Research On Simulation Technology Of Acoustic Radiation Of Internal-combustion Engine Structure

Structural acoustic radiation noise has become an important factor which restricts the development of I.C.E(Internal-combustion Engine) technology. If the radiation level of the I.C.E can be predicted at the development stage, and through the acoustic optimization, it will be conducive to improving the market competitiveness of the products.In the use of finite element and boundary element coupling analysis theory to analyze the vibration characteristics of I.C.E structure, there is not a consistent one-to-one match between finite element mesh and acoustic boundary element mesh, the finite element mesh surface vibration data can not be assigned directly to the acoustic boundary element model mesh as the acoustic boundary condition, it need to define the equivalent mapping relationship between the two grids, realization of the structural finite element analysis data equivalent mapping transfer to the acoustic grid up, then solving the acoustic radiation characteristics. Therefore, it is very important to study the interpolation of FEM/BEM equivalent mapping in acoustic radiation prediction of I.C.E structure..In this paper, taking into account the complexity of the I.C.E structure, we will use hierarchical analysis hierarchy process. Firstly, from the common plate structure on the surface of I.C.E, research on FEM/BEM equivalent mapping interpolation law for the prediction of sound radiation of plate structure and then the relevant research results are applied to the structure of I.C.E. Mainly completed the following research work:⑴ Taking plate structure as an example, finite element mesh model is established in Abaqus, and the modal analysis is carried out; by applying the harmonic excitation, analysis of structural dynamic response based on modal superposition method, get the structural surface vibration response data and modal participation factors.⑵ By using the direct extraction of the structural finite element surface mesh as the acoustic boundary element mesh in LMS.Virtual Lab-Acoustic, and import surface dynamic response of plate structure, the main acoustic results of radiated are calculated, such as sound power level and sound pressure level. And as a standard, to provide reference for the post text that there is an equivalent mapping data transfer.⑶ The acoustic boundary element mesh is obtained by the "coarsening" process; an equivalent mapping algorithm model of FEM/BEM is established, based on the principle of inverse distance weighted average method, analysis the influence law of the number of neighboring nodes and the maximum distance of the search structure nodes on the acoustic prediction accuracy, to ensure that the accuracy of acoustic analysis can be satisfied.⑷ According to the characteristics of complex structure, wide working speed range and changeable working condition in I.C.E structure, using FEM/BEM coupled solution method and use ATV technology, based on the FEM/BEM equivalent mapping interpolation law of plate structure, it has completed the fast solving structural acoustic radiation problem, and gotted the acoustic physics of I.C.E under certain conditions.