Study of Engine Vibration Due to Piston Slap on Single Cylinder High Powered Engine

The piston slap is an important phenomenon in the engine, which governs the vibration, noise, and wear of liner surfaces. It occurs due to transverse and rotational motion of piston, which depends on clearance between piston and liner and is governed by geometry, mass and inertia properties of reciprocating parts, and gaseous loads. Piston slap is studied on single cylinder high-powered engine, which showed large vibrations and noise during the field trials. The classical methodology is used to determine secondary movement, contact forces and kinetic energy loss due to piston impact. The calculated result showed no major impact of piston on liner surfaces due to presence of hydrodynamic lubrication between two mating surfaces. The loss of kinetic energy due to the impact is of the order of 0.007 Nm, which is negligibly small. The calculated values were compared with measured field trial and engine dynamometer test results, and observed predominant frequency value of 36 Hz, which is much lower to normal piston slap frequency value of 200 to 400 Hz. In addition, the engine endurance experimental results showed no severe marks on the piston and liner surface. This clearly indicated that the problem is not due to piston assembly. The technique is extended to predict the wear of critical engine parts like piston and liner surface. Thus, the finite element method and piston transverse movement calculation technique is satisfactorily used to predict engine vibrations and noise due to piston slap.