Measurements of Metastable N2(A3Σu+,v) Molecules in Nonequilibrium Supersonic Flows
- 1 January 2022
- journal article
- research article
- Published by American Institute of Aeronautics and Astronautics (AIAA) in Journal of Thermophysics and Heat Transfer
- Vol. 36 (1), 196-206
- https://doi.org/10.2514/1.t6254
Abstract
Nonintrusive laser diagnostics are used for the measurements of metastable nitrogen molecules in the lowest excited electronic state, , in a nonequilibrium flow, blowdown supersonic wind tunnel. The tunnel is operated with nitrogen at plenum pressures of Torr, with the flow expanding through a two-dimensional contoured nozzle to the Mach number of . The steady-state run time of the tunnel is approximately 10 s. The flow is excited by a repetitive nanosecond pulse discharge operated in the plenum or in the nozzle throat. Time-resolved absolute populations in the plenum are measured by single-pass, continuous wave tunable diode laser absorption spectroscopy (TDLAS). In the supersonic test section, absolute populations are measured by cavity ring down spectroscopy (CRDS), using a tunable pulsed laser system operated at 10 Hz. During each run, 50 single-shot ring down traces are acquired, demonstrating good shot-to-shot reproducibility. The results demonstrate that the cavity ring down time is not affected by the supersonic flow. populations and the flow temperature are inferred from the single-shot CRDS data. At the conditions when the flow is excited by the discharge in the nozzle throat, population in the supersonic test section is measured by both CRDS and TDLAS diagnostics. The two diagnostic techniques are complementary and can be used for characterization of nonequilibrium reacting flows over a wide range of pressures, including short-run-time high-enthalpy flow facilities.
Keywords
Funding Information
- Air Force Office of Scientific Research/ Energy Transfer Processes in Nonequilibrium Hypers ((FA9550-17-1-0370))
This publication has 27 references indexed in Scilit:
- Development of a Mach 5 Nonequilibrium-Flow Wind TunnelAIAA Journal, 2012
- Nitrogen Vibrational Population Measurements in the Plenum of a Hypersonic Wind TunnelAIAA Journal, 2012
- Time-Resolved CRDS Measurements of the N2(A3Σu+) Density Produced by Nanosecond Discharges in Atmospheric Pressure Nitrogen and AirThe Journal of Physical Chemistry A, 2009
- Comprehensive analysis of the effect of atomic and molecular metastable state excitation on air plasma composition behind strong shock wavesPlasma Sources Science and Technology, 2009
- Laser-induced fluorescence of N2( A\,^3\Sigma_{\rm u}^+ ) metastable in N2pulsed positive corona dischargePlasma Sources Science and Technology, 2009
- Absolute number densities of vibrationally excited ) produced in a low pressure rf plasmaJournal of Physics D: Applied Physics, 2006
- Kinetics of N2(A3Σu+) molecules and ionization mechanisms in the afterglow of a flowing N2microwave dischargeJournal of Physics D: Applied Physics, 2001
- Experimental and Numerical Study of Nonequilibrium Ultraviolet NO and N Emission in Shock LayerJournal of Thermophysics and Heat Transfer, 1998
- Examination of theory for bow shock ultraviolet rocket experiments. IIJournal of Thermophysics and Heat Transfer, 1994
- Comparison of theory with experiment for the bow shock ultraviolet rocket flightJournal of Thermophysics and Heat Transfer, 1993