Figure 23 Wind turbine blade roots, courtesy of GE Vernova.
Function
The blade root acts as the interface between the main composite section of the blade and the steel blade bearing.
Who supplies them
An integral element of a blade design, blade roots are designed then manufactured by the blade supplier using bought-in items.
Key facts
The design of the connection to the Blade bearings is critical due to the attachment of a relatively soft composite structure to the stiff bolting and bearing structure.
Differing arrangements are used to provide threaded connection for fasteners connecting the blade bearing. In some cases, a ring is set into the root of the blade. In other cases, inserts are either bonded into holes drilled in the root or inserts are infused during manufacture. Finally, other designs use a single or double row of “IKEA-type” threaded bars, set perpendicular to the direction of orientation of studs.
The composite structure near the blade root is designed to apply even loading around the blade root as well as smooth transfer of load into each insert. The root of the blade must be sufficiently flat so as not to apply excessive uneven load to the blade bearing.
Loading of the root-end and fasteners at the blade root is critical due to the complex geometry, especially of the hub and bearing under load. Development testing of root end strength is common.
What’s in it
- Metal inserts
- Composite structure