Device for exhaust gas recirculation and method for preventing ice formation in such a device

Abstract

The invention relates to an exhaust gas recirculation device for an internal combustion engine (1) with an exhaust gas recirculation line (2) comprising an exhaust gas recirculation cooler (11), an exhaust gas recirculation valve (10), and a catalyst (12). The device according to the invention is characterized in that the catalyst (12) is arranged downstream of the exhaust gas recirculation cooler in the direction of flow. A defined fuel concentration in the exhaust gas can be set via specific combustion and / or ignition control, which is then converted in the catalyst with the generation of heat.

Description

[0001] The invention relates to an exhaust gas recirculation device for an internal combustion engine, in particular a gas engine, according to the type defined in more detail in the preamble of claim 1. The invention also relates to a method for preventing ice formation in such an exhaust gas recirculation system.

[0002] The use of exhaust gas recirculation (EGR) in internal combustion engines is generally known from the state of the art. To improve combustion and raw emissions under certain operating conditions, a portion of the exhaust gas can be recirculated via an EGR line into an intake air line leading to the internal combustion engine. US 2012 / 0055156 A1 serves as a purely illustrative example. This patent depicts such a setup, in which the EGR line branches off from the exhaust pipe of the internal combustion engine upstream of a turbine. The exhaust gas then flows first through a catalyst to reduce nitrogen oxides, a sensor, and an EGR cooler. The flow rate is then regulated by an EGR valve before the exhaust gas is returned to the intake air leading to the internal combustion engine after passing through a compressor and an intercooler.

[0003] A similar setup with a NOx catalyst is also shown in JP 2020-033974 A.

[0004] The catalysts described in these writings therefore serve to clean the exhaust gas and are arranged in the direction of flow upstream of the exhaust gas recirculation cooler and the exhaust gas recirculation valve in order to reduce contamination of these components accordingly.

[0005] In gas engines, and especially hydrogen engines, the exhaust gases have a very high water content of up to 30%. The exhaust gas recirculation (EGR) valve is typically designed to allow a certain amount of leakage to adjust the exhaust gas flow rate under varying temperatures and conditions. However, this leakage becomes problematic in cold ambient conditions and with a high water content in the recirculated exhaust gas, as contact with the cold intake air can lead to condensation and ice formation. This can, for example, block a throttle valve or restrict the flow cross-section for the incoming air and / or the recirculated exhaust gas to such an extent that the combustion engine can no longer operate efficiently.

[0006] To avoid the problems of freezing water in the exhaust gas recirculation (EGR) line and the intake manifold area after the exhaust gas has been recirculated, an EGR valve that seals completely can be used. By reducing leakage in this way, the use of the EGR line can be completely prevented at very low ambient temperatures. However, this has its drawbacks, as such EGR valves are relatively expensive and tend to fail relatively quickly due to potential contamination in the exhaust system.

[0007] Another well-known alternative is electrical heating of the affected components, which is correspondingly complex and energy-intensive, or heating via the combustion engine's coolant, which is even more disadvantageous in terms of complexity, as it requires the installation of appropriate valves and the routing of fluid lines. Furthermore, complex heat exchangers are necessary.

[0008] The object of the present invention is to provide an improved device for the recirculation of exhaust gas, in particular for hydrogen-powered combustion engines, which reduces the problem of freezing simply and efficiently.

[0009] According to the invention, this problem is solved by a device having the features of claim 1, and in particular the characterizing part of claim 1. Advantageous embodiments and further developments of the device according to the invention are described in the dependent claims. Furthermore, a method having the features of claim 6 solves the problem.

[0010] The device according to the invention provides an exhaust gas recirculation line which, similar to the prior art, has an exhaust gas recirculation valve, an exhaust gas recirculation cooler and a catalyst.

[0011] According to the invention, this catalyst, unlike in the prior art, is arranged downstream of the exhaust gas recirculation cooler in the direction of exhaust gas flow. It comprises a platinum group metal (also known as platinum group metals (PGM), Pt, Ir, Os, Pd, Rh, Ru) or a combination of several platinum group metals, which, for example, can be applied as a coating to metallic or ceramic supports or can be contained within the catalyst in the form of pellets or coated ceramic pellets. Fuel, and in particular hydrogen, which reaches the catalyst, is thus able to be catalytically oxidized within it. Particularly with hydrogen, very low temperatures on the order of 25°C are sufficient to enable a catalytic reaction.In this way, sufficient heat can be supplied to the exhaust gas recirculation line, and thus ultimately to the intake manifold of the combustion engine, to reliably prevent icing even at low ambient temperatures. The design is exceptionally simple and efficient. It requires no electrical heating elements or similar components and still allows the use of a conventional exhaust gas recirculation valve, which, by its very nature, permits a certain degree of leakage.

[0012] As already mentioned, the internal combustion engine is preferably designed as a gas engine, in particular as a hydrogen engine.

[0013] According to a particularly advantageous embodiment of the device according to the invention, the exhaust gas recirculation line can branch off from the exhaust gas line of the internal combustion engine upstream of a turbine and lead into the intake air line to the internal combustion engine downstream of a compressor. This is therefore a so-called high-pressure exhaust gas recirculation system, which operates at the pressure level between the compressor and a turbine of a turbocharger provided here.

[0014] Between the compressor and the outlet of the exhaust gas recirculation line, an intercooler and a throttle valve can be arranged, so that the regularly flowing air is conveyed via the compressor, sent through the intercooler, and then metered into the combustion engine via the throttle valve. The recirculated exhaust gas then enters the intake air system in the direction of airflow after this throttle valve.

[0015] The exhaust gas recirculation valve can, in principle, be positioned either before or after the exhaust gas recirculation cooler. According to a particularly advantageous embodiment, it is positioned between the exhaust gas recirculation cooler and the branch of the exhaust gas recirculation line from the exhaust pipe. The exhaust gas recirculation valve is therefore the first component within the exhaust gas recirculation line.

[0016] The inventive method for preventing ice formation in such a device is designed such that combustion and / or ignition in the internal combustion engine is controlled in such a way that a defined quantity of fuel, in particular a defined quantity of hydrogen, is supplied to the catalyst. The hydrogen thus passes unburned through the internal combustion engine to the catalyst. There it is catalytically reacted or burned in order to prevent ice formation through the heat of combustion.

[0017] Further advantageous embodiments of the invention also result from the exemplary embodiment, which is described in more detail below with reference to the figure.

[0018] In the only attached Figure 1 A schematic representation of an internal combustion engine and a device for exhaust gas recirculation can be seen.

[0019] The core of the schematic representation of the Figure 1The system comprises an internal combustion engine, designated 1, which is specifically designed as a hydrogen engine. This internal combustion engine 1 has an exhaust gas recirculation device with an exhaust gas recirculation line 2, which branches off from an exhaust line 3 of the internal combustion engine 1 in the direction of flow upstream of a turbine 4 of a turbocharger 5. In this turbocharger 5, the turbine 4 drives a compressor 6, which supplies compressed intake air to the internal combustion engine 1 via an intake air line 7. An intercooler 8 and a throttle valve 9 are arranged in this intake air line 7 in a manner known per se.

[0020] The exhaust gas recirculation line 2 branches off from the exhaust gas line 3 before the turbine 4 and leads into the intake air line 7 after the compressor 6. This is therefore a so-called high-pressure exhaust gas recirculation.

[0021] In a manner known per se, an exhaust gas recirculation valve 10 and an exhaust gas recirculation cooler 11 are arranged within the exhaust gas recirculation line 2. Downstream of this exhaust gas recirculation cooler 11, before the exhaust gas recirculation line 2 opens into the intake air line 7, a catalyst, here designated 12, follows. This catalyst 12 comprises a platinum group metal (PGM), such as Pt, Ir, Os, Pd, Rh, or Ru, or a combination of several platinum group metals, which are applied, for example, as a coating on metallic or ceramic substrates. Due to its special properties, it is thus able to catalytically combust hydrogen even at very low temperatures on the order of 25°C.If there is a risk of ice formation in the exhaust gas recirculation line 2 and / or the supply line 7 after the exhaust gas recirculation line 2 has entered it, then the combustion or ignition can be controlled by a control system of the combustion engine 1 (not shown here) so that a defined amount of hydrogen flows unburned from the combustion engine 1, is recirculated through the exhaust gas recirculation line 2 and can therefore be catalytically combusted in the catalyst 12.

[0022] The control system, which is essentially part of the engine control unit that is required anyway, can therefore be used to achieve a targeted heat input in the area of ​​the catalyst 12 and thus reliably prevent the icing of the exhaust gas recirculation line 2 or the intake air line 7, after the exhaust gas recirculation line 2 has connected to it, using only chemical energy from the fuel. The entire system is purely passive and requires no additional valves, electrical switching elements, electrical wiring, fluid lines, or the like.

Claims

1. Exhaust gas recirculation device for an internal combustion engine (1) with an exhaust gas recirculation line (2) which has an exhaust gas recirculation cooler (11), an exhaust gas recirculation valve (10) and a catalyst (12), characterized by the fact that the catalyst (12) is arranged in the direction of flow of the recirculated exhaust gas downstream of the exhaust gas recirculation cooler.

2. Exhaust gas recirculation device for an internal combustion engine, which is designed as a gas engine, in particular as a hydrogen engine.

3. Exhaust gas recirculation device according to claim 1 or 2, characterized by the fact that the exhaust gas recirculation line (2) branches off from an exhaust gas line (3) of the internal combustion engine (1) before a turbine (4) and leads into an air supply line (7) to the internal combustion engine (1) after a compressor (6).

4. Exhaust gas recirculation device according to claim 1, 2 or 3, characterized by the fact thatBetween the compressor (6) and the outlet of the exhaust gas recirculation line (2) a charge air cooler (8) and a throttle valve (9) are arranged in the intake air line.

5. Exhaust gas recirculation device according to one of claims 1 to 4, characterized by the fact that the exhaust gas recirculation valve (10) is arranged between the exhaust gas recirculation cooler (11) and the branch of the exhaust gas recirculation line (2) from the exhaust gas line (3).

6. Method for preventing ice formation in a device according to one of claims 1 to 5, wherein a defined amount of unburned fuel is set at the catalyst (12) by controlling the combustion and / or ignition in the internal combustion engine (1), where it is catalytically combusted to prevent ice formation by the heat of combustion.

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