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