(GE) is sticking to a technology test plan for the GE9X engine for the , despite continuing uncertainty over Boeing’s development timetable.
The engine maker is running a raft of technology demonstrations to support FAR33 engine certification in 2018 and entry-into-service in 2019. Boeing, which has not formally announced a firm schedule for the 777 derivative, still is believed to be aiming at introducing the aircraft by 2020.
“Even though Boeing is still figuring out what they want to do, we’re doing the technology,” saysGeneral Manager William Millhaem. “It’s the right thing to do for the industry.”
Although GE also is reluctant to give schedule details, it is expected to run the first version of a new core for the GE9X as early as 2014. A final “Toll Gate 6” decision on freezing the design likely will take place around 2015, with the first engine going to test in 2016. Given this timing, the engine would be tested on GE’s-400 flying testbed in 2017, with certification the following year.
Among several key technology maturation tests leading to the design of the new core is the planned evaluation of a 27:1 pressure ratio, high-pressure compressor design. The initial version of an 11-stage unit will be tested at GE’s Oil and Gas facility in Massa, Italy, in mid-2013, and will be the highest-pressure (HP) ratio compressor of its type yet developed for a GE commercial engine.
Testing of the advanced compressor rig will check the configuration “to look if anything unexpected happens at 27:1 and see what happens when we bleed air off and if we get the right clearances,” says Millhaem, adding that the lessons will be used to improve the baseline design before the first core is built.
The HP compressor lies at the heart of the engine and is fundamental to its overall efficiency and performance level. The advanced “E3” (Energy Efficient Engine) 19:1 compressor developed withwas key to the success of the original GE90, while the evolved HP compressor of the has a pressure ratio of 23:1.
The overall pressure ratio for the entire GE9X is similarly targeted at an extremely ambitious 60:1, compared with 50:1 for the GEnx and 40:1 for the GE90.
“With the GE9X we’re continuing that strategy, but we are reaching into the technology cupboard and pulling out new things from the 9X technology pool,” says Millhaem. As well as improved aerodynamics in the compressor and turbine, the project aims to leverage advances in materials, such as next-generation powder metal alloys and ceramic matrix composites, to help bridge the gap between the GEnx and Boeing’s performance goal for the 777X.
“If we start with a scaled GEnx-1B, we get about half-way to what Boeing is asking us to do for the 777X,” Millhaem says. The 777X is targeting fuel burn that is about 10% lower than that of the current GE90-115B-powered 777, while maintaining existing maintenance costs.
Other work is focused on a fourth-generation fan that will operate at higher speed than the current engine. “We’re also going to thinner blades, which allows us to take weight out,” Millhaem adds. Exact details about the structure of the new blade have not been finalized.