发动机油底壳的辐射噪声分析及结构优化

油底壳表面辐射噪声占发动机总辐射噪声的24 %左右，已成为降低发动机噪声的重要制约因素。为了降低某油底壳的辐射噪声，通过有限元模型，计算其约束模态，找出油底壳的薄弱位置；进而施加由试验测得的激励，计算油底壳的表面振动加速度。在此基础上，采用边界元法对其进行辐射噪声总声功率级的计算；根据计算结果，对该油底壳进行结构优化，并预测结构优化后的辐射噪声水平。通过优化前后的对比表明：结构优化后约束模态频率有很大的提高，振型也有明显变化，总声功率级降低了1.83 dB (A)。

Radiation Noise Analysis and Structure Optimization for an Engine Oil Pan

The radiated noise from oil pan surface was accounted for about 24 % in the total engine, has become animportant restrictive factor to reduce engine noise. In order to reduce radiated noise of the oil pan, the finite element modelwas established, the constraint mode was calculated, and unsubstantial place of oil pan was found; and then, the surfacevibratory acceleration of oil pan was obtained by the excitation load from test, and on that basis, the total sound power levelwas calculated using the BEM method. According to the results, the structural optimization was done, and the levels ofstructure radiated noise of the oil pan were predicted. The results were compared with those of the original pan. It is foundthat after the improvement, the frequency of constraint mode was greatly increased, the modal shape also changes obviously,and the total sound power level was reduced by 1.83 dB （A）.