An Investigation of Viscosity Effects on Axial Piston Motor Efficiency
This paper examines the relationship between axial piston motor efficiency and viscosity. The volumetric, mechanical, and overall efficiencies of hydraulic motors were measured under steady state conditions. Newtonian and non-Newtonian antiwear hydraulic fluids were evaluated at 50°C and 80°C. Dimensionless viscosity values for mechanical, volumetric, and overall efficiency were compared to the classic Stribeck curves. The experimental curves for volumetric and overall efficiency were consistent with the classic efficiency model. Mechanical efficiency diverged from model behavior at low Stribeck numbers; declining at low speeds and high pressures as contact conditions transitioned through the mixed-film lubrication regime. A new model for relating the viscosity to volumetric and mechanical efficiency is presented.