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The Greenwood model has been extensively used for calculation of the asperity pressures under mixed lubrication conditions, but usually assuming that the surfaces are gaussian. In this work, the Greenwood parameters are calculated from actual, non-gaussian, engine surfaces measured by White Light Interferometer. Results from 2D profiles and 3D measurements are compared. An improved way to calculate the Greenwood parameters and to apply them for estimation of the contact area and pressure is described. To illustrate the methodology, some examples of topography characterization and modeling for engine liners are presented. The influence of the asperity summit height average on the predicted contact area calculation is discussed. To explore and validate the proposed method, several WLI measurements from different engine HDD liners were analyzed using a proprietary code.

This paper describes the development of a low friction power cell (piston, piston rings, connecting rod and bearings) for a spark-ignition 1.0 liter engine with the help of mathematical simulations. Using numerical modelling, small variations in friction power loss can be studied, which would be impossible by actual engine tests due to uncertainties in measurement process. Although it was not possible to experimentally quantify the individual component gains, the increase in engine brake power measured with the engine running with the original and modified power cells correlates very well with the simulated values.