Mass spectrometric measurements of the freestream composition in the T4 free-piston shock-tunnel |
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Authors: | R R Boyce M Takahashi R J Stalker |
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Institution: | (1) Formerly Mechanical Engineering, University of Queensland, Australia;(2) School of Aerospace, Civil and Mechanical Engineering, University College, University of New South Wales, Australian Defence Force Academy, Canberra, 2600, Australia;(3) Japanese Aerospace Exploration Agency, Kakuda Space Center, 1 Koganesawa, Kimigaya, Kakuda-shi, Miyagi 981-1525, Japan;(4) Division of Mechanical Engineering, University of Queensland, Brisbane, 4072, Australia |
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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.
PACS 07.75.th; 47.40.-x |
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Keywords: | Time-of-flight mass spectrometer Freestream species composition Shock tunnel Catalytic recombination Skimmer |
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