Experimental analysis of piston slap from small two-stroke gasoline engine

摘要

This project is an experimental investigation and optimization of piston slap noise in a small two-stroke gasoline engine. Piston slap is one of the most significant mechanical noise sources in an internal combustion engine. It is a dynamic impact phenomenon between the piston and the cylinder block caused by changes in the lateral forces acting on the piston. The change in cylinder block vibration level caused by the piston impact is considered as a measure of piston slap during this experiment. The intensity of piston slap is measured in terms of vibration level in "g" units, by means of accelerometers mounted on the cylinder block with Top Dead Center (TDC) and Bottom Dead Center (BDC) marker. For the design of low-noise engines, all the major parameters, which contribute to piston slap, are listed and the critical four are examined through additional experiments. The four critical parameters are the piston pin offset, piston-to-cylinder block cold clearance, skirt length and cylinder block thickness. The experimental work, considering the above critical parameters, was planned according to the statistical technique called Design of Experiments (DOE). This technique gives all the possible combinations of experiments and its interaction effects on the piston slap intensity. The results obtained from above procedure are further analyzed with ANOVA (analysis of variance) and conclusions are drawn based on this analysis. It was found that piston pin offset and piston- to-cylinder block cold clearance were dominant among the design parameters selected for experimentation. These optimized design values are recommended for production.