development of blade element momentum theory for unsteady flow with regard to the dynamic stall phenomenon

The first step in turbine blade design is to select TSR. Therefore, an optimization procedure should be applied to find the best ratio since this directly affects the energy generated from the turbine. In this research the optimum TSR are calculated with regard to the dynamic stall phenomenon. The dynamic stall imposes large amplitude loading on airfoil sections and since it occurs in HAWT operating envelope in unsteady flow. The purpose of this study was to investigate the effect of unsteady flow with periodic oscillation on the performance of HAWT turbines. A DS model is implanted to analyze the static data. Then the Beddoes-Leishman DS model was tailored to the HAWT environment. Then, using this model and BEMT, the optimal TSR is calculated And the impact of the presence of dynamic stall is shown. Also, Cp and CT are plotted in several different TSR with different time steps to express the effects of Unsteady phenomenon. In addition to dynamic results, static and steady results are plotted in power and thrust graphs. This phenomenon affect the efficiency by -3% as compared to the static stall. Also the Optimum TSR increases in dynamic mode. Examination of the time average diagrams of the drag coefficient shows that the delay in separation starts approximately from the midpoints of the blade and reaches the maximum value at the root.