Internal combustion engine with an exhaust system

Abstract

Internal combustion engine (1) with at least one cylinder (2) and with an exhaust system (3) arranged on an exhaust manifold (4) arranged on the internal combustion engine (1), wherein a turbine housing with a turbine wheel (5) of an exhaust gas turbocharger (6) is arranged in the exhaust system (3) and a first exhaust gas purification system (7) is arranged behind the turbine housing in the flow direction of an exhaust gas, wherein a first exhaust pipe (8), in which a first shut-off element (11) is arranged, branches off from the exhaust manifold (4) carrying exhaust gas and opens back into the exhaust system (3) after the first exhaust gas purification system (7), characterized in that the exhaust manifold (4) is connected to the exhaust system (3) between the turbine wheel (5) and the first exhaust gas purification system (7) via a second exhaust pipe (9), in which a second shut-off element (10) is arranged, and to the exhaust system (3) via the first exhaust pipe (8) in the flow direction of the exhaust gas. can be connected by the shut-off elements (10,11) are arranged in series, the first exhaust pipe (8) and the second exhaust pipe (9) have a single connection to the exhaust manifold (4), the second shut-off element (10) is arranged upstream of the first shut-off element (11) in the flow direction and the second exhaust pipe (9) branches off from the first exhaust pipe (8) between the second shut-off element (10) and the first shut-off element (11) and opens into the exhaust system (3) between the turbine wheel (5) and the first exhaust gas purification system (7).

Description

The invention relates to an internal combustion engine having an exhaust system with the features from the preamble of claim 1.With regard to the technical field, reference is made, for example, to German laid-open specification DE 28 51 675 A1. This laid-open specification discloses a post-combustion device for the exhaust gases of internal combustion engines. An apparatus is proposed for post-burning exhaust gases of internal combustion engines with a catalytic converter, for the oxidation of CO (carbon monoxide) and HC (hydrocarbons), in which, in the upper load range of the internal combustion engine, a part of the exhaust gas is conducted through an exhaust gas duct, bypassing a catalytic converter, a second catalytic converter being arranged downstream of the catalytic converter in the exhaust gas duct.A further development of the post-combustion device known from DE 28 51 675 A1 is described in DE 10 2017 218 837 A1. This patent application describes an internal combustion engine having an exhaust system which has an exhaust manifold which is connected to the internal combustion engine. In the exhaust system, a first exhaust gas purification system and, downstream thereof, a second exhaust gas purification system are arranged. The first exhaust gas purification system can be bypassed by a shut-off element via a bypass, wherein the shut-off element is arranged in the exhaust manifold.DE 10 2006 038 289 A1 and EP 2 372 122 A1 disclose an exhaust gas purification device for a combustion engine of the generic type. DE 41 27 634 A1 discloses an exhaust system.In gasoline engines, the fuel-air mixture is normally enriched (lambda<1) at high engine speeds and high power in order to protect the exhaust-gas-carrying components from thermal overloading. This applies in particular to supercharged internal combustion engines in which the exhaust gas turbine and the catalytic converter could otherwise be destroyed by excessively high exhaust gas temperatures.The mixture enrichment leads to high CO concentrations in the exhaust gas and the CO is disadvantageously not oxidized in the catalyst due to the oxygen deficiency prevailing in the exhaust gas. The catalytic converter does not operate more than 3-way catalytic converter in this operating range, since no stoichiometric mixture (lambda=1) is set. This jeopardizes the fulfilment of future approval requirements for motor vehicles.Present-day exhaust systems, in particular of turbo-charged Otto engines, typically have a turbine bypass, also called a waste gate, with a controllable exhaust gas mass flow through the waste gate. With this waste gate, the exhaust gas mass flow via the turbine and thus the turbine power and thus the desired boost pressure are adjusted. After the turbine and after the supply of the waste gate channel to the main flow of the exhaust gas, a catalytic converter (also called a catalytic converter close to the engine) is typically located as close as possible in order to ensure rapid heating after the internal combustion engine has been started. When the internal combustion engine is started, the waste gate is also opened far, in order to conduct as much hot exhaust gas as possible directly to the catalytic converter close to the engine for heating.In full load, at high powers of the internal combustion engine, high mass exhaust gas flows (approximately 30-45%) typically have to be diverted past the turbine via the waste gate. Since this exhaust gas is not expanded in the turbine, it is very hot. Thus, the average exhaust temperature after the mixing of turbine outlet exhaust mass flow and waste gate exhaust mass flow is higher than the turbine outlet temperature. It may exceed the maximum exhaust gas inlet temperature allowed for the catalyst. As a result, for example, the power of the internal combustion engine must be throttled, which is not desired.From DE 10 2017 218 837 A1 an exhaust system for an internal combustion engine is known which is connected to the internal combustion engine via an exhaust manifold. A first exhaust gas purification system and a second exhaust gas purification system are arranged behind it in the flow direction of the exhaust gas, wherein the first exhaust gas purification system can be bypassed by a shut-off element via a bypass. The shut-off element is arranged in the exhaust manifold.It is an object of the present invention to show a measure by which higher specific performance levels of the internal combustion engine of the type in question can be achieved without thermal damage to the catalytic converter close to the engine.This object is achieved for a generic internal combustion engine by the features in the characterizing part of claim 1.Advantageous refinements of the invention are described in the dependent claims.Due to the inventive configuration of the internal combustion engine with the exhaust system, significantly higher performance levels of the internal combustion engine can be achieved without thermal damage to the catalytic converter close to the engine.With the embodiment according to claims 2 and 3, the best possible exhaust gas purification is achieved.With the embodiment according to claim 4, the thermal protection of the first exhaust gas purification system is further significantly improved.In a further preferred embodiment according to claim 5, the first exhaust pipe can also be cooled. This can be effected, for example, with a coolant of the internal combustion engine, whereby the thermal protection of the second exhaust gas purification system is significantly improved again.The invention is explained in more detail below with reference to two figures. FIG. 1 shows a first exemplary embodiment, not belonging to the invention, for an internal combustion engine having an exhaust system. FIG. 2 shows a second exemplary embodiment, which forms part of the invention, for an internal combustion engine having an exhaust system.In the following, the same reference numerals apply to the same components in FIGS. 1 and 2.FIG. 1 schematically shows a first exemplary embodiment of an internal combustion engine 1 according to the invention having an exhaust system 3. An inflow of the fresh air is shown symbolically by an arrow. Subsequently, the fresh air is conducted through a not numbered intake line through a compressor 15 of an exhaust gas turbocharger 6 and cooled further downstream of the compressor 15 in a charge air cooler 16. Downstream of the charge air cooler 16, the fresh air flows through a throttle element 17, such as a throttle valve. After the throttle element 17, the fresh air enters an air collector 18, from which the fresh air is divided into four cylinders 2 in the present exemplary embodiment. In these four cylinders 2, the fresh air is mixed with fuel and burned.The exhaust gas flows out for each cylinder 2 via two gas exchange outlet valves, not numbered, which are shown symbolically by a circle in each case, first through an exhaust manifold 4 and further into the exhaust system 3. A transition from the exhaust manifold 4 to the exhaust system 3 is shown in dashed lines. Two cylinders 2 are combined into one cylinder group in accordance with a cylinder sequence of internal combustion engine 1. A typical firing order for a present four-cylinder internal combustion engine is, for example, cylinder 1, cylinder 3, cylinder 4, cylinder 2. in this firing order, cylinders 1 and 4 and cylinders 2 and 3 each form a cylinder group. Another possible firing order is cylinder 1, cylinder 2, cylinder 4, cylinder 3.Downstream of the exhaust manifold 4, the exhaust gas flows through a turbine housing of the exhaust gas turbocharger 6, in which a turbine wheel 5 is arranged. The turbine wheel 5 is coupled rotationally fixedly to the compressor wheel 15, which compresses the fresh air.Downstream of the exhaust gas turbocharger 6, the exhaust gas flows through a first exhaust gas purification system 7, a catalytic converter close to the engine, and in the present exemplary embodiment a third exhaust gas purification system 13 and leaves the exhaust system 3 in the present exemplary embodiment into the ambient air. An exit of the exhaust gas from the exhaust system 3 is shown symbolically by an arrow.Furthermore, a first exhaust pipe 8 is arranged on the exhaust manifold 4, in which first shut-off element 11 is arranged. The first shut-off element 11 is shown closed. When the shut-off element 11 is open, exhaust gas can flow through the first exhaust pipe 8 past the turbine wheel 5. For the best possible exhaust gas purification, a second exhaust gas purification device 12 is arranged in the first exhaust pipe 8.Furthermore, a second exhaust pipe 9, a so-called turbine bypass, is arranged on the exhaust manifold 4, in which a second shut-off element 10 is arranged. The second shut-off element 10 is also shown in a closed position. With the second shut-off element 10 open, hot exhaust gas can be conducted past the turbine wheel 5 in order to bring the first exhaust gas purification system 7 rapidly to its light-off temperature (light off) after a cold start of the internal combustion engine 1 in order to purify the exhaust gas as quickly as possible.When the internal combustion engine 1 is at full load, the second shut-off element 10 is closed and boost pressure is controlled via the first shut-off element 11, and when the internal combustion engine 1 is at partial load, the first shut-off element 11 is closed and boost pressure is controlled via the second shut-off element 10, just as the first exhaust gas purification system 7 is heated, so-called cat heating.In both cases, hot exhaust gas is thus guided past the turbine wheel 5 of the exhaust gas turbocharger 6, so that the first exhaust gas purification system 7, but also the turbine wheel 5 itself, is thermally protected. Because of the configuration according to the invention, significantly higher full load capacities can now be provided for the internal combustion engine 1, since the first exhaust gas purification system 7 and also the turbine wheel 5 are thermally protected by exhaust gas mass flow flowing past the turbine 5.Advantage: Temperature reduction upstream of the first exhaust gas purification system 7 at rated power gg. the admixing of the waste gate exhaust gas mass flow upstream of the first exhaust gas purification system 7.Advantage: cat heating is possible via the second exhaust pipe 9.Disadvantage: more expensive exhaust manifold 4, two wastegates (first and second exhaust pipes 8, 9).In further preferred embodiments, which are not shown in the figures, the first and / or the second exhaust pipe 8, 9 can also be cooled. This can be done, for example, with a coolant of the internal combustion engine.FIG. 2 shows a second exemplary embodiment of the internal combustion engine 1 according to the invention with the exhaust system 3; FIG. 2 differs from FIG. 1 in that the second and the first shut-off elements 10, 11 are arranged not in parallel but in series. That is, the first exhaust pipe 8 and the second exhaust pipe 9 have a single connection to the exhaust manifold 4, and the second shut-off element 10 is arranged upstream of the first shut-off element 11 in the flow direction. The second exhaust pipe 9 branches off from the first exhaust pipe 8 between the second shut-off element 10 and the first shut-off element 11.Advantage: Temperature reduction upstream of the first exhaust gas purification system 7 at rated power gg. the admixing of the waste gate exhaust gas mass flow upstream of the first exhaust gas purification system 7.Advantage: cat heating is possible via the second exhaust pipe 9.Disadvantage: the tightness of the first and second shut-off elements 11, 10 must be ensured.1. Internal combustion engine 2. cylinder 3. exhaust system 4. exhaust manifold 5. turbine wheel 6. exhaust turbocharger 7. first exhaust gas purification system 8. first exhaust pipe 9. second exhaust pipe 10. second shut-off element 11. first shut-off element 12. second exhaust gas purification system 13. third exhaust gas purification system 14. intake noise damper 15. compressor wheel 16. charge air cooler 17. throttle element 18. air collector

Claims

Internal combustion engine (1) having at least one cylinder (2) and having an exhaust system (3) which is arranged on an exhaust manifold (4) arranged on the internal combustion engine (1), wherein a turbine housing having a turbine wheel (5) of an exhaust gas turbocharger (6) is arranged in the exhaust system (3) and a first exhaust gas purification system (7) is arranged behind the turbine housing in the direction of flow of an exhaust gas, wherein a first exhaust pipe (8) in which a first shut-off element (11) is arranged branches off from the exhaust manifold (4) in a guiding manner and opens out again into the exhaust system (3) downstream of the first exhaust gas purification system (7), characterized in that the exhaust manifold (4) opens out again into the exhaust system (3) via a second exhaust pipe (9) in which a second shut-off element (10) is arranged, with the exhaust system (3) between the turbine wheel (5) and the first exhaust gas purification system (7) and with the first exhaust pipe (8) being connectable to the exhaust system (3) in the flow direction of the exhaust gas by the shut-off elements (10, 11) being arranged in series, the first exhaust pipe (8) and the second exhaust pipe (9) having a single connection to the exhaust manifold (4), the second shut-off element (10) being arranged upstream of the first shut-off element (11) in the flow direction and the second exhaust pipe (9) branching off from the first exhaust pipe (8) between the second shut-off element (10) and the first shut-off element (11) and opening into the exhaust system (3) between the turbine wheel (5) and the first exhaust gas purification system (7).Internal combustion engine (1) according to Patent Claim 1, characterized in that a second exhaust gas purification system (12) is arranged in the first exhaust pipe (8) downstream of the first shut-off element (11) in the direction of flow of the exhaust gas.Internal combustion engine (1) according to either of Patent Claims 1 and 2, characterized in that a third exhaust-gas purification system (13) is arranged in the exhaust system (3) downstream of an opening of the first exhaust pipe (8) in the direction of flow of the exhaust gas.Internal combustion engine (1) according to one of Patent Claims 1 to 3, characterized in that a cooling device is provided for the second exhaust pipe (9).Internal combustion engine (1) according to one of Patent Claims 1 to 4, characterized in that a cooling device is provided for the first exhaust pipe (8).

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