Optimisation of piston compression ring for improved energy efficiency of high performance race engines

The primary function of the piston compression ring is to seal the combustion chamber from the bottom end of the engine. As a result its conformance to the cylinder liner surface is of prime importance. This close contact contiguity results in increased friction, making this contact conjunction responsible for a significant proportion of energy losses. The frictional losses can be as much of 2-6% of expended fuel energy, which is quite significant for such a diminutive contact. Under these conditions, geometrical profile, surface topography and inertial properties of the ring assume significant importance. The paper presents an integrated mixed-hydrodynamic analysis of the compression ring-cylinder liner contact with multi-parameter optimisation, based on the use of genetic algorithm. The multi-objective functionality includes minimisation of parasitic energy loss, reduction of incidence of asperity level interactions as well as minimisation of ring mass. Both cold and hot running engine conditions in line with the New European Drive Cycle have been considered. Hitherto, such an approach has not been reported in literature.