Simulation Analysis of the Splash Lubrication of the Main Gearbox for Unmanned Helicopters

The main gearbox of unmanned helicopters operates under complex, high-speed, and variable conditions, making lubricating oil behaviour under splash lubrication difficult to characterize and churning power loss mechanisms unclear.In this study, a computational fluid dynamics (CFD) model of the main gearbox was established to investigate lubricant flow behaviour and power dissipation in the helicopter main transmission.In particular, a numerical model was built via the moving particle semi-implicit (MPS) method.The distribution pattern of the lubricating oil in the gearbox, and the characteristics of the churning power loss under different conditions were evaluated.Results demonstrate that lubrication characteristics are influenced by the splashing effect caused by gear rotation and the fluidity of the lubricant.Churning power loss increases with gear speed and initial oil quantity, while it decreases as lubricating oil temperature rises, exhibiting a nonlinear trend overall.The proposed method provides a theoretical basis for optimizing the splash lubrication scheme and improving the energy efficiency of the main gearbox of unmanned helicopters.