Design Process for Scaled Model Wind Turbines Using Field Measurements

Abstract

This paper presents a method for designing wind turbine-scaled models based on field data. The scaling process requires careful consideration of the system's physical laws and similarity criteria. Scaling methods depend on the prototype's operating conditions (full-size wind turbine) and the experimental conditions (scaled model dimensions and wind tunnel capabilities). The data from a field turbine are the input for creating a scaled model and testing it in a wind tunnel. There are few field data available. The task is not straightforward since most operating conditions must be satisfied, and the similarity criteria could result in different scaled models and wind tunnel conditions. The drawback of the scaling models is their inability to reproduce all the operating conditions. The method presented here considers most of the recommended similarities, including the dynamic modeling of the system and two additional similarities, one related to the blade's natural frequencies and the other to the rotor's moment of inertia. The additional similarities allow the designers to define the blade's mass and stiffness. The final scaled-model design was obtained by modifying the blade profile to reproduce similar power, pitch momentum, and trust coefficients, keeping the same twist angle as the prototype. Since the possible profiles are too large, the best approximation was obtained by comparing the coefficient curves of different blade profiles with the prototype's curves. The curves were calculated using the blade element momentum (BEM) method. It was found that the scaled model has an entirely different design.