CN114323692A - SCR (selective catalytic reduction) low-efficiency fault diagnosis method - Google Patents
SCR (selective catalytic reduction) low-efficiency fault diagnosis method Download PDFInfo
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- CN114323692A CN114323692A CN202111637057.9A CN202111637057A CN114323692A CN 114323692 A CN114323692 A CN 114323692A CN 202111637057 A CN202111637057 A CN 202111637057A CN 114323692 A CN114323692 A CN 114323692A
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- 238000003745 diagnosis Methods 0.000 title claims abstract description 20
- 238000000034 method Methods 0.000 title claims abstract description 13
- 238000010531 catalytic reduction reaction Methods 0.000 title description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 170
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 85
- 238000012544 monitoring process Methods 0.000 claims abstract description 19
- 238000009825 accumulation Methods 0.000 claims abstract description 7
- 229910000069 nitrogen hydride Inorganic materials 0.000 claims abstract description 6
- 238000011144 upstream manufacturing Methods 0.000 claims description 7
- 239000000446 fuel Substances 0.000 claims description 6
- 238000002347 injection Methods 0.000 claims description 6
- 239000007924 injection Substances 0.000 claims description 6
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 4
- 239000004202 carbamide Substances 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 claims description 4
- 238000000197 pyrolysis Methods 0.000 claims description 4
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 claims description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 abstract description 4
- 229910052717 sulfur Inorganic materials 0.000 abstract description 4
- 239000011593 sulfur Substances 0.000 abstract description 4
- 230000000694 effects Effects 0.000 abstract description 3
- 231100000572 poisoning Toxicity 0.000 abstract description 3
- 230000000607 poisoning effect Effects 0.000 abstract description 3
- 239000003054 catalyst Substances 0.000 description 2
- 238000001514 detection method Methods 0.000 description 1
- 239000002283 diesel fuel Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
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Abstract
The invention discloses a fault diagnosis method for low SCR efficiency, which comprises the following steps: s1, judging a general release condition; s2, calculating the actual ammonia storage amount; s3, NH3Monitoring the storage capacity; s4, time accumulation counting; s5, calculating the ammonia leakage ratio based on time; and S6, judging error. The invention has the advantages that: by NH3The monitoring of the storage capacity avoids the phenomenon of false alarm caused by working conditions or SCR sulfur poisoning, and has high diagnosis accuracy and better use effect.
Description
Technical Field
The invention relates to the field of ammonia leakage detection, in particular to a fault diagnosis method for low SCR efficiency.
Background
The automobile emission regulation stipulates that the automobile OBD system must be provided with the SCR catalyst for converting NOXEfficiency diagnostic capability, prior art solutions by SCR catalyst upstream NOx mass flow and downstream NOXThe actual average efficiency is calculated by mass flow to judge, when SCR is influenced by working conditions or poor diesel oil is added, reversible SCR sulfur poisoning easily occurs in short time, SCR efficiency is obviously reduced, error report is caused, and NH at the moment3The storage capacity can not be obviously reduced, and the situation of false alarm is easy to occur.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for passing NH3Monitoring of storage capacity to avoid production due to operating conditions or SCR sulfur poisoningThe SCR low-efficiency fault diagnosis method has the advantages of false alarm, high diagnosis accuracy and better use effect.
In order to solve the technical problems, the technical scheme provided by the invention is as follows: an SCR inefficiency fault diagnosis method includes the following steps:
s1, judging a general release condition;
s2, calculating actual ammonia storage amount according to NOXThe corresponding relation of the reaction with ammonia is calculated according to the ammonia nitrogen ratio to obtain NOXMass of ammonia reacted, total mass of ammonia produced by pyrolysis of urea with NOXThe quality of the reacted ammonia and the quality of the leaked ammonia are subjected to difference calculation to obtain the actual ammonia storage amount;
S3、NH3monitoring the storage capacity, comparing the calculated actual ammonia storage with the target ammonia storage, wherein ammonia leakage does not occur when the actual ammonia storage is smaller than the target ammonia storage, and if the ammonia sensor detects ammonia leakage at the moment, determining that the ammonia storage capacity of the SCR is reduced;
s4, time accumulation counting, monitoring release conditions are met, a condition counter starts timing, ammonia is detected through an ammonia sensor, ammonia leakage is identified, and ammonia leakage time accumulation is carried out when the monitoring release conditions are met;
s5, calculating the ammonia leakage ratio based on time, and calculating the ratio of the ammonia leakage accumulated time to the accumulated time of the condition counter in real time;
and S6, judging error, releasing the monitoring condition, judging that the SCR efficiency is normal if the deviation percentage of the time ratio is lower than a set limit value, and reporting error if the deviation exceeds the set limit value.
Further, the general release condition determination in S1 includes (1) performing an ammonia sensor signal reliability diagnosis based on the received ammonia sensor signal, and if the ammonia sensor signal is normal as a result of the diagnosis, executing the next step; (2) judging the condition of the fuel injection quantity, and executing the next step if the fuel injection quantity is greater than a set value; (3) judging the rotating speed condition of the engine, and executing the next step when the rotating speed is in a set range; (4) judging the condition of the engine running mode, and if the engine running mode is in the set mode range, executing the next step; (5) judging the atmospheric pressure condition, and executing the next step if the atmospheric pressure is in a set range; (6) judging the environment temperature condition, and executing the next step if the environment temperature is within a set range; (7) judging the condition of SCR upstream temperature, and executing the next step if the SCR upstream temperature is in a set range; (8) judging the SCR exhaust flow rate condition, and executing the next step if the SCR exhaust flow rate is in a set range; (9) and if the conditions are met, judging that the monitoring conditions are released.
Further, in S4, the condition counter time is reset when reaching the set value.
Compared with the prior art, the invention has the advantages that: according to the SCR low-efficiency fault diagnosis method, an ammonia sensor is additionally arranged after SCR is processed at the exhaust end of an engine, and ammonia and NO generated by urea pyrolysis reaction are mixed withXIntegrating the difference of the reacted ammonia, comparing the integrated difference with an ammonia storage model, detecting ammonia leakage by an ammonia sensor if the actual ammonia storage does not reach the target ammonia storage, and considering that the ammonia storage capacity of the SCR is reduced when the ammonia leakage exceeds a certain limit value, namely the SCR efficiency is low; by NH, in contrast to the prior art3The monitoring of the storage capacity can effectively avoid the phenomenon of false alarm caused by working conditions or SCR sulfur poisoning, thereby effectively improving the accuracy of diagnosis and ensuring better use effect.
Drawings
Fig. 1 is a flow chart of a method for diagnosing SCR inefficiency according to the present invention.
Detailed Description
Examples
An SCR inefficiency fault diagnosis method, comprising the steps of:
s1, general release condition judgment:
(1) performing credibility diagnosis on the ammonia sensor signal according to the received ammonia sensor signal, and executing the next step if the diagnosis result is that the ammonia sensor signal is normal;
(2) judging the condition of the fuel injection quantity, and executing the next step if the fuel injection quantity is greater than a set value;
(3) judging the rotating speed condition of the engine, and executing the next step when the rotating speed is in a set range;
(4) judging the condition of the engine running mode, and if the engine running mode is in the set mode range, executing the next step;
(5) judging the atmospheric pressure condition, and executing the next step if the atmospheric pressure is in a set range;
(6) judging the environment temperature condition, and executing the next step if the environment temperature is within a set range;
(7) judging the condition of SCR upstream temperature, and executing the next step if the SCR upstream temperature is in a set range;
(8) judging the SCR exhaust flow rate condition, and executing the next step if the SCR exhaust flow rate is in a set range;
(9) if the conditions are met, the monitoring condition is judged to be released;
s2, calculating actual ammonia storage amount according to NOXThe corresponding relation of the reaction with ammonia is calculated according to the ammonia nitrogen ratio to obtain NOXMass of ammonia reacted, total mass of ammonia produced by pyrolysis of urea with NOXThe quality of the reacted ammonia and the quality of the leaked ammonia are subjected to difference calculation to obtain the actual ammonia storage amount;
S3、NH3monitoring the storage capacity, comparing the calculated actual ammonia storage with the target ammonia storage, wherein ammonia leakage does not occur when the actual ammonia storage is smaller than the target ammonia storage, and if the ammonia sensor detects ammonia leakage at the moment, determining that the ammonia storage capacity of the SCR is reduced;
s4, time accumulation counting, monitoring release conditions are met, a condition counter starts timing, ammonia is detected through an ammonia sensor, ammonia leakage is identified, ammonia leakage time accumulation is carried out when the monitoring release conditions are met, and the condition counter is reset when the time reaches a set value;
s5, calculating the ammonia leakage ratio based on time, and calculating the ratio of the ammonia leakage accumulated time to the accumulated time of the condition counter in real time;
and S6, judging error, releasing the monitoring condition, judging that the SCR efficiency is normal if the deviation percentage of the time ratio is lower than a set limit value, and reporting error if the deviation exceeds the set limit value.
Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that: modifications and equivalents may be made thereto without departing from the spirit and scope of the invention and it is intended to cover in the claims the invention as defined in the appended claims.
Claims (3)
1. An SCR inefficiency fault diagnosis method, comprising the steps of:
s1, judging a general release condition;
s2, calculating actual ammonia storage amount according to NOXThe corresponding relation of the reaction with ammonia is calculated according to the ammonia nitrogen ratio to obtain NOXMass of ammonia reacted, total mass of ammonia produced by pyrolysis of urea with NOXThe quality of the reacted ammonia and the quality of the leaked ammonia are subjected to difference calculation to obtain the actual ammonia storage amount;
S3、NH3monitoring the storage capacity, comparing the calculated actual ammonia storage with the target ammonia storage, wherein ammonia leakage does not occur when the actual ammonia storage is smaller than the target ammonia storage, and if the ammonia sensor detects ammonia leakage at the moment, determining that the ammonia storage capacity of the SCR is reduced;
s4, time accumulation counting, monitoring release conditions are met, a condition counter starts timing, ammonia is detected through an ammonia sensor, ammonia leakage is identified, and ammonia leakage time accumulation is carried out when the monitoring release conditions are met;
s5, calculating the ammonia leakage ratio based on time, and calculating the ratio of the ammonia leakage accumulated time to the accumulated time of the condition counter in real time;
and S6, judging error, releasing the monitoring condition, judging that the SCR efficiency is normal if the deviation percentage of the time ratio is lower than a set limit value, and reporting error if the deviation exceeds the set limit value.
2. The SCR inefficiency fault diagnosis method of claim 1, wherein: the general release condition determination in S1 includes (1) performing an ammonia sensor signal plausibility diagnosis based on the received ammonia sensor signal, and if the ammonia sensor signal is normal as a result of the diagnosis, executing the next step; (2) judging the condition of the fuel injection quantity, and executing the next step if the fuel injection quantity is greater than a set value; (3) judging the rotating speed condition of the engine, and executing the next step when the rotating speed is in a set range; (4) judging the condition of the engine running mode, and if the engine running mode is in the set mode range, executing the next step; (5) judging the atmospheric pressure condition, and executing the next step if the atmospheric pressure is in a set range; (6) judging the environment temperature condition, and executing the next step if the environment temperature is within a set range; (7) judging the condition of SCR upstream temperature, and executing the next step if the SCR upstream temperature is in a set range; (8) judging the SCR exhaust flow rate condition, and executing the next step if the SCR exhaust flow rate is in a set range; (9) and if the conditions are met, judging that the monitoring conditions are released.
3. The SCR inefficiency fault diagnosis method of claim 1, wherein: in S4, the condition counter time is reset when it reaches the set value.
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Cited By (1)
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| CN114961956A (en) * | 2022-07-06 | 2022-08-30 | 潍柴动力股份有限公司 | Method and device for diagnosing conversion efficiency of selective catalytic reduction |
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