Slender Wind Turbine Blade With Vortex Generators
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Solution Overview
Problem
Current wind turbines face high costs due to varying loads, difficulty in predicting aerodynamic characteristics, efficiency drops at reduced tip speed ratios, and increased moments requiring strong materials, leading to flow separation and reduced power production.
Innovation Solution
Implementing airfoils with a 10-minute averaged lift coefficient of more than 1.1, particularly 1.2 and 1.4, and using vortex generators (VGs) to reduce lift variations, postpone stall angles, and integrate lift-enhancing means to minimize load fluctuations and material usage while maintaining efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If airfoils with higher lift coefficients are used to reduce chord length and material usage, then weight and material requirements decrease, but lift force variations increase due to turbulence and flow separation
Solution Approach 1:
Vortex generators act as intermediary elements between the free stream and the boundary layer, creating controlled vortices that enhance mixing and delay flow separation. This mediator approach allows the boundary layer to remain attached longer on high-lift airfoils, reducing lift variations while maintaining the benefits of reduced chord length and material usage
Solution Approach 2:
The invention changes the parameters of the boundary layer by introducing vortex generators that modify its velocity profile and turbulence characteristics. This parameter change allows the boundary layer to resist adverse pressure gradients better, maintaining stable lift forces even with slender airfoils operating at higher lift coefficients
2Reliability
If vortex generators are added to reduce lift variations and delay stall, then reliability and performance in turbulent conditions improve, but device complexity and manufacturing costs increase
Solution Approach 1:
Vortex generators are applied locally at specific positions on the airfoil surface (typically near the leading edge or at critical separation zones) rather than uniformly across the entire blade. This local application provides the necessary flow control exactly where needed to delay separation and reduce lift variations, while minimizing overall device complexity and manufacturing burden
3Loss of substance
If slender blades with reduced chord are used to decrease material usage, then weight and cost decrease, but aerodynamic performance drops due to flow separation and reduced lift
Solution Approach 1:
Vortex generators serve as intermediary devices that enable slender blades to maintain attached flow and high lift coefficients despite their reduced chord. By introducing controlled vortices, they allow the boundary layer to remain stable and delay separation, preserving aerodynamic performance while enabling material reduction through smaller chord dimensions
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 reduces lift force variations by over 30%, mitigates fatigue and extreme loads, allows turbine operation in high turbulence sites, and decreases material requirements, enhancing overall wind turbine performance and reducing production losses due to contamination.
Implementation Method 1
a rotor blade with a plurality of vortex generators (45) projecting from its lee surface for controlling the boundary layer separation
Implementation Method 2
Each vortex generator is formed as a solid and in a top view substantially wedge-shaped body defined by two lateral faces arranged substantially perpendicular to the surface of the blade
Implementation Method 3
The lift L = 1⁄2ρU 2c l c and drag D = 1⁄2ρU 2c l c of an airfoil are both proportional to the chord c and respectively to the lift coefficient c l and the drag coefficient c d
Implementation Method 4
The curve through the centres of circles within the airfoil touching both the lower side and the upper side is called the camber line. The largest distance between the camber line and the chord is the camber
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Wind turbine with a rotor blade wherein said blade is relatively insensitive to turbulence because it is more slender than according to the prior art and is nevertheless able to generate sufficient lift by virtue of the fact that flow enhancing means such as vortex generators combat flow separation. The slenderness is defined by the chord numbers C and D of which C is defined as C = Ncrclrλ2/R2, in which N is the number of blades, cr is the local chord, cl the lift coefficient, r the radial position, λ the tip speed ratio and R the rotor radius. Subsequently, the chord should be less than what follows from the equation C = M in which M=−1.19+9.74Cp−21.01Cp2+17.50Cp3 and Cp is the power coefficient. A wind turbine according to the invention is subject to about 2-12% less operational loads and to about 5-40% reduced survival wind speed loads compared to classical designs.