Dynamic Simulation Analysis And Optimization Of Double Helical Planetary Gear Transmission System

Double helical planetary gear transmission system has significant advantages,including litter axial thrust forces,high load carrying capacity,low noise,and stable operation,which is widely used in ship,aerospace,aviation,and high precision transmission machine.Double helical planetary gear reducer performs as a transmission machine between the turbine and the fan of a GTF aero-engine,of which the service environment is extremely demanding,and the internal dynamic excitations are complex and variable,causing prominent system vibration and noise problems.Therefore,the research involving dynamic analysis and optimization design of transmission system shows important theoretical significance and engineering value.The research object of this paper is double helical planetary gear transmission for GTF aero-engine,considering the internal nonlinear coupled dynamic excitation of the system,and focusing on the key problems of system coupling dynamics modeling,natural characteristics,dynamic response and load distribution features,and dynamic performance optimization.The main contents in this paper are as follows:(1)Accroding to the structural features and meshing characteristics of double helical gears,an improved time-varying mesh stiffness(TVMS)meshing model of helical gears taking into account considering tooth surface friction and axial deformation is proposed,and the TVMS of the gear pairs is calculated by proposed method.Considering the internal dynamic nonlinear excitation of the transmission system,such as TVMS,tooth surface friction and comprehensive error and gear backlash,the bending-torsion-axis dynamic coupling model of double helical planetary gear transmission in multi-split condition is established.(2)Based on the bending-torsion-axis dynamic coupling model of double helical planetary gear transmission system,the dynamic differential equation of free vibration for the transmission system is established,and the system natural frequencies and vibration modes of the system are calculated by subspace iteration method,then the characteristics of the vibration mode are summarized.Combined with frequency response curves of the transmission system,the effects of support stiffness,mesh stiffness and left and right coupling stiffness of the transmission system on natural frequencies are investigated.(3)On the basis of the bending-torsional-axis coupling dynamics model about double helical planetary gear transmission system,considering numerical expressions of the internal dynamic excitation,the dynamic model is programmed,and numerical integration method is used to solve the vibration response of the transmission system,including the vibration displacement,vibration velocity,vibration acceleration and dynamic meshing force of each gear component.Finally,the relationship between meshing stiffness,comprehensive error,tooth surface friction,operating conditions and load sharing characteristics is studied.(4)Considering TVMS and comprehensive error nonlinearities,a dynamic performance optimization model of the transmission system is established.By using Harmonic Balance analytical method,the acceleration expression of the gear component are obtaind.The vibration acceleration and volume of the gear transmission system are considered as the objective functions,and bending stress,contact stress and the geometric position between gears are treated as constraint functions.By optimising the main parameters of gears,such as the module,number of teeth,pressure angle and helix angle,hybrid discrete optimization algorithm of MATLAB is programmed to obtain the optimal solution,obvious optimum effect is accuired.