Hub Description

Figure 1 is a side elevation view of a portion of a wind turbine fitted with a teetering hub assembly that is undergoing teetering. The wind turbine includes a nacelle, a vertically-aligned tower, turbine blades coupled to the hub shell, and a hub shaft extending between the nacelle and the hub shell. The turbine blades and the teetering hub assembly in combination form a rotor of the wind turbine. During teetering, at least one turbine blade moves forward and at least one turbine blade moves backward while the rotor rotates relative to the nacelle. In this example, the topmost turbine blade is rotated (or tilts) backward by 10° and the two other turbine blades are rotated (or tilt) forward by 5°. During teetering, the hub shaft remains oriented horizontally whereas the hub shell and turbine blades tilt back and forth, e.g., ± 10° when oriented at different positions during rotation of the rotor. In the depiction shown in Figure 1, the nacelle and tower are downstream of the rotor, such that wind impinges on the rotor before impinging on the tower. This is an upwind configuration that was modeled using FAST software. In a downwind configuration, the wind would come from the opposite direction of the arrow shown in Figure 1 and impinge on the nacelle and the tower before impinging on the rotor. The teetering hub assembly can be used in either the upwind or downwind configurations. The interior of the nacelle is not shown because it does not differ from commercially-available horizontal axis wind turbines, that are typically equipped with an electric generator arranged to receive torque supplied by the hub shaft, and that the nacelle is preferably arranged to rotate relative to a vertical yaw axis extending through the tower.

The main difference between the teetering hub and a rigid hub is the means for passing torque from the blades to the main shaft. With a rigid hub, the hub and main shaft move together and torque is passed from hub to the main shaft at the rear of the hub. With the teetering hub, the hub shell is free to move, or teeter, with respect to the hub shaft while torque is being passed from the hub shell to the hub shaft. The hub shaft is either part of or affixed to the main shaft. Otherwise the construction of the hub shell can be made to be very similar to that of a rigid hub.  Prior patents by A. Ramsland described use of a ball-and-socket design.  The design shown here does not rely on a ball-and-socket.  Elimination of the ball-and-socket has significantly reduced the weight and very significantly improved the strength of the hub.

 

Figure 2 is a perspective view of the exterior portion of the teetering hub assembly.  As shown, a hub shaft extends through a hub shell opening arranged along a rear of a hub shell. The diameter of the hub shell opening is somewhat greater than the diameter of the hub shaft in order to provide room for limited teetering of the hub shell. No teetering deflections are shown in Figure. 1, as evidenced by the uniform distance between the hub shaft and the hub shell opening. Figure. 1 shows a turbine blade connector fitted within the hub shell. The turbine blade connector has a series of blade connector holes used for connection to a turbine blade.  In this embodiment, it is possible to change the pitch angle of a turbine blade received by the turbine blade connector by use of a slewing drive. The slewing drive includes a ring gear arranged to cooperate with a worm gear.