NASA testing new boundary layer ingesting (BLI) propulsor; 4-8% fuel burn savings over current advanced engines
12 December 2016
Engineers at NASA Glenn are testing a new boundary layer ingesting (BLI) inlet-fan combination—the first of its kind ever to be tested. Originally conceived of as a propulsion system for generation-after-next (N+2), the BLI system could increase fuel efficiency by 4-8% more than the advanced engines airlines are beginning to use.
On today’s jet aircraft, the engines are typically located away from the aircraft’s body to avoid ingesting the layer of slower flowing air that develops along the aircraft’s surfaces, called boundary layer. Aerospace engineers believe they can reduce fuel burn by embedding an aircraft’s engines into these surfaces and ingesting the boundary layer air flow to propel the aircraft through its mission.
MIT and NASA engineers earlier proposed the D8 Series as one future aircraft design concept that uses boundary layer ingestion. Projected as a replacement for the Airbus A320/Boeing 737 around 2035 (N+3 generation)—the D8 could deliver fuel burn more than 70% lower than the 737-800—assuming the BLI propulsor is feasible.
Studies backed by more detailed analyses have shown that boundary layer ingesting propulsors have the potential to significantly improve aircraft fuel efficiency. If this new design and its enabling technologies can be made to work, the BLI propulsor will produce the required thrust with less propulsive power input. Additional aircraft drag and weight reduction benefits have also been identified.
—David Arend, a BLI propulsion expert at NASA Glenn
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| Source: Hall (2016). Click to enlarge. |
NASA is testing the propulsor, designed by United Technologies Research Center with research conducted by Virginia Polytechnic and State University, in its 8' x 6' Wind Tunnel at NASA Glenn in Cleveland, Ohio. The highly experimental tests have required years of preparation. Many industry, NASA and academic experts contributed to the design and analysis of the propulsor. NASA Glenn engineers also modified the wind tunnel to accept a larger model, a boundary layer control system and a way to power the experiment.
We have generated a unique test capability that doesn’t exist anywhere in the country for testing boundary layer ingesting propulsors.
—Jim Heidmann, manager of NASA’s Advanced Air Transport Technologies project
One of the key challenges facing BLI propulsors, noted Arend and his colleagues in a 2012 paper, is the ability of the turbomachinery to operate efficiently in highly distorted flow. In particular, a high-performance, distortion-tolerant fan will be required.
Throughout testing, the team will change the wind speed and vary the boundary layer thickness and fan operation to see how these changes affect the propulsor’s performance, operability and structure. Results of the tests will be applicable to multiple cutting-edge aircraft designs being pursued by NASA as well as by its academic and private industry partners.
Resources
Larry W. Hardin, Gregory Tillman, Om P. Sharma, Jeffrey Berton and David J. Arend (2012) “Aircraft System Study of Boundary Layer Ingesting Propulsion” 48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit
< Shishir A. Pandya (2015) “Preliminary Assessment of the Boundary Layer Ingestion Benefit for the D8 Aircraft” Applied Modeling & Simulation Seminar Series
David K. Hall (2016) “Boundary Layer Ingestion Propulsion – Benefit, Challenges, and Opportunities” 5th UTIAS International Workshop on Aviation and Climate Change
These are traditional fuselage wing models. When does the length of the fuselage become a factor where the BLI can no longer benefit or correct reduced/disturbed air flow toward the Nose and leading part of the aircraft? Do away with the fuselage and go Flying wing employing in wing mounted engines.
What about a new concept where the fuselage surface has small openings where jet exhaust over pressure can be directed backwards to help mitigate the negative affects of disturbed viscous air flow along the surface? Modeling problem.
Posted by: Dr. Strange Love | 12 December 2016 at 06:58 AM
The longer the fuselage, the better. The thicker the fuselage, the better. Because both produce greater boundary layer
Airbus designed the theoretical battery driven plane, VoltAir, with a thick fuselage and counter-rotating ducted propellers ingesting the fuselage boundary layer.
A wide body also enables body-mounted landing gear and thus a very clean wing without protuberances or their ensuing drag.
Bonus info about the VoltAir aircraft: It would employ theoretical, future Li-Air batteries - replaceable - with an energy density of 1000 Wh/kg, and high-temperature superconducting e-motors cooled by liquid nitrogen.
Posted by: Thomas Pedersen | 13 December 2016 at 05:11 AM
Thomas P. Now that is futuristic. So a fuselage has advantages.
Posted by: Dr. Strange Love | 13 December 2016 at 04:55 PM