Research On Nonlinear Dynamics Of Wind Turbine Gear System Under Fault Condition

As a green and clean power generation method,wind power generation has broad development prospects.The wind turbine speed increasing gearbox usually works in heavy load,high temperature,severe cold,dusty and other harsh conditions,which is prone to failure.This will affect the power generation efficiency of wind turbine.Therefore,the dynamic research of wind turbine gear system,especially the dynamic modeling and analysis of the gear system with faults,is helpful for people to deeply understand the faults mechanism and the impact of fault evolution.It is of great significance for the design,safe operation and fault detection of the speed increasing gearbox in wind turbine.The main contents are as follows:(1)Taking the gearbox of wind turbine as the research object,considering sun gear support,backlash,etc,the lateral-torsional nonlinear dynamic model of wind turbine gear system is established.The time-varying mesh stiffness model is established based on potential energy method.Furthermore,establishing the gear teeth root crack fault model to analyze the influence of crack propagation path and evolution on mesh stiffness.(2)Using bifurcation diagram,time series,Poincaré map,spectrum diagram and related three-dimensional diagrams,etc,as tools,the dynamic response of the wind turbine gear system under variable working conditions is researched,and the influence of sun gear root crack fault and its evolution on the system dynamic behavior is analyzed.It is found that the occurrence of crack failure has a significant influence on the dynamic behavior of the system,such as bifurcation and chaos,and the crack failure characteristics appear in the time-frequency analysis.With the evolution of crack failure,the periodic motion behavior and the recognizability of fault characteristic frequency change accordingly.The reliability of the nonlinear dynamic model is verified by the wind turbine gearbox experiment.(3)The calculation method of gear mesh stiffness is improved considering the influence of gear teeth root,and the mesh stiffness model with spalling fault is established.It is found that spalling fault weakens the mesh stiffness of gears.Incorporating the time-varying and nonlinear characteristics of tooth friction into considering,the tooth surface friction factor is introduced to further improve the nonlinear dynamic model of the gear system.Combined with bifurcation diagram,time series and phase trajectory diagram,etc,the dynamic response of system under variable excitation is analyzed,and the influence of spalling fault on the system dynamic behavior is revealed.The results show that,due to the influence of spalling fault,the single period motion in the system gradually develops into multi period motion at low excitation frequency,and the original period motion becomes quasi-period or chaotic motion when the excitation frequency is high.In addition,spalling fault plays a certain role in dissipating the energy of chaotic motion of the system,and the fault characteristic frequency is sensitive at low excitation frequency.By studying the dynamic response of the system with different spalling length,it is found that the expansion of spalling fault makes the dynamic behavior of the system more complex.