Generalized analytical model for evaluating the gear power losses transition changing from windage to churning behavior

Abstract

Although splash lubrication is usually adopted in the intermediate or tail gearbox of helicopters at low or moderate speed, and it appears that the oil jet lubrication used in a high-speed main reducer of helicopters would be turned into the splash lubrication that only a small part of gears is immersed in the oil sump due to the lubricating oil deposition by the mismatch between the oil feed and return. The classic drag power losses model is either used for the churning behavior of common splash lubrication or the windage behavior of oil jet lubrication, and is no longer suitable for this transition phenomenon of these two behaviors coexist. In this paper, a theoretical analytical method by introducing the windage contribution factor and air-oil ratio evolution model is proposed to predict the associated power losses for one single spur gear rotating partially immersed in an oil bath. To verify the accuracy and correctness, the theoretical calculations are then compared with the existing experimental data from Quiban et al. [33]. Based on this method, a generalized analytical model to evaluate the gear drag power losses for the windage, churning phenomenon and their transition behavior are established.