| 摘要 |
A wind turbine blade configured such that the lift force from the blade airfoil is always normal, or nearly normal, to the shaft torque. This objective may be achieved by a) having the airfoil chord always aligned to the actual wind direction (subject only to small angle of attack variations), and b) slowing the turbine rotation rate so that no blade twist is needed. As a result, blade tip speed due to shaft rotation is less than the wind speed. The lift force from the blade airfoil directly drives the torque on the shaft, so the control problemsimplifies to adjusting the blade angle of attack to keep the lift constant across varying wind speeds. For most airfoils, a slightly negative angle of attack results in zero lift. This fail-safe condition is operable up to very high windspeeds, eliminating any need to provide for turbine overspeed control. |
