Measurement of Vibrational Nonequilibrium in a Supersonic Freestream Using Dual-Pump CARS

Cutler, Andrew D.; Magnotti, Gaetano; Cantu, Luca; Gallo, Emanuela; Danehy, Paul M.; Burle, Rob; Rockwell, Robert D.; Goyne, Christopher P.; McDaniel, James C.

doi:10.2514/6.2012-3199

Cited by 8 publications

(5 citation statements)

References 26 publications

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“…12 The N 2 and O 2 Q-branches and several H 2 rotational lines are resonant in our spectra. The remaining major species in H 2 -air combustion is H 2 O which is not resonant but can be estimated by difference.…”

Section: Fitting Algorithmmentioning

confidence: 96%

“…The difference between rotational and vibrational temperature in the freestream is real and consistent with predictions by computational modeling, as previously discussed. 12 In the freestream flow of this scramjet the N 2 is vibrationally frozen at the temperature in the facility heater. Some of the measured unsteadiness may be attributed to instrument noise, while some is real, originating in the facility heater, or due to effects of unsteadiness in the boundary layers and fuel plume.…”

Section: Equationmentioning

confidence: 99%

“…In Ref. 12 we reported on CARS measurements at the entrance plane of the combustor for both configurations A and C and these showed that the N 2 (and to a lesser extent the O 2 ) entering the combustor was not in vibrational equilibrium, but that the N 2 vibrational temperature was equal to the temperature in the facility heater while the rotational temperature was much cooler. This non-equilibrium was present even for configuration C where the entrance plane was further downstream (after the inlet isolator).…”

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confidence: 99%

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Dual-Pump CARS Measurements in the University of Virginia's Dual-Mode Scramjet: Configuration "C"

Cutler

Magnotti

Cantu

et al. 2013

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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Measurements have been conducted at the University of Virginia Supersonic CombustionFacility in configuration C of the dual-mode scramjet. This is a continuation of previously published works on configuration A. The scramjet is hydrogen fueled and operated at two equivalence ratios, one representative of the "scram" mode and the other of the "ram" mode. Dual-pump CARS was used to acquire the mole fractions of the major species as well as the rotational and vibrational temperatures of N 2 . Developments in methods and uncertainties in fitting CARS spectra for vibrational temperature are discussed. Mean quantities and the standard deviation of the turbulent fluctuations at multiple planes in the flow path are presented. In the "scram" case the combustion of fuel is completed before the end of the measurement domain, while for the ram case the measurement domain extends into the region where the flow is accelerating and combustion is almost completed. Higher vibrational than rotational temperature is observed in those parts of the hot combustion plume where there is substantial H 2 (and hence chemical reaction) present.

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Section: Fitting Algorithmmentioning

confidence: 96%

Section: Equationmentioning

confidence: 99%

mentioning

confidence: 99%

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Dual-Pump CARS Measurements in the University of Virginia's Dual-Mode Scramjet: Configuration "C"

Cutler

Magnotti

Cantu

et al. 2013

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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“…Palma, Danehy and Houwing 3 also used NO PLIF but excited several vibrational and rotational ground states to generate Boltzmann plots for rotational and vibrational distributions and thus infer these two temperatures independently in a shock-heated nozzle flow. Cutler et al 4 used dual-pump coherent anti-Stokes Raman spectroscopy (CARS) to study the effect of vitiation on vibrational non-equilibrium in a high-enthalpy nozzle flow. With this technique, simultaneous pointwise information about the temperature and mole fraction of O2 and N2 was obtained and used to validate a CFD simulation.…”

Section: Introductionmentioning

confidence: 99%

“…Several previous studies have documented vibrational non-equilibrium effects in turbulent flows. For example, spontaneous Raman spectroscopy 1 , nitric oxide planar laser induced fluorescence (NO-PLIF) 2,3 , and coherent anti-Stokes Raman spectroscopy (CARS) 4 have all been used as measurement techniques. Sharma et al 1 used spontaneous Raman scattering to and infer vibrational temperatues of rapidly expanding nitrogen at points along the axis of a nozzle in a shock tunnel.…”

Section: Introductionmentioning

confidence: 99%

Vibrational Non-equilibrium Effects in Supersonic Jet Mixing

Reising

Utsav

Voelkel

et al. 2014

52nd Aerospace Sciences Meeting

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A joint experimental and computational study is being conducted to investigate the effects of vibrational non-equilibrium on supersonic combustion, although the focus of this paper is on mixing between a supersonic jet and a subsonic coflow. A new facility has been constructed that consists of a Mach 1.5 turbulent jet issuing into an electrically heated coflow. In the preliminary experiments reported here, air is used in both the jet and the coflow. The degree of non-equilibrium in the jet shear layers is quantified by using high-spectral resolution timeaverage spontaneous Raman scattering. The Raman scattering is complemented with planar temperature imaging using Rayleigh scattering. Much of the current work is focused on the extent to which vibrational non-equilibrium can be assessed by using time-averaged Raman scattering in a turbulent flow with large-scale temperature fluctuations. The experimental work is supported by direct numerical simulation of related jet flows. Preliminary DNS of turbulent jets in coflow with imposed vibrational non-equilibrium shows that vibrational relaxation effects have a first-order effect on the jet temperature field and mixing physics. Nomenclature= specific heat at constant volume of species, α = vibrational energy = projected pixel dimension in physical plane = convective Mach number = incident laser power = Rayleigh scattered power = partition function − = translational-vibrational energy exchange , = reference temperature by which is defined for species, α = rotational temperature = translational temperature = vibrational temperature = passive scalar concentration = visual shear layer thickness  = characteristic vibrational temperature of an oscillator  = reduced mass of colliding pair 2  = vibrational relaxation timescale Ø = mass fraction of species, α = mixture fraction of species, α = collection solid angle ( ) = Rayleigh scattering cross-section

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Interferometry analysis and CARS measurements of nonequilibrium in hypersonic oxygen/argon and pure oxygen flows

Anaya,

Manavi,

Tropina

et al. 2024

Exp Fluids

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Measurement of Vibrational Nonequilibrium in a Supersonic Freestream Using Dual-Pump CARS

Abstract: Measurements have been conducted at the University of Virginia Supersonic Combustion

Cited by 8 publications

References 26 publications

Dual-Pump CARS Measurements in the University of Virginia's Dual-Mode Scramjet: Configuration "C"

Dual-Pump CARS Measurements in the University of Virginia's Dual-Mode Scramjet: Configuration "C"

Vibrational Non-equilibrium Effects in Supersonic Jet Mixing

Interferometry analysis and CARS measurements of nonequilibrium in hypersonic oxygen/argon and pure oxygen flows

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