Structural Noise Analysis Of F168 Gasoline Engine

As a kind of power machinery, the internal-combustion engine is widely applied in the national economy. Noise and vibration is the important parameter for the engine's performance. Along with kinds of rules and standards about noise and vibration, and the practical requirements for the environment protection and good NVH performance, the structural noise prediction has been an important aspect in the field of internal-combustion engine research. Knowing the radiant level of engine noise at the stage of design and doing the optimization of whole engine structural noise control based on simulative model have great significance to insure internal-combustion engine satisfying more and more strict requirement of engine noise and to promote the product competitive capability.Based on the F168 gasoline engine, the study of engine structural noise prediction is done systematically by using Finite Element Method (FEM),Multi-Body Dynamics (MBD) and Boundary Element Method (BEM), and the research on the structural noise prediction of F168 gasoline engine is achieved, which can be as the basis and reference for the afterwards structural modification and optimization. In detail, the main work is as follows:(1) At first, the actuality of the research about engine structural noise prediction is reviewed after referring to some literature and relative theory, and then coming up with the main scheme and technical path of this research. (2) Creating the 3D geometry model and the FEM model, and the modal analysis is done. According to the practical conditions, the compromise between the computation precision and speed should be taken into consideration when creating the FEM model. The natural frequencies and eigenvalues can be computed from modal analysis, which not only can validate the FEM model but also as the basis for the structural modification and optimization.(3) Create the dynamic model in Excite software and run the dynamic response analysis. The free degree number of the FEM model is very large, using the sub-structure method, the free degree number can be deceased from millions to thousands by matrix reduction, which can save the time and computer resources. Combined with the FEM and MBD, the nonlinear factor is taken into consideration and the dynamic response analysis is carried systematically.(4) The boundary element model of F168 gasoline engine is created, and after the import of the results of the dynamic response analysis, the structural noise prediction is carried using the professional vibro-acoustic software Sysnoise. Then we can get the acoustic results such as sound pressure, sound intensity, sound power, radiation efficiency and so on. Combined with the results of dynamic response analysis, the measure of the structural modification and optimization is received.