3 m x 6 m Open-Circuit Propulsion Wind Tunnel

View of PIWT fan

The 3 m x 6 m Propulsion and Icing Wind Tunnel (PIWT) is a facility which bridges the gap between a conventional wind tunnel and an engine test cell. The wind tunnel has several unique features which lend themselves to a variety of applications.

The open-circuit layout, with fan at entry, permits contaminants associated with the test arrangements (such as heat, combustion products, wakes, jets, lost lubricants etc.) to discharge directly, without recirculating or contacting the fan. Additionally, a high solidity fan attenuates unsteadiness due to atmospheric wind. The fan is normally driven electrically but high-speed operation can be accommodated by a gas turbine drive system.

The working section floor may be raised to within 0.46 m of the centreline to facilitate work on test installations, to simulate varying ground effects, or to modify floor boundary layer characteristics. The floor may be solid or porous, and in the normal lowered position forms the upper surface of a 1.22 m deep steel plenum extending the full width and length of the working section.

Working section velocity non-uniformities are generally less than 0.5 per cent of mean velocity and over most of the working section flow direction is within 1° of the longitudinal axis. A test section insert is available to further increase wind speed.

Sikorsky S-76 helicopter half-model tested in the PIWT

Experiments on models of aeronautical propulsion systems are facilitated by a connection to the NRC Institute for Aerospace Research (NRC Aerospace) compressor / exhauster facility. Compressed air to simulate jet effluxes or to drive turbine-powered fans, and suction to simulate intake characteristics, are available.

Research on surface transport propulsion systems conducted in the PIWT has been concerned with cooling airflows. Aeronautical propulsion applications included tests on a turbo-prop engine (complete with propeller) mounted on force balances to permit measurement of engine performance various simulated flight conditions. Other development work carried out on thrust reverser behaviour applicable to turbo-fan engines.

The facility was also recently used for a major national study that examined the air quality associated with flaring of natural gas. The facility's size and an ability to provide fuel into the explosion-proof test section enabled the experiment to occur at full-scale in simulated natural wind conditions. This was critical to the project, as the scaling of combustion is not straightforward and the combustion is dependent on wind conditions. An instrumented rig of gas-detection equipment was installed downstream of the burning flare. It was mounted from a two-axis traverse enabling the flow to be surveyed over a large area.

Inclined stay-cable test

The PIWT is ideal for large-scale bluff-body aerodynamic investigations such as cable vibration studies. Inclined cables are prone to wind-induced vibration with amplitudes approximately equal to the cable diameter. This phenomenon is sensitive to Reynolds and Scruton numbers, which effectively means that full-scale cables must be tested at full-scale wind speeds. With the wind tunnel spray rigs, it is also possible to study rain-wind vibratory phenomena.

The length of the wind tunnel's test section also makes it ideal for simulating natural winds using the NRC-developed spire technique. Several recent investigations have focused on characterizing the highly turbulent air wake in the vicinity of aviation-capable ships. For further information on this topic, visit the aerodynamics of helicopter-ship interface page.

Currently, the PIWT is being used in icing research. The open-circuit design of the wind tunnel means a naturally cold test section is available in the winter. This capability, combined with the working section height, results in the ability to simulate larger water droplets than most icing wind tunnels can support. Small cloud droplets have been simulated in the wind tunnel and the potential exists to do a freezing drizzle simulation.

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