Vibrational relaxation of CO by O atoms

Center, R. E.

doi:10.1063/1.1679135

Cited by 47 publications

(24 citation statements)

References 20 publications

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“…Models in the literature indicate that with only 1% H 2 O present, at the nozzle exit pressure and temperature, the vibrational relaxation time of N 2 is reduced to 5 µs (as opposed to many milliseconds), and this time is further reduced by increases in temperature or pressure. 20 Thus the observation of equilibrium in the combustion products is again plausible.…”

Section: Cars Resultsmentioning

confidence: 99%

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

Cutler

Magnotti

Cantu

et al. 2012

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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In this paper we describe efforts to obtain canonical data sets to assist computational modelers in their development of models for the prediction of mixing and combustion in scramjet combustors operating in the ramjet-scramjet transition regime. The CARS technique is employed to acquire temporally and spatially resolved measurements of temperature and species mole-fraction at four planes, one upstream of an H 2 fuel injector and three downstream. The technique is described and results are presented for cases with and without chemical reaction. The vibrational energy mode in the heated airstream of the combustor was observed to be frozen at near facility heater conditions and significant nonuniformities in temperature were observed, attributed to non-uniformities of temperature exiting the heater. The measurements downstream of fuel injection show development of mixing and combustion, and are already proving useful to the modelers.

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Section: Cars Resultsmentioning

confidence: 99%

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

Cutler

Magnotti

Cantu

et al. 2012

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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“…Center (1973) found O atoms an order of magnitude more efficient at relaxing the bending mode than Ar atoms; a probability of about 1~o was measured at 3000 K. Bass (1974) computed the probabilities assuming classical scattering with a hard sphere interaction and quasi-diatomic model for CO 2 for energies from 1 to 10 eV and found that when the C atom was struck by the impinging O atom, the average fraction of energy transferred to the v 2 mode was 0.447. Schatz and Redmon (1981) used quasi-classical trajectory theory to compute the cross sections for excitation of the bending mode and found avalueofl.9 x 10 -15 2 cm at 2.2 eV, whereas the excitation of the symmetric and asymmetric stretch modes were 2 and 4-5 orders of magnitude smaller, respectively.…”

Section: Ir Heating and 15-pm Coolingmentioning

confidence: 99%

Structure, luminosity, and dynamics of the Venus thermosphere

Fox

Bougher

1991

Space Sci Rev

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We review here observations and models related to the chemical and thermal structures, airglow and auroral emissions and dynamics of the Venus thermosphere, and compare empirical models of the neutral densities based in large part on in situ measurements obtained by the Pioneer Venus spacecraft.Observations of the intensities of emissions are important as a diagnostic tool for understanding the chemical and physical processes taking place in the Venus thermosphere. Measurements, ground-based and from rockets, satellites, and spacecraft, and model predictions of atomic, molecular and ionic emissions, are presented and the most important sources are elucidated. Coronas of hot hydrogen and hot oxygen have been observed to surround the terrestrial planets. We discuss the observations of and production mechanisms for the extended exospheres and models for the escape of lighter species from the atmosphere. Over the last decade and a half, models have attempted to explain the unexpectedly cold temperatures in the Venus thermosphere; recently considerable progress has been made, although some controversies remain. We review the history of these models and discuss the heating and cooling mechanisms that are presently considered to be the most important in determining the thermal structure. Finally, we discuss major aspects of the circulation and dynamics of the thermosphere: the sub-solar to anti-solar circulation, superrotation, and turbulent processes.

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“…During the Configuration C test campaign (with essentially identical CARS instrumentation to A) we acquired CARS data sets at the entrance plane with various levels of steam introduced in the facility heater. Since steam is known to greatly increase the rate at which N 2 relaxes to thermal equilibrium, 15 this experiment was expected to confirm the hypothesis that non-equilibrium was a result of processes in the flow and provide useful information on relaxation rates. Figure 4 shows experimental CARS spectra (200 shot averages) acquired near the center of the duct for cases with no steam (i.e., "clean air"), and 1.9%, 3.7% and 5.7% steam.…”

Section: A Existence Of Non-equilibriummentioning

confidence: 60%

“…Addition of steam was expected to bring the gas flow back towards equilibrium. 15 Computations of the flowfield for both equilibrium and thermal nonequilibrium have been performed and are compared with the data. Our contribution is to demonstrate that vibrational non-equilibrium can be found in supersonic nozzles as well as hypersonic nozzles, and show that published modeling methods can predict it.…”

Section: Introductionmentioning

confidence: 99%