An Analytical Study Of Piston Secondary Motion And Prediction Of Impact Noise

The impact noise is an important aspect of the internal combustion engine vibration and noise control. The 12V620 diesel is selected as the research object in this paper and the secondary motion of piston and impact noise of this diesel is studied in detail.The thermal field of the whole piston was calculated with ANSYS, close to the experiment result. Then the distortion of the piston skirt can be got, which affects the clearance between piston and cylinder, proving that the secondary motion is intenser in thermal state than in cold state. The model of piston secondary motion is established by considering the hydrodynamic lubrication between the piston and cylinder. In this course, Reynolds equation is founded and numerical method is used. Simulation of piston secondary motion to 12V620 diesel is dealt with GLIDE to analyze the structure parameters which affect the motion.The finite element model of engine block and oil pan was built with ANSYS. The distortion process of model was studied by transient dynamic analysis under the impact force of piston. Based on this, the paper studies transient sound field of the block and oil sump surfaces by using the infinite element method with SYSNOISE. And the contrast analysis on impact noise is carried on in different diesel operating modes. It is found that impact noise increases as the rotational speed is higher and decreases when piston has a certain pin eccentricity. In addition, cylinder pressure is loaded on the model to analyze which external load is more important to combustion noise and impact noise. It is proved that impact of piston has the leading effects on mixed noise.