Theoretical Investigation of Friction Forces between Vane Tip and Cam-Ring in Oil Vane Pumps

Abstract

Oil type used for oil vane pumps is an essential element affecting its performance. Trying to understand oil type effect and proper oil type selection will lead to significant enhancement of oil pump performance and increase its life time. In order to accomplish this task, a simple thermo-elasto-hydrodynamic lubrication (TEHL) model was used to calculate the friction forces between vane tip and cam-ring. Effect of oil temperature, vane relative speed, normal vane force, and oil film thickness were theoretically investigated for different oil types. Navier-Stokes and energy equations were numerically solved using finite difference technique. Viscosity and density distributions as a function of oil pressure and temperature were taken into consideration. Results show that proper oil type selection and its operating temperature are key parameters that significantly affecting the vane pump performance. The vane relative speed is quit important parameter affecting the coefficient of friction and should not be less than 5 m/s. increasing of lubricant film thickness is not necessarily enhances the friction coefficient between van tip and cam-ring. The study shows that the best type of oil for vane pump in some operating conditions is not necessarily the best choice for this pump in other operating conditions. It may be helpful for designers to select more than one oil type for the same pump according to its operating conditions