DE102022108338B3 - Internal combustion engine and associated method of operation - Google Patents

Abstract

The invention relates to a method for operating a supercharged internal combustion engine (1),
- in which, during a cold start of the internal combustion engine (1), the internal combustion engine (1) is operated with a sub-stoichiometric mixture to heat up an oxidation catalytic converter (11) of an exhaust system (6) of the internal combustion engine (1),
- In which an exhaust gas flow (7) of the internal combustion engine (1) secondary air (14) is supplied in such a way that a stoichiometric or over-stoichiometric mixture is formed in the exhaust gas flow (7).
The time required to heat up the oxidation catalytic converter (11) to its activation temperature can be reduced in that the stoichiometric or over-stoichiometric mixture in the exhaust gas flow (7) downstream of a turbine (9) of an exhaust gas turbocharger (8) of the internal combustion engine (1) and upstream of the oxidation catalytic converter (11 ) is externally ignited.

Description

The present invention relates to an internal combustion engine for a motor vehicle, in particular for a passenger car, having the features of the preamble of claim 1. The invention also relates to a method for operating such an internal combustion engine.

A generic internal combustion engine is from DE 697 22 260 T2 and from PAFFRATH, H., PANHANS, S.: Secondary air injection in: MTZ 12/2010, S 878-885 (2010) and has an engine block which has at least one cylinder bank with several combustion chambers. An exhaust system for discharging an exhaust flow from the combustion chambers is connected to the cylinder bank. The internal combustion engine is also equipped with an exhaust gas turbocharger, the turbine of which is arranged in the exhaust system and the exhaust gas flow can flow through it. An oxidation catalytic converter is arranged in the exhaust system downstream of the turbine. Furthermore, the internal combustion engine is equipped with a secondary air supply for supplying secondary air to the exhaust gas flow, which is connected to the exhaust system via at least one inlet point with respect to the exhaust gas flow upstream of the oxidation catalytic converter. With the help of an appropriately configured engine control, the internal combustion engine can be operated for a cold start to heat up the oxidation catalytic converter in such a way that a sub-stoichiometric mixture of fuel and primary air is formed in the combustion chambers, with the secondary air supply device supplying the exhaust gas flow with so much secondary air that there is a stoichiometric or super-stoichiometric mixture Mixture of unburned fuel and secondary air is formed, finally the mixture is ignited in the exhaust gas flow. In the known internal combustion engine, the mixture in the exhaust gas flow is ignited upstream of the turbine in order to be able to use the enthalpy of the heated exhaust gas flow in the turbine to increase the power of the internal combustion engine. In the known internal combustion engine, the mixture in the exhaust gas flow is ignited by self-ignition, for which purpose the sub-stoichiometric operation of the internal combustion engine must be carried out in a targeted manner such that high exhaust gas temperatures arise. When supplying secondary air, care must then be taken to ensure that a sufficiently high temperature for self-ignition is maintained in the mixture.

From the EP 1 637 706 A1 on the other hand, it is known to ignite a combustible mixture upstream of the turbine by means of an ignition device, for example in order to heat up a catalytic converter. A hydrogen-containing reformate gas is fed to the exhaust gas as fuel. A spark ignition is also from the DE 199 59 303 A1 and from the DE 101 62 738 A1 known.

More internal combustion engines, in which a catalyst is heated, are from DE 695 20 930 T2 , GB 2 428 465 A and GB 2 280 128A known.

From the DE 10 2018 114 681 A1 it is known to provide a common point of introduction which is arranged downstream of a turbine and upstream of a three-way catalytic converter.

From the DE 10 2016 119 306 A1 a mixing device for mixing two fluid streams is known.

In the course of ever more stringent emission laws, it is necessary to bring the exhaust aftertreatment of an internal combustion engine to an operating temperature required for this as quickly as possible. This applies in particular to a cold start of the internal combustion engine, in which the main components of the internal combustion engine are in the range of ambient temperature. Oxidation catalysts for converting hydrocarbons that are not or not completely burned are particularly important for exhaust gas aftertreatment. These must be heated to an activation or light-off temperature or light-off temperature for proper operation.

The present invention deals with the problem of specifying an improved or at least another embodiment for an internal combustion engine of the type described above or for a method for operating such an internal combustion engine, which is characterized in particular by increased efficiency.

According to the invention, this problem is solved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

The internal combustion engine according to the invention has a spark ignition device for igniting a combustible mixture in the exhaust gas flow, which is arranged downstream of the respective introduction point of the secondary air supply on the exhaust system with respect to the exhaust gas flow. In addition, the external ignition device, which is also referred to below as the ignition device, is arranged on the exhaust system downstream of the turbine. Furthermore, the ignition device is arranged upstream of the oxidation catalytic converter on the exhaust system. By using such a spark ignition device downstream of the turbine, the mixture in the exhaust gas flow between the turbine and the oxidation catalyst can be ignited so that the freed set heat is largely available for heating the catalyst. While when the mixture is ignited upstream of the turbine, part of the energy released in the process is absorbed by the turbine, when the mixture is ignited downstream of the turbine almost all of the released energy is available for heating the catalytic converter. In this respect, the heating of the catalytic converter can be carried out much faster, which improves the efficiency of the heating. The sooner the oxidation catalytic converter reaches its light-off temperature, the fewer pollutant emissions can escape into the environment when the internal combustion engine is in operation. Furthermore, the use of the external ignition device enables the internal combustion engine to be operated in such a way that the exhaust gas temperature is reduced, which reduces the pollutant emissions.

The exhaust system has a separate exhaust pipe for several or for all combustion chambers of the respective cylinder bank, which leads the exhaust gas flow from the respective combustion chamber to an exhaust gas collecting pipe, which is arranged upstream of the turbine with respect to the exhaust gas flow. Such exhaust manifolds are often also referred to as exhaust manifolds. As a rule, all combustion chambers of the respective cylinder bank are routed to a common exhaust manifold. However, split embodiments are also known, in which one half of the combustion chambers are fed to a first exhaust manifold, while the other half is then fed to a second exhaust manifold.

Appropriately, according to an embodiment not according to the invention, provision can now be made for the secondary air supply to have a separate introduction point for each combustion chamber of the respective cylinder bank, which is arranged on the respective exhaust pipe. This causes the secondary air to mix with the exhaust gas as early and as intensively as possible.

Alternatively, according to another embodiment not according to the invention, the secondary air supply for all combustion chambers of the respective cylinder bank can have a common introduction point, which is arranged downstream of the exhaust gas pipes on the exhaust gas collecting pipe or between the exhaust gas collecting pipe and the turbine. This measure simplifies the structure of the secondary air supply.

According to the invention, the secondary air supply for all combustion chambers of the respective cylinder bank has a common inlet point, which is arranged downstream of the turbine on the exhaust system. This measure makes it possible to avoid adverse interactions between the secondary air inlet and the turbine. In particular, the secondary air supply, if performed upstream of the turbine, can reduce the velocity and/or temperature of the exhaust gas flow and thus its enthalpy, which correspondingly reduces the performance of the turbine.

According to the invention, the exhaust system has a mixture formation chamber between the turbine and the oxidation catalytic converter, at which the inlet point and the ignition device are arranged. In this way, sufficient space is provided in the exhaust system for the secondary air to be mixed with the exhaust gas. The mixture formation chamber can be formed in an outlet area of the turbine and/or in an inlet area of the oxidation catalytic converter. It is also conceivable to form the mixture formation chamber in a separate pipe section that is arranged between the turbine and the oxidation catalytic converter. According to the invention, a mixer structure is arranged in the mixture formation chamber, which causes the secondary air to be thoroughly mixed with the exhaust gas. Such a mixer structure can be formed, for example, by flow guide elements and the like.

In another advantageous embodiment, a particle filter can be arranged in the exhaust system downstream of the oxidation catalytic converter with respect to the exhaust gas flow. In particular, this allows soot particles, which can arise during the oxidation reaction in the catalytic converter, to be filtered out of the exhaust gas flow.

In another embodiment, the engine may be configured as a compression ignition engine. Diesel is then the preferred fuel. In diesel engines, the rapid heating up of the oxidation catalytic converter is of particularly great importance, since modern, efficient diesel engines generate comparatively little waste heat, so that the oxidation catalytic converter would need a comparatively long time to reach its activation temperature without additional measures.

A method according to the invention for operating a supercharged internal combustion engine with an oxidation catalytic converter in the exhaust system assumes that during a cold start of the internal combustion engine, the internal combustion engine is operated with a substoichiometric mixture to heat up the oxidation catalytic converter. Secondary air is also supplied to an exhaust gas stream of the internal combustion engine, which is generated during sub-stoichiometric operation, in such a way that a stoichiometric or super-stoichiometric mixture is formed in the exhaust gas stream. Furthermore, this stoichiometric or over-stoichiometric mixture is spark-ignited in the exhaust gas flow downstream of the turbine of the exhaust gas turbocharger and upstream of the oxidation catalytic converter. Through this measure is quasi all of the heat that is generated during the exothermic conversion of the combustible mixture is available for heating the oxidation catalytic converter, so that this heating process can be carried out particularly quickly.

The secondary air is again supplied downstream of the turbine and is implemented collectively for all cylinders.

The internal combustion engine is usually designed as a piston engine, so that the combustion chambers are formed in cylinders in which pistons are arranged in a stroke-adjustable manner. In the case of a sub-stoichiometric mixture, there is an excess of fuel, the associated lambda value is less than 1 and is, for example, in a range from 0.6 to 0.9. Sub-stoichiometric operation is also referred to as rich operation or rich combustion. In a stoichiometric mixture, fuel and air or atmospheric oxygen are present in a ratio that is just sufficient to convert all of the fuel, with all of the oxygen being consumed. The associated lambda value is then equal to 1. In the case of a hyper-stoichiometric mixture, there is an excess of air or oxygen. In over-stoichiometric operation, all of the fuel is converted, leaving an excess of air or atmospheric oxygen. The associated lambda values are then greater than 1 and can be in a range from 1.1 to 1.5, for example.

In an embodiment of the internal combustion engine as an in-line engine, the engine block has only a single bank of cylinders, in which all the combustion chambers of the engine block are arranged. In an embodiment of the internal combustion engine as a V-engine, the engine block has two banks of cylinders, in each of which half of the combustion chambers are arranged. In the case of two banks of cylinders, two separate exhaust lines with two separate exhaust gas turbochargers can in principle also be provided. Expediently, the exhaust lines can also be brought together upstream of a common turbocharger. It is clear that the present invention can also be implemented accordingly in these embodiments.

Further important features and advantages of the invention result from the dependent claims, from the drawings and from the associated description of the figures with reference to the drawings.

It goes without saying that the features mentioned above and those still to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the invention. Components of a higher-level unit, such as a device, a device or an arrangement that are mentioned above and are to be mentioned below, which are designated separately, can form separate parts or components of this unit or be integral areas or sections of this unit, even if this shown differently in the drawings.

Preferred exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, with the same reference numbers referring to identical or similar or functionally identical components.

• 1 und 2 jeweils eine stark vereinfachte Prinzipdarstellung einer Brennkraftmaschine bei verschiedenen nicht erfindungsgemäßen Ausführungsformen,
• 3 eine stark vereinfachte Prinzipdarstellung der Brennkraftmaschine wie in den 1 und 2, jedoch bei einer erfindungsgemäßen Ausführungsform.

It shows, each schematically,

• 1 and 2 in each case a greatly simplified schematic representation of an internal combustion engine in various embodiments not according to the invention,
• 3 a greatly simplified schematic diagram of the internal combustion engine as in the 1 and 2 , but in an embodiment of the invention.

According to the 1 until 3 An internal combustion engine 1, which is suitable for use in a motor vehicle, preferably in a passenger car, has an engine block 2 which has at least one cylinder bank 3 containing a plurality of combustion chambers 4. Usually, the combustion chambers 4 are formed in cylinders 5, in which pistons (not shown here) are arranged in a stroke-adjustable manner. The internal combustion engine 1 is also equipped with an exhaust system 6 which is connected to the cylinder bank 3 and discharges the exhaust gases or an exhaust gas stream 7 from the combustion chambers 4 . The exhaust gas flow 7 is indicated by an arrow. The internal combustion engine 1 is supercharged and for this purpose has an exhaust gas turbocharger 8, the turbine 9 of which is arranged in the exhaust system 6 and the compressor 10 of which is arranged in a fresh air system, not shown here. The exhaust gas flow 7 can usually flow through the turbine 9 and thereby drives the compressor 10 .

An oxidation catalytic converter 11 is arranged in the exhaust system 6 in such a way that it is located downstream of the turbine 9 with respect to the exhaust gas flow 7 . Optionally, the exhaust system 6 can also be equipped with a particle filter 12 which is arranged downstream of the oxidation catalytic converter 11 with respect to the exhaust gas flow 7 .

Furthermore, the internal combustion engine 1 is equipped with a secondary air supply 13, which is only represented here by symbols that indicate the supply of secondary air 14 to the exhaust gas represent stream 7. It is clear that the secondary air supply 13 has a suitable conveying device for driving the secondary air 14, such as a pump or a fan. The supply of secondary air 14 to the exhaust gas flow 7 takes place via at least one inlet point 15, via which the secondary air supply 13 is connected to the exhaust system 6 upstream of the oxidation catalytic converter 11. In the present context, the relative location information “upstream” and “downstream” always refers to the flow of exhaust gas, i.e. to the flow direction of the exhaust gas in the exhaust system 6.

The internal combustion engine 1 is also equipped here with a spark ignition device 16 or ignition device 16 in the 1 until 3 is indicated in each case by a lightning symbol. It can be seen that the ignition device 16 is arranged on the exhaust system 6 downstream of the turbine 9 and upstream of the oxidation catalytic converter 11 in such a way that it can ignite a combustible mixture in the exhaust gas flow 7 . The ignition device 16 can be a spark plug or a glow plug or the like.

The internal combustion engine 1 is also equipped with an engine controller 17, which is used to control the internal combustion engine 1 and is coupled to controllable components of the internal combustion engine 1 via control lines (not shown here). In particular, engine control 17 is coupled to secondary air supply 13 and to ignition device 16 . In order to drive the secondary air 14, the secondary air supply 13 can be equipped in the usual way with a conveying device, not shown here, such as a pump or a blower.

The engine controller 17 is now configured in such a way that it operates the internal combustion engine 1 to heat up the oxidation catalytic converter 11 when the internal combustion engine 1 is started from cold. For this purpose, the engine controller 17 controls the internal combustion engine 1 or its components in such a way that a sub-stoichiometric mixture of fuel and primary air is formed and converted in the combustion chambers 4 . Primary air is the air that is fed to the combustion chambers with the fresh air system mentioned above. In the case of a substoichiometric mixture, this conversion or combustion in the combustion chambers 4 is incomplete, so that the exhaust gas still contains unburned fuel. With the help of the secondary air supply 13, the exhaust gas stream 7 is now supplied with so much secondary air 14 that a stoichiometric or even a super-stoichiometric mixture is formed in the exhaust gas stream 7. This mixture is then ignitable or combustible. The secondary air 14 can be branched off at a suitable point, preferably downstream of an air filter, in particular from the above-mentioned fresh air system.

The ignitable mixture in the exhaust gas flow 7 downstream of the turbine 9 and upstream of the oxidation catalytic converter 11 is ignited via the ignition device 16 . As a result, a lot of heat is generated directly at the inlet of the oxidation catalytic converter 11, as a result of which the oxidation catalytic converter 11 quickly reaches its activation temperature and can fulfill its catalytic exhaust gas purification function.

In all of the embodiments shown here, the exhaust system 6 has a separate exhaust pipe 18 and an exhaust manifold 19 for each combustion chamber 4 of the cylinder bank 3 . The exhaust gas pipes 18 lead the exhaust gas flow 7 from the respective combustion chamber 4 to the exhaust gas manifold 9 which then leads the exhaust gas flow 7 to the turbine 9 . The area of the exhaust manifold 19 connected to the exhaust pipes 18 is also regularly referred to as the exhaust manifold.

At the in 1 In the embodiment shown, the secondary air supply 13 has a separate introduction point 15 for each combustion chamber 4 of the cylinder bank 3 . The inlet points 15 are each arranged on one of the exhaust gas pipes 18 , expediently on an end remote from the exhaust gas collecting pipe 19 .

At the in 2 The embodiment shown has the secondary air supply 13 for all combustion chambers 4 of the cylinder bank 3 at a common inlet point 15 . This is now arranged downstream of the exhaust gas pipes 18 on the exhaust gas collecting pipe 19 . If the turbine 9 is not arranged at the outlet end of the exhaust manifold 19, the inlet point 15 is located at the outlet end of the exhaust manifold 19 or between the exhaust manifold 19 and the turbine 9. A section of the exhaust system 6 that leads from the common inlet point 15 to the turbine 9 , serves as a mixing section for mixing the exhaust gas with the secondary air 14.

At the in 3 The embodiment shown has the secondary air supply 13 as in 2 for all combustion chambers 4 a common discharge point 15, which deviates from 2 however, it is arranged on the exhaust system 6 downstream of the turbine 9 .

The exhaust system 6 can have a mixture formation chamber 20 between the turbine 9 and the oxidation catalytic converter 11, in which the secondary air 14 is supplied and in which the ignition device 16 is arranged. The mixture formation chamber 20 can be formed using a separate piece of pipe 21 which connects the turbine 9 to the oxidation catalytic converter 11 . Alternatively, the mixture formation chamber can be 20 in an outlet of the turbine 9 and/or in an inlet of the oxidation catalytic converter 11 .

The oxidation catalytic converter 11 comprises a tubular housing, not designated in any more detail here, in which a catalytically active catalytic converter body through which a flow can flow is arranged. The particle filter 12 comprises a tubular housing, not designated in any more detail, in which a particle filter body, which can be flowed through and retains particles, is arranged.

A mixer structure 22 can be arranged in the mixture formation chamber 20 , which supports thorough mixing of the secondary air 14 with the exhaust gas flow 7 . The mixer structure 22 can have at least one flow guide element.

In all of the embodiments, the internal combustion engine 1 can be configured as a spark-ignited internal combustion engine 1, ie as an Otto engine, or as a self-igniting internal combustion engine 1, ie as a diesel engine.

During normal operation of internal combustion engine 1, it is usually operated lean or at least stoichiometrically, so that the fuel supplied to combustion chambers 4 is largely converted. Remaining, unreacted fuel residues are converted in the oxidation catalytic converter 11 .

During a cold start of internal combustion engine 1, internal combustion engine 1 is operated with a substoichiometric mixture to heat up oxidation catalytic converter 11. The resulting sub-stoichiometric exhaust gas is then enriched with secondary air 14 to such an extent that a stoichiometric or even a super-stoichiometric mixture is produced in the exhaust gas flow 7 . This stoichiometric or over-stoichiometric mixture in the exhaust gas flow 7 is ignited with the ignition device 16 downstream of the turbine 9 and upstream of the oxidation catalytic converter 11 .

Claims (4)

Internal combustion engine (1) for a motor vehicle, in particular a passenger car, - with an engine block (2) which has at least one cylinder bank (3) with several combustion chambers (4), - with an exhaust system (6) connected to the cylinder bank (3) for discharging an exhaust gas flow (7) from the combustion chambers (4), - with an exhaust gas turbocharger (8), the turbine (9) of which is arranged in the exhaust system (6) and through which the exhaust gas flow (7) can flow, - with an oxidation catalytic converter (11), which is arranged downstream of the turbine (9) in the exhaust system (6) with respect to the exhaust gas flow (7), - with a secondary air supply (13) for supplying secondary air (14) to the exhaust gas flow (7), which has at least one inlet point (15) with respect to of the exhaust gas stream (7) is connected to the exhaust system (6) upstream of the oxidation catalytic converter (11), - with an engine controller (17) for controlling the internal combustion engine (1), which is designed and/or programmed in such a way that the engine controller (17) on a cold start The internal combustion engine (1) activates the internal combustion engine (1) to heat up the oxidation catalytic converter (11) in such a way --- that a substoichiometric mixture is formed in the combustion chambers (4), --- that with the secondary air supply (13) the exhaust gas flow (7) so much secondary air (14) is supplied that a stoichiometric or over-stoichiometric mixture is formed in it, --- that the mixture is ignited in the exhaust gas flow (7), - the exhaust system (6) for several or for all combustion chambers (4) of each cylinder bank (3) has a separate exhaust gas pipe (18) which leads the exhaust gas flow (7) from the respective combustion chamber (4) to an exhaust gas collecting pipe (19) which is arranged upstream of the turbine (9) with respect to the exhaust gas flow (7), characterized in that the internal combustion engine (1) has a spark ignition device (16) for igniting a combustible mixture in the exhaust gas flow (7), which with respect to the exhaust gas flow (7) downstream of the respective introduction point (15) and downstream of the turbo ne (9) is arranged on the exhaust system (6), - that the secondary air supply (13) for all combustion chambers (4) of the respective cylinder bank (3) has a common inlet point (15), which is downstream of the turbine (9) on the exhaust system (6) is arranged, - that the exhaust system (6) has a mixture formation chamber (20) between the turbine (9) and the oxidation catalytic converter (11), at which the inlet point (15) and the ignition device (16) are arranged, and - that the mixture formation chamber (20) contains a mixer structure (22) for mixing the secondary air (14) with the exhaust gas. Internal combustion engine (1) after claim 1 , characterized in that - with respect to the exhaust gas flow (7) downstream of the oxidation catalytic converter 11, a particle filter (12) is arranged in the exhaust system (6). Internal combustion engine (1) after claim 1 or 2 , characterized in that the internal combustion engine (1) is configured as a self-igniting internal combustion engine (1). Method for operating a supercharged internal combustion engine (1), - wherein the internal combustion engine (1) has: - an engine block (2) which has at least one cylinder bank (3) with a plurality of combustion chambers (4), - an exhaust system (6) connected to the cylinder bank (3) for discharging an exhaust gas stream (7) of the combustion chambers (4), -- an exhaust gas turbocharger (8), the turbine (9) of which is arranged in the exhaust system (6) and through which the exhaust gas flow (7) can flow, -- an oxidation catalytic converter (11), which with respect to the exhaust gas flow (7) is arranged downstream of the turbine (9) in the exhaust gas system (6), -- a secondary air supply (13) for supplying secondary air (14) to the exhaust gas flow (7), which has at least one inlet point (15) with respect to the exhaust gas flow (7) is connected to the exhaust system (6) upstream of the oxidation catalytic converter (11), - the exhaust system (6) having a separate exhaust pipe (18) for several or for all combustion chambers (4) of the respective cylinder bank (3), which the exhaust gas flow (7) from the respective combustion chamber (4) to an exhaust manifold (19) which is arranged upstream of the turbine (9) with respect to the exhaust gas flow (7), - the secondary air supply (13) for all combustion chambers (4) of the respective cylinder bank (3) having a common inlet point (15) which is downstream the turbine (9) is arranged on the exhaust system (6),- the exhaust system (6) having a mixture formation chamber (20) between the turbine (9) and the oxidation catalytic converter (11), which has a mixer structure (22) for mixing the secondary air (14) with the exhaust gas, - wherein in the method - during a cold start of the internal combustion engine (1) to heat up an oxidation catalytic converter (11) of the exhaust system (6) of the internal combustion engine (1), the internal combustion engine (1) is operated with a substoichiometric mixture is, - an exhaust gas flow (7) of the internal combustion engine (1) secondary air (14) is supplied in such a way that the exhaust gas flow (7) forms a stoichiometric or superstoichiometric mixture, - the stoichiometric or superst öchiometric mixture in the exhaust gas flow (7) downstream of a turbine (9) of an exhaust gas turbocharger (8) of the internal combustion engine (1) and upstream of the oxidation catalytic converter (11) is spark-ignited.

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