《小型风力发电机组叶片设计》（英语）D. H. Wood

cai1972

ABSTRACT
Experimental studies of the starting behaviour of small wind turbines have shown that the initial “idling period”, characterised by small rotor acceleration, is usually much longer than the subsequent period of rapid accleration to reach operational rotor speed. Idling obviously reduces the power generation potential of any turbine. The experimental results also imply that most starting torque is generated near the hub, whereas power-producing torque is concentrated near the tip. Therefore this paper considers the computational design of blades for small wind turbines for the dual purposes of (i) efficient power production at rated wind speeds and (ii) rapid starting at smaller wind speeds. Standard blade element theory is used to determine the power coefficient, which is the first objective function to be maximised. A modified blade element method gives the start, whose inverse is the second objective function. During the idling period, the blade angles of attack are relatively large, allowing the lift and drag to be modelled using “generic” flat-plate equations with a small adjustment for the particular aerofoil. No power is extracted from the wind while the blades are accelerated by the aerodynamic torque. Starting is deemed to be complete at a tip speed ratio representing the end of the idling period, which considerably less than the period for power generation.