Numerical investigation on the use of multi-element blades in horizontal axis hydrokinetic turbine

This paper presents the sizing of the blades of a 1 kW hydrokinetic turbine with 3 blades with hydrodynamic multi-element profiles using the Blade Element Momentum theory (BEM). The hydrodynamic profile used was the Eppler 420. The turbine was designed from a water flow velocity of 1.5 m/s with a tip speed ratio of the blade (lambda) of 6.325, a pitch angle of the blade section (theta) of 0 degrees, a power coefficient of 0.4382 and a mechanical efficiency of 70%. The Eppler 420 multi-element profile was selected for the design of the blade because it has a high ratio between the lift coefficient and the drag. A 2D computation study in the JavaFoil code of the Eppler 420 profile was carried out in order to determine the optimal lengths of the main element and the optimal flap for a deflection angle of 30 degrees under conditions of a low Reynolds number.