MODELING STARVATION EFFECTS IN PISTON SKIRT’S ELASTOHYDRODYNAMIC LUBRICATION AT INITIAL ENGINE START UP CONDITIONS

Abstract

There always has been a desire of improving the performance and efficiency of an automobile engine in order to reduce energy usage and control the losses. As a result the demand for better performance of important engine components has increased. Friction forces between surfaces of components in relative motion with each other are major source of energy loss in an IC Engine. There are many sources of friction in IC Engines such as Piston Assembly, Connecting Rod, Bearing, Valve train, Oil and Water Pumps and other components. Studies revealed that Power Cylinder (Piston and Ring/Liner) contributes a significant portion of mechanical friction losses. In general Piston Skirt–Liner conjunction is considered as major source of engine rubbing friction and cylinder friction power loss (1). Inadequate Skirt-Liner lubrication due to starvation has dramatic impact over the entire system efficiency. Piston Skirts experience starved elastohydrodynamic lubrication at engine startup and at some points along their stroke in normal operation. It is therefore quiet important to understand lubricant starvation and consider its effect. Starvation, as the name signifies is inadequate lubricant supply conditions. The aim of this research is therefore to mathematically model hydrodynamic and elastohydrodynamic lubrication of piston skirts under starvation conditions at initial engine startup. The mathematical model, thus developed will be used for prediction of lubrication behavior of piston skirt under various degrees of starvation. The results will be compared with those under fully flooded lubrication conditions in order to study the effects of starvation.