| The exhaust of automobile has been one of the social effects of pollution. With the problem solved step by step, the noise of automobiles have been a main problem. It's investigated that 71 percent of the automobile noise is produced by engine.Foreign engineers mainly use advanced testing apparatuses and CAD\CAE measures to study engine noise. The results are relatively accurate, and can be used in practice. Because the measures they use are advanced, the time they need is comparatively short. This meets to the requirements of production and market. As regards domestic corporations, they have less capital to purchase expensive apparatuses. So using software to optimize and design is very important.To reduce the noise of an engine, reducing its radiant noise is one of the effective methods. It has proved that the components of shell type in engine has thin wall and big plane and is the main radiant point of surface noise. Some data indicate the radiant noise of oil pan is an important part of engine radiant noise. In some conditions 15~22 percent of engine noise is come from oil pan. Above all, reducing the radiant noise of oil pan is meaningful to reducing engine noise.In most papers of oil pan radiant noise analysis, only oil pan was considered, oil was just regarded as damp and was not analyzed. For more accurate simulating the oil pan, this paper built a liquid-solid couple model of oil pan and oil, and analyzed them as a whole.FEM has matured in mechanics. But analyzing acoustic radiation need mesh the exterior acoustic field into 3D mesh, which increases the element number and solving workload and even lead the mesh cannot be solved. Therefore,FEM only applied in interior acoustic field or exterior acoustic field of simple and regular structure. Different from FEM, BEM uses boundary integral equation, which decreases the dimension of the problem. Therefore the method can solve the problems of both limitary and limitless field. Combine the two methods will gain a fine effect.This paper combined FEM and BEM, simulated the solid-liquid couple oil pan of CA6110 diesel engine, analyzed its radiant field, and then analyzed some parameters' effect to its radiant field. At present, FEM is the most successful and practical method to solve the system dynamical response. Through dispersing the vibration structure and apply suitable boundary condition, FEM can easily solve all kinds of structure responses.Modal analysis is the basic of dynamics, and as well as the effective method to validate FEM model. This paper tested the experiment mode of the oil pan via the impulse prompting method, and got the oil pan's nature frequency and mode. Then built FEM model of oil pan through Ansys, which is a FEM analysis software, and computed its free mode. Through comparing the two kinds of modal results, it was find that the errs are all not more than 10 percent, so it can be concluded that the model is right and can be used for lasting analysis.After the modal analysis, this paper analyzed the surface displacement response of oil pan. First, tested the prompting that oil pan undertake when the engine in working order, and the surface displacement response spectra on the centers of the five big planes at same time. Then, built liquid-solid couple FEM model, applied accurate boundary condition and prompting which come from the experiment mentioned above. After harmonic solution, the surface displacement spectra of the oil pan were gotten, which can be the velocity boundary condition of BEM analysis. Through observing the surface displacement response spectra of the nodes which in the centers of oil pan's five big planes and comparing them with the trial results, it is find that they are consistent, so the model and method can be considered as right.Just as noted above, BEM is a best method to simulation an acoustic field. This paper simulation the exterior acoustic field of oil pan with direction BEM. First, built a semi-anechoic chamber BEM model of oil pan's acoustic field, |
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