Hydraulic Fluid Efficiency Effects in External Gear Pumps

摘要

This paper presents an experimental study of external gear pump efficiency based upon an analysis of the Stribeck values. The volumetric, mechanical, and overall efficiencies of a variety of external gear pumps were measured under steady state conditions. Straight grade antiwear hydraulic fluids were evaluated at 50°C and 80°C. Stribeck values for mechanical, volumetric, and overall efficiency were compared to classic pump efficiency curves. The experimental curves for pump volumetric and overall efficiency were consistent with the classic pump efficiency model. Mechanical efficiency diverged from model behavior at low Stribeck numbers; declining at low speeds and high pressures as contact conditions transitioned from the hydrodynamic to the mixed-film lubrication regime. A simple expression for relating the Stribeck number to volumetric and mechanical efficiency is presented. This model is used to compare the efficiencies of hydraulic fluids in a backhoe loader trenching and loading cycle. The results indicate that fluid efficiency differences increase with the workload intensity.