Multi-field Coupling Analysis Method And Optimization Of Oil Injection Lubrication For Planetary Gearbox Gear Lubrication

Planetary transmissions are widely used in various on-road and off-road machinery products.How to achieve reliable lubrication is one of the challenges that all engineers need to break through.With the rapid development of computational fluid dynamics(CFD),it has become a reliable technical route to reproduce the lubrication behavior of key components in engineering practice and guide the design through numerical simulation of flow.In this study,CFD theoretical calculations are carried out for the lubrication problem of an NGWtype planetary gear train,and the ideal lubrication and no-load loss evaluation strategy is determined through the comparative analysis of three gear lubrication multi-field coupling strategies.Subsequently,a new oil injection lubrication mechanism is analyzed around the NGW-type planetary transmission system with an electric drive gearbox,and the effects of fluid characteristics and injection hole structure on lubrication behavior and injection torque are evaluated,and an optimization scheme of the injection hole structure is proposed.Finally,a mathematical model of injection torque is constructed for the component with the largest torque-the planetary frame.The main research contents and methods include the following:1.Numerical simulation methods and comparative analysis of multi-field couplingThe basic principles and control equations of the three mesh processing strategies are introduced,and the method of implementing CFD numerical simulation of gear lubrication based on the finite volume method is determined.Relying on the same flow control equations and turbulence calculation methods,the flow field information such as oil phase distribution,resistance moment,pressure distribution and velocity distribution obtained by the three multi-field coupling strategies are evaluated.The results show that the dynamic grid strategy can obtain the oil distribution results closest to the experiments,but the iterative solving process consumes the most computational resources.The sliding mesh strategy achieves the simplification of the mesh motion,but the redundant intersections in the flow field increase the error of flow field information transfer.When applying the immersion solid method,the mesh does not undergo actual motion,but its automatically generated flow-solid intersection interface has a large difference compared with the original model,which affects the oil distribution near the wall.2.NGW planetary gear system oil injection lubrication influence factor analysis and structure optimizationA three-dimensional transient flow analysis model is constructed by applying the dynamic mesh technique,and the effects of different oil characteristics and oil injection port structures on the volume fraction of oil on the surface of planetary wheel system components and the amount of wet clutch oil supply are analyzed.The main influencing factors on different component lubrication and ring clutch oil supply are identified,i.e.,the oil supply volume of the oil injection port lubricant,the diameter,and the number of oil injection ports had the most influence on this new oil injection jet behavior.Structural optimization of the sun gear oil injection port is given,and the optimized oil injection lubrication system increases the volume fraction of oil on the component surface and provides a stable oil supply to the gear ring clutch.3.NGW planetary gear system oil injection torque characteristics analysis and mathematical model constructionThe effects of different oil flow rates,densities,viscosities,axial positions,diameters,and numbers of oil injection holes on the component oil injection torque are analyzed,and the largest body of torque in the planetary gear system is found to be the carrier,which clarifies the effect of the lubrication enhancement optimization scheme on the component oil injection torque.Compared with the original design,the proposed lubrication optimization strategy can not only increase the oil volume fraction on different component surfaces but also reduce the oil injection torque.A mathematical model for the analysis of the planetary frame torque during the rotation of the oil injection hole is established,which provides a more economical analysis strategy for engineering designers.