LUBRICATION ANALYSIS BETWEEN PISTON AND CYLINDER IN HIGH PRESSURE PISTON PUMP CONSIDERING CIRCUMFERENTIAL GROOVES AND VISCOSITY VARIATION WITH PRESSURE

In this study, a theoretical study on the lubrication analysis of an axially moving tapered piston with circumferential grooves subjected to a large pressure gradient within cylindrical bore has been done, Taking into account viscosity variation with pressure, analytic expressions for the pressure distribution leakage are obtained solving modified one-dimensional Reynolds equation for the case that the cylinder and the multi-grooved piston axis has uniform eccentricity. It is shown that the viscosity variation with pressure highly affect the pressure distribution, lateral force acting on piston and leakage flow rate. Numerical solutions of two-dimensional Reynolds equation are also presented to confirm the validity of the analytical results. It is recommended that the piston used in various piston pumps should be tapered toward its high pressure end.