Boeing 787 Dreamliner - Mark Wagner [62]
Having evolved various new concepts for the Sonic Cruiser, many of them based around the PW4000 core and technology from its armory of military engines, Pratt & Whitney saw that the only way to meet the 7E7 goals was with an all-new engine. “We recognize what we have today will not meet Boeing’s goals,” said P&W Commercial Engine Marketing General Manager March Young.
General Electric’s GEnx development was rooted in its search for a CF6 replacement. Developed originally in the 1960s from the TF39 for the U.S. Air Force’s C-5A Galaxy, the engine gradually grew in capability from 40,000 pounds to 72,000 pounds of thrust. Although it came close to refanning the CF6 with a wide-chord fan blade design, GE’s ultimate member of the family became the CF6-80E1—one of which is pictured here undergoing maintenance at Prestwick, Scotland, in 2008. Mark Wagner
General Electric’s composite fan blade technology was first developed for the GE36 unducted fan and perfected for the GE90 before evolving yet again for the 787’s GEnx engine. Fitted with a titanium leading-edge cuff, the composite is less dense, and therefore lighter, but as strong as equivalent metallic blades. The GEnx-1B has only eighteen blades, compared to twenty-two on the GE90-115B and thirty-six on the CF6-80C2. Mark Wagner
If there was one advanced technology development program that paid constant dividends to GE it was the joint NASA-GE Energy Efficient Engine (E3). The ten-stage high-pressure compressor formed the heart of the GE90 and, with its 23:1 pressure ratio, was scaled for the GEnx. Mark Wagner
Pratt& Whitney’s PW-EXX concept wrapped a PW4000-derived, counterrotating low-pressure spool around an all-new high-pressure core. The engine had the same 112-inch-diameter fan as the PW4000 version on the 777, but had a smaller core to increase bypass ratio to about 10:1, versus 6:1 on the previous engine. The new core, based on the F119 engine developed for the supercruising Lockheed Martin F-22 Raptor, was configured with a ten-stage HP compressor and two-stage HP turbine, while specific fuel consumption was reduced by boosting overall pressure ratio to 50:1, compared to just under 43:1 for the PW4000 on the 777.
The PW-EXX’s “dual arc” wide-chord fan blades, based on the GP7200 design, were to be from hollow titanium, and were contained within an aluminum isogrid fan case. The case also supported integrated fan exit guide vanes, which doubled as struts. The four-stage LP compressor rotated on a special frangible support that was designed to allow the fan stage to mechanically detach in case of a major failure. Other distinguishing features of the EXX included integrally bladed rotors in the compressor, the low-emissions Talon X combustor, axially leaned airfoils in the seven-stage low-pressure turbine, and “super-cooled” high-pressure turbine blades.
Rolls-Royce’s proposal was the RB262, a three-shaft design evolved from its RB211 heritage and based around a scaled and improved version of its Trent 900, developed for the A380. The engine also incorporated technology from the company’s Vision 10 research program, which encompassed the affordable near-term low-emissions (ANTLE) demonstrator engine. To cut noise and fuel burn, the new powerplant also was designed with a higher bypass ratio, provisionally set between 10.5:1 and 11.1, making it the largest ever developed by Rolls-Royce.
The U.K. company also planned to take maximum advantage of Boeing’s goal of having a “no bleed” systems architecture. “By not taking the bleed off the core of the engine, it allows us to change the matching of the HP and LP compressors, and we are now almost certain to make the IP [intermediate compressor] contrarotating,” said Rolls-Royce Director of Engineering and Technology Mike Howse. This was a departure from the Trent 900, which had been the first contrarotating Trent engine, but which rotated the HP in the opposite direction to the LP and IP systems. The principle was still the same, and essentially improved