Research On Fault Diagnosis Strategy Of SCR System Based On National V Diesel Engine

Based on environmental and energy pressures,the GB18352.5-2013"Light Vehicle Pollutant Emission Limits and Measurement Methods"(Fifth Phase)was issued in 2013.From January 2017,the fifth phase emission regulations were implemented throughout the country.The GB18352.6—2016"Light Vehicle Pollutant Emission Limits and Measurement Methods"(Sixth Phase)was issued was issued in2016.From July 2020,the sixth phase emission regulations were implemented throughout the country,and regulations stipulated the PM emission limit is 3.0mg/km,the NO_X emission limit is 45mg/km,and the passenger car fuel consumption limit is5L/100km,which indicates that China is determined to promote air pollution and corporate technology upgrade.In order to meet the national V,national VI and higher emission regulations,SCR technology is imperative for diesel engines.By July 2020,the implementation of national VI regulations,the"EGR+DOC+DPF+SCR"technology will be adopted by many companies.Therefore,the development of the SCR control system has become a key point.At the same time,the development of fault diagnosis(OBD)technology to ensure the normal operation of the SCR system is also very important.The SCR system that develops and studies the independent property rights and the OBD technology that meets the national emission regulations are also technical problems that many companies have to overcome.According to"Car Compression Ignition,Gas Fuel Ignition Engine and Automotive OBD Technical Requirements",the paper has designed the SCR fault diagnosis system(OBD)function.Mainly for the basic function of the SCR system fault diagnosis made a corresponding study,Such as the sensor's limit value diagnosis,urea tank level sensor fault diagnosis,urea consumption diagnosis,NO_X sensor fault diagnosis.Based on the SCR system of the National V diesel engine,the aim is to design a fault diagnosis and control strategy for parts of diesel engine SCR system by studying the basic functions of the SCR system.According to the modular design,many model of fault diagnosis was built on the MATLAB/Simulink software platform,and the main control module was elaborated.For example,sensor overrun diagnostic model(with urea tank temperature sensor as an example),urea tank level sensor rationality detection model,urea consumption fault diagnosis model,downstream NO_X sensor rationality detection model.By the main application parameters was calibrated,and the model fault diagnosis was simulated respectively,including sensor over-limit fault diagnosis,liquid level sensor fault diagnosis,urea consumption fault diagnosis,and NO_X sensor fault diagnosis.The simulation results verified the correctness of the fault diagnosis strategy and the feasibility of the module function,which satisfied that the requirements of the SCR system fault diagnosis(OBD)control strategy design.Take a urea tank temperature sensor as an example,the HIL verified the correctness of the over-limit fault of the sensor.The verification result proves the functional feasibility of fault diagnosis strategy of urea tank temperature sensor?...