GE Aviation will shortly begin running a test engine equipped with a number of advanced-technology components that will feature on the GE9X powerplant destined for the Boeing 777X.
The parts include combustor liners, high-pressure turbine shrouds and nozzles made from ceramic matrix composite (CMC), next-generation high-pressure turbine blades, and titanium-aluminide low-pressure turbine blades produced via additive layer manufacturing (ALM).
Set to get under way in the coming weeks at GE's facility in Peebles, Ohio, the trials will be conducted using a GEnx test engine fitted with the new parts.
Although the manufacturer has already performed extensive tests of the components separately, this will be the first time it has brought them together in a full-scale surrogate engine.
The CMC components are around 25% lighter than their metallic equivalents, says Matt Szolwinski, head of the GE9X programme, and are additionally able to withstand much higher temperatures without the need for cooling.
"It's all about using less cooling flow and running at a higher temperature. You don't need to take all this really expensive air and use it to cool parts."
GE is already utilising CMCs for the high-pressure turbine shroud on the CFM International Leap engines it produces in partnership with Snecma, but the GE9X dramatically expands their deployment.
Tests were carried out on the combustor liner in the autumn of 2014, says Szolwinski. "We could not tickle it hard enough. Let's say we demonstrated margin."
The design of the GE9X's high-pressure turbine blades also build on GE's contribution to the Leap powerplant. Those used on the narrowbody engine are the first iteration of next-generation blades which feature a more complex internal structure than the "serpentine" cooling channels currently employed. For the GE9X, however, GE will further evolve the design, taking what Szolwinski calls "another step forward".
GE also intends to expand the use of ALM-produced parts on the GE9X. Although the GEnx test engine at Peebles is only installed with the 3D-printed blades on the seventh stage of the low-pressure turbine, they will be used on the two final stages of the production model.
In addition, the manufacturer is investigating the possibility of using ALM swirlers in the engines, but Szolwinski stresses that no final decision has been made.
Meanwhile, tests will shortly commence on a second iteration of the compressor. These will be carried out in Massa in Italy – where GE has an oil and gas business – and "that's ready to fire up in the next week or so", he says.
Changes include refinements to some of the aerofoils to improve efficiency.
A demonstration core will also run in the autumn of 2015 at its Evendale, Cincinnati headquarters, with assembly and instrumentation of the core having commenced late last year.
In an altitude test facility, GE will "take it to cruise conditions and take it everywhere from take-off to cruise to fully characterise that compressor", says Szolwinski.
Overall, the programme is proceeding on schedule, he says. He expects design freeze in the third quarter.
Long-lead-time components such as the Snecma-built 140in (356cm) diameter composite fan case are already in production, he adds.
"We are happy with where we are right now. Because of the rigorous technology-maturation programme, we understand not only what we have in terms of technology but where we need to focus on turning those technologies into GE9x part numbers," says Szolwinski.
First flight of the 105,000lb-thrust powerplant is scheduled for 2017 aboard GE's 747-400 test aircraft. Certification should follow around a year later.