Study On Impact Of The Exhaust Purification Device On Engine Performance And Exhaust Noise

Exhaust purification technology was developed to reduce the harmful ingredients of thediesel exhaust by chemical reactions, physical absorption before the exhaust is discharged intothe atmosphere. It not only can reduce the hazards of the natural environment and humanhealth，but also can achieve the purpose of controlling exhaust noise. But the addition of theexhaust purification device is bound to have an impact on engine performance and exhaustnoise. To achieve the best state for the coupling of exhaust system and engine, it is necessaryto study on the impact of the exhaust purification device on engine performance and exhaustnoise.The GT-power software is used to simulate the working process of engine. It is based onthe theory of one-dimensional fluid dynamics and using the finite volume method to achievedecomposition of model calculation. So when the three-dimensional flow and thethree-dimensional sound exist in exhaust system, there are some differences between actualsituations and the results computed by using GT-power software. To solve this problem, thispaper uses the GT-power software and the software of three-dimensional fluid dynamics(CFD) method Fluent to compute the engine performance. When calculating the soundpropagation, we use the transfer matrix method to calculate the insertion loss of exhaust gaspurification device and tail pipe noise of diesel engine.Use the GT-power software to build the coupling model of the engine and exhaustsystem. Build the three-dimensional model of the exhaust system with the GAMBIT software.In order to simulate the flow field of the exhaust system, the calculated results of theGT-power software was used to set the boundary in Fluent, after that, we use the results as areference in the correction of coupled model parameters to make the two results match. Thenwe make an analysis of the effect that the exhaust purification device had on engineperformance. Based on it, we calculate the impact of purification device on diesel engineperformance and make an analysis of it. With this method, we calculate the pressure loss ofexhaust system which contain muffler、dissipative muffler、through-flow vector、wall flowvector structure respectively and make an analysis of engine performance before and after the correction of diesel engine model.In order to predict the acoustics source impedance accurately and conveniently, theGT-POWER software is used in this thesis to simulate the working process of internalcombustion engine, and the maximum radiated power method is employed to determine theacoustics source impedance. The exhaust acoustic source impedance of4102BG diesel enginewitch is predicted by the maximum radiated power method is compared with the valuecalculated by GT-POWER software. With the maximum radiated power method, we make ananalysis of the impact of speed and load on the acoustics sound sourceIn this paper, we use the acoustics source impedance which calculated by maximumradiated power method and the pipe termination impedance as the boundary conditions at theinlet and outlet of purification device, then, with the four-pole parameters witch is calculatedby three-dimension finite element method, we calculate the insertion loss of purificationdevice by the transfer matrix method. With this method, we calculate the insertion loss ofexhaust system which contain muffler、dissipative muffler、through-flow vector、wall flowvector structure and the radiated noise of engine respectively. Compared with theone-dimensional method, we can know that it is correct to use the transfer matrix method tocalculate the insertion loss of exhaust gas purification device and tail pipe noise of engine.In this paper, we design a set of purification device, then, we calculate and make ananalysis of the impact of purification device on diesel engine performance and exhaust noise.Based on it, I make an optimization design of the device and an analysis of the diesel engineperformance and the exhaust noise before and after optimization.