| In recent years,wind power is developing rapidly in China as a clean renewable new energy.Improving the operational reliability of wind turbine units and enhancing the maintenance management quality in wind farm can significantly increase the efficiency of power generation.As an important part of the transmission system,the gearbox is prone to fatigue damage under such long-term random alternating load.Randomness of the external wind load and interaction of the structures make fatigue damage assessment and life prediction more difficult.This paper mainly analyzes the gear fatigue under different wind speeds and load types.The main research contents include: firstly,the wind speed model and impeller torque calculation model are established by the unit operation principle to calculate the external excitation.The gear bending stress load spectrum under different wind conditions is compiled through the gearbox dynamics model,considering time-varying meshing stiffness and damping.Rain flow counting method is used to calculate the stress cycle.The gear fatigue damage under short-term wind conditions are eventually evaluated based on the linear fatigue cumulative damage theory.Secondly,in order to study the effect of multi-frequency loads on fatigue life,a hybrid uniaxial stress fatigue method based on time-frequency analysis is proposed.The characteristic parameters of the ground state loads are obtained by Hilbert transform,and the comprehensive fatigue life under the joint action is further calculated.Then,the remaining cycles of crack growth on gear root are analyzed under constant wind and random turbulent wind.Finally,based on SCADA data,the cumulative variation of fatigue damage before gear fracture failure is given.At the same time,crack propagation life is calculated by wind speed record before wind turbine is shut down for maintenance,and the fatigue life of the crack formation to the extended failure was comprehensively evaluated.The whole fatigue life from crack formation to fracture failure is comprehensively evaluated.The results of this paper prove that fatigue life of the gearbox is intrinsically linked to the external wind load.The average wind speed and turbulence changes make different degrees of fatigue damage.Hybrid uniaxial stress fatigue method based on time-frequency analysis is proposed for calculating the comprehensive remain life of gears,promoting the evaluation of gear fatigue damage under multi-frequency alternating loads.In addition,the residual life of gears under different wind conditions according to the crack propagation speed is analyzed.SCADA data is used to study the damage accumulation law and calculate the remaining life after the crack is formed.A method to evaluate the whole fatigue life for gear fracture failure duration is proposed,which can provide more comprehensive reference for online monitoring and fatigue life prediction of wind turbine gearbox. |
PDF Full Text Request