Stagnation temperature measurements in the USQ hypersonic wind tunnel

Abstract

A thermocouple probe with a heated shield has been used to measure stagnation temperature at the nozzle exit of the University of Southern Queensland hypersonic wind tunnel. The thermocouple probe consisted of a welded junction T-type thermocouple mounted within a heated tube with a vent hole downstream of the junction. Pressure transducers within the barrel of the wind tunnel have also been used to obtain the pressure history during the free piston compression process. The pressure measurements have been used to provide a theoretical value for the flow stagnation temperature for direct comparison with the thermocouple measurements. Assuming isentropic compression of the test gas, the flow stagnation temperature would be about 571 K for the current operating condition. After applying a response-time correction for the thermocouple signals, a stagnation temperature value of about 495 K was obtained from the measurements. The measured stagnation temperature of the test gas is somewhat lower than the isentropic value because of heat loss from the test gas to the barrel during the test gas compression and discharge process.