ARCHIVED - Propulsion Wind Tunnel Gets New Icing Capabilities

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August 05, 2005— Ottawa, Ontario

What does NRC Aerospace do when a client requires icing tests on a new helicopter engine configuration and its facilities are already booked for the winter? It turns its existing propulsion wind tunnel into a state-of-the-art facility for icing certification tests on engines and their surrounding nacelles.

Full-scale wing section undergoing icing test in the NRC Propulsion Wind Tunnel.
Full-scale wing section undergoing icing test in the NRC Propulsion Wind Tunnel.

In July, 2004, Sikorsky Aircraft approached Jim MacLeod, a propulsion expert at NRC Aerospace, with a requirement for icing tests on its S-76 helicopter, which had been modified with a new Turbomeca engine. MacLeod said, "We were booked up for the year in the engine test cells but our Aerodynamics Laboratory said they could put it in their open-circuit Propulsion Wind Tunnel. While the tunnel had previously been used for aircraft de-/anti-icing fluid research, it had never been used for in-flight icing simulation, so we had to start from a clean slate." With the winter season rapidly approaching, a team of experts from the Aerodynamics Laboratory and the Propulsion Group began modifying the tunnel in September and added a new icing capability. The Sikorsky/ Turbomeca tests were carried out from January to mid-March, 2005. The S-76 tests came through with flying colors and Sikorsky Aircraft plans on returning next winter for further trials.

NRC open circuit Propulsion Wind Tunnel.
NRC open circuit Propulsion Wind Tunnel.

Dr. Myron Oleskiw, NRC Aerospace icing specialist said, "The client desired a maximum airspeed of about 150 knots but the tunnel previously had only operated up to about 90 knots with its 750 kW electric fan drive. To increase that speed, we had to reduce the height of the tunnel's test section by adding a specially designed insert."

The wind tunnel 6000 kW gas turbine drive, de-commissioned over 15 years ago, also had to be made operational. On learning that the turbine drive was designed to use fuel which is no longer available, MacLeod's team got it to start at cold temperatures using regular gasoline then switched over to modern aviation fuel to keep it running. That allowed the tunnel to reach a maximum airspeed of 125 knots last winter with an additional speed increase expected to be available by this Fall.

Close-up of spray bars.
Close-up of spray bars.

A new spray system was also constructed. The spray bar array consisted of 16 horizontal bars holding up to 500 spray nozzles. Oleskiw said, "In addition to fabricating a new water supply system, we modified the existing air supply system to allow us to generate different spray patterns, while maintaining good spray uniformity. By varying the water flow rate and the air pressure, we were able to simulate droplets from 15 to 50 micrometers in size with icing intensities from 0.1 to 2.5 g/m3 at the maximum airspeed."

The tunnel's open-circuit design is ideal for engine tests as it prevents contaminants from recirculating within the tunnel. Because it also draws in air from outside, it can be used for wintertime testing. MacLeod explained, "The expensive part of icing tests is having to refrigerate the air, but here in Ottawa, Mother Nature provides the cold for four months of the year. We are able to be very cost-effective, as a result." Within those months, the full range of temperatures required for icing certification, -30°C to near 0°C, are obtainable.

Sikorsky/Turbomeca are just the first to take advantage of the tunnel's new capabilities. They won't be the last. The new icing facility is attracting the attention not only of helicopter manufacturers, who can take advantage of the wind tunnel's relatively large 3 m x 6 m regular test section to test engines and powered tail rotors, but also manufacturers of business jets and smaller aircraft who can check out wing de-/anti-icing systems on full-scale wing sections. It's even suitable for powered Unmanned Aerial Vehicles. Now that's a versatile tunnel.

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