| As the main transmission system of geared turbofan(GTF)aeroengine,the double helical star gear system needs to meet the requirements of high speed,high load capacity and ultra-high transmission efficiency.The high speed rotation of gear agitates the surrounding air violently,and the power loss caused by windage will become an important source of total power loss of gear system,which requires enough attention.When the gears are lubricated by oil jet,the two-phase flow formed by the mixture of high speed air flow and lubricating jet is complicated and changeable.If the tooth surface is not well lubricated,friction loss will be increase.Therefore,it has great theoretical and engineering significance to carry out the windage analysis and oil jet lubricating state prediction of high speed double helical star gear system for reducing the windage power loss,improving the lubrication effect and promoting the transmission efficiency.Aiming at the high speed double helical star gear system,in this paper,the applicability of various transient flow field modeling methods for gear pairs are compared and analyzed,the system’s windage loss and the windage reduction effect of the gear cover structure are simulated and analyzed,and then the oil jet lubrication of the gear system is simulated.The main research points are as follows:(1)The dynamic mesh method,sliding mesh method and immersed solid method are used to simulate the external air flow field of single-stage high speed double helical gear pair,respectively.The simulation results of velocity field,pressure field and calculation time of different models are compared.Based on the comprehensive evaluation of the accuracy and efficiency of the simulation results,it is concluded that the dynamic mesh method is more suitable for modeling and simulation of the external flow field of the gear pair.(2)The calculation model of single-phase air flow in double helical star gear system is established.The transient characteristics of air flow around the gear are simulated and analyzed,and the mechanism of windage loss is clarified.The windage torque of gear is extracted,and the windage power of double helical star gear system is calculated.By comparing the windage power of gear system with different rotating orientation and speed,it is concluded that the windage power is not affected by the change of orientation,but approximately proportional to the third power of speed.(3)The methods to suppress the windage loss of the gear system are analyzed.According to the gear cover windage reduction scheme,the windage power of the gear system with different cover clearances are simulated and calculated.It is concluded that the smaller the gear cover gap,the better the gear windage reduction effect.Aiming at the low drag structure,the law of windage power changing with speed is studied,and the windage loss power of gears before and after using windage reduction structure and the windage reduction effect at different speeds are compared and analyzed.(4)Based on the theory of two-phase flow and dynamic mesh method,the oil jet lubrication simulation model of double helical star system with gear cover is established.By analyzing the lubrication effect on the meshing in or meshing out side,the jet lubrication scheme on the meshing in side and the structural parameters of the nozzle are determined.Then the lubrication characteristics of the gear system are analyzed,and the oil movement state,the oil-gas ratio of the tooth surface and the mass flow of the lubricant in the meshing area are obtained.The results show that the double helical star gear system has good lubrication effect. |
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