Modern military turbofan engines have two airstreams – one that passes through the core of the engine, and another that bypasses the core. The development of a third stream provides an extra source of air flow to improve propulsive efficiency and lower fuel burn, or to deliver additional air flow through the core for higher thrust and cooling air.
Utilizing a third stream of air that can be modulated to adapt the engine's performance across the flight envelope means a fighter can have the best of both worlds by accessing an on-demand increase in thrust or smoothly shift to highly efficient operations during cruise. This capability provides an optimal balance for combat scenarios requiring both high-end acceleration and increased range.
“We look forward to continuing the maturation of adaptive engine technologies in collaboration with the U.S. Air Force for the next generation of combat aircraft,” says Chris Flynn, vice president of Military Development Programs at Pratt & Whitney. “In addition to providing a seamless transition between high thrust and fuel efficiency, adaptive propulsion can enable an unprecedented range of capability growth in mission systems and heat dissipation capacity at the air vehicle level. We are committed to giving the warfighter a technological advantage.”
Last year, Pratt & Whitney successfully completed testing of an adaptive three-stream fan in an engine with an F135 core as part of the U.S. Air Force Research Laboratory (AFRL) Adaptive Engine Technology Development (AETD) program. The F135 advanced turbofan engine powers the multirole Lockheed Martin F-35 Lightning II fighter aircraft and is a derivative version of the proven F119-PW-100 engine, which powers the Lockheed Martin F-22 Raptor tactical fighter aircraft.
The goal of the AETD program was to achieve a 25 percent reduction in fuel consumption and a 10 percent improvement in thrust levels compared to modern fifth-generation combat aircraft engines.
The adaptive three-stream fan technology leverages and improves upon Pratt & Whitney's experience as the only provider of fifth-generation fighter engines – the F119 and F135, which power the F-22 and F-35, respectively. (Image source: Department of Defense)
Over the coming months, Pratt & Whitney will leverage experience from design and test activities completed during AETD efforts to ensure the AETP program refines the technologies necessary to meet future mission requirements of air superiority.
The AETP contract is now currently cumulatively valued at nearly $1.5 billion, according to the Department of Defense. The majority of the contract work will occur in East Hartford, with an expected completion date of February 28, 2022.
Along with a demand-modulated engine architecture, Pratt & Whitney is also maturing an adaptive technology suite that includes control systems as well as power and thermal management systems to enable enhanced range, persistence, survivability, and maintainability capabilities for advanced weapon systems.
William Kucinski is content editor at SAE International, Aerospace Products Group in Warrendale, PA. Previously, he worked as a writer at the NASA Safety Center in Cleveland, OH, and was responsible for writing the agency’s System Failure Case Studies. His interests include literally anything that has to do with space, past and present military aircraft, and propulsion technology.
Contact him regarding any article or collaboration ideas by e-mail at firstname.lastname@example.org.
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