METHOD FOR METERING A REACTANT INTO AN EXHAUST GAS PATH OF AN INTERNAL COMBUSTION ENGINE, AND INTERNAL COMBUSTION ENGINE

Abstract

A method for metering a reactant into an exhaust gas path of an internal combustion engine, wherein the reactant is introduced into an area of the exhaust gas path in which pressure surges in the exhaust gas stream, generated by a charge exchange of the internal combustion engine, contribute to breakdown of droplets of the reactant, wherein a metering device for metering the reactant is activated at a variable metering frequency, depending on an operating point of the internal combustion engine.

Claims

1-10. (canceled)

11. A method for metering a reactant into an exhaust gas path of an internal combustion engine, comprising the steps of: introducing the reactant into a region of the exhaust gas path, in which region pressure shocks in an exhaust gas stream which are produced by a gas exchange of the internal combustion engine contribute to a disintegration of droplets of the reactant; and actuating a metering device for metering in the reactant at a variable metering frequency in a manner dependent on an operating point of the internal combustion engine.

12. The method according to claim 11, including actuating the metering device synchronously with respect to a defined stroke of the internal combustion engine.

13. The method according to claim 12, including actuating the metering device with a defined phase shift with respect to the defined stroke of the internal combustion engine.

14. The method according to claim 11, including metering the reactant into the exhaust gas path upstream of a turbine of an exhaust gas turbocharger.

15. The method according to claim 11, including introducing the reactant into an exhaust gas collecting region that adjoins at least one combustion chamber of the internal combustion engine.

16. The method according to claim 11, including actuating the metering device synchronously with an ignition sequence.

17. The method according to claim 16, including actuating the metering device with a defined stroke of at least one combustion chamber of the internal combustion engine.

18. The method according to claim 17, including actuating the metering device with a defined phase shift.

19. The method according to claim 11, including actuating the metering device synchronously with an exhaust stroke of at least one combustion chamber of the internal combustion engine.

20. The method according to claim 19, including actuating the metering device with a defined phase shift.

21. The method according to claim 11, including actuating the metering device in a pulse width modulated manner in order to set a metered quantity of reactant.

22. An internal combustion engine, comprising: at least one combustion chamber; an exhaust gas path; a metering device arranged in the exhaust gas path for metering a reactant into the exhaust gas path so that pressure shocks in an exhaust gas stream, which are produced by a gas exchange of the internal combustion engine, contribute to a disintegration of droplets of the reactant; and a control device set up to actuate the metering device at a variable metering frequency in a manner dependent on an operating point of the internal combustion engine.

23. The internal combustion engine according to claim 22, further comprising an exhaust gas turbocharger having a turbine, wherein the metering device is arranged upstream of the turbine.

24. The internal combustion engine according to claim 22, wherein the internal combustion engine is configured as a low speed engine, a medium speed engine or a fast speed engine.

Description

[0030] In the following text, the invention will be described in greater detail using the drawing, in which:

[0031] FIG. 1 shows a diagrammatic illustration of one exemplary embodiment of an internal combustion engine, and

[0032] FIG. 2 shows a diagrammatic illustration of one embodiment of the method.

[0033] FIG. 1 shows a diagrammatic illustration of one exemplary embodiment of an internal combustion engine 1. The internal combustion engine has at least one combustion chamber 3 (four combustion chambers here, of which only one is denoted by the designation 3 for improved clarity). Moreover, the internal combustion engine 1 has an exhaust gas path 5, in which a metering device 7 for metering a reactant into the exhaust gas path 5 is arranged.

[0034] The reactant is preferably a reducing agent, in particular for use as a reducing agent for the selective catalytic reduction of nitrogen oxides, particularly preferably a urea/water solution. As an alternative or in addition, it is also possible, however, that a reactant for another exhaust gas aftertreatment reaction is introduced into the exhaust gas path 5. It is possible, in particular, that a hydrocarbon or a hydrocarbon mixture for conversion at an oxidation catalytic converter is introduced as reactant.

[0035] Here, the metering device 7 is arranged in such a way that the reactant is introduced into a region of the exhaust gas path 5, in which region pressure shocks in the exhaust gas stream which are produced by way of a gas exchange of the internal combustion engine 1 contribute to a disintegration of droplets of the reactant. It is shown here, in particular, that the metering device 7 is arranged upstream of a turbine 9 of an exhaust gas turbocharger 11. In particular, the metering device 7 is arranged at an exhaust gas collecting region 13 which directly adjoins the at least one combustion chamber 3 of the internal combustion engine 1 and can be configured as an exhaust gas manifold. Here, it is preferably arranged centrally at the exhaust gas collecting region 13, with the result that the reactant can preferably be metered centrally into the exhaust gas collecting region 13.

[0036] The exhaust gas path 5 preferably has a catalytic converter 15 downstream of the exhaust gas turbocharger 11, at which catalytic converter 15 the reactant can be converted with the exhaust gas. The catalytic converter 15 is particularly preferably configured as an SCR catalytic converter.

[0037] The internal combustion engine 1 has a control device 17 which is set up to actuate the metering device at a variable metering frequency in a manner which is dependent on an operating point of the internal combustion engine 1. To this end, the control device 17 is preferably operatively connected firstly to an engine block 19 of the internal combustion engine 1, in particular to a rotational speed sensor (not shown) for detecting the rotational speed of said internal combustion engine 1, and to the metering device 7.

[0038] The control device 17 is set up, in particular, to actuate the metering device 7 in a manner which is dependent on the rotational speed, that is to say dependent on a rotational speed of the internal combustion engine 1. Furthermore, the control device 17 is preferably configured to actuate the metering device synchronously with a defined stroke of the internal combustion engine, in particular in a pulsed manner, preferably with a defined phase shift, preferably synchronously with an ignition sequence of the internal combustion engine 1, in particular with a defined stroke of at least one combustion chamber 3. The control device 17 is particularly preferably set up to actuate the metering device 7 synchronously with an exhaust stroke of at least one combustion chamber of the internal combustion engine.

[0039] The internal combustion engine 1 is preferably configured as a four stroke reciprocating piston engine, a sequence of four strokes of each combustion chamber 3 having an intake stroke, a compression stroke, a work stroke and an exhaust stroke. The corresponding method of operation of an internal combustion engine 1 is generally known, with the result that it will not be described in greater detail.

[0040] The metering of the reactant into a region which is close to the combustion chamber and, in particular, into a region, in which pressure shocks in the exhaust gas stream which are produced by way of a gas exchange of the internal combustion engine 1 contribute to a secondary disintegration of droplets of the reactant, necessitates metering in at an elevated exhaust gas temperature, with the result that a metering release can take place in a wider engine map range. At the same time, the pressure shocks aid a rapid and homogeneous distribution of the reactant in the exhaust gas, with the result that, in particular in comparison to an actuation of the metering device 7 at a constant frequency, a homogeneity of the distribution of the reactant in the exhaust gas stream becomes possible, which homogeneity is improved over the engine map of the internal combustion engine 1. Moreover, an arrangement of the metering device 7 upstream of the turbine 9 leads to said turbine 9 being used efficiently as a mixing device, with the result that possible further, additional mixing elements can be dispensed with or at least can be of smaller design. This in turn leads to a configuration of the exhaust gas path 5 which saves installation space, and to a reduction in the exhaust gas back pressure for the internal combustion engine 1, and therefore also to a reduction of the fuel consumption.

[0041] The control device 17 is preferably set up to actuate the metering device 7 in a pulse width modulated manner, in particular to set a quantity of reactant which is metered into the exhaust gas path 5.

[0042] FIG. 2 shows a diagrammatic illustration of one exemplary embodiment of the method. Here, FIG. 2a) illustrates a schematic, diagrammatic illustration of an ignition sequence of an internal combustion engine 1 having four combustion chambers which are labelled with the letters A, B, C, D. Here, in the diagram, an exhaust gas mass flow {dot over (m)}.sub.A in the exhaust gas path 5 is plotted against the time t, the individual mass flow distributions being assigned in each case to the outlet strokes of the different combustion chambers A, B, C, D.

[0043] FIG. 2b) schematically shows a diagram of a mass flow {dot over (m)}.sub.R of the reactant into the exhaust gas path 5 in a manner which is dependent on the time t, as results by way of actuation of the metering device 7. It is shown here that the actuation of the metering device 7 and therefore the mass flow of the reactant are synchronized here with the exhaust stroke of the combustion chamber B, preferably with a defined phase shift. This therefore results in a metering period T.sub.D which is dependent on the rotational speed, a metering frequency which is dependent on the rotational speed resulting accordingly.

[0044] It is shown overall that an improved distribution of a reactant in an exhaust gas stream can be realized over a wide engine map range of an internal combustion engine 1 by means of the method according to the invention and the internal combustion engine 1.