Wind Turbine Blade Asymmetric Spar Caps for Edgewise Vibration Damping
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Solution Overview
Problem
Larger rotor diameters in wind turbines increase structural demands and lead to significant edgewise vibrations with low aerodynamic damping, posing a risk of fatigue failure due to complex loading scenarios.
Innovation Solution
A wind turbine blade design with asymmetric spar caps and shear webs, providing a structural pitch angle by varying the chordwise distances and widths of spar caps, coupled with flapwise bending to enhance aerodynamic damping of edgewise vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If larger rotor diameters are used to increase swept area and energy capture, then energy production is improved, but structural demands and edgewise vibration loads increase
Solution Approach 1:
The patent applies asymmetry by positioning the suction-side spar cap at a different chordwise distance from the shear web line compared to the pressure-side spar cap. This creates an asymmetric structural configuration that generates a structural pitch angle, coupling edgewise bending with flapwise bending to increase aerodynamic damping and reduce edgewise vibration loads in larger rotor blades
2Reliability
If edgewise vibrations occur in slender blades, then aerodynamic damping is reduced, but vibration amplitude increases leading to fatigue failure
Solution Approach 1:
The asymmetric spar cap arrangement creates a structural pitch angle that couples edgewise bending with flapwise bending. This coupling increases the aerodynamic damping of edgewise vibrations by utilizing the larger air displacement characteristic of flapwise motions, thereby reducing vibration amplitude and improving fatigue resistance
Solution Approach 2:
The patent introduces dynamic coupling between edgewise and flapwise bending modes through the structural pitch angle. This dynamic interaction allows the blade to utilize flapwise aerodynamic damping to suppress edgewise vibrations, transforming the static structural configuration into a dynamically coupled system that actively dampens harmful vibrations
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
The design increases aerodynamic damping of edgewise vibrations, improving load resistance and aeroelastic stability while maintaining manufacturability and structural integrity.
Implementation Method 1
The frequencies are known as natural frequencies and each corresponds to a specific vibration shape or vibration mode. The vibration shapes can broadly be categorised into flapwise bending, edgewise bending, and twisting. All types of vibration can apply significant loads on the blade which can lead to fatigue failure. It is therefore important to avoid excitation of these vibrations but also damping them once being excited.
Implementation Method 2
the one or more suction-side spar caps and the one or more pressure-side spar caps provide the main bending stiffness of the wind turbine blade along a major principal axis defining a structural pitch angle of at least 1° with respect to the chord line
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A wind turbine blade comprising a plurality of spar components extending along the longitudinal axis and providing the main bending stiffness of the wind turbine blade a major principal axis defining a structural pitch angle of at least 1° with respect to a chord line, and including: one or more suction-side spar caps each having a centre line; one or more pressure-side spar caps each having a centre line; and one or more shear webs distributed around a central shear web line and at least one of which being connected to first spar caps, wherein at least one suction-side spar cap centre lines is arranged with a first chordwise distance to the central shear web line, and at least one pressure-side spar cap centre lines is arranged with a second, different, chordwise distance to the central shear web line.