Structural Optimization Of SCR Catalytic Converter For Light-duty Diesel Engine

Our nation pays more and more attention to environmental protection these days.In order to control the pollution of vehicles strictly,our nation decided to launch the National-?emission standards for light-duty diesel vehicles from the New Year's day of 2018.The research is aimed at a light-duty diesel engine called SOFIM8140.43S4 and it has already adopted SCR(selective catalytic reduction technology)as a post-processing plan.By optimizing the structure of the SCR catalytic converter of the light-duty diesel engine,it can meet the requirements of the National-?emission.The main contents and innovations of the research are as follows:1.The principle analysis of the diesel engine post-processing SCR catalytic converter is carried out and the light diesel engine called SOFIM8140.43S4 is used as the object.The overall design of the SCR catalytic converter and the selection of the related components are also carried out in the paper.2.The two-dimensional model of SCR catalytic converter was established by Gambit software and the two-dimensional steady flow field of SCR catalytic converter was simulated by Fluent software.In addition,the internal flow characteristics of the typical SCR catalytic converter are analyzed by simulation.3.Different calculation models,such as inlet expansion pipe angle,outlet contraction pipe angle,carrier length and carrier clearance,are established respectively.The internal flow law of the SCR catalytic converter under different structural parameters is studied by Fluent numerical simulation.The results show that the three parameters including the inlet expansion pipe angle,the length of the carrier and the clearance between the carriers can provide the basis and guidance for the structural optimization of the SCR catalytic converter and the outlet contraction pipe angle can not be used as an optimization parameter.4.Based on the Nelder-Mead algorithm,the goal of structural optimization of the SCR catalytic converter is to optimize the gas flow velocity uniformity at the rear of the carrier as far as possible.The flow field of the optimized SCR catalytic converter is also analyzed.The results show that under the condition of A25 and B50,the gas flow uniformity index in the rear point of the optimized SCR catalytic converter reaches above 0.872.By optimizing,the velocity uniformity of the SCR catalytic converter is improved obviously.5.The optimized SCR catalytic converter is used to match with SOFIM8140.43S4.The results show that the optimized SCR catalyst converter works normally,and the NO_X emission ratio is 1.824g/(kW·h)under the ESC cycle,which reaches the National-?emission standards.