The effect of load and viscosity on the minimum operating oil film thickness of piston-rings in internal combustion engines

Abstract

Computer simulations are now routinely used in the design and analysis of ring packs for internal combustion engines. Commonly they predict that an increase in engine load decreases minimum operating film thickness because oil availability and oil transport through the ring pack are reduced under these conditions. To assess the reliability of new simulations, investigators compare the output of computer models with experimental measurements of parameters on operating engines. Contributing to this process this paper presents an experimental study of an investigation into the effect of load on the minimum oil film thickness between piston rings and cylinder liner in a fired compression ignition engine. Oil film thickness data were collected using capacitance-based transducers located near top dead centre and mid-stroke. Experiments were performed at 2000 r/min using two mono-grade oils (SAE 50 and SAE 20) and one multi-grade oil (SAE 5W50) under a range of fixed engine loads. The experimental data obtained are discussed in the context of experimental and theoretical work published by other investigators.