Study On The Overall Performance Of Exhaust Catalytic Silencers

It is important research project to reduce the diesel engine exhaust emission and noise in the today's world. The exhaust catalytic silencers have wide potential applications in view of their dual functions of exhaust emission reduction and noise control, and may save the space as a single device in the exhaust system. This paper studies the acoustic attenuation performance, flow distribution, flow resistance loss and purification characteristics of the exhaust catalytic silencers.Based on the sound propagation theory in the viscous flow, the transfer matrices of the capillary tube and catalytic monolith are built and then may be used to calculate the acoustic attenuation performance of catalytic monolith. According to the structure of the catalytic converter, it is divided into two parts: the monolith and the connected cavities. The acoustic calculation models of the two parts are built up by using the transfer matrix method and the finite element method respectively, and then they are coupled to calculate the transmission loss of the catalytic converter. Theoretical prediction is then compared with the experimental result of a catalytic monolith to validate the theory of this paper.A model of the flow field in the catalytic converter is established by treating the monolith as porous media. The flow field and pressure loss is simulated with the computational fluid dynamics (CFD) software. The effects of monolith parameters, gas velocity and inlet conical angle on the flow field are analyzed and discussed, which may be used to guide the optimum design of catalytic converters.The mathematical model is established by combining different chemical reaction mechanisms with the governing equations. The mathematical models of a single channel and the whole monolith of the OCC are built up respectively. In this paper, the analysis is conducted from the point of view of chemical kinetics by using CFD software. The rule of conversion with the change of temperature for harmful components and the mass distribution of harmful components in the channel are obtained, which could provide a guide for the coating of the catalyst.An exhaust catalytic silencer of diesel engine is designed. The acoustic attenuation performance, flow resistance loss and emission reduction efficiency are predicted and analyzed. The effects of inlet orientation, internal connecting tubes and the flow guiding annuluses on the overall performance parameters of the exhaust catalytic silencer are investigated.