Momentum Theory of Diffuser Augmented Wind Turbine

Abstract

Momentum theory of diffuser augmented wind turbine (DAWT) or all-directional wind acceleration tower (ADWAT) was treated, basically with Bernoulli's equation, the actuator disk theory and the equation of continuity. Then, output coefficients of the turbine were deduced as functions of load factor of the turbine, area ratio and efficiency of the diffuser. Through the numerical computation and the investigation of the resulting equations, the following has been ascertained. If there is no momentum loss in the diffuser flow, the maximum output coefficient of the turbine, based on the diffuser exit area, is found to be 0.385 with suitable combinations of the load factor and the area ratio. The effect of the diffuser efficiency becomes severer in the case of a larger area ratio of the diffuser and a lighter load factor of the turbine. Hence, it has been suggested that the reasonable area ratio of the diffuser and the load factor of the turbine are around 1:3 and 0.5, respectively. The output coefficient of the turbine based on the turbine area may be expected to be about 0.7.