Pratt & Whitney and the US Air Force Research Laboratory (AFRL) have begun testing with an adaptive fan engine test rig that is based on the company’s F135 afterburning turbofan found on the Lockheed Martin F-35 Joint Strike Fighter.
According to P&W, the fan rig test is being conducted at the AFRL Compressor Research Facility in Dayton, Ohio, in tandem with the USAF’s Adaptive Engine Technology Demonstration (AETD) programme, the US Navy Fuel Burn Reduction (FBR) programme and other company-funded efforts.
“Developing an effective adaptive fan concept is a critical step in advancing technology that will ensure next generation air dominance for our military,” says Jack Hoying, the AFRL’s programme manager for the AETD effort.
Next-generation adaptive fan engines will allow a fighter-sized afterburning turbofan to alter its bypass ratio for different phases of flight by using a third stream of air. For low speeds below about Mach 0.85, the third air stream will be used to increase the engine’s bypass ratio and boost its propulsive efficiency.
However, at transonic and supersonic speeds where high specific thrust is needed, that third stream will run through the core and increase the jet velocity of the exhaust. The third airstream can also be used for cooling the engine during especially demanding operations.
“We’re building on our foundation of proven fifth generation capabilities, and we are now mastering adaptive technologies – really expanding the boundaries of state of the art engine technology critical for the next sixth-generation aircraft,” says Bennett Croswell, president of P&W military engines.
The results of the P&W adaptive fan rig tests will flow into the AETD programme, which has a stated goal of improving fuel consumption by 25% while providing a 10% increase in thrust compared with current fifth-generation fighter engines such as the F135. The navy’s FBR programme hopes to deliver a better than 5% fuel burn reduction on an F135 demonstration engine.
The jointly USAF and USN-funded adaptive fan test effort was launched in late 2011, with testing of the adaptive fan concept taking place from August through September 2013, according to P&W.