Parameterisation of friction in engine piston-cylinder assembly

Abstract

Commonly used empirical or semi-empirical global friction models in IC engines are insufficient in terms of precision needed for global optimisation of power train system and more attention must be paid to simple, yet effective comprehensive angle-resolved, analytical models. In this paper, detailed Stribeck’s theory based analytical angle-resolved model is employed to simulate major friction loss in contact of piston ring assembly (PRA) and piston skirt (PS) to engine cylinder, respectively. Widely used simplifications in both slider mechanism dynamics and heat release rate simulations are avoided in order to achieve improved sensitivity and accuracy. The parameterisation enables one to encounter for the effects of gas pressure and combustion dynamics, crank- slider dynamics, piston ring geometry and lubricant viscosity to engine friction losses. Gas pressure trace and engine indicated torque have been simulated by means of a nonlinear, detailed, two-zone, zero-dimensional multi-cylinder SI engine combustion model. The piston ring to cylinder (PRAC) and piston squirt to cylinder (PSC) friction components ratio has been introduced to analyse this phenomena in angular domain.