Folded Metal Effect on Lubricant Film Thickness and Friction Using a Mixed Lubrication Deterministic Model 2014-36-0302
Despite the influence of folded metal material on the lubrication performance of engine cylinder liners has been largely investigated, its effect has not been isolated yet in terms of other surface parameters as Sa, Sq, Vo, Rpk etc.
In the present contribution, the isolated effect of folded metal on the performance of engine cylinder liners was investigated by comparing the hydrodynamic and asperity contact pressures through a deterministic mixed lubrication model. From that, the friction coefficients and the engine friction losses were also estimated.
The topography of a production car engine block was characterized employing a Non-Contact Surface Profiler System. Folded metal was quantified using in-house algorithms, and so its occurrences were digitally removed. Afterwards, the surfaces with and without folded metal were studied with the deterministic model.
The effect of the lubricant flow through the asperities located in the contact region between the parallel, flat lands of a twin-land oil control ring (TLOCR) and the cylinder topography was deterministically modelled based on the Reynolds lubrication equation, and the cavitation phenomena were taken into account by adopting the mass-conserving JFO formulation. The asperity contacts were also deterministically calculated for different surface separations. Finally, full-engine cycle simulations were also carried out in order to predict the global engine friction losses according to the “correlation factors” obtained from the deterministic model.