Research On Dynamic Behavior Of Load-split Speed-growth Planetary Gear Train

The importance of wind power generation technology is widely recognized with increasing deterioration of the ecological environment and energy shortage. Planetary gear train is widely used in wind turbine owing to their advantages such as little space required, large ratio of transmission and high efficiency. Wind power planetary gear is used in the growth of the transmission and has high failure rate, which is under a complex load. The technology of planetary gear train is improved, but the gap between domestic wind power planetary gear transmission system and those of the other countries is still large. It is necessary to research on the dynamic characteristics of planetary gear train to reduce the failure rate of wind power growth gearbox and enhance its life and reliability. A load-split spee-growth planetary gear train is proposed and the danamic characteristics of the transmission system is analyzed by adopting the method of theoretical analysis, finite element method and experimental method. The contents of the study are as follows:A load-split two-stage planetary gear train for wind turbine gearbox was studied, which was composed of simple planetary gear train and the differential planetary gear train. The kinematics of the transmission mechanism was analyzed. The carrier and the sun gear of the first-stage planetary gear train were provided to link up the ring gear and the carrier of the second-stage planetary gear train separately to form the transmission mechanism, which was used to withstand simultaneously the torque of blade. The kinematics equation of each component and transmission ratio equation were deduced based on the mechanism inversion method. The influence of characteristic parameter on rotational speed of the planetary gear train was analyzed. It was shown that the transmission ratio and the rotational speed of sun gear were increased and the rotational speed of planetary gear was decreased by increasing characteristic parameter of planetary gear train.The contact process of the first planetary gear pairs was studied according to the transient dynamic finite element method. The solid model of multi-stage transmission system made up of the two-stage planetary gear train and one-stage parallel-shaft gear train was built by using the parameterization function of Proe software. The finite element model of the first-stage planetary gear pairs was built. In order to ensure the convergence of contact analysis, the entire simulation process was divided into multiple analysis steps. Boundary conditions and load were analyzed. The result was checked. The equivalent stress law of contact and non contact surfaces of planetary gear pairs was studied.The influence of temperature difference on the first-stage planetary gear train was studied. The finite element model of gear was established and divided into two districts. The temperature of each district was set using temperature field pre-defined function in Abaqus to introduce the temperature difference, which could be used to simulate the temperature difference. The relationship between temperature difference and equivalent stress of addendum, pitch circle and dedendum of the gear was analyzed. The influence of temperature difference on equivalent stress of addendum, pitch circle and dedendum of internal and external meshing planetary gear tooth profile was analyzed.The dynamic model of load-split speed-growth planetary gear train was presented using lumped-parameter method and dynamic differential equations were established. The natural frequencies and vibration modes of the system were obtained through solution of the associated eigenvalue problem by using the related parameters. Based on the properties of the transmission system, the vibration modes of the system were classified into eight categories and the characteristics of vibration modes were analyzed.The influence of the coupling stiffness between the first stage and the second stage on the natural characteristics was studied. It was shown that the natural frequencies of coupling vibration mode could be changed by controlling the coupling stiffness. The frequencies increased with the increase of the coupling stiffness. The coupling stiffness didn’t affect the type of vibration modes. The natural frequencies of coupling vibration mode could be controlled by changing the coupling stiffness between the first-stage carrier and the second-stage ring gear or between the first-stage sun gear and the second-stage carrier. The analysis was helpful in reducing the system vibration scope and avoiding resonating. Load sharing characteristic of the system was researched. The dynamic equations of the load-split speed-growth gear train were solved by using numerical integration method. The dynamic responses of the system were obtained and the uniform loading coefficient expressions of the system were deduced.The experimental platform of planetary gear train was established, which could detect the rotation speed, torque and power of the planetary gear train. An experimental mode technique was applied to study the dynamic characteristics of planetary gear train. The results indicated that meshing frequencies and the low order natural frequencies of planetary gear train had an obvious difference. The planetary gear meshing resonance phenomenon could not occur. The frequency characteristics of the dynamic response of the planetary gear train was analyzed by using the method of theoretical analysis and experimental verification. It was shown that frequency of the planetary gear train were abundant, which was relevant for the meshing frequencies, the characteristic frequencies and rotating frequency of the planetary gear train.The author gratefully acknowledges the support of the Chinese National Science Foundation (No.51175299), the Shandong Provincial Natural Science Foundation, China (No.ZR2010EM012) and the Graduate Independent Innovation Foundation of Shandong University (No. yzc10117).