CN113417726A - Method for detecting ammonia leakage of aftertreatment system and controller of aftertreatment system - Google Patents

Method for detecting ammonia leakage of aftertreatment system and controller of aftertreatment system Download PDF

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Publication number
CN113417726A
CN113417726A CN202110713043.4A CN202110713043A CN113417726A CN 113417726 A CN113417726 A CN 113417726A CN 202110713043 A CN202110713043 A CN 202110713043A CN 113417726 A CN113417726 A CN 113417726A
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conversion efficiency
ammonia
scr
aftertreatment system
controlling
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CN113417726B (en
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耿磊
滕佳新
袁志玲
王远景
孙志江
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Weichai Power Co Ltd
Weichai Power Emission Solutions Technology Co Ltd
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Weichai Power Co Ltd
Weichai Power Emission Solutions Technology Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N9/00—Electrical control of exhaust gas treating apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
    • F01N2560/026—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting NOx
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

The invention relates to a detection method for ammonia leakage of an after-treatment system and a controller of the after-treatment system, wherein the detection method comprises the following steps: controlling an SCR of an aftertreatment system to spray urea or reducing agent ammonia to tail gas of a vehicle when a working condition is detected; controlling the ammonia nitrogen ratio of urea or reducing agent ammonia to tail gas to be less than 1, and calculating the first conversion efficiency of SCR; controlling the ammonia nitrogen ratio of urea or reducing agent ammonia to tail gas to be not less than 1 according to the condition that the first conversion efficiency is within the first conversion efficiency threshold value, and calculating the second conversion efficiency of the SCR; and judging that the ammonia leakage occurs in the after-treatment system according to the fact that the second conversion efficiency is smaller than the second conversion efficiency threshold value. According to the method for detecting ammonia leakage of the aftertreatment system, the SCR can be judged to be in a normal working state through the first conversion efficiency within the first conversion efficiency threshold, so that the influence of SCR abnormity on ammonia leakage is reduced, and then whether the aftertreatment system has ammonia leakage is judged through the second conversion efficiency.

Description

Method for detecting ammonia leakage of aftertreatment system and controller of aftertreatment system
Technical Field
The invention relates to the technical field of vehicles, in particular to a method for detecting ammonia leakage of an aftertreatment system and a controller of the aftertreatment system.
Background
This section provides background information related to the present disclosure only and is not necessarily prior art.
The existing vehicle aftertreatment system sprays reducing agent ammonia or urea into the vehicle exhaust through SCR (selective catalytic reduction) under the action of a catalyst, and reduces NOx in the exhaust into N through the reducing agent ammonia or urea2And H2However, in the case of an abnormality in the aftertreatment system, the ammonia in the reducing agent or urea leaks, i.e., a part of the ammonia in the reducing agent or urea is discharged to the atmosphere without reacting with NOx, resulting in atmospheric pollution.
In order to detect whether the ammonia leakage phenomenon occurs in the aftertreatment system, the ammonia leakage phenomenon occurs in the aftertreatment system is generally judged according to the conversion efficiency of SCR (technology) on NOx, but the conversion efficiency of NOx is influenced by the failure of SCR and the ammonia leakage phenomenon in the aftertreatment system, so that a certain error exists in the judgment of the ammonia leakage phenomenon in the aftertreatment system according to the conversion efficiency of NOx.
Disclosure of Invention
The invention provides a method for detecting ammonia leakage of an aftertreatment system and a controller of the aftertreatment system, aiming at least solving the technical problem that SCR (selective catalytic reduction) abnormity affects the detection accuracy of the ammonia leakage, and the aim is realized by the following technical scheme:
the invention provides a method for detecting ammonia leakage of an aftertreatment system, which comprises the following steps: controlling an SCR of an aftertreatment system to spray urea or reducing agent ammonia to tail gas of a vehicle when a working condition is detected; controlling the ammonia nitrogen ratio of urea or reducing agent ammonia to tail gas to be less than 1, and calculating the first conversion efficiency of SCR; controlling the ammonia nitrogen ratio to be more than or equal to 1 and calculating the second conversion efficiency of the SCR according to the condition that the first conversion efficiency is within the first conversion efficiency threshold value; and judging that the ammonia leakage occurs in the after-treatment system according to the fact that the second conversion efficiency is smaller than the second conversion efficiency threshold value.
According to the method for detecting ammonia leakage of the aftertreatment system, the SCR can be judged to be in a normal working state through the first conversion efficiency within the first conversion efficiency threshold, so that the influence of SCR abnormality on ammonia leakage is reduced, and then whether the aftertreatment system has ammonia leakage is judged through the second conversion efficiency, so that the reliability of the detection method is improved.
Further, the detection working condition comprises a common working condition of the vehicle, and the common working condition specifically comprises: the engine of the vehicle outputs a rotational speed corresponding to the maximum torque, and the upstream temperature interval of the SCR is 300-400 ℃.
Further, controlling the ammonia nitrogen ratio of the urea or the reducing agent ammonia to the exhaust gas to be less than 1, and calculating the first conversion efficiency of the SCR comprises: the ammonia-nitrogen ratio is controlled to be 0.7, and the first conversion efficiency of the SCR is calculated according to nitrogen oxides detected by nitrogen-oxygen sensors at the upstream and downstream of the SCR.
Further, controlling the ammonia nitrogen ratio to be greater than or equal to 1, and calculating the second conversion efficiency of the SCR comprises: the ammonia-nitrogen ratio is controlled to be 1, and the second conversion efficiency of the SCR is calculated according to nitrogen-oxygen compounds detected by nitrogen-oxygen sensors at the upstream and downstream of the SCR.
Further, the first conversion efficiency threshold specifically includes: and under the condition that the ammonia nitrogen ratio is less than 1, respectively calculating the conversion efficiency of the SCR in a fresh state and an aged state, thereby obtaining an upper limit value and a lower limit value of a first conversion efficiency threshold value.
Further, the second conversion efficiency threshold specifically includes: and under the condition that the ammonia nitrogen ratio is more than or equal to 1, respectively calculating the conversion efficiency of the SCR in a fresh state and an aged state, thereby obtaining an upper limit value and a lower limit value of a second conversion efficiency threshold value.
Further, controlling the ammonia nitrogen ratio of the urea or the reducing agent ammonia to the tail gas to be less than 1, and calculating the first conversion efficiency of the SCR, and then: judging that the SCR has a degradation fault according to the condition that the first conversion efficiency is smaller than a first conversion efficiency threshold value; and determining that the SCR has the fault of excessive injection of urea according to the condition that the first conversion efficiency is greater than the first conversion efficiency threshold value.
Further, determining that ammonia slip in the aftertreatment system occurs according to the second conversion efficiency being less than the second conversion efficiency threshold specifically comprises: and judging that the leaked ammonia reacts with a downstream nitrogen-oxygen sensor of the SCR to generate nitrogen-oxygen compounds according to the fact that the second conversion efficiency is smaller than a second conversion efficiency threshold value.
Further, determining that ammonia slip has occurred in the aftertreatment system based on the second conversion efficiency being less than the second conversion efficiency threshold further comprises: and judging that the post-treatment system has a serious ammonia leakage phenomenon and triggering an ammonia leakage alarm according to the fact that the difference value between the second conversion efficiency threshold value and the second conversion efficiency is larger than a preset difference value.
A second aspect of the present invention provides a controller of an aftertreatment system, the controller including a device for detecting ammonia leakage of the aftertreatment system and a computer-readable storage medium, the computer-readable storage medium storing control instructions, the device implementing the method for detecting ammonia leakage of the aftertreatment system according to the first aspect of the present invention by executing the control instructions, the device comprising: the control module is used for controlling the SCR of the aftertreatment system to spray urea or reducing agent ammonia to tail gas of the vehicle when the working condition is detected; the control module is also used for controlling the ammonia nitrogen ratio of urea or reducing agent ammonia to tail gas to be less than 1, and the detection device also comprises a calculation module used for calculating the first conversion efficiency of the SCR; the control module is also used for controlling the ammonia nitrogen ratio to be more than or equal to 1 according to the condition that the first conversion efficiency is within the first conversion efficiency threshold value, and the calculation module is also used for calculating the second conversion efficiency of the SCR; and the judging module is used for judging that the ammonia leakage occurs in the aftertreatment system according to the condition that the second conversion efficiency is smaller than the second conversion efficiency threshold.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
FIG. 1 is a schematic flow diagram of a method for detecting ammonia slip in an aftertreatment system in accordance with one embodiment of the invention;
FIG. 2 is a schematic flow diagram of a method for detecting ammonia slip in an aftertreatment system according to another embodiment of the invention;
FIG. 3 is a schematic diagram of a controller of an aftertreatment system in accordance with one embodiment of the invention;
wherein the reference numbers are as follows:
10. a controller; 11. a computer-readable storage medium; 12. a detection device; 121. a control module; 122. a calculation module; 123. and a judging module.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
It is to be understood that the terminology used herein is for the purpose of describing particular example embodiments only, and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprising," "including," and "having" are inclusive and therefore specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof.
Although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "first," "second," and "third," as well as other numerical terms, are not used herein to imply a sequence or order unless clearly indicated by the context. In addition, in the description of the present invention, unless otherwise explicitly specified or limited, the terms "disposed" and "connected" are to be construed broadly, e.g., as a fixed connection, a removable connection, or an integral connection; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
For convenience of description, spatially relative terms, such as "upper", "inner", "close", and the like, may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" or "over" the other elements or features. Thus, the example term "below … …" can include both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
It should be noted that the SCR described in the embodiments of the present invention is also referred to as selective catalytic reduction technology, and the technology is a treatment process for NOx in the exhaust emission of a motor vehicle, i.e. under the action of a catalyst, a reducing agent ammonia or urea is injected to reduce NOx in the exhaust to N2And H2O。
In addition, the ammonia nitrogen ratio in the embodiment of the invention is the ratio of the reducing agent ammonia or urea injected by the aftertreatment system to the NOx in the exhaust gas, and under the condition that the ammonia nitrogen ratio is less than 1, because the amount of the reducing agent ammonia or urea is less than the amount of the NOx in the exhaust gas, the reducing agent ammonia or urea can be fully mixed and reacted with the NOx in the exhaust gas, at this time, the probability of leakage of the reducing agent ammonia or urea is very low, and under the condition that the ammonia nitrogen ratio is not less than 1, because the amount of the reducing agent ammonia or urea is not less than the amount of the NOx in the exhaust gas, at this time, the phenomenon that the reducing agent ammonia or urea is not uniformly mixed with the NOx in the exhaust gas, so that the phenomenon that the reducing agent ammonia or urea is not fully mixed and reacted with the NOx in the exhaust gas, and leaks may occur.
As shown in FIG. 1, a first aspect of the present invention provides a method for detecting ammonia slip in an aftertreatment system, the method comprising the steps of: s10, controlling the SCR of the aftertreatment system to spray urea or reducing agent ammonia to the tail gas of the vehicle when the working condition is detected; s20, controlling the ammonia nitrogen ratio of urea or reducing agent ammonia to tail gas to be less than 1, and calculating the first conversion efficiency of SCR; s30, controlling the ammonia nitrogen ratio to be more than or equal to 1 according to the fact that the first conversion efficiency is within the first conversion efficiency threshold value, and calculating the second conversion efficiency of the SCR; and judging that the ammonia leakage occurs in the after-treatment system according to the fact that the second conversion efficiency is smaller than the second conversion efficiency threshold value.
In this embodiment, the method for detecting ammonia leakage of the aftertreatment system provided by the invention can determine that the SCR is in a normal operating state through the first conversion efficiency being within the first conversion efficiency threshold, so as to reduce the influence of the SCR abnormality on ammonia leakage, and then determine whether the aftertreatment system has ammonia leakage through the second conversion efficiency, thereby improving the reliability of the detection method of the invention.
Further, the detection working condition comprises a common working condition of the vehicle, and the common working condition specifically comprises: the engine of the vehicle outputs a rotational speed corresponding to the maximum torque, and the upstream temperature interval of the SCR is 300-400 ℃.
In the embodiment, the detection working condition is usually an economic interval of vehicle operation and is a common working condition, taking a 10L engine as an example, the rotating speed corresponding to the maximum torque output by the engine is 1000rpm-1400rpm, and in addition, whether the ammonia leakage phenomenon occurs in the aftertreatment system is detected under the common working condition, so that the practicability of the detection method for detecting the ammonia leakage of the aftertreatment system is improved.
Further, in the embodiment of the present invention, the ammonia nitrogen ratio of the urea or the reducing agent ammonia to the exhaust gas is controlled to be less than 1, including a plurality of ratios with the ammonia nitrogen ratio of less than 1, in the embodiment of the present invention, the ammonia nitrogen ratio is preferably 0.7, specifically, the ammonia nitrogen ratio is controlled to be 0.7, and the first conversion efficiency of the SCR is calculated according to the nitrogen oxides detected by the upstream and downstream nitrogen oxide sensors of the SCR, the upstream nitrogen oxide detected by the upstream nitrogen oxide sensor is the nitrogen oxide which is not treated in the exhaust gas, the downstream nitrogen oxide detected by the downstream nitrogen oxide sensor is the nitrogen oxide which is treated by the SCR in the exhaust gas, and the first conversion efficiency of the SCR at the ammonia nitrogen ratio of 0.7 can be calculated according to the upstream nitrogen oxide amount and the downstream nitrogen oxide amount.
Further, in the embodiment of the present invention, the ammonia nitrogen ratio of urea or reducing agent ammonia to the exhaust gas is controlled to be greater than or equal to 1, including a plurality of ratios of the ammonia nitrogen ratio to 1, in the embodiment of the present invention, the ammonia nitrogen ratio is preferably 1, specifically, the ammonia nitrogen ratio is controlled to be 1, and the second conversion efficiency of the SCR is calculated according to the detected nitrogen oxides of the upstream and downstream nitrogen oxide sensors of the SCR, the upstream nitrogen oxide detected by the upstream nitrogen oxide sensor is an untreated nitrogen oxide in the exhaust gas, the downstream nitrogen oxide detected by the downstream nitrogen oxide sensor is a nitrogen oxide treated by the SCR in the exhaust gas, and the second conversion efficiency of the SCR at the ammonia nitrogen ratio of 1 can be calculated according to the upstream nitrogen oxide amount and the downstream nitrogen oxide amount.
Further, the first conversion efficiency threshold specifically includes: and under the condition that the ammonia nitrogen ratio is less than 1, respectively calculating the conversion efficiency of the SCR in a fresh state and an aged state, thereby obtaining an upper limit value and a lower limit value of a first conversion efficiency threshold value.
In this embodiment, the SCR in the fresh state is in the normal operating state, the conversion efficiency is high, the conversion efficiency of the SCR in the fresh state is calculated, the upper limit value of the first conversion efficiency threshold can be obtained, the SCR in the aging state is in the low-efficiency operating state, the conversion efficiency is low, the conversion efficiency of the SCR in the aging state is calculated, the lower limit value of the first conversion efficiency threshold can be obtained, the first conversion efficiency threshold can be obtained through the upper limit value and the lower limit value of the first conversion efficiency threshold, the rationality of the first conversion efficiency threshold is improved, the misjudgment of the failure of the SCR is reduced, and specifically, the SCR in the aging state can simulate the SCR aged for 30 kilometers quickly.
Further, the second conversion efficiency threshold specifically includes: and under the condition that the ammonia nitrogen ratio is more than or equal to 1, respectively calculating the conversion efficiency of the SCR in a fresh state and an aged state, thereby obtaining an upper limit value and a lower limit value of a second conversion efficiency threshold value.
In this embodiment, the SCR in the fresh state is in the normal operating state, the conversion efficiency is high, the conversion efficiency of the SCR in the fresh state is calculated, the upper limit value of the second conversion efficiency threshold can be obtained, the SCR in the aging state is in the low-efficiency operating state, the conversion efficiency is low, the conversion efficiency of the SCR in the aging state is calculated, the lower limit value of the second conversion efficiency threshold can be obtained, the second conversion efficiency threshold can be obtained through the upper limit value and the lower limit value of the second conversion efficiency threshold, the rationality of the second conversion efficiency threshold is improved, the misjudgment of the failure of the SCR is reduced, and specifically, the SCR in the aging state can simulate the SCR aged for 30 kilometers quickly.
Further, controlling the ammonia nitrogen ratio of the urea or the reducing agent ammonia to the tail gas to be less than 1, and calculating the first conversion efficiency of the SCR, and then: judging that the SCR has a degradation fault according to the condition that the first conversion efficiency is smaller than a first conversion efficiency threshold value; and determining that the SCR has the fault of excessive injection of urea according to the condition that the first conversion efficiency is greater than the first conversion efficiency threshold value.
In the embodiment, when the SCR has the fault of excessive urea injection, the ECU of the engine timely corrects the injection quantity of the urea, controls the injected urea in a reasonable range corresponding to the tail gas, and then calculates the first conversion efficiency of the SCR.
Further, determining that ammonia slip in the aftertreatment system occurs according to the second conversion efficiency being less than the second conversion efficiency threshold specifically comprises: and judging that the leaked ammonia reacts with a downstream nitrogen-oxygen sensor of the SCR to generate nitrogen-oxygen compounds according to the fact that the second conversion efficiency is smaller than a second conversion efficiency threshold value.
In this embodiment, the key innovation of the present invention is the nitrogen oxygen sensor to ammonia (NH)3) Presence of cross-sensitivity, i.e. NH3When the NOx sensor exists, the NOx value measured by the nitrogen oxygen sensor is higher, and the measured value of the downstream nitrogen oxygen sensor is abnormally higher, so that the two reasons are generally only two: one is degradation of the SCR, resulting in reduced conversion efficiency; the other is NH in the tail gas3And (4) leakage. According to the invention, the phenomenon that the measured value of the downstream nitrogen-oxygen sensor is abnormally high due to the reduction of the SCR efficiency is eliminated by designing the detection process, so that the occurrence of NH in the post-processing system can be judged according to the abnormally high measured value of the downstream nitrogen-oxygen sensor3And (4) leakage.
Further, determining that ammonia slip has occurred in the aftertreatment system based on the second conversion efficiency being less than the second conversion efficiency threshold further comprises: and judging that the post-treatment system has a serious ammonia leakage phenomenon and triggering an ammonia leakage alarm according to the fact that the difference value between the second conversion efficiency threshold value and the second conversion efficiency is larger than a preset difference value.
In this embodiment, if the difference between the lower limit of the second conversion efficiency threshold and the second conversion efficiency is not less than 2%, it indicates that serious NH occurs in the aftertreatment system3Leakage phenomenon, at which point NH is triggered3Leakage over-standard alarm is given to remind the owner to maintain the post-processing system as soon as possible, and NH is reduced3And (4) environmental pollution caused by leakage.
Referring to FIG. 2, the method for detecting ammonia slip in an aftertreatment system according to an embodiment of the invention is described in detail as follows:
1) detecting the working condition: the detection working condition is the rotating speed corresponding to the maximum torque of the engine, the temperature interval of the SCR upstream is 300-400 ℃ for temperature exhaust, the temperature interval is usually an economic interval and is a common working condition, a 10L engine is taken as an example, and the rotating speed of the engine corresponding to the maximum torque is 1000-1400 rpm.
2) Pre-calibration MAP 1: in the fresh state of the SCR, the ammonia-to-nitrogen ratio is 0.7, and the conversion efficiency of the SCR is f1 (the measured conversion efficiency of the SCR is calculated by measuring NOx by an upstream nitrogen-oxygen sensor and a downstream nitrogen-oxygen sensor), see Table 1, where X is the engine speed and Y is the temperature upstream of the SCR.
TABLE 1 conversion efficiency f1 of SCR in fresh state at 0.7 ammonia-to-nitrogen ratio
Y\X 1000 1100 1200 1300 1400
300 f1 f1 f1 f1 f1
320 f1 f1 f1 f1 f1
340 f1 f1 f1 f1 f1
360 f1 f1 f1 f1 f1
380 f1 f1 f1 f1 f1
400 f1 f1 f1 f1 f1
2) Pre-calibration MAP 2: simulating 30 kilometres of rapidly aged SCR, the SCR in an aged state has an ammonia-nitrogen ratio of 0.7, and the conversion efficiency of the SCR at this time is f2 (the measured conversion efficiency of the SCR is calculated by measuring NOx by an upstream nitrogen-oxygen sensor and a downstream nitrogen-oxygen sensor), as shown in Table 2, X is the engine speed, and Y is the upstream temperature of the SCR.
TABLE 2 conversion efficiency f2 for SCR in the aged state at 0.7 ammonia nitrogen ratio
Y\X 1000 1100 1200 1300 1400
300 f2 f2 f2 f2 f2
320 f2 f2 f2 f2 f2
340 f2 f2 f2 f2 f2
360 f2 f2 f2 f2 f2
380 f2 f2 f2 f2 f2
400 f2 f2 f2 f2 f2
3) Pre-calibration MAP 3: in the fresh state of the SCR, the ammonia to nitrogen ratio is 1, and the conversion efficiency of the SCR is f3 (the measured conversion efficiency of the SCR is calculated by measuring NOx by an upstream nitrogen-oxygen sensor and a downstream nitrogen-oxygen sensor), see Table 3, where X is the engine speed and Y is the temperature upstream of the SCR.
TABLE 3 conversion efficiency f3 of SCR in fresh state at 1 Ammonia to Nitrogen ratio
Figure BDA0003133718140000091
4) Pre-calibration MAP 4: in the aged SCR, the ammonia-to-nitrogen ratio is 1, and the SCR conversion efficiency is f4 (the measured SCR conversion efficiency is calculated from the measurement of NOx by the upstream and downstream NOx sensors), see table 4, where X is the engine speed and Y is the SCR upstream temperature.
See Table 4 conversion efficiency f4 for an aged SCR at 1 Ammonia to Nitrogen ratio
Figure BDA0003133718140000092
The method for detecting ammonia leakage of the aftertreatment system comprises the following steps: when the engine operates in a common working condition, namely a rotating speed range corresponding to the maximum torque, and the upstream temperature of the SCR is 300-400 ℃, the rotating speed and the torque at the moment are fixed, a detection device for detecting ammonia leakage of the aftertreatment system sends detection information to the ECU, and the ECU controls the SCR to execute an open-loop ammonia nitrogen ratio mode.
In the first step, the ammonia-nitrogen ratio of urea or reducing agent ammonia to exhaust gas is controlled to be 0.7, the time is timed for 150s, the NOx value measured by the SCR upstream/downstream nitrogen-oxygen sensor is recorded, the average NOx value measured by the SCR upstream/downstream nitrogen-oxygen sensor at 120s-150s is calculated, and then the conversion efficiency f0 of the SCR is calculated, wherein f0 is (A-B)/A. If f0 is larger than f1, the SCR conversion efficiency is abnormal high, urea is likely to be sprayed more, and a urea multi-spraying fault alarm is triggered; if f0 < f2, SCR degradation is indicated, and an SCR degradation fault alarm is triggered. If f2 is not less than f0 is not less than f1, the SCR efficiency is normal, and the subsequent diagnosis is continued. If the timer does not reach 150s for a special reason, the interrupt exit is detected.
Wherein: when A is 0.7 ammonia nitrogen ratio, the average NOx value measured by an upstream nitrogen oxygen sensor of SCR of 120s-150s is unit ppm; and B is 0.7 ammonia-nitrogen ratio, and the average NOx value measured by a nitrogen-oxygen sensor at the downstream of the SCR of 120s-150s is unit ppm.
And secondly, sending detection information to the ECU by the detection device for ammonia leakage of the aftertreatment system, changing the open-loop ammonia-nitrogen ratio to be 1 by the ECU, and recording the NOx value measured by the upstream/downstream nitrogen-oxygen sensor of the SCR. The average NOx value measured by the SCR upstream/downstream NOx sensors at 120s-150s was calculated, and the conversion efficiency f 0', f0 ═ (C-D)/C was calculated. If f4 is not less than f 0' is not less than f3, the SCR conversion efficiency is normal, and the diagnosis is finished; if f 0' < f4, that is, in the case where the SCR efficiency is normal when the ammonia nitrogen ratio is detected at 0.7, the SCR conversion efficiency detected when the ammonia nitrogen ratio is 1 is low, and the SCR deteriorates, indicating the presence of NH3Leakage, triggering NH3And (5) leakage fault alarm. If (f4-f 0'). gtoreq.100%. gtoreq.2%, NH is indicated3Severe breakthrough, triggering NH3And (5) alarming for exceeding the standard.
Wherein: when C is 1 ammonia-nitrogen ratio, the average NOx value measured by a nitrogen-oxygen sensor at the upstream of SCR of 120s-150s is unit ppm; d is the ammonia nitrogen ratio of 1, the average NOx value measured by a nitrogen oxygen sensor at the downstream of SCR of 120s-150s is measured in ppm.
As shown in fig. 3, a second aspect of the present invention provides a controller 10 of an aftertreatment system, the controller 10 includes a detection device 12 for detecting ammonia leakage of the aftertreatment system and a computer-readable storage medium 11, a control instruction is stored in the computer-readable storage medium 11, the detection device 12 implements a method for detecting ammonia leakage of the aftertreatment system according to the first aspect of the present invention by executing the control instruction, and the detection device 12 includes: the control module 121 is used for controlling the SCR of the aftertreatment system to inject urea or reducing agent ammonia to the tail gas of the vehicle when the working condition is detected; the control module is further used for controlling the ammonia nitrogen ratio of urea or reducing agent ammonia to tail gas to be less than 1, and the detection device further comprises a calculation module 122 for calculating the first conversion efficiency of SCR; the control module is also used for controlling the ammonia nitrogen ratio to be more than or equal to 1 according to the condition that the first conversion efficiency is within the first conversion efficiency threshold value, and the calculation module is also used for calculating the second conversion efficiency of the SCR; and a determination module 123 configured to determine that ammonia slip has occurred in the aftertreatment system based on the second conversion efficiency being less than the second conversion efficiency threshold.
In this embodiment, the controller of the aftertreatment system has all the technical effects of the method for detecting ammonia leakage of the aftertreatment system according to the invention, and will not be described herein again.
In addition, the device for detecting ammonia slip in the aftertreatment system provided by the invention can be integrated in the ECU module or be a separate device, and the device for detecting ammonia slip in the aftertreatment system and the ECU can communicate and exchange data, and NH is detected3An alarm alert may be triggered when a leak occurs.
Those skilled in the art will understand that all or part of the steps in the method according to the above embodiments may be implemented by a program instructing related hardware to complete, where the program is stored in a memory and includes several instructions to enable a control device (such as a processor) or a single chip (such as a single chip, a chip, etc.) to execute all or part of the steps in the method according to the embodiments of the present application. And the aforementioned memory comprises: a U-disk, a removable hard disk, a Read-only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims (10)

1. A method for detecting ammonia slip in an aftertreatment system, the method comprising the steps of:
controlling the SCR of the aftertreatment system to spray urea or reducing agent ammonia to the tail gas of the vehicle when the working condition is detected;
controlling the ammonia nitrogen ratio of the urea or the reducing agent ammonia to the tail gas to be less than 1, and calculating the first conversion efficiency of the SCR;
controlling the ammonia nitrogen ratio to be more than or equal to 1 according to the condition that the first conversion efficiency is within a first conversion efficiency threshold value, and calculating a second conversion efficiency of the SCR;
and judging that the ammonia leakage of the aftertreatment system occurs according to the fact that the second conversion efficiency is smaller than a second conversion efficiency threshold value.
2. The method for detecting ammonia slip in an aftertreatment system of claim 1, wherein the detected operating condition comprises a common operating condition of the vehicle, and the common operating condition specifically comprises:
the engine of the vehicle outputs a rotational speed corresponding to a maximum torque, and an upstream temperature interval of the SCR is 300-400 ℃.
3. The method of claim 1, wherein the controlling the ammonia-nitrogen ratio of the urea or the reducing agent ammonia to the exhaust gas to be less than 1, and the calculating the first conversion efficiency of the SCR comprises:
and controlling the ammonia-nitrogen ratio to be 0.7, and calculating the first conversion efficiency of the SCR according to nitrogen oxides detected by nitrogen-oxygen sensors at the upstream and downstream of the SCR.
4. The method of claim 1, wherein the controlling the ammonia nitrogen ratio to be greater than or equal to 1 and the calculating the second conversion efficiency of the SCR comprises:
and controlling the ammonia-nitrogen ratio to be 1, and calculating the second conversion efficiency of the SCR according to nitrogen oxides detected by an upstream and downstream nitrogen-oxygen sensor of the SCR.
5. The method of claim 1, wherein the first conversion efficiency threshold specifically comprises:
in the case where the ammonia-nitrogen ratio is less than 1, conversion efficiencies of the SCRs in a fresh state and an aged state are respectively calculated, thereby obtaining upper and lower limit values of the first conversion efficiency threshold.
6. The method of claim 1, wherein the second conversion efficiency threshold specifically comprises:
and under the condition that the ammonia nitrogen ratio is more than or equal to 1, respectively calculating the conversion efficiency of the SCR in a fresh state and an aging state, thereby obtaining an upper limit value and a lower limit value of the second conversion efficiency threshold value.
7. The method for detecting ammonia slip in an aftertreatment system according to claim 1, wherein the controlling the ammonia-nitrogen ratio of the urea or the reducing agent ammonia to the exhaust gas to be less than 1, and calculating the first conversion efficiency of the SCR further comprises:
determining that the SCR has a degradation fault according to the fact that the first conversion efficiency is smaller than the first conversion efficiency threshold;
and determining that the SCR has the fault of excessive injection of urea according to the condition that the first conversion efficiency is greater than the first conversion efficiency threshold value.
8. The method of claim 1, wherein determining that an ammonia slip has occurred in the aftertreatment system based on the second conversion efficiency being less than a second conversion efficiency threshold specifically comprises:
and judging that the leaked ammonia reacts with a downstream nitrogen-oxygen sensor of the SCR to generate nitrogen-oxygen compounds according to the fact that the second conversion efficiency is smaller than the second conversion efficiency threshold value.
9. The method of claim 1, wherein determining that an ammonia slip has occurred in the aftertreatment system based on the second conversion efficiency being less than a second conversion efficiency threshold further comprises:
and judging that the aftertreatment system has a serious ammonia leakage phenomenon and triggering an ammonia leakage alarm according to the fact that the difference value between the second conversion efficiency threshold value and the second conversion efficiency is larger than a preset difference value.
10. A controller of an aftertreatment system, wherein the controller comprises a device for detecting ammonia leakage of the aftertreatment system and a computer-readable storage medium, the computer-readable storage medium has control instructions stored therein, and the detecting device implements the method for detecting ammonia leakage of the aftertreatment system according to claim 1 by executing the control instructions, and the detecting device comprises:
the control module is used for controlling the SCR of the aftertreatment system to spray urea or reducing agent ammonia to tail gas of the vehicle when the working condition is detected;
the control module is further used for controlling the ammonia nitrogen ratio of the urea or the reducing agent ammonia to the tail gas to be smaller than 1, and the detection device further comprises a calculation module used for calculating the first conversion efficiency of the SCR;
the control module is further used for controlling the ammonia nitrogen ratio to be greater than or equal to 1 according to the fact that the first conversion efficiency is within a first conversion efficiency threshold value, and the calculation module is further used for calculating a second conversion efficiency of the SCR;
and the judging module is used for judging that the ammonia leakage occurs in the aftertreatment system according to the condition that the second conversion efficiency is smaller than a second conversion efficiency threshold value.
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