Optimization of the piston assembly friction

Abstract

The present paper points out that improvements of the piston assembly friction necessitate a high level of system knowledge, which requires experimental investigations. Therefor the self-developed research engine of the Institute of Internal Combustion Engines of the Technical University of Munich is introduced. Besides the high accuracy of the measurement device a well-defined testing procedure is important to analyze the influence of specific design changes of the piston assembly on their frictional behavior. The presented testing methodology developed by the Institute guarantees the comparability of different testing configurations.

Crank angle resolved measurements of two top ring design features were presented, which prove the positive influences regarding the piston assembly friction of a low friction coating and an optimized shape of the running face. The results illustrate in detail that these particular design changes only affects the friction force in the expansion stroke within high cylinder pressures. Although the impact on the friction force is pretty similar for both design changes the given reasons for the effects differs. Furthermore, the results show that with higher engine load and lower speed the improvement of the frictional losses increases. Thus, both design changes are an effective way to optimize the mechanical efficiency of an internal combustion engine.