It’s another torrid summer day in Italy and an extra-long truck approaches the gates of the Avio Aero plant in Pomigliano d’Arco, a few kilometers north of Naples, carrying an oversized load weighing about five tons—a GEnx-1B engine. This particular engine began its journey on a cargo flight from Chicago destined for the largest test cell in Italy. This Neapolitan facility, among the five largest in Europe, can accommodate and test a variety of powerplants, including the GEnx, LEAP, Passport 20 and CFM56.
The GEnx-1B engine powers all models of the Boeing 787 Dreamliner, a new generation twin-aisle aircraft. Although designed for long-haul flights, the 787 with GEnx engines has proved to be a versatile asset, capable of flying routes as short as 25 minutes and as long as 17.5 hours. When this GEnx-1B arrived in Pomigliano, it was entrusted to Francesco Gaudino, the Test Engineering and Test Cell manager, to undergo a highly demanding test campaign never carried out before in Italy.
“It has been our team, with about 12 people directly involved, that undertook the sand ingestion tests working side-by-side with GE Aviation’s Central Engineering in Ohio and also with the European and U.S. research and development centers—such as the EDC in Warsaw and the GRC in Niskayuna, New York,” said Gaudino. “This campaign generated an amount of data and results that we will share and analyze with our colleagues in order to offer solutions that improve engine performance under extreme conditions.”
These tests commenced at the end of last summer; to date they have recorded more than 400 hours of activity focused almost exclusively on sand ingestion. In a typical test, the engine is run at different speeds (taxi, take-off, cruising and landing) and at maximum power while being subjected to “sandstorms” of increasing intensity in the Pomigliano test cell.
Each test follows a well-defined process that requires unpacking and positioning in the preparation and configuration room right next to the test cell. The cell ceiling is 12 meters high and the interior is equipped with systems that allow it to faithfully simulate the use of the engine. The control room is filled with computer screens and a large window gives the staff a profile view of the engine being tested. Inside the cell, a long exhaust tunnel tapers off into the dark to the rear of the engine.
During the sand ingestion test a special metal structure equipped with several small nozzles in a fascinating geometric design is set up in front of the fan. The sand is shot from here, at different levels of intensity, directly into the front fan of the engine so that the sand passes lengthwise through the entire interior and penetrates any exposed components.
“These tests are specifically conducted for operators and our direct customers who use their aircraft in areas of the world that we technically call ‘Severe Operating Environment’ or SOE—desert areas, such as Africa and the Middle East, or regions affected by certain environmental phenomena that spread sand or dust,” says Shawn Pearson, GEnx Engineering Leader. “Sand can degrade the cooling muscle in our hot section components—like combustors but also turbines—and create distress in protective coatings, accelerating hardware damage and leading to early engine removals. This test is critical to understand the capability of our engines in SOE, to develop and validate designs that will meet our customers’ expectations in challenging environments.”
Sand ingestion has been a regular part of the battery of tests conducted at GE’s test cell in Peebles, Ohio, so much so that the facility has a dedicated “dust rig.”
“But on this occasion, we wanted to collaborate with the Pomigliano team to find better and better solutions for our customers in certain geographical areas,” Pearson said. “The ability to collaborate across the globe and across time zones has allowed us to execute a successful test so far and we are learning a lot, thanks to the expertise of the Pomigliano team and the support of engineers from Evendale, Peebles, Warsaw and GRC.
The work of GE teams located on three different continents generates a multitude of data, which of course offers great opportunities to learn and improve not only the design but the performance that can be achieved during specific climatic events. In certain parts of the world, even at high altitudes, the wind can carry mining dust and different types of sand at high speeds. Some of it can even be electrostatically charged.
GEnx, the engine of choice for the Dreamliner, is chock full of extremely advanced technology: composite fan blades and fan case, the highest-pressure ratio compressor of commercial engines in operation, lean-burn combustor, and low-pressure turbine made with titanium aluminide material. All of which is to say, the more extreme the environment, the more intense the test regimen.
“These are very complex, delicate test activities, but we are proud to deal with such special and important cases for our customers,” says Gaudino. “In the test cell, we meticulously control what happens in the engine. We periodically perform borescope inspections on every single component, as if we were analyzing it under a microscope to highlight the consequences of air and sand flow through the engine at high speed and temperature.”