内燃机2阶激励引起的车内噪声预测及优化OA

A method for predicting interior noise of vehicles caused by second-order excitation of internal combustion engine(ICE)was proposed.Firstly,combustion gas pressures in the cylinders were measured under a certain rotation speed,and then the pressures were applied to the multi-body rigid-flexible coupling model of the ICE to simulate the inertial loads of moving parts.Secondly,combustion gas pressures and inertial loads were simplified as the resultant loads and resultant torques applied at the crank center.Both loads and torques were transformed into the frequency domain based on Fast Fouri-er Transformation,and their 2nd order loads and torques were extracted as the second-order excitation of the ICE.Thirdly,the excitation forces were shifted from crank center to centroid of powertrain assembly,and applied to the vehicle mode for modal frequency response analysis to predicate the interior noise.Meanwhile,this interior noise was also tested.The compar-ison of simulation and test results show that both results of the sound pressure level curves have a good consistency in the frequency range from 50 to 110 Hz,which proved that this method is correct and effective.Finally,the transfer path,noise transfer function,operating deflection shapes and grid participation analyses were used to identify the weak area of the struc-ture,and then the drainage trough rack of front windshield was optimized,resulting in 5.4 dB decrease of the peak sound pressure level at the frequency of 65 Hz.