Analysis Of Gear Fatigue In Wind Turbine Gearbox Under Turbulent Wind

As a representative of new energy power generation technologies, wind power generation is increasingly developing in the world. Gearbox is a critical mechanical component of wind turbine that is working under stochastic and alternating load condition, which is essentially the cause of gear fatigue damage. Randomness and unpredictability of wind turbine actual load makes gear fatigue damage calculations and life prediction difficulty. This paper studied the fatigue damage of 1.67MW wind turbine gearbox under turbulent wind speed.The main research contents include:firstly, the external load excitation of wind turbine gear transmission system model is studied based on the turbulent wind model and aerodynamic theory. Secondly, a simplified gear load transmission system model and a purely torsional gear transmission system model are established. Gear root bending stress time series under different mean wind speeds and turbulence intensities are obtained. Rain flow counting method is used to statistically calculate stress cycles. Miner linear fatigue cumulative damage theory is used to estimate the 10min short-term gear fatigue damage. Then, a frequency-domain method is adopted to estimate the lOmin short-term fatigue of gear in purely torsional gear transmission system. Time-domain fatigue damage analysis in terms of simplified gear load model, time-domain fatigue damage analysis in terms of gear in purely torsional dynamic model and frequency-domain fatigue damage analysis in terms of gear in purely torsional dynamic model are compared. The effects of wind speed and turbulence intensity to gear fatigue damage are discussed. The results show that a proper flexible gear transmission system design could assist to buffer external torque excitation due to turbulent wind and to reduce the excitation fluctuation impacts to gears. Finally, a new method of using wind turbine SCADA data to estimate gear fatigue damage by reconstructing 10 min average wind speeds profile is proposed. Fatigue analysis methods are tested to calculate planetary gear damage of an operating wind turbine before teeth broken. The results show that this approach can effectively estimate the gear fatigue damage of wind turbine in service using time-domain fatigue damage calculating method for gear transmission system.The results of this paper analyze excitation and dynamic behavior of wind turbine gearbox system which provides useful information for wind turbine gearbox design optimization. A new method of using SCADA data to predict gear fatigue damage is proposed and it is proved to be applicable for online wind turbine gear fatigue life monitoring.