Slitted Aeroshell Extender for Wind Turbine Blade Strain Relief
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Solution Overview
Problem
Wind turbine blades with aeroshells face high stress levels at the extended trailing edge, requiring additional reinforcement that increases weight and cost, while existing solutions do not adequately address flexibility and aerodynamic performance.
Innovation Solution
A slitted or slotted aeroshell extender piece is fitted to the inboard portion of the wind turbine blade, providing flexibility and reducing strain, with slits dimensioned to be aerodynamically insignificant and reinforced with flexible materials or bristles to maintain performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a rigid aeroshell extender piece is used to provide aerodynamic profile, then aerodynamic performance is improved, but stress concentration and strain at the trailing edge increase requiring additional reinforcement
Solution Approach 1:
The extender piece is divided into multiple segments along its length, allowing each segment to move independently and accommodate stress variations without concentrating strain at the trailing edge, thereby maintaining aerodynamic shape while reducing stress concentration
Solution Approach 2:
The extender piece is constructed as a flexible shell structure that can deform elastically under operational loads, absorbing stress through controlled deformation rather than rigid resistance, which reduces the need for additional reinforcement materials
2Reliability
If additional reinforcement material is added to the aeroshell extender piece to withstand stress, then strength and reliability are improved, but weight and manufacturing cost increase
Solution Approach 1:
The material properties of the extender piece are optimized by selecting materials with high strength-to-weight ratio and adjusting structural parameters such as wall thickness and segment geometry to achieve the minimum necessary reinforcement for reliable operation without excess weight
Solution Approach 2:
By segmenting the structure, reinforcement is applied locally only where stress concentrations occur rather than uniformly throughout the entire extender piece, reducing the total amount of reinforcement material needed and thereby reducing overall weight and cost
3Strength
If the extender piece is made flexible with slits to reduce strain, then stress resistance is improved, but aerodynamic performance may be degraded
Solution Approach 1:
The slits create segments that are spaced and dimensioned to maintain overall aerodynamic continuity while allowing local flexibility, ensuring that the aerodynamic profile is preserved from a distance while strain is reduced at the segment levels
Solution Approach 2:
The flexibility is introduced locally at specific slit positions where it provides the necessary strain relief, while the overall aerodynamic surface maintains its integrity and smooth contour for optimal airflow, achieving both flexibility and aerodynamic performance
Data Source
Figure 1
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AI summary
A flexible aeroshell extender piece for an inboard part of a wind turbine blade is described, along with an associated method of manufacture. The flexible aeroshell is formed by first assembling a consolidated aeroshell piece, and then making a series of slits at the trailing edge of the aeroshell piece. Such a construction provides an 5 aeroshell having a relatively flexible trailing edge section, which allows for bending or flexing of the aeroshell trailing edge during wind turbine blade operation.