Abstract
In this study, we propose a computational fluid dynamics (CFD)-based method to study the lubrication and temperature characteristics of an intermediate gearbox with splash lubrication. A volume of fluid (VOF) multiphase model was used to track the interface between oil and air. A multiple reference frame (MRF) model was adopted to accurately simulate the movement characteristics of the gears, bearings, and the surrounding flow field. The thermal-fluid coupling computational model of an intermediate gearbox with splash lubrication was then established. Combined with experimental results, we verified that the lubricating oil temperature was below the limit requirement (<110 °C). The numerical results revealed that large amounts of lubricating oil were splashed onto the tooth surfaces near the gear meshing area. A large convective heat transfer coefficient corresponds to a low gear tooth surface temperature. The tooth surface temperature of the driving gear is higher than that of the driven gear. The distribution law of oil volume fraction of the bearing roller was jointly affected by the roller rotation direction and gravity. The convective heat transfer coefficient of the roller wall was largely related to the lubrication environment of the roller, including the oil distribution inside the bearing cavity and the flow rate.
Highlights
Splash lubrication [2,3,4] is widely used in intermediate gearboxes on account of its simplicity and reliability
Significant energy losses occur in the intermediate gearbox during operation, most of which are dissipated as heat
Temperature experiments were performed to obtain the temperature distribution across the casing and the end covers of the intermediate gearbox, and the oil temperature in the oil pool was measured as well
Summary
The transmission system, engine, and rotor system are the three critical dynamic components of a helicopter. The former is the only path of power transmission in a helicopter, and its performance can directly determine the service life of the helicopter [1]. Splash lubrication [2,3,4] is widely used in intermediate gearboxes on account of its simplicity and reliability. Predicting the temperature distribution of an intermediate gearbox is challenging, because the heat convection inside the gearbox is determined by the intermittent splashing behavior of the lubricating oil, which is relatively unknown. Studying the lubrication and temperature characteristics of an intermediate gearbox under splash lubrication remains a significant challenge
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