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New tests move P&W closer to ultra-high bypass GTF

Pratt & Whitney is a step closer to developing an ultra high-bypass version of the PW1000G geared turbofan after completing a second round of ground testing of key components.

Increasing the ratio of airflow that bypasses the engine core is one of the tools that engine designers use to improve fuel efficiency. The PW1100G entered service with the Airbus A320neo family with a 12.2:1 bypass ratio, which doubled the amount of air bypassing the engine core compared to the CFM International CFM56 engine.

P&W is now working on the design of the next generation geared turbofan engine with a bypass ratio that the company describes as “significantly higher” than the 12.2:1 ratio in the PW1100G.

More than 175h of ground testing were recently completed on GTF propulsory technology — namely, the ultra high-bypass ratio fan, inlet and part of the nacelle, GTF says. The demonstrator engine used a shorter duct inlet than the current generation engine and “significantly fewer” lower-pressure ratio fan blades. The PW1100G todays uses 20 fan blades.

P&W has not released details for the bypass ratio used in the tests or the precise number of fan blades installed on the demonstrator.

The next-generation geared turbofan is being developed as Boeing considers engine suppliers for a proposed New Mid-Sized Airplane, which is scheduled to enter service in the mid-2020s. The same technology also could attract interest from Airbus as it considers a response to the NMA, if Boeing decides to launch the programme next year. It would compete against a higher-thrust version of the CFM International Leap-1 engine and the Rolls-Royce UltraFan concept.

"The success of this ground test is an important step in taking our geared turbofan engine technology to the next level," Alan Epstein, P&W’s vice-president of technology and environment, says in a news release.

Since the PW1100G entered service on the A320neo in January 2016, durability problems with key components have plagued operators and shortages of key parts have stymied P&W’s production ramp-up. But the engine’s operators have unanimously praised the fuel efficiency of the first-generation geared turbofan, which features a reduction gear that allowed P&W to increase the size and lower the rotation speed of the inlet fan. Both improvements are required to increase the bypass ratio to 12.2:1.

The recent tests come two years after P&W completed a 275h round of testing on a fan rig for the ultra high bypass ratio fan and five years after completing wind tunnel tests on an earlier version of the fan.

Both series of tests were sponsored under the first phase of the US Federal Aviation Administration’s continuous lower emissions, energy and noise (CLEEN) programme. P&W launched development of the new engine in 2010 with the goal of designing an engine that could improve single-aisle aircraft fuel consumption by 20% compared to a CFM56-7 and reduce noise by 25dB relative to the FAA’s Stage 4 noise regulations.

More rig testing will continue under the second phase of the CLEEN programme, P&W says. The goal is validate the technologies developed under CLEEN in a flight test campaign, the company says.

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