Wind Turbine Rotor Blade Load Emulator Stiffness Augmentation
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Solution Overview
Problem
The existing methods for conducting fatigue tests on long wind turbine rotor blades are hindered by the need for large, cumbersome load frames that can damage the blades and result in undesirably large oscillations, leading to potential blade failure and limited understanding of the blade's loading capacity, due to weight restrictions and friction issues.
Innovation Solution
A wind turbine rotor blade load emulator arrangement that includes a stiffness augmentation assembly, comprising end fittings and a tensile element, such as springs or mesh, to increase the rotor blade's stiffness in specific regions, reducing the need for heavy load frames and minimizing oscillations during testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If large load frames are used to achieve desired dynamic moment, then the fatigue test can be conducted, but the rotor blade may be damaged during mounting and testing
Solution Approach 1:
A load emulator arrangement is introduced as an intermediary device between the exciter and the rotor blade. This emulator comprises a mass element and a stiffness element that collectively reproduce the desired dynamic moment while distributing loads more evenly, thereby preventing blade damage during mounting and testing.
Solution Approach 2:
The invention changes the parameters of the testing system by replacing heavy load frames with a load emulator having optimized mass and stiffness characteristics. The emulator is designed with specific mass (1-10% of blade mass) and stiffness properties that allow achieving the required dynamic moment while reducing peak loads on the blade structure.
2Speed
If heavy load frames are used to achieve target oscillations in root end, then the fatigue test can be performed, but undesirably large oscillations occur in shoulder or transition region
Solution Approach 1:
The load emulator applies localized mass and stiffness characteristics at the root end region without affecting other parts of the blade. By concentrating the inertial effect locally rather than using distributed heavy load frames, the system achieves target oscillations in the root end while minimizing unwanted oscillations in the shoulder or transition region.
3Force
If large load frames are used during fatigue test, then the desired dynamic moment is achieved, but friction heating causes contact area to become brittle and deteriorate
Solution Approach 1:
The load emulator acts as an intermediary that reduces direct contact friction between the load application device and the blade surface. By using a mass element that generates inertial forces rather than relying on friction-based force transmission, the system achieves the required dynamic moment while minimizing friction heating and contact area deterioration.
4Reliability
If multiple load frames are used along the rotor blade, then the fatigue test coverage is improved, but the device complexity and handling difficulty increase
Solution Approach 1:
The invention extracts the essential function of multiple load frames and consolidates it into a single load emulator arrangement. By removing the need for multiple distributed load frames and replacing them with one emulator having optimized mass and stiffness properties, the system maintains adequate test coverage while significantly reducing device complexity and handling requirements.
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 allows for more precise and thorough fatigue testing by reducing the likelihood of damage and enhancing data collection, while adhering to weight restrictions, thereby improving the understanding of the rotor blade's loading capacity and performance.
Implementation Method 1
a stiffness augmentation assembly, comprising end fittings and a tensile element, such as springs or mesh, to increase the rotor blade's stiffness in specific regions
Implementation Method 2
An electric or hydraulic exciter is coupled to one or more of the load frame fittings, for example by means of a rod. To carry out the fatigue test, the exciter repeatedly moves the actuator back and forth, thereby effecting an oscillation of the rotor blade.
Data Source
AI summary
A wind turbine rotor blade load emulator arrangement includes a support unit constructed to support a rotor blade during a fatigue test procedure; an exciter configured to deflect the rotor blade during a fatigue test procedure; and a stiffness augmentation assembly for mounting to the rotor blade over a mounting length, which stiffness augmentation assembly is realized to increase the stiffness of the rotor blade in the mounting length. A method of carrying out a fatigue test procedure on a wind turbine rotor blade uses such a load emulator arrangement.