Stochastic Vibration Analysis Of Gear Transmission System Of Wind Turbine And Probabilistic Optimization Design Based On Dynamic Reliability

As wind turbine working condition is bad, and withstand the variable wind loads orstrong gusts, coupled with installed overhead and difficult to maintain requests higherreliability and longer service life than the general mechanical system. Gear transmissionsystem need to withstand the highly fluctuating load and much higher cyclic fatiguethan other transmission mechanism as the key components of drive system of windturbine, and it is one of the highest failure rate components of wind turbine. Therefor,the study of dynamic behavior and reliability of gear transmission system of windturbine has an important practical significance to improve the stable and reliableoperation of the wind turbine.According to the research task of the National Natural Science Foundation ofChina (50975294)“Reliability research of wind turbine transmission besed on theflexible multi-body dynamics”, and considering the practical operating condition ofwind turbine, the dynamics and the reliability problems are investigated fairlycomprehensively and deeply in this dissertation. The main researches are as following:①Inherent characteristic analysis of gear transmission system of wind turbine.According to gear mesh theory and Lagrange equation, the torsional dynamicmodel for gear transmission system of1.5MW wind turbine is developed bylumped-parameter method. The expression of the statistical characteristics of the systemeigenvalues is derived based on the stochastic perturbation theory. The statisticalcharacteristics of system eigenvalues are researched taking the elastic modulus, massdensity, tooth width and pitch diameter as random variables, and the influence of theseparameters on the system natural frequency are also studied.②Random vibration analysis of gear transmission system of wind turbineA dynamic model of planetary gear transmission system of wind turbine wasdeveloped with considering the time-varying mesh stiffness, transmission error anddamp. Random wind velocity is obtained based on the Stochastic Volatility (SV) model,and the external excitation of the gear transmission system is got according toaerodynamic theory on the basis of the dynamic model of the system. Thecharacteristics of internal excitation of the multi-stage gear transmission system areanalysed, and a solving algorithm for system response of wind turbine gear transmissionsystem when the external loads and design parameters are random variable. The statistical characteristics of the vibration displacement and dynamic dynamic meshingforce are obtained by numuerical simulation, and the influence of these parameters onsystem dynamics are also be analysed.③The influence of randomness of loadings and parameters on dynamic reliabilityof gear transmission system.According to rain flow counting principle, the dynamic meshing forces have beenconverted into a series of amplitude fatigue load spectrum blocks. Then, the equivalentamplitude and frequency will be get using equivalent method of Geber quadratic curve.Finally, the dynamic reliability model of components and system have been set upaccording the theory of probability fatigue damage cumulative. The change laws withtime of system reliability with the random variation of parameters has been calculated,and the influence of random parameters on dynamic reliability of components havebeen studied and compared with the results of Monte Carlo method.④Probability optimization design of wind turbine gear transmission system basedon dynamic reliabilityA probability optimal mathematic model of wind turbine gear transmission systemis built with goals of the maximum of the mean vibration displacement of systemcomponents and minimum volume, design variables of parameters which have aninfluence on system dynamics and reliability, comstrains of the reliability of geartransmission system, and the influence of random parameters on system reliability andthe normal meshing conditions and strength of gears. A solving algorithm for systemprobability optimal model is presented based on the system dynamic reliability analysisand probability optimal mathematic model. Then, an optimized example of geartransmission system of wind turbine is given. The optimization results is compared todesign results and the Monte Carlo optimization results to verify the feasibility of theoptimization method.⑤Random vibration test of wind turbine gearboxThe wind turbine gearbox used testing is designed and manufactured based on thesimilitude theory，and the test fig is set up for dynamic characteristics testing of windturbine gearbox. According to the working characteristics of wind turine geartransmission system, the dynamic responses of each point have been measured under avariety of random load conditions, and the statistical characteristics of the randomvibration of wind turine gear transmission system have been obtained through statistical analysis and numerical integration. The comparison analysis between theory calculationand test results shows that the theory model is correct and effective.