Variation of pilot pressure was observed in a Mach 10 nozzle calibration test of the National Aerospace Laboratory 1.27m hypersonic wind tunnel immediately after a humid combustion gas evacuation system was added to the air heater. The mix of humidity provided by condensed water inside the tunnel structure was evaluation using run-by-run variations of evacuated heater pressure and of measured humidity level in the working air. The calibration data were also examined and a non-isentropic condensing flow through the nozzle was believed to have occurred. Thus modifications to prevent condensing of water were carried out and constant pitot pressure was obtained in a further calibration test. A statistical assessment was made of the data obtained before and after these modifications, and the results were compared to confirm the existence of a repeatable isentropic flow. This allowed efficient humidity management within the operation cycle. The water-effect free flow was assured by monitoring the humidity level and nozzle exit wall pressure.
Technical Report of National Aerospace Laboratory Management for the NAL 1.27m Hypersonic Wind Tunnel
2001
18 pages
Report
Keine Angabe
Englisch