined period of approximately 3 seconds, preferably approximately 1 second, can be waited until steps 220 to 250 are carried out. This ensures that at the time the oxygen content is measured by means of the oxygen sensor 140, the exhaust gases generated due to the combustion that previously took place in the combustion chambers 110 have already flowed past the oxygen sensor 140. Consequently, the exhaust gas measured in step 220 should be the exhaust gas vented from the crankcase 120 and the fresh air from the intake manifold 102.

[0050] If it is determined in step 260 that the hydrogen content determined in step 250 exceeds a predetermined first hydrogen content threshold, the method proceeds to step 270, where a properly functioning crankcase ventilation system is diagnosed. In particular, exceeding the predetermined first hydrogen content threshold can be interpreted as meaning that the exhaust gases trapped in the crankcase 120 are vented either via the vent line 124 and / or past the pistons 114 (i.e., along the arrow 108 in the Fig. 1) into the combustion chambers 110 and thus into the exhaust tract 130. Thus, these two venting paths are essentially unblocked and essentially free.

[0051] However, if it is determined in step 260 that the hydrogen content determined in step 250 does not exceed, i.e., falls below, the predetermined first hydrogen content threshold, the method proceeds to step 280, where an improperly functioning or malfunctioning crankcase ventilation is diagnosed. In particular, falling below the predetermined first hydrogen content threshold can be interpreted to mean that the exhaust gases trapped in the crankcase 120 cannot be vented as desired via the ventilation line 124 and / or past the pistons 114 (i.e., along the arrow 108 in the Fig. 1) can flow into the combustion chambers 110 and thus into the exhaust tract 130. Thus, at least one of these two ventilation paths is at least partially blocked or clogged, for example, by foreign particles, a crushed line, or a clogged intake air filter. Simultaneously with step 280 or subsequently, a warning signal can be sent indicating the detected crankcase ventilation malfunction.

[0052] Alternatively, in step 260, the oxygen signal received in step 220 can be directly evaluated to diagnose the crankcase ventilation system. In such an alternative embodiment, fault-free crankcase ventilation is present if the oxygen content in the exhaust gas determined by means of the oxygen sensor 140 falls below a predetermined first oxygen content threshold (analogous to steps 260 and 270). Furthermore, a malfunctioning crankcase ventilation system can be diagnosed if the oxygen content in the exhaust gas determined by means of the oxygen sensor 140 exceeds the predetermined first oxygen content threshold (analogous to steps 260 and 280).

[0053] In the in the Fig. In an advantageous and exemplary embodiment according to FIG. 2, steps 270 and 280 are each followed by a step 290 in which the exhaust gas mass flow is determined. This can be done, for example, by means of an air mass meter arranged in the intake manifold 102 or via an air path model calculated in the engine control system.

[0054] In a subsequent step 292, the hydrogen content present in the crankcase 120 is determined based on the hydrogen content in the exhaust gas determined in step 250 and the exhaust gas mass flow determined in step 290. In particular, the hydrogen content in the crankcase 120 can be determined by correlating the hydrogen content in the exhaust gas determined in step 250 and the exhaust gas mass flow determined in step 290.

[0055] In a subsequent step 294, a check is performed to determine whether the hydrogen content in the crankcase 120 determined in step 292 exceeds a predetermined second hydrogen content threshold value. If it is determined in step 294 that the hydrogen content in the crankcase 120 determined in step 292 exceeds the predetermined second hydrogen content threshold value, such as 3%, the method proceeds to step 296, at which an increased risk of explosion is determined. In step 296, a warning signal can be output to the operator of the hydrogen internal combustion engine 100, alerting the operator that there is an increased risk of explosion. At the same time or subsequently, active venting of the crankcase 120 can take place as a countermeasure.

[0056] If it is determined in step 294 that the hydrogen content in the crankcase 120 determined in step 292 does not exceed the predetermined second hydrogen content threshold, such as 3%, the method proceeds to step 298, at which no increased risk of explosion is determined.

[0057] After steps 296 and 298, the procedure of Fig. 2 at step 300.

Claims

[1] Method for determining the hydrogen content in an exhaust tract (130) of a hydrogen internal combustion engine (100) having combustion chambers (110) and an oxygen sensor (140) arranged in the exhaust tract (130) of the hydrogen internal combustion engine (100), which oxygen sensor is designed to generate an oxygen signal that is representative of the oxygen content in the exhaust gas of the hydrogen internal combustion engine (100), the method comprising: - determining a predetermined operating mode of the hydrogen internal combustion engine (100) during which substantially no combustion of an air-hydrogen mixture takes place within the combustion chambers (110), - receiving an oxygen signal from the oxygen sensor (140) during the predetermined operating mode of the internal combustion engine (100), and - Determining the hydrogen content in the exhaust gas of the hydrogen internal combustion engine (100) based at least partially on the oxygen signal received from the oxygen sensor (140). [2] The method of claim 1, further comprising: - determining the oxygen content in the exhaust gas of the hydrogen internal combustion engine (100) based on the oxygen signal received from the oxygen sensor (140), wherein the determination of the hydrogen content in the exhaust gas of the hydrogen internal combustion engine (100) is based at least partially on the determined oxygen content. [3] The method of claim 2, further comprising: - determining the actual oxygen content in the exhaust gas of the hydrogen internal combustion engine (100) based on the determined predetermined operating mode of the hydrogen internal combustion engine (100), and - forming an oxygen content difference between the determined actual oxygen content and the oxygen content determined based on the oxygen signal received from the oxygen sensor (140), wherein the determination of the hydrogen content in the exhaust gas of the hydrogen internal combustion engine (100) is based at least partially on the determined oxygen content difference. [4] Method according to one of the preceding claims, wherein the receiving of the oxygen signal occurs after a predetermined period of time has elapsed after the predetermined operating mode of the hydrogen internal combustion engine (100) has been determined. [5] The method of claim 4, wherein the predetermined time period is approximately 3 seconds, preferably approximately 1 second. [6] Method according to one of the preceding claims, wherein the predetermined operating mode of the hydrogen internal combustion engine (100) comprises an overrun fuel cut-off phase of the hydrogen internal combustion engine (100). [7] Method according to one of the preceding claims, further comprising: - Determining a functional ventilation of the crankcase (120) when the hydrogen content in the exhaust gas of the hydrogen internal combustion engine (100) determined during the predetermined operating mode of the hydrogen internal combustion engine (100) exceeds a predetermined first hydrogen content threshold value. [8] Method according to one of the preceding claims, further comprising: - Determining a malfunctioning ventilation of the crankcase (120) if the hydrogen content in the exhaust gas of the hydrogen internal combustion engine (100) determined during the predetermined operating mode of the hydrogen internal combustion engine (100) falls below a predetermined first hydrogen content threshold value. [9] The method of claim 8, further comprising: - issuing a warning to the operator of the hydrogen internal combustion engine (100) if a malfunctioning crankcase ventilation (120) has been detected. [10] A method according to any one of claims 7 to 9, wherein the predetermined first hydrogen content threshold is between about 0.3% and about 0.6%, preferably about 0.5%. [11] Method according to one of the preceding claims, further comprising: - determining an exhaust gas mass flow through the exhaust tract (130) of the hydrogen internal combustion engine (100), and - Determining the hydrogen content in the crankcase (120) of the hydrogen internal combustion engine (100) at least partially based on the determined hydrogen content in the exhaust gas of the hydrogen internal combustion engine (100) and at least partially based on the determined exhaust gas mass flow through the exhaust tract (130) of the hydrogen internal combustion engine (100). [12] The method of claim 11, further comprising: - determining that the hydrogen content in the crankcase (120) of the hydrogen internal combustion engine (100) exceeds a predetermined second hydrogen content threshold, and - at least partially venting the crankcase (120) if it has been determined that the hydrogen content in the crankcase (120) of the hydrogen internal combustion engine (100) exceeds the predetermined second hydrogen content threshold value. [13] The method of claim 12, further comprising: - determining the temperature of the gas mixture in the crankcase (120), wherein the predetermined second hydrogen content threshold value is predetermined as a function of the determined temperature of the gas mixture in the crankcase (120). [14] Hydrogen internal combustion engine (100) designed to be operated with hydrogen as fuel, comprising: - at least one combustion chamber (110) formed by a piston (114) reciprocating reciprocally within a cylinder (112), - a crankcase (120) in which the piston (114) is at least partially arranged and which is at least partially fluidly connected to the combustion chamber (110) via a gap between the piston (114) and the cylinder (112), - an exhaust tract (130) which is fluidly connected to the at least one combustion chamber (110), - an oxygen sensor (140) arranged in the exhaust tract (130) which is designed to generate an oxygen signal which is representative of the oxygen content in the exhaust gas of the hydrogen internal combustion engine (100), and - a control unit (160) which is designed to carry out a method according to one of the preceding claims for determining the hydrogen content in the exhaust gas of the hydrogen internal combustion engine (100). [15] Hydrogen internal combustion engine (100) according to claim 14, further comprising: - an intake pipe (102) fluidly connected to the at least one combustion chamber (110) and configured to supply air to the at least one combustion chamber (110) for the combustion of an air-hydrogen mixture, and - a vent line (124) which fluidly connects the crankcase (120) to the intake pipe (102).

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