Torque and drag characteristics of a three bladed savonius rotor

Abstract

Drag and torque coefficients of a stationary thrcc bladcd Savonius rotor havc bccn invcstigatcd by mcasuring thc prcssurc distribution on thc bladc surfaccs fiJI' various rotor angle. The experiments have been carried out at a Reynolds number of2x I05 in a uniform flow jet produced by an open circuit wind tunnel. To calculate drag force and torque in non-dimensional form, Microsoft Fortran programmes have been developed. Thc data inputs were pressure on 17 tapping points on each blades of the three bladcd Savonius rotor for every 10" interval of the angle of rotation and different fluid properties. Thc outputs of these programmes were subsequently plotted and analyscd. The cffects of individual blade and also the combined effects of three blades on different aerodynamic characteristics are analysed in the present research work. The total static torque coefficient incrcases with the rolor angle and reachcs its maximum value at the rotor angle a=60" and then decreases to a negative valuc at a=! 00" and becomes zero at 110°. The curve repeats from 120" to 230" and n.om 240° to 3500 angle of rotation. A quasi-steady approach has been applied for the prcdiction of the dynamic performance of the rotor using the static drag and torque coefficients. This method results in a reasonable agreement with the measured power coefficient.