Modeling Rough Piston Skirts EHL at Very Low Initial Engine Startup Speeds - Pressure Flow Factors Effects

Syed Adnan Qasim, Mubashir Gulzar, Riaz A. Mufti, and M. Afzaal Malik


Mathematical modeling, Modeling and simulation methodologies, piston EHL, Surface roughness, Initial engine start up


Prevention of wear of the rough piston skirts and the cylinder liner surfaces in the absence of a fully developed elastohydrodynamic lubricating (EHL) film is a major concern in the initial very low engine start up speeds. This study models the isothermal piston skirts hydrodynamic and EHL numerically at a very low engine start up speed. A high-viscosity grade engine lubricant is used and same roughness of the interacting surfaces is assumed. The pressure flow factors representing the surface roughness are incorporated in the 2-D Reynolds equation, which is solved to generate the hydrodynamic pressures. The inverse solution technique is used to generate the EHL pressures between the rough surfaces. The equations defining the secondary motion of the piston, contact geometry and the pressure dependence of viscosity are incorporated in the mathematical models. The simulation results show the effects of pressure flow factors on friction, eccentricities, velocities, hydrodynamic and EHL pressures and film thickness profiles. The study is extended to a lower speed to generate results for comparative study and analysis. The outcomes suggest that pressure flow factors affect the viscous friction and the piston eccentricities. The hydrodynamic pressures and film thickness profiles improve at the given load and speed conditions. The comparative study suggests optimizing the very low start up speed under the stated conditions.

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