A coupled heat transfer model was constructed for silencer and external atmosphere environment, and the Fluent code was used to calculate the temperature field of a simple expansion chamber silencer. The reasons for internal and external temperature distribution of the silencer and the effect of internal flow on the temperature field were analyzed. Based on the above study, the temperature field of dual-inlet silencer was calculated under a given work condition.

The software Pro/E was employed to build the 3-D model of a diesel engine’s exhaust system. The software HyperMesh was used to create the FEM mesh, and then the FEM mesh data was input into the finite element software ANSYS for simulation to obtain the modal characteristics of the exhaust system. On this basis, the harmonic response analysis was performed for analyzing the diesel engine’s excitation force and the vibration of the exhaust system. Finally, the vibration isolation effect of metal bellows on the exhaust system was evaluated.

( College of Power and Energy Engineering, Harbin Engineering University, Harbin 150001, China )
Abstract : The finite element method is used to calculate the internal sound field of a silencer, the mode waves are decomposed based on the acoustic mode theory, and then the transmission loss is determined. Based on the same theory, the transmission loss is measured through wave decomposition method with multi-sensors. It is found that results of the experimental measurement agree well with those of the numerical predictions. The effective frequency range for prediction and measurement of transmission loss are both extended beyond the cut-off frequency.

The time-domain method based on the large eddy simulation is applied to predict the flow noise in variable cross-sectional area pipes. For the pipes with sudden area contraction and expansion, the numerical predictions and measured results agree reasonable well. Then the effects of connected structures of pipes on the flow noise is investigated numerically, and the variable cross-sectional area pipes with low flow-generated noise are explored.

The compact SCR purified noise reduction device may achieve the dual functions of engine exhaust purification and exhaust noise control. The DPM model of Fluent software is used to simulate the gas flow and aqueous spray atomization process within SCR purified noise reduction device. The acoustic finite element method of Sysnoise software is used to analyze the acoustic attenuation performance of SCR purified noise reduction device. The effects of different inlet orientation and perforated tubes on resistance loss and transmission loss are investigated.

The finite element method (FEM) is applied to predict acoustic attenuation characteristics of straightthrough perforated tube silencer with steady air flow. The finite element formulation is carried out, and the numerical method and procedure for predicting the acoustic attenuation characteristics are introduced. Since the convective effect is taken into consideration, the present method is suitable for the case with steady air flow. Transmission loss of straightthrough perforated tube silencer is then predicted using threedimensional finite element method. The numerical results show that the acoustic attenuation effect is raised in the medium and higher frequency range as the Mach number of the flow is increased. It is suggested that in order to predict the acoustic attenuation characteristics of straightthrough perforated tube silencer accurately, the influence of steady flow on the sound propagation in the silencer should be considered.

Influence of air flow on sound elimination effect of silencers with double expansion chamber is analyzed by means of the dual reciprocity boundary element method (DRBEM). The results show that the influence of higher Mach number subsonic flow on the sound elimination of complex silencers can not be ignored. Affects of the number of interconnecting tubes, inlet positions and the structural type of diversion annuluses on acoustic transmission loss of the silencers are summarized. Such conclusions are of some practical value for engineering application.