Performance Analysis And Optimization Of Catalytic Muffler

The catalyst is used to reduce vehicle exhaust emissions,and the muffler reduce exhaust noise,thereby meeting vehicle emission standards and passenger comfort requirements.The catalytic muffler is tightly composed of the catalyst and the muffler,which has the function of reducing emissions and noise,saving the space structure of the exhaust system.The catalytic muffler was developed for emission standard CN6,which composed of DOC,DPF,SCR and muffler.Currently,This study on the performance of this structure is still relatively less in China.In the paper,the flow field characteristics,acoustic performance and structural intensity of the new catalytic muffler are studied,which provides a reference for the further optimization design of catalytic muffler.After meshing the 3D geometric model of the catalytic muffler,a fluid simulation model considering the spraying and chemical reaction of the urea solution was established and calculated.According to the calculation results,the velocity field,temperature field and pressure field of the catalytic muffler fluid are analyzed,and the velocity uniformity coefficient,pressure loss,and mass fraction uniformity coefficient are quantitatively evaluated.These results show that the velocity distribution of the carrier of the catalytic muffler is uniform,the temperature difference is small,and the pressure loss is large.The NH₃ mass fraction uniformity coefficient of the inlet section of the SCR carrier is low,and there is a room for further optimization.Establishing the acoustic finite element model of the catalytic muffler,the acoustic transmission loss is calculated to analyz the muffler performance of the catalytic muffler.At the same time,the effects of parameters such as the number of carriers and flow rate on the muffler performance of the catalytic muffler were studied.Based on the bidirectional fluid-structure coupling method,a fluid-structure coupling calculation model is established.The heat flow and temperature transfer between the fluid domain and the structure domain are used to calculate the thermal stress and thermal deformation of the catalytic muffler shell under thermal load.Finally,yield limit is used to analyze the structural intensity at high temperature.Through the analysis and research of the flow field characteristics,acoustic performance and structural intensity of the catalytic muffler,the catalytic muffler model need be optimizated.The velocity uniformity coefficient of the SCR inlet cross section and the mass fraction of the reactant at the urea nozzle position at three different angles were studied.Through the analysis and comparison of the three schemes,the optimization and improvement of the urea nozzle position rotated 10°clockwise improves the catalytic efficiency of the catalytic muffler SCR carrier more significantly.