ADVANCED DESIGN FEATURES IN CANADA'S SUPERSONIC WIND TUNNEL 620458
This paper describes the methods employed in stabilizing stagnation temperature, settling chamber pressure and transonic Mach number in the 5 ft × 5 ft High Speed Wind Tunnel of the National Aeronautical Establishment, Ottawa, Canada.
Under the most demanding flow conditions a temperature drop of less than 10°F is achieved by 210 tons of thin walled tubing placed in the last 90 feet of the last of three storage vessels connected in series.
Pressure in the settling chamber is maintained constant within ± 0.5% over the range 1.8 to 13.5 atmospheres by a specially designed 72" diameter sleeve valve and matching feedback control system. The valve also incorporates a unique safety feature - that of physically preventing the valve from over-opening and hence over-pressuring the tunnel circuit in the event of a control system malfunction.
The Transonic Test section Mach number is held constant, within ±0.5% against disturbances created during changes in model incidence by flow through porous walls into a plenum which is then ejected back into the tunnel stream aft of the model. Control of this flow is achieved by movable flaps at entry to the variable diffuser which are part of a pressure regulating system whose setting is controlled by changes of pressure within the plenum chamber.