Method for operating exhaust system of internal combustion engine, exhaust system and internal combustion engine
By cooling the exhaust gas in the hydrogen internal combustion engine and monitoring its concentration using traditional hydrogen sensors, the problem of flammable mixture formation caused by unburned hydrogen is solved, the operation safety of the hydrogen internal combustion engine is improved, and explosions and fires are prevented.
Patent Information
- Application Number
- CN202410932501.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-07-14
- Filing Date
- 2024-07-12
- Publication Date
- 2025-01-14
AI Technical Summary
In hydrogen internal combustion engines, unburned hydrogen may form a flammable mixture with oxygen in the exhaust system, resulting in explosions, deflagration and fires. The traditional hydrogen sensor design is not suitable for high temperature environments, making it difficult to effectively monitor and prevent combustion failures.
Hazardous hydrogen concentrations are identified early by cooling the exhaust stream in the exhaust system and measuring its concentration using a conventional hydrogen sensor, and turning off hydrogen delivery through the motor controller to prevent critical mixture formation.
It improves the operation safety of the hydrogen internal combustion engine, prevents the formation of explosive gas mixture, and ensures the safety and integrity of the system.
Smart Images
Figure CN119308745A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for operating an exhaust system of an internal combustion engine that can be operated with hydrogen. The invention also relates to an exhaust system for an internal combustion engine that can be operated with hydrogen, which is suitable for carrying out the method or can be operated according to the method. In addition, an internal combustion engine having an exhaust system according to the invention is specified.
[0002] A preferred field of application of the invention is mobile applications, in particular vehicles with an internal combustion engine that can be operated with hydrogen. Background Art
[0003] In an internal combustion engine that can run on hydrogen, hydrogen is burned as fuel with air in the combustion chamber. It can happen that the hydrogen in the combustion chamber of the motor is not completely burned or not burned at all, so that the exhaust gas discharged from the combustion chamber may contain hydrogen. This unburned hydrogen can form a flammable mixture with oxygen in the exhaust system, which can then ignite on hot exhaust system surfaces, on hot catalysts (temperatures are usually >580°C) and / or by hot exhaust gases from cylinders with complete combustion. If this is the case, it may lead to flame formation at the end of the exhaust pipe, exhaust pipe bursting (due to explosion, deflagration, knock) and / or vehicle fire. These events will not only damage the corresponding components, but also endanger the body and life of passengers and people in the surrounding environment of the vehicle. This needs to be prevented.
[0004] One strategy could be to prevent the causes of the combustion failure and thus the formation of a flammable hydrogen-air mixture in the exhaust system. However, the causes of an incomplete or incomplete combustion in the combustion chamber of an internal combustion engine can be various, such as ignition failure, hydrogen entering the combustion chamber at the wrong time, too little oxygen in the fresh air due to exhaust gas recirculation, too rich a mixture (above the upper ignition limit), too lean a mixture (below the lower ignition limit), etc. Therefore, the diagnosis based on the possible causes is usually very complex, not always reliable, and is usually limited to a single cause. Furthermore, these diagnostics usually do not meet the required safety integrity requirements (ASIL).
[0005] Another strategy could be to mitigate the effects of a combustion failure by monitoring the hydrogen concentration in the exhaust gas. Thus, an undesirable or critical concentration of hydrogen in the exhaust gas can be determined independently of the cause and, if necessary, the system can be switched to a safe state, for example by stopping the supply of hydrogen to the internal combustion engine. However, monitoring the hydrogen concentration in the exhaust gas of an internal combustion engine is problematic because conventional hydrogen sensors are designed for lower temperatures, for example -40° C. to 100° C., and not for the high temperatures that are common in exhaust systems.
[0006] The present invention addresses the following object: to increase safety in the operation of an internal combustion engine operated with hydrogen. In particular, the formation of explosive gas mixtures should be prevented by early detection of increased or dangerously high hydrogen concentrations in the exhaust gas flow of the internal combustion engine.
[0007] In order to achieve this task, a method according to the invention for operating an exhaust system for an internal combustion engine that can be operated with hydrogen and an exhaust system according to the invention for an internal combustion engine that can be operated with hydrogen are proposed. Advantageous expansion schemes of the invention can be found below. In addition, an internal combustion engine with an exhaust system according to the invention is also provided. Summary of the invention
[0008] A method for operating an exhaust system of an internal combustion engine that can be operated with hydrogen is proposed, wherein the hydrogen concentration in the exhaust gas flow of the internal combustion engine is monitored. The method comprises the steps of:
[0009] a) cooling the exhaust gas flow or a partial flow branched off from the exhaust gas flow,
[0010] b) measuring the hydrogen concentration in the cooled exhaust gas flow or in the cooled partial flow by means of a hydrogen sensor,
[0011] c) Comparing the measured value of the hydrogen sensor with a reference value, preferably an expected value that is dependent on the operating point.
[0012] By measuring the hydrogen concentration in the exhaust gas of an internal combustion engine, unburned hydrogen can be detected early. By introducing appropriate measures, such as shutting down the hydrogen supply, reaching a critical hydrogen concentration can then be reliably prevented. Accordingly, safety in the operation of the internal combustion engine is increased. It has proven to be particularly advantageous that conventional hydrogen sensors (i.e. hydrogen sensors designed for the low temperature range) can be used to measure the hydrogen concentration in the exhaust gas, since the exhaust gas is cooled beforehand.
[0013] Depending on the design of the method or of the exhaust gas system for carrying out the method, the entire exhaust gas flow or a partial flow branched off from it is cooled. The latter has the advantage that the branched partial flow can be cooled more simply and more quickly.
[0014] According to a preferred embodiment of the present invention, in step a), the exhaust gas flow or partial flow is cooled by means of a heat exchanger. A cooling medium may flow through the heat exchanger, which absorbs and dissipates heat from the exhaust gas, so that the exhaust gas temperature decreases.
[0015] Preferably, in step a), the exhaust gas flow or the partial flow is cooled to a temperature below 100° C. This ensures an exhaust gas temperature that enables the use of conventional hydrogen sensors (ie hydrogen sensors designed for the low temperature range).
[0016] Furthermore, it is proposed that before step a) and / or before step b), the exhaust gas flow or partial flow is introduced into a line branching off from the exhaust system. Thus, cooling and / or measurement of the hydrogen concentration does not take place in the exhaust system, but in an area separate from the exhaust system, so that separate cooling and / or measuring areas are achieved, which simplify the implementation of the method.
[0017] The line branching off from the exhaust system can be, in particular, an exhaust gas recirculation line or a bypass line. The exhaust gas flow or part of the flow reaches the intake side of the internal combustion engine via the exhaust gas recirculation line so that it is delivered to the internal combustion engine again. For this purpose, the exhaust gas recirculation line can be connected to the intake pipe for supplying air to the internal combustion engine. By cleverly arranging the hydrogen sensor in the exhaust gas recirculation line, for example, in the vicinity of the intake pipe, the sensor can be used to detect hydrogen in the intake pipe. For example, when the engine is stationary, a leak diagnosis can be performed with the aid of the hydrogen sensor, which can identify a leak in a hydrogen injector for blowing hydrogen into the internal combustion engine.
[0018] If the branched-off line is a bypass line, it can only be used for the purpose of determining the hydrogen concentration in the exhaust gas. After flowing through the cooling region and / or the measuring region formed in the bypass line, the exhaust gas flow or the branched-off partial flow can be reintroduced into the exhaust system. The introduction into the exhaust system takes place upstream of at least one component integrated into the exhaust system for exhaust gas aftertreatment or exhaust gas purification.
[0019] Preferably, step c) of the proposed method is performed by means of a motor controller or a separate electronic control unit to which the measurement data of the hydrogen sensor are transmitted. For this purpose, a reference value is stored in the motor controller or the electronic control unit. The reference value can be, in particular, an operating point-dependent desired value which takes into account the current operating point or operating mode of the internal combustion engine. Since no unburned hydrogen should enter the exhaust gas during normal operation of the internal combustion engine, there can be special operating modes in which hydrogen is introduced into the exhaust system in a targeted manner, for example in order to heat a catalytic converter integrated into the exhaust system. The reference value can therefore differ depending on the operating mode.
[0020] If the engine controller or the electronic control unit determines a deviation from the reference value, in particular an excess of the reference value, at least one measure can be initiated by means of the engine controller or the electronic control unit, which prevents the formation of a safety-critical gas mixture in the exhaust system. For example, the supply of hydrogen to the internal combustion engine can be shut off. In this way, deflagrations, knocks and / or fires are prevented, which can damage not only the exhaust system but also people in the surrounding area.
[0021] Furthermore, an exhaust system for an internal combustion engine that can be operated with hydrogen is proposed, comprising an exhaust system for discharging exhaust gas from the internal combustion engine and a line branching off from the exhaust system, in particular an exhaust gas recirculation line or a bypass line, into which a cooling device and a hydrogen sensor downstream of the cooling device are integrated.
[0022] The proposed exhaust gas device is particularly suitable for carrying out the method according to the invention described above. That is to say, the same advantages can be achieved. In particular, the safety in the operation of the exhaust gas device can be improved, because the safety-critical hydrogen concentration in the exhaust gas can be detected early with the help of the hydrogen sensor. The hydrogen sensor can be a conventional hydrogen sensor (i.e., a hydrogen sensor designed for the low temperature range), because the exhaust gas flow or partial flow supplied to the hydrogen sensor is cooled in advance with the help of a cooling device. The cooling device can be, for example, a heat exchanger. With the help of a heat exchanger, the exhaust gas flow or partial flow introduced into the branched pipeline can be cooled to a temperature below 100° C., so that a conventional hydrogen sensor can be used in full.
[0023] Preferably, the hydrogen sensor is arranged in the region of the inlet of the line branching off from the exhaust system into the intake pipe. Thus, the arrangement takes place near the intake pipe. In this arrangement, the hydrogen sensor can additionally be used to detect hydrogen in the intake pipe.
[0024] Furthermore, an internal combustion engine is proposed which can be operated with hydrogen and comprises an exhaust gas device according to the invention. With the exhaust gas device according to the invention, unburned hydrogen can be detected in the exhaust gas. Furthermore, it can be detected early whether the hydrogen concentration is approaching a safety-critical value, so that measures to counteract it can be initiated if necessary.
[0025] The hydrogen required for the internal combustion engine can be blown directly into or into the intake manifold of the internal combustion engine so that it is delivered together with the combustion air. The internal combustion engine can be used in particular to drive vehicles, namely commercial vehicles and passenger cars. In addition, the internal combustion engine can also be used as a "range extender" in vehicles with hybrid drive solutions. Other mobile applications are ship traffic and rail traffic. Furthermore, stationary applications are also conceivable. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 An internal combustion engine which can be operated with hydrogen is shown. DETAILED DESCRIPTION
[0027] from Figure 1 An internal combustion engine 2 which can be operated with hydrogen is known from FIG. The hydrogen is provided by a hydrogen supply unit 9 and is injected directly into the internal combustion engine 2 by means of a hydrogen injection unit 10 . The required air is supplied to the internal combustion engine 2 via an intake pipe 8 .
[0028] The exhaust gas generated when burning hydrogen is discharged via an exhaust system 5, into which an exhaust gas turbine 11 and a component 12 for exhaust gas aftertreatment or exhaust gas purification are integrated in the present case. A pipeline 6 branches off upstream of the exhaust gas turbine 11, through which at least part of the exhaust gas flow in the exhaust system 5 is returned to the intake side of the internal combustion engine 2. For this purpose, the pipeline 6 leads to an intake pipe 8. A heat exchanger 4 for cooling the exhaust gas flow or part of the flow and a hydrogen sensor 3 (downstream of the heat exchanger 4) are integrated into the pipeline 6. Since the exhaust gas flow or part of the flow supplied to the hydrogen sensor 3 is cooled, the hydrogen sensor 3 can be designed for use in a low temperature range. With the help of the hydrogen sensor 3, unburned hydrogen in the exhaust gas can be detected. In addition, the hydrogen concentration in the exhaust gas can be measured so that it can be identified as early as possible whether it is close to a safety-critical value.
[0029] The hydrogen sensor 3 is connected to the motor controller 7 in a data transmission manner, so that the hydrogen sensor 3 can forward its measurement data to the motor controller 7 for evaluation. Preferably, at least one reference value is stored in the motor controller 7, with which the measurement data of the hydrogen sensor 3 can be compared. If the motor controller 7 determines a deviation from the reference value, in particular an excess of the reference value, the hydrogen supply to the internal combustion engine 2 can be shut down. In other words, hydrogen is no longer blown into the internal combustion engine 2.
Claims
1. A method for operating an exhaust system (1) of an internal combustion engine (2) which can be operated with hydrogen, wherein: Monitoring the concentration of hydrogen in the exhaust gas flow of the internal combustion engine (2), the method comprising the steps of: a) cooling the exhaust gas flow or a partial flow branched off from the exhaust gas flow, b) measuring the hydrogen concentration in the cooled exhaust gas flow or in the cooled partial flow by means of a hydrogen sensor (3), c) comparing the measured value of the hydrogen sensor (3) with a reference value, preferably an expected value dependent on the operating point.
2. The method according to claim 1, It is characterized in that In step a), the exhaust gas stream or the partial stream is cooled by means of a heat exchanger (4).
3. The method according to claim 1 or 2, It is characterized in that In step a), the exhaust gas stream or the partial stream is cooled to a temperature below 100° C.
4. The method according to any one of the preceding claims, It is characterized in that Before step a) and / or before step b), the exhaust gas flow or the partial flow is introduced into a line (6) branching off from the exhaust system (5), preferably into an exhaust gas recirculation line or a bypass line.
5. The method according to any one of the preceding claims, It is characterized in that Step c) is performed by means of a motor controller (7) or a separate electronic control unit, to which the measurement data of the hydrogen sensor (3) are transmitted.
6. An exhaust device (1) for an internal combustion engine (2) that can be operated with hydrogen, the exhaust device comprising an exhaust system (5) for discharging exhaust gases from the internal combustion engine (2) and a pipeline (6) branching off from the exhaust system (5), in particular an exhaust gas recirculation pipeline or a bypass pipeline, a cooling device and a hydrogen sensor (3) downstream of the cooling device being integrated into the pipeline.
7. The exhaust device (1) according to claim 6, It is characterized in that The cooling device is a heat exchanger (4).
8. The exhaust device (1) according to claim 7 or 8, It is characterized in that The hydrogen sensor (3) is arranged in the region of the inlet of the line (6) into the intake pipe (8).
9. An internal combustion engine (2) which can be operated with hydrogen and comprises an exhaust system (1) according to any one of claims 6 to 8.