Wind Turbine Rotor Blade Shear Web Torsional Stiffness
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Solution Overview
Problem
Conventional wind turbine rotor blades experience reduced torsional stiffness at the outboard locations, leading to increased twist and reduced energy capture, particularly at the blade tip, necessitating an improvement in structural rigidity without excessive weight increase.
Innovation Solution
A dual shear web configuration is introduced, with a first shear web extending from the blade root to an intermediate span location and a second shear web overlapping the first, extending towards the tip, optionally with a third shear web, to enhance torsional rigidity and change the shear-center of the rotor blade's cross-section, while cut-outs provide stress relief.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single web design is used to promote torsional rigidity, then the blade structure is simplified, but the torsional stiffness is insufficient at outboard locations
Solution Approach 1:
The blade is divided into multiple span zones with different shear web configurations. The first span (root to intermediate location) contains a first shear web, while the second span (intermediate location to tip) contains a second shear web. This segmentation allows each zone to be optimized for its specific structural requirements, increasing torsional stiffness where needed without unnecessarily complicating the entire blade structure.
Solution Approach 2:
Different shear web configurations are applied to different locations along the blade span. The first shear web extends from the root to an intermediate span location, while the second shear web extends from the intermediate location to the tip. This local differentiation addresses the specific need for increased torsional stiffness at outboard locations without adding complexity to the entire blade structure.
2Weight of moving object
If the chord and thickness of the airfoil are reduced, then the blade weight is decreased, but the torsional stiffness drops quickly
Solution Approach 1:
The dual shear web configuration is specifically implemented at outboard locations where the chord and thickness are reduced. By concentrating the structural reinforcement where the airfoil dimensions are minimized, the design compensates for the reduced torsional stiffness in these specific zones without increasing the weight of the entire blade.
Solution Approach 2:
The blade span is segmented into zones with different structural characteristics. The dual shear web configuration is applied selectively to the second span (intermediate location to tip) where the chord and thickness reductions occur, allowing weight optimization in other areas while maintaining sufficient torsional stiffness where needed.
3Ease of operation
If the blade tip experiences greater twist, then the angle of attack changes, but the energy capture is impacted negatively
Solution Approach 1:
The dual shear web configuration modifies the torsional stiffness distribution along the blade span, creating a more optimized twist curve. By increasing torsional stiffness at outboard locations, the blade maintains a more consistent angle of attack along its span, reducing excessive tip twist and improving energy capture efficiency.
Data Source
AI summary
A rotor blade for a wind turbine includes an upper shell member having a spar cap configured on an internal face thereof, a lower shell member having a spar cap configured on an internal face thereof, and a shear web assembly extending between the spar caps along a longitudinal length of the rotor blade. The shear web assembly includes, at least, a first shear web and a second shear web. The first shear web starts at a blade root of the rotor blade and extends to an intermediate span location. The second shear web overlaps the first shear web at the intermediate span location and extends towards a blade tip of the rotor blade so as to provide increase torsional rigidity to the rotor blade.