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

A gasdynamical detectorhas been applied to measure thearrival timeof driver gas in a low concentration in the testsectionofa high-enthalpyshock tunnel. Thedetection determines theusefultesttimewith uncontaminated test gas for a wide range of specie c reservoir enthalpies. Effects of over- or undertailored interface condition on severe contaminationhavebeeninvestigated.Itisexperimentallydemonstratedthatovertailoredinterfaceoperationmust beavoided toachievethetestdurationnecessary foraerodynamicmeasurements,especially forhigh-enthalpy e ow. Theinterfacecondition isoptimized forthelongesttesttimeattainable. Asan activemethod fordelaying drivergas contamination,adevicetotrapthedrivergasattheendoftheshocktubehasbeentriedforanovertailoredcondition. The method, however, causes the contamination to occur earlier. A modie ed device using a sleeve to capture driver gas upstream has been developed. Results with the longest sleeve tested show that strong contamination is dramatically delayed and that the uncontaminated test time is signie cantly increased. Nevertheless, improved test times are still shorter than the test time without the device at a slightly undertailored condition.