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.

Vane Geometry Effect on Lubrication Conditions between Vane Tip and Cam-Ring in Hydraulic Vane Machines

“…Increasing operating oil temperature increases coefficient of friction in the low temperature regions while decreases it at the high temperature regions. For vane pump that runs under different operating conditions, more than one oil type may be required to optimize its performance [1].…”

“…The effect of the radial vane force and the pressure difference between the two sides of the vane were found very small compared to other parameters such as vane relative speed. Coating material shows insignificant effect for the friction coefficient between vane tip and cam-ring in oil vane pumps [7].…”

“…Pressure distribution is simply replaced by Hertzian distribution "elliptic curve" (1). Theoretical models solving Navier-Stoke's equation (2) with elastic deformation were used for TEHL-model.…”

“…Elasto-hydrodynamic deformation due to very high pressure of lubricant between vane tip and cam-ring within contact area was modeled according to Hertzian distribution "elliptic curve" (1). Fig.…”

Analysis of vane loads and motion in a hydraulic double vane pump with integrated electrical drive

“…Inaguma [2][3][4] shows that this type of friction has a significant impact on the mechanical efficiency of a double-acting vane pump and that the friction force is proportional to the vane force, vane thickness and delivery pressure. Elashmawy [5,6] stated that the oil type used by the vane pump is an essential element influencing the pump performance. Faber and Ortwig [7,8] have carried out the experimental and theoretical investigations of friction between vanes and cam ring and developed theoretical model for the description of vane friction.…”