Driver gas contamination in high-enthalpy shock tunnels has been detected using a gasdynamical device composed of a duct and a wedge. The detection technique was developed in the T 5 shock tunnel, and a detector has been newly designed for use in the HEK and HIEST shock tunnels with some modifications. Driver gas in low concentration is satisfactorily detected at the test sections of both shock tunnels. The detector allows the flow visualization of duct internal flow, and a sequence of Schlieren pictures during a shot gives a better understanding of unsteady duct choking phenomena. Futhermore, the useful test time is compared among three shock tunnels and the optimum length-to-diameter ratio of shock tube is discussed.
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