Modeling and Performance Analysis of Direct Acting Valve Train System

Abstract

Engine manufacturers all around the world are trying to find ways to reduce fuel consumption during the engine operation to improve overall efficiency. Major fuel losses occur due to thermal and mechanical losses. The focus of this research work is on mechanical losses in engine valve train. Different researchers have developed valve train friction models to analyze the tribological performance of engine valve train. Valve train frictional loss is mostly due to the interaction between cam and tappet. Friction models developed by Yang (1992) and Zhu (1988) have been used with changes to develop new mathematical model to analyze the effect of lubrication on the friction at cam/tappet, tappet/bore and valve/stem interface. In these model effects of tappet rotation is also examined on friction and power loss. Matlab software has been used to develop software for valve train friction. Different parameters like camshaft speed, dynamic viscosity etc. have been changed in the parametric study to analyze effects on minimum film thickness, vertical loading, friction due to asperities, shear friction and power loss.