What turned out to be a big week for Boeing with the formal launch of its new 777X widebody also promises to be a big week for the engine that will power it, the GE9X. Dubai Airshow visitors can get a sneak preview of the 102,000-pound thrust turbofan through a new 3-D representation of the equipment at the GE Aviation exhibit (Chalet A9).
According to the U.S. manufacturer, its extensive technical maturation process is progressing well ahead of the start of the full-blown engine development cycle, which is set to being in mid-2015. The initial program has involved full-scale rig tests with fan testing and will include the running of a full core engine and a variety of low-pressure turbine demonstration tests. “We are trying to substantiate the performance of the module, including its aerodynamic performance and the new materials we’ve used for it,” explained GE90 program manager Bill Millhaem.
A big part of the maturation process is to run a series of “trade studies” that consider various trade offs involved in choices made between various new materials. These include new carbon fibers and resins, as well as an improved metal leading edge to allow for a thinner fan blade.
The 9X has just 16 fan blades (compared with 22 blades on the original GE90) and these are stronger and thinner than their predecessors, delivering improved aerodynamics. Millhaem told AIN that GE has run tests of the new fan blades but with them sized up to the dimensions of the GEnX turbofan so that it can run tests to benchmark the blades’s performance against the established database for these engines.
Also in the works at GE is a new universal propulsion system rig at Boeing’s facility in Seattle, where it will run a scaled version of the 9X with fan blades, nacelles and outlet guide vanes. Engineers will take the results of both of these tests and use the data to build the full-size 9X, after which it will verify the design of the fan blades before doing some inlet testing and a blade-out test.
Meanwhile, similar technical maturation work is being done on both the 9X compressor and combustor. A compressor demonstrator unit has been installed at GE’s facility in Massa, Italy, where it has conducted initial runs to evaluate the performance of the 11-stage, 27:1 pressure ratio unit. “The initial data looks very good and we will now do the design iteration of the compressor based on what we’ve seen and we’ll run a demonstration core in 2015 to substantiate the engine size and what the core will look like,” Millhaem explained.
For the combustor, GE engineers are working on evaluations of design concepts for the fuel nozzle. This will be based on the combustion system of the existing GEnX, and Leap narrowbody engines, but will operate at higher pressure and temperatures.
Using 3-D printing techniques to make early iterations of the fuel nozzles, GE is saving a lot of time because it can quickly incorporate design changes and test these with a new version. Later this year or early in 2014, the 9X team will start low-pressure tests. The company is building a new facility in Cincinnati to allow combustor tests to be conducted across the full pressure range.
The 9X is due to begin full ground tests in 2016, followed by flight trials starting in 2017. When it completes certification in 2018, the turbofan is expected to deliver a 10-percent reduction in fuel burn compared with the GE90-115B and a 5-percent improvement in specific fuel consumption compared with rival widebody engines available around 2020.
“We have a lot to do but technologies are maturing as we would hope and we don’t see any roadblocks to delivering the engine on time,” concluded Millhaem.