Vibrational Energy Transfer in Diatomic Gas Mixtures

Horn, Kenneth P.; Oettinger, P. E.

doi:10.1063/1.1675290

Cited by 62 publications

(10 citation statements)

References 13 publications

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“…But firstly, notice how the vibrational levels attain a population distribution in the shape of Ϟ where a near "plateau" region forms around the intermediate levels. Caused by anharmonicity and coupling between the StS thermal and chemical kinetic processes [4,70], this trend is commonly observed in nonequilibrium expanding flows as shown numerically [4,21,23,44,45,47,[70][71][72], and experimentally [73,74]. Sometimes, a small peak is formed on the right (higher level) side of the plateau region due to population inversion, as seen in O2 in the current work and in Ref.…”

Section: On the Reduction Of Vvt Transitions A Influence Of Multi-qua...supporting

confidence: 74%

State-Specific Study of Air in the Expansion Tunnel Nozzle and Test Section

Hao

Wen

2022

AIAA Journal

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Thermochemical nonequilibrium in expansion tunnel nozzles is investigated numerically using a state-to-state description in one-dimension for representative air conditions. Limiting the multi-quantum jumps of VVT transitions to 3 in both N2 and O2 can accurately simulate the nonequilibrium nozzle flow. The reduction of VVT transitions to VT transitions works well. State-to-state modelling of an actual expansion tunnel nozzle condition yielded agreement with the measured static pressure. A study on the influence of different thermochemical excitation in the freestream at the test section shows that the post-shock radiation emissions can differ by more than 50 %. However, the non-Boltzmann distributions in the freestream has no influence. An evaluation of the discrepancy between the twotemperature and state-to-state models shows that the former generally predicts a faster thermochemical relaxation. Furthermore, the state-to-state results indicate that, in general, the molecular species all have a different vibrational temperature.

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Section: On the Reduction Of Vvt Transitions A Influence Of Multi-qua...supporting

confidence: 74%

State-Specific Study of Air in the Expansion Tunnel Nozzle and Test Section

Hao

Wen

2022

AIAA Journal

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“…15 In that experiment, a subsonic flow in a tube was heated with a microwave discharge. The measurement was made in the flow in the downstream relaxation region.…”

Section: Horn and Oettinger Experimentsmentioning

confidence: 99%

Estimation of excitation energy of diatomic molecules in expanding nonequilibrium flows

Park

1995

Journal of Thermophysics and Heat Transfer

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The energy contained in the highly excited vibrational and rotational states in a diatomic gas in a thermochemical nonequilibrium state during expansion is estimated. The population distribution of the vibrational and rotational states is assumed to be describable by a polynomial. The parameters in the polynomial are determined by invoking known physical constraints. The energy contained in the internal states in excess of that accounted for in the conventional method is calculated for N 2 , O 2 , NO, CO, and H 2 . The calculation is carried over a wide range of conditions, and the results are fitted with polynomials. The population distributions so determined agree with the theoretical and experimental results of others. A sample calculation made for a typical nozzle flow shows that the excess energy may reach 6% of the total enthalpy of the flow, and that the flow velocity may decrease by 3% due to this phenomenon. NomenclatureA = cross-sectional area of nozzle a { = coefficients of expansion of p, Eq. (29) c -continuum state D = dissociation energy measured from the ground vibrational state, eV or cm" 1 E = combined vibrational-rotational energy (E v + £,.), eVor cm" 1 E(i) = energy level of state /, eV or cm" 1 E r = rotational energy per molecule, eV or cm" 1 E v = vibrational energy per molecule measured from the ground vibrational state, eV or cm" 1 £ v = excess vibrational-rotational energy per unit mass, J/kg, Eq. (3) g = rotational statistical weight, 2J + 1 H = enthalpy /, /' = indices representing an internal state J = rotational quantum number K(i, /') = rate coefficient for collisional transition from state / to state /', m 3 /s k = Boltzmann constant M = see Eq. (8) m = exponent in Eq. (29) n = exponent in Eq. (29), or number density, m~3 n E (i) = number density of state / in equilibrium, m~3 n(i) = number density of state /, m~3 n x = number density of colliding particles, m" 3 p = pressure, atm Q = partition function R = absolute radius in E v vs E r coordinate system, eV or cm" 1 , Eq. (10) r = normalized radius, Eq. (11) T = heavy particle translational temperature, K T r = rotational temperature defined by lowest two states, K T v = vibrational temperature defined by lowest two states, K / = time, s V -flow velocity, m/s v -vibrational quantum number v -average thermal speed, m/s a = kTID dT r = see Eq. (16) 8T V = see Eq. (13) E = vibrational-rotational energy, eV or cm" 1 6 = characteristic vibrational temperature (co e /k), K 0 -polar angle in E v vs E r coordinate system, rad, Eq. (12) p(i) = normalized nonequilibrium population for state «, Eq. (5) p M = normalized nonequilibrium molecular density, Eq. (38) p = fluid density, kg/m 3 cr = excitation cross section, m 2 o} e = first vibrational constant, eV co e x e = second vibrational constant, eV Subscripts A = atomic species A av = average energy B -atomic species B E = equilibrium M = molecule m = maximum value s = settling chamber 0 = origin in E v vs E r coordinate system Superscript

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“…Figure 3 shows the vibrational population distribution functions (VDFs) of carbon monoxide inferred from highresolution (0.25 cm −1 ) CO infrared emission spectra recorded by the FT spectrometer. Vibrational level populations are inferred from the spectra using a standard technique [22].…”

Section: Thomson Discharge Measurementsmentioning

confidence: 99%

Ionization measurements in optically pumped discharges

Plönjes

Palm

Adamovich

et al. 2000

J. Phys. D: Appl. Phys.

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The kinetics of ionization and electron removal in optically pumped non-equilibrium plasmas sustained by a CO laser are studied using non-self-sustained dc and RF electric discharges. Experiments in optically pumped CO/Ar/N2 mixtures doped with O2 and NO demonstrated that associative ionization of CO produces free electrons at a rate up to S = 1015 cm-3 s-1. The ionization rate coefficient, inferred from the CO vibrational population measurements, is kion = (1.1-1.8)×10-13 cm3 s-1. It is shown that excited NO and possibly O2 molecules also contribute to the vibrationally stimulated ionization process. In a CO/Ar plasma, applying a dc bias to the cell electrodes resulted in the rapid accumulation of a deposit on the negative electrode due to a large cluster ion current. The average mass of an ion in this plasma, estimated by measuring the mass of the deposit, is m≅250 amu, which is consistent with the mass spectrometer analysis of the deposit. The deposit did not accumulate when small amounts of O2 and NO were added to the CO/Ar plasma, which presumably indicates the destruction of the cluster ions. It is demonstrated that adding small amounts of O2 to the optically pumped CO/Ar plasmas significantly increases the electron density, from ne = (4-7)×109 cm-3 to ne = (1-2)×1011 cm-3. This effect occurs at a nearly constant (within 50%) electron production rate S, indicating a substantial reduction in the overall electron removal rate. This reduction can be qualitatively interpreted as the destruction of rapidly recombining cluster ions in the presence of the O2 additive, and their replacement by monomer ions with a slower recombination rate. Further studies of the ion composition in optically pumped plasmas are suggested.

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Vibrational Energy Transfer in Diatomic Gas Mixtures

Cited by 62 publications

References 13 publications

State-Specific Study of Air in the Expansion Tunnel Nozzle and Test Section

State-Specific Study of Air in the Expansion Tunnel Nozzle and Test Section

Estimation of excitation energy of diatomic molecules in expanding nonequilibrium flows

Ionization measurements in optically pumped discharges

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