Experimental and Theoretical Evaluation of Simultaneous Piston Assembly, Valve Train and Engine Bearing Friction in a Fired Engine

Abstract

Engineers are constantly challenged to develop advanced products to meet more demanding emissions and fuel economy targets. In the past 20 years the automotive industry has greatly improved vehicle fuel efficiency by detailed engine component design improvement and formulating compatible lubricants, heavily relying on the computer based analytical tools. The sophistication and other complexity of these tools are growing rapidly. It is therefore important that the models, on which these techniques are based, are validated and continually improved by experimental techniques. For validating a predictive friction model, very accurate friction force data is required. Truly representative results can only be obtained if experiments are undertaken on a real fired engine and the friction loss in each component is recorded. The main aim of this research work is to validate an engine friction mathematical model called FLAME (Friction and Lubrication Analysis Model for Engines), over a range of load, engine speeds and lubricant temperatures, using 0W20 lubricant. The model was developed in a separate study and comprises of three parts, addressing each of the main tribological components (piston assembly, valve train and engine bearings). The validation was carried out by characterising the frictional losses generated from the major tribological components of a real fired engine. This was achieved by experimentally determining simultaneously the power loss in each component of a single cylinder, four valve, Ricardo Hydra gasoline engine under fired conditions.