Wind Turbine Rotor Bushing Angular Displacement
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Solution Overview
Problem
Wind turbine rotor blades and hubs experience severe stress due to centrifugal and bending forces, leading to fatigue failure in traditional bushing and stud connections, which are not efficiently designed to accommodate high bending stresses, resulting in costly and heavy components.
Innovation Solution
A non-rigid coupling system for wind turbine rotor blades and hubs, where bushings with a longer internal thread than the stud thread allow for angular displacement of the stud, reducing stress concentration and accommodating high centrifugal forces, particularly bending stresses, by providing a degree of rotation to the stud relative to the bushing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional rigid bushing and stud connections are used to connect blades to hub, then connection strength is improved, but bending stress accommodation deteriorates and fatigue failure occurs
Solution Approach 1:
The patent transforms the rigid static connection into a dynamic system by introducing a spherical bearing at the end of the bushing. This allows the stud to rotate and accommodate bending forces dynamically, converting the static rigid connection into a dynamic adaptive connection that can handle varying load directions without fatigue failure.
Solution Approach 2:
The patent changes the physical state of the connection by introducing a spherical bearing that enables rotational movement. This parameter change from fixed position to variable angular position allows the connection to adapt to bending stresses while maintaining tensile strength, resolving the contradiction between strength and fatigue resistance.
2Reliability
If heavy construction is used for blade and hub connection parts, then connection reliability is improved, but component weight and cost increase
Solution Approach 1:
The spherical bearing introduces a parameter change that enables rotational freedom, allowing lighter components to handle bending stresses through movement rather than through mass. This transforms the solution from relying on heavy construction to relying on kinetic adaptation, reducing weight while maintaining reliability.
3Force
If spherical bearing is added to bushing ends to absorb centrifugal forces, then centrifugal force accommodation is improved, but bending stress accommodation deteriorates
Solution Approach 1:
The spherical bearing creates a dynamic connection that can simultaneously handle both centrifugal forces and bending stresses. The rotation capability allows the stud to adapt to bending moments while the bearing structure maintains centrifugal force absorption, resolving the apparent contradiction between these two force accommodations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution significantly reduces fatigue damage from bending stresses, allowing for smaller diameter studs and potentially lighter, less expensive components while effectively managing high centrifugal forces, with bending stress reduction reaching up to 80% of total fatigue damage.
Implementation Method 1
The ends of the bushings have respective cup bearings having spherical faces in order to absorb centrifugal forces of the blades
Implementation Method 2
such that no rigid coupling is provided between the blade portion and the hub portion, and high centrifugal forces acting on the hub, and in particular the resulting bending stresses, can be efficiently accommodated
Data Source
AI summary
It includes a rotatable hub carrying blades and a device for attaching a portion of the blades to a portion of the hub. The attaching device includes bushings inside of which corresponding studs can be secured. At least some of the bushings are provided with at least one securing end adapted for providing the stud with a degree of rotation relative to the bushing. Bushings may include an inner receiving member for receiving a corresponding end of the stud. The receiving member can be rotated inside the bushing around an axis.