Method and system for protecting a particulate filter

Abstract

The present application relates to the protection method and system of the particle trap, when the differential pressure sensor fault does not appear, and the volume flow of tail gas does not exceed the flow limit value 1, the current flow resistance carbon load S2 is latched, and the low volume flow timer starts timing;When the low volume flow timing time exceeds the time limit value 1, the flow resistance carbon load of the particle trap is forced to release and starts timing, and the flow resistance carbon load S3 under the corresponding time window is obtained according to the pressure difference accumulation value P3 and the volume flow accumulation value M3 in the timing time period;When the timing time of the flow resistance carbon load release exceeds the time limit value 2, the current flow resistance carbon load S3 is latched, the larger value between S3 and S2 is taken as the final carbon load of the output, and the low volume flow timing time and the timing time of the flow resistance carbon load release are reset. The working condition that the flow resistance carbon load can not be released all the time is judged by the time under the continuous low tail gas flow, and the combustion deterioration condition that may occur is identified by forcing the flow resistance carbon load to release for a period of time.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of engine control technology, in particular to a method and system for protecting a particulate filter. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute the prior art.

[0003] A diesel particulate filter (DPF) is a component installed in the exhaust system of an engine, which filters and traps the particulate matter in the engine exhaust through diffusion, deposition and impaction mechanisms. The ability of a DPF to trap particulate matter is generally measured by carbon loading. The trapped particulate matter is divided into combustible and non-combustible parts. As the engine operates, the particulate matter accumulates inside the DPF, gradually reducing its ability to trap particulate matter. The combustible part of the particulate matter can be released through active regeneration or passive regeneration, thereby restoring the trapping capacity of the DPF (or carbon loading release).

[0004] Active regeneration usually occurs periodically by injecting a certain amount of fuel into the DPF, causing the combustible part of the particulate matter to react with oxygen and burn off the combustible part of the particulate matter, thereby restoring the particulate matter trapping capacity of the DPF. Passive regeneration, on the other hand, is achieved through engine thermal management measures or by operating the engine at a certain temperature, causing the combustible part of the particulate matter to react with NO2 at a lower temperature (generally 250-450°C). The particulate matter is oxidized to CO2, and NO2 is reduced to NO, thereby removing the particulate matter. This process occurs continuously. In actual operation, the DPF is usually combined with various technologies such as catalytic oxidation and exhaust gas recirculation to achieve standard exhaust emissions from the engine.

[0005] Both active regeneration and passive regeneration are means to restore the particulate matter trapping capacity of the DPF. To cope with as many operating conditions as possible, there are multiple conditions for triggering DPF regeneration, such as temperature, pressure difference, oxygen content, and flow resistance. In some poor operating conditions, if the exhaust gas volume flow is small, the DPF cannot use the flow resistance of the exhaust gas as a condition to trigger the release of particulate matter (regeneration). At this time, if combustion deteriorates and engine smoke increases, the model value of the control system for controlling the release of carbon loading by the DPF will deviate too much, causing the DPF to fail to trigger regeneration and posing a risk of DPF burnout. SUMMARY

[0006] To solve the technical problems in the background art, the present application provides a method and system for protecting a particulate filter, which judges that the running condition is too poor and the flow resistance carbon load cannot be released when the time under low exhaust flow is counted, and forcibly releases the flow resistance carbon load for a period of time when the time under low exhaust flow exceeds a limit value, so that the combustion deterioration can be timely identified and timely regeneration is performed to achieve the purpose of protecting the DPF.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] The first aspect of the present application provides a method for protecting a particulate filter, comprising the following steps:

[0009] The volume flow of engine exhaust and the state of the differential pressure sensor of the particulate filter are obtained, when no differential pressure sensor failure occurs and the volume flow of the exhaust does not exceed the flow limit value 1, the current flow resistance carbon load S2 is latched, and the low volume flow timer starts timing;

[0010] When the low volume flow timing time exceeds the time limit value 1, the flow resistance carbon load of the particulate filter is forcibly released and timing starts, and the flow resistance carbon load S3 under the corresponding time window is obtained according to the pressure difference cumulative value P3 and the volume flow cumulative value M3 in the timing period;

[0011] When the timing time of the flow resistance carbon load release exceeds the time limit value 2, the current flow resistance carbon load S3 is latched, the larger value between S3 and S2 is taken as the final carbon load of the output, and the low volume flow timing time and the timing time of the flow resistance carbon load release are reset.

[0012] Further, when no differential pressure sensor failure occurs and the volume flow of the exhaust does not exceed the flow limit value 1, the flow resistance value R1 is determined according to the pressure difference P1 and the exhaust volume flow M1 at this time, and the flow resistance carbon load S1 is obtained by looking up the table according to the flow resistance R1.

[0013] Further, the flow resistance value R1 is determined according to the pressure difference P1 and the exhaust volume flow M1 at this time, specifically: the pressure difference P1 is divided by the exhaust volume flow M1, and a factor obtained by looking up the table according to the temperature upstream of the particulate filter is corrected to calculate the flow resistance value R1.

[0014] Further, when the low volume flow timing time does not exceed the time limit value 1, the low volume flow timing time continues to be accumulated.

[0015] Further, the flow resistance carbon load of the particulate filter is forcibly released, specifically: the flow resistance carbon load of the particulate filter is released by active regeneration or passive regeneration.

[0016] Further, according to the pressure difference accumulated value P3 and the volume flow accumulated value M3 in the timing period, the flow resistance carbon load S3 in the corresponding time window is obtained, specifically: the flow resistance R3 in the time window is calculated by dividing the pressure difference accumulated value P3 by the volume flow accumulated value M3, and the flow resistance carbon load S3 is obtained by looking up the table according to the flow resistance R3 in the time window.

[0017] Further, the correction is specifically: the factor obtained by looking up the table according to the temperature upstream of the particulate filter is corrected.

[0018] Further, when the timing time of the flow resistance carbon load release does not exceed the time limit value 2, the timing time of the flow resistance carbon load release is continued to be accumulated.

[0019] Further, the control parameters of the particulate filter in the engine exhaust control system are updated by using the obtained final carbon load.

[0020] The second aspect of the present application provides a system for implementing the above-mentioned particulate filter protection method, comprising:

[0021] A volume flow sensor is configured to obtain the volume flow of the engine exhaust and send the volume flow to the processor;

[0022] A differential pressure sensor is configured to obtain the differential pressure of the particulate filter and output the differential pressure value and the corresponding fault state or normal state;

[0023] The processor is configured to: when there is no differential pressure sensor fault and the volume flow of the exhaust does not exceed the flow limit value 1, latch the current flow resistance carbon load S2, and start the low volume flow timer;

[0024] The processor is further configured to: when the low volume flow timing time exceeds the time limit value 1, forcibly release the flow resistance carbon load of the particulate filter and start timing, and according to the pressure difference accumulated value P3 and the volume flow accumulated value M3 in the timing period, obtain the flow resistance carbon load S3 in the corresponding time window;

[0025] The processor is further configured to: when the timing time of the flow resistance carbon load release exceeds the time limit value 2, latch the current flow resistance carbon load S3, take the larger value between S3 and S2 as the output final carbon load, and reset the low volume flow timing time and the timing time of the flow resistance carbon load release.

[0026] Compared with the prior art, the above one or more technical solutions have the following beneficial effects:

[0027] 1. By counting the time of low exhaust flow, the working condition that cannot trigger the release of carbon load by flow resistance is determined. When the time of low exhaust flow exceeds the limit, the carbon load is released for a period of time, which can identify the possible combustion deterioration and perform timely regeneration.

[0028] 2. By calculating the average value of the time window flow resistance R3 and increasing the correction of the temperature upstream of the DPF, the flow resistance carbon load S3 obtained by looking up the table with the time window flow resistance R3 ensures the accuracy of the carbon load calculation, and S3 and the flow resistance carbon load S2 latched before the release of the flow resistance carbon load S3 take the maximum value as the final carbon load, without using the original carbon load with deviation as the parameter to control the DPF, which can improve the differential pressure under low exhaust flow and protect the DPF from burning out. BRIEF DESCRIPTION OF DRAWINGS

[0029] The drawings constituting a part of the specification of the present application are used to provide a further understanding of the present application, the illustrative embodiments of the present application and the description thereof are used to explain the present application, and do not constitute an improper limitation on the present application.

[0030] Figure 1 is a schematic diagram of the protection process of the particulate matter trap provided by one or more embodiments of the present application. DETAILED DESCRIPTION

[0031] The present application will be further described below in conjunction with the drawings and embodiments.

[0032] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

[0033] It should be noted that the terms used herein are only for the purpose of describing the specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form, and in addition, it should be understood that when the terms "comprise" and / or "include" are used in the specification, they refer to the presence of a feature, step, operation, device, component and / or combination thereof.

[0034] Term explanation:

[0035] EGR, exhaust gas recirculation technology, separates part of the exhaust gas (exhaust gas) and introduces it into the intake side to participate in combustion again, which can reduce nitrogen oxides (NOx) in the exhaust gas and share part of the load, and can improve fuel consumption.

[0036] DOC, oxidation catalyst, a device that converts carbon monoxide (CO) and hydrocarbons (HC) in exhaust gas into harmless water (H2O) and carbon dioxide (CO2) through oxidation reaction.

[0037] DPF, diesel particulate filter, a device that traps particulate matter in exhaust gas of a diesel engine by a filter, and the trapped particulate matter is burned by exhaust gas temperature to be harmless, and the filter is regenerated.

[0038] SCR, selective catalytic reduction system, a device that reduces NO and NO2 into N2 by spraying a reducing agent NH3 into a processor under the action of a catalyst. The reducing agent NH3 is generally urea, which is stored in a container in liquid form and is referred to as ammonia storage in the following examples.

[0039] ASC, ammonia slip catalyst, a device that generally installed at the rear end of the SCR, reduces the ammonia (NH3) leaked in the exhaust gas at the rear end of the SCR by catalytic oxidation.

[0040] The above-mentioned EGR, DOC, DPF, SCR and ASC are components in the exhaust gas treatment system of a diesel engine. Different combinations of the above-mentioned components are used to meet the exhaust emission standards according to different exhaust emission standards.

[0041] Particulate matter, particulate matter contained in engine exhaust gas, generally includes soot and ash. Soot refers to the part that can be burned by regeneration, and ash refers to the non-combustible component that will accumulate in the DPF. When the accumulation reaches a certain amount, it needs to be removed and cleaned. Most of the particulate matter is the combustible part, so the accumulation of carbon in the DPF can be restored by regeneration, i.e. the carbon load is restored.

[0042] Flow resistance carbon load is a concept related to the carbon load in the DPF and the exhaust gas flow. It describes the resistance of the carbon load in the DPF to the exhaust gas flow at different exhaust gas flows. In this embodiment, the flow resistance carbon load refers to measuring and calculating the flow resistance (usually represented as the ratio of pressure difference to flow) when the exhaust gas passes through the particulate filter (DPF), and estimating and determining the current carbon accumulation (i.e. carbon load) in the DPF according to the pre-established relationship model or data table (MAP graph) between flow resistance and carbon load.

[0043] The Diesel Oxidation Catalysis (DOC) is a noble metal catalyst (such as Pt, etc.) coated on a carrier (such as honeycomb ceramic), which aims to reduce the chemical reaction activation energy of HC, CO and SOF in the engine exhaust, so that these substances can be oxidized at a lower temperature with oxygen in the exhaust and eventually converted into CO2 and H2O. The oxidation type catalytic converter does not require a regeneration system and control device, has the characteristics of simple structure and good reliability, and has been applied to some modern small engines.

[0044] The basic working principle of the particulate matter trapping system is that when the engine exhaust gas flows through the oxidation catalyst (DOC), CO and HC are first almost completely oxidized to CO2 and H2O, and NO is converted to NO2 at a temperature of 200-600°C. After the exhaust gas from the DOC enters the particulate trap (DPF), the particulates are trapped in the filter core of the filter body, and the remaining relatively clean exhaust gas is discharged into the atmosphere, and the trapping efficiency of the DPF can be more than 90%.

[0045] As the working time increases, the particulate matter accumulated on the DPF increases, which not only affects the filtering effect of the DPF, but also increases the exhaust back pressure, thereby affecting the engine breathing and combustion, resulting in reduced power output and increased fuel consumption. In the long-term operation of the DPF, the gradual increase of particulate matter in the trap will cause the engine back pressure to rise, resulting in a decrease in engine performance, so the deposited particulate matter needs to be removed regularly to restore the filtering performance of the DPF.

[0046] There are two methods for DPF regeneration: active regeneration and passive regeneration. Active regeneration refers to using external energy to increase the temperature in the DPF to make the particulate matter ignite and burn. When the pressure difference sensors before and after the DPF detect that the back pressure before and after the DPF is too large, it is considered that the carbon accumulation capacity of the DPF has been reached. At this time, external energy, such as injecting diesel before the DOC and burning, is used to increase the temperature in the DPF, so that the deposited particulate matter is oxidized and burned to achieve the purpose of regeneration. The temperature of the DPF rises to above 550°C, causing the trapped particulate matter to burn and restore the trapping capacity of the DPF. Passive regeneration refers to the use of NO2 as an oxidizing agent to remove the particulate matter in the particulate trap within a certain temperature range. NO2 has strong oxidizing ability to the trapped particulate matter, so it can be used as an oxidizing agent to remove the particulate matter in the particulate trap and generate CO2, and NO2 is reduced to NO, thereby achieving the purpose of removing the particulate matter. Passive regeneration does not require additional fuel, so the more times passive regeneration is performed during the life cycle of the DPF, the longer the period for active regeneration needs to be performed, and the less fuel the aftertreatment system consumes, thereby improving the overall fuel consumption of the engine.

[0047] As introduced in the background, in some poor working conditions, due to the small exhaust gas volume flow, the DPF cannot trigger the release of particulate matter (regeneration) by using the flow resistance carbon load as the judgment condition, at this time, if the combustion deteriorates, the engine smoke becomes large, which will make the model value of the control DPF release carbon load in the engine exhaust control system deviate too much, resulting in the DPF cannot be regenerated, and there is a risk of DPF burning out.

[0048] Therefore, the following embodiments give a protection method and system of the particulate matter trap, by counting the time under the condition of low exhaust gas flow, the working condition that cannot trigger the release by using the flow resistance carbon load is judged. When the counting time under the condition of low exhaust gas flow exceeds the limit value, the carbon load is forced to release for a period of time, which can timely identify the combustion deterioration and regenerate in time, so as to achieve the purpose of protecting the DPF.

[0049] Embodiment one:

[0050] The protection method of the particulate matter trap comprises the following steps:

[0051] The volume flow of the engine exhaust and the state of the differential pressure sensor of the particulate matter trap are obtained, when there is no differential pressure sensor failure and the volume flow of the exhaust gas does not exceed the flow limit value 1, the current flow resistance carbon load S2 is latched, and the low volume flow timer starts counting;

[0052] When the low volume flow counting time exceeds the time limit value 1, the flow resistance carbon load of the particulate matter trap is forced to release and starts counting, according to the pressure difference cumulative value P3 and the volume flow cumulative value M3 in the counting time period, the flow resistance carbon load S3 under the corresponding time window is obtained;

[0053] When the counting time of the flow resistance carbon load release exceeds the time limit value 2, the current flow resistance carbon load S3 is latched, the larger value between S3 and S2 is taken as the final carbon load of the output, and the low volume flow counting time and the counting time of the flow resistance carbon load release are reset.

[0054] As shown in Figure 1 When the engine is in the running state and there is no differential pressure sensor related failure, and at the same time the exhaust gas volume flow exceeds the flow limit value 1, the flow resistance value R1 is calculated according to the differential pressure P1 at this time divided by the volume flow M1, and the factor obtained by looking up the table according to the temperature upstream of the DPF is increased for correction. The flow resistance carbon load S1 is obtained by looking up the table according to the flow resistance R1. At this time, the low volume flow counting time is cleared.

[0055] When the exhaust gas volume flow is small, that is, the exhaust gas volume flow does not exceed the flow limit value 1, it is considered that the exhaust gas volume flow is low, then the current flow resistance carbon load S2 is latched, and the low volume flow timer starts counting.

[0056] When the low volume flow timing time exceeds the time limit value 1, the forced flow resistance carbon load release is triggered, the timer for triggering the flow resistance carbon load release starts timing, and the time window flow resistance R3 is calculated according to the pressure difference accumulated value P3 divided by the volume flow accumulated value M3 in the timing time period, and is corrected by increasing the factor obtained by looking up the table according to the temperature upstream of the DPF, and the flow resistance carbon load S3 is obtained by looking up the table according to the time window flow resistance R3; when the low volume flow timing time does not exceed the time limit value 1, the low volume flow timing time continues to be accumulated.

[0057] In the embodiment, the forced flow resistance carbon load release refers to forcibly releasing the flow resistance carbon load in the DPF by controlling the DPF to perform at least one active regeneration or passive regeneration.

[0058] When the flow resistance carbon load release timing time exceeds the time limit value 2, the current flow resistance carbon load S3 is latched, the larger value between S3 and S2 is taken as the final carbon load of the output, and the low volume flow timing time and the flow resistance carbon load release timing time are cleared; otherwise, the timing time of the flow resistance carbon load release continues to be accumulated.

[0059] In the above process, the time under the condition of continuous low exhaust gas flow is counted to determine the working condition in which the flow resistance carbon load cannot be released due to the excessively low exhaust gas flow. When the timing time under the condition of continuous low exhaust gas flow exceeds the limit value, the flow resistance carbon load is forcibly released for a period of time, which can timely identify the possible combustion deterioration and perform timely regeneration.

[0060] By calculating the time window flow resistance average value R3 and increasing the correction of the temperature upstream of the DPF, the flow resistance carbon load S3 obtained by looking up the table according to the time window flow resistance R3 ensures the accuracy of the carbon load calculation, and the larger value between S3 and the flow resistance carbon load S2 latched before the flow resistance carbon load release is taken as the final carbon load of the output, instead of using the original carbon load with deviation as the parameter for controlling the DPF, which can improve the pressure difference discrimination under the condition of low exhaust gas flow and protect the DPF from burning out.

[0061] Embodiment two:

[0062] The system of the method for protecting the particulate matter trap comprises:

[0063] A volume flow sensor is configured to acquire the volume flow of the engine exhaust gas and send the volume flow to the processor.

[0064] A differential pressure sensor is configured to acquire the differential pressure of the particulate matter trap and output a differential pressure value and a corresponding fault state or normal state.

[0065] The processor is configured to latch the current flow resistance carbon load S2 when no differential pressure sensor fault occurs and the volume flow of the exhaust gas does not exceed the flow limit value 1, and start timing of a low volume flow timer.

[0066] The processor is further configured to force release of the flow resistance carbon load of the particulate trap and start timing when the low volume flow metering time exceeds a time limit 1, and obtain the flow resistance carbon load S3 in the corresponding time window according to the pressure difference accumulation value P3 and the volume flow accumulation value M3 in the timing time period;

[0067] The processor is further configured to latch the current flow resistance carbon load S3 when the timing time of the flow resistance carbon load release exceeds a time limit 2, take the larger value between S3 and S2 as the final carbon load of the output, and reset the low volume flow metering time and the timing time of the flow resistance carbon load release.

[0068] By counting the time of the low exhaust flow, the working condition that the flow resistance carbon load cannot be released is determined. When the timing time of the low exhaust flow exceeds the limit, the flow resistance carbon load is forced to be released for a period of time, which can identify the possible combustion deterioration in time and perform timely regeneration.

[0069] By calculating the time window flow resistance average value R3 and adding the correction of the temperature upstream of the DPF, the flow resistance carbon load S3 obtained from the time window flow resistance R3 ensures the accuracy of the carbon load calculation, and the larger value between S3 and the flow resistance carbon load S2 latched before the release of the flow resistance carbon load is taken as the final carbon load, instead of using the original carbon load with deviation as the parameter for controlling the DPF, which can improve the pressure difference differentiation under the low exhaust flow and protect the DPF from burning out.

[0070] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of protecting a particulate filter, characterized by, The following steps are involved: The volume flow rate of the engine exhaust and the status of the differential pressure sensor of the particulate matter trap are obtained. When there is no differential pressure sensor failure and the volume flow rate of the exhaust does not exceed the flow limit 1, the current flow resistance carbon load S2 is latched and the low volume flow timer starts timing; When the low volume flow rate timing time exceeds the time limit 1, the flow resistance carbon load of the particulate matter trap is forcibly released and the timing starts. The flow resistance carbon load S3 in the corresponding time window is obtained according to the accumulated pressure difference P3 and the accumulated volume flow M3 during the timing period. When the timing time of the flow resistance carbon load release exceeds the time limit 2, the current flow resistance carbon load S3 is latched, the larger value between S3 and S2 is taken as the output final carbon load, and the low volume flow timing time and the flow resistance carbon load release timing time are reset.

2. The method of protecting a particulate filter as set forth in claim 1, characterized by, When there is no differential pressure sensor failure and the volume flow of the exhaust gas does not exceed the flow limit 1, the flow resistance value R1 is determined based on the pressure difference P1 and the exhaust gas volume flow M1 at this time, and the flow resistance carbon load S1 is obtained by looking up the flow resistance R1 in the table.

3. The method of protecting a particulate filter as set forth in claim 2, characterized by, The flow resistance R1 is determined based on the pressure difference P1 and the exhaust volume flow M1 at this time. Specifically, the pressure difference P1 is divided by the exhaust volume flow M1, and the flow resistance R1 is calculated by adding a factor obtained from the table of the particulate matter collector upstream temperature.

4. The method of protecting a particulate filter as set forth in claim 1, characterized by, When the low volume flow timing time does not exceed time limit 1, the low volume flow timing time continues to be accumulated.

5. The method of protecting a particulate filter as set forth in claim 1, characterized by, The flow resistance carbon load of the particulate matter trap is forcibly released, specifically: the flow resistance carbon load of the particulate matter trap is released through active regeneration or passive regeneration.

6. The method of protecting a particulate filter as set forth in claim 1, characterized by, According to the accumulated pressure difference value P3 and the accumulated volume flow value M3 within the timing time period, the flow resistance carbon load S3 in the corresponding time window is obtained. Specifically, the accumulated pressure difference value P3 within the timing time period is divided by the accumulated volume flow value M3, and the time window flow resistance R3 is calculated after correction. The flow resistance carbon load S3 is obtained by looking up the table of the time window flow resistance R3.

7. The method of protecting a particulate filter as set forth in claim 6, characterized by, The correction is specifically: the correction is made by adding a factor obtained by looking up the table of the temperature upstream of the particulate matter trap.

8. The method of protecting a particulate filter as set forth in claim 1, characterized by, When the flow resistance carbon load release timing time does not exceed the time limit 2, the flow resistance carbon load release timing time continues to be accumulated.

9. The method of protecting a particulate filter as in claim 1 wherein, The obtained final carbon load is used to update the control parameters of the particulate matter filter in the engine exhaust control system.

10. A protection system for a particulate filter, characterized in that include: A volume flow sensor is used to obtain the volume flow of engine exhaust and send it to the processor; A differential pressure sensor is used to obtain the pressure difference of the particulate matter trap and output the pressure difference value and the corresponding fault status or normal status; The processor is configured to: when no differential pressure sensor failure occurs and the volume flow rate of the exhaust gas does not exceed the flow limit value 1, latch the current flow resistance carbon load S2 and start the low volume flow timer; The processor is further configured to: when the low volume flow timing time exceeds the time limit 1, forcibly release the flow resistance carbon load of the particulate matter trap and start timing, and obtain the flow resistance carbon load S3 in the corresponding time window according to the accumulated pressure difference value P3 and the accumulated volume flow value M3 during the timing period; The processor is further configured to: when the time limit 2 is exceeded for the timing of the flow resistance carbon load release, latch the current flow resistance carbon load S3, take the greater value between S3 and S2 as the final carbon load of the output, and reset the low volume flow timing and the timing of the flow resistance carbon load release.

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