Performance analysis of double blade airfoil for hydrokinetic turbine applications

Hydrokinetic energy holds significant promise as a new, carbon-free energy source. The hydrokinetic turbine harnesses the power from moving water without the construction of a darn. Operational effectiveness of the wind and hydrokinetic turbines depend on the performance of the airfoils chosen. Traditionally, standard airfoils, like NACA and GOTINGEN, are used for wind and hydrokinetic turbines generating energy have the maximum lift coefficient about 1.3 at the stall angle of attack, about 12 degrees. At these values, the flow velocities to produce electric energy are 7 m/s and 3 m/s for wind turbine and hydrokinetic turbine respectively. Using double blade airfoil, the fluid dynamics governing the flow field eliminates the separation bubble by the injection of the high momentum fluid through the gab of the double blade of airfoil by meaning of the flow control delays the stall up to an angle of attack of 20 degrees, with a maximum lift coefficient of 2.06. Hence, using double blade airfoils in the wind and hydrokinetic turbines, minimum wind and hydrokinetic flow velocities to produce economical energies will be 3-4 m/s for wind turbines and 1-1.5 m/s or less for hydrokinetic turbines. Consequently, the wind power and hydrokinetic potentials of Turkey will be re-defined and increased accordingly. (C) 2012 Elsevier Ltd. All rights reserved.