Icing for testing larger engines

Citation

(2007), "Icing for testing larger engines", Aircraft Engineering and Aerospace Technology, Vol. 79 No. 6. https://doi.org/10.1108/aeat.2007.12779faf.004

Icing for testing larger engines

Icing for testing larger engines

A new facility for conducting icing certification tests on large engines has, almost overnight, sprung out of the ground at the end of Montreal's Mirabel International Airport runway. Last September, the runway ended in a flat piece of concrete. Five months later, it sported a wind tunnel 75ft long and 25ft in diameter, complete with spray system and engine stand. The tunnel was built to test the GEnx, a 70,000lb thrust engine that GE Aviation is developing for Boeing's 787 Dreamliner.

NRC Aerospace and GE Aviation erected the Mirabel facility, in partnership with Aeroports de Montreal, because NEC's engine test cells in Ottawa were not large enough to handle the GEnx. NRC engine testing expert, Jim MacLeod, stated, “This is a whole new engine for GE and significantly larger than the biggest we'd ever tested, which was 20,000lb. This was four times that.”

Mirabel was selected because of its wide, open spaces and existing concrete pads, office and assembly areas. Its location as a major transportation hub also facilitated moving parts in and out, and its proximity to Ottawa allowed NRC staff to commute between the two sites.

When construction began in September, nothing existed but a flat piece of concrete. “Not only was nothing there,” MacLeod explained, “We had to dig a big hole in the ground because the runway was made with concrete slabs 20 by 25ft across and 15 inches thick, not reinforced concrete. We had to chip out four of these slabs, then dig down 28 inches so that we could pour a reinforced concrete pad thick enough, and strong enough, to withstand forces generated during even the most extreme test conditions.”

Tunnel parts were fabricated and assembled by Benoit Forest Inc., a small Quebec-based company that, declared MacLeod, did a fantastic job. “Not only were they extremely skilled at what they did, they worked like beavers,” he stated. “They just didn't stop.” Thanks to this determination, construction was completed in record time.

The facility is an outdoor, open- circuit, wind tunnel with seven 8-foot diameter fans that can push air over the engine at 3,000lb per second. Its thrust stand, rated for 85,000lb of thrust, is enough to accommodate the GEnx. To simulate flying in icing conditions, the spray mast inside the tunnel discharges very small heated water droplets, which quickly cool and freeze on impact at the engine inlet.

The engine arrived at Mirabel in early February. It underwent six weeks of testing that ended in late March with all temperature points in the test matrix being met, including the coldest and least common one, 2208C. GE plans to return next winter to test a smaller version of the engine for the 747-8 aircraft.

“The reason GE came here is that the temperature at its Ohio testing facility only experiences a limited number of cold days in which to do ice testing,” said MacLeod. “They needed help to do this and, having worked with us in the past, understand we have a lot of experience with icing as well as good credibility with the FAA. They know we can make these projects work.”

Figure 1 GEnx engine mounted on test stand at new icing facility in Mirabel

Figure 2 GEnx engine undergoing icing test

The new facility is an opportunity for NRC Aerospace. Bob Hastings, director of the NRC Aerospace Gas Turbine Laboratory, explained, “It's a very small playing field out there for people with icing experience, especially independents like us. These engines are getting too big for the altitude facilities that exist, and the power consumption requirements for the big indoor facilities are mind numbing. You just can't afford to do it anymore. We're at the right time, at the right place, with the right people. Between our own facilities in Ottawa for smaller engines, and the new Mirabel facility, we could become the icing certification centre of excellence for the world” (Figures 1 and 2).