Method and device for identifying ammonia leakage risk of exhaust gas treatment system, and motor vehicle

Abstract

The present application relates to a method and device for identifying ammonia leakage risk of an exhaust treatment system, and a motor vehicle. Temperature data of the exhaust treatment system within a set time period is obtained, and temperature distribution data is determined. When the upstream temperature of the selective catalytic reduction system meets a threshold value, the corresponding temperature proportion data meets a threshold value, and the corresponding ammonia conversion efficiency meets a threshold value, the corresponding working condition has ammonia leakage risk. When there is ammonia leakage risk, the upstream temperature of the selective catalytic reduction system is changed, heat management is performed, and the ammonia leakage amount under high-risk working conditions is controlled. By affecting the weight of factors affecting ammonia leakage, the corresponding judgment logic is established, the risk caused by ammonia leakage is accurately identified, and corresponding control adjustment is performed to improve the adaptability of the exhaust treatment control process.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas treatment technology, specifically to a method, device, and motor vehicle for identifying ammonia leakage risks in exhaust gas treatment systems. Background Technology

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

[0003] The exhaust gas produced by a diesel engine needs to be treated by an exhaust gas treatment system to meet emission standards. In this system, stored urea is used as a source of ammonia. Under certain temperature and catalyst conditions, various harmful substances in the exhaust gas are rendered harmless, such as converting NOx into nitrogen, carbon dioxide, and water, and burning particulate matter after it has been collected. However, in actual use, catalysts inevitably undergo regeneration, mild sulfur and phosphorus poisoning, and abnormally high temperatures under special circumstances. These situations can lead to varying degrees of efficiency reduction in the treatment effect, often manifested as a decrease in the ammonia conversion efficiency of SCR (Selective Catalytic Reduction) and ASC (Ammonia Slip Catalyst).

[0004] At the same time, catalysts have different catalytic capabilities depending on their formulations, which are usually reflected on the characteristic curve. In the sensitive area of ​​the catalyst's key characteristics, the conversion efficiency will also decrease. The decrease in ammonia conversion efficiency will cause false alarms from the NOx emission diagnostic system on the engine. In other words, the actual risk of NOx leakage is not high, but due to the combined effect of excessive ammonia leakage and the cross-sensitivity of the NOx sensor, the NOx sensor cannot distinguish whether the currently detected ammonia comes from NOx in the exhaust gas or from ammonia leakage. Summary of the Invention

[0005] To address the technical problems mentioned above, this invention provides a method, device, and vehicle for identifying ammonia leakage risks in exhaust gas treatment systems. Based on temperature distribution data and ammonia conversion efficiency under corresponding operating conditions, the invention identifies potential ammonia leakage risks and reduces these risks through appropriate control adjustments.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a method for identifying ammonia leakage risk in an exhaust gas treatment system, comprising the following steps:

[0008] Acquire temperature data from the exhaust gas treatment system within a set time period to determine temperature distribution data;

[0009] In the obtained temperature distribution data, when the upstream temperature of the selective catalytic reduction system meets the threshold, and the corresponding temperature percentage data meets the threshold, and the corresponding ammonia conversion efficiency meets the threshold, the corresponding operating condition has the risk of ammonia leakage.

[0010] When there is a risk of ammonia leakage, thermal management is implemented by changing the upstream temperature of the selective catalytic reduction system to control the amount of ammonia leakage under high-risk conditions.

[0011] Furthermore, when the upstream temperature of the selective catalytic reduction system meets the threshold, and the corresponding temperature percentage data meets the threshold, while the corresponding ammonia conversion efficiency meets the threshold, the corresponding operating condition presents a risk of ammonia leakage, specifically:

[0012] If the percentage of upstream temperatures of the selective catalytic reduction system that are lower than the first temperature setpoint exceeds the first percentage, and the percentage of upstream temperatures of the selective catalytic reduction system that exceed the second temperature setpoint is less than the second percentage, and the ammonia conversion efficiency of the selective catalytic reduction system decreases by the third set percentage compared to the reference value, then the corresponding operating condition poses a risk of ammonia leakage.

[0013] Furthermore, thermal management includes: changing the temperature; when the upstream temperature of the selective catalytic reduction system exceeds a threshold and remains so for a first set time period, and the corresponding ammonia conversion efficiency shows a trend of first decreasing and then increasing, thermal management is terminated.

[0014] Furthermore, thermal management also includes: if the ammonia conversion efficiency of the selective catalytic reduction system meets the threshold and continues to exceed the third set time period within the second set time period, then thermal management is terminated.

[0015] Furthermore, when there is a risk of ammonia leakage, the ammonia injection rate is adjusted. Specifically, the ammonia storage capacity is adjusted according to the corresponding operating conditions, and the ammonia injection rate is reduced. When the ammonia conversion efficiency returns to normal and begins to decline, the injection rate is restored.

[0016] A second aspect of the present invention provides an ammonia leakage risk identification device for an exhaust gas treatment system.

[0017] The data acquisition unit is used to acquire temperature data of the exhaust gas treatment system within a set time period and send it to the processor;

[0018] The processor is configured to receive temperature data acquired from the data acquisition unit and convert it into temperature distribution data.

[0019] The processor is also configured to: when the upstream temperature of the selective catalytic reduction system meets the threshold, and the corresponding temperature percentage data meets the threshold, and the corresponding ammonia conversion efficiency meets the threshold, the corresponding operating condition has a risk of ammonia leakage, and issue corresponding thermal management commands or ammonia injection quantity correction commands to control the ammonia leakage under high-risk operating conditions.

[0020] Furthermore, the thermal management instructions include: changing the temperature; when the upstream temperature of the selective catalytic reduction system exceeds a threshold and remains so for a first set time period, and the corresponding ammonia conversion efficiency shows a trend of first decreasing and then increasing, then exiting thermal management.

[0021] Furthermore, the thermal management instruction also includes: if the ammonia conversion efficiency of the selective catalytic reduction system meets the threshold and continues to exceed the third set time period within the second set time period, then the thermal management is terminated.

[0022] Furthermore, the ammonia injection rate correction command is as follows: adjust the ammonia storage capacity according to the corresponding operating conditions and reduce the ammonia injection rate. When the ammonia conversion efficiency returns to normal and begins to decline, resume injection.

[0023] A third aspect of the invention provides a motor vehicle equipped with the above-described device for identifying the risk of ammonia leakage from the motor vehicle's exhaust gas treatment system.

[0024] Compared with existing technologies, one or more of the above technical solutions have the following beneficial effects:

[0025] Based on the characteristics of the catalyst, the efficiency of the catalyst is judged to be normal by combining the temperature distribution data with the ammonia conversion efficiency under the corresponding operating conditions. If the catalyst is normal, and the efficiency inflection point occurs in the high-efficiency conversion range, it is determined that the false alarm is caused by ammonia leakage. Thus, the possible risk of ammonia leakage can be identified, and the risk of ammonia leakage can be reduced by thermal management or injection correction. Attached Figure Description

[0026] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0027] Figure 1 This is a schematic diagram illustrating the efficiency characteristics of a catalyst during exhaust gas treatment provided in one or more embodiments of the present invention.

[0028] Figure 2 This is a schematic diagram illustrating the efficiency reduction caused by ammonia leakage during tail gas treatment, provided by one or more embodiments of the present invention.

[0029] Figure 3 This is a schematic diagram of the ammonia leakage risk identification process of the exhaust gas treatment system provided in one or more embodiments of the present invention. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0031] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0032] Terminology Explanation:

[0033] EGR, or Exhaust Gas Recirculation, is a technology that separates a portion of the exhaust gas and introduces it into the intake side for combustion again. This reduces nitrogen oxides (NOx) in the exhaust gas and shares some of the load, thus improving fuel efficiency.

[0034] DOC, or oxidation catalytic converter, is a device that converts carbon monoxide (CO) and hydrocarbons (HC) in exhaust gas into harmless water (H2O) and carbon dioxide (CO2) through an oxidation reaction.

[0035] DPF, or Diesel Particulate Filter, uses a filter to collect particulate matter from diesel engine exhaust. The particulate matter collected on the filter is then burned off by the exhaust temperature to render it harmless, while the filter itself is regenerated.

[0036] SCR, or Selective Catalytic Reduction System, uses a catalyst to inject a reducing agent (NH3) into the processor, reducing NO and NO2 to N2. The reducing agent NH3 is typically urea, stored in liquid form in a container, referred to as ammonia storage in the following examples.

[0037] ASC, or ammonia escape catalyst, is typically installed after an SCR (Selective Catalytic Reduction) system. It is a device that reduces the amount of ammonia (NH3) leaking from the exhaust gas after the SCR system through catalytic oxidation.

[0038] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the scope of exemplary embodiments of the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0039] Diesel engine exhaust typically achieves emission standards using a technical route of EGR+DOC+DPF+SCR+ASC. To ensure effective exhaust treatment, excess ammonia (commonly urea as the ammonia source) is injected into the exhaust. To prevent excess ammonia from being released into the atmosphere, an ammonia escape catalytic converter (ASC) is used, with the help of a built-in catalyst, to convert excess ammonia into nitrogen. Different types of catalysts have different characteristic curves, such as... Figure 1 As shown, in the sensitive regions of the catalyst's key properties, this can lead to... Figure 2The decrease in ammonia conversion efficiency shown can cause false alarms in NOx emission diagnosis. In other words, the actual risk of NOx leakage is not high, but due to the combined effect of excessive ammonia leakage and the cross-sensitivity of NOx sensors, the NOx sensors cannot distinguish whether the currently detected ammonia comes from NOx in the exhaust gas or from ammonia leakage caused by excessive urea injection.

[0040] Therefore, the following embodiments provide a method, device and motor vehicle for identifying ammonia leakage risk in exhaust gas treatment systems. Considering that the nitrogen oxide sensor may identify NH3 as NOx due to cross-sensitivity, based on the characteristics of the catalyst, it is first determined whether the efficiency of the catalyst is normal. Under the premise that the catalyst is normal, if an efficiency inflection point occurs in the high-efficiency conversion range of the catalyst, it is determined that it is caused by ammonia leakage.

[0041] Example 1:

[0042] like Figures 1-2 As shown, the method for identifying ammonia leakage risk in an exhaust gas treatment system includes the following steps:

[0043] Acquire temperature data from the exhaust gas treatment system within a set time period to determine temperature distribution data;

[0044] In the obtained temperature distribution data, when the upstream temperature of the selective catalytic reduction system meets the threshold, and the corresponding temperature percentage data meets the threshold, and the corresponding ammonia conversion efficiency meets the threshold, the corresponding operating condition has the risk of ammonia leakage.

[0045] When there is a risk of ammonia leakage, thermal management is implemented by changing the upstream temperature of the selective catalytic reduction system to control the amount of ammonia leakage under high-risk conditions.

[0046] The following conditions are used to determine if there is a risk of ammonia leakage:

[0047] If the percentage of upstream temperatures of the selective catalytic reduction system that are lower than the first temperature setpoint exceeds the first percentage, and the percentage of upstream temperatures of the selective catalytic reduction system that exceed the second temperature setpoint is less than the second percentage, and the ammonia conversion efficiency of the selective catalytic reduction system decreases by the third set percentage compared to the reference value, then the corresponding operating condition poses a risk of ammonia leakage.

[0048] Thermal management includes: changing the temperature; when the upstream temperature of the selective catalytic reduction system exceeds the threshold and remains so for a first set time period, and the corresponding ammonia conversion efficiency shows a trend of first decreasing and then increasing, thermal management is terminated; or, within a second set time period, if the ammonia conversion efficiency of the selective catalytic reduction system meets the threshold and remains so for a third set time period, thermal management is terminated.

[0049] When there is a risk of ammonia leakage, the ammonia injection rate is adjusted. Specifically, the ammonia storage capacity is adjusted according to the corresponding operating conditions, and the ammonia injection rate is reduced. When the ammonia conversion efficiency returns to normal and begins to decline, the injection rate is restored.

[0050] In this embodiment, key feature quantities are extracted based on ammonia storage characteristics and ASC characteristic plots, with the following specific conditions:

[0051] Temperature distribution proportion characteristics: Statistically analyze the temperature proportion distribution over X hours (calibrated based on actual conditions) to obtain the temperature distribution proportion curve;

[0052] The criteria for judging the risk of ammonia leakage are: the percentage of SCR upstream temperatures <260℃ >80%, the percentage of SCR upstream temperatures >320℃ <5%, and the SCR conversion efficiency <threshold (e.g., a decrease of 15% to 20% compared with the reference value, especially the efficiency change characteristics with temperature, with a significant decrease in efficiency at certain temperatures, such as 280℃).

[0053] The specific threshold points or threshold ranges involved in the above judgment conditions, such as temperature, proportion, and conversion efficiency, can be determined according to the differences in characteristics such as ammonia storage and conversion efficiency brought about by different catalyst formulations. This embodiment is only for illustrative purposes.

[0054] If the above conditions are met, it is considered that there is a risk of ammonia leakage under the current operating conditions. The ammonia leakage control mode is then entered to perform thermal management or ammonia (urea) injection quantity correction, thereby eliminating the deviation of the control model, controlling the amount of ammonia leakage under high-risk operating conditions, and thus significantly improving the ammonia leakage handling capacity of ASC in the sensitive temperature range.

[0055] Thermal management and ammonia injection quantity correction are parallel processes. In this embodiment, thermal management is tried first. If the operating conditions cannot support the improvement of thermal management, then ammonia injection quantity correction is performed.

[0056] 1. Thermal management, specifically: increasing the temperature percentage to reduce the absolute deviation to a controllable range, with the following control conditions:

[0057] If the upstream temperature of the SCR is >320℃ and the duration is >Xmin, and the SCR conversion efficiency shows a trend of first decreasing and then increasing, it is determined that the deviation has been successfully eliminated and thermal management is terminated.

[0058] Alternatively, if the cumulative time for the SCR conversion efficiency to meet the threshold is >2Xmin within Y hours, the deviation is considered successfully eliminated, and thermal management is exited.

[0059] 2. Ammonia (urea) injection rate correction: Based on the current operating conditions, determine the deviation of the ammonia storage, adjust the set ammonia storage, and gradually reduce injection until the SCR efficiency first returns to normal and then begins to decline again, at which point injection is resumed. The ammonia injection rate is corrected using the coefficient of the gradual reduction as a reference.

[0060] This embodiment only considers the typical failure risks of ammonia leakage caused by the reduction of ammonia reserves due to conventional hydrothermal aging and the difference in ASC consistency. Other risks (such as those based on sulfur poisoning) are triggered by separate logic and will not be described in detail here.

[0061] The characteristics of ammonia storage and the efficiency of ASC determine the degree of differentiation of ammonia leakage under different ammonia storage conditions and temperatures. Combined with actual application conditions, the actual ammonia leakage risk can be accurately predicted and identified, and prevented and eliminated in conjunction with existing strategies.

[0062] Example 2:

[0063] This embodiment provides an ammonia leakage risk identification device for an exhaust gas treatment system to implement the above method, including:

[0064] The data acquisition unit is used to acquire temperature data of the exhaust gas treatment system within a set time period and send it to the processor;

[0065] The processor is configured to receive temperature data acquired from the data acquisition unit and convert it into temperature distribution data.

[0066] The processor is also configured to: when the upstream temperature of the selective catalytic reduction system meets the threshold, and the corresponding temperature percentage data meets the threshold, and the corresponding ammonia conversion efficiency meets the threshold, the corresponding operating condition has a risk of ammonia leakage, and issue corresponding thermal management commands or ammonia injection quantity correction commands to control the ammonia leakage under high-risk operating conditions.

[0067] Thermal management instructions include: changing the temperature; when the upstream temperature of the selective catalytic reduction system exceeds the threshold and continues for a first set time period, and the corresponding ammonia conversion efficiency shows a trend of first decreasing and then increasing, the thermal management is terminated.

[0068] Alternatively, if the ammonia conversion efficiency of the selective catalytic reduction system meets the threshold and continues to exceed the third set time period within the second set time period, thermal management will be terminated.

[0069] The ammonia injection rate correction command is as follows: adjust the ammonia storage capacity according to the corresponding operating conditions and reduce the ammonia injection rate. When the ammonia conversion efficiency returns to normal and begins to decline, resume injection.

[0070] Based on the characteristics of the catalyst, the efficiency of the catalyst is judged to be normal by combining the temperature distribution data with the ammonia conversion efficiency under the corresponding operating conditions. If the catalyst is normal, and the efficiency inflection point occurs in the high-efficiency conversion range, it is determined that the false alarm is caused by ammonia leakage. Thus, the possible risk of ammonia leakage can be identified, and the risk of ammonia leakage can be reduced by thermal management or injection correction.

[0071] Example 3:

[0072] This embodiment provides a motor vehicle equipped with the device described in Embodiment 2, used to identify the risk of ammonia leakage from the motor vehicle's exhaust gas treatment system.

[0073] Based on the characteristics of the catalyst, the efficiency of the catalyst is judged to be normal by combining the temperature distribution data with the ammonia conversion efficiency under the corresponding operating conditions. If the catalyst is normal, and the efficiency inflection point occurs in the high-efficiency conversion range, it is determined that the false alarm is caused by ammonia leakage. Thus, the possible risk of ammonia leakage can be identified, and the risk of ammonia leakage can be reduced by thermal management or injection correction.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for identifying ammonia leakage risk in an exhaust gas treatment system, characterized in that, Includes the following steps: Acquire temperature data from the exhaust gas treatment system within a set time period to determine temperature distribution data; In the obtained temperature distribution data, when the upstream temperature of the selective catalytic reduction system meets the threshold, and the corresponding temperature percentage data meets the threshold, and the corresponding ammonia conversion efficiency meets the threshold, the corresponding operating condition has the risk of ammonia leakage. When there is a risk of ammonia leakage, the amount of ammonia leakage under the risky operating conditions can be controlled by implementing thermal management or ammonia injection rate correction. Specifically, when the upstream temperature of the selective catalytic reduction system meets a threshold, the corresponding temperature percentage data meets a threshold, and the corresponding ammonia conversion efficiency meets a threshold, the corresponding operating condition presents a risk of ammonia leakage. The percentage of upstream temperatures of the selective catalytic reduction system that are lower than the first temperature setpoint exceeds the first percentage, and the percentage of upstream temperatures of the selective catalytic reduction system that exceed the second temperature setpoint is less than the second percentage, while the ammonia conversion efficiency of the selective catalytic reduction system decreases by the third set percentage compared to the reference value, at which point there is a risk of ammonia leakage in the corresponding operating condition. The thermal management process includes: changing the temperature; when the upstream temperature of the selective catalytic reduction system exceeds a threshold and remains so for a first set time period, and the corresponding ammonia conversion efficiency shows a trend of first decreasing and then increasing, the thermal management process is terminated. The ammonia injection quantity correction includes: adjusting the set ammonia storage quantity according to the corresponding operating conditions and reducing the ammonia injection quantity; when the ammonia conversion efficiency returns to normal and begins to decline, the injection is resumed.

2. An ammonia leak risk identification device for a tail gas treatment system, the device being used to perform the method of claim 1, characterized in that, include: The data acquisition unit is used to acquire temperature data of the exhaust gas treatment system within a set time period and send it to the processor; The processor is configured to receive temperature data acquired from the data acquisition unit and convert it into temperature distribution data. The processor is also configured to: when the upstream temperature of the selective catalytic reduction system meets the threshold, and the corresponding temperature percentage data meets the threshold, and the corresponding ammonia conversion efficiency meets the threshold, the corresponding operating condition has a risk of ammonia leakage, and issue a corresponding thermal management command or ammonia injection quantity correction command to control the amount of ammonia leakage under the risky operating condition.

3. The ammonia leakage risk identification device for the exhaust gas treatment system as described in claim 2, characterized in that, Thermal management instructions include: changing the temperature; when the upstream temperature of the selective catalytic reduction system exceeds the threshold and remains so for a first set time period, and the corresponding ammonia conversion efficiency shows a trend of first decreasing and then increasing, then exiting thermal management.

4. The ammonia leakage risk identification device for the exhaust gas treatment system as described in claim 2, characterized in that, The ammonia injection rate correction command is as follows: adjust the ammonia storage capacity according to the corresponding operating conditions and reduce the ammonia injection rate. When the ammonia conversion efficiency returns to normal and begins to decline, resume injection.

5. A motor vehicle, characterized in that, A device for identifying ammonia leakage risk in an exhaust gas treatment system as described in any one of claims 2-4.

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