Noise reduction of the radial dissipative silencer in the intake system of the medium-duty diesel engine

摘要

To reduce the characteristic high frequency tonal noise due to the high speed vanes in the turbocharger, the intake system of the medium-duty diesel engine, which is of concern in this study, employs a radial fan-shaped dissipative silencer in the inlet. An acoustic model of such a silencer was studied to predict the acoustic performance. The passage between the lined static flow guides, which are primary acoustic elements of this silencer, was considered as the three-dimensional lined duct of varying cross section. This lined duct was modeled by adopting the segmental approach, which incorporated many lined, stepped straight ducts. First, based on the conservation of mass, momentum to all segments, a steady flow solution was sought for to determine the fluid properties in the axial-direction. Next, in the acoustic analysis, the liner was modeled as a bulk-reacting type, which enabled a two-dimensional analysis using the results of the steady flow analysis. For each segment, eigen-functions were derived and the propagation constants of the cross modes were obtained. The amplitude ratio of incident and transmitted wave in each segment was calculated by the mode-matching technique. Then, calculated transmitted pressure for each mode were summed from lowest modes, and convergence check was done as increasing the number of modes. Finally the transmission loss of lined flow guides was calculated and compared with the measured result.