100-KW Hingeless Metal Wind Turbine Blade Design, Analysis And Fabrication

The design, fabrication and analysis of aluminum wind turbine rotor blades is discussed. The blades are designed to meet criteria established for a 100-kilowatt wind turbine generator operating between 8 and 60-mile-per-hour speeds at 40 revolutions per minute. The design wind speed is 18 miles per hour. Two rotor blades are used on a new facility which includes a hingeless hub and its shaft, gearbox, generator and tower. Experience shows that, for stopped rotors, safe wind speeds are strongly dependent on blade torsional and bending rigidities which the basic D spar structural blade design provides. The 0.25-inch-thick nose skin is brake/bump formed to provide the basic “D” spar structure for the tapered, twisted blades. This technique was developed to form the thick spar skins to avoid high tooling costs associated with stretch forming methods. Wind turbine blade design must provide good separation from nP higher harmonic aerodynamic forces as well as the 1P gravity field. The symmetric elastic characteristics of the drive shaft, bedplate and tower structure are coupled to the rotor system. Adequate margins for flutter and divergence are predicted from the use of existing, correlated stopped rotor and helicopter rotor analysis programs. Adequate structural margins are indicated for the prescribed loading conditions.