| Numerical simulation of structural acoustics is an important aspect of noise and vibration control domains. The 9-19 No.5A centrifugal fan is studied in this essay. In this study, simulation of the fluid field of the fan was proceeded by employing the finite volume method; and by using FEM analysis, vibrating of the impeller and volute shell of the centrifugal fan was simutlated. With combining FEM and BEM,the study of the sound field of the fan is presented in the essay.The achievements of former researcher in noise and vibration control of centrifugal fan are reviewed firstly, which make the key problems clearer. The finite element method and the boundary element method are introduced as well as the finite element software (FLUENT, ANSYS and Sysnoise)In the project, there are four parts concluded as follows:In the first part, according to the features of the geometry and character of the fluid field, meshing model is built in FLUENT software. The 3D turbulent flow field problem in the impeller of the centrifugal fan is solved by using the standard k-turbulence model and wall function. The influences of the blade profile on speed distribution, press distributions and the flow regulation pattern in the impeller of a centrifugal fan was also studied.In the second part, finite element model of the impeller of the centrifugal fan is built and the mode analysis is carried out. In ANSYS software the impeller model is meshed by element type shell63, and the former 100 step modes are extracted. In the paper, the comparision between free mode and stess mode is completed.In the third part, modeling the shell of fan in finite element method, the mode analysis and harmonic analysis are carried out for two shell different in thickness. After results of the harmonic responsing analysis is loaded on the model of shell as boundary conditions, the Distribution of the vibration on the shell is studied by using indirect boundary element model.In the last part, analysis of the sound field around the shell of the fan is done with combining finite element method and boundary element method by using software ANSYS and SYSNOISE. After the inderect boundary element model is buit and the results of the harmonic responsing analysis of the shell is transferred onto the acoustic mode as boundary conditions, the problems of the sound field around the fan is solved in software SYSNOISE. |
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