Research On The Dynamics Of A Coupled High-power Wind Turbine Gearbox System

The research subject of the dissertation stems from the projects “The study of Key technologies of industrialization for 7MW wind turbine gearbox and spindle bearing”(2012BAA01B05) in the National Science and Technology Pillar Program during the 12 th Five-Year Plan period of China.The high-power speed up wind turbine gearbox is one of the key mechanical units in the wind turbine, allocated between the main shaft and generator. The security, reliability and stability for high-power wind turbine gearbox is gradually becoming to the focus of the wind power industry. It is significant to study the dynamic characteristics for coupled high-power wind turbine gearbox system and improve the stability and reliability of high-power wind turbine gear box.Based on a certain 5MW wind turbine gearbox, a dynamic model of coupled high-power wind turbine gearbox system is established considering load spectrum of wind turbine, manufacture and assembly errors of transmission parts and time-varying mesh stiffnesses and dampings of gear pairs. The system dynamics are analyzed and experimental investigated. The main contents and conclusions of dissertation are as following:(1) The dynamic model of transmission sub-structure is built considering load spectrum of random wind, manufacture and assembly errors of transmission parts, time-varying stiffnesses and dampings of gear pairs, stiffnesses and dampings of transmission shafts. The bending-torsional-pendular dynamic model of box sub-structure is built based on structure discretization of uniform bending Timoshenko to box. A dynamic model of coupled high-power wind turbine gearbox system is established based on deformation compatibility conditions of connection sites between the transmission sub-structure and box sub-structure.(2) The natural characteristics of high-power wind turbine gearbox system are analyzed,and the natural frequencies and vibration modes of system are acquired. The results show that modal shape of high-power wind turbine gearbox is composed of three vibration modes – planetary system mode, parallel shaft mode and global coupled mode. And, the planetary system mode is composed of rotational-axial mode, rotational-translational mode and planet gear mode. The 1st natural frequency of transmission sub-structure is 18.7Hz and the vibration shape is global coupled mode. The vibration shapes of the first 6 order natural frequencies are the rotation around coordinate axes. The 1st natural frequency of wind turbine gearbox is 23.1 Hz, and the vibration shape is the rotation around x axis. The modal strain characteristics of system under natural frequencies are researched. The modal strain energies of system converged on the meshing of gear pairs and support of bearings.(3) The dynamic responses of coupled high-power wind turbine gearbox system are analyzed, and the influences of manufacture and assembly errors for transmission parts on load sharing characteristics of system are discussed. The results show that the maximum vibration amplitude is shaft direction of the 3rd stage pinion, and the minimum vibration amplitude is vertical direction of the 1st stage inner gear. Meanwhile, the vibration frequencies are the mesh frequencies for gear pairs of the 3rd stage transmissions and their frequency multiplication. The influence of the vertical error for the 1st stage carrier and horizontal error for the 1st stage planet gear(P1) on dynamic load sharing for planetary transmission of the 1st stage is evident.(4) The sensitivities of manufacture and assembly errors for transmission parts to dynamic responses of system are analyzed. The maximum sensitivity is shaft direction of the 3rd stage. The larger sensitivity manufacture and assembly errors of transmission parts are defined as optimization design variables. The dynamic characteristics of coupled high-power wind turbine gearbox system are optimized considering the load sharing of planetary transmission, mesh forces of gear pairs and vibration amplitudes. The optimized load sharing of the 1st stage transmission reduced 2.5%, and the mesh force reduced 5.6%. The optimized vibration amplitude for z direction of the 3rd stage pinion reduced 4.25%.(5) On the test of high-power wind turbine gearbox, the vibration, load sharing characteristics for 5MW wind turbine gearbox are investigated, and the characteristics of the system vibration and load sharing of planetary transmission are acquired. The test results are in accord with analysis results, and the theoretical analyses are validated.