Study On The WHTC Test Of SCR System For Heavy Duty Diesel Engine

Because of its high thermal efficiency, good adaptability, wide power range and long service life in the field, diesel engine is broadly used in road transportation, engineering machinery, agricultural machinery, locomotive, marine and so on. It is a major power source deployed by truck and coach. In passenger car area, diesel engine has become a trend in Europe.As environmental pollution increasing, people pay more attention to environment protection than before. China’s emissions regulations become more and more in line with the world’s latest ones. The implementation of these regulations puts forward higher requirements on diesel engine technology. Currently, advanced high-pressure common-rail technology, advanced turbocharger technology, diesel exhaust after treatment technology, and in-cylinder combustion optimization technology are occupied by foreign companies. Domestic diesel engine manufactures are still in the initial stage of applying these new technologies, and their product developments heavily rely on the support from international automotive components enterprises. Meanwhile, domestic components enterprises are still in research stage of these new technologies.This paper focuses on the research of V-SCR catalyst characteristics, SCR urban buses road applications, and SCR system applications for WHTC test cycle.Firstly, engine bench is utilized to study the conversion of V-SCR catalysts. The effects of different space velocities on the conversion of SCR, SCR conversion curves under varied temperatures, and NH3leakage during ESC calibration have been investigated. Further, during the test, the measurement accuracy of Continental sensors and the NH3influence on NOx sensor accuracy have also been studied.Then SCR system in actual city buses duty cycles has been studied. In-field data are collected. The SCR system requirements fitting for urban traffic conditions are analyzed. The verification process of the reliability of SCR system under low temperature crystallization test is proposed.Finally, SCR system work conditions under WHTC test cycle are investigated. Engine can meet Beijing IV stage WHTC emission standards by engine emissions calibration and SCR system calibration.