GE (General Electric) has already started, a few months ago, tests on the GE9X engine for its certification, which is scheduled for 2018. This engine stands out for being the largest turbofan in the world ever created, despite its power being smaller when compared to the brother GE90-115, the lower power is enough to move the brand new 777X, which Boeing will debut in 2019, since this aircraft has several points to reduce its weight.
The fact is that GE set up a new program to develop this engine in 2013, after a request from Boeing, which launched the 777X in the same year. This is an unusual situation for the company, most engines are developed within 8 to 12 years, but GE has only 6 years to design, build and certify the company's new invention.
first engine
The first unit of the engine was tested 13 months ago in Peebles, Ohio, the second unit soon after entered the testing program on May 16th. The first engine was responsible for informing the engineers of complete data and also its aerodynamic performance. “FETT (name of the 1st engine) was to make sure the architecture really came together,” said GE's Chuck Jackson.
In October 2016, GE completed the second phase of testing CMC (Ceramic Matrix Composite) components on a GEnx demonstration engine, accumulating 1800 cycles, exposing the engine to severe environmental conditions of dust and debris. The level of debris exposure was equivalent to about 3000 takeoff and landing operating cycles. For the second round of testing, the GEnx demo engine utilized the same CMC combustion chamber liners, stage 1 HPT liners, and stage 2 HPT nozzles that were in the first round of testing in September 2015, along with the addition of the HPT phase 1 nozzles made in CMC.
CMC is significantly lighter, stronger and more heat resistant than the metal components they replace, plus it saves weight and allows the engine to run more efficiently and warmer. CMC consists of silicon carbide ceramic fibers and ceramic matrix, they are reinforced with coatings made exclusively for these parts. With one-third the density of metal alloys, this CMC reduces engine weight, which improves fuel efficiency and durability.
The first engine underwent winter cold weather testing as well as high altitude testing. To prevent problems from occurring in cold weather, GE carried out more than 50 batteries of tests on the GE9X, which were mainly related to the formation of ice crust in the engines, there were 168 hours of tests and 162 cycles in this process. In total, the engine has already performed 335 hours of tests and 375 cycles so far, it was left aside after GE defined the final characteristics, although it remains assembled for possible tests.
With this arduous step, GE is confident that the GE9X will not have problems with PTO freezing, thanks to the learnings with the GEnx and GE90. Additional tests will take place at high altitude, with thin air and lower pressure, to that the data obtained on the ground are consistent with the tests in flight.
Second engine, changes and certification
The second engine is also nominated as the first engine for the certification program, and known within the company as “test engine GE9X 002/1″, while the first engine was responsible for stating that the GE project was as expected by the company, the second engine (SETT) had the final characteristics, which can be changed minimally, according to the ground tests.
The SETT engine means a small evolution for GE from the FETT, some minimal features were changed by the company, mostly to achieve GE's efficiency goals for the 9X. GE has made changes in the area between high pressure turbine and low pressure turbine, both located right after the engine's combustion chamber.
The company reports that the performance of this area of the engine affects everything else, such as the compressor, the turbine and the huge front fan, since the turbine is responsible for keeping the engine shaft in action, taking advantage of the energy of the gases of the burning of the combustion chamber.
Other areas of the engine also underwent modifications, such as the high-pressure compressor, which is located near the combustion chamber, and also affects the way air is delivered to that location, and consequently its burning. The compressor has a compression ratio of 27:1 and 11 stages, this ratio is, for example, much higher than that found in most cars.
With these changes, GE started this week, on May 16, the GE9X certification process, which should be completed by 2018. From that point on, the company has approximately 1 year and a half to put the engine in full operation.
To be certified, engines must continue to operate in weather and operating conditions that exceed anything they may encounter in actual service (e.g., hail and ice storms, winds at nearly 160 km/h, bird attack, ice).
At the same time that the second GE9X engine begins testing, assembly of the third and fourth GE9X engines will be underway at GE Aviation headquarters in Evendale, Ohio. The fourth GE9X engine is scheduled for flight testing, installed on GE's Boeing 747-400, which is located at GE's Mojave Desert facility in Victorville, CA, before the end of this year.
There will be eight engines in total for the GE9X certification process, which also includes ETOPS operations, essential for the 777X that will be able to fly for hours above the Pacific without needing to refuel. These engines also include Boeing units for the four 777-9X test planes, which the manufacturer will present in 2019.
GE9X and 777X
The GE9X should be able to offer a thrust of 105 pounds, this value is slightly lower when compared to the GE90-115B, which has 115 pounds of thrust. However, GE's new engine can be up to 15% more efficient when compared to its older brother.
Among the standout features of the new engine is the front fan, made with a new generation of composite materials, a new TAPS III combustion chamber, better than that used in GEnx engines, and CMC materials in the turbine and combustion area.
GE has 700 orders for GE9X engines, not counting spare units for maintenance.
Video – The GE9X
Video – Some tests of the GE9X (FETT)
Video – Ice formation test
Via - Aviation Week e GE Aviation
