| Geared Turbofan Engine（GTF）has always been a hot spot in aero-engine research.As the core component of the gear-driven turbofan engine,the herringbone star gear trains not only have complex structure,but also require high efficiency.Under actual working conditions,the efficiency of the star gear trains would be decreased which caused by various unavoidable manufacturing and installation errors and harsh working environment.Thus,it is significant to study the efficiency of the herringbone star gear trains and optimize it for improvement.In this paper,taking a herringbone star gear train in GTF as the research object,the meshing efficiency of the herringbone gear pair is analyzed firstly,and the efficiency is optimized by tooth profile modification.Then the influence of load distribution on the power flow to study the efficiency of the star gear train was considered,and the efficiency was optimized by improving the load sharing performance.The details are as follows:（1）According to the transmission principle of herringbone star gear trains and the factors affecting its efficiency,the efficiency solution method of the gear train is determined.The static model of the herringbone star gear train is established as the theoretical basis for the study of the load sharing performance of the gear train.Meanwhile,the bending-torsional dynamics model is established by the concentrated mass method,which considering the nonlinear error excitation such as the comprehensive gear meshing errors,tooth surface friction.And the dynamics differential equations are solved by the Runge-Kutta method for the subsequent study of gear meshing efficiency.（2）Based on the elastic flow lubrication theory,a gear meshing friction loss model is established to solve the friction force of the gear pair and the herringbone gear pair meshing power loss formula is derived.Then the herringbone gear is reshaped by ROMAX software based on genetic algorithm.The gear tooth load distribution is improved and the power loss is reduced,so as to improve the meshing efficiency of the herringbone gear.（3）The load distribution of the gear train is studied based on the power flow of the herringbone star gear trains.According to the static model of the gear train,the manufacturing errors and misalignment affecting the load sharing performance are analyzed,and the equivalent displacement of the errors on the meshing line is calculated.Based on the herringbone star gear trains load sharing mechanism,the equation of load sharing coefficient of the gear train is given,and the load distribution condition of the star gear is considered when the stagge angle exists.Then the load sharing performance of the star gear train is analyzed to prepare for the study of the effect of load distribution on the efficiency of the star gear train.（4）The influence of load distribution on the meshing efficiency of the gear train is analyzed,and the calculation method of the the herringbone star gear train efficiency is given by considering the bearing power loss and wind resistance loss comprehensively.By adjusting the stagger angle to improve the fluctuation of the meshing force and selecting a suitable stagger angle under the consideration of vibration,the load sharing performance of the gear train is improved,and the optimization of the gear train transmission efficiency and comprehensive transmission performance is realized. |
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