Research On Numerical Simulation Of Diesel Engine’ Emission Performance To Meet The Sixth Phase Of Emission Standards

With the improvement of people’s awareness of environmental protection,the emission limits of cars are increasingly strict,and the sixth phase of emission standards will be implemented in next few years.At present,the application development of the sixth phase of emission standards’ s diesel engine is not mature enough.Under this trend,this paper has carried out a comprehensive study on the measures to reduce diesel engine emissions.At the same time,a one-dimensional numerical simulation model of the engine and integrated aftertreatment system and exhaust gas recirculation(EGR)system was established based on the data of the bench test of a turbocharged diesel engine that meets the fifth phase of emission standards.Also,a three-dimensional CFD model for studying the uniformity of EGR intake was established,and deeply studied the impact of different EGR schemes on diesel engine performance and emissions.The main research contents and results of this paper are:(1)The one-dimensional simulation models of high-pressure circulating EGR(HP_EGR)and low-pressure circulating EGR(LP_EGR)of the turbocharged diesel engines were established and verified by GT-power software.Based on this model,different throttle valves and back pressure valves were further studied.The results showed that compared with the HP_EGR scheme,the LP_EGR scheme can flexibly adjust EGR through the throttle valve(or back pressure valve),and it has the ability to obtain a larger EGR rate.Therefore,the LP_EGR scheme is applicable to a wider range;(2)Using AVL-Cruise software to establish a vehicle road cycle simulation model,and the typical engine operating conditions were calculated based on the light vehicle test cycle(WLTC).The NOx and Soot emissions of the engine after integrated post-processing and EGR system were obtained,and the results were weighted.The results show that the total emissions can meet the sixth-a phase of emission standards.(3)Based on the combination of one-dimensional and three-dimensional analysis,the uniformity of EGR rate of each cylinder under steady-state and transient conditions were studied based on CFD(AVL-Fire).The calculation results showed that the EGR uniformity of the 3-cylinder’s intake manifold is the best,the fourth cylinder is the second.Which provides a reference for the optimization of the engine’s EGR uniformity which meet the sixth phase of emission standards.This paper focuses on the EGR combined with integrated post-processing system to improve the comprehensive performance of diesel engine,while taking into account the power and economy of the diesel engine,providing theoretical support for the optimization of diesel engines.The work of this paper has great practical value and engineering value.