Evaluation on the structural-acoustic modification of internal combustion engines

To improve the accuracy of prediction in the simulation of the dynamic and acoustic behavior of engines, and offer selective projects, an approach based on the coupled FEM/BEM method is proposed. Prediction models of a certain 4 cylinder diesel engine were established. Results of prediction including vibration modes, surface vibration velocity, radiation power, radiation ratio and field pressure were obtained. Based on these results, four projects were investigated and the effect of modified engine structures was analyzed. Comparison between the original model and several modified models showed that the wavy-ribs in the oil sump, the main bearing cap connected by transverse bolts, and the bracket of balance structure proved to be excellent in reducing the engine's structural noise.