Instantaneous friction components model for transient engine operation

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Abstract
An engine friction model is developed in order to determine the instantaneous friction components at any crank angle during the overall engine response. In order that it can be meaningfully incorporated in overall engine control models, the engine friction model should represent the relevant trends but be relatively simple to compute. The main friction components are the piston assembly, the bearing, the valve train and the auxiliaries. The model includes new analytically derived equations for the friction components of the ring assembly, the bearing with mixed lubrication and the valve train. Many factors contribute to the successful starting of diesel engines and one of them is the effect of engine friction due to high oil viscosity (cold start) on engine startability. The model takes into consideration the effect of temperature variations on the viscosity of the oil. The friction equations are based on theoretical calculations for hydrodynamic and mixed lubrication (where the oil film has collapsed). They rely on Reynolds equation and dynamic analysis. Simulation results are presented, which compared with experimental data indicate an accuracy of more than 97 per cent.

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