Research On Fault Diagnosis Of Diesel Vehicle Emissions Exceeding Standards Based On Multi-Source Information

The implementation of Inspection and Maintenance(I/M)systems is the most effective measure for controlling emissions from diesel trucks.Currently,the diagnostic capabilities of the M stations are insufficient,and blind repairs are common.According to the actual needs of the maintenance and diagnosis work of the diesel truck exceeding the standard at station M,this paper employs a comprehensive approach including theoretical analysis,simulation analysis,and survey research,to study the diesel engine exhaust emission fault diagnosis technology based on multi-source information and to develop a diagnostic system.The main research achievements are as follows:(1)Simulation analysis was conducted to investigate the impact of changes in the technical conditions of the target diesel engine model on emissions.Through investigative analysis,the research object was determined to be heavy-duty diesel trucks with emission standards of National IV and National V,and a technical route of high-pressure common rail+selective catalytic reduction(SCR)with in-use diesel engines as the target research model.By establishing an emission simulation model based on a National V diesel engine in GT-Power software,which is founded on the mechanism of pollutant generation of diesel engines and the characteristics of the emission control system of the target engine type,the impact of performance degradation of the most frequent faulty components of diesel engines on emissions exceeding standards is analyzed.These findings provide a mechanistic basis for identifying targets for diagnosing diesel trucks that exceed emission standards and optimizing reasoning analysis.(2)The relationship between symptoms and causes of faults in diesel engines with emissions exceeding standards was analyzed,and fault category identification targets were determined.The periodic emission inspection process,items,and requirements for diesel trucks were analyzed,and the characteristics of diesel engine pollutant emissions exceeding standards were summarized and analyzed.A total of 563 cases of maintenance and management of diesel trucks with emissions exceeding standards were investigated,collected,and verified.Through the analysis of maintenance and management cases,the main fault locations and reasons corresponding to NO_x emissions exceeding standards,PM emissions exceeding standards,and power unqualified for the target model were identified.The characteristics of the involved fault locations and reasons were analyzed,and seven categories of diagnostic system faults were identified,including intake system faults,SCR carrier blockage,and poor fuel spray,etc.(3)A fault diagnosis system for diesel trucks with excessive emissions was designed and developed.Based on the principles of fault classification identification and diagnostic parameter selection,six parameters from three sources,including NO_xemissions,PM emissions,intake air flow,and exhaust back pressure,were selected as diagnostic parameters.These parameters were sourced from the I-station loaded deceleration exhaust pollutant detection report,the vehicle-mounted OBD system,and manual measurements taken at the maintenance station.The system was constructed using fuzzy diagnosis theory and technology,and was based on multi-source information.A fuzzy diagnosis model was designed by combining statistical analysis of maintenance cases and expert experience,and the diagnostic system was developed.A diagnostic system verification test was conducted,and preliminary results showed that the system’s fault diagnosis accuracy rate exceeded 90%,providing useful guidance for the actual maintenance of diesel trucks with excessive emissions at maintenance stations.