Experimental study on small scale horizontal axis wind turbine of analytically-optimized blade with linearized chord twist angle profile

Abstract

Blade linearization is used to simplify the blade design and reduce the blade manufacturing cost of Small-Scale Horizontal Axis Wind Turbine (SSHAWT). Compared to analytical studies, experimental investigations on the blade linearization of SSHAWT are rare. The present work aims to introduce a simple and efficient design of SSHAWT, and verify its performance experimentally. Two designs of rotor models are proposed and their performance is analyzed. The first one is a classical rotor with non-linear chord and twist distributions and the second one is a new linearized rotor design. Analytical optimizations of the linearized blades are employed through three tuning steps using Blade Element Momentum (BEM) theory. The highest coefficient of correlation with the classical rotor among the linearized rotor is found to be 0.969. The two rotor models, selected based on the optimization results are then fabricated, tested, and compared. The comparison made between the two designs is verified experimentally, at different wind speeds of 5, 6, 8, and 10 m/s. Further, measurements are performed at blade pitching of −3, 0, and 3°. It was found that, the proposed new linear design of the rotor blades has efficient performance, with maximum power coefficient Cpmax=0.426 at tip-speed ratio 5.1 and wind speed 10 m/s. The performance in terms of power coefficient approaches that achieved by non-linear blades. Moreover, there is significant reduction in the blade size volume of the new design by 26% which consequently reduces the blade weight. The results obtained in the present work show higher starting ability and extended operating range of the linearized model at lower wind speed compared with the classical model.