Velocity and performance correction methodology for hydrokinetic turbines experimented with different geometry of the channel

Abstract

Abstract The aim of the present work is to study the influence of channel geometrical parameters on the performance of Savonius type hydrokinetic turbine and to present velocity correction methodology to determine the actual performance of the turbine. In the present experimental work, the effect of geometry of channel bottom and channel side wall distance on the performance of a Savonius turbine is investigated. Elevated channel bottom (hump) enhances the velocity of flow by reducing the depth of flow. Experimental results indicate that nearly an increase of 83% in power output is achieved by placing the turbine on the hump with reference to the turbine placed at the bottom of the channel. Similarly, the effect of channel sidewall location on the performance of turbine is studied for two separate cases, i. Constant flow rate - water spilling not allowed from blocked region and ii. Variable flow rate -water spilling over the blocked region allowed. In both the cases, the obtained coefficient of power is achieved above 0.45, considering the inlet velocity of flow. The results suggest that the potential head difference between the turbine inlet and outlet has the predominant effect on the power output of the turbine when a rotor is placed between the two closely located side walls. Considering the above facts, a new methodology is developed to find the corrected velocity to correlate the results obtained from restricted, high blockage canal flow with the performance which can be obtained from the same turbine when operated in a negligible blockage flow domain. Experimental results indicate that there is a vast variation in the maximum coefficient of power for all the cases studied if the velocity correction is not considered. However, with the application of the present velocity correction method, the corrected results are closer with the unblocked case.