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Elasto-Hydrodynamic Lubrication (EHL) analysis of a fully flooded piston skirt-liner conjunction is a useful methodology for design analysis of pistons. However, under typical engine operating conditions, oil present in the clearance region between the skirt and liner is sufficient to wet only a portion of the piston skirt (partial skirt lubrication). The reduction in damping due to partial skirt lubrication is an important consideration to address issues related to piston slap noise, liner cavitation and other noise and vibration aspects. The existing simulation methodology for EHL analysis of a fully flooded piston skirt uses a finite-difference scheme to solve the coupled Reynolds, Greenwood-Tripp and elasticity equations in order to calculate the nodal oil film pressures, contact pressures and elastic deformations respectively. Detection of cavitation zones within the oil film done via implementation of the Half-Sommerfeld boundary condition.

This paper demonstrates the effect of elastic deformation of the cylinder wall on the lubrication between the skirt and cylinder with simulation results of two realistic examples. The simulation methodology is described. Cylinder flexibility caused substantial changes in slap motion, average and peak wear loads on the skirt, friction, and power losses due to asperity contact and hydrodynamic friction. Cylinder deflection due to side loads was about ten percent of the skirt deflection due to side loads, and deformation due to cylinder gas pressure was substantial.

Using skirt-liner clearance and cylinder pressure measurements provided by Isuzu Motors, Ltd. of a production type gasoline automotive engine, a validation study was done of Ricardo's PISDYN code, which predicts the secondary motions and skirt liner elastohydrodynamic lubrication of pistons. Predictions using the computer code of the skirt liner clearance at two locations on the skirt were compared with measured results. Using the code, parametric studies were done. Very good qualitative and quantitative agreement was found for the baseline cases. In the parametric studies using the code only, the following were found: The predicted clearances were very sensitive to variation in cold minimum clearance. The effect of cylinder induced pressure deformation was significant, especially near the point of peak cylinder pressure. Increasing the cylinder pressure increased the peak clearances. Changing the asperity roughness height affected the clearances near a point of asperity contact only.