Optical Fiber Strain Sensing for Wind Turbine Blade Testing
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Solution Overview
Problem
Current wind turbine blade testing methods using strain gauges face challenges with low spatial resolution, leading to inadequate characterization of physical properties like longitudinal mass distribution and bending stiffness, and are cumbersome due to extensive cabling and vulnerability to electromagnetic interference.
Innovation Solution
The method involves installing mono-mode optical fibers along the leading and trailing edges and both sides of the blade, using Rayleigh scattered light to measure strain distributions, allowing for high-spatial resolution measurements of flapping and edge bending stiffness and longitudinal mass distribution, both at the factory and in the field, with a simple and robust installation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are used to measure strain distribution along the blade, then the measurement system is simple to implement, but the spatial resolution is low and information is lost between discrete gauge locations
Solution Approach 1:
The patent replaces traditional electrical strain gauges with optical fibers that use Rayleigh scattered light to measure strain. This substitution eliminates the need for extensive electrical cabling while providing continuous high-spatial resolution measurements along the entire blade length, directly resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent introduces optical fibers as an intermediary medium that carries strain measurement information along the blade. The optical fibers act as continuous sensors that distribute measurement capability throughout the blade structure without requiring discrete electrical connections at each measurement point, thereby reducing cabling complexity while maintaining high spatial resolution
2Reliability
If strain gauges are installed on the blade, then the installation process is straightforward, but the system becomes vulnerable to electromagnetic interference
Solution Approach 1:
The patent replaces electrical strain gauge systems with optical fiber-based measurement systems. Since optical fibers use light rather than electrical signals, they are inherently immune to electromagnetic interference, significantly improving reliability while the fiber optic cabling is less susceptible to interference than traditional electrical wiring
3Productivity
If the blade size increases, then the power generation capacity improves, but the number of strain gauges required increases rapidly
Solution Approach 1:
The patent implements a universal optical fiber measurement system that can continuously monitor strain across the entire blade structure regardless of blade size. A single optical fiber can provide measurements at multiple locations along the blade, making the system scalable and eliminating the need to proportionally increase the number of discrete sensors as blade dimensions grow
4Loss of information
If discrete strain gauges are used, then the measurement system is easier to install, but information is lost in non-linear areas between gauge locations
Solution Approach 1:
The patent implements continuous strain measurement along the entire blade using optical fibers, eliminating the discrete measurement gaps inherent in traditional strain gauge systems. The continuous optical fiber sensor provides uninterrupted strain data throughout the blade structure, preventing information loss in non-linear areas while maintaining installation feasibility through integrated fiber placement
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 approach provides accurate, continuous monitoring of bending stiffness and mass distribution, enabling effective quality control during manufacturing and throughout the blade's lifetime, reducing the risk of defects and failures by detecting local changes and maintaining high precision with minimal interference.
Implementation Method 1
obtaining the strain distribution produced by said load or loads along the blade using a suitable external equipment connected to the free end of at least one of said cables for measuring the strain using Rayleigh scattered light
Data Source
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AI summary
Testing method for determining the distribution of a physical property along a wind turbine blade comprising the following steps: a) installing inside the blade a first optical fibre cable (13) along the leading and trailing edges and a second and third centered optical fibre cables (14, 15) at both sides of the blade (9), leaving in them a free end; b) applying one load to the blade (9) in a test bench (10) placed at the blade factory; c) obtaining the strain distribution produced by said load along the blade (9) using a suitable external equipment connected to said free end for measuring the strain using Rayleigh scattered light; d) determining the distribution of said physical property from said strain distribution; e) comparing the distribution of said physical property with its design distribution. The invention also comprises a method of installation of said cables.