Impact of manufacture-induced blade shape distortion on turbine loads and energy yield

Abstract

A blade shape distortion develops during the manufacturing process. The distortion is defined as the difference between the target blade shape as per the design and the shape under operational temperatures. This initial distortion varies under operational temperatures due to the different thermal coefficients of expansion of the various blade materials. The resulting manufacture-induced distortion and operational temperatures affect the twist angle, the cross-sectional shape, and the sweep of the blade. Young's modulus of the blade's raw materials, i.e., the matrix of the fiber-reinforced polymers and the adhesive material, changes during the manufacturing process, complicating the determination of the distortion. This work calculates the shape distortion for a reference temperature on the basis of a thermal stress analysis using a full 3D finite element blade model. It performs an aero-elastic load simulation for two models: one with the target blade shape and one with the distorted shape. The simulation reveals that the turbine with the distorted shape has an energy yield which is 0.5% lower and a lifetime extension of additional 4. 4 years.