As a five-year series of engine certification testing nears a midway point, GE Aviation has completed testing on the advanced high-pressure compressor module of the GE9X turbofan, says Bill Millhaem, general manager of the GE90/GE9X programme.
The critical HPC module for the 100,000lb-thrust engine selected to power the Boeing 777-9X has evolved slightly over 2.5 years of testing. The 27:1 compressor ratio – roughly 20% higher than the previous standard – remains unchanged, but details have changed.
A “Build 1” prototype of the HPC module revealed an opportunity to reduce the number of blades at the front end, Millhaem says. That change “increases the efficiency of the overall compressor”, he adds.
A new set of airfoils with fewer pieces was assembled for a “Build 2” prototype that entered testing earlier this year.
“We’ve run about 350h now on that to validate an improvement in the efficiency in the compressor and better [specific fuel consumption],” Millhaem says. “We’re very pleased with the results that we’ve seen.”
The data from the tests will be used to finalise the design of the HPC module. The next step for GE Aviation is to assemble and run the first GE9X core, which includes the HPC, combustor and high-pressure turbine and excludes the low-pressure spool. That testing will begin in the second half of the year.
GE is also in the process of commissioning a new, $100 million facility in Cincinnati to test the combustor. A 90-degree quarter-sector of the combustor will run in the new test chamber.
All of those tests will lead to the graduation exercise. The low-pressure section has already passed through testing in Boeing’s low-speed wind tunnel in Seattle. In the first half of 2016, GE will assemble the first low-pressure section and high-pressure section to complete the first full-scale GE9X test engine.
GE finalised the architectural design of the GE9X earlier this year, which allows the company’s engineers to proceed into detailed design reviews of the mach of the modules and components. The company’s design freeze milestone – internally designated as Toll Gate 6 – is scheduled in the fourth quarter.
“There’s still a lot of testing we’re doing this summer,” Millhaem says. “The learnings to date have all been very, very positive and we are on track to meet all our commitments to the marketplace.”
GE has announced plans to use ceramic matrix composites in turbine shrouds and combustor liners. Company officials once seemed bullish on the idea of also using the high-temperature materials in the high-pressure turbine blades, but stepped back from that approach about a year ago. As the design moves closer to configuration freeze, there will be less room for entertaining new ideas.
“I would say at this point the technologies we’re testing have bought their way on, and we’re substantiating their performance and analysis around how they will perform,” Millhaem says.
Source: Flight Daily News
