DE102019108938A1 - Exhaust system with the possibility of thermal conditioning, method for aftertreatment of an exhaust stream, motor vehicle - Google Patents

Abstract

An exhaust system (100) for removing and cleaning an exhaust gas stream of combustion exhaust gases from an internal combustion engine (1), in particular an internal combustion engine (1) of a motor vehicle (200), has an exhaust manifold (2) for receiving the combustion exhaust gases from the internal combustion engine (1), - a turbine (3), - a first line section (A) connecting the exhaust manifold (2) to the turbine (3), - a first catalytic converter (4), - a first conduit section (3) connecting the turbine (3) to the first catalytic converter (4) second line section (B), - a second catalytic converter (5), a third line section (C) connecting the first catalytic converter (4) to the second catalytic converter (5), - a first line section (A) for fluid power bridging of the turbine (3 ) with the second line section (B) connecting first bypass line (10) and a second line section (B) for fluid technology bridging of the first catalytic converter (4) with the third line section (C) second bypass line (20) proposed. A method and a motor vehicle (200) are also proposed.

Description

The present invention relates to an exhaust system for removing and cleaning an exhaust gas stream of combustion exhaust gases from an internal combustion engine, in particular an internal combustion engine of a motor vehicle, a method for aftertreatment of an exhaust gas stream, and a motor vehicle with an exhaust system.

To reduce pollutant emissions in internal combustion engines, the three-way catalytic converter in gasoline engines and the oxidation catalytic converter in conjunction with SCR exhaust gas aftertreatment in diesel engines represent the state of the art. In gasoline engines, the so-called 3-way reaction simultaneously oxidizes HC and CO to CO2 and H2O and the reduction of NOx to N2 + 02 takes place. In diesel systems, due to the considerable excess of air in the oxidation catalytic converter, there is almost only a two-way reaction, namely the oxidation of HC and CO to CO2 and H2O. The NOx reduction, on the other hand, essentially takes place in the SCR catalytic converter with the addition of a reducing agent, for example aqueous urea solution.

The three-way or oxidation catalytic converters are basically constructed identically. They consist of ceramic carrier matrices with a highly porous ceramic coating. The chemical catalysts platinum, palladium and rhodium are arranged in this coating. A minimum operating temperature of the catalysts is necessary for the reaction to take place. One speaks here of the so-called light-off temperature, which is around 300 ° C. Below this temperature the reaction does not take place or takes place incompletely. The catalysts are usually heated directly by means of the combustion exhaust gas. This means that in the first few seconds after starting the engine before the light-off temperature is reached, some of the combustion exhaust gases leave the catalytic converter without being converted. More than 80% of the pollutants in the test cycle arise immediately after the engine has started before reaching the light-off temperature.

At the same time, excessive thermal stress on the catalytic converter from hot combustion exhaust gases must be avoided. Excessive thermal loads lead to increased wear on the catalytic converter and, in the worst case, to its destruction. The catalytic converter also throttles the exhaust gas flow, which leads to a loss of performance.

It is therefore an object of the present invention to provide an exhaust system for preconditioning an exhaust system for the removal and cleaning of combustion exhaust gases from an internal combustion engine, in particular an internal combustion engine of a motor vehicle, which does not have the disadvantages of the prior art described above and has a simple and robust option offers to operate a catalytic converter of the exhaust system in an optimal temperature range.

Another object of the invention is to introduce a portion of uncleaned exhaust gas into a second catalytic converter in order to increase a catalytic exhaust gas cleaning effect (conversion rate) of the second catalytic converter based on an increased residual oxygen proportion and further raw exhaust gas components.

This object is achieved by an exhaust system for removing and cleaning combustion exhaust gases from an internal combustion engine, in particular an internal combustion engine of a motor vehicle, having an exhaust manifold for receiving the combustion exhaust gases from the internal combustion engine, a turbine, a first line section connecting the exhaust manifold to the turbine, a first catalytic converter, a a second line section connecting the turbine to the first catalyst, a second catalyst, a third line section connecting the first catalyst to the second catalyst, a first bypass line connecting the first line section for fluidly bridging the turbine with the second line section and a second line section for fluid-technical bridging of the first catalyst with the third line section connecting second bypass line. This advantageously makes it possible, depending on the temperature of the first catalyst, to guide an exhaust gas flow past the turbine and thus not to cool the exhaust gas flow and / or to lead the exhaust gas flow past the first catalyst and thus not to heat the first catalyst any further. In the context of the present invention, connecting means enabling fluid-technical conduction. For the purposes of the present invention, fluid technology means the technical treatment of fluids, that is to say relating to gases and liquids.

It is conceivable that when the temperature of the first catalytic converter is below its light-off temperature, at least part of an exhaust gas flow of the combustion exhaust gas is passed through the first bypass line past the turbine. The hot part of the exhaust gas flow that bypasses the turbine is not cooled by the turbine and can thus heat the first catalytic converter to its light-off temperature more quickly. It is also conceivable that when the temperature of the first catalytic converter is in an optimal range, the exhaust gas flow is not diverted past the turbine. It is also conceivable that if the temperature of the first catalytic converter is too high, at least part of the exhaust gas flow through the second bypass line on the first Catalyst is passed by. The thermal load on the first catalytic converter is thus reduced. It is nevertheless advantageously possible for the exhaust gas flow to be passed through the turbine and for the turbine to be driven by the exhaust gas flow despite the reduction in the thermal load on the first catalytic converter.

Advantageous refinements and developments of the invention can be found in the subclaims and the description with reference to the drawings.

According to a preferred embodiment of the invention it is provided that the first bypass line has a first bypass valve for closing the first bypass line, the first bypass valve preferably being adjustable in the degree of opening of the first bypass valve, wherein the first bypass valve is particularly preferably a first throttle valve. This advantageously enables the first bypass line to be switched on and off. If the degree of opening of the bypass valve is adjustable, it can also advantageously serve as an external wastegate of the turbine.

According to a preferred embodiment of the invention it is provided that the second bypass line has a second bypass valve for closing the second bypass line, the second bypass valve preferably being adjustable in the degree of opening of the second bypass valve, wherein the second bypass valve is particularly preferably a second throttle valve. This advantageously enables the second bypass line to be switched on and off independently of the first bypass valve. If the degree of opening of the second bypass valve is adjustable, it can also advantageously serve as an external wastegate of the first catalytic converter.

According to a preferred embodiment of the invention it is provided that the turbine is an exhaust gas turbocharger. This advantageously makes it possible for the first bypass valve to be used as an external wastegate of the exhaust gas turbocharger, with combustion exhaust gases from the internal combustion engine being conducted past the exhaust gas turbocharger through the first bypass line when the first bypass valve is open and with a degree of opening of the first bypass valve a boost pressure generated by the exhaust gas turbocharger is regulated. This enables the exhaust system to operate effectively when driving with the internal combustion engine. It is conceivable that a turbocharger valve is arranged upstream of the exhaust gas turbocharger between the first bypass line and the turbine, so that when the turbocharger valve is closed, the combustion exhaust gases flow exclusively through the first bypass line and not through the exhaust gas turbocharger.

According to a preferred embodiment of the invention it is provided that the second bypass line has an exhaust gas cooling system. This makes it possible to cool down the exhaust gas flow in such a way that the second catalytic converter is not overheated and thereby damaged.

According to a preferred embodiment of the invention it is provided that the exhaust gas cooling has air cooling. Air cooling is light, robust, can be installed with little effort and is inexpensive.

According to a preferred embodiment of the invention it is provided that the exhaust gas cooling has water cooling. Water cooling can work more efficiently than air cooling. It is also conceivable that the exhaust gas cooling has both air cooling and water cooling.

According to a preferred embodiment of the invention, it is provided that the exhaust system has a temperature sensor, the temperature sensor preferably being arranged on the first catalytic converter, the temperature sensor preferably being designed to detect the temperature of the first catalytic converter. The temperature sensor can be used to control the first bypass valve and / or the second bypass valve using temperature data relating to the operating temperature of the first catalytic converter.

Another object of the invention for solving the problem formulated at the beginning is a method for the aftertreatment of an exhaust gas stream with an exhaust system according to one of the preceding claims, wherein the exhaust gas stream is passed from the internal combustion engine via the exhaust manifold into the first line section, at least parts of the exhaust gas stream from the first Line section through the turbine into the second line section, from the second line section through the first catalyst into the third line section and from the third line section into the second catalyst when a temperature of the first catalyst is above a minimum temperature and below a maximum temperature, at least parts of the exhaust gas flow from the first line section through the first bypass line past the turbine into the second line section, from the second line section through the first catalyst into the third line section and from the third line section into the second catalyst when the temperature of the first catalyst is below the minimum temperature and at least parts of the exhaust gas flow from the first line section through the turbine in the second line section, from the second line section through the second bypass line past the first catalyst into the third line section and from the third line section into the second catalyst when the temperature is reached temperature of the first catalyst is above the maximum temperature. This advantageously makes it possible, depending on the temperature of the first catalyst, to guide an exhaust gas flow past the turbine and thus not to cool the exhaust gas flow and / or to lead the exhaust gas flow past the first catalyst and thus not to heat the first catalyst any further.

It is conceivable to drive the vehicle in a purely naturally aspirated engine mode in which the first bypass valve is fully open and the combustion exhaust gas is led past the turbine. This dethrottles the path of the combustion exhaust gases. It is conceivable that a turbocharger valve is arranged in front of the turbine, so that when the turbocharger valve is closed, the combustion exhaust gases flow exclusively through the first bypass line and not through the turbine. It is also conceivable that for driving in pure naturally aspirated engine operation, in addition or as an alternative to the first complete opening of the first bypass valve, the second bypass valve is fully open and the combustion exhaust gas is led past the first catalytic converter. This further dethrottles the path of the combustion exhaust gases. It is conceivable that a catalytic converter valve is arranged upstream of the first catalytic converter, so that when the catalytic converter valve is closed, the combustion exhaust gases flow exclusively through the second bypass line and not through the first catalytic converter.

According to a preferred embodiment of the invention it is provided that a part of the exhaust gas flow which is passed through the second bypass line is cooled by the exhaust gas cooling. This makes it possible to cool down the exhaust gas flow in such a way that the second catalytic converter is not overheated and thereby damaged.

According to a preferred embodiment of the invention it is provided that at full load of the internal combustion engine at least parts of the exhaust gas flow from the second line section through the second bypass line past the first catalytic converter into the third line section and from the third line section into the second catalytic converter. In this way, the path of the combustion exhaust gases continues to be de-throttled and thermal relief of the first catalytic converter is achieved. It is preferably provided that the catalyst valve is closed for this purpose.

According to a preferred embodiment of the invention it is provided that the temperature is measured with the temperature sensor. This advantageously enables the first bypass valve and / or the second bypass valve to be controlled on the basis of temperature data relating to the operating temperature of the first catalytic converter. Alternatively, the temperature of the first catalytic converter can be calculated in a control unit using a computer model.

It is also possible for the second catalytic converter to be monitored by a temperature sensor or a temperature calculation model and for the positions of the bypass lines and the combustion control to be set as a function of both temperatures.

Another object of the invention for solving the object formulated at the beginning is a motor vehicle, having an internal combustion engine and an exhaust system according to the invention.

All details, features and advantages disclosed above relate to the exhaust system according to the invention, the method according to the invention and the motor vehicle according to the invention.

• 1(a) und 1(b) illustrieren jeweils schematisch die Abgasanlage gemäß einer beispielhaften Ausführungsform der vorliegenden Erfindung.
• 2 illustriert schematisch das Kraftfahrzeug gemäß einer beispielhaften Ausführungsform der vorliegenden Erfindung.

Further details, features and advantages of the invention emerge from the drawings and from the following description of preferred embodiments with reference to the drawings. The drawings merely illustrate exemplary embodiments of the invention, which do not restrict the concept of the invention.

• 1 (a) and 1 (b) each schematically illustrate the exhaust system according to an exemplary embodiment of the present invention.
• 2 schematically illustrates the motor vehicle according to an exemplary embodiment of the present invention.

In the various figures, the same parts are always provided with the same reference numerals and are therefore usually only named or mentioned once.

In 1 (a) is schematic of the exhaust system 100 illustrated in accordance with an exemplary embodiment of the present invention. From the internal combustion engine 1 the combustion exhaust gases are in an exhaust gas stream through the exhaust manifold 2 in the direction of the first line section A. directed. Between the first line section A. and the second line section B. is these two line sections A. , B. connecting the turbine 3 , here an exhaust gas turbocharger, arranged. The exhaust system also has the first line section A. with the second line section B. connecting and the turbine 3 bridging the first bypass line 10 with the first bypass valve 11 on. Between the second line section B. and the third line section C. is these two line sections B. , C. connecting the first catalyst 4th arranged. The exhaust system also has the second line section B. with the third line section C. connecting and the first catalyst 4th bridging the second bypass line 20th with the second bypass valve 21st on. On the second bypass line 20th is still the exhaust gas cooling 22nd , here in the form of air cooling 22nd with a heat exchanger and water cooling 22 ' , arranged. On the first catalyst 4th opposite end of the third line section C. is the second catalyst 5 arranged.

The temperature sensor 6th in the first catalyst 4th measures the temperature of the first catalyst 4th . Is the temperature below the lightoff temperature of the first catalyst 4th so becomes the first bypass valve 11 open. The hot exhaust gas flow from the internal combustion engine 1 can now through the first bypass line 10 on the turbine 3 flow past without being cooled down and so the first catalyst 4th heat quickly to a temperature above the lightoff temperature. Has the first catalyst 4th reaches its optimum operating temperature, the first bypass valve closes 11 and the exhaust gas stream flows through the turbine. The first bypass valve 11 here is a throttle valve and the degree of its opening can be regulated. It is not only used to heat the first catalytic converter 4th , but is also an external waste gate of the exhaust gas turbocharger, through which the boost pressure of the exhaust gas turbocharger can be regulated. The temperature of the first catalyst increases 4th too much and reaches a maximum temperature, the second bypass valve will 21st open. The exhaust gas stream now flows through the first catalytic converter 4th pass through the second bypass line 20th in the third line section C. to the second catalyst 5 . This relieves the thermal load on the first catalytic converter 4th reached. When flowing through the second bypass line 20th the exhaust gas flow is cooled down by the exhaust gas cooling system to such an extent that the thermal load on the second catalytic converter 5 is reduced to sub-critical areas.

The first bypass line 10 and the second bypass line also fulfill the function of dethrottling the path of the exhaust gas flow. So it is possible to use the first bypass valve 11 and / or the second bypass valve 21st to open and the internal combustion engine 1 so to drive in a pure naturally aspirated engine operation. However, the second bypass valve is also conceivable 21st at full load of the combustion engine 1 to open and so in addition to the thermal relief of the first catalyst 4th to dethrottle the path of the exhaust gas flow and thus effectively provide more driving power.

In 1 (b) is schematic of the exhaust system 100 illustrated in accordance with another exemplary embodiment of the present invention. In contrast to the in 1 (a) The embodiment shown here has the second bypass line 20th no second bypass valve 21st out. The second bypass line 20th is designed as passive bridging. This not only saves components, it also reduces the weight, flow behavior and susceptibility of the exhaust system to failure 100 improved.

2 schematically illustrates the motor vehicle 200 according to an exemplary embodiment of the present invention. The car 200 instructs the internal combustion engine 1 and the exhaust system 100 according to an exemplary embodiment of the present invention.

List of reference symbols

1

Internal combustion engine

2

Exhaust manifold

3

turbine

4th

first catalyst

5

second catalyst

6th

Temperature sensor

10

first bypass line

11

first bypass valve

20th

second bypass line

21st

second bypass valve

22, 22 '

Exhaust gas cooling

100

Exhaust system

200

Motor vehicle

A.

first line section

B.

second line section

C.

third line section

Claims (13)

Exhaust system (100) for removing and cleaning an exhaust stream of combustion exhaust gases from an internal combustion engine (1), in particular an internal combustion engine (1) of a motor vehicle (200), comprising - an exhaust manifold (2) for receiving the combustion exhaust gases from the internal combustion engine (1), - a turbine (3), - a first line section (A) connecting the exhaust manifold (2) to the turbine (3), - a first catalytic converter (4), - a second line section (3) connecting the turbine (3) to the first catalytic converter (4) ( B), - a second catalyst (5), a third line section (C) connecting the first catalyst (4) to the second catalyst (5), a first bypass line (10) connecting the first line section (A) for fluid-technical bridging of the turbine (3) with the second line section (B) and a second line section (B) for fluid-technical bridging of the first catalytic converter (4) with the third line section (C) connecting second bypass line (20). Exhaust system (100) Claim 1 , wherein the first bypass line (10) has a first bypass valve (11) for closing the first bypass line (10), the first bypass valve (11) preferably in the degree of opening of the first bypass valve (11) is adjustable, the first bypass valve (11) being particularly preferably a first throttle valve. Exhaust system (100) according to one of the preceding claims, wherein the second bypass line (20) has a second bypass valve (21) for closing the second bypass line (20), the second bypass valve (21) preferably in the degree of opening of the second bypass valve (21) can be adjusted, the second bypass valve (21) particularly preferably being a second throttle valve. Exhaust system (100) according to one of the preceding claims, wherein the turbine (3) is an exhaust gas turbocharger. Exhaust system (100) according to one of the preceding claims, wherein the second bypass line (20) has an exhaust gas cooling system (22). Exhaust system (100) Claim 5 , wherein the exhaust gas cooling (22) comprises air cooling. Exhaust system (100) Claim 5 or 6th , wherein the exhaust gas cooling (22) comprises water cooling. Exhaust system (100) according to one of the preceding claims, wherein the exhaust system (100) has a temperature sensor (6), wherein the temperature sensor (6) is preferably arranged on the first catalytic converter (4), the temperature sensor (6) preferably for detecting the temperature of the first catalyst (4) is formed. Method for aftertreatment of an exhaust gas flow with an exhaust system (100) according to one of the preceding claims, wherein the exhaust gas flow from the internal combustion engine (1) is passed through the exhaust manifold (2) into the first line section (A), at least parts of the exhaust gas flow from the first line section (A) through the turbine (3) into the second line section (B), from the second line section (B) through the first catalytic converter (4) into the third line section (C) and from the third line section (C) into the second catalytic converter (5) are passed when a temperature of the first catalyst (4) is above a minimum temperature and below a maximum temperature, at least parts of the exhaust gas flow from the first line section (A) through the first bypass line (10) to the turbine (3 ) past into the second line section (B), from the second line section (B) through the first catalyst (4) into the third line section (C) and from the third th line section (C) are passed into the second catalyst (5) when the temperature of the first catalyst (4) is below the minimum temperature and at least parts of the exhaust gas flow from the first line section (A) through the turbine (3) into the second line section (B), from the second line section (B) through the second bypass line (20) past the first catalytic converter (4) into the third line section (C) and from the third line section (C) into the second catalytic converter (5) are passed when the temperature of the first catalyst (4) is above the maximum temperature. Procedure according to Claim 9 wherein a part of the exhaust gas flow passed through the second bypass line (20) is cooled by the exhaust gas cooling system (22). Method according to one of the Claims 9 or 10 , with at full load of the internal combustion engine (1) at least parts of the exhaust gas flow from the second line section (B) through the second bypass line (20) past the first catalytic converter (4) into the third line section (C) and from the third line section ( C) are passed into the second catalyst (5). Method according to one of the Claims 9 to 11 , the temperature being measured with the temperature sensor (6). Motor vehicle (200), having an internal combustion engine (1) and an exhaust system (100) according to one of the Claims 1 to 8th .

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