Active Flow Control System for Simple-hinged Flaps

Mechanical and Fluid Systems
Active Flow Control System for Simple-hinged Flaps (LAR-TOPS-340)
Less cruise drag, better fuel economy
Overview
Conventional high-lift systems allow transport aircraft to safely operate at low speeds for landing and takeoff. These high-lift devices, such as Fowler flaps, are complex, heavy, and have high part counts. Fowler flap mechanisms also protrude externally under the wings, requiring external fairings, which increase cruise drag. Simple-hinged flaps are less complex, and an ideal choice for low-drag cruise efficiency. However, simple-hinged flaps require high flap deflections to achieve lift comparable to Fowler flaps. These flap deflections cause severe adverse pressure gradients, which generate flow separation that is difficult to control. In response to these challenges, NASA developed the High Efficiency Low Power (HELP) active flow control (AFC) system. This simple, elegant invention can control flow separation resulting from the high flap deflections required by simple-hinged flap systems – making such flaps a viable option for aircraft designers. Aircraft with simple-hinged flap systems will achieve reduced cruise drag, thereby increased fuel efficiency.

The Technology
Although simple-hinged flaps represent optimal high-lift systems for reducing cruise drag, previous attempts to design flow control systems enabling such technology in transport aircraft have been unsuccessful. This is largely because such systems generally require a tradeoff between (a) the ability to achieve the required lift performance, and (b) possessing sufficiently low pneumatic power to enable feasible aircraft system integration (i.e., avoiding excess weight penalties associated with high pneumatic power). For example, electrically powered AFC systems (e.g., plasma actuators, synthetic jet actuators) have practical power requirements, but with limited control authority, making such systems ineffective for highly deflected flaps. On the other hand, circulation control systems can provide necessary lift for airfoils or wings with high flap deflections, but require too much pneumatic power for aircraft integration. NASA’s HELP AFC system represents a breakthrough in flow separation control technology – to efficiently achieve necessary lift performances while requiring low pneumatic power relative to alternative flow control techniques. NASA’s HELP AFC system uses a unique two-row actuator approach comprised of upstream sweeping jet (SWJ) actuators and downstream discrete jets, which share the same air supply plenum. The upstream (row 1) SWJ actuators provide good spanwise flow-control coverage with relatively mass flow, effectively pre-conditioning the boundary layer such that the downstream (row 2) discrete jets achieve better flow control authority. The two row actuator system, working together, produce a total aerodynamic lift greater than the sum of each row acting individually. The result is a system that generates sufficient lift performance for simple-hinged flaps with pneumatic power requirements low enough to enable aircraft integration.
HELP actuator cartridges on the NASA High-Lift Common Research Model (CRM-HL). Testing proved that HELP flow control actuators were very effective in controlling the substantial flow separation on a simple-hinged flap system with a 50 degree flap deflection.
Benefits
  • Enables use of simple-hinged flap systems in aircraft design: By attenuating strong adverse pressure gradients encountered by highly deflected simple-hinged flaps while using relatively low pneumatic power, NASA's HELP AFC system makes the use of simple-hinged flaps feasible.
  • Improved fuel efficiency: The ability to replace Fowler flaps with simple-hinged flaps eliminates the cruise-drag penalty associated with Fowler flap systems' decreasing fuel burn.
  • Low maintenance: HELP actuators do not have any moving parts, and are essentially maintenance free.
  • Reduced size and part count: NASA's HELP AFC system has the potential to decrease aircraft weight and part count by enabling simpler flap deployment operation.
  • Reduced noise: The elimination of slotted (i.e., Fowler) flaps minimizes airframe noise.

Applications
  • Aerospace: Simple-hinged control surfaces (e.g., flaps and rudders) for commercial and military aircraft
  • Marine Vessels: Simple-hinged flap control surfaces for marine vessels
  • Spacecraft: Enhancing lift for bluff bodies, such as those associated with planetary reentry vehicles
  • Urban Air Mobility (UAM): Vertical and/or short take-off and landing wings in the UAM industry
  • Engines: Flow separation and/or distortion control for compact diffusers upstream of engine inlets
Technology Details

Mechanical and Fluid Systems
LAR-TOPS-340
LAR-19615-1
11,884,381
"Comparative Study of Active Flow Control Strategies for Lift Enhancement of a Simplified High-Lift Configuration" Veer N. Vatsa, Benjamin Duda, John C. Lin, Latunia P. Melton, David P. Lockard, Matthew O’Connell, & Judith A. Hannon , 06/14/2019,
https://ntrs.nasa.gov/api/citations/20200002623/downloads/20200002623.pdf

"Wind Tunnel Testing of Active Flow Control on High-Lift Common Research Model" John C. Lin, Latunia P. Melton, Judith A. Hannon, Marlyn Y. Andino, Mehti Koklu, Keith B. Paschal, & Veer N. Vatsa, 06/14/2019,
https://ntrs.nasa.gov/api/citations/20200002632/downloads/20200002632.pdf

"Testing of High-Lift Common Research Model with Integrated Active Flow Control" John C. Lin, Latunia P. Melton, Judith A. Hannon, Marlyn Y. Andino, Mehti Koklu, Keith B. Paschal, & Veer N. Vatsa, 08/25/2020,
https://arc.aiaa.org/doi/10.2514/1.C035906
Similar Results
Wing shaping Control with Variable Camber
Green aviation - improved aerodynamic efficiency and less fuel burn
Currently, as fuel is burned, wing loading is reduced, thereby causing the wing shape to bend and twist. This wing-shape change causes the wings to be less aerodynamically efficient. This problem can be further exacerbated by modern high-aspect flexible wing design. Aircraft designers typically address the fuel efficiency goal by reducing aircraft weights, improving propulsion efficiency, and/or improving the aerodynamics of aircraft wings passively. In so doing, the potential drag penalty due to changes in the wing shapes still exists at off-design conditions. The unique or novel features of the new concepts are: 1. Variable camber flap provides the same lift capability for lower drag as compared to a conventional flap. The variable camber trailing edge flap (or leading edge slat) comprises multiple chord-wise segments (three or more) to form a cambered flap surface, and multiple span-wise segments to form a continuous trailing edge (or leading edge) curve with no gaps which could be prescribed by a mathematical function or the equivalent with boundary conditions enforced at the end points to minimize tip vortices 2. Continuous trailing edge flap (or leading edge slat) provides a continuously curved trailing edge (or leading edge) with no gaps to minimize vortices that can lead to an increase in drag. 3. The active wing-shaping control method utilizes the novel flap (or slat) concept described herein to change a wing shape to improve aerodynamic efficiency by optimizing span-wise aerodynamics. 4. An aeroelastic wing shaping method for analyzing wing deflection shape under aerodynamic loading is used in a wing-control algorithm to compute a desired command for the flap-actuation system to drive the present flap (or slat) system to the correct position for wing shaping.
Lift cruise configuration AAM design
Active Turbulence Suppression System for Electric Vertical Take-Off and Landing (eVTOL) vehicles
The Active Turbulence Suppression (ATS) system for electric Vertical Take-Off and Landing (eVTOL) vehicles employ existing lifting propellers to dampen instabilities during flight, such as Dutch-roll oscillations and other gust-induced oscillations. When a roll angle of an eVTOL aircraft has deviated or is about to deviate from a current stable aircraft state to an undesirable, unstable, and oscillating aircraft state, the ATS system queries a turbulence suppression database that stores a set of propeller speed profiles for mitigation a deviation of a given roll angle for a particular aircraft with specified propellers. Using this data, the eVTOL flight controller adjusts the speed of the propellers for a certain duration of time, according to the propeller speed profiles for mitigating the deviation. In models of aircraft with adjustable propeller angles, the database includes blade angle profiles for mitigating the effects of turbulent conditions. Timing and rate of propeller activation can be pre-computed using higher order computational modeling performed with NASA’s super computing resources. Because the data is pre-computed, the use of the ATS system onboard does not require significant computing resources to implement on eVTOL vehicles. The technology, a mechanism by which existing eVTOL propellers are leveraged to suppress gust-induced oscillations enables a safe and comfortable passenger experience at low-cost and without added hardware.
PRANDTL in flight
New Wing Design Exponentially Increases Total Aircraft Efficiency
Adverse yaw, present in current aircraft design, is the adverse horizontal movement around a vertical axis of an aircraft; the yaw opposes the direction of a turn. As an aircraft turns, differential drag of the left and right wings while banking contributes to aircraft yaw. Proverse yaw—yawing in the same direction as a turn—would optimize aircraft performance. Initial results from flight experiments at Armstrong demonstrated that this wing design unequivocally established proverse yaw. This wing design further reduces drag due to lift at the same time. How It Works The Armstrong team (supported by a large contingent of NASA Aeronautics Academy interns) built upon the 1933 research of the German engineer Ludwig Prandtl to design and validate a scale model of a non-elliptical loaded wing that reduces drag and increases efficiency. The key to the innovation is reducing the drag of the wing through use of an alternative bell-shaped spanload, as opposed to the conventional elliptical spanload. To achieve the bell spanload, designers used a sharply tapered wing, with 12 percent less wing area than the comparable elliptical spanload wing. The new wing has 22 percent more span and 11 percent less area, resulting in an immediate 12 percent drag reduction. Furthermore, using twist to achieve the bell spanload produces induced thrust at the wing tips, and this forward thrust increases when lift is increased at the wingtips for roll control. The result is that the aircraft rolls and yaws in the same direction as a turn, eliminating the need for a vertical tail. When combined with a blended-wing body, this approach maximizes aerodynamic performance, minimizes weight, and optimizes flight control. Why It Is Better Conventional aircraft make use of elliptical loaded wings to minimize drag. However, achieving aircraft stability and control in conventional elliptical wings produces a strong adverse yaw component in roll control (i.e., the aircraft will yaw the opposite direction with application of roll control). Therefore, a vertical tail or some other method of direct yaw control is required, such as split elevons for use as drag rudders. The use of elliptical wings also results in a suboptimal amount of structure to carry the integrated wing bending moment. Adopting the bell-shaped spanload change results in an immediate 12 percent drag reduction. In addition, optimization of the overall aircraft configuration is projected to achieve additional significant overall performance increases.
Low Separation Force Quick Disconnect Device
The Low Separation Force Quick Disconnect device uses an innovative seal arrangement and flow path to eliminate separation force from line pressure. A radial design ensures a low separation force regardless of line pressure. Ten holes around the internal seal cancel loads due to balanced pressure; thus, the central force exerted on the device is due to the springs fixed internally. The device also provides for additional optional characteristics including a self-aligning feature from a compliant mount and a self-sealing mechanism that keeps dust out of the device. The Low Separation Force Quick Disconnect device is designed to transport pneumatics and cryogenic fluid. Due to the low separation force and overall design, the system requires less heavy and high-strength support structures than conventional designs; the design permits lighter retention systems and reduces deflection variations. Aerospace specific uses of the invention include flight-to-ground, flight-to-flight and surface-system applications. Other uses of the invention include any mechanism in which fluid is being transferred from ground to a vehicle or another system, especially where a high line pressure is used.
Passenger Airplane
Real-Time Drag Opti-mization Control Framework
According to the International Air Transport Association statistics, the annual fuel cost for the global airline industry is estimated to be about $140 billion in 2017. Therefore, fuel cost is a major cost driver for the airline industry. Advanced future transport aircraft will likely employ adaptive wing technologies that enable the wings of those aircraft to adaptively reconfigure themselves in optimal shapes for improved aerodynamic efficiency throughout the flight envelope. The need for adaptive wing technologies is driven by the cost of fuel consumption in commercial aviation. NASA Ames has developed a novel way to address aerodynamic inefficiencies experienced during aircraft operation. The real-time drag optimization control method uses an on-board, real-time sensor data gathered from the aircraft conditions and performance during flight (such as engine thrust or wing deflection). The sensor data are inputted into an on-board model estimation and drag optimization system which estimates the aerodynamic model and calculates the optimal settings of the flight control surfaces. As the wings deflect during flight, this technology uses an iterative approach whereby the system continuously updates the optimal solution for the flight control surfaces and iteratively optimizes the wing shape to reduce drag continuously during flight. The new control system for the flight control surfaces can be integrated into an existing flight control system. This new technology can be used on passenger aircraft, cargo aircraft, or high performance supersonic jets to optimize drag, improve aerodynamic efficiency, and increase fuel efficiency during flight. In addition, it does not require a specific aircraft math model which means it does not require customization for different aircraft designs. The system promises both economic and environmental benefits to the aviation industry as less fuel is burned.
Stay up to date, follow NASA's Technology Transfer Program on:
facebook twitter linkedin youtube
Facebook Logo Twitter Logo Linkedin Logo Youtube Logo