Piston Assembly Friction Losses: Comparison of Measured and Predicted Data

The main objective of this research was to validate the friction prediction capability of Ricardo Software products PISDYN and RINGPAK by comparing predictions with measured piston assembly friction force.

The measurements were made by the University of Leeds on a single cylinder Ricardo Hydra gasoline engine using an IMEP method developed by the University. This technique involves the use of advanced instrumentation to make accurate measurements of cylinder pressure, crankshaft angular velocity and connecting rod strain. These measured values are used to calculate the forces acting on the piston assembly including the friction force.

PISDYN was used by Ricardo to calculate friction force at the interface between the piston skirt and cylinder liner. The model used includes the effects of secondary dynamics, partial lubrication and piston skirt profile. RINGPAK was used by Ricardo to calculate the friction force at each piston ring. The total friction force due to skirt and rings was compared with the measured data.

Various parametric studies were undertaken to improve the correlation between measurement and prediction and to investigate the sensitivity of the models to uncertain input data.