Active Flow Control for Lift Enhancement and Destruction
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Solution Overview
Problem
Current airfoil designs face challenges in achieving both lift enhancement and destruction, particularly at high angles of attack, due to flow separation and increased aerodynamic loads, which can lead to stall and potential damage, and existing systems are costly and inefficient.
Innovation Solution
An active flow control system utilizing upstream fluid injection leverages the Coandă effect to provide either lift enhancement by mixing high momentum freestream flow with low momentum secondary flow or lift destruction by creating flow blockage, using oscillatory, pulsed, or steady air flows from devices like synthetic jets or plasma actuators, adjustable by operating parameters such as voltage and frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional airfoil designs are used at high angles of attack, then lift is generated, but flow separation occurs causing stall and loss of lift
Solution Approach 1:
The patent applies dynamic flow control by switching between different injection modes (enhancement vs. destruction) based on real-time operating conditions. The system dynamically adjusts the injection flow rate and direction to either enhance lift during normal operation or destroy lift during high-angle-of-attack conditions to prevent stall, making the airfoil's aerodynamic characteristics adaptable rather than fixed.
Solution Approach 2:
The patent changes physical parameters of the fluid injection system, specifically the injection flow rate and momentum ratio, to achieve different aerodynamic outcomes. By varying these parameters, the system can transition between lift enhancement mode (during cruise) and lift destruction mode (during high angle of attack), directly addressing the stall risk while maintaining lift generation capability.
2Productivity
If lift enhancement is achieved through active circulation control, then energy production increases, but aerodynamic loads increase causing blade bending toward the tower
Solution Approach 1:
The patent implements a feedback control system that monitors blade position relative to the tower and operating conditions. When the blade approaches the tower, the system automatically switches from lift enhancement mode to lift destruction mode, reducing aerodynamic loads to prevent blade-to-tower collision while allowing maximum energy production during safe operating conditions.
Solution Approach 2:
The system takes preliminary anti-action by detecting high-angle-of-attack conditions or tower proximity before collision occurs, and preemptively switches to lift destruction mode to reduce aerodynamic loads and prevent harmful effects, rather than reacting after the problem occurs.
3Adaptability or versatility
If a single active system provides both lift enhancement and destruction, then system versatility improves, but device complexity increases
Solution Approach 1:
The patent achieves multi-functionality by using a single fluid injection system that can perform both lift enhancement and lift destruction functions. The same injection devices, when operated at different flow rates and momentum ratios, can either energize the boundary layer to enhance lift or create flow separation to destroy lift, eliminating the need for separate systems for each function.
Solution Approach 2:
The system uses parameter changes (injection flow rate, momentum ratio, injection timing) to achieve different functions from the same hardware. By adjusting these parameters based on operating conditions, the single system can seamlessly switch between enhancement and destruction modes without requiring additional complex hardware.
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 system effectively mitigates stall risk and aerodynamic loads, enabling improved load-bearing performance and energy production by dynamically controlling lift, reducing the risk of blade-to-tower collisions and optimizing aerodynamic profiles for various applications.
Implementation Method 1
Airfoil circulation control typically uses fluid injection in the form of a secondary fluid flow to create a steady wall-jet at the proximity of a rounded surface in a blade to leverage the Coandã effect. The Coandã effect can be defined as the effect by which a fluid jet attaches itself to an adjacent surface, such as an airfoil, and remains attached.
Data Source
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AI summary
A method for actively manipulating a primary fluid flow over a surface (42) using an active flow control system including an active fluid flow device (58) to provide lift enhancement and lift destruction. The method including the disposing of an active fluid flow device in the surface. The active fluid flow device is then operated to generate at least one of a steady blowing secondary fluid flow (62), a pulsed secondary fluid flow or an oscillating secondary fluid flow. While flowing the primary fluid (64) over the surface (42) to create a primary flow field, a secondary fluid flow (62) is injected in an upstream direction and substantially opposed to the incoming primary fluid flow (64). The injecting of the secondary fluid flow in this manner provides for influencing of the primary flow field by manipulating a momentum of the secondary fluid flow to influence the incoming primary fluid flow and resultant lift.