DE102018205072A1 - Method for operating an exhaust system for an internal combustion engine and corresponding exhaust system - Google Patents

Abstract

The invention relates to a method for operating an exhaust system (1) for an internal combustion engine, wherein the exhaust system (1) comprises an exhaust gas purification device (2) for purifying exhaust gas and a first exhaust gas pressure in a first exhaust partial line (7) upstream of the exhaust gas purification device (2) and a second exhaust gas pressure is detected in a second exhaust gas part line (8) downstream of the exhaust gas purification device (2) for calculating a state parameter of the exhaust gas purification device (2) influencing the pressure loss of the exhaust gas purification device (2). It is provided that a line pressure loss of the first exhaust pipe part (7) and / or the second exhaust pipe part (8) is determined and taken into account in the calculation of the state parameter. The invention further relates to an exhaust system (1) for an internal combustion engine.

Description

The invention relates to a method for operating an exhaust system for an internal combustion engine, wherein the exhaust system comprises an exhaust gas purification device for purifying exhaust gas and a first exhaust pressure in a first exhaust pipe upstream of the exhaust gas purification device and a second exhaust pressure in a second exhaust pipe downstream of the exhaust gas purification device for calculating the pressure loss the exhaust gas purification device influencing state parameter of the exhaust gas purification device are detected. The invention further relates to an exhaust system for an internal combustion engine.

From the prior art, for example, the publication DE 102 34 791 A1 known. This relates to a method for operating a particulate filter system, wherein the particulate filter flows through the exhaust gas of a self-igniting internal combustion engine, loaded with soot and regenerated in dependence on predetermined soot loading conditions of the particulate filter. It is provided that the operation of the particulate filter is further optimized by determining in addition to the soot loading of the particulate filter, the loading of deposited in the particulate filter, non-regenerable constituents of the exhaust gas and the particulate filter is maintained after a certain load.

It is an object of the invention to propose a method for operating an exhaust system for an internal combustion engine, which has advantages over known methods, in particular allows a more accurate determination of a state parameter of the exhaust gas purification device.

This is achieved according to the invention with a method for operating an exhaust system for an internal combustion engine with the features of claim 1. It is provided that a line pressure loss of the first exhaust pipe part and / or the second exhaust pipe part is determined and taken into account in the calculation of the state parameter.

The exhaust system is used to remove exhaust gases that are generated by the internal combustion engine. For this purpose, the exhaust system is supplied to the exhaust gas generated by the internal combustion engine and discharged via the exhaust system, in particular in the direction of an external environment. For example, the exhaust gas exits through an end pipe from the exhaust system. In terms of flow technology, the exhaust system is connected on the one hand to the internal combustion engine and on the other hand preferably to the outside environment.

The exhaust system has the exhaust gas purification device for purifying exhaust gas as well as the two exhaust gas sub-lines, namely the first exhaust partial line and the second exhaust partial line. The two exhaust partial pipes are part of an exhaust pipe of the exhaust system. The exhaust gas purification device is fluidically connected to the internal combustion engine via the first exhaust gas part line. The exhaust gas purification device is preferably in fluid communication with the outside environment via the second exhaust gas part line on its side facing away from the first exhaust part line.

The exhaust gas purification device is present, for example, as a particle filter, in particular as a soot particle filter. However, the exhaust gas purification device may also be in the form of another device which generally serves to purify the exhaust gas. The exhaust gas generated by the internal combustion engine contains particles, such as soot particles. These particles accumulate over time in the exhaust gas purification device. For example, in order to promptly initiate a regeneration of the exhaust gas purification device, during which the particles are discharged from the exhaust gas purification device, for example by oxidation, the state parameter of the exhaust gas purification device is determined.

The state parameter describes the pressure loss of the exhaust gas purification device or the pressure loss of the exhaust gas over the exhaust gas purification device. For determining the state parameter, first the first exhaust gas pressure and the second exhaust gas pressure are determined. The first exhaust gas pressure corresponds to the pressure of the exhaust gas in the first exhaust partial line and the second exhaust gas pressure corresponds to the pressure of the exhaust gas in the second exhaust gas partial line. It can be provided to detect the first exhaust gas pressure and the second exhaust gas pressure separately, in particular by means of a respective pressure sensor. However, it can also be provided that determining the first exhaust gas pressure and the second exhaust gas pressure takes place only in the form of detecting a differential pressure which describes the pressure difference between the first exhaust gas pressure and the second exhaust gas pressure or vice versa.

At least one of the two exhaust gas pressures, that is to say either the first exhaust gas pressure or the second exhaust gas pressure, or both exhaust gas pressures are determined by the exhaust gas purification device at a distance from the flow. Correspondingly, the difference between the two exhaust gas pressures does not directly include the pressure difference and therefore the pressure loss via the exhaust gas purification device, but additionally a pressure loss that occurs in the respective exhaust gas part line. Here is the Line pressure loss over the respective exhaust pipe part not or at most slightly dependent on the state parameter, whereas the pressure drop of the exhaust gas purification device itself has a pronounced dependence on the state parameter, which ultimately describes the loading of the exhaust gas purification device with particles.

In addition, the pressure loss of the exhaust gas purification device is dependent on an exhaust gas volume flow with which the exhaust gas flows through the exhaust system or the exhaust gas purification device. The dependence of the pressure loss of the exhaust gas purification device of the exhaust gas flow is largely linear. By contrast, the dependence of the line pressure loss on the exhaust gas volume flow is often of the second order, so that significant discrepancies between the course of the pressure loss of the exhaust gas purification device and the line pressure loss arise over the exhaust gas volume flow.

For this reason, it is now provided to determine the line pressure drop of the first exhaust partial line and / or the second exhaust partial line and to take into account in the calculation of the state parameter. The state parameter is thus present as a function of at least the line pressure loss, the first exhaust gas pressure and the second exhaust gas pressure. By taking account of the line pressure loss, a state parameter is obtained which is largely independent of the exhaust gas volume flow. It follows that the state parameter is constant over a wide range of exhaust gas flow rates. This ultimately means that the state parameter only has to be determined in the case of an exhaust gas volume flow, and the determined exhaust gas flow rate is meaningful even for exhaust gas flow rates that deviate from this exhaust gas volume flow.

For example, it is provided to initiate a regeneration of the exhaust gas purification device if the state parameter exceeds a certain state parameter threshold value. As part of the regeneration, for example, the exhaust gas temperature is increased such that the particles located in the exhaust gas purification device oxidize or burn off and are dissipated. The regeneration is carried out, for example, until the state parameter falls below a certain further state parameter threshold value.

Additionally or alternatively, it can be checked on the basis of the state parameter to a proper installation of the exhaust gas purification device. If, for example, the state parameter is too low, then it can be recognized that the exhaust gas purification device is not or at least not properly mounted or is fluidically connected to the exhaust gas sub-lines. If, on the other hand, the condition parameter exceeds the specific value, a proper arrangement of the exhaust-gas purification device is recognized.

On the one hand, the described procedure for operating the exhaust system or for determining the state parameter enables high accuracy in determining the state parameter. In addition, a substantial independence of the state parameter from the exhaust gas volume flow is achieved.

A further embodiment of the invention provides that the first exhaust gas pressure with a first pressure sensor and the second exhaust gas pressure with a second pressure sensor is measured or by means of a differential pressure sensor, the pressure difference between the first exhaust pressure and the second exhaust pressure is detected. The two pressure sensors, that is, the first pressure sensor and the second pressure sensor, so at least in fluid communication with the respective exhaust partial line at least. For example, the pressure sensors are in the respective exhaust partial line or at least project into this.

The use of the two pressure sensors has the advantage that the first exhaust gas pressure and the second exhaust gas pressure are determined with high accuracy, so that the finally determined state parameter is meaningful. The first pressure sensor is arranged upstream of the exhaust gas purification device and the second pressure sensor upstream of the exhaust gas purification device with respect to a direction of flow through the exhaust system or the first exhaust gas part line, the exhaust gas purification device and the second exhaust gas part line. If the differential pressure sensor is used, it is fluidically connected at a first connection point to the first exhaust gas part line and at a second connection point to the second exhaust part line. With regard to the arrangement of the connection points, the embodiments for the first pressure sensor on the first connection point and the versions for the second pressure sensor on the second connection point are each directly transferable.

At least one of the pressure sensors is fluidly arranged at a distance from the exhaust gas purification device, this preferably applies to both pressure sensors. Thus, the first pressure sensor is located a certain distance upstream of the exhaust gas purification device and the second pressure sensor is located a certain distance downstream of the exhaust gas purification device. Accordingly, a pressure loss in the first drops between the first pressure sensor and the exhaust gas purification device Exhaust part line and between the exhaust gas purification device and the second pressure sensor, a pressure drop in the second exhaust pipe part. These two pressure losses add up to the line pressure loss and are dependent on the exhaust gas volume flow and the respective distance of the pressure sensor to the exhaust gas purification device as well as parameters of the first exhaust partial line and the second exhaust partial line. The latter parameters of the exhaust partial lines can be taken into account, for example, via coefficients in calculating the line pressure loss. The above explanations apply analogously to the connection points which are present when using the differential pressure sensor.

A particularly preferred further embodiment of the invention provides that a particle loading of the exhaust gas purification device is used as the state parameter. The exhaust gas purification device is configured accordingly such that during the operation of the internal combustion engine contained in the exhaust gas particles remain in the exhaust gas purification device, so that the particle load of the exhaust gas purification device increases with time. The exhaust gas cleaning device is so far, for example, as a particle filter or the like. If the particle loading is too high, the pressure loss via the exhaust gas purification device becomes so high that the exhaust gas of the internal combustion engine can no longer be properly discharged via the exhaust gas system.

For this reason, the above-mentioned regeneration of the exhaust gas purification device is performed from time to time, during which the particle load is reduced. The consideration of the line pressure loss in determining the state parameter and thus the particle load allows a particularly reliable operation of the exhaust system and according to the internal combustion engine.

ermittelt werden, wobei Δp den Leitungsdruckverlust, p die Dichte des Abgases, ζ eine die Rohrreibung beschreibende dimensionslose Kennzahl und u die Strömungsgeschwindigkeit des Abgases ist. Mit der Kontinuitätsgleichung $$\dot{V}=uA$$

kann die Strömungsgeschwindigkeit in den Abgasvolumenstrom umgerechnet werden beziehungsweise umgekehrt. Insgesamt ergibt sich somit für den Leitungsdruckverlust die Beziehung $$\Delta p=\frac{1}{2}\rho \zeta \frac{{\dot{V}}^2}{A^2}$$

Within the scope of a further preferred embodiment of the invention it can be provided that the line pressure loss is determined by means of a model from an exhaust gas volume flow of the exhaust gas. In general, the line pressure loss from the relationship $$\Delta p=\frac{1}{2}\rho \zeta u^2$$

where Δp is the line pressure loss, p is the density of the exhaust gas, ζ is a dimensionless index describing the pipe friction, and u is the flow velocity of the exhaust gas. With the continuity equation $$\dot{V}=uA$$

the flow rate can be converted into the exhaust gas volume flow or vice versa. Overall, therefore, the relationship for the line pressure loss $$\Delta p=\frac{1}{2}\rho \zeta \frac{{\dot{V}}^2}{A^2}$$

berechnet werden, wobei λ die Rohrreibungszahl, L die Leitungslänge und D den hydraulischen Durchmesser der jeweiligen Abgasteilleitung beschreibt. Weil grundsätzlich auch weitere Einflüsse auf den Leitungsdruckverlust vorliegen können, wird dieser - zur Vereinfachung einer empirischen Kalibration - aus der Beziehung $$\Delta p_L=a_{L\mathrm{,1}}\dot{V}+a_{L\mathrm{,2}}{\dot{V}}^2$$

ermittelt, wobei a_L,1 und a_L,2 Koeffizienten sind, die empirisch ermittelt werden, beispielsweise während einer Kalibration der Abgasanlage. Die Verwendung einer derartigen Beziehung im Rahmen des Modells ermöglicht eine präzise Bestimmung des Leitungsdruckverlusts bei geringem Rechenaufwand.The pipe friction coefficient can in this case from the relationship $$\zeta =\lambda \frac{L}{D}$$

are calculated, where λ describes the pipe friction coefficient, L the line length and D the hydraulic diameter of the respective exhaust partial line. Because, in principle, other influences on the line pressure loss can be present, this - for the sake of simplification of an empirical calibration - from the relationship $$\Delta p_L=a_{L\mathrm{,1}}\dot{V}+a_{L2}{\dot{V}}^2$$

determined, where a _{L, 1} and a _{L, 2 are} coefficients that are determined empirically, for example, during a calibration of the exhaust system. The use of such a relationship within the model allows precise determination of line pressure loss with little computational effort.

A further development of the invention provides that, in calculating the condition parameter, a model pressure loss which is calculated for a pressure loss of the exhaust gas purification device corresponding to a minimum pressure loss of the exhaust gas purification device from the exhaust gas volume flow is additionally taken into account. In this respect, the model pressure loss describes, for example, the pressure loss of the exhaust gas purification device when new, ie, for example, immediately after the exhaust gas purification device has been installed in the exhaust gas system. It can also describe the pressure loss immediately after a regeneration of the exhaust gas purification device.

ermittelt, wobei a_P,1 und a_P,2 wiederum Koeffizienten sind, die empirisch ermittelt werden, beispielsweise während der Kalibration der Abgasanlage. Die Komponente zweiter Ordnung kann für die Abgasreinigungseinrichtung optional vernachlässigt werden. Eine derartige Vorgehensweise, insbesondere die Verwendung der genannten Beziehung für den Modelldruckverlust, ermöglicht die Bestimmung des Zustandsparameters mit hoher Genauigkeit bei gleichzeitig geringem Rechenaufwand.Analogous to the line pressure loss, the model pressure loss is only via the exhaust gas purification device based on the relationship $$\Delta p_{P.m}=a_{P\mathrm{,1}}\dot{V}+a_{P2}{\dot{V}}^2$$

where a _{P, 1} and a _{P, 2 are} again coefficients which are determined empirically, for example, during the calibration of the exhaust system. The second-order component may optionally be neglected for the exhaust gas purifier. Such a procedure, in particular the use of the above-mentioned relationship for the model pressure loss, makes it possible to determine the state parameter with high accuracy and, at the same time, low computation effort.

A further preferred embodiment of the invention provides that the model pressure loss is calculated by means of a relationship of at least first order and / or the line pressure loss by means of a second order relationship from the exhaust gas volume flow. As has already been pointed out above, the specific relationships have already been specified. Basically, the first-order relationship suffices for determining the model pressure loss. However, higher accuracy can be achieved by means of a least second order relationship. The same applies to the line pressure loss.

ermittelt wird, wobei Δp_g ein aus dem ersten Abgasdruck und dem zweiten Abgasdruck ermittelter Gesamtdruckverlust aus dem Druckverlust der Abgasreinigungseinrichtung und dem Leitungsdruckverlust, Δp_L der Leitungsdruckverlust und Δp_P,m der Modelldruckverlust ist. Vorstehend wurde bereits erläutert, dass der Leitungsdruckverlust und der Modelldruckverlust mit den folgenden Beziehungen ermittelt werden können: $$\Delta p_L=a_{L\mathrm{,1}}\dot{V}+a_{L\mathrm{,2}}{\dot{V}}^2$$

$$\Delta p_{P,m}=a_{P\mathrm{,1}}\dot{V}+a_{P\mathrm{,2}}{\dot{V}}^2$$

A further embodiment of the invention provides that the state parameter from the relationship $$a=\frac{\Delta p_G-\Delta p_L}{\Delta p_{P.m}}$$

where Δp _{g is} a total pressure loss determined from the first exhaust pressure and the second exhaust pressure from the exhaust gas purifier pressure loss and the line pressure loss, Δp _{L is} the line pressure loss and Δp _{P m is} the model pressure loss. It has already been explained above that the line pressure loss and the model pressure loss can be determined with the following relationships: $$\Delta p_L=a_{L\mathrm{,1}}\dot{V}+a_{L2}{\dot{V}}^2$$

$$\Delta p_{P.m}=a_{P\mathrm{,1}}\dot{V}+a_{P2}{\dot{V}}^2$$

Taking into account the state parameter, the pressure loss of the exhaust gas purification device results from the relationship $$\Delta p_{P.a}=a\Delta p_{P.m}=a\left(a_{P\mathrm{,1}}\dot{V}+a_{P2}{\dot{V}}^2\right)$$

If now the total pressure loss is compared to the sum of the model pressure loss and the line pressure loss, then the term results $$\frac{\Delta p_G}{\Delta p_L+\Delta p_{P.m}}$$

The total pressure loss is known and corresponds to the difference between the first exhaust pressure and the second exhaust pressure. In addition, it is equal to the sum of the line pressure loss and the model pressure loss multiplied by the state parameter. Consequently, the relationship arises $$\frac{\Delta p_G}{\Delta p_L+\Delta p_{P.m}}=\frac{\Delta p_L+\Delta p_{P.a}}{\Delta p_L+\Delta p_{P.m}}=\frac{\Delta p_L+a\Delta p_{P.m}}{\Delta p_L+\Delta p_{P.m}}$$

By shortening and changing the relationship finally results $$a=\frac{\Delta p_G-\Delta p_L}{\Delta p_{P.m}}$$

This relationship allows a simple and accurate determination of the state parameter with little computational effort.

Finally, within the scope of a further embodiment of the invention, it may be provided that values for the state parameter are determined for different exhaust gas volume flows and the state parameter is determined from these values. It is therefore intended to determine the state parameter at different exhaust gas flow rates, so that there is a value for the state parameter for each of the different exhaust gas volume flows. The determination of the state parameter takes place within the scope of this description. From the values for the state parameter, the state parameter itself is finally determined.

For example, the state parameter corresponds to an average of the values. However, it can also be provided that the deviation of the values from one another or from the mean value is determined and the state parameter is set equal to the value which has the smallest distance from all other values or the mean value. With such a procedure, the accuracy of the state parameter is further improved.

The invention further relates to an exhaust system for an internal combustion engine, in particular for carrying out the method according to the statements in this description, wherein the exhaust system comprises an exhaust gas purification device for purifying exhaust gas and a first exhaust gas pressure in a first exhaust pipe section upstream of the exhaust gas purification device and a second Exhaust gas pressure in a second exhaust pipe part downstream of the exhaust gas purification device for calculating a pressure loss of the exhaust gas purification device influencing state parameter of the exhaust gas purification device are detected. It is provided that the exhaust system is designed to determine a line pressure loss of the first exhaust pipe part and / or the second exhaust pipe part and to take into account in the calculation of the state parameter.

The advantages of such an approach or such an embodiment of the exhaust system has already been pointed out. Both the exhaust system and the method for its operation can be further developed according to the statements in the context of this description, so that reference is made to this extent.

A further embodiment of the invention provides that the exhaust gas purification device comprises a plurality of partial exhaust gas purification devices, which are fluidly arranged in parallel and connected in each case on the one hand to the first exhaust partial line and on the other hand to the second exhaust partial line. Between the first exhaust partial line and the partial exhaust gas purification devices, a branch is provided in this respect, as well as between the second exhaust partial line and the partial exhaust gas purification devices. In this respect, the exhaust gas flowing through the first exhaust gas part line is first of all fluidly divided between the several partial exhaust gas purification devices and subsequently combined again in the second exhaust gas partial line.

Preferably, the partial exhaust gas purification devices are identical. However, different configurations of the partial exhaust gas purification devices may also be provided. In particular, the splitting of the exhaust gas to the plurality of partial exhaust gas purification devices is associated with a high line pressure loss in the first exhaust partial line, so that without consideration of the line pressure loss strong deviations of the state parameter on the exhaust gas volume flow occur. Particularly in such an embodiment of the exhaust system with a plurality of partial exhaust gas purification devices, the consideration of the line pressure loss in the calculation of the state parameter results in a much higher accuracy and in a much better independence of the state parameter of the exhaust gas volume flow.

• 1 eine schematische Darstellung einer Abgasanlage für eine Brennkraftmaschine in einer zweiten Ausführungsform,
• 2 ein Diagramm, in welchem ein Druckverlauf für eine Abgasreinigungseinrichtung der Abgasanlage bei Vorliegen eines ersten Zustandsparameters und ein zweiter Druckverlauf bei Vorliegen eines zweiten Zustandsparameters gezeigt sind,
• 3 ein Diagramm, in welchem verschiedene Druckverläufe über einen Abgasvolumenstrom aufgetragen sind, sowie
• 4 ein Diagramm, in welchem der Zustandsparameter über dem Abgasvolumenstrom aufgetragen ist.

The invention will be explained in more detail with reference to the embodiments illustrated in the drawings, without any limitation of the invention. Showing:

• 1 a schematic representation of an exhaust system for an internal combustion engine in a second embodiment,
• 2 1 is a diagram in which a pressure curve for an exhaust gas purification device of the exhaust system in the presence of a first state parameter and a second pressure curve in the presence of a second state parameter are shown,
• 3 a diagram in which various pressure curves are plotted on an exhaust gas flow, and
• 4 a diagram in which the state parameter is plotted against the exhaust gas flow.

The 1 shows a schematic representation of an exhaust system 1 for an internal combustion engine, not shown. The exhaust system has an exhaust gas purification device 2 in the form of a particle filter 3 is present. The particle filter 3 has a filter substrate 4 on which in a housing 5 is arranged. Regarding one by the arrow 6 indicated flow direction upstream of the particulate filter 3 is a first exhaust partial line 7 and downstream of the particulate filter 3 a second exhaust pipe part 8th arranged fluidically. The two exhaust partial pipes 7 and 8th preferably each extend directly to the filter substrate 4 so that also the conical regions shown here upstream and downstream of the filter substrate 4 Part of the exhaust partial pipes 7 and 8th are.

The exhaust system 1 is assigned to an internal combustion engine not shown here, which generates exhaust gas during its operation. The exhaust gas generated by the internal combustion engine is the exhaust system 1 supplied and flows through this in the direction of the arrow 6 , To a pressure drop over the particle filter 3 and therefore the pressure loss of the exhaust gas purification device 2 to determine influencing state parameter is in the first exhaust partial line 7 at a first measuring point 9 a first exhaust pressure and in the second exhaust pipe part 8th on a second exhaust partial line 8th at a second measuring point 10 a second exhaust pressure determined. The two exhaust gas pressures cause a pressure difference between the measuring points 9 and 10 calculated. In the embodiment shown here are the two measuring points 9 and 10 to a differential pressure sensor 11 connected, which measures the pressure difference directly.

From the two exhaust gas pressures or the pressure difference is now the state parameter of the exhaust gas purification device 2 determined, namely taking into account a line pressure loss of the first exhaust partial line 7 and / or the second exhaust partial line 8th , The following relationship applies to this: $$a=\frac{\Delta p_G-\Delta p_L}{\Delta p_{P.m}}$$

beschrieben, wohingegen der Verlauf 13 von der Beziehung $$\Delta p_{P,a}+\Delta p_L=a\Delta p_{P,m}+\Delta p_L=a\left(a_{P\mathrm{,1}}\dot{V}+a_{P\mathrm{,2}}{\dot{V}}^2\right)+\Delta p_L$$

beschrieben wird. Es zeigt sich, dass sich die beiden Beziehungen lediglich um den Leitungsdruckverlust sowie einen Faktor unterscheiden, welcher dem Zustandsparameter a der Abgasreinigungseinrichtung 2 entspricht.The 2 shows a diagram in which a pressure loss Ap over an exhaust gas volumetric flow V is plotted. A first course 12 shows the total pressure loss with unloaded exhaust gas purifier 2 whereas the course 13 shows the total pressure loss at higher load. The history 12 will be at least approximately from the relationship $$\Delta p_{P.m}=+\Delta p_L=a_{P\mathrm{,1}}\dot{V}+a_{P2}{\dot{V}}^2+\Delta p_L$$

described, whereas the course 13 from the relationship $$\Delta p_{P.a}+\Delta p_L=a\Delta p_{P.m}+\Delta p_L=a\left(a_{P\mathrm{,1}}\dot{V}+a_{P2}{\dot{V}}^2\right)+\Delta p_L$$

is described. It can be seen that the two relationships differ only by the line pressure loss and a factor which corresponds to the state parameter a of the exhaust gas purification device 2 equivalent.

The 3 again shows a pressure drop over the exhaust gas flow. Here again are the courses 12 and 13 for the exhaust gas purification device 2 shown in unloaded and loaded condition. Furthermore shows a course 14 the line pressure loss in the exhaust partial pipes 7 and 8th , A course 15 finally describes the pressure loss of the exhaust gas purification device 2 in unloaded condition and a course 16 the pressure loss of the exhaust gas purification device 2 in loaded condition. The courses 15 and 16 arise from the progressions 12 and 13 , each less the course 14 , It turns out that the adjusted gradients 12 and 16 behave almost linearly over the exhaust gas mass flow V.

The 4 shows a diagram in which the state parameter of the exhaust gas purification device 2 is plotted above the exhaust gas volume flow. The history 17 shows the relationship between the pressure losses according to the courses 13 and 12 , the history 18 the course of the ratio of the pressure loss according to the courses 16 and 15 , It becomes clear that the course 18 remains largely constant over the exhaust gas volume flow, whereas the course 17 decreases with increasing exhaust gas volume flow.

The described method for operating the exhaust system 1 has the advantage that a very accurate determination of the state parameter with simultaneous low dependence on the exhaust gas volume flow takes place, so that a control and / or a regulation of the exhaust system can be carried out with high accuracy.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 10234791 A1 [0002]

Claims (10)

Method for operating an exhaust system (1) for an internal combustion engine, wherein the exhaust system (1) comprises an exhaust gas purification device (2) for purifying exhaust gas and a first exhaust gas pressure in a first exhaust partial line (7) upstream of the exhaust gas purification device (2) and a second exhaust gas pressure in a second exhaust pipe part (8) downstream of the exhaust gas purification device (2) for calculating a pressure loss of the exhaust gas purification device (2) influencing state parameter of the exhaust gas purification device (2) are detected, characterized in that a line pressure loss of the first exhaust pipe part (7) and / or the second exhaust pipe part (8) is determined and taken into account in the calculation of the state parameter. Method according to Claim 1 , characterized in that the first exhaust pressure with a first pressure sensor and the second exhaust pressure with a second pressure sensor is measured or by means of a differential pressure sensor, the pressure difference between the first exhaust pressure and the second exhaust pressure is detected. Method according to one of the preceding claims, characterized in that a particle loading of the exhaust gas purification device (2) is used as the state parameter. Method according to one of the preceding claims, characterized in that the line pressure loss is determined by means of a model from an exhaust gas volume flow of the exhaust gas. Method according to one of the preceding claims, characterized in that in the calculation of the state parameter additionally a model pressure loss is taken into account, which is calculated for a minimal pressure loss of the exhaust gas purification device (2) corresponding pressure loss of the exhaust gas purification device (2) from the exhaust gas volume flow. Method according to one of the preceding claims, characterized in that the model pressure loss is calculated by means of a relationship of at least first order and / or the line pressure loss by means of a second order relationship from the exhaust gas volume flow. Method according to one of the preceding claims, characterized in that the state parameter from the relationship $$a=\frac{\Delta p_G-\Delta p_L}{\Delta p_{P.m}}$$

where Δp _{g is} a total pressure loss determined from the first exhaust pressure and the second exhaust pressure from the pressure loss of the exhaust gas purification device (2) and the line pressure loss, Δp _{L is} the line pressure loss and Δp _{P m is} the model pressure loss. Method according to one of the preceding claims, characterized in that at different exhaust gas flow rates values for the state parameter are determined and from these values, the state parameter is determined. Exhaust system (1) for an internal combustion engine, in particular for carrying out the method according to one or more of the preceding claims, wherein the exhaust system (1) comprises an exhaust gas purification device (2) for purifying exhaust gas and a first exhaust gas pressure in a first exhaust partial line (7) upstream of Exhaust gas purification device (2) and a second exhaust gas pressure in a second exhaust part line (8) downstream of the exhaust gas purification device (2) for calculating a pressure loss of the exhaust gas purification device (2) influencing state parameter of the exhaust gas purification device (2) are detected, characterized in that the exhaust system (1) is designed to determine a line pressure loss of the first exhaust partial line (7) and / or the second exhaust partial line (8) and to take into account in the calculation of the state parameter. Exhaust system after Claim 9 , characterized in that the exhaust gas purification device (2) comprises a plurality of partial exhaust gas purification devices, which are fluidically arranged in parallel and connected on the one hand to the first exhaust pipe part (7) and on the other hand to the second exhaust pipe part (8).

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