Determination of optimum design criteria of a cretan wind rotor

Date

1987

Abstract

Eight different Cretan models namely A,B,C,D,E,F,G and H, each with two to eight blades were tested in a tunnel. The models A,B,C and D had equal heights but 'd' were different while models E,F,G and H had the same 'c' but different heights. From among the models A,B,C, and D, model B gave the highest power coefficients, Cp=0.298 but the torque coefficient, Ct=0.39 and tip speed ratio is 0.76 with 6 blades while model 'D' contributed a highest tip speed ratio of X = 0.88 but Cp = 0.26 and Ct = 0.29 with eight blades. From the other group E,F,G and H, model F contributed the highest Cp=0.29 and Ct=0.44 at a tip speed ratio of 0.66. It was also found that although the models B and F belongs to different groups their Cp and Ct contribution were almost the same except their sip speed ratios of 0.76 and 0.66, respectively, due to their geometrical similarity by variation in shape. It concluded that for high torque coefficient the point 'd' should be nearer or around the center of the arm having a height lower than half of the arm. When the point 'd' moved away from the center of the rotor but with the same height of the blades Cp was increased but not Ct. This means that the farthest point (but not at the tip) could give better Cp than closest to the center of the rotor. However, the Cretan wind rotor cannot be generalized in terms of Cp and Ct. Its performance would vary according to its shape, material and location of cord. Certain mills should be designed either for generation of electricity or production of high torque depending on the purpose of use. However, the Cretan wind rotor generally should not be used for generation of electricity because of its low tip speed ratio. The power contributed by the root is less than that by the outer portion of the blade. Generally, it lies between 50% and 90% of the arm of the rotor.

Document Type

Master Thesis

Language

English

LC Subject

Windmills

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 995 1987 A2 C56

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