Test time increase by delaying driver gas contamination for reflected shock tunnels

A gasdynamical detector has been applied to measure the arrival time of dri ver gas in a low concentration in the test section of a high-enthalpy shock tunnel. The detection determines the useful test time with uncontaminated test gas for a wide range of specific reservoir enthalpies. Effects of over - or undertailored interface condition on severe contamination have been in vestigated,It is experimentally demonstrated that overtailored interface op eration must be avoided to achieve the test duration necessary for aerodyna mic measurements, especially for high-enthalpy Row. The interface condition is optimized for the longest test time attainable. As an active method for delaying driver gas contamination, a device to trap the driver gas at the end of the shock tube has been tried for an overtailored condition. The met hod, however, causes the contamination to occur earlier. A modified device using a sleeve to capture driver gas upstream has been developed. Results w ith the longest sleeve tested show that strong contamination is dramaticall y delayed and that the uncontaminated test time is significantly increased. Nevertheless, improved test times are still shorter than the test time wit hout the device at a slightly undertailored condition.