METHOD FOR FLUSHING AN EXHAUST-GAS CLEANING SYSTEM

Abstract

A method for flushing an exhaust-gas cleaning system of an internal combustion engine having a catalytic converter with at least one catalyst bed, whereby an exhaust gas from the internal combustion engine is supplied to the exhaust-gas cleaning system in an active operating phase of the exhaust-gas cleaning system, and no exhaust gas is supplied to the exhaust-gas cleaning system in a passive operating phase of the exhaust-gas cleaning system, whereby a temperature of the at least one catalyst bed is determined and the flushing is performed depending on the determined temperature, whereby the exhaust-gas cleaning system is flushed in the passive operating phase of the exhaust-gas cleaning system by a flushing device, which is connected directly to an exhaust-gas line.

Claims

1. A method for flushing an exhaust-gas cleaning system of an internal combustion engine comprising a catalytic converter with at least one catalyst bed, wherein an exhaust gas from the internal combustion engine is supplied to the exhaust-gas cleaning system in an active operating phase of the exhaust-gas cleaning system, and no exhaust gas is supplied to the exhaust-gas cleaning system in a passive operating phase of the exhaust-gas cleaning system, wherein a temperature of the at least one catalyst bed is determined and the flushing is performed depending on the determined temperature, wherein the exhaust-gas cleaning system is flushed in the passive operating phase of the exhaust-gas cleaning system by a flushing device, which is connected directly to an exhaust-gas line.

2. The method according to claim 1, wherein the exhaust-gas cleaning system is flushed only in the passive operating phase of the exhaust-gas cleaning system.

3. The method according to claim 1, wherein the temperature of the at least one catalyst bed is determined in the passive operating phase of the exhaust-gas cleaning system.

4. The method according to claim 1, wherein the exhaust-gas cleaning system is flushed after a shutdown of the internal combustion engine.

5. The method according to claim 1, wherein a period of time during which the exhaust-gas cleaning system is flushed is determined depending on the determined temperature.

6. The method according to claim 1, wherein the exhaust-gas cleaning system is flushed before a start-up of the internal combustion engine.

7. The method according to claim 1, wherein the exhaust-gas cleaning system is flushed until the temperature of the at least one catalyst bed is lower than or equal to a predetermined setpoint temperature.

8. The method according to claim 7, wherein the exhaust-gas cleaning system is flushed if the temperature of the at least one catalyst bed before flushing is higher than or equal to a predetermined threshold value E.

9. The method according to claim 1, wherein a first exhaust-gas temperature value is determined upstream of the catalytic converter and a second exhaust-gas temperature value is determined downstream of the catalytic converter, wherein the temperature of the at least one catalyst bed is determined by taking account of the first exhaust-gas temperature value and the second exhaust-gas temperature value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Further details and advantages of this invention are explained in more detail below in the description of the figures, with reference to the exemplary embodiments shown in the drawings. The figures show the following:

[0021] FIG. 1 shows an internal combustion engine with an exhaust-gas cleaning system,

[0022] FIG. 2 shows a flowchart relating to the flushing of an exhaust-gas cleaning system after the shutdown of an internal combustion engine,

[0023] FIG. 3 shows a flowchart relating to the flushing of an exhaust-gas cleaning system before the start-up of an internal combustion engine.

DETAILED DESCRIPTION

[0024] FIG. 1 shows an internal combustion engine 4, in the exhaust-gas line 5 of which an exhaust-gas cleaning system 3 is arranged. The internal combustion engine 4 in this example is a stationary gas engine, which is operated with a fuel-gas/air mixture. The exhaust-gas cleaning system 3 comprises a catalytic converter 1, which in this example is equipped with two catalyst beds 2. Upstream of the exhaust-gas cleaning system 3, a flushing device 6 is arranged, through which the air L can be introduced into the exhaust-gas line 5 upstream of the exhaust-gas cleaning system 3 in order to flush the exhaust-gas cleaning system 3.

[0025] According to the proposed method, the exhaust-gas cleaning system 3 is flushed depending on a determined temperature T of the catalyst beds 2 of the catalytic converter 1. To determine the temperature T in this example, two temperature sensors 7, 8 are arranged upstream and downstream of the exhaust-gas cleaning system 3. The temperature sensors 7, 8 determine the temperature of the exhaust gas of the internal combustion engine 4. The temperature sensor 7 detects a first exhaust-gas temperature value T1 upstream of the catalytic converter 1, and the temperature sensor 8 determines a second exhaust-gas temperature value T2 downstream of the catalytic converter 1. The determined exhaust-gas temperature values T1, T2 are reported via signal lines 10 to a control device 9, which determines an estimated temperature T of the catalyst beds 2 from the first exhaust-gas temperature value T1 and the second exhaust-gas temperature value T2. This determination of the temperature T of the catalyst beds 2 can be performed e.g. by calculating the arithmetic mean of the first exhaust-gas temperature value T1 and the second exhaust-gas temperature value T2, or e.g. further calculations are performed, taking into account the caloric influencing variables, the response times of the measurement signal chains and the operating history. Depending on the determined temperature T, the control device 9 can activate the flushing device 6 via a control line 11 in order to introduce air L upstream of the exhaust-gas cleaning system 3 into the exhaust-gas line 5, thereby flushing the exhaust-gas cleaning system 3.

[0026] FIG. 2 shows, by way of example, a flowchart relating to the flushing of the exhaust-gas cleaning system 3 after the shutdown of an internal combustion engine 4. Starting from step S1, in which the internal combustion engine runs and supplies exhaust gas to the exhaust-gas cleaning system 3, whereby the exhaust-gas cleaning system 3 is in an active operating phase, a stop command for stopping the internal combustion engine 4 is initiated in step S2. Accordingly, the internal combustion engine 4 is stopped in step S3. As a result, no further exhaust gas from the internal combustion engine 4 is fed into the exhaust-gas cleaning system 3, and the exhaust-gas cleaning system 3 is in a passive operating phase in step S4. In this passive operating phase of the exhaust-gas cleaning system 3, the temperature T of the at least one catalyst bed 2 of the catalytic converter 1 of the exhaust-gas cleaning system 3 is now determined in step S5. In step S6, a period of time tp is determined depending on the determined temperature T of the at least one catalyst bed 2, during which the exhaust-gas cleaning system 3 is flushed in step S7.

[0027] FIG. 3 shows, by way of example, a flowchart for the flushing of the exhaust-gas cleaning system 3 before the start-up of an internal combustion engine 4. In step S8, a passive operating phase of the exhaust-gas cleaning system 3 is then assumed, which may be caused by the fact that the internal combustion engine 4 is not running. In step S9, the start command for starting the internal combustion engine 4 is executed. In step S10, it is checked whether the start command was preceded by a false start of the internal combustion engine 4, or whether the internal combustion engine 4 was previously shut down (e.g. within a predefined period). If a false start has not occurred and the internal combustion engine 4 was not shut down recently, the temperature T of the at least one catalyst bed 2 of the catalytic converter 1 of the exhaust-gas cleaning system 3 is determined in step S11. In step S12, it is checked whether the determined temperature T of the at least one catalyst bed 2 is lower than or equal to a setpoint temperature value TS. If this is not the case and the temperature T is higher than the setpoint temperature value TS, then the exhaust-gas cleaning system 3 is flushed in step S13, and in step S11 the determination of the temperature T of the at least one catalyst bed 2 is continued. If it is found in step S12 that the temperature T of the at least one catalyst bed 2 is lower than or equal to the setpoint temperature TS, then the internal combustion engine 4 can be started in step S14. By starting the internal combustion engine 4, an exhaust gas from the internal combustion engine 4 is fed into the exhaust-gas cleaning system 3, and the exhaust-gas cleaning system 3 is in an active operating phase in step S15.

[0028] If it is determined in step S10 that a false start of the internal combustion engine 4 has previously occurred, or the internal combustion engine 4 was shut down recently, the temperature T of the at least one catalyst bed 2 is determined in step S16, and in step 17 it is checked whether the temperature T of the at least one catalyst bed 2 is higher than or equal to a threshold value TT. If this is the case and thus the temperature T is higher than or equal to the threshold value TT, then we continue in step S12. If this is not the case and thus the temperature T is lower than the threshold value TT, then a safety flush of the exhaust-gas cleaning system 3 is performed in step S18. The exhaust-gas cleaning system 3 can thus be flushed for a fixed predetermined duration of e.g. 30 to 225 seconds, depending on the size of the exhaust tract. After this safety flush in step S18, step S14 (starting of the internal combustion engine 4) is continued.

[0029] This written description uses examples to disclose the invention, including the preferred embodiments, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.