某小型发动机辐射噪声预测研究

Research On Radiation Noise Prediction of a Small Engine

为了精确预测某小型发动机辐射噪声,采用仿真与试验相结合的方法对发动机进行振动和噪声数值仿真。通过计算模态与试验模态对标,校验有限元模型精度,模态频率最大相对误差为3.07%;运用发动机多体动力学软件建立配气机构、活塞敲击及曲柄连杆机构多体动力学模型,获取作用在机体上的主要激励力。将仿真分析得到的激励力和试验模态数据导入到LMS Virtual.Lab软件中,运用模态叠加法计算发动机结构振动和辐射噪声。结果表明:仿真与试验结果一致性较好,振动主要阶次对应,振幅相近,辐射噪声最大误差为3.6 dB(A)。分析结果为后续发动机噪声优化提供了依据。

In order to accurately predict the radiated noise of a small engine,simulation and experimentation are combined to simulate the engine vibration and noise.Via comparing the calculated modal with the experimental modal and verifying the accuracy of the finite element model,it's found that the maximum relative error of modal frequency is 3.07%.The multi-body dynamics models of valve mechanism,piston slap and crankshaft connecting rod system were built with engine multi-body dynamics software,to obtain the main excitation forces acting on the engine body.Then,the excitation force and modal data obtained by simulation were imported into LMS Virtual.Lab software and the method of modal superposition was applied to calculate the structural vibration and radiated noise of the engine.The results show that the simulation results are in good agreement with the test results,the dominating order and the amplitude of the vibration are all similar,the maximum radiated noise error difference is 3.6 dB(A).The analysis provides foundation for engine noise optimization.