Study On The Key Design Technology Of Gearboxes For Large-scale Wind Turbines

In recent years, wind power industry has been rapidly developing along with thewind power generation drawing more and more attention. At present, horizontal axiswind turbine has the dominant position in wind turbine generator system (WTGS).The key design and manufacturing technology of gearboxes have become animportant factor for restricting the development of wind power. With the windturbine's capacity increasing, more and more complications must be considered inlarge-scale wind turbine's design and manufacturing. The gearbox is damaged tooearlier for WTGS in life expectancy. The main cause is that the bearing lifetime can'tbe estimated accurately when the load is very complicated. On the other hand, despitethere are many calculating methods, bearing lifetime can not be estimated well andtruly. In addition, the calculating method of load capacity of gears and the method ofdealing with complicated load need to be improved, so it's very important to researchthe gearbox of large-scale wind turbines systematically. This dissertation focuses onthe key technology of gearboxes for large-scale wind turbines, according to the statesof wind power industry in China, studies on the methods of dealing with variableloads, calculation methods of bearing lifetime and gear strength, achieves geometricoptimization of gearbox for wind turbines with single planetary gearing and two stagefixed-axis drive train. The main contents of this dissertation are summarized asfollows:1) The load cases of gearbox for wind turbines are analyzed, and the interrelationof loading cycle numbers under different torque levels is deduced according to the curve of materials' fatigue. The equivalent torque and an application factor of givenload spectrum are obtained for wind turbine by Miner's rule.2) The calculation methods of modern beating lifetime are researched. And somekey influencing factors for bearing lifetime are pointed out by comparing the methodsof ISO, FAG, SKF, etc. The influences of these factors for bearing lifetime areanalyzed and computed in detail, some theoretical directions are provided toengineering application.3) The calculation methods of gear strength are researched by.comparing ISO6336 with American national standard AGMA 2101. The calculation models andformulas of the two methods are analyzed; the similarities and differences ofinfluence coefficients in calculation formulas are discussed. The conclusion isobtained that there is not any constant factor for converting between the two methods.4) Based on the theoretical analysis, the computer programs of load processing,bearing lifetime calculating, and gear strength calculating of the gearbox for windturbines are developed.5) According to the characteristics of gearboxes for large-scale wind turbines, thestructure of gearbox with single planetary gearing and two stage fixed-axis drive trainis analyzed, and the mathematical model of the gearbox is established. The optimumprogram is compiled and the objective function reaching equilibrium with the contactstrength of every stage is achieved.