Variable Camber Leading Edge for Transonic Wave Drag Reduction
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Solution Overview
Problem
Aircraft operating in transonic regimes face significant wave drag issues due to shock waves on wing surfaces, which limit high-speed cruise speeds, increase fuel costs, and cause stability and control problems, with existing solutions like supercritical airfoils and variable camber trailing edges having limited effectiveness.
Innovation Solution
A method involving a selectively movable airfoil with a variable camber leading edge and trailing edge, which changes positions based on speed to generate shock waves near the leading edge or trailing edge, reducing wave drag by creating oblique shock waves that weaken aft shock waves, thereby optimizing lift-to-drag ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the airfoil uses a conventional fixed geometry design, then the structure is simple and manufacturing is easy, but wave drag increases significantly at transonic speeds
Solution Approach 1:
The airfoil employs a variable camber leading edge that can dynamically adjust its position between multiple discrete configurations (first, second, and third positions) based on flight conditions. This dynamic adjustment allows the airfoil to optimize its shock wave characteristics at transonic speeds while maintaining simplicity at subsonic speeds, resolving the contradiction between manufacturing simplicity and wave drag reduction.
Solution Approach 2:
The invention changes the geometric parameters of the airfoil by moving the leading edge between different positions, each corresponding to a specific camber configuration. This parameter change enables the airfoil to adapt its shock wave generation characteristics to minimize wave drag at transonic speeds while maintaining ease of manufacture through discrete, identifiable configurations.
2Object-affected harmful factors
If the airfoil uses a supercritical airfoil design with larger nose radius and flatter upper surface, then wave drag is reduced, but the device complexity increases
Solution Approach 1:
Rather than using a single complex supercritical geometry, the invention employs a dynamic system that can switch between multiple discrete leading edge positions. Each position provides a simplified geometric configuration that is easier to manufacture, while the ability to switch between them provides the adaptability of complex geometries without the manufacturing complexity.
Solution Approach 2:
The airfoil leading edge is segmented into multiple discrete positions (first, second, and third positions) that can be selectively activated. This segmentation allows the system to use simple geometric configurations for each position while maintaining the overall complexity management through discrete, manageable options rather than a single complex continuous design.
3Object-affected harmful factors
If the airfoil uses variable camber trailing edge devices to reduce overall wing drag, then drag is reduced, but the effectiveness is limited by wing geometry including sweep and thickness characteristics
Solution Approach 1:
The invention applies variable camber specifically to the leading edge portion of the airfoil, creating localized shock wave management at the critical forward portion where shock waves first form. This local approach to camber variation provides greater adaptability and effectiveness compared to trailing edge devices, as it directly addresses the shock wave generation point rather than being limited by overall wing geometry constraints.
Solution Approach 2:
The leading edge is made dynamically adjustable with multiple discrete positions that can be selected based on flight conditions. This dynamic capability provides greater versatility and adaptability than fixed trailing edge devices, allowing the airfoil to optimize its performance across different speed regimes and flight conditions without being constrained by fixed wing geometry.
4Object-affected harmful factors
If the airfoil moves to positions that generate shock waves near the leading edge, then wave drag is reduced by creating oblique shock waves, but the airfoil configuration becomes more complex
Solution Approach 1:
The airfoil employs a dynamic leading edge system that can switch between multiple discrete configurations (first, second, and third positions) to generate oblique shock waves at appropriate locations. This dynamic adjustability allows the system to minimize wave drag through controlled shock wave positioning while managing configuration complexity through discrete, identifiable states rather than continuous complex geometries.
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 achieves up to 14.7% reduction in drag compared to fixed geometry airfoils, enhancing aircraft range, fuel efficiency, and allowing higher speeds while minimizing wave drag and stability issues.
Implementation Method 1
The shape of the airfoil causes supersonic flow on the forward portion of the upper surface of the airfoil and generates a strong shock wave on the upper surface of the airfoil
Implementation Method 2
moving the leading edge to the second position generates a shock wave near to the leading edge of the airfoil
Data Source
AI summary
A disclosed method reduces a wave drag on an airfoil traveling at a speed. At least a portion of the airfoil is configured to be selectively moveable between a first position and a second position. The first position is a neutral position, and the second position generates a shock wave near to the leading edge of the airfoil. The method includes the steps of maintaining the airfoil in the first position when the speed is less than a first limit and moving the airfoil to the second position when the speed is greater than a first limit.