Performance measurement of a twisted three-bladed airfoil-shaped H-rotor

Abstract

In the present study, performance of a twisted three-bladed airfoilshaped H-rotor was measured experimentally for different values of chord Reynolds number of flow and ratios of height-to-diameter (H/D). The rotor was 20 cm in height (H) and 5 cm in chord with about 26° twist at the trailing end. Tests were conducted in an open circuit subsonic wind tunnel for ten H/D ratios, namely 0.85, 1.0, 1.10, 1.33, 1.54, 1.72, 1.80, 1.92, 2.1 and 2.2. The wind tunnel blockage effect was also taken into consideration. The power coefficients (Cp) and torque coefficients (Ct) were evaluated for the selected values of H/D. It was observed that at any H/D, both Cp and Ct increased with the increase of tip speed ratio up to a certain limit, but then decreased even though tip speed ratio was increased. Moreover, there were optimum values of H/D at which both Cp and Ct were the highest. Further, lift and drag coefficients of the rotor were evaluated by using Prandtl lifting line concept and by computational fluid dynamics (CFD) approach. Moreover, the power loss due to the parasitic drag of the support arms was also calculated.