Parameter design method for the heat transfer performance of a fan-driven gearbox under planetary gear opening and oil-return conditions

On the basis of the computational fluid dynamics (CFD) method, this study calculates the surface convective heat transfer coefficients of the sun gear, planetary gear, ring gear, and bearing before and after the opening of the planetary gear of a fan-driven gearbox. A numerical fitting method is used to establish the calculation model of the convective heat transfer coefficients of the sun gear, planetary gear, ring gear, and bearing under the open-hole oil-return condition. The convective heat transfer coefficients of each element are compared before and after the hole is bored, and the design method for the gearbox parameters with the objective of heat transfer performance is proposed. Result shows that the convective heat transfer coefficients of each element are increased after oil is returned from the hole of the planetary gear, and the change rate of the convective heat transfer coefficient of the raceway in the planetary gear bearing is the highest. When the aperture of the planetary gear is 7 mm and the number of holes is four, the heat transfer performance of the gearbox is the best. The maximum error between the convection heat transfer coefficient fitting formula value and the CFD simulation calculation result is 1.0558 %.