Experimental investigation of the oil jet heat transfer on meshing spur gears

Designing an adequate cooling system for a high-speed high-power gearbox of a geared turbofan requires a thorough understanding of the cooling capabilities of the utilized oil jet impingement. An experimental setup is employed to determine the heat transfer coefficient on gear teeth in various non-meshing and meshing configurations, which incorporate inclined jets with varying distances between the impingement and the meshing zones. The direction of heat transfer is inverted in the experiments to allow for a feasible setup with the rotating gears, where impinging oil jets heat the hollow instrumented gear as its inner surface is cooled via air jet impingement. Measurements with varying oil volume flow rates and rotational speeds are carried out. The losses are analyzed to enable an isolated investigation of the heat transfer between the oil and the gear via measured temperatures on the gear teeth. Heat transfer coefficients are compared at the lower rotational speed with relatively small meshing losses. The meshing in the experimental setup does not have a significant influence on the mean heat transfer coefficient. The spatial distribution of the heat transfer coefficient is slightly affected by the meshing teeth as the distribution gets more uniform with decreasing distance between the impingement and meshing zones.