Aerodynamic characteristics of a five bladed S-shaped savonius rotor

Abstract

The S-shaped rotor is a modification of the Savonius rotor with no overlap. Drag and torque coefficients of a five bladed S-shaped Savonius rotor have been investigated by measuring the pressure distribution on the blade surfaces for various rotor angles. The experiments have been carried out at a Reynolds number of 2.1x105 in a uniform flow jet produced by an open circuit wind tunnel. To calculate drag force and torque in non-dimensional form, the data are taken on 12 pressure tapping points on each blade of the five bladed S-shaped Savonius rotor for every 100 interval of the angle of rotation. The pressure distributions both on the concave and convex surface of the blade at different angle of rotation are presented graphically. At rotor angle α = 400, difference of pressure coefficient on convex surface and concave surface is maximum. At rotor angle α = 3100, difference of pressure coefficient on convex surface and concave surface is minimum. The measurements indicate that drag forces and the torque, vary with rotor angle. The normal drag coefficient increases with the rotor angle, reaches its maximum value at the rotor angle α = 400, remains approximately constant value at the rotor angle α = 1400 to 2100 and minimum value at the rotor angle α = 3100. The tangential drag coefficient increases with the rotor angle, reaches its maximum value at the rotor angle α = 2900 and minimum value at the rotor angle α = 00. The torque coefficient also increases with the rotor angle, reaches its maximum value at the rotor angle α = 400, remains approximately constant value at the rotor angle α = 1400 to 2100 and reaches minimum value at the rotor angle α = 3100. The result facilitates predicting the performance of five bladed S-shaped Savonius rotor under dynamic conditions.