An experimental investigation of windage and oil churning power losses of gears and discs

Abstract

This study presents comparable sets of churning and windage power loss measurements of a gear. Measurements are performed under windage (air only) and churning (immersion in oil up to a certain level) to quantify load-independent power losses of a family of spur and helical gears along with representative discs. Aiming at quantifying the impact of gear geometry on churning or windage losses to establish a baseline for the case of no enclosures around the gear, the test matrix is designed to investigate three key items: (a) contribution of losses along the periphery and faces, (b) the influences of gear teeth versus a toothless replacement disc as well as key design parameters (gear module and helix angle), and (c) a comparison of churning and windage power losses measured from the same exact set-up. The churning power losses are shown to increase with the static oil levels due to increased solid-fluid interactions. The impact of oil bath temperature (oil viscosity) on churning loss is observed to be more pronounced for higher oil levels. The presence of gear teeth on the rotating specimen (spur or helical) cause churning loss to increase modestly in comparison to the disc specimens. Furthermore, a larger tooth size results in higher churning power losses. The influence of gear teeth (gear vs. disc) on windage loss is shown to be significant, indicating that modeling a gear in a high-speed windage condition as a cylindrical disc might not be an acceptable practice.