'Smart' flaps could improve efficiency of supersonic engines

November 30, 2000

CHAMPAIGN, Ill. -- Small flaps mounted in jet-engine inlet ducts may allow supersonic aircraft to fly faster and farther at less cost, say researchers at the University of Illinois. "When flying at supersonic speeds, shock waves naturally occur in the engine inlet," said Eric Loth, a UI professor of aeronautical and astronautical engineering. "The shock waves disrupt the airflow, creating considerable flow separation and significantly reducing engine efficiency." To minimize this effect and prevent boundary-layer flow separation, conventional supersonic engines use a bleed system that removes air through holes in the inlet wall and dumps it out the back. While this keeps the boundary layer attached, it also wastes a fair portion of the ingested airflow.

"Engine efficiency can be improved by covering the holes with 'smart' flaps that bend under certain operating conditions," said Loth, the project director of a three-year development effort that includes researchers from the UI, NASA, Boeing and the U.S. Air Force.

Flaps downstream of a shock will bend downward, sucking air from the boundary layer into a cavity below, while flaps upstream of a shock will bend upwards, injecting air from the cavity back into the boundary layer, Loth said. "Recirculating the air not only prevents flow separation, it also improves the engine's efficiency, since the air is no longer being thrown away."

Thousands of flaps would line an inlet. Resembling slips of paper about one centimeter on a side, the flaps are being made from shape-memory materials such as nitinol, an alloy of nickel and titanium.

"Shape-memory alloys are materials that can 'memorize' a shape and return to it after repeated thermo-mechanical cycling," said Scott White, a UI professor of aeronautical and astronautical engineering. "We can design these smart materials to 'turn on' and open up under specific conditions of stress and temperature. Their stiffness - and therefore the amount they deflect - can be controlled."

In a series of recent experiments, White characterized the bending behavior of miniature flaps under dynamic loading conditions. He and graduate student Sridhar Krishnan monitored the static and dynamic properties of thin nitinol beams as they deflected under various transformation temperatures.

"Such an analysis is critical to the next stage of our project, where we want to place the flaps under active, closed-loop control," said White, who presented the team's findings at the national meeting of the American Society of Mechanical Engineers, held Nov. 5-10 in Orlando, Fla. "A system of smart flaps coupled with a non-linear, adaptive-feedback control system could continually adjust the material properties - and therefore the position of the flaps - for optimum engine performance."
-end-
In addition to Loth and White, the UI research team includes aeronautical and astronautical engineering professor Philippe Geubelle and mechanical and industrial engineering professors Andrew Alleyne, Craig Dutton and Dan Tortorelli. Funding for this work was provided by the Defense Advanced Research Projects Agency and the U.S. Air Force Office of Scientific Research.

University of Illinois at Urbana-Champaign

Related Efficiency Articles from Brightsurf:

Theoretically, two layers are better than one for solar-cell efficiency
Solar cells have come a long way, but inexpensive, thin film solar cells are still far behind more expensive, crystalline solar cells in efficiency.

Using physics to improve root canal efficiency
In Physics of Fluids, scientists report calculations with a model of a conical-shaped root canal inside a tooth.

Record efficiency for printed solar cells
A new study reports the highest efficiency ever recorded for full roll-to-roll printed perovskite solar cells.

New 5G switch provides 50 times more energy efficiency than currently exists
As 5G hits the market, new US Army-funded research has developed a radio-frequency switch that is more than 50 times more energy efficient than what is used today.

On the trail of organic solar cells' efficiency
Scientists at TU Dresden and Hasselt University in Belgium investigated the physical causes that limit the efficiency of novel solar cells based on organic molecular materials.

Wearable health tech gets efficiency upgrade
North Carolina State University engineers have demonstrated a flexible device that harvests the heat energy from the human body to monitor health.

Photoelectrochemical water-splitting efficiency hits 4.5%
Solar-to-fuel conversion offers a promising technology to solve energy problems, yet device performance could be limited by undesired sunlight absorption.

Green hydrogen: Research to enhance efficiency
Laboratory experiments and a parabolic flight campaign have enabled an international team of researchers from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) to gain new insights into water electrolysis, in which hydrogen is obtained from water by applying electric energy.

New efficiency world record for organic solar modules
Researchers from Nuremberg and Erlangen has set a new record for the power conversion efficiency of organic photovoltaic modules.

A new method for quantifying crystal semiconductor efficiency
Japanese scientists have found a new way to successfully detect the efficiency of crystal semiconductors.

Read More: Efficiency News and Efficiency Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.