Design, fabrication and testing of a savonius type windmill with a deflector augmentor

Abstract

The study was conducted with the objectives of developing and testing a savonius wind mill and analysing the effect of a deflector augmentor on the performance characteristics of the rotor. The wind mill was consisted of two rotors of 2 m x 3 m size fixed one below the other at 90 degree out of phase. A 100 mm galvanised iron pipe of 12 m length acts as the shaft. The shaft passes through two ‘30220’ taper roller bearings. Lower bearing was fixed on a I m x I m x I m foundation and the upper bearing was positioned by four 4 mm guy wires. The guy wires were equidistant and forms an angle of 45 degree with the shaft. This wind mill was tested under field conditions. Power developed by the wind mill was calculated by measuring the torque and rotor speed, and power delivered to the rotor was calculated by taking corresponding wind velocity. The coefficient of power and coefficient torque were calculated for different tip speed ratios. The wind mill was found to attain a maximum coefficient of power 0.155 at a tip speed ratio 1.0. Maximum torque coefficient attained was 0.185 at a tip speed ratio 0.75 Optimum tip speed ratio of the wind mill was found to be in a range of 0.5 to 0.9. A deflector augmentor of 6.93 m2 effective wind facing area was fixed at an angle of 60 degree with the wind direction. Wind mill was again tested with the deflector augmentor. Power coefficient was found to attain a maximum value of 0.32 at a tip speed ratio 1.54. The maximum torque coefficient was 0.385 at a tip speed ratio of 0.56. Optimum tip speed ratio of the wind mill with the deflector augmentor was found to be in a range of 0.5 to 1.5. When the deflector augmentor was attached to the wind mill, power coefficient was increased by 106.5 percent and torque coefficient was increased by 108 percent. The wind mill was found to work in higher tip speed ratios. The cut in velocity was reduced from 2.4 m/s to 1.4 m/s. Cost of operation of the wind mill was Rs.1.45 per bhp.hr which is comparable with diesel and electric power.