Simulation Of Fluid And Temperature Field Of A Spiral Bevel Gear Transmission System

As one of the most important parts of a drive system,a transmission mainly relies on multistage gears to realize aims like changing over,reducing speed and multiplying torque,etc.However,in the process of transmission,the existence of relative tangential velocity on the two tooth surfaces usually leads to a large number of heat.If there is no sufficient lubrication and cooling,failure modes like scuffing and gluing will occur.Therefore,studying the mechanism of oil movement and heat balance in the gearbox is of vital importance to its lubrication system,whether it is in the period of initial design or improvement.Based on an engineering project,this paper combines theory with CFD simulation to analyze the distribution of fluid and temperature in a complex gearbox.Main contents and conclusions are as follows:(1)Simplify spiral bevel gear to helical gear,then based on the theory of gear meshing and tribology,establish the equivalent model to calculate power loss of sliding friction.Then compare power loss rate with results of look-up table to verify the reliability of the theoretical model,which provides heat source for the analysis of temperature field in the subsequent chapters.(2)Simulate the rotation of a smooth disc and a spur gear in the air,and choose wall heat transfer coefficient as the criterion to compare simulation result with empirical formula.It appears that difference between the two is very small,thus a relatively accurate finite element modeling method is established.Then apply the method to simulate the fluid and temperature field of a pair of spiral bevel gears,and distribution of oil around the gears and temperature on tooth surfaces are obtained,Meanwhile,analyze why the distribution occurs.(3)Choose gear immersed depth,tooth width and rotation speed as variables to study how they affect the process of oil splash and tooth temperature.To sum up,as far as the flow field is concerned,decreasing gear immersed depth leads to an obvious decline of oil adhesion on tooth surface.And shortening tooth width will weaken the capacity of stirring oil of the teeth.When rotation speed increases,oil distribution on the gear surface is more uniform,but oil volume fraction on the tooth surfaces of meshing area are similar.For the temperature field,the correlation between temperature and gear immersed depth is not completely negative,and there is an optimal value of gear immersed depth.And temperature rises with the increase of tooth width and rotation speed.(4)Taking the system of bevel drive in a complex transmission as the research object,simulate its internal oil movement,and heat production of the moving parts calculated by theoretical formula is applied as boundary.Results show that lubrication in the system is not sufficient and temperature of the spiral bevel gears is too high.Give improvement suggestions from the two aspects of local structure of the gearbox and initial height of oil level,and reanalyze the model.It appears that the improvement measures are effective,which provide a reference for the subsequent optimization of the lubrication system.