Load Sharing Analysis And Optimization Of Large Wind Turbine Gearbox With Floating Components

Offshore wind turbine gearboxes operating in complex environments can easily lead to uneven load distribution between multi-stage planetary gear systems,which will generate large vibrations and noise,seriously affecting the safe and reliable operation of the unit.The 9MW offshore wind turbine with two-stage planetary and one-stage parallel shaft gearbox established the multibody dynamic model by the lumped parameter method.The support stiffness of floating gears is analysed and optimised and the interaction between gear wear and uniform load characteristics is revealed.This research was completed under the funding of National Key R&D Program of China"Optimal Design and Batch Manufacturing Process and Inspection Technology of Key Components of Large Offshore Wind Turbine Drive Chain(No.:2018Y FB1501304)".The main research work and results are as follows:(1)The dynamic differential equations for the bending-torsional-axial coupling of multi-stage gearing transmission system are established and a virtual prototype model of the gearbox is built based on SIMPACK software.The effect of the support stiffness of floating center wheels on the load sharing characteristic and vibration characteristic of the planetary wheel system are analysed in the time domain,and the effect of different floating modes on the inherent frequency of the planetary gear train is investigated from the modal perspective.The simulation results show that:The load distribution performance of the transmission system decreases with increasing support stiffness.Floating gears mainly affect the higher-order inherent frequency of the system and have the lowest inherent frequency when the gears are floating together.(2)Taking a wind turbine two-stage planetary one-stage parallel gearbox as the research object,a 49-group orthogonal design scheme with each floating centre wheel as the independent variable factor and support stiffness values of 1×109 N/m,2.5×109 N/m,4×109 N/m,5.5×109 N/m,7×109 N/m,8.5×109 N/m and 1×1010 N/m as discrete levels is established to optimize the support stiffness of the floating sun gears and the floating internal gears of the two-stage planetary gears.The influence law of each floating gear on the transmission shaft is studied by using the extremum difference analysis.The simulation results show that:High speed shaft vibration is mainly influenced by the second stage sun wheel support stiffness.The optimised solution reduces the overall vibration index of the gearbox by 8.9%compared to considering only the equal load performance of the system.(3)Taking the planetary gear system of the first stage as the research object,a parametric model of localized uniform wear of the tooth surface of the floating sun wheel is established,and the dynamics of the gear system under different degrees of wear is analyzed.The simulation results show that:Uniform tooth wear will reduce the system’s load sharing characteristic,but floating elements will mitigate the adverse effects of wear failures and improve the system’s load sharing characteristic.