Span-wise comb elements for wind turbine trailing edge noise
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Solution Overview
Problem
Existing solutions for reducing wind turbine rotor blade noise, such as serrated trailing edges and in-plane comb elements, are limited in their ability to address turbulence upstream of the trailing edge, resulting in significant residual noise levels.
Innovation Solution
The implementation of span-wise separator comb elements mounted perpendicular to the trailing edge and airfoil surface of the rotor blade, which act to diffuse turbulence and break up vortices, thereby reducing aerodynamic noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If serrated trailing edges and in-plane comb elements are used to reduce trailing edge noise, then trailing edge noise is reduced to some extent, but significant noise levels remain due to inability to address turbulence upstream of the trailing edge
Solution Approach 1:
The patent transitions from in-plane comb elements (lying in the same plane as the trailing edge) to span-wise comb elements (extending perpendicular to the trailing edge plane). This dimensional change allows the comb elements to effectively address turbulence upstream of the trailing edge by extending into the spanwise direction, thereby reducing the residual noise levels while maintaining structural manageability.
2Object-generated harmful factors
If rotational speed is reduced to reduce noise from aerodynamic rotor, then noise level is reduced, but power output suffers a substantial penalty
Solution Approach 1:
The patent extracts and addresses the specific source of noise (turbulence upstream of the trailing edge) through span-wise comb elements, rather than reducing the overall rotational speed. By targeting and eliminating the specific turbulence source, the solution reduces noise while preserving the rotational speed and associated power output.
3Object-generated harmful factors
If comb elements are arranged in the plane of main airflow direction to diffuse turbulence, then trailing edge noise is reduced, but turbulence upstream of the trailing edge is not significantly affected
Solution Approach 1:
The patent reorients the comb elements from lying in the plane of main airflow direction to extending span-wise (perpendicular to the trailing edge plane). This dimensional reorientation enables the comb elements to effectively interact with and diffuse turbulence upstream of the trailing edge, thereby improving adaptability and versatility in addressing noise sources at different locations.
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 effectively reduces aerodynamic noise by smoothing instabilities in the boundary layer as it passes over the trailing edge, thereby meeting acoustic noise regulations even at rated power output.
Implementation Method 1
Eddies develop when the air flows over the suction side or the pressure side, resulting in turbulence passing the trailing edge of the blade. The noise that mainly arises when this turbulence passes the trailing edge is referred to as 'trailing edge noise'.
Implementation Method 2
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) and/or dissipation of some of the energy in the turbulent airflow.
Data Source
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AI summary
The invention describes an aerodynamic structure (1) for mounting to a surface (20S, 20P, 30) of a wind turbine rotor blade (2), which aerodynamic structure (1) comprises a number of comb elements (10T, 10F), a comb element (10T, 10F) comprising comb teeth (100) arranged in a comb plane (10P), characterized in that the comb plane (10P) of a mounted comb element (10T, 10F) is essentially perpendicular to the trailing edge (TE) of the rotor blade (2) and to the airfoil surface (20S, 20P) of the rotor blade (2). The invention further describes a wind turbine rotor blade (2) comprising at least one such aerodynamic structure (1), and a method of equipping a wind turbine rotor blade (2) with such an aerodynamic structure (1).