Analysis Of The Flow And Acoustic Performance Of Catalytic Muffler And Design Research

The exhaust and noise made by the motor vehicle do great harm to our environment,and impair the physical and psychological health of human beings,in which the pollution of heavy-duty diesel vehicle occupies a big position.Doing some breakthrough in this is positive to our surroundings.This dissertation will do some research in flow field and sound field of the catalytic muffler designed for the diesel engine.,discuss the factors that impact its catalytic efficiency,dynamic performance and acoustical behavior,and find some synthesis design methods.Firstly establish the mathematical models of the inner flow field and the urea injection.Considering the unique structure of the honeycomb carrier,treat it as porous solid,the left flow field deal with turbulence model.Using the DPM simulates the urea injection.Provide the evaluation criterion of the inner flow field,calculate the flow field by CFD software FLUENT,and discuss the influences to velocity field and pressure field bringing by structure changes.Calculate the Transmission loss by the Transfer Matrix Method and Finite Volume Method respectively,compare the results and prove the believability of CAE software GT-power.Finally discuss the influences of carrier structure to the acoustical performance of the system.On the basis of the previous,find two synthesis design methods to do the simulation design of the catalytic muffler.The first one takes advantage of the coupling of GT-power and FLUENT,build the complex box-type catalytic muffler model,the 6-cylinder diesel engine and the Insertion Loss computation module,calculate the IL and discuss the distribution of the pressure field and velocity filed on some different engine operating conditions.Another one is calculating the TL in the FLUENT based on 3D time-domain pulse method.And discuss the acoustical behavior of system on different inlet-velocity of the airflow.