CFM International claims it is behind a revolution in the use of advanced materials for its Leap series of engines for single-aisle aircraft, that gives it a durability and maintainability edge over the competing Pratt & Whitney PurePower geared turbofan.
In a comprehensive briefing yesterday before the opening of the Paris Air Show the company gave a novel 3-D presentation of the engine and its key components, CFMI (Chalet B121 Hall 2a B252) put the case that in developing the Leap family it had emphasized the need for continuing the CFM56’s reputation for reliability and maintainability while introducing advanced materials technologies to offset the extra weight of the slightly larger engine.
For the first time in a commercial aircraft engine the GE Aviation/Snecma partnership has used ceramic matrix composites (CMCs) in a key component, the first stage of the high-pressure compressor turbine shrouds which encircle the HP blades to reduce tip leakage. “It’s the beginning of a revolution in materials design,” said Leap program manager Gareth Richards. “This technology will eventually migrate throughout the high-pressure turbine, reducing weight by a third and eliminating the need for cooling.”
GE Aviation plans to invest $27 million over the next five years on a “Lean Lab” at its Newark, Delaware CMC facility, which will allow engineering and manufacturing teams to bring CMC products to manufacturing readiness before committing to full-rate production. GE said demand for CMC components in jet engines is expected to grow tenfold over the coming decade.
Another Leap first is in the use of additive manufacturing, or three-dimensional printing, for the extremely complex TAPS combustor nozzles and the core of the stage-one HP turbine blade. In November 2012 GE Aviation completed its acquisition of Cincinnati-based Morris Technologies and sister company Rapid Quality Manufacturing, both additive manufacturing specialists. GE plans to open two new production plants in the U.S. next year.
Additive manufacturing technology involves building up layers of powdered metal, each layer melted by pinpoint lasers to the exact geometry called for by the computer-aided design process. Richards said the technology took months out of the production cycle time because it eliminated the need for assembly of a number of separate components into the finished part. The “nirvana,” he added, would be using additive manufacturing for the entire HP turbine blade, although there will be a “lot of work” ahead if the proven durability of the current single-crystal blades were to be matched. He denied there were any manufacturing or repeatability issues with the technique.
GE Aviation’s manager of advanced programs, Jeff Martin, said that the use of technologies such as CMCs and additive manufacturing in the Leap engine meant the manufacturer “didn’t need to use complex systems such as gearboxes and other tricks” to achieve similar performance levels.
With around 50 percent of the market to-date shared between them, single-aisle airline customers have so far endorsed both approaches to achieving a 15-percent fuel burn advantage over the engines currently powering single-aisle aircraft. The battle will center on reliability and maintainability, and it will be only after several years of service the answer to that will be known.