Geared Turbofan to Shoulder Pratt’s JT8D Legacy
Pratt & Whitney’s efforts to ensure it takes pole position in the next generation of medium-sized powerplants are materializing, with several major technology programs under way aimed at ensuring its geared turbofan (GTF) demonstrator beats the competition.
Besides the geared fan itself, the GTF will feature P&W’s Talon X (Technology for Advanced Low NOx) combustor, an early version of which is already in service on the PW4000 100-inch engine. Under development with NASA, the combustor is designed around a rich-burn/quick-burn/lean-burn concept and is yielding dramatic reductions in emissions.
The combustor features an initial rich-burning combustion zone that is quenched with dilution air to produce a second lean-burning combustion zone. The rich-burning zone minimizes instability and flameout, while the lean-burning zone significantly reduces NOx emissions. Advanced fuel air atomizers and metallic liners with an advanced cooling system contribute to reducing NOx emissions during the landing and takeoff cycle, as well as during high-altitude cruising, without increasing other pollutants.
P&W has also launched a technology readiness program with Germany’s MTU to develop a new generation of high-pressure compressors for the GTF and advanced military applications. Ground rig tests of the eight-stage, 17:1 pressure ratio compressor are set for the second half of 2006. It will incorporate integrally bladed rotors in which the compressor blades are part of the compressor disk, reducing weight and increasing strength and durability, says P&W.
Overall, the GTF is expected to reduce fuel burn by up to 12 percent over the most modern engines in service today and reduce noise levels by 18 decibels as well as reducing maintenance costs by requiring fewer parts. Testing of the GTF demonstrator is set to begin in 2007 with flight tests the following year.