Angled Comb Elements for Wind Turbine Trailing Edge Noise Reduction
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Solution Overview
Problem
Wind turbine rotor blades generate significant noise due to trailing edge noise, which existing serrated or comb element designs only partially address, leaving substantial noise levels unchanged and limiting their effectiveness in reducing aerodynamic noise.
Innovation Solution
The implementation of a plurality of rectangular or angular comb elements, known as 'canopy comb elements,' which are inclined at an angle to the rotor blade surface, acting as a 'canopy' to push the boundary layer outward and stabilize turbulent airflow, thereby reducing acoustic scattering at the trailing edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If trailing edge serrations are used to reduce noise, then trailing edge noise is reduced to some extent, but significant noise levels remain and the effect is limited
Solution Approach 1:
The trailing edge is segmented into multiple serrations that create individual comb elements, which divide the turbulent boundary layer into smaller segments. This segmentation prevents the formation of large coherent vortices and reduces the intensity of trailing edge noise more effectively than a straight edge.
Solution Approach 2:
Comb elements are added in the spanwise dimension (perpendicular to the chordwise direction), creating a three-dimensional structure from the two-dimensional serrations. This additional dimension further diffuses turbulence and enhances noise reduction by disrupting vortex structures in multiple directions.
2Object-affected harmful factors
If in-plane comb elements are arranged between serrations to improve noise reduction, then trailing edge noise is further reduced, but turbulence upstream of the trailing edge remains unaffected
Solution Approach 1:
Comb elements are positioned upstream of the trailing edge to act on the turbulent boundary layer before it reaches the trailing edge. This preliminary action stabilizes the incoming turbulence and reduces the intensity of vortices that would otherwise generate noise at the trailing edge.
Solution Approach 2:
Comb elements serve as intermediary structures between the turbulent boundary layer and the trailing edge, mediating the interaction by diffusing and stabilizing turbulence. This intermediary action reduces the direct coupling between incoming turbulence and trailing edge noise generation.
3Object-affected harmful factors
If rotor blade rotational speed is reduced to minimize noise, then noise level is reduced, but power output suffers substantial penalty
Solution Approach 1:
The aerodynamic parameters of the trailing edge are changed by introducing serrations and comb elements, which modify the flow characteristics and noise generation mechanisms. This allows the blade to maintain its rotational speed and power output while reducing noise through altered trailing edge geometry rather than speed reduction.
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 significantly reduces noise emissions from wind turbines, allowing them to operate at rated power output while meeting acoustic regulations, enabling closer installation to residential areas and reducing the need for power curtailment.
Implementation Method 1
The embodiments are based on the insight that trailing edge noise can be further reduced when the boundary layer is pushed away from the airfoil surface
Implementation Method 2
The cause of trailing edge noise can also be regarded as a distribution of unstable surface pressures at the trailing edge. The surface pressures are the footprint or signature of the turbulent boundary layer
Implementation Method 3
The beneficial acoustic effect of such comb elements may be understood to arise from diffusion of a horseshoe vortex (i.e. the combs between serrations break up a large vortex into smaller vortices)
Data Source
AI summary
Provided is an aerodynamic structure for mounting to a surface of a wind turbine rotor blade, which aerodynamic structure includes a plurality of rectangular comb elements and/or a plurality of angular comb elements, wherein a comb element includes comb teeth arranged in a comb plane that subtends an angle to the surface of the rotor blade. The embodiments further describe a wind turbine rotor blade including such an aerodynamic structure.