DE102020209156A1 - Exhaust system for a hydrogen internal combustion engine and method for operating an exhaust system of a hydrogen internal combustion engine - Google Patents

Abstract

The present invention relates to an exhaust system (100) for a hydrogen internal combustion engine (10) and a method for operating an exhaust system (100) of a hydrogen internal combustion engine that is operated with hydrogen gas as fuel. The exhaust line (100) according to the invention comprises an exhaust pipe (102), a first catalytic converter device (110) arranged in the exhaust pipe (102) and designed to at least partially post-treat the exhaust gas, a catalytic converter device (110) installed in the exhaust pipe (102) upstream of the first catalytic converter device ( 110) arranged second catalyst device (120), which is designed to at least partially post-treat the exhaust gas, and a hydrogen gas injection device (170) arranged upstream of the second catalyst device (120), which is designed to inject hydrogen gas so that the injected hydrogen gas with the in the second catalytic device (120) reacts oxygen present to heat the exhaust gas.

Description

The present invention relates to an exhaust system for a hydrogen internal combustion engine and a method for operating an exhaust system of a hydrogen internal combustion engine, in particular an exhaust system for a hydrogen internal combustion engine with a device for rapidly heating the catalyst device and a corresponding method for this

Hydrogen internal combustion engines are becoming more important as emission regulations become more stringent, particularly with regard to carbon oxide emissions. In the case of a hydrogen combustion engine, due to the high temperatures and the nitrogen present in the air, nitrogen oxides can also occur in the exhaust gas, which can be post-treated with the aid of a catalytic converter device, such as a catalytic converter device based on the principle of selective catalytic reduction, in combination with hydrogen gas. to reduce nitrogen oxide emissions as much as possible. It is known from fossil internal combustion engines that a catalytic converter device, such as a catalytic converter device based on the principle of selective catalytic reduction, must be heated to a predetermined operating temperature so that efficient conversion of the nitrogen oxides can be implemented. For this purpose, it is known to combine a conventional catalyst substrate with an electrically heatable disc that can heat the catalyst substrate to the predetermined temperature.

Furthermore, from the DE 10 2007 021 827 A1 an exhaust gas purification system for a hydrogen engine is known. The exhaust gas purification system disclosed therein includes a hydrogen storage tank for storing high-pressure hydrogen, a hydrogen engine for combusting hydrogen supplied from the hydrogen storage tank, and a catalyst. The emission control system is capable of introducing hydrogen gas into the exhaust pipe during the operation of the hydrogen engine. Further, the system includes an upstream exhaust gas sensor arranged in the exhaust pipe upstream of the catalyst for detecting the exhaust element, and a downstream hydrogen gas injector formed upstream of the upstream exhaust gas sensor for injecting hydrogen gas into the exhaust pipe.

The present invention is at least partially based on the object of providing an exhaust system for a hydrogen internal combustion engine and a method for operating an exhaust system of a hydrogen internal combustion engine, with which the catalytic converter device arranged in the exhaust system can be heated to its operating temperature as early and quickly as possible.

This object is achieved with an exhaust line for a hydrogen internal combustion engine according to independent claim 1 and a method for operating an exhaust line of a hydrogen internal combustion engine having the features according to independent claim 10 . Preferred and advantageous configurations are specified in the dependent claims.

The present invention is essentially based on the idea of heating a (main) catalytic converter device, in particular an SCR catalytic converter device, of an exhaust system for a hydrogen internal combustion engine to its predetermined operating temperature in that an additional catalytic converter device upstream of the (main) catalytic converter device and a hydrogen gas injection device, adapted to inject hydrogen gas upstream of the further catalyst device, to allow the injected hydrogen gas to react with the oxygen present in the further catalyst device to heat the exhaust gas. The exhaust gas heated in this way can then be used by the (main) catalytic converter device to heat it up early, in order to heat it up to the predetermined operating temperature as early and as quickly as possible.

Thus, according to a first aspect, an exhaust system for a hydrogen internal combustion engine configured to be operated with hydrogen gas as a fuel is disclosed. The hydrogen gas is combusted with air in at least one combustion chamber. The exhaust line according to the invention has an exhaust line for conducting the exhaust gas flowing out of the at least one combustion chamber, a first catalytic converter device which is arranged in the exhaust line downstream of the at least one combustion chamber and is designed to at least partially post-treat the exhaust gas, an exhaust line in the exhaust line downstream of the at least one combustion chamber and a second catalytic converter device arranged upstream of the first catalytic converter device, which is designed to at least partially after-treat the exhaust gas, and a hydrogen gas injection device arranged upstream of the second catalytic converter device, which is designed to inject hydrogen gas so that the injected hydrogen gas is mixed with the oxygen present in the second catalytic converter device reacts to heat the exhaust gas and upon further flow through the exhaust pipe and through the first catalytic device device to a predetermined operation heated to room temperature.

The invention makes use of the fact that in the second catalytic converter device the hydrogen gas injected upstream can react with the oxygen contained therein and lead to exothermic energy, which at the same time can significantly heat the exhaust gas flowing through it. The further flowing, significantly heated exhaust gas can then heat the first catalytic converter device, which is arranged in the exhaust pipe downstream of the second catalytic converter device, to the predetermined operating temperature much faster. This can lead to the first (main) catalytic converter device getting into its efficient normal operation earlier and thus the pollutant emissions of the hydrogen internal combustion engine can be reduced.

The first catalytic converter device is preferably a so-called SCR catalytic converter device, which is based on the principle of selective catalytic reduction with hydrogen gas. Here, the injected hydrogen gas is converted into water and nitrogen with the nitrogen oxides in the exhaust gas.

Furthermore, it is preferred that the second catalyst device is an oxidation catalyst device. At this time, the injected hydrogen gas can easily combine with the oxygen present in the oxidation catalyst device by catalytic action, thereby releasing thermal energy. This released thermal energy heats the exhaust gas, which in turn can heat the first catalytic device more quickly.

Furthermore, it is advantageous if the exhaust line according to the invention also has a bypass line which is designed to direct the exhaust gas past the second catalytic converter device directly to the first catalytic converter device. The bypass line is arranged in such a way that it bypasses that area of the exhaust line in which the second catalytic converter device is arranged and directs the exhaust gas past it so that it can then flow directly through the first catalytic converter device.

A control valve is preferably located at least partially in the bypass line and is configured to direct the exhaust gas flow either through the second catalytic converter device or through the bypass line. The control valve is preferably a 3/2-way valve.

In a further preferred embodiment, the exhaust system according to the invention also has a further hydrogen gas injection device which is designed to inject hydrogen gas into the exhaust pipe at a position upstream of the first catalytic converter device and downstream of the second catalytic converter device. In particular, the hydrogen gas injected by means of the at least one further hydrogen gas injection device serves as a reducing agent for the reduction taking place in the first catalytic converter device.

In a further advantageous embodiment of the exhaust line according to the invention, the hydrogen gas injection device is designed to inject hydrogen into the at least one combustion chamber during a working phase and/or during an exhaust phase of the hydrogen internal combustion engine. In particular, the main injection device for the hydrogen gas can be used to introduce unburned hydrogen gas into the exhaust pipe so that, as already mentioned, this can react with the oxygen present in the second catalytic converter device to heat the exhaust gas.

According to a further aspect of the present invention, a hydrogen engine is disclosed which has at least one combustion chamber and an exhaust line according to the invention arranged downstream of the at least one combustion chamber.

According to a further aspect of the present invention, a method for operating an exhaust train of a hydrogen internal combustion engine configured to be operated with hydrogen gas as a fuel is disclosed. The hydrogen gas is burned with air in at least one combustion chamber. The exhaust system has an exhaust pipe for conducting the exhaust gas flowing out of the at least one combustion chamber, a first catalytic converter device which is arranged in the exhaust pipe downstream of the at least one combustion chamber and is designed to at least partially post-treat the exhaust gas, a catalytic converter device in the exhaust pipe downstream of the at least one combustion chamber and a second catalyst device arranged upstream of the first catalyst device and designed to at least partially after-treat the exhaust gas, and a hydrogen gas injection device arranged upstream of the second catalyst device and designed to inject hydrogen gas. The method of the present invention includes injecting hydrogen gas by means of the hydrogen gas injector to allow the injected hydrogen gas to react with the oxygen present in the second catalyst device to heat the exhaust gas, heating the first catalyst device by flowing the exhaust gas heated in the second catalyst device therethrough, and terminating the injection of hydrogen gas when the temperature of the first catalyst device has reached a predetermined operating temperature.

The additional hydrogen gas is injected into the exhaust line until the first catalytic converter device is heated to its predetermined operating temperature. The operation of the exhaust system then switches to normal operation.

Preferably, the exhaust system also has a bypass line, which is designed to conduct the exhaust gas past the second catalytic converter device to the first catalytic converter device, and a control valve which is at least partially arranged in the bypass line and is designed to direct the exhaust gas flow either through the second exhaust gas catalytic converter device or through the bypass line. In particular, hydrogen gas is injected when the control valve blocks the bypass line and the exhaust gas together with the injected hydrogen gas can consequently flow through the second catalytic converter device.

In a further preferred embodiment, the method according to the invention further comprises injecting additional hydrogen gas into the exhaust line at a position upstream of the first catalyst device and downstream of the second catalyst device when the temperature of the first catalyst device has reached the predetermined operating temperature. The additional injection of the hydrogen gas is thus used during normal operation of the exhaust system as a reducing agent for the first catalytic converter device, which is in particular an SCR catalytic converter device.

In an alternative embodiment, the method according to the invention further includes injecting additional hydrogen gas into the at least one combustion chamber during a working phase and/or during an exhaust phase of the hydrogen internal combustion engine when the temperature of the first catalytic converter device has reached the predetermined operating temperature. In particular, as a result, unburned hydrogen gas can get into the exhaust line and be used there as a reducing agent in the first catalytic converter device.

Preferably, the predetermined operating temperature of the first catalytic device is approximately 100°C.

In a further preferred embodiment, the method according to the invention also includes determining that the hydrogen internal combustion engine has started, with hydrogen gas being injected to heat the first catalytic converter device when it has been determined that the hydrogen internal combustion engine has started.

• 1 eine schematische Ansicht eines beispielhaften Wasserstoffverbrennungsmotors mit einem erfindungsgemäßen Abgasstrang zeigt,
• 2 eine schematische Ansicht eines beispielhaften Wasserstoffverbrennungsmotors mit einem weiteren erfindungsgemäßen Abgasstrang zeigt, und
• 3 ein beispielhaftes Ablaufdiagramm eines erfindungsgemäßen Verfahrens zum Betreiben eines Abgasstrangs eines Wasserstoffverbrennungsmotors zeigt.

Other objects and features of the present invention will become apparent to those skilled in the art by practicing the present teachings and considering the accompanying drawings, in which:

• 1 shows a schematic view of an exemplary hydrogen internal combustion engine with an exhaust system according to the invention,
• 2 shows a schematic view of an exemplary hydrogen internal combustion engine with a further exhaust system according to the invention, and
• 3 shows an exemplary flow chart of a method according to the invention for operating an exhaust system of a hydrogen internal combustion engine.

Elements of the same construction or function are provided with the same reference symbols across the figures.

the 1 shows a schematic view of an exemplary hydrogen internal combustion engine 10 with an exhaust system 100 according to the invention. The hydrogen internal combustion engine 10 is operated with hydrogen gas as fuel and is known in principle from the prior art. In particular, a hydrogen gas-air mixture is burned in at least one combustion chamber (not shown explicitly) of the hydrogen internal combustion engine 10 and the exhaust gas obtained is released to the environment via the exhaust system 100 according to the invention. The hydrogen internal combustion engine 10 is in particular a four-stroke engine with the phases intake, compression, work and exhaust.

The exhaust line 100 has an exhaust line 102 which is fluidly connected to the at least one combustion chamber (not explicitly shown) of the internal combustion engine 10 and is designed to conduct the exhaust gas flowing out of the at least one combustion chamber. The exhaust line 100 also has a first catalytic converter device 110 which is arranged in the exhaust line 102 downstream of the at least one combustion chamber and is designed to at least partially post-treat the exhaust gas. The first catalyst device 110 is preferably an SCR catalyst device based on the principle of selective catalytic reduction with hydrogen gas.

The exhaust line 100 also has a second catalytic converter device 120 which is arranged in the exhaust pipe 102 downstream of the at least one combustion chamber and upstream of the first catalytic converter device 110 and is designed for this purpose is to at least partially post-treat the exhaust gas. The second catalyst device 120 is preferably an oxidation catalyst device.

The exhaust system 100 also has a sensor device 130, which is arranged downstream of the first catalytic converter device 110 and is designed to measure the exhaust gas with regard to its components.

Sensor device 130 is preferably a nitrogen oxide sensor which is designed to detect any nitrogen oxides present in the exhaust gas. Sensor device 130 can be designed, for example, as a nitrogen oxide sensor with an additionally integrated mixed potential electrode or sensor and can be based on the electrochemical principle. Sensor device 130 can preferably detect the nitrogen oxide concentration and hydrogen concentration in the exhaust gas.

Optionally, a further sensor device 140 can be provided, which is arranged downstream of the at least one combustion chamber and upstream of the second catalytic converter device 120 in the exhaust gas line 102 and can be designed to detect components in the exhaust gas. Further sensor device 140 is preferably also a nitrogen oxide sensor, which is designed to detect nitrogen oxides present in the exhaust gas.

Furthermore, the exhaust line 100 of 1 a hydrogen gas injector 150 configured to inject hydrogen gas into the exhaust pipe 102 at a position downstream of the second catalyst device 120 and upstream of the first catalyst device 110 . In particular, the hydrogen gas injected by the hydrogen gas injection device 150 can be used as a reducing agent for the first catalyst device 110 .

The exhaust line 100 of 1 may further comprise a hydrogen gas injection device 170 arranged upstream of the second catalytic converter device 120 and downstream of the at least one combustion chamber, which is configured to inject hydrogen gas as a reducing agent into the exhaust line 102.

First sensor device 130, second sensor device 140, hydrogen gas injection device 150 and hydrogen gas injection device 170 are each connected to a control device 160, which is designed to receive the respective signals and also in turn to send signals for controlling the hydrogen gas injection by means of hydrogen gas injection devices 150, 170 steer. Sensor device 140 is provided for controlling the amount of hydrogen gas to be injected by means of hydrogen gas injection device 170 .

the 2 shows a further inventive embodiment of an exhaust line 100 for a hydrogen internal combustion engine 10. The exhaust line 100 of FIG 2 differs from the exhaust system 1 in that a bypass line 104 is additionally provided, which directs the exhaust gas emerging from the at least one combustion chamber of the hydrogen internal combustion engine 10 around the second catalytic converter device 120 to the first catalytic converter device 110 . To control the exhaust gas, a control valve 106 is provided upstream of the second catalytic converter device 120 for this purpose, which is at least partially arranged in the bypass line 104 . The control valve 106 is thus provided in the upstream orifice of the bypass line 104 into the exhaust line 102 and is preferably a 3/2-way valve and can route the exhaust gas either through the bypass 104 or through the second catalytic converter device 120 . To control the control valve 106, the control valve 106 is connected to the control device 160.

In addition, the exhaust line 100 differs 2 from the exhaust system 100 of 1 in that the hydrogen gas injector 150 in the embodiment according to FIG 2 is not available. The hydrogen gas, which serves as a reducing agent for the first catalytic converter device 110, can be taken from that hydrogen gas injection device which represents the main hydrogen gas injection device for the at least one combustion chamber of the hydrogen internal combustion engine 10. It is of course self-evident for the person skilled in the art that also in the design according to 2 the hydrogen gas injector 150 may be arranged, which in turn may be arranged downstream of the second catalyst device 120 and upstream of the first catalyst device 110 .

Referring to the 3 is an exemplary flowchart of a method according to the invention for operating the exhaust system according to the invention 1 described.

The procedure according to 3 starts at step 200 and then proceeds to step 210 where it is determined whether the hydrogen engine 10 has been started. The method remains at step 210 until a start of the hydrogen internal combustion engine 10 has been determined.

When it is determined in step 210 that a hydrogen engine start is occurring , the process proceeds to step 220 where hydrogen gas is injected into the exhaust pipe 102 by the hydrogen gas injector 170 . The hydrogen gas injected via the hydrogen gas injector 170 may react with the oxygen present in the second catalytic device 120 and generate exothermic energy that significantly increases the temperature of the exhaust gas. The heated exhaust gas then flows on to the first catalytic device 110 where it can then give up the heat thereto in turn in order to at least partially warm the first catalytic device 110 .

In a subsequent step 230, it is determined whether the first catalytic converter device 110 has reached its operating temperature. If it is determined in step 230 that the operating temperature of the first catalytic converter device 110 has not yet been reached, the method returns to step 220 and hydrogen gas continues to be injected by means of the hydrogen gas injection device 170 .

If it is determined in step 230 that the predetermined operating temperature, for example approximately 100 °C, of the first catalytic converter device 110 has been reached, the method proceeds to step 240, at which the injection of the hydrogen gas provided for heating by means of the further hydrogen gas injection device 170 is ended and in the normal operation of the exhaust line 100 is switched. Then, during normal operation, hydrogen gas serving as a reducing agent for the first catalyst device 110 is injected by the hydrogen gas injector 150 . The method then ends at step 250.

At step 220, as an alternative to injecting hydrogen gas by means of the hydrogen gas injector 170, the hydrogen gas provided for heating the exhaust gas in the second catalytic converter device can also come from a main hydrogen gas injector, which is injected during a working phase and/or exhaust phase of the hydrogen internal combustion engine 10 and unburned into the exhaust system 100 can flow.

With additional reference to the 2 First catalytic converter device 110 can also be heated by additionally injected hydrogen gas by controlling control valve 106 during the warm-up phase of first catalytic converter device 110 in such a way that the exhaust gas flows through second catalytic converter device 120 and therefore does not pass through bypass 104. Consequently, the hydrogen gas can react with the oxygen present in the second catalytic device 110 and, as previously described, significantly heat the exhaust gas before it flows into the first catalytic device 100 .

Once at step 230 the 3 it is determined that the predetermined operating temperature of the first catalytic converter device 110 has been reached, the control valve 106 switches to a position in which the exhaust gas passes through the bypass 104 and no longer through the second catalytic converter device 120. At the same time, the injection of the to heat the first Catalyst device 110 provided hydrogen gas (either by means of the hydrogen gas injector 170 or via the main hydrogen gas injector of the hydrogen internal combustion engine) and the method then proceeds to step 240, where the exhaust line is switched to normal operation for after-treatment of the exhaust gas.

The measure of heating the catalyst by oxidizing hydrogen gas with oxygen in the oxidation catalyst can also be reinforced with other heating measures such as delayed ignition timing and/or increasing the engine speed when idling after the start (e.g. above 1500 rpm), whereby the other measures can continue to exist until the Catalyst device reaches its operating temperature of about 100 ° C.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102007021827 A1 [0003]

Claims (15)

Exhaust system (100) for a hydrogen internal combustion engine (10), which is designed to be operated with hydrogen gas as fuel, the hydrogen gas being combusted with air in at least one combustion chamber, the exhaust system (100) having: - an exhaust pipe (102) for conducting the exhaust gas flowing out of the at least one combustion chamber, - a first catalytic converter device (110) which is arranged in the exhaust pipe (102) downstream of the at least one combustion chamber and is designed to at least partially post-treat the exhaust gas, - a second catalytic converter device (120) arranged in the exhaust pipe (102) downstream of the at least one combustion chamber and upstream of the first catalytic converter device (110), which is designed to at least partially post-treat the exhaust gas, and - a hydrogen gas injection device (170) arranged upstream of the second catalytic device (120) and adapted to inject hydrogen gas so that the injected hydrogen gas reacts with the oxygen present in the second catalytic device (120) to heat the exhaust gas. Exhaust system (100) after claim 1 , wherein the first catalyst device is an SCR catalyst device (110) based on the principle of selective catalytic reduction with hydrogen gas. The exhaust system (100) according to any one of the preceding claims, wherein the second catalyst device is an oxidation catalyst device (120). Exhaust line (100) according to any one of the preceding claims, further comprising - A bypass line (104) which is designed to conduct the exhaust gas past the second catalytic converter device (120) to the first catalytic converter device (110). Exhaust system (100) after claim 4 , further comprising: - a control valve (106) arranged at least partially in the bypass line (104) and adapted to direct the flow of exhaust gas either through the second catalytic device (120) or through the bypass line (104). Exhaust system (100) after claim 5 , wherein the control valve is a 3/2-way valve. The exhaust system (100) according to any one of the preceding claims, further comprising a further hydrogen gas injector (150) which is adapted to inject hydrogen gas into the exhaust line (102) at a position upstream of the first catalyst device (110) and downstream of the second catalyst device (120). . Exhaust system (100) according to one of Claims 1 until 6 , wherein the hydrogen injection device is designed to inject hydrogen into the at least one combustion chamber of the hydrogen internal combustion engine (10) during a working phase and/or during an exhaust phase of the hydrogen internal combustion engine (10). Hydrogen engine (10) with: - at least one combustion chamber, and - A downstream of the at least one combustion chamber arranged exhaust line (100) according to any one of the preceding claims. Method for operating an exhaust system (100) of a hydrogen internal combustion engine, which is designed to be operated with hydrogen gas as fuel, the hydrogen gas being combusted with air in at least one combustion chamber, the exhaust system (100) having an exhaust line (102) for conducting the from the exhaust gas flowing out of at least one combustion chamber, a first catalytic converter device (110) which is arranged in the exhaust gas line (102) downstream of the at least one combustion chamber and is designed to at least partially post-treat the exhaust gas, a first catalytic converter device (110) in the exhaust gas line (102) downstream of the at least one combustion chamber and a second catalyst device (120) arranged upstream of the first catalyst device (110) and designed to at least partially post-treat the exhaust gas, a hydrogen gas injection device (170) arranged upstream of the second catalyst device (120) and designed to inject hydrogeng to inject as, the method comprising: - injecting hydrogen gas by means of the hydrogen injection device (170) so that the injected hydrogen gas reacts with the oxygen stored in the second catalytic device (120) to heat the exhaust gas, - heating the first catalytic device (110) by flowing the exhaust gas heated in the first catalytic device (120) therethrough, and - stopping the injection of hydrogen gas when the temperature of the first catalyst device (110) has reached a predetermined operating temperature. procedure after claim 10 , The exhaust line (100) further comprising a bypass line (104) which is designed to the exhaust gas at the second catalytic converter device (120) past the first catalytic converter device (110), and having a control valve (106) which is at least partially arranged in the bypass line (104) and which is designed to direct the exhaust gas flow either through the second catalytic converter device (120) or through the bypass line (104), the injection of hydrogen gas occurring when the control valve (106) blocks the bypass line (104) and directs the exhaust gas through the second catalytic device (120). Procedure according to one of Claims 10 and 11 , further comprising: - injecting additional hydrogen gas into the exhaust line (102) at a position upstream of the first catalyst device (110) and downstream of the second catalyst device (120) when the first catalyst device (110) has reached the predetermined operating temperature. Procedure according to one of Claims 10 and 11 , further comprising: - injecting hydrogen gas into the at least one combustion chamber during a working phase or during an exhaust phase of the hydrogen internal combustion engine when the first catalytic device (110) has reached the predetermined operating temperature. Procedure according to one of Claims 10 until 13 , wherein the predetermined operating temperature is about 100 °C. Procedure according to one of Claims 10 until 14 , further comprising: - determining a successful start of the hydrogen internal combustion engine, wherein the hydrogen gas is injected to heat the first catalyst device (110) when a successful start of the hydrogen internal combustion engine is determined.

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