Analysis of Piston Slap Induced Noise and Vibration of Internal Combustion Engine

This paper presents the analytical method to evaluate the impact force and engine noise induced by piston slap considering the detailed piston profile and dynamic characteristics of the piston. This method was applied to examine the effect of the piston profile and piston pin offset on the piston slap impact force and its induced engine noise. Present numerical method showed that increasing the upper clearance of the piston skirt enlarged the higher frequency components of the piston impact force and engine noise and this was verified by the experimental results. The analysis revealed that piston movement at the vicinity of the combustion top dead center was governed by the friction moment around the piston pin and the additional piston pin offset moment induced by combustion pressure could cancel this friction moment and reduce the piston impact force if the piston pin was offset to the major thrust side. This analytical results was confirmed by the measured results of actual diesel engine.