Effects of the deflector plate on performance and flow characteristics of a drag-type hydrokinetic rotor

Abstract

An experimental work was conducted to investigate effects of the deflector plate on the performance and flow characteristics of a drag-type hydrokinetic rotor. A measurement device was specifically designed to record instantaneous rotational speed and output torque of the hydrokinetic rotor. The performance of the rotor and the near-rotor flow were studied comprehensively. The deflector angle and the upstream velocity were varied. The results show that the maximum power coefficient of the rotor reaches 0.463 at the deflector angle of 60°, approximately 2.5 times that obtained at the deflector angle of 30°. As the upstream water velocity increases from 0.63 m/s to 0.73 m/s, the maximum power coefficient of the rotor is increased by 22.8%. The deflector plate not only prevents the impingement of the upstream flow on the returning blade, but also guides the upstream flow toward the concave side of the advancing blade. As the deflector angle increases, more upstream water with high velocity is guided toward the concave side of the advancing blade. The Coanda-like flow arising at the convex side of the advancing blade is beneficial for the improvement of the rotor performance and is enhanced with increasing deflector angle. The effect of the deflector plate on the operation of the Savonius hydrokinetic rotor was clarified and the conclusions provide a sound support for the improvement of the rotor performance.