Mass spectrometric measurements of the freestream composition in the T4 free-piston shock tunnel

Boyce, R. R., Takahashi, M. and Stalker, R. J. (2005) Mass spectrometric measurements of the freestream composition in the T4 free-piston shock tunnel. Shock Waves Journal, 14 5-6: 359-370. doi:10.1007/s00193-005-0275-4

Author Boyce, R. R.
Takahashi, M.
Stalker, R. J.
Title Mass spectrometric measurements of the freestream composition in the T4 free-piston shock tunnel
Journal name Shock Waves Journal   Check publisher's open access policy
ISSN 0938-1287
Publication date 2005-01-01
Sub-type Article (original research)
DOI 10.1007/s00193-005-0275-4
Volume 14
Issue 5-6
Start page 359
End page 370
Total pages 12
Place of publication Berlin
Publisher Springer - Verlag
Language eng
Subject 090107 Hypersonic Propulsion and Hypersonic Aerodynamics
Abstract The freestream composition is an important parameter in ground-based aerodynamic testing, and direct measurement of it is very important. This paper reports extensive composition measurements in the freestream of the T4 free-piston shock-tunnel, employing a recently improved time-of-flight mass spectrometer. A wide range of nozzle reservoir conditions were used. The results show good agreement between measured and theoretical values for nitric oxide over the entire enthalpy range reported (2.5–13 MJ/kg). This provides confidence that the chemistry model is correctly predicting sudden freezing of NO in the nozzle expansion. On the other hand, no monatomic species have been measured other than those produced by dissociative ionisation within the mass spectrometer, even at flow conditions where significant freestream dissociation is expected. Furthermore, excess diatomic oxygen is detected at high enthalpies. These observations are consistent with the possibility that oxygen recombination is not correctly predicted in the nozzle expansion, with sudden freezing occurring significantly later than predicted. However, the observations are also consistent with possible catalytic recombination in the skimmer system. The possibility for producing an empirical correlation between the freestream composition and the reservoir entropy has also been observed.
Keyword Time-of-flight mass spectrometer
Freestream species composition
Shock tunnel
Catalytic recombination
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collections: Faculty of Engineering, Architecture and Information Technology Publications
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