US20180187588A1

US20180187588A1 - Method for operating an exhaust gas aftertreatment system, exhaust gas aftertreatment system, and internal combustion engine with an exhaust gas aftertreatment system

Info

Publication number: US20180187588A1
Application number: US15/737,527
Authority: US
Inventors: Daniel Chatterjee; Klaus Rusch; Guido Schäffner; Klaus Wehler
Original assignee: MTU Friedrichshafen GmbH
Current assignee: Rolls Royce Solutions GmbH
Priority date: 2015-06-17
Filing date: 2016-06-06
Publication date: 2018-07-05
Also published as: CN107709719B; HK1251027A1; WO2016202435A1; CN107709719A; EP3311012A1; EP3311012B1; DE102015211169A1

Abstract

A method for operating an exhaust gas aftertreatment system, having the following steps: determining a permissible energy input into at least one exhaust gas aftertreatment element of the exhaust gas aftertreatment system; ascertaining a current energy input into the at least one exhaust gas aftertreatment element by ascertaining at least one energy input variable which characterizes the current energy input; and actuating an adjusting device which varies a distribution of an exhaust gas mass flow to the at least one exhaust gas aftertreatment element and a bypass path that runs about the at least one exhaust gas aftertreatment element depending on the permissible energy input and the current energy input.

Description

The invention relates to a method for operating an exhaust gas aftertreatment system, to an exhaust gas aftertreatment system and to an internal combustion engine with an exhaust gas aftertreatment system.
Under certain operating conditions there is a risk of damage or destruction of exhaust gas aftertreatment systems, or an undesired release of substances stored in an exhaust gas aftertreatment system can occur. In order to avoid such circumstances and, in particular, overheating of exhaust gas aftertreatment elements of an exhaust gas aftertreatment system, it is basically known to provide bypass paths around exhaust gas aftertreatment elements, wherein typically in such bypass paths an actuation element, in particular a bypass flap, is provided for setting an exhaust gas mass flow which flows through the bypass path. The setting of the actuation element can be adjusted here, for example, to a temperature which is measured upstream of the exhaust gas aftertreatment system. A disadvantage of this is that slow heating of an exhaust gas aftertreatment element is virtually impossible to sense. In particular, the temperature measured upstream of an exhaust gas aftertreatment element says nothing about the time profile of a rise in temperature in the exhaust gas aftertreatment element. Alternatively, it is possible to adjust the setting of the actuation element to a temperature measured downstream of an exhaust gas aftertreatment system. It is disadvantageous here that such adjustment is too slow acting, and in particular destructive or damaging events which occur quickly cannot be avoided. Finally, it is also possible to prevent damage or destruction of an exhaust gas aftertreatment system by means of a thermal management system for the engine. This is not possible under all operating conditions of an engine, in particular not in the case of a rapid acceleration of the engine.
The invention is based on the object of providing a method for operating an exhaust gas aftertreatment system, an exhaust gas aftertreatment system and an internal combustion engine whereby the abovementioned disadvantages do not occur.
The object is achieved by providing the subject matters of the independent claims. Advantageous refinements can be found in the dependent claims and the description.
The object is achieved, in particular, by providing a method for operating an exhaust gas aftertreatment system which has the following steps: a permissible energy input into at least one exhaust gas aftertreatment element of the exhaust gas aftertreatment system is determined. An instantaneous energy input into the at least one exhaust gas aftertreatment element is ascertained by ascertaining at least one energy input variable which characterizes the instantaneous energy input, and an actuation device by means of which a distribution of an exhaust gas mass flow to the at least one exhaust gas aftertreatment element, on the one hand, and a bypass path around the at least one exhaust gas aftertreatment element, on the other can be varied, is actuated as a function of the permissible energy input and as a function of the instantaneous energy input. By determining the permissible energy input it is possible to define what quantity of energy, in particular what quantity of energy per unit of time, can be input into an exhaust gas aftertreatment element without said element being damaged or destroyed. Since the instantaneous energy input is ascertained, there is always sufficient information available in order to detect whether there is a risk of damage or destruction of the at least one exhaust gas aftertreatment element. Since the actuation device is actuated as a function of the permissible energy input, on the one hand, and the instantaneous energy input, on the other, it is possible to prevent in a very efficient way damage or destruction of the at least one exhaust gas aftertreatment element at any operating point of the exhaust gas aftertreatment system. In contrast to pure temperature measurement upstream or downstream of the at least one exhaust gas aftertreatment element, with the instantaneous energy input a variable is made available which is actually directly informative and relevant for the loading of the exhaust gas aftertreatment element. It also becomes apparent here that the energy which is input into the exhaust gas aftertreatment element constitutes a comparatively slow acting variable which is very suitable for actuating the actuation device as a function thereof. In contrast, pure temperature measurement is significantly more volatile and less suitable for carrying out stable open-loop or closed-loop control.
The term “energy input” is understood to mean a quantity of energy which is input into the at least one exhaust gas aftertreatment element. In this context, according to one refinement of the method this is a quantity of energy which is input per unit of time so that the energy input has the dimension of a power value. According to a different embodiment of the method it is possible that energy which is input in absolute terms into the at least one exhaust gas aftertreatment element during a predetermined time period is used as the energy input. For example, in this case it is possible that a quantity of energy which is input per unit of time into the at least one exhaust gas aftertreatment element is ascertained and integrated over a predetermined time period, in order to obtain the quantity of energy which is input in absolute terms. Both energy which is input per unit of time and energy which is input in absolute terms over a predetermined time period are suitable variables for permitting reliable prediction of possible damage or destruction of the exhaust gas aftertreatment element.
The term “energy input variable” is to be understood as meaning a variable which is characteristic of the instantaneous energy input, or on which the instantaneous energy input depends. In particular, this comprises at least one variable or a multiplicity of variables from which the instantaneous energy input can be derived, in particular calculated. It is possible that the instantaneous energy input is ascertained directly, for example on the basis of a model calculation or simulation. In this case, the at least one energy input variable is directly the instantaneous energy input.
The fact that the actuation device is actuated includes an open-loop or closed-loop control operation being carried out for the actuation device. A control operation can be carried out, for example, if the instantaneous energy input is not ascertained by measuring variables which are suitable for this at the exhaust gas aftertreatment element but instead by means of a model calculation or simulation, with the result that no precise knowledge is available and, in particular, no feedback of the actual instantaneous energy input occurs. Adjustment can be carried out, in particular, by virtue of the fact that the instantaneous energy input is ascertained on the basis of variables which are actually measured in the region of the or at the exhaust gas aftertreatment element, with the result that a feedback takes place. The fact that the actuation takes place as a function of the permissible energy input and the instantaneous energy input means, in particular, that the instantaneous energy input is compared with the permissible energy input, wherein the actuation device is actuated as a function of the comparison result. For example, it is possible for a difference between the instantaneous energy input and the permissible energy input to be formed, wherein the actuation device is actuated as a function of the difference. For example, it is possible to actuate the actuation device in such a way that a main part of the exhaust gas mass flow flows via the bypass path if the instantaneous energy input exceeds the permissible energy input. Conversely, the actuation device can be actuated in such a way that a main part of the exhaust gas mass flow is directed via the at least one exhaust gas aftertreatment element if the instantaneous energy input is less than the permissible energy input.
A bypass path is understood here to be, in particular, a bypass, specifically a line section, which branches off from a main exhaust gas path of the exhaust gas aftertreatment system upstream of the at least one exhaust gas aftertreatment element, and which has the at least one exhaust gas aftertreatment element, and opens again into the main exhaust gas path downstream of the at least one exhaust gas aftertreatment element.
The actuation device preferably has an actuation element or a multiplicity of actuation elements, in particular an actuation flap or a multiplicity of actuation flaps by which the exhaust gas mass flow can be distributed by the exhaust gas aftertreatment system to the at least one exhaust gas aftertreatment element, on the one hand, and to the bypass path, on the other. In this context, continuous distribution to the various paths of respectively 0% to 100% is preferably possible.
An embodiment of the method is preferred which is distinguished by the fact that the permissible energy input is determined as a function of at least one operating parameter of the at least one exhaust gas aftertreatment system. The permissible energy input varies, in particular, as a function of the specific operating conditions for the at least one exhaust gas aftertreatment element.
In particular, the permissible energy input is preferably determined as a function of a soot load of an exhaust gas aftertreatment element which is embodied as a particle filter. In this context, the permissible energy input typically varies as a function of whether a soot load threshold of the particle filter which triggers a regeneration event is exceeded or not. If such a predetermined soot load threshold is exceeded, the soot is to be ignited, for which purpose a relatively high permissible energy input is preferably set than before the soot load threshold is exceeded. On the other hand, the intension is to prevent the soot burn-off reaction from carrying on, wherein the particle filter would be loaded too highly in thermal terms. Instead, the soot burn-off is to take place continuously and with a predetermined, maximum burn-off rate, and preferably in a controlled fashion, in order to avoid excessively high thermal loading of the particle filter. For this purpose, the permissible energy input is preferably also limited upward in the case of a soot burn-off.
It is also possible for the permissible energy input to be determined as a function of a reducing agent load of an exhaust gas aftertreatment element which is designed as a catalytic converter for selective catalytic reduction of nitrogen oxides. Such a catalytic converter, which is also referred to as an SCR catalytic converter, typically acts as an accumulator for a reducing agent, in particular for ammonia, which is not to be expelled or discharged from the catalytic converter. In this context, discharging or expulsion of the reducing agent from the catalytic converter is dependent on the energy input into the catalytic converter. The more energy that is input into the catalytic converter, the greater the degree to which the reducing agent is expelled therefrom. Furthermore, the discharge is higher at a given energy input the larger the amount of reducing agent which is stored in the catalytic converter. Therefore, the permissible energy input is dependent, in terms of preventing the discharging of reducing agent, on the loading of the catalytic converter with reducing agent.
It is also possible that the permissible energy input is determined as a function of a hydrogen load of a catalytic converter, in particular of an oxidation catalytic converter or of an SCR catalytic converter. It becomes apparent here that hydrocarbons which are stored in the catalytic converter are to be expelled, in particular baked out, but this is to occur without said hydrocarbons being ignited, which could otherwise lead to thermal damage of the catalytic converter. However, this is particularly critical since the interval between a minimum temperature at which the hydrocarbons are actually expelled and a maximum temperature at which the expelled hydrocarbons ignite is comparatively small and is, in particular, between 10 K and 20 K. Therefore, in particular in this case it is important to select the permissible energy input suitably as a function of the hydrocarbon load of the catalytic converter.
An embodiment of the method is preferred which is distinguished by the fact that an exhaust gas mass flow through the at least one exhaust gas aftertreatment element and/or an exhaust gas temperature are/is ascertained as an energy input variable. It is possible for just one of these variables to be measured, wherein the other variable is preferably determined by simulation, model calculation or on the basis of a characteristic curve or a characteristic diagram. However, both the exhaust gas mass flow through the at least one exhaust gas aftertreatment element and an exhaust gas temperature are particularly preferably ascertained by measurement in the region of the exhaust gas aftertreatment element. The energy input can be ascertained with a high level of accuracy if both the exhaust gas mass flow and the exhaust gas temperature are ascertained, in particular, measured, at the at least one exhaust gas aftertreatment element. It becomes apparent here, in fact, that the thermal capacity c_pof the exhaust gas at a constant pressure is very well known and moreover is also constant in a good approximation over all the operating points of the exhaust gas aftertreatment system. If this thermal capacity c_pis known, and the exhaust gas mass flow through the at least one exhaust gas aftertreatment system as well as the exhaust gas temperature are also known, the energy which is input into the at least one exhaust gas aftertreatment element per unit of time can readily be ascertained, in particular calculated, therefrom with a high level of accuracy. The instantaneous energy input is preferably calculated from the exhaust gas mass flow through the at least one exhaust gas aftertreatment element and the exhaust gas temperature.
Alternatively or additionally, it is also possible to ascertain the instantaneous energy input into the at least one exhaust gas aftertreatment element directly from a model calculation or simulation, a characteristic curve or a characteristic diagram.
In one embodiment of the method there is provision that the exhaust gas temperature is measured upstream of the at least one exhaust gas aftertreatment element. In a different embodiment of the method there is provision that the exhaust gas temperature is measured downstream of the at least one exhaust gas aftertreatment element. Alternatively or additionally there is preferably provision that the exhaust gas temperature is measured in the at least one exhaust gas aftertreatment element. For this purpose, preferably, in particular, temperature sensors are provided, wherein a temperature sensor is arranged upstream, downstream and/or in the at least one exhaust gas aftertreatment element. It is possible for an average exhaust gas temperature in the exhaust gas aftertreatment element to be determined by forming mean values of a temperature which is measured upstream of the exhaust gas aftertreatment element and a temperature which is measured downstream of the exhaust gas aftertreatment element. Additionally or alternatively, it is possible that the energy which is taken up by the exhaust gas aftertreatment element is determined by measuring differences between the exhaust gas temperature upstream of the exhaust gas aftertreatment element and downstream of the exhaust gas aftertreatment element. Alternatively or additionally, it is possible that the energy which is taken up by the exhaust gas aftertreatment element is determined, on the basis of the exhaust gas temperature, from a model or a simulation of the exhaust gas aftertreatment element.
It is also possible that an exhaust gas temperature is not measured but instead is determined from a model or a simulation or a characteristic diagram or a characteristic curve, in particular from a model or a simulation of an internal combustion engine in combination with which the exhaust gas aftertreatment system is operated. It is possible here for the exhaust gas temperature to be determined very precisely as a function of the operating point, by means of a model, a simulation, a characteristic diagram or a characteristic curve.
An embodiment of the method is also preferred which is distinguished by the fact that the exhaust gas mass flow is determined as a function of an instantaneous operating state of an internal combustion engine, in combination with which the exhaust gas aftertreatment system is operated. In this context it is, in particular, possible to determine the exhaust gas mass flow on the basis of a model calculation, a simulation, a characteristic diagram or a characteristic curve as a function of the operating point. Alternatively or additionally, it is possible for the exhaust gas mass flow to be determined as a function of a pressure loss variable across the at least one exhaust gas aftertreatment element. Alternatively or additionally, it is possible for the exhaust gas mass flow to be ascertained as a function of a pressure loss variable across at least one actuation element of the actuation device—in particular additionally as a function of an instantaneous actuation position, in particular an actuation angle, of the actuation element. The pressure loss variable is preferably determined by measuring a pressure upstream of the exhaust gas aftertreatment element and/or of the actuation element, as well as a pressure downstream of the exhaust gas aftertreatment element and/or of the actuation element. From these pressure values it is possible to determine a differential pressure value which can be used as a pressure loss variable. If at the same time the exhaust gas temperature in the region of the at least one exhaust gas aftertreatment element and/or of the actuation element and, if appropriate, the actuation position of the actuation element is/are known, it is readily possible to determine the exhaust gas mass flow with a high level of accuracy from the pressure loss variable and the exhaust gas temperature. It is also possible for the pressure loss variable to be determined by means of a differential pressure sensor.
The object is also achieved in that an exhaust gas aftertreatment system is provided which has at least one exhaust gas aftertreatment element, a bypass path around the exhaust gas aftertreatment element, an actuation device which is configured to distribute an exhaust gas mass flow to the at least one exhaust gas aftertreatment element, on the one hand, and the bypass path, on the other, and a control device. In this context, the control device has a determining means for determining a permissible energy input into the at least one exhaust gas aftertreatment element, an ascertaining means for ascertaining an instantaneous energy input into the at least one exhaust gas aftertreatment element, and an actuation means for actuating the actuation device. The control device is configured to actuate the actuation device as a function of the permissible energy input and as a function of the instantaneous energy input. In particular, the control device is preferably configured to carry out a method as claimed in one of the embodiments described above. In this context, the advantages which have already been explained in relation to the method are obtained in relation to the exhaust gas aftertreatment system.
It is possible for the control device to be configured to determine the permissible energy input and/or the instantaneous energy input on the basis of model calculations and/or simulations. The control device is, however, preferably operatively connected to at least one sensor in order to determine the permissible energy input and/or the instantaneous energy input. This sensor is preferably at least one pressure sensor and/or at least one temperature sensor, which are arranged, in particular, in the region of the at least one exhaust gas aftertreatment element. With suitable pressure sensors, for example a soot load of a particle filter can readily be determined, preferably on the basis of a pressure loss variable across the particle filter, wherein such a procedure is known per se, and more details will therefore not be given on it here. In a similar way, a pressure-sensor arrangement, as already explained above, can be used to determine an exhaust gas mass flow via the at least one exhaust gas aftertreatment element in order to ascertain the instantaneous energy input.
At least one temperature sensor is preferably arranged upstream of, downstream of and/or in the at least one exhaust gas aftertreatment element and operatively connected to the control device.
It is possible for further suitable sensors to be provided in order to detect, for example, a reducing agent load of an SCR catalytic converter and/or a hydrocarbon load of an oxidation catalytic converter or of an SCR catalytic converter.
The exhaust gas aftertreatment system preferably has a multiplicity of exhaust gas aftertreatment elements. In particular, it is possible for the exhaust gas aftertreatment system to have a multiplicity of different exhaust gas aftertreatment elements, for example a particle filter, an oxidation catalytic converter and/or an SCR catalytic converter.
At least one first exhaust gas aftertreatment element and at least one second exhaust gas aftertreatment element are each assigned a separate bypass path and a separate actuation device. In this context it is possible for various groups of exhaust gas aftertreatment elements to be assigned separate bypass paths and separate actuation devices. Alternatively or additionally, it is possible for separate bypass paths and separate actuation devices to be individually assigned to specific exhaust gas aftertreatment elements. In the case of an assignment of a bypass path and of an actuation device to a group of exhaust gas aftertreatment elements, this group can be appropriately selected in this context, wherein exhaust gas aftertreatment elements which are assigned to the group preferably have similar conditions for a permissible energy input. In particular, it is possible to combine various exhaust gas aftertreatment elements of the same type, for example a multiplicity of particle filters, to which particle filters a bypass path and an actuation device are then jointly assigned. If specific individual bypass paths and actuation devices are assigned to specific individual exhaust gas aftertreatment elements, it is possible for each of these specific exhaust gas aftertreatment elements to define an individual permissible energy input and to actuate the actuation device in a correspondingly individual fashion, wherein each exhaust gas aftertreatment element is relieved of loading in an optimum way and protected against damage or destruction.
Alternatively or additionally, it is also possible for a global bypass path to be provided with a global actuation device, wherein the bypass path is provided around all the exhaust gas aftertreatment elements of the exhaust gas aftertreatment system. This constitutes a simultaneously effective and economical solution, because all the exhaust gas aftertreatment elements can be protected against damage and destruction with minimum expenditure in terms of cost and parts.
An exemplary embodiment of the exhaust gas aftertreatment system is preferred which is distinguished by the fact that the actuation device has precisely one actuation element for distributing the exhaust gas mass flow. This actuation element can be, for example, an exhaust gas switch by means of which the exhaust gas flow can be distributed to the main exhaust gas path via the at least one exhaust gas aftertreatment element, and the bypass path, or it can be an actuation flap in the bypass path, in particular a bypass flap, by which the bypass path can be closed and opened, preferably continuously.
Alternatively it is possible for the actuation device to have in each case an actuation element in the bypass path and upstream of the exhaust gas aftertreatment element, preferably downstream of a branch of the bypass path, ahead of the exhaust gas aftertreatment element when viewed in the direction of flow. In this case, two actuation elements are therefore provided, specifically a first in the main exhaust gas path downstream of the branch of the bypass path and a second in the bypass path, as a result of which a very sensitive and precise distribution of the exhaust gas mass flow is possible. In this context there is particularly preferably provision for the two actuation devices to be coupled to one another in opposite directions, in particular in such a way that the one actuation device opens by the same amount as the other actuation device closes. This can ensure that the positions of the actuation elements always correspond to suitable portions of the exhaust gas mass flow, which add up to form 100%.
The at least one actuation element which has the actuation device is preferably embodied as a flap. Alternatively, it is possible for the at least one actuation element to be embodied as a valve or in some other suitable way.
Finally, the object is achieved by providing an internal combustion engine which has an exhaust gas aftertreatment system as claimed in one of the exemplary embodiments described above. In this context, the advantages which have already been explained in relation to the exhaust gas aftertreatment system and the method are obtained in relation to the internal combustion engine.
At least one control unit of the internal combustion engine, in particular the central control unit of the internal combustion engine (engine control unit-ECU) is used as the control device of the exhaust gas aftertreatment system. However, it is also possible for the functionality of the control device of the exhaust gas aftertreatment system to be performed by a multiplicity of control units which interact with one another. These may be control units of the exhaust gas aftertreatment system or of the internal combustion engine in the stricter sense. It is also possible for the control device to be assigned completely to the exhaust gas aftertreatment system.
It is possible for the method to be permanently implemented in an electronic structure, in particular a hardware structure, of the control device. Alternatively or additionally, it is possible that a computer program product which has instructions on the basis of which the method can be carried out when the computer program product runs on the control device is loaded into the control device.
The invention also includes a computer program product which has machine-readable instructions, on the basis of which an embodiment of the method can be carried out when the computer program product runs on a computing device, in particular on a control device.
The invention also includes a data carrier which has such a computer program product.
The internal combustion engine is preferably embodied as reciprocating piston engine. It is possible for the internal combustion engine to be configured to drive a passenger car, a truck or a utility vehicle. In one preferred exemplary embodiment, the internal combustion engine serves to drive, in particular, relatively heavy land vehicles or watercraft, for example mining vehicles or trains, wherein the internal combustion engine is used in a locomotive or a power car, or ships. Use of the internal combustion engine to drive a vehicle which is used in defence, for example a tank, is also possible. An exemplary embodiment of the internal combustion engine is preferably also used in a stationary fashion, for example for providing a stationary power supply in an emergency operating mode, continuous load mode or peak load mode, wherein in this case the internal combustion engine preferably drives a generator. A stationary application of the internal combustion engine for driving auxiliary assemblies, for example fire extinguisher pumps on drills is also possible. Furthermore, an application of the internal combustion engine in the field of mining fossil raw materials and, in particular, fossil fuels, for example oil and/or gas. It is also possible to use the internal combustion engine in the industrial field or in the field of construction, for example in a construction or building machine, for example in a crane or an excavator. The internal combustion engine is preferably embodied as a diesel engine, as a gasoline engine, as a gas engine for operation with natural gas, biogas, special gas or some other suitable gas. In particular, if the internal combustion engine is embodied as a gas engine, it is suitable for use in a block heating plant for the stationary generation of energy.
The description of the method, on the one hand, and of the exhaust gas aftertreatment system as well as of the internal combustion engine, on the other hand, are to be understood as complementary to one another. Features of the exhaust gas aftertreatment system and/or of the internal combustion engine which have been explicitly or implicitly explained in relation to the method are preferably features, individually or when combined with one another, of a preferred exemplary embodiment of the exhaust gas aftertreatment system and/or of the internal combustion engine. Method steps which were described explicitly or implicitly in relation to the exhaust gas aftertreatment system and/or the internal combustion engine are preferably individually, or when combined with one another, steps of a preferred embodiment of the latter. This preferably distinguished by means of at least one method step which is conditional on at least one feature of an inventive or preferred exemplary embodiment of the exhaust gas aftertreatment system and/or of the internal combustion engine. The internal combustion engine and/or the exhaust gas aftertreatment system are/is preferably distinguished by at least one feature which is conditional on at least one step of an inventive or preferred embodiment of the method.

The invention will be explained in more detail below with reference to the drawing, in which:

FIG. 1 shows a schematic illustration of a first exemplary embodiment of an internal combustion engine having a first exemplary embodiment of an exhaust gas aftertreatment system;

FIG. 2 shows a schematic illustration of a second exemplary embodiment of the exhaust gas aftertreatment system, and

FIG. 3 shows a schematic illustration of a third exemplary embodiment of the exhaust gas aftertreatment system.

FIG. 1 shows a schematic illustration of a first exemplary embodiment of an internal combustion engine 1 with a first exemplary embodiment of an exhaust gas aftertreatment system 3. In this context, an engine block 5 of the internal combustion engine 1 is connected to the exhaust gas aftertreatment system 3 in such a way that exhaust gas can be fed from the engine block 5 via the exhaust gas aftertreatment system 3 to an outlet, in particular an exhaust, which is illustrated here schematically by an arrow P. The exhaust gas aftertreatment system 3 has at least one exhaust gas aftertreatment element 7 which can be embodied, for example, as a particle filter, as an SCR catalytic converter or as an oxidation catalytic converter. It is possible for the exhaust gas aftertreatment system 3 to have more than one exhaust gas aftertreatment element 7.
The exhaust gas aftertreatment system 3 also has a bypass path 9 around the at least one exhaust gas aftertreatment element 7, which bypass path 9 is embodied, in particular, as a bypass. In this context it is possible that the bypass path 9 is provided to bypass precisely one exhaust gas aftertreatment element 7, or that it is provided to bypass a group of exhaust gas aftertreatment elements 7 or else also all the exhaust gas aftertreatment elements 7 of the exhaust gas aftertreatment system 3.
The exhaust gas aftertreatment system 3 also has an actuation device 11 which is configured to distribute an exhaust gas mass flow to the at least one exhaust gas aftertreatment element 7, on the one hand, and the bypass path 9, on the other. In the exemplary embodiment illustrated here, the actuation device 11 has precisely one actuation element 13, which is provided here as an exhaust gas switch in a branch 15, at which a main exhaust gas path 17, comprising the exhaust gas aftertreatment element 7, and the bypass path 9 separate off. Here, the actuation element 13 is preferably embodied as a flap which can pivot along a schematically indicated double arrow, by which flap the exhaust gas mass flow can be divided between the main exhaust gas path 17, on the one hand, and the bypass path 9, on the other.
The exhaust gas aftertreatment system 3 also has a control device 19. For its part, said control device 19 has a determining means 21 for determining a permissible energy input into the at least one exhaust gas aftertreatment element 7, an ascertaining means 23 for ascertaining an instantaneous energy input into the at least one exhaust gas aftertreatment element 7, and an actuation means 25 for actuating the actuation device 11. In this context, the control device 19 is configured to actuate the actuation device 11 as a function of the permissible energy input and of the instantaneous energy input into the at least one exhaust gas aftertreatment element 7, in particular in order to perform open-loop or closed-loop control of the actuation device 11 and preferably of an actuation position of the actuation element 13.
In this context it is possible for the permissible energy input to be used as a setpoint value within the scope of an adjustment process, wherein the instantaneous energy input is used as an actual value.
It is possible for the control device 19 to be embodied as an engine control unit or as a central control unit of the internal combustion engine 1. In particular, the control device 19 is preferably operatively connected to the engine block 5 in order to ascertain an instantaneous operating state of the internal combustion engine 1.
The ascertaining means 23 is preferably configured to ascertain the instantaneous energy input by ascertaining at least one energy input variable which characterizes the instantaneous energy input. In this context, preferably an exhaust gas mass flow through the at least one exhaust gas aftertreatment element 7 and/or an exhaust gas temperature in the region of the exhaust gas aftertreatment element 7, preferably the exhaust gas mass flow and the exhaust gas temperature, is used as energy input variable. A thermal capacity c_pat a constant pressure of the exhaust gas is preferably stored as a constant in the control device 19, in particular in the ascertaining means 23.
The determining means is preferably configured to determine the permissible energy input as a function of at least one operating parameter of the at least one exhaust gas aftertreatment element 7.
In order to ascertain an operating parameter of the at least one exhaust gas aftertreatment element and/or to determine an energy input variable, the exhaust gas aftertreatment system 3 preferably has a multiplicity of sensors, in particular a first pressure sensor 27 upstream of the exhaust gas aftertreatment element 7 and a second pressure sensor 29 downstream of the exhaust gas aftertreatment element 7. In particular, a pressure loss variable can be ascertained across the exhaust gas aftertreatment element 7 by means of the pressure sensors 27, 29. Instead of two separate pressure sensors 27, 29 it is also possible to use one differential pressure sensor.
A soot load of a particle filter can be ascertained from the pressure loss variable, for example as an operating parameter of the exhaust gas aftertreatment element 7. Additionally or alternatively, an exhaust gas mass flow can be ascertained across the exhaust gas aftertreatment element 7 from the pressure loss variable, preferably using the exhaust gas temperature in the region of the exhaust gas aftertreatment element 7.
A first temperature sensor 31 is preferably provided upstream of the exhaust gas aftertreatment element 7, wherein a second temperature sensor 32 is provided downstream of the exhaust gas aftertreatment element 7. For example, a mean value for the exhaust gas temperature in the exhaust gas aftertreatment element 7 can be ascertained on the basis of the measured values of the temperature sensors 31, 32. Alternatively or additionally, it is also possible to use a temperature sensor which is integrated into the exhaust gas aftertreatment element 7, or a temperature sensor which is arranged on the exhaust gas aftertreatment element 7 in such a way that it measures an exhaust gas temperature in the exhaust gas aftertreatment element 7. On the basis of a temperature difference between a measuring point upstream of the exhaust gas aftertreatment element 7 and a measuring point downstream of the exhaust gas aftertreatment element 7, in particular therefore on the basis of a temperature difference which is sensed with the temperature sensors 31, 32, it is possible to ascertain energy which is actually taken up by the exhaust gas aftertreatment element 7, by means of the heat loss in the exhaust gas.
It is also possible to ascertain the instantaneous energy input into the exhaust gas aftertreatment element 7 from the exhaust gas mass flow through the exhaust gas aftertreatment element 7, the known thermal capacity c_pof the exhaust gas at a constant pressure and the exhaust gas temperature. In particular, it is therefore readily possible to ascertain energy which is input per unit of time into the exhaust gas aftertreatment element 7. By integration over a predetermined time period it is therefore also possible to ascertain energy which is in absolute terms input into the exhaust gas aftertreatment element 7 in the predetermined time period.
The control device 19 is preferably operatively connected to the actuation device 11, in particular to the actuation element 13, in order to actuate it. The control device 19 is also preferably operatively connected to the pressure sensors 27, 29 and the temperature sensors 31, 33.
If one of the energy input variables which is preferably used to ascertain the instantaneous energy input, that is to say in particular the exhaust gas mass flow and/or the exhaust gas temperature, is not determined by measurement, it is possible to acquire them on the basis of a model calculation or a simulation, in particular for the engine block 5, or to read them out from a characteristic diagram or a characteristic curve of the internal combustion engine 1.
It is important that within the scope of the method proposed here, not only pure control of the exhaust gas temperature of the actuation device is used but instead the energy input into the exhaust gas aftertreatment element 7 is ascertained, said energy input being actually informative about possible damage or destruction of the exhaust gas aftertreatment element 7.
FIG. 2 shows a schematic illustration of a second exemplary embodiment of the exhaust gas aftertreatment system 3. Identical and functionally identical elements are provided with the same reference symbols, with the result that in this respect reference is made to the preceding description. Here, the actuation device 11 has precisely one actuation element 13 which is preferably embodied as an actuation flap and is arranged in the bypass path 9. The actuation element 13 is embodied, in particular, as a bypass flap.
FIG. 3 shows a schematic illustration of a third exemplary embodiment of the exhaust gas aftertreatment system 3. Identical and functionally identical elements are provided with the same reference symbols, with the result that in this respect reference is made to the preceding description. In this exemplary embodiment, the actuation device 11 has in each case one actuation element 13, 13′ in the bypass path 9, on the one hand, and in the main exhaust gas path 17, on the other, upstream of the exhaust gas aftertreatment element 7 and downstream of the branch 15. In this context, the two actuation elements 13, 13′ are preferably coupled to one another in opposite directions, with the result that on the basis of their actuation positions or actuation angles the exhaust gas mass flow can also be divided clearly into portions which add up overall to 100%. In this context it is also possible to determine the exhaust gas mass flow through the exhaust gas aftertreatment element 7 by determining the exhaust gas mass flow, preferably by means of a pressure loss variable, by means of the actuation element 13′ in the bypass path 9. If, in fact, this exhaust gas mass flow is known and at the same time the actuation position of the actuation element 13′ is known, it is in turn possible to use this to infer the actuation position of the actuation element 13 in the main exhaust gas path 17, from which it is in turn possible to infer the exhaust gas mass flow through the exhaust gas aftertreatment element 7. For reasons of construction space, it may be appropriate to provide a sensor system for acquiring an exhaust gas mass flow only in the region of the actuation element 13′ which is assigned to the bypass path 9.
Overall it becomes apparent that by means of the method, the exhaust gas aftertreatment system 3 and the internal combustion engine 1 it is possible to acquire in a very precise fashion an energy input into the exhaust gas aftertreatment element 7, with the result that it is possible, under operating conditions which are hazardous for the exhaust gas aftertreatment system 3, to conduct exhaust gas via the bypass path 9 and in doing so actuate the actuation device 11, with the result that the exhaust gas aftertreatment element 7 is enabled in a controlled fashion after a critical situation, or can be disabled in a controlled fashion when a critical situation occurs. In this context it is also to be noted that, in particular in the marine field, bypasses are in any case required around an exhaust gas aftertreatment system, with the result that no additional components are necessary to carry out the method. All that is necessary is to configure a means of actuating the actuation device 11 in such a way that said actuation device 11 is actuated, in particular adjusted, on the basis of the instantaneous energy input and the permissible energy input. Overall, it is therefore possible to prevent excessive ageing, damage or destruction of exhaust gas aftertreatment elements. Furthermore, an undesired emission of stored substances from an exhaust gas aftertreatment element can be prevented.

Claims

1-9. (canceled)

10. A method for operating an exhaust gas aftertreatment system, comprising the steps of:

determining a permissible energy input into at least one exhaust gas aftertreatment element of the exhaust gas aftertreatment system;

ascertaining an instantaneous energy input into the at least one exhaust gas aftertreatment element by ascertaining at least one energy input variable which characterizes the instantaneous energy input; and

actuating an actuation device which varies, a distribution of an exhaust gas mass flow to the at least one exhaust gas aftertreatment element and varies a bypass path that leads around the at least one exhaust gas aftertreatment element, as a function of the permissible energy input and the instantaneous energy input.

11. The method according to claim 10, including determining the permissible energy input as a function of at least one operating parameter of the at least one exhaust gas aftertreatment element.

12. The method according to claim 11, including determining the permissible energy input as a function of a soot charge of a particle filter, a reducing agent charge of an SCR catalytic converter and/or a hydrocarbon charge of a catalytic converter.

13. The method according to claim 10, wherein an exhaust gas mass flow through the at least one exhaust gas aftertreatment element and/or an exhaust gas temperature are/is ascertained as the energy input variable.

14. The method according to claim 13, including measuring the exhaust gas temperature upstream of the at least one exhaust gas aftertreatment element, downstream of the at least one exhaust gas aftertreatment element, and/or in the at least one exhaust gas aftertreatment element.

15. The method according to claim 10, including ascertaining the exhaust gas mass flow as a function of an instantaneous operating state of an internal combustion engine in combination with which the exhaust gas aftertreatment system is operated, as a function of a pressure loss variable across the at least one exhaust gas aftertreatment element, and/or as a function of a pressure loss variable across at least one actuation element of the actuation device.

16. An exhaust gas aftertreatment system, comprising:

at least one exhaust gas aftertreatment element;

a bypass path around the at least one exhaust gas aftertreatment element;

an actuation device, configured to selectively distribute an exhaust gas mass flow to the at least one exhaust gas aftertreatment element and the bypass path; and

a control device having determining means for determining a permissible energy input into the at least one exhaust gas aftertreatment element, ascertaining means for ascertaining an instantaneous energy input into the at least one exhaust gas aftertreatment element, and actuation means for actuating the actuation device, wherein the control device is configured to actuate the actuation device as a function of the permissible energy input and the instantaneous energy input.

17. The exhaust gas aftertreatment system according to claim 16, comprising a plurality of exhaust gas aftertreatment elements, including at least one first exhaust gas aftertreatment element and at least one second exhaust gas aftertreatment element are each assigned a separate bypass path and a separate actuation device.

18. The exhaust gas aftertreatment system according to claim 16, wherein the actuation device has precisely one actuation element for distributing the exhaust gas mass flow.

19. The exhaust gas aftertreatment system according to claim 16, wherein the actuation device has an actuation element in the bypass path and an actuation element upstream of the exhaust gas aftertreatment element, wherein the actuation elements are coupled to one another in opposite directions.

20. An internal combustion engine, comprising an exhaust gas aftertreatment system according to claim 16.