某汽油机本体振动噪声分析及优化

Analysis and optimization on vibration and noise of a gasoline engine body

为解决某汽油机本体振动大问题,通过噪声、振动、声振粗糙度(noise vibration harshness,NVH)测试分析,确定导致发动机本体振动大的原因;研究缸体模态提升和燃烧优化对降低发动机振动噪声的效果,并设计专项试验进行对比验证。发动机NVH性能测试和声学相机测试结果表明发动机本体振动大的原因为发动机结构较弱和燃烧激励较大。安装曲轴箱加强板后缸体模态提升显著,缸体一阶扭转模态频率提高了61.4%,一阶弯曲模态频率提高了5.7%,缸体裙部振动下降明显;在链轮室盖增加固定螺栓后,振动加速度导纳和由3.2 g/N降低到1.2 g/N,相同激励下部件产生振动噪声的风险显著降低;燃烧优化后,发动机特定转速点的整体(含附件)振动能量降低明显,但发动机动力性、经济性略有下降,需要综合评估燃烧优化对整机性能的影响。

To solve the problem of large vibration of a gasoline engine,noise vibration harshness(NVH)tests are conducted to analyze and determine the causes of large vibration of the engine body.The effects of cylinder modal improvement and combustion optimization on reducing engine vibration noise are studied,and special tests are designed for comparative verification.The results of engine NVH performance testing and acoustic camera testing indicate that the reason for the high vibration of the engine body is due to the weak engine structure and high combustion excitation.After installing the crankcase reinforcement plate,the modal of the cylinder body significantly improved,with a 61.4%increase in the first-order torsional frequency modal and a 5.7%increase in the first-order bending frequency modal.The vibration of the cylinder body skirt decreased significantly.After adding fixing bolts to the sprocket chamber cover,the sum of vibration acceleration admittance decreases from 3.2 g/N to 1.2 g/N,and the risk of component vibration noise under the same excitation conditions is significantly reduced.After combustion optimization,the overall(including accessories)vibration energy of the engine at a specific speed point decreases significantly,but the power and economy of the engine slightly decrease.It is necessary to comprehensively evaluate the impact of combustion optimization on the overall performance of the engine.