INTERNAL COMBUSTION ENGINE WITH EXHAUST GAS AFTERTREATMENT AND CONTROL OF THE NITROGEN OXIDE EMISSIONS

Abstract

An internal combustion engine, with an engine regulating device and an exhaust gas aftertreatment device with an SCR catalytic converter for the reduction of at least one NO.sub.x component, and with a catalytic converter regulating device, wherein the engine regulating device is prescribed a target value for an NO.sub.x mean value of the NO.sub.x component of the exhaust gases, which mean value results at an outlet point of the exhaust gas aftertreatment device in relation to a predefinable time period, and the engine regulating device is configured at least in one operating mode to continuously calculate an NO.sub.x reference value for the catalytic converter regulating device with consideration of No.sub.x components which have already been emitted and the predefined target value, which reference value is selected in such a way that the predefined target value results at the outlet point of the exhaust gas aftertreatment device at the end of the predefinable time period when the calculated NO.sub.x reference value of the catalytic converter regulating device is fed as NO.sub.x setpoint value to the regulating means.

Claims

1-20. (canceled)

21. A system, comprising: a controller configured to: set a target value, for an emissions average value of an exhaust emissions portion of an exhaust gas produced by one or more piston-cylinder assemblies of an internal combustion engine, to achieve in relation to a period of time at a discharge from an exhaust gas aftertreatment apparatus having at least one catalytic converter; and calculate an emissions reference value at least based on an already emitted amount of the exhaust emissions portion and the target value, wherein the emissions reference value is selected to achieve the target value by an end of the period of time.

22. The system of claim 21, wherein the exhaust emissions portion at least relates to NH.sub.3 associated with an amount of a reducing agent.

23. The system of claim 21, wherein the at least one catalytic converter comprises an ammonia slip catalytic converter (ASC).

24. The system of claim 21, wherein the target value and the period of time are predetermined or predeterminable.

25. The system of claim 21, wherein the controller is configured to calculate the emissions reference value continuously or repeatedly at least in one operating mode.

26. The system of claim 21, wherein the controller comprises an engine controller configured to control operation of the internal combustion engine, wherein the engine controller is configured to provide the emissions reference value to a catalytic converter controller of the exhaust gas aftertreatment apparatus as an emissions setpoint value.

27. The system of claim 26, wherein the controller is a common controller having the engine controller and the catalytic converter controller.

28. The system of claim 21, wherein the controller is configured to, at least after an expiration of a starting time of the internal combustion engine, to control a current operating point of the internal combustion engine in dependence on a conversion rate of the exhaust gas aftertreatment apparatus.

29. The system of claim 21, wherein the controller is configured to move a current operating point of the internal combustion engine away from a first operating point to a transient operating point with a lower amount of the exhaust emissions portion if the at least one catalytic converter of the exhaust gas aftertreatment apparatus reduces less of the exhaust emissions portion than is required to attain the emissions reference value at the discharge of the exhaust gas aftertreatment apparatus.

30. The system of claim 21, wherein the controller is configured to, during a starting time of the internal combustion engine, reduce the exhaust emissions portion by at least setting a power ramp for the internal combustion engine in a first time portion, after a power output reaches a minimum power output, until the power output reaches a limit value with a first lesser gradient and in a second time portion until the power output reaches a nominal power output of the internal combustion engine with a second greater gradient, wherein the second greater gradient is calculated in dependence on a remaining time to reach the starting time.

31. The system of claim 21, wherein the controller is configured to, during a starting time of the internal combustion engine, reduce the exhaust emissions portion by at least increasing an air excess number (λ) of an air-fuel mixture for combustion in the internal combustion engine from a lower first value (λ.sub.1) to a higher second value (λ.sub.2).

32. The system of claim 21, wherein the controller is configured to control the exhaust emissions portion to control a charging pressure of the internal combustion engine to provide a desired air excess number (λ).

33. The system of claim 21, wherein the controller is configured not to exceed a limit value dependent on a mode of operation for a momentary mass flow or for a momentary concentration of the exhaust emissions portion of the exhaust gas in an exhaust manifold.

34. The system of claim 21, comprising the internal combustion engine.

35. The system of claim 34, comprising an electric generator coupled to the internal combustion engine.

36. A method, comprising: setting, a target value, for an emissions average value of an exhaust emissions portion of an exhaust gas produced by one or more piston-cylinder assemblies of an internal combustion engine, to achieve in relation to a period of time at a discharge from an exhaust gas aftertreatment apparatus having at least one catalytic converter; and calculating an emissions reference value at least based on an already emitted amount of the exhaust emissions portion and the target value, wherein the emissions reference value is selected to achieve the target value by an end of the period of time; wherein setting and calculating are performed via a controller.

37. The method of claim 36, wherein the exhaust emissions portion comprises NO.sub.x emissions.

38. The method of claim 36, wherein the calculating comprises calculating the emissions reference value continuously or repeatedly at least in one operating mode.

39. The method of claim 36, comprising providing the emissions reference value to a catalytic converter controller of the exhaust gas aftertreatment apparatus as an emissions setpoint value.

40. A system, comprising: an internal combustion engine configured to produce an exhaust gas having an exhaust emissions portion; an exhaust gas aftertreatment apparatus configured to treat the exhaust gas to lower an amount of the exhaust emissions portion; and a controller configured to: set a target value, for an emissions average value of the exhaust emissions portion, to achieve in relation to a period of time at a discharge from the exhaust gas aftertreatment apparatus; and calculate an emissions reference value at least based on an already emitted amount of the exhaust emissions portion and the target value, wherein the emissions reference value is selected to achieve the target value by an end of the period of time.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Embodiments of the invention are discussed with reference to the Figures in which:

[0082] FIG. 1 shows an internal combustion engine according to the invention,

[0083] FIG. 2 shows a view of the state of the internal combustion engine in relation to time on the basis of selected parameters,

[0084] FIG. 3 shows a further view of the state of the internal combustion engine in relation to time on the basis of selected parameters with adaptation of a load ramp,

[0085] FIG. 4 shows an open-loop and closed-loop control movement of the operating point of the engine block in a combustion diagram,

[0086] FIG. 5 shows a view of the state of the internal combustion engine in relation to time on the basis of selected parameters when using the open-loop and closed-loop control strategy shown in FIG. 4, and

[0087] FIG. 6 shows a genset according to the invention.

DETAILED DESCRIPTION

[0088] The moments in time identified by the same references in FIGS. 1, 3 and 5 are identical.

[0089] FIG. 1 diagrammatically shows an embodiment of an internal combustion engine 1 according to the invention with the following proportions or components: [0090] 2 piston-cylinder units [0091] 3 engine closed-loop control unit [0092] 4 SCR catalytic converter [0093] 5 engine block [0094] 6 catalytic converter closed-loop control device [0095] 7 discharge from the exhaust gas aftertreatment apparatus [0096] 8 electric generator of a genset including the internal combustion engine [0097] 9 turbocharger (optional) [0098] 10 wastegate (optional) [0099] 11 ignition device [0100] 12 NO.sub.x sensor (optional), in particular NO.sub.x sensors do not have to be provided at all illustrated positions, [0101] 13 temperature sensor (optional), in particular temperature sensors do not have to provided at all illustrated positions, [0102] 14 oxidation catalytic converter (optional), in particular alternatively or additionally there can be an ammonia slip catalytic converter and/or oxidation catalytic converter upstream of the SCR catalytic converter [0103] 15 injection device for reducing agent [0104] 16 exhaust gas aftertreatment apparatus [0105] 17 exhaust manifold [0106] 18 charging air temperature control device (optional)

[0107] FIG. 6 shows a genset, which is or can be electrically connected to a power supply grid 23, and having an internal combustion engine 1 according to the invention which is coupled to an electric generator 8 by means of a mechanical coupling 24.

[0108] The term state of the engine block 5 is used to denote in particular (individually or in any combination, naturally not all the following variables have to be taken into account): [0109] the temperature of the exhaust gases directly after a turbine of a possibly provided turbocharger 9 and/or directly after exhaust valves of the piston-cylinder units 2; [0110] temperature of operating means (like oil, cooling water, . . . ) or a material of the engine block 5 itself; [0111] NO.sub.x proportion or component in the exhaust gases in an exhaust manifold 17 after a possibly provided low-pressure turbine of a turbocharger 9 before an injection device 15 for reducing agent of the at least one SCR catalytic converter 4 (preferably for each engine bank of the engine block 5); [0112] NO.sub.x proportion or component in the exhaust gases at a discharge 7 from the at least one SCR catalytic converter; [0113] ratio of NO proportion or component to NO.sub.2 in the exhaust gas or the NO.sub.2 proportion or component to NO.sub.x or the NO proportion or component to NO.sub.x, that can be converted as desired, as the following applies: NO.sub.x=NO+NO.sub.2; [0114] actual speed of a crankshaft of the internal combustion engine 1, driven by the piston-cylinder units 2 of the engine block 5; [0115] speed of a turbocharger 9 which is possibly provided; [0116] exhaust gas pressure ensuing from a degree of opening of a wastegate 10 which is possibly provided; [0117] selected ignition times for the piston-cylinder units 2; [0118] on/off state of ignition devices for the piston-cylinder units 2; [0119] charging pressure (pressure in front of the inlet valves of the piston-cylinder units 2); [0120] charging temperature (temperature in front of the inlet valves of the piston-cylinder units 2); [0121] induction air temperature; [0122] fuel mass flow or mixture mass flow to the piston-cylinder units 2; [0123] air mass flow; [0124] currently produced mechanical and/or electrical (in the case of a genset) power; and [0125] valve control times (in the case of a variable valve drive).

[0126] The state of the engine block 5 can be influenced by way of the engine closed-loop control unit 3 by means of actuators known in the state of the art (and therefore not shown). For example: [0127] the temperature of the exhaust gases can be influenced directly after outlet valves of the piston-cylinder units 2 by the selection of an ignition time and/or the air excess number of the fuel-air mixture and/or exhaust gas recycling, total amount of fuel, temperature of the charging air or the fuel-air mixture in front of inlet valves of the piston-cylinder units 2, skip firing, valve control times and so forth; [0128] the NO.sub.x proportion or component in the exhaust gases in the exhaust manifold 17 can be influenced by the choice of a combustion temperature and/or combustion speed, in particular by the choice of an ignition time and/or the air excess number λ of the fuel-air mixture and/or exhaust gas recycling, total amount of fuel, temperature of the charging air or the fuel-air mixture in front of inlet valves of the piston-cylinder units 2, valve control times and so forth; [0129] the exhaust gas backpressure can be influenced by the degree of opening of an optionally provided wastegate 10 or by a variable turbine geometry (VTG); and [0130] the selected ignition times and/or the on/off state (skip firing) of ignition devices for the piston-cylinder units 2 can be influenced by appropriate actuation of the ignition devices of the piston-cylinder units 2.

[0131] The term state of the exhaust gas aftertreatment apparatus 16 is used to mean in particular (individually or in any combination, naturally not all the following variables have to be taken into consideration): [0132] the exhaust gas mass flow fed to the at least one SCR catalytic converter 4; [0133] a temperature of a catalytic zone and/or a temperature of the exhaust gas at an inlet location and/or a temperature of the exhaust gas at a discharge location of the at least one SCR catalytic converter 4; [0134] a mass flow Redux of reducing agent introduced into the at least one SCR catalytic converter 4; [0135] an amount of reducing agent reacted in the catalytic zone of the at least one SCR catalytic converter 4; [0136] an NH.sub.3 storage state of the at least one SCR catalytic converter 4; [0137] the state of a possibly provided heating device for the at least one SCR catalytic converter 4; and [0138] state of a possibly provided oxidation catalytic converter 14.

[0139] The state of the exhaust gas aftertreatment apparatus 16 can be influenced by the catalytic converter closed-loop control device 6 by way of actuators known in the state of the art (and therefore not shown). By way of example, the following can be influenced: [0140] the exhaust gas mass flow fed to the at least one SCR catalytic converter 4, influenced by the selection of a power output or an operating point of the engine block 5; [0141] the temperature of the catalytic zone of the at least one SCR catalytic converter 4, influenced by a temperature of the supplied exhaust gas and/or a heating device and/or a change in the exhaust gas mass flow; [0142] the temperature at the inlet to the at least one SCR catalytic converter 4, influenced by a temperature of the supplied exhaust gas and/or a heating device; [0143] a mass flow Redux of reducing agent introduced into the at least one SCR catalytic converter 4, being influenced by suitable actuation of an injection device 15 for reducing agent; [0144] the NH.sub.3 storage state in the catalytic zone of the at least one SCR catalytic converter 4, being influenced by the supplied amount of reducing agent, the temperature of the catalytic zone, a change in the exhaust gas mass flow, a change in the NO.sub.x proportion or component and/or the NO.sub.2 proportion or component of the exhaust gas.

[0145] The engine closed-loop control unit 3 can be or is prescribed a target value NO.sub.x.sub.,Tar for an NO.sub.x average value NO.sub.x of the NO.sub.x proportion or component of the exhaust gases in relation to a predetermined or predeterminable period of time t.sub.av, at a discharge 7 from the exhaust gas aftertreatment apparatus 16.

[0146] The engine closed-loop control unit 3, at least during the period t.sub.av, is in an operating mode in which it is configured to continuously calculate an NO.sub.x reference value NO.sub.x,Ref(t) for the catalytic converter closed-loop control device 6 having regard to already emitted NO.sub.x proportions or components and the predeterminable or predetermined target value NO.sub.x.sub.,Tar, which reference value is so selected that, at the end of the predeterminable or predetermined period of time t.sub.av, the predeterminable or predetermined target value NO.sub.x.sub.,Tar results at the discharge of the exhaust gas aftertreatment apparatus 16, and to feed the calculated NO.sub.x reference value NO.sub.x,Ref(t) to the catalytic converter closed-loop control device 6 as an NO.sub.x setpoint value.

[0147] FIG. 2 shows a typical operating situation in relation to the FIG. 1 embodiment of an internal combustion engine 1 according to the invention, the starting point here being a start of the internal combustion engine 1 by actuating a start button at the moment in time t.sub.1.

[0148] At the moment in time t.sub.3, the internal combustion engine 1 has reached the nominal power output (here, in the form of an electrical nominal power output P.sub.el of a genset afforded by way of a coupled electric generator—not shown in FIG. 1 as it corresponds to the state of the art, but see FIG. 6), so that the following applies for the starting time: t.sub.Start=t.sub.3−t.sub.1. The starting operation is therefore concluded at the moment in time t.sub.3 (here, for example approximately 5 minutes).

[0149] Within the starting time t.sub.Start in relation to the NO.sub.x proportions or components occurring in the engine block 5 at NO.sub.x,in of the exhaust gases (the index “in” is adopted because this involves the NO.sub.x proportions or components flowing into the exhaust gas aftertreatment apparatus 16), it is possible to see two clear peaks, namely a first peak by virtue of the increase in the speed v to a nominal value (synchronous speed in relation to a power supply grid) and—after coupling of the genset to the power supply grid and the load uptake resulting therefrom—a second peak because of the build-up in torque during the turbo lag (which can be seen in the electrical power output as a divergence which remains behind the predetermined ramp). After overcoming the turbo lag (as soon as the turbocharger or turbochargers is or are brought up to speed), the NO.sub.x proportions or components NO.sub.x,in in the exhaust gases occurring in the engine block 5 fall to a first value which is constant for the rest of the starting time t.sub.Smart.

[0150] The reduction in the NO.sub.x proportions or components NO.sub.x,in in the exhaust gases occurring in the engine block 5, that can be seen after the conclusion of the starting operation, is to be attributed to the fact that the engine closed-loop control unit 3 is configured, after the attainment of a nominal power output of the internal combustion engine 1, for a predetermined or predeterminable period of time, to increase a charging pressure of the engine block 5 and/or to set an ignition time of the ignition in the piston-cylinder units to late (see also the combustion diagram in FIG. 4).

[0151] The engine closed-loop control unit 3 monitors a conversion rate R.sub.conv(t) of the exhaust gas aftertreatment apparatus as an absolute value or—preferably—relative to an expected target value. The SCR catalytic converter 4 begins to work at the moment in time t.sub.4 as the temperature necessary for reduction of the NO.sub.x in the catalytic zone is reached and reducing agent is injected with a mass flow Redux by the injection device 15 (controlled by the catalytic converter closed-loop control device 6) into the exhaust manifold 17. Therefore, the conversion rate R.sub.conv(t) begins to rise from the value zero, and the NO.sub.x proportions or components NO.sub.x,out of the exhaust gases at the discharge from the SCR catalytic converter 4 begin to diverge from the NO.sub.x proportions or components NO.sub.x,in (the expected target value of the conversion rate R.sub.conv(t) is first reached at the moment in time t.sub.5).

[0152] As from the moment in time ta, the engine closed-loop control unit 3 begins to enrich the air-fuel mixture again and to set the ignition time back to earlier (see also the combustion diagram in FIG. 4). Therefore, the NO.sub.x proportions or components NO.sub.x,in increase again to the value at the moment in time t.sub.3, this however can be accepted as now in fact the SCR catalytic converter 4 is working.

[0153] At the moment in time t.sub.2, the predetermined period of time ta, (here, for example, 30 minutes) has expired and the NO.sub.x reference value NO.sub.x,Ref(t) for the catalytic converter closed-loop control device 6 has reached the predetermined target value NO.sub.x.sub.,Tar. (see FIG. 5).

[0154] The illustration, as from the moment in time t.sub.6 (here, for example, 2 hours) to the moment in time t.sub.7 (here, for example, 24 hours), shows by way of example that here a 24 hours—target value NO.sub.x.sub.,Tar which is increased in relation to the 30 minutes—target value NO.sub.x.sub.,Tar is accepted in order to minimize a consumption of reducing agent.

[0155] FIG. 3 shows an optional control diagram in which the engine closed-loop control unit 3 of the internal combustion engine 1 in FIG. 1, to reduce the NO.sub.x proportion or component in the exhaust gases that is emitted during a starting time by the internal combustion engine 1, is additionally configured during the starting time t.sub.Smart of the internal combustion engine 1 to predetermine a power output ramp (dotted line which covers over a long period of time with the solid line) for the engine block 5 (here, for the electrical power output P.sub.el) in a first time portion, preferably after reaching a minimum power output (moment in time t.sub.8) until reaching a predetermined limit value for the power output (moment in time t.sub.11) with a first lesser gradient and in a second time portion (from the moment in time t.sub.11) until reaching a nominal power output of the internal combustion engine 1 (at the moment in time t.sub.3) with a second greater gradient, wherein it is preferably provided that the second greater gradient is calculated in dependence on the remaining time (period t.sub.3−t.sub.11) until the starting time t.sub.Smart is reached.

[0156] The solid line represents the actual power output. It can be seen that the engine block 5 can follow the power output ramp only after overcoming the turbo lag, which occupies the greatest part of the period of time t.sub.9−t.sub.8.

[0157] A power ramp is shown in dashed-line form without the optional control scheme, and it can be seen that from the outset a steeper power output ramp is adopted, which during the turbo lag leads to increased NO.sub.x emissions, which as from the moment in time t.sub.9 would have to be compensated by a drop in the power output ramp in order to be able to reach the predetermined NO.sub.x average value NO.sub.x of the NO.sub.x proportion or component of the exhaust gas for the period of time t.sub.av.

[0158] FIG. 4 shows a combustion diagram in which it can be seen that the engine closed-loop control unit 3 of the internal combustion engine 1 in FIG. 1 is optionally configured to move a current first operating point 19 of the engine block 5, which occurs after attainment of a nominal power output of the internal combustion engine 1, to a transient operating point 20 with lower NO.sub.x emissions (the NO.sub.x emissions occurring in the engine block 5, for which straight lines involving constant values are shown, decrease upwardly in FIG. 4), for example, to an operating point at higher temperatures (the temperatures of the piston-cylinder units, for which straight lines involving constant values are shown, increase towards the left in FIG. 4), of the exhaust gases immediately after exhaust valves of the piston-cylinder units (preferably in that respect the temperature T of the hottest piston-cylinder unit is used by the engine closed-loop control unit 3). That can be achieved for example by adjusting an ignition time of ignition in the piston-cylinder units to late and/or (preferably, at the same time, leaning of the fuel-air mixture available for combustion in the piston-cylinder units from the first value λ.sub.1 to a second value λ.sub.2 (naturally in such a way that no misfires or knocking occurs). In the combustion diagram (with the coordinate axes “air excess number” and ignition time measured at the “crankshaft angle θ”), the operating point thereby moves within the knock limit and the misfire limit in the direction of higher exhaust gas temperatures.

[0159] That can optionally occur in a first step (along a first trajectory 21 in the combustion diagram) by means of a pre-control in order to cause rapid first adjustment of the operating point of the engine block 5. That can be followed in a second step (along a second trajectory 22 in the combustion diagram) by a control action in order to be able to more accurately select the ensuing transient operating point 20.

[0160] When the at least one SCR catalytic converter begins to reduce the NO.sub.x proportion or component in the exhaust gas (because the catalytic zone has reached the required temperature), the engine closed-loop control unit provides for open-loop and/or closed-loop control of the engine block in such a way that the current operating point moves away from the transient operating point back in the direction of the first operating point (preferably, on the same trajectory as for the movement from the nominal operating point to the steady-state operating point, but in the reverse direction) and reaches same.

[0161] FIG. 5 shows once again the most important above-discussed parameters in the course of time t. It can be clearly seen how the time-dependent NO.sub.x reference value NO.sub.x,Ref(t) increasingly approaches the predetermined target value NO.sub.x.sub.,Tar and finally reaches it at the time t.sub.2 (right-hand dark point). By way of example, shown for an earlier time (left-hand dark point) in a shape with a gray background are rectangles which correspond to the average NO.sub.x proportions or components in the exhaust gases, that have already been emitted by the internal combustion engine 1 up to that moment in time, and the average NO.sub.x proportions or components in the exhaust gases, that are thus still available to reach the predetermined target value NO.sub.x.sub.,Tar.

[0162] With reference to FIG. 3, the synchronization duration is measured (here equal: t.sub.8−t.sub.1) and in dependence on the synchronization duration it is decided (immediately after the moment in time t.sub.5) whether the mixture is to be more or less greatly enriched, and therefore a desired air excess number λ is established in dependence on the synchronization duration.

LIST OF REFERENCES

[0163] 1 internal combustion engine [0164] 2 piston-cylinder units [0165] 3 engine closed-loop control unit [0166] 4 SCR catalytic converter [0167] 5 engine block [0168] 6 catalytic converter closed-loop control device [0169] 7 discharge of the SCR catalyst [0170] 8 electric generator [0171] 9 turbocharger [0172] 10 wastegate [0173] 11 ignition device [0174] 12 NO.sub.x sensor [0175] 13 temperature sensor [0176] 14 oxidation catalytic converter [0177] 15 injection device for reducing agent [0178] 16 exhaust gas aftertreatment apparatus [0179] 17 exhaust manifold [0180] 18 charging air temperature control device [0181] 19 first operating point [0182] 20 transient operating point [0183] 21 first trajectory in the combustion diagram [0184] 22 first trajectory in the combustion diagram [0185] 23 power supply grid [0186] 24 mechanical coupling between internal combustion engine and electric generator [0187] t.sub.av predetermined or predeterminable period of time [0188] t.sub.1, t.sub.2, t.sub.3, . . . first, second, third . . . moment in time [0189] t current moment in time [0190] t.sub.Start starting time of the internal combustion engine [0191] NO.sub.x(t) rate of the NO.sub.x proportion or component (mass flow or concentration) at the moment in time t [0192] NO.sub.x NO.sub.x average value [0193] NO.sub.x.sub.,Tar predeterminable or predetermined (constant) target value [0194] NO.sub.x,Ref(t) time-dependent NO.sub.x reference value (mass flow) at the moment in time t [0195] cumulNO.sub.2 cumulated NO.sub.x proportion or component [0196] R.sub.conv(t) conversion rate of the exhaust gas aftertreatment apparatus at the moment in time t [0197] NO.sub.x,in (t) mass flow entering the exhaust gas aftertreatment apparatus at the moment in time t [0198] NO.sub.x,out(t) mass flow issuing from the exhaust gas aftertreatment apparatus at the moment in time t [0199] Redux(t) mass flow of reducing agent at the moment in time t [0200] λ air excess number [0201] λ.sub.1 first value of the air excess number [0202] λ.sub.2 second value of the air excess number [0203] P.sub.m mechanical power output of the internal combustion engine [0204] P.sub.el electrical power output of the internal combustion engine [0205] V speed of a crankshaft of the engine block [0206] T temperature [0207] θ crankshaft angle