Applied-Ignition Internal Combustion Engine and Method for Operating the Internal Combustion Engine

Abstract

An applied-ignition internal combustion engine includes first and second combustion chambers, an exhaust-gas system with an exhaust-gas purification system is disposed at the first and second combustion chambers, and an exhaust-gas manifold. An exhaust gas from a combustion of a fuel/air mixture firstly flows through the exhaust-gas manifold and subsequently flows through the exhaust-gas purification system. A first section of the exhaust-gas system from the first combustion chamber to the exhaust-gas purification system is cooled more than a second section of the exhaust-gas system from the second combustion chamber to the exhaust-gas purification system. The first combustion chamber is operated with a lean fuel/air mixture, the second combustion chamber is operated with a rich fuel/air mixture, and an overall exhaust-gas lambda value at an inlet into the exhaust-gas purification system is stoichiometric.

Claims

1.-8. (canceled)

9. An applied-ignition internal combustion engine (1), comprising: a first combustion chamber (2); a second combustion chamber (3); an exhaust-gas system (4) disposed at the first and second combustion chambers, wherein an exhaust-gas purification system (6) is disposed in the exhaust-gas system (4); and an exhaust-gas manifold (5); wherein an exhaust gas from a combustion of a fuel/air mixture firstly flows through the exhaust-gas manifold (5) and subsequently flows through the exhaust-gas purification system (6) in the exhaust-gas system (4); wherein a first section of the exhaust-gas system (4) from the first combustion chamber (2) to the exhaust-gas purification system (6) is cooled more than a second section of the exhaust-gas system (4) from the second combustion chamber (3) to the exhaust-gas purification system (6); wherein the first combustion chamber (2) is operated with a lean (λ>1) fuel/air mixture, wherein the second combustion chamber (3) is operated with a rich (λ<1) fuel/air mixture, and wherein an overall exhaust-gas lambda value at an inlet into the exhaust-gas purification system (6) is stoichiometric (λ=1).

10. The applied-ignition internal combustion engine (1) according to claim 9 further comprising a turbine housing (7) of an exhaust-gas turbocharger, wherein the turbine housing (7) is disposed in the exhaust-gas system (4) between the exhaust-gas manifold (5) and the exhaust-gas purification system (6).

11. The applied-ignition internal combustion engine (1) according to claim 9, wherein the exhaust-gas manifold (5) is integrated at least in a section in a cylinder head of the applied-ignition internal combustion engine (1).

12. The applied-ignition internal combustion engine (1) according to claim 9, wherein the exhaust-gas manifold (5) is cooled.

13. The applied-ignition internal combustion engine (1) according to claim 12, wherein the exhaust-gas manifold (5) is liquid-cooled.

14. The applied-ignition internal combustion engine (1) according to claim 10, wherein the exhaust-gas turbocharger is a twin-scroll exhaust-gas turbocharger.

15. The applied-ignition internal combustion engine (1) according to claim 14, wherein the first section of the exhaust-gas system (4) opens into a first scroll (8) of the exhaust-gas turbocharger and wherein the second section of the exhaust-gas system (4) opens into a second scroll (9) of the exhaust-gas turbocharger.

16. A method for operating the applied-ignition internal combustion engine (1) according to claim 9, comprising the steps of: introducing the lean (λ>1) fuel/air mixture air into the first combustion chamber (2); igniting and combusting the lean fuel/air mixture in the first combustion chamber (2); discharging exhaust gas from the first combustion chamber (2) through the exhaust-gas system (4); introducing the rich (λ<1) fuel/air mixture air into the second combustion chamber (3); igniting and combusting the rich fuel/air mixture in the second combustion chamber (3); and discharging exhaust gas from the second combustion chamber through the exhaust-gas system (4).

17. The method according to claim 16, further comprising the steps of: adapting a first combustion center of gravity position in the first combustion chamber (2) until a first exhaust-gas temperature from the first combustion chamber (2) is at a first minimum; and adapting a second combustion center of gravity position in the second combustion chamber (3) until a second exhaust-gas temperature from the second combustion chamber is at a second minimum.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 schematically shows an internal combustion engine according to the invention.

[0033] FIG. 2 shows, in a diagram, the effect according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 schematically shows an internal combustion engine 1 according to the invention, which has for example four cylinders. Through an air manifold 10, the internal combustion engine draws in fresh air for its two first combustion chambers 2 and its two second combustion chambers 3. The combustion chambers, which also correspond to the individual cylinders, are symbolically illustrated by circles. Here, the mixture formation may be performed for example by direct injection into combustion chambers 2, 3 and/or into the air manifold 10. The fuel-air mixture is burned in the combustion chambers 2, 3 and is discharged through an exhaust-gas manifold 5 into an exhaust-gas system 4. In the present exemplary embodiment, the exhaust gases flow firstly through a turbine housing 7 of an exhaust-gas turbocharger (not illustrated in any more detail) and onward through an exhaust-gas purification system 6. The exhaust-gas purification system 6 may for example be a 3-way catalytic converter. The turbine housing 7 and the exhaust-gas purification system 6 are part of the exhaust-gas system 4.

[0035] In this present exemplary embodiment, the exhaust-gas manifold 5 is integrated into the cylinder head (cylinder-head-integrated manifold), though this need not be the case. Irrespective of whether or not the exhaust-gas manifold 6 is integrated in the cylinder head of the internal combustion engine 1, and also irrespective of whether it is a cast manifold or an exhaust-gas manifold 5 insulated by means of an air gap, a first section of the exhaust-gas system 4 is better cooled from the first combustion chambers 2 to the turbine 7 than from the second combustion chambers 3 to the turbine 7. In another exemplary embodiment, the turbine 7 may also be omitted, such that the exhaust-gas purification system 6 is the first component that is flowed through by the exhaust gas in the exhaust-gas system 4. Furthermore, in the present exemplary embodiment, the exhaust-gas system 4 is cooled, in particular liquid-cooled, within the cylinder head of the internal combustion engine 1.

[0036] Furthermore, in the present exemplary embodiment, the turbine 7 is of two-channel configuration, that is to say it is a so-called twin-scroll turbine, with a first scroll 8 and a second scroll 9. Single-channel turbines, so-called mono-scroll turbines, may also be used for the internal combustion engine 1 according to the invention. It is preferable for the first section of the exhaust-gas purification system 4 to open into the first scroll and for the second section of the exhaust-gas purification system 4 to open into the second scroll 9.

[0037] With the present applied-ignition internal combustion engine 1, a method for operation which has the following method steps is now possible:

[0038] introducing air and fuel into the first combustion chamber 2 with a lean ratio (λ>1),

[0039] igniting and combusting the fuel/air mixture in the first combustion chamber 2,

[0040] discharging the exhaust gas through the exhaust-gas system 4,

[0041] introducing air and fuel into the second combustion chamber 3 with a rich ratio (λ<1),

[0042] igniting and combusting the fuel/air mixture in the second combustion chamber 3,

[0043] discharging the exhaust gas through the exhaust-gas system 4.

[0044] A further lowering of the exhaust-gas temperature level is possible by means of the following method steps:

[0045] adapting a combustion center of gravity position in the first combustion chamber 2 until an exhaust-gas temperature from the first combustion chamber 2 is at a minimum,

[0046] adapting a combustion center of gravity position in the second combustion chamber 3 until an exhaust-gas temperature from the second combustion chamber 3 is at a minimum.

[0047] This adaptation of the combustion center of gravity position may be performed for example by means of an engine control unit which is provided with the data by measurement sensors or wherein the data are stored in a characteristic map.

[0048] The combustion center of gravity position indicates the crank angle position at which 50% of the fuel mixture is converted and is furthermore used as a measure for the efficiency of the combustion. Combustion which is optimum from an efficiency aspect for Otto internal combustion engines lies at a center of gravity position of approximately 8 degrees crank angle after ignition TDC.

[0049] FIG. 2 shows the effect of the method according to the invention in a diagram.

[0050] A temperature of the exhaust gas upstream of the exhaust-gas purification system 6 or upstream of the turbine 7 is plotted on a y axis, from 780° C. to 930° C. A cylinder-selective λ value is illustrated on an x axis, in a range from 0.9 to 1.08.

[0051] A first graph is labelled 11, and is representative of the exhaust-gas temperature from the first combustion chamber 2 upstream of the exhaust-gas purification system 6 in the case of variation of the lambda value from 0.9 to 1.08. A second graph is labelled 12, and is representative of the exhaust-gas temperature emerging from the second combustion chamber 3 upstream of the exhaust-gas purification system 6 in the case of variation of the lambda value from 0.9 to 1.08. The measurements that constitute the basis for the graphs are an adjustment of the lambda value uniformly for all cylinders of a multi-cylinder internal combustion engine in order to illustrate the effect according to the invention.

[0052] As can be seen in the diagram, a lowering of the exhaust-gas temperature in the rich range at approximately k=0.9 is approximately 60° colder than in the case of operation with λ1, whereas, in the case of a lean mixture at approximately λ=1.08, the lowering of the temperature is approximately 40° C. A further lowering in rich operation is possible in particular by means of an adaptation of the ignition angle.

LIST OF REFERENCE CHARACTERS

[0053] 1 Internal combustion engine [0054] 2 First combustion chamber [0055] 3 Second combustion chamber [0056] 4 Exhaust-gas system [0057] 5 Exhaust-gas manifold [0058] 6 Exhaust-gas purification system [0059] 7 Turbine housing [0060] 8 First scroll [0061] 9 Second scroll [0062] 10 Air manifold [0063] 11 Exhaust-gas temperature, first combustion chamber [0064] 12 Exhaust-gas temperature, second combustion chamber