Performance of a stationary vertical axis vane type rotor tested in a wind tunnel
This paper reports the performance of an equally spaced vertical axis vane type rotor tested in a wind tunnel. The aerodynamic characteristics i.e. torque coefficient, drag coefficient etc. of a stationary vane type rotor have been studied in this research work by measuring the pressure distribution on the blade surfaces at various rotor angles. The experimental investigation was performed on four bladed vertical axis vane type rotor in a uniform flow jet produced by an open circuit wind tunnel. It has been observed that the static torque varies at different rotor angles. Total static torque coefficient at different rotor angles curve repeats from 0° to 80°, 90° to 170°, 180° to 260° and 270° to 350° angle of rotation. A quasi-steady approach was applied for the prediction of dynamic performance of the rotor using the static drag and torque coefficients. This method results in a fair agreement with the measured power coefficient.
On the Performance of the Savonius Wind Turbine
An extensive wind tunnel test program is described which assesses the relative influence of system parameters on the Savonius rotor performance. The parametric study leads to an optimum configuration with an increase in efficiency by around 100 percent compared to the reported efficiency of approx. 12-15 percent. Of particular interest is the blockage correction procedure which is vital for application of the wind tunnel results to a prototype design, and facilitates comparison of data obtained by other investigators. Next, using the concept of a central vortex, substantiated by a flow visualization study, a semiempirical approach to predict the rotor performance using measured stationary blade pressure data is developed. The simple approach promises to be quite effective in predicting the rotor performance, even in the presence of blockage, and should prove useful at least in the preliminary design stages.
Visualization study of the flow in and around a Savonius rotor
Flow in and around a Savonius rotor has been studied by flow visualization experiments, and the rotation effect is discussed in comparison with the measured pressure distributions on the blade surfaces. It is observed that the flow separating regions on the blade surfaces are fairly reduced by the rotation effect and the flow through the overlap is weakened by the appearance of resisting flow. The former contributes to the torque production of the rotating rotor while the latter acts as a resistance. These phenomena together with the stagnation effect on the front side of the rotor contribute to the power producing mechanism of the Savonius rotor.