Research On Dynamic Efficiency Of Double Helical Star Gear Trains

Compared with the conventional turbofan engine,star gear box is added between the fan and the turbine in Geared Turbofan Engine(GTF),which makes the fan and the turbine functioning in suitable speed and high efficiency.Design of star gear box is the key technique in the design of high efficiency geared turbofan engine to reduce fuel consumption.Based on this situation,this paper focused on the research on dynamic efficiency of double helical star gear trains.Research of FEA on gears meshing and dynamic analysis of the double helical gear were carried out.In the research of FEA,a method of mesh generation was proposed according to the meshing characteristics of helical gear.As the tooth surface grid nodes were sequentially loaded,the tooth surface flexibility coefficients matrix was obtained by finite element calculation.Helical gear contact model was established based on this matrix.By introducing boundary conditions and deformation compatibility conditions,the equilibrium equations are established.Meshing stiffness,load-sharing ratio can be obtained by the solution of equations.In the analysis of the dynamic characteristics,dynamics model of the internal and external engaging double helical gears was established,which takes the sliding friction,time-varying stiffness,axial vibration as well as mutual influence of gear vibration at left and right ends into account.Vibration displacement was obtained by solving the dynamic equation with the Runge Kutta method,then tooth surface load distribution can be calculated by contact model with the vibration displacement.Power loss calculation model was established to get the dynamic efficiency by choosing friction coefficient model based on elastohydrodynamic lubrication theory.Based on the above,the influence of macro,micro structure and lubrication parameters of gear pair on the transmission efficiency is analyzed,and efficiency optimization model was proposed.Finally,a dynamics model of double helical star gear trains considering sliding friction,time-varying stiffness was established to get the accurate tooth surface load distribution,and vibration characteristics was analyzed.A power loss calculation model for star gear system was established to analysis the influence of gear parameters on the transmission efficiency.At last,parameters of star gear trains were optimized to estimate increasement of the efficiency.