Numerical Simulation Research On The Lean- No_x-Trap Of Physical Factor And Intake Components Of Lean Burn Gasoline Engine

The ICE brings convenience and comfort to people's life,and it also caused a series of energy and environment issues simultaneously,which challengs the engine related researchers and also provides an opportunity to develop advanced technology of in-cylinder and after-treatment system of engines.Most of passenger vehicles operate at medium-low load area where gasoline engines usually have a relative worse BSFC because of its pumping loss.The application of lean-burn technology on gasoline engine could compensate its drawback in fuel economy.But conventional TWC of gasoline engines cannot control NOx emission efficienctly under an ultra lean AFR because of its internal oxygen inhibition phenomenon,which makes NOx control technology in lean-burn gasoline engines become one of the highlights in the current research field.In this paper,a model based on Stuttgart principle was built to accurately simulate the working process of the LNT.The simulation results was achieved from the analysis of NOx adsorption process,and the influence of temperature,space velocity of the inlet boundary,length-diameter ratio and concentration of CO₂ and vapor on the performance of LNT was researched,which will provide theoretical basis for the practical application of LNT.Temperature is an important influencing factor on NOx adsorption.The result show that for low and high temperature,NOx emissions are relatively higher,and most of them are NO.Low leakage of NOx happen between 300?and 350?,which lead to more NO₂ pollution.With the increase of space velocity from entrance boundary,working efficiency of adsorption goes down.The gas space velocity should be taken into consideration to achieve the best NOx control.For length-diameter ratio of the catalyst,when the length of catalyst increase,the LNT catalyst has a lower efficiency on NOx trap.The inhibition of CO₂ and vapor was explored and the results show that CO₂would significantly reduce the LNT adsorption efficiency compared with non-CO₂adsorption efficiency.While the adsorption efficiency nearly constant with the increase of CO₂ concentration.Vapor reduces the efficiency to a certain extent less than CO₂,and the reduction is more obvious with the increase of vapor.When both CO₂ and vapor exists,its adsorption efficiency stands between sole CO₂ and sole vapor.This paper also investigates into LNT desorption and reduction period for three common reduction gas:H₂,CO and C₃H₆.The results show that H₂ has the best reducing ability,followed by CO,and C₃H₆ to be the worst.CO₂ and vapor have little influence on H₂ and C₃H₆,while for CO,NOx leakage and initial burst release increase when CO₂ content grows.On the other side,time needed for rich-burn decrease with the CO₂ content growth.