| Compared with the traditional parallel gear transmission,the herringbone star gear transmission system has many advantages,such as its small volume,light weight,heavy carrying capacity,and so no.Hence,it is extensively used in automobile,ship,aviation,aerospace and other related field.However,because of the inevitable manufacturing,assembling errors and elastic deformation in the actual engineering application,the load cannot be evenly distributed to the various power splits of the star gear transmission system,which reduces carrying the capacity of the system,causing overload,vibration,noise,and other issues.In order to meet the development requirements of high speed and overloading,it is necessary,therefore,to use flexible supporting component in the star gear transmission system.But few scholars have conducted related research on the techonology in the herringbone star gear transmission system,which makes it difficult to further develope complex star gear transmission system.In this thesis,the natural vibration characteristic,dynamic response,and load sharing performance of the herringbone star gear transmission system for geared turbofan(GTF)engine were thorough analyzed based on system dynamics model,considering all kinds of dynamic incentivend and introducing flexible pin.The research will provide a theoretical basis for determining the load sharing coefficient,controlling errors,and structural design of the flexible pin.The specific research contents are as follows:1)Based on the generalized finite element method,the herringbone star gear transmission system can be equivalent to the coupling shafting elements using the space beam element theory.After analysizing and deducing the coupling relationship between the all shafting segment elements,the dynamic model of the herringbone star gear transmission system with a flexible pin is established,considering the influence of the meshing error,time-varying meshing stiffness,and flexibility of the shaft segments,which will lay the foundation for the research of the natural vibration characteristic,dynamic response,and load sharing performance.2)The calculation formula of the time-varying meshing stiffness and equivalent meshing error was deduced based on the overall dynamic model of the herringbone star gear transmission system.The natural frequency of the system under supporting of different pins was solved according to the calculation principle of the natural characteristics;the main modes corresponding to each order frequency are summarized;the distribution law of various types of modal energy was analyzed;and the influence of the system parameters on the modes was studied.3)Based on the established dynamics model and dynamic excitation parameters of the GTF star gear transmission system,the nonlinear dynamics differential equation was solved using the numerical analysis method;the time domain response of the gear nodes was obtained in the steady working condition(the input speed is 9000 r/min,the input power is 120 kW),including the vibration displacement,vibration velocity and vibration acceleration of all gear nodes in each degree of freedom.The dynamic meshing force was obtained based on the dynamic response,and the influence of the working condition parameters,stiffness,and the structure of the pin on the dynamic meshing force was studied,which will provide important reference index for reducing noise and vibration of the transmission system.4)Starting from the dynamic meshing force,the calculation method of the dynamic load sharing coefficient was defined;the dynamic load sharing coefficient of the GTF star gear transmission system was obtained in the steady working condition;and the influence of the working condition parameters,errors,and the structure of the pin on the load sharing coefficient was studied.Besides these,the optimization mathematical model for the structure of the flexible pins was established based on the dynamic load sharing performance;the structure dimention of the F&J flexible pin was optimized aiming at minimize the bending stress of the pin and the load sharing coefficient of the system,which will provide the theory basis for the structure design and optimization of the flexible pins in the star gear transmission system. |
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