Method for operating a particulate filter in an exhaust aftertreatment system of a combustion engine

Abstract

A method for the operation of a particulate filter in an exhaust aftertreatment system of a combustion engine (200) with the following steps: set up (111, 116) a pressure difference model, which models a measured pressure difference (Δp) which drops across the particulate filter (210) as a function (220) of a volume flow ({dot over (V)}) through the particulate filter (210) with an offset value (a.sub.0, C); measure (120) multiple measurement values (245) for the pressure difference (Δp) at different volume flows ({dot over (V)}) and solve (130) the pressure difference model as a function of the pressure difference (Δp), whereby the offset value (a.sub.0, C) is also determined.

Claims

1. A method (100) for the operation of a particulate filter in an exhaust aftertreatment system of a combustion engine (200), the method comprising: setting up (111, 116), in an electronic computer, a pressure difference model, which models a measured pressure difference (Δp) which drops across the particulate filter (210) as a function (220) of a volume flow (V) through the particulate filter (210) with an offset value (ao, C); measuring, via a sensor, (120) multiple measurement values (245) for the pressure difference (Δp) at different volume flows (V); solving (130), via the electronic computer, the pressure difference model as a function of the pressure difference (Δp), whereby the offset value (ao, C) is also determined; and, controlling operation, via a controller, of the particulate filter based on the pressure difference (Δp) and the offset value (ao, C), wherein the pressure difference (Δp) that drops across the particulate filter (210) is modelled as a function of the volume flow (V), a pressure (p), and a temperature (T) in the particulate filter (210), and the pressure difference (Δp) is modelled by the following equation:
Δp=A.Math.T.sup.v.Math.V÷B.Math.V.sup.2.Math.p+C wherein Δp is the pressure difference (Δp), A, B and C are coefficients, wherein the coefficient Cis the offset value, T is the temperature in the particulate filter (210), Vis the volumetric flow (V) through the particulate filter (210), p is the density of the exhaust gas, and vis a constant exponent.

2. The method (100) according to claim 1, wherein the function (220) of the pressure difference (Δp) is an nth order polynomial.

3. The method (100) according to claim 2, wherein at least n measurement values (245) for the pressure difference (Δp) can be measured at different volume flows (V).

4. The method (100) according to claim 1, wherein the pressure difference model is solved recursively.

5. The method (100) according to claim 1, wherein at least two measurements for the pressure difference (Δp) are averaged.

6. The method (100) according to claim 1, wherein the volume flow (V), the pressure difference (Δp), the temperature (T) in the particulate filter (210) and a mass flow (m) through the particulate filter (210) are determined at at least three different operating points of the combustion engine (200).

7. The method (100) according to claim 1, wherein a maximum allowable volume flow (V.sub.max) is determined for a predetermined, maximum allowable pressure difference (Δp.sub.max) using the solved pressure difference model.

8. A non-transitory, machine-readable storage medium containing instructions that when executed on a computer cause the computer to control operation of a particulate filter in an exhaust aftertreatment system of a combustion engine (200), by: setting up (111, 116) a pressure difference model, which models a measured pressure difference (Δp) which drops across the particulate filter (210) as a function (220) of a volume flow (V) through the particulate filter (210) with an offset value (ao, C); measuring, via a sensor, (120) multiple measurement values (24S) for the pressure difference (Δp) at different volume flows (V); solving (130) the pressure difference model as a function of the pressure difference (Δp), whereby the offset value (ao, C) is also determined; and, controlling operation of the particulate filter based on the pressure difference (Δp) and the offset value (ao, C), wherein the pressure difference (Δp) that drops across the particulate filter (210) is modelled as a function of the volume flow (V), a pressure (p), and a temperature (T) in the particulate filter (210), and the pressure difference (Δp) is modelled by the following equation:
Δp=A.Math.T.sup.v.Math.V÷B.Math.V.sup.2.Math.p+C wherein Δp is the pressure difference (Δp), A, B and C are coefficients, wherein the coefficient Cis the offset value, Tis the temperature in the particulate filter (210), Vis the volumetric flow (V) through the particulate filter (210), p is the density of the exhaust gas, and vis a constant exponent.

9. An electronic control unit configured to control operation of a particulate filter in an exhaust aftertreatment system of a combustion engine (200), by: setting up (111, 116) a pressure difference model, which models a measured pressure difference (Δp) which drops across the particulate filter (210) as a function (220) of a volume flow (V) through the particulate filter (210) with an offset value (ao, C); measuring, via a sensor, (120) multiple measurement values (245) for the pressure difference (Δp) at different volume flows (V); solving (130) the pressure difference model as a function of the pressure difference (Δp), whereby the offset value (ao, C) is also determined, and controlling operation of the particulate filter based on the pressure difference (Δp) and the offset value (ao, C), wherein the pressure difference (Δp) that drops across the particulate filter (210) is modelled as a function of the volume flow (V), a pressure (p), and a temperature (T) in the particulate filter (210), and the pressure difference (Δp) is modelled by the following equation:
Δp=A.Math.T.sup.v.Math.V÷B.Math.V.sup.2.Math.p+C wherein Δp the pressure difference (Δp), A, B and C are coefficients, wherein the coefficient C is the offset value, T is the temperature in the particulate filter (210), V is the volumetric flow (V) through the particulate filter (210), p is the density of the exhaust gas, and v is a constant exponent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are represented in the drawings and are explained in more detail in the following description.

(2) FIG. 1 shows a schematic representation of a combustion engine with a particulate filter, which is used in a method according to an embodiment of the invention;

(3) FIG. 2 shows a schematic flow diagram of a method according to an embodiment of the invention;

(4) FIG. 3 shows averaging for measurements of the pressure difference and the volume flow based on volume flow intervals according to an exemplary embodiment of the invention; and

(5) FIGS. 4 and 5 illustrate an increase in model quality through a larger number of averaged measurement values.

DETAILED DESCRIPTION

(6) FIG. 1 shows a particulate filter 210 arranged downstream of a combustion engine 200. The pressure difference Δp that drops across the particulate filter 210 is modelled by a function 220.

(7) FIG. 2 shows a method 100 for the operation of the particulate filter 210 in an exhaust aftertreatment system of the combustion engine 200, which determines in particular an offset value of a pressure difference model during the operation of the combustion engine.

(8) In a first step 105, a query is made as to whether a first or a second differential pressure model should be chosen.

(9) If the first differential pressure model is selected, the method proceeds with step 111, if the second differential pressure model is selected, the method proceeds with step 116.

(10) In step 111, a pressure difference model is established, which models a measured pressure difference which drops across the particulate filter 210 as a function of a volume flow {dot over (V)} through the particulate filter 210 with an offset value a.sub.0, wherein the function 220 of the pressure difference Δp is an nth order polynomial of the volume flow {dot over (V)} according to equation (4).

(11) In the next step 121, multiple measured values for the pressure difference p are measured at different volume flows V.

(12) In the next step 131, the pressure difference model or the equation system is solved. Here, the offset value a.sub.0 is also determined.

(13) After step 131, in step 138 a maximum allowable volume flow {dot over (V)}.sub.max for a predetermined, maximum allowable pressure difference Δp.sub.max is determined using the solved pressure difference model. The engine controller ensures that the maximum allowable volume flow {dot over (V)}.sub.max is not exceeded.

(14) After step 138, the method returns to step 121, wherein the multiple measurement values for the pressure difference Δp are measured again at different volume flows {dot over (V)}. Here, the new measurements for the pressure difference Δp at different volume flows {dot over (V)} are averaged with the previously determined measurement values. Furthermore, the pressure difference model is solved recursively. Also, the maximum allowable volume flow {dot over (V)}.sub.max is determined iteratively.

(15) In step 116, a pressure difference model is established, which models a measured pressure difference which drops across the particulate filter 210 as a function of a volume flow {dot over (V)} through the particulate filter 210 with an offset value C, wherein the function 220 of the pressure difference Δp is given by equation 5. Here, the pressure difference Δp is modeled as a function of the volume flow {dot over (V)}, the pressure p and the temperature T in the particulate filter.

(16) In the next step 126, the volume flow {dot over (V)}, the pressure difference Δp, the temperature T in the particulate filter 210 and a mass flow {dot over (m)} through the particulate filter 210 are measured at six different operating points of the combustion engine 200.

(17) In the next step 136, the pressure difference model or the equation system is solved. The offset value C is also determined.

(18) After step 136, a maximum allowable volume flow {dot over (V)}.sub.max is determined in step 138 for a predetermined, maximum allowable pressure difference Δp.sub.max using the solved pressure difference model. In the engine controller, it is ensured that the maximum allowable volume flow {dot over (V)}.sub.max is not exceeded.

(19) After step 138, the method returns to step 126, wherein the multiple measurement values for the pressure difference Δp are measured again at different volume flows V. Here, the new measurements for the pressure difference Δp at different volume flows {dot over (V)} are averaged with the previously determined measurement values. Furthermore, the differential pressure model is solved recursively. Also, the maximum allowable volume flow {dot over (V)}.sub.max is determined.

(20) FIG. 3 shows measurement points for the pressure difference Δp measured across the particulate filter 210 as a function of the measured volume flow {dot over (V)}. Here, the pressure difference Δp is measured in units of hectopascals (hPa) and the volume flow {dot over (V)} in units of cubic meters per hour (m.sup.3/h). In FIG. 3, three volume flow intervals 230 are defined. If a measured volume flow {dot over (V)} is within one of these three volume flow intervals 230, the pressure difference Δp and volume flow {dot over (V)} are taken into account for the averaging of the corresponding volume flow interval 230. Once a predetermined minimum number of measured values has been recorded within a volume flow interval 230, this average is considered to be valid and may be used to determine the coefficients. For the three volume flow intervals 230, three valid average values 240 are plotted, using which a fit curve 250 of function 220 of the first pressure difference model was drawn.

(21) FIGS. 4 and 5, as well as FIG. 3, show measurement points for the pressure difference Δp measured across the particulate filter 210 as a function of the measured volume flow {dot over (V)}. In FIG. 4, the case is shown in which only three average values 240 were used for the fit curve 250, whereas in FIG. 5 four average values 240 were used. It can be clearly seen that the fit curve 250 in FIG. 5 is much better matched to the measured values 245 than in FIG. 4.