Method, control device and computer program for determining the hydrogen content in the exhaust gas of a hydrogen combustion engine, as well as exhaust system, hydrogen combustion engine, vehicle and computer-readable medium

Abstract

Method for determining the hydrogen content in the exhaust gas of a hydrogen combustion engine at a position upstream of an oxidation catalyst device (110) configured to oxidize the hydrogen in the exhaust gas, wherein upstream of the oxidation catalyst device (110) a first exhaust gas sensor (120) is arranged, which is configured to generate a first exhaust gas signal that is representative of the oxygen content in the exhaust gas that has diffused into the first exhaust gas sensor (120) at the measuring position, which originates from the exhaust gas upstream of the oxidation catalyst device (110), and downstream of the oxidation catalyst device (110) a second exhaust gas sensor (130) is arranged, which is configured to generate a second exhaust gas signal that is representative of the oxygen content in the exhaust gas that has diffused into the second exhaust gas sensor (130) at the measuring position, which originates from the exhaust gas.originates downstream of the oxidation catalyst device (110), the method comprising: - Determining a deceleration shutdown phase of the hydrogen combustion engine, - Receiving a first exhaust signal from the first exhaust sensor (120), - Receiving a second exhaust signal from the second exhaust sensor (130), - Determining a difference at least partially based on the received first exhaust signal and the received second exhaust signal, - Determining the hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device (110) at least partially based on the determined difference, wherein the determined hydrogen content provides an indication of the crankcase ventilation of the hydrogen combustion engine, and - Sending a hydrogen signal that is representative of the determined hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device (110).

Description

The present invention relates to a method, a control device and a computer program for determining the hydrogen content in the exhaust gas of a hydrogen combustion engine, as well as an exhaust system, a hydrogen combustion engine, a vehicle and a computer-readable medium. In hydrogen combustion engines, catalysts, such as oxidation catalysts, are used for exhaust aftertreatment to reduce hydrogen emissions by converting them to water (H₂O). This process occurs in an oxidation catalyst particularly when it reaches an operating temperature of approximately 250 °C. At this temperature, the so-called "light-off" temperature is reached. In practice, however, it has been shown that the actual operating temperature, or "light-off" temperature, is not a fixed temperature threshold, but rather depends on certain operating and boundary conditions, such as the coating of the catalyst device, the exhaust gas mass flow rate, the aging state of the catalyst device, and / or the degree of catalyst poisoning. Consequently, even at catalyst device temperatures higher than the predetermined operating temperature, which is, for example, approximately 250 °C, incomplete conversion of the carbon compounds may still occur. On the other hand, the catalyst device may already reach its "light-off" temperature at a temperature lower than the predetermined operating temperature, so that further external heating of the catalyst device is no longer necessary. DE 10 2021 203 282 A1 relates to a method for operating an oxidation catalyst device arranged in the exhaust system of an internal combustion engine, which is designed to oxidize the carbon compounds present in the exhaust gas, and to an exhaust system. An exhaust gas sensor is also arranged downstream of the oxidation catalyst device, which is designed to detect the carbon content in the exhaust gas. The method according to the invention comprises determining the carbon content in the exhaust gas by means of the exhaust gas sensor and heating the oxidation catalyst device when the determined carbon content in the exhaust gas exceeds a predetermined carbon threshold value. DE 43 41 632 A1 discloses a method for testing and controlling motor vehicles using a known method for determining the air factor lambda from the oxygen partial pressure of the exhaust gas brought almost to total chemical equilibrium, given knowledge of the average fuel composition. In addition to the oxygen partial pressure of the exhaust gas brought almost to chemical equilibrium, the oxygen partial pressure in exhaust gas that has not been exposed to any means of achieving total gas equilibrium is measured. Lambda is then calculated from the two oxygen partial pressures, the difference between the lambda values ​​is determined, and this difference is used as a measure of the concentration of the sum of the hydrocarbon residues in the exhaust gas. Further state of the art includes FR 3 139 600 A1 , DE 10 2020 209 159 B4 , FR 2 950 386 B1 , US 2008 / 0 041 034 A1 , DE 10 2005 044 335 A1 , EP 3 158 174 B1 , FR 2 950 386 B1 and US 8 161 729 B2 . The present invention is essentially based on the objective of providing a method and a control device with which the hydrogen content in the exhaust gas of the hydrogen combustion engine can be determined in a simple and reliable manner at a position upstream of an oxidation catalyst device. Based on the determined hydrogen content, the operating parameters of the hydrogen combustion engine can then be adjusted for efficient and emission-reduced operation. This problem is solved by a method according to claim 1, a control device according to claim 8, an exhaust system according to claim 10, a hydrogen combustion engine according to claim 12, a vehicle according to claim 13, a computer program according to claim 14, and a computer-readable medium according to claim 15. Advantageous embodiments are specified in the dependent claims. The present invention is essentially based on the idea of ​​a method for determining the hydrogen content in the exhaust gas of a hydrogen combustion engine at a position upstream of an oxidation catalyst device, and thus obtaining an indication of the crankcase ventilation, by determining the difference between the oxygen content upstream and downstream of the oxidation catalyst device using exhaust gas sensors arranged in such a way as to be sensitive to hydrogen, and then inferring the hydrogen content in the exhaust gas of the hydrogen combustion engine based on this difference. The present invention takes advantage of the fact that there is a correlation between the determined difference upstream of the oxidation catalyst device and the corresponding hydrogen content. Consequently, according to a first aspect of the present invention, a method for determining the hydrogen content in the exhaust gas of a hydrogen internal combustion engine is disclosed at a position upstream of an oxidation catalyst device designed to oxidize the hydrogen present in the exhaust gas.In this arrangement, a first exhaust gas sensor is arranged upstream of the oxidation catalyst device, which is configured to generate a first exhaust gas signal that is representative of the oxygen content in the exhaust gas that has diffused into the first exhaust gas sensor at the measuring position and that originates from the exhaust gas upstream of the oxidation catalyst device, and a second exhaust gas sensor is arranged downstream of the oxidation catalyst device, which is configured to generate a second exhaust gas signal that is representative of the oxygen content in the exhaust gas that has diffused into the second exhaust gas sensor at the measuring position and that originates from the exhaust gas downstream of the oxidation catalyst device.The method according to the invention comprises determining a deceleration cut-off phase of the hydrogen combustion engine, receiving a first exhaust gas signal from the first exhaust gas sensor, receiving a second exhaust gas signal from the second exhaust gas sensor, determining a difference at least partially based on the received first exhaust gas signal and the received second exhaust gas signal, determining the hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device at least partially based on the determined difference, wherein the determined hydrogen content provides an indication of the crankcase ventilation of the hydrogen combustion engine, and sending a hydrogen signal that is representative of the determined hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device. Using the method according to the invention, the hydrogen content upstream of the oxidation catalyst device in the exhaust gas of the hydrogen combustion engine can therefore be determined simply and reliably and used for adjusting the operating parameters of the hydrogen combustion engine and providing information about the crankcase ventilation. The present invention utilizes the cross-sensitivity of the exhaust gas sensor to the hydrogen present in the exhaust gas by ensuring that the hydrogen present in the exhaust gas is at least partially oxidized as it diffuses into the exhaust gas sensor up to the measuring position within the sensor. In particular, chemical reactions, such as the oxidation of hydrogen present in the exhaust gas, already take place along this diffusion path from the exhaust gas tract to the measuring position within the exhaust gas sensor.This influence of changes in exhaust gas composition, particularly oxygen content, as the exhaust gas diffuses into the exhaust gas sensor can be described as the cross-sensitivity of the exhaust gas sensor to the hydrogen contained in the exhaust gas. Thus, upstream of the oxidation catalyst device, where the first exhaust gas sensor is also located, the composition of the exhaust gas at the measuring position of the first exhaust gas sensor can differ from the composition of the exhaust gas in the exhaust tract upstream of the oxidation catalyst device. Before the minimum operating temperature or light-off temperature of the oxidation catalyst device is reached, this also applies to the exhaust gas downstream of the oxidation catalyst device, which diffuses into the second exhaust gas sensor and can change its composition during this diffusion due to the oxidation of the hydrogen contained in the exhaust gas. After reaching the minimum operating temperature or light-off temperature,However, at the light-off temperature of the oxidation catalyst device, the hydrogen is essentially completely oxidized, so that the composition of the exhaust gas at the measuring position of the second exhaust gas sensor is essentially the same as the composition of the exhaust gas in the exhaust tract downstream of the oxidation catalyst device. The present invention thus takes advantage of the fact that the hydrogen content upstream of the oxidation catalyst device can be determined by calculating the difference between the received first exhaust gas signal and the received second exhaust gas signal. This difference can be calculated using the oxygen content determined from the respective exhaust gas signals or directly using the two respective exhaust gas signals themselves. In a preferred embodiment, the method according to the invention further comprises receiving a temperature signal representative of the temperature of the oxidation catalyst device and determining whether the received temperature signal indicates a temperature of the oxidation catalyst device that is greater than a predetermined temperature threshold. The determination of the hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device, at least partially based on the determined difference, only takes place after it has been determined that the received temperature signal indicates a temperature of the oxidation catalyst device that is greater than the predetermined temperature threshold. It is particularly preferred if the predetermined temperature threshold indicates the minimum operating temperature or light-off temperature of the oxidation catalyst device. This means that the process according to the invention is preferably only carried out when the oxidation catalyst device has reached its operating temperature and is thus within its optimal operating range. Preferably, the predetermined temperature threshold is approximately 250 °C. According to a further advantageous embodiment of the method according to the invention, determining the hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device involves at least partially assigning the determined difference to a corresponding hydrogen content value. It is particularly preferred that the assignment of the determined difference to the corresponding hydrogen content value is carried out by means of an assignment table and / or an assignment formula and / or an assignment diagram. According to a further advantageous embodiment, the method according to the invention further comprises determining that the determined difference exceeds a predetermined difference threshold and ascertaining that the oxidation catalyst device has reached its minimum operating temperature or light-off temperature when it has been determined that the determined difference exceeds a predetermined difference threshold. In this preferred embodiment, the present invention takes advantage of the fact that the oxidation catalyst device can be assumed to have reached its minimum operating temperature or light-off temperature when the measured difference exceeds the predetermined difference threshold. Only then can it be stated that the conversion of oxygen or the oxidation of hydrogen in the oxidation catalyst device is proceeding as desired, which is only possible when the minimum operating temperature or light-off temperature of the oxidation catalyst device is reached. Thus, the measured difference then exceeds the predetermined difference threshold. It should be noted that the presence of hydrogen is a prerequisite for this. The presence of hydrogen can be, for example,This can be achieved through model calculations using the operating parameters of the hydrogen combustion engine, for example by deliberately inducing hydrogen slip through the hydrogen combustion engine. According to a further aspect of the present invention, a control device is disclosed which is configured to perform the steps of a method according to the invention. According to a preferred embodiment, the control device according to the invention comprises a first control device section for performing the step of receiving a first exhaust gas signal from the first exhaust gas sensor, a second control device section for performing the step of receiving a second exhaust gas signal from the second exhaust gas sensor, a third control device section for performing the step of determining a difference at least partially based on the received first exhaust gas signal and the received second exhaust gas signal, a fourth control device section for performing the step of determining the hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device at least partially based on the determined difference, and a fifth control device section for performing the step of sending a hydrogen signal.This is representative of the determined hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device. According to a further aspect of the present invention, an exhaust system for a hydrogen combustion engine is disclosed, comprising an oxidation catalyst device configured to oxidize the hydrogen contained in the exhaust gas, a first exhaust gas sensor arranged upstream of the oxidation catalyst device, configured to generate a first exhaust gas signal representative of the oxygen content in the exhaust gas diffused into the first exhaust gas sensor at the measuring position, which originates from the exhaust gas upstream of the oxidation catalyst device, and a second exhaust gas sensor arranged downstream of the oxidation catalyst device, configured to generate a second exhaust gas signal representative of the oxygen content in the exhaust gas diffused into the second exhaust gas sensor at the measuring position, which originates from the exhaust gas downstream of the oxidation catalyst device.and includes a control device according to the invention:, In a preferred embodiment of the exhaust system according to the invention, the first exhaust gas sensor and / or the second exhaust gas sensor is an oxygen sensor, a nitrogen oxide sensor, a binary lambda probe, a linear lambda probe or any other sensor that is sensitive to oxygen and cross-sensitive to hydrogen. According to a further aspect of the present invention, a hydrogen combustion engine with an exhaust system according to the invention is disclosed. According to yet another aspect, a vehicle with a hydrogen combustion engine according to the invention is disclosed. According to a further aspect of the present invention, a computer program is disclosed comprising instructions which, when executed by a computing unit, cause the computing unit to execute a method according to the invention for determining the hydrogen content in the exhaust gas of a hydrogen combustion engine. According to a further aspect of the present invention, a computer-readable medium is disclosed on which the computer program according to the invention is stored. Further tasks and features of the present invention will become apparent to the person skilled in the art by applying the present teaching and considering the accompanying drawings, in which: Fig. 1 shows a schematic view of an exhaust tract of a hydrogen combustion engine according to the invention, and Fig. 2 shows an exemplary flow diagram of a method according to the invention for determining the hydrogen content in the exhaust gas flowing through the exhaust tract of Fig. 1 upstream of an oxidation catalyst device arranged therein. Within the scope of this disclosure, the term "cross-sensitivity" describes a property of an exhaust gas sensor such that the generated exhaust gas signal can be at least partially distorted by any hydrogen present. This means that the exhaust gas signal from the sensor is only representative of the composition of the exhaust gas at the measurement point within the sensor, but not necessarily of the composition of the exhaust gas in the exhaust system of the hydrogen combustion engine before it enters the sensor. This is primarily due to the fact that chemical reactions, such as the oxidation of hydrogen present in the exhaust gas, can occur along the diffusion path of the exhaust gas from the exhaust system to the measurement point within the sensor, so that the exhaust gas composition at the measurement point can differ from that in the exhaust system. Fig. 1 shows a schematic view of an exhaust system 100 according to the invention for a hydrogen combustion engine (not explicitly shown). In particular, the exhaust gas from the hydrogen combustion engine enters the exhaust system 100 via arrow 102. The exhaust system 100 has an oxidation catalyst device 110 and an optional catalyst device 140 with selective catalytic reduction arranged downstream of it. For example, the optional catalyst device 140 can be a purely selective catalytic reduction device (“selective catalytic reduction” SCR) or a particulate filter with a selective catalytic reduction coating. The oxidation catalyst device can be an oxidation catalyst in which hydrogen is oxidized. In particular, in the oxidation catalyst device 110, the hydrogen present in the exhaust gas is converted or transformed, for example into water. The exhaust system 100 further comprises a first exhaust gas sensor 120 arranged upstream of the oxidation catalyst device 110 and a second exhaust gas sensor 130 arranged downstream of the oxidation catalyst device 110. Optionally, a further exhaust gas sensor 150 can be arranged downstream of the optional catalyst device 140. The first exhaust gas sensor 120 is configured to generate a first exhaust gas signal that is representative of the oxygen content in the exhaust gas that has diffused into the first exhaust gas sensor 120 at the measuring position within the first exhaust gas sensor 120, which originates from the exhaust gas upstream of the oxidation catalyst device 110, and the second exhaust gas sensor 130 is configured to generate a second exhaust gas signal that is representative of the oxygen content in the exhaust gas that has diffused into the second exhaust gas sensor 130 at the measuring position of the second exhaust gas sensor 130, which originates from the exhaust gas downstream of the oxidation catalyst device 110.In particular, the exhaust gas sensors 120 and 130 could be nitrogen oxide sensors, which, in addition to their primary function of measuring the nitrogen oxide content in the exhaust gas, can also generate the corresponding exhaust gas signal that is cross-sensitive to hydrogen. Furthermore, the two exhaust gas sensors 120 and 130 could be any sensor capable of detecting the oxygen content in the exhaust gas and generating and transmitting a corresponding exhaust gas signal, such as linear or binary lambda sensors. In order for selective catalytic reduction to take place in the catalyst device 140, a reducing agent injection device 142 can be located upstream of the catalyst device 140 and downstream of the exhaust gas sensor 130, via which a reducing agent, such as an aqueous urea solution, can be injected into the exhaust gas. Optionally, an additional exhaust gas sensor 170, such as a nitrogen oxide sensor, can be provided downstream of the catalyst device 140. The exhaust system 100 also has a control device 160, which is connected via suitable connecting lines to the exhaust gas sensors 120, 130, 170 and the reducing agent injection device 142 and is designed to control the exhaust system 100. The control device 160 can have several control device sections, such as a first control device section 161, a second control device section 162, a third control device section 163, a fourth control device section 164 and a fifth control device section 165, which will be discussed in more detail below with reference to Fig. 2. The control device 160 can include a processor or arithmetic unit and memory. Alternatively, the control device 160 can be the processor or arithmetic unit connected to the memory. The processor can be a central processing unit (CPU). The processor can also be another general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or another programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, or the like. The general-purpose processor can be a microprocessor, or the processor can be any conventional processor or the like. The memory includes, but is not limited to, Random Access Memory (RAM), Read-Only Memory (ROM), Erasable Programmable Read-Only Memory (EPROM), or Portable Read-Only Memory (e.g., CD-ROM). The memory is configured to store associated program instructions and data. With additional reference to Fig. 2, which shows an exemplary flowchart of a method according to the invention for determining the hydrogen content in the exhaust gas of the exhaust tract 100 of Fig. 1, a method according to the invention is explained below. The process of Fig. 2 starts at step 200 and then proceeds to step 210, in which the control device 160 detects a deceleration shutdown phase of the hydrogen combustion engine and, in particular, the first control device section 161 receives a first exhaust gas signal from the first exhaust gas sensor 120. The first exhaust gas signal can, for example, indicate the oxygen content in the exhaust gas at the measuring position of the first exhaust gas sensor 120 and is cross-sensitive to the hydrogen present in the exhaust gas. Alternatively, the first exhaust gas signal can be a linear or binary lambda signal, which in each case indicates the lambda value of the exhaust gas at the measuring position of the first exhaust gas sensor 120. The lambda signal is therefore also representative (directly or indirectly) of the oxygen content in the exhaust gas at the measuring position of the first exhaust gas sensor 120. In a subsequent step 220, which preferably follows the first step 210 in time, the control device 160, in particular the second control device section 162, receives a second exhaust gas signal from the second exhaust gas sensor 130. The time difference between the reception of the first and second exhaust gas signals can be selected such that the substantially same exhaust gas, which has meanwhile passed through the oxidation catalyst device, is measured at the position of the first exhaust gas sensor 120 and at the position of the second exhaust gas sensor 130. For example, it may be preferred to take the flow velocity or the exhaust gas mass flow rate into account. The second exhaust gas signal can, for example, indicate the oxygen content in the exhaust gas at the measuring position of the second exhaust gas sensor 130 and is cross-sensitive to the hydrogen present in the exhaust gas.Alternatively, the second exhaust gas signal can be a linear or binary lambda signal, which in each case indicates the lambda value of the exhaust gas at the measuring position of the second exhaust gas sensor 130. The lambda signal is therefore also representative (directly or indirectly) of the oxygen content in the exhaust gas at the measuring position of the second exhaust gas sensor 130. In a subsequent step 230, a difference is determined using the control device 160, in particular using the third control device section 163. Specifically, the difference is determined at least partially based on the first exhaust gas signal received in step 210 and the second exhaust gas signal received in step 220. The determined difference can, for example, be an oxygen content difference or a lambda difference. In a subsequent step 240, the hydrogen content in the exhaust gas of the hydrogen combustion engine is determined by means of the control device 160, in particular by means of the fourth control device section 164. The determination of the hydrogen content is based at least partially on the difference determined in step 230. The determined difference can be assigned to a corresponding hydrogen content, for example by means of an assignment table and / or an assignment formula and / or an assignment diagram. In a subsequent step 250, a hydrogen signal is sent that is representative of the determined hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device 110, before the process ends at step 260. Although not shown, a query may precede step 210 to verify whether the oxidation catalyst device 110 is operating within its optimal temperature range. In particular, it is preferred that the method according to the invention, especially steps 210 to 250, is only carried out after it has been determined that the oxidation catalyst device 110 is operating within its optimal temperature range. This can be done, for example, by means of a temperature sensor provided in the oxidation catalyst device 110, which is configured to generate a temperature signal that is representative of the temperature of the oxidation catalyst device 110. Alternatively, the temperature of the oxidation catalyst device 110 can be estimated or determined using a temperature model. Steps 210 to 250 are only carried out once the measured temperature of the oxidation catalyst device 110 is above the minimum operating temperature or predetermined light-off temperature. This is because only when the oxidation catalyst device 110 has reached its minimum operating temperature or predetermined light-off temperature can it be assumed that the exhaust gas downstream of it is essentially free of hydrogen, and thus the exhaust gas measured by the second exhaust gas sensor 130 is essentially the same as the exhaust gas in the exhaust tract downstream of the oxidation catalyst device 110. Accordingly, the cross-sensitivity of the second exhaust gas sensor 130 to hydrogen then has essentially no further effect. Instead of using a temperature sensor, the determination that the oxidation catalyst device 110 is operating within its optimal temperature range, for example, above approximately 250 °C, can be made using the difference determined in step 230. In particular, step 230 can be followed by a query to check whether the determined difference exceeds a predetermined threshold. If the difference is found to be below this threshold, it can be determined that the hydrogen oxidation in the oxidation catalyst device 110 is not yet sufficiently advanced and, consequently, its operating temperature has not yet been reached.However, if the difference determined in step 230 exceeds the predetermined difference threshold, it can be assumed that a sufficiently high oxidation of the hydrogen takes place within the oxidation catalyst device, and consequently the oxidation catalyst device 110 is in its temperature-optimal operating range. The monitoring of the temperature and / or the determined difference can be carried out continuously, and thus the heating or warming of the oxidation catalyst device 110 can be controlled as required. According to the invention, during the overrun shutdown phase of the hydrogen combustion engine, the state of the engine is determined by evaluating the hydrogen content. The determined hydrogen content then provides an indication of the crankcase ventilation of the hydrogen combustion engine. If the determined hydrogen content exceeds a predetermined hydrogen content threshold, such as 4%, it can be concluded that there is an excessive accumulation of hydrogen in the crankcase of the hydrogen combustion engine, so that immediate crankcase ventilation may be necessary to reduce the risk of explosion.

Claims

Method for determining the hydrogen content in the exhaust gas of a hydrogen combustion engine at a position upstream of an oxidation catalyst device (110) configured to oxidize the hydrogen in the exhaust gas, wherein upstream of the oxidation catalyst device (110) a first exhaust gas sensor (120) is arranged, which is configured to generate a first exhaust gas signal that is representative of the oxygen content in the exhaust gas that has diffused into the first exhaust gas sensor (120) at the measuring position, which originates from the exhaust gas upstream of the oxidation catalyst device (110), and downstream of the oxidation catalyst device (110) a second exhaust gas sensor (130) is arranged, which is configured to generate a second exhaust gas signal that is representative of the oxygen content in the exhaust gas that has diffused into the second exhaust gas sensor (130) at the measuring position, which originates from the exhaust gas.originates downstream of the oxidation catalyst device (110), the method comprising: - Determining a deceleration shutdown phase of the hydrogen combustion engine, - Receiving a first exhaust signal from the first exhaust sensor (120), - Receiving a second exhaust signal from the second exhaust sensor (130), - Determining a difference at least partially based on the received first exhaust signal and the received second exhaust signal, - Determining the hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device (110) at least partially based on the determined difference, wherein the determined hydrogen content provides an indication of the crankcase ventilation of the hydrogen combustion engine, and - Sending a hydrogen signal that is representative of the determined hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device (110). The method according to claim 1, further comprising: - receiving a temperature signal that is representative of the temperature of the oxidation catalyst device (110), and - determining that the received temperature signal indicates a temperature of the oxidation catalyst device (110) that is greater than a predetermined temperature threshold, wherein the determination of the hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device (110) is carried out at least partially based on the determined difference only after it has been determined that the received temperature signal indicates a temperature of the oxidation catalyst device (110) that is greater than the predetermined temperature threshold. Method according to claim 2, wherein the predetermined temperature threshold indicates the minimum operating temperature or light-off temperature of the oxidation catalyst device (110). Method according to one of claims 2 and 3, wherein the predetermined temperature threshold is approximately 250 °C. Method according to one of the preceding claims, wherein the determination of the hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device (110) at least partially comprises an assignment of the determined difference to a corresponding hydrogen content value. Method according to claim 5, wherein the assignment of the determined difference to the corresponding hydrogen content value is carried out by means of an assignment table and / or an assignment formula and / or an assignment diagram. Method according to one of the preceding claims, further comprising: - determining that the determined difference exceeds a predetermined difference threshold, and - determining that the oxidation catalyst device (110) has reached its minimum operating temperature or light-off temperature when it has been determined that the determined difference exceeds a predetermined difference threshold. Control device (160) configured to perform the steps of the method according to one of the preceding claims. Control device (160) according to claim 8, comprising: - a first control device section (161) for performing the step of receiving a first exhaust gas signal from the first exhaust gas sensor (120), - a second control device section (162) for performing the step of receiving a second exhaust gas signal from the second exhaust gas sensor (130), - a third control device section (163) for performing the step of determining a difference at least partially based on the received first exhaust gas signal and the received second exhaust gas signal, - a fourth control device section (164) for performing the step of determining the hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device (110) at least partially based on the determined difference, and - a fifth control device section (165) for performing the step of sending a hydrogen signal.which is representative of the determined hydrogen content in the exhaust gas of the hydrogen combustion engine upstream of the oxidation catalyst device (110). Exhaust system (100) for a hydrogen combustion engine, comprising: - an oxidation catalyst device (110) configured to oxidize the hydrogen present in the exhaust gas, a first exhaust gas sensor (120) arranged upstream of the oxidation catalyst device (110) configured to generate a first exhaust gas signal representative of the oxygen content in the exhaust gas diffused into the first exhaust gas sensor (120) at the measuring position, which originates from the exhaust gas upstream of the oxidation catalyst device (110), - a second exhaust gas sensor (130) arranged downstream of the oxidation catalyst device (110) configured to generate a second exhaust gas signal representative of the oxygen content in the exhaust gas diffused into the second exhaust gas sensor (130) at the measuring position, which originates from the exhaust gas downstream of the oxidation catalyst device (110),and- a control device (160) according to one of claims 8 and 9., Exhaust system (100) according to claim 10, wherein the first exhaust gas sensor (120) and / or the second exhaust gas sensor (130) is an oxygen sensor, a nitrogen oxide sensor, a linear lambda probe, a binary lambda probe or any other sensor that is sensitive to oxygen and cross-sensitive to hydrogen. Hydrogen internal combustion engine with an exhaust system (100) according to one of claims 10 and 11. Vehicle with a hydrogen combustion engine according to claim 12. Computer program comprising instructions which, when executed by a computing unit, cause the computing unit to execute a method according to any one of claims 1 to 7. Computer-readable medium on which the computer program according to claim 14 is stored.

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