Blade number effect on the optimal energy efficiency for a modified Savonius rotor

In this paper, the effect of the number of blades on the optimal energy utilisation efficiency for a modified Savonius rotor with rotor diameter of 4 m is investigated by computational fluid dynamics simulation using a uniform test method. The appropriate computational domain of a numerical model is determined by first analysing the relative error of the outlet wind velocity on the outflow boundary of the domain. Taking the rotor rotation speed, the blade width and blade installation angle of the modified Savonius rotor as three key factors, it obtains the optimal energy utilisation efficiencies for the modified Savonius rotors with eight, nine and ten blades by transient numerical simulations under the condition of wind velocity of 8 m/s. The sliding mesh and the Piso (pressure implicit with splitting of operators) scheme are utilised in Fluent software simultaneously. The results demonstrate that the optimum wind energy utilisation efficiency rises and the corresponding blade width decreases with the number of blades.