Absolute intensity of non-equilibrium radiation in air and stagnation heating at high altitudes

Camm, John C.; Kivel, B.; Taylor, Raymond L.; Teare, J.D.

doi:10.1016/0022-4073(61)90011-5

Cited by 37 publications

(9 citation statements)

References 5 publications

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“…However, all attempts to reproduce spectrally resolved emission spectra have been only partially successful. 7 ' 23 Several factors are responsible for this: 1) All previously available experimental data had very poor spectral resolution (AVCO data 1 ' 3 have a resolution of 100 A).…”

Section: Introductionmentioning

confidence: 98%

Modeling of nonequilibrium radiation phenomena - An assessment

Sharma

Whiting

1996

Journal of Thermophysics and Heat Transfer

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The present understanding of shock-layer radiation in the low-density regime, as appropriate to hypersonic vehicles, is discussed. Calculated spectra using the NONEQ and GENRAD computer programs are compared with experimental spectra recorded at NASA Ames's electric arc-driven shock-tube facility. The computations predict the intensity of the Nj(1~) system very well, but overpredict the intensities of various atomic O and N transitions and underpredict the intensities of the N 2 (2 + ) band system. To compute the correct electronic populations, it appears that the quasi-steady-state formulation must be expanded to include more individual electronic states. However, this may cause some computational difficulties and will require excitation rate data for many states, which are not well known. NomenclatureA t j = Einstein transition probability for spontaneous emission, particle" 1 s" 1 B A = Planck function, W/cm 2 /mi sr c = velocity of light, cm/s N = rotational quantum number N e = electron number density, cm" 3 N ion = ion number density, cm" 3 T e = electron temperature, K r elec = electronic temperature, K r ex = excitation temperature, Eq. (1), K T R = rotational temperature, K T v = vibrational temperature, K v = vibrational quantum number a = constant, Eq. (4) j8 = constant, Eq. (2) e = emission coefficient, W/cm 2 /mi sr K = absorption coefficient, cm" 1

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Section: Introductionmentioning

confidence: 98%

Modeling of nonequilibrium radiation phenomena - An assessment

Sharma

Whiting

1996

Journal of Thermophysics and Heat Transfer

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“…The N 2 + (l -) system lies in the same wavelength region but has been found to have a weak overshoot. 27 Other prominent features are additional peaks at 3100, 7600, and 9400 A, which are attributed to the N 2 (2+) and N 2 (l+) systems. The strongest overshoot observed has o a ratio of 6 and lies in the valley between the 3590 and 3883 A band heads of the CN violet system.…”

Section: Nonequilibrium Radiation Resultsmentioning

confidence: 97%

“…27 The sensitive element is high-purity tungsten having an impurity ratio of less than 100 parts per million. The gage is sting-mounted along the axis of the shock tube facing the driver diaphragm.…”

Section: Photoelectric Gage Measurementsmentioning

confidence: 99%

Experimental measurements of nonequilibrium and equilibrium radiation from planetary atmospheres.

Menard

Thomas

1966

AIAA Journal

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An electric arc-driven shock tube was used to study the effect of composition on the radiation from shock-heated mixtures of 9% CO 2 -90% N 2 -l% A, 30% CO 2 -70% N 2 , and 100% CO 2 . Measurements were made of the shock-layer radiance at the stagnation point of a flat-faced cylinder in the 0.3-to 2.7-ju. region, using a carbon-coated thin film gage for flight velocities from 20,000 to 46,000 fps and initial pressures varying from 0.25 to 2.00 mm Hg. Shock standoff distances were measured by photographic techniques. Photometric measurements were made of the intensity behind the incident shock in the 0.3-to 1.0-/i region, and a tungsten photoelectric gage measured the nonequilibrium intensity in the far ultraviolet region. Shock front integrated nonequilibrium and equilibrium intensities, nonequilibrium relaxation distances, and time to peak intensity were obtained. Stagnation-point radiance results are higher than one current estimate at high temperatures and low densities. Integrated nonequilibrium intensity for 9% CO 2 -90% N 2 -l% A mixtures was 32 w/cm 2 -27T sr at 25,000 fps. Major radiating species are identified as the CN radical for CO 2 -N 2 mixtures and the CO + ion for 100% CO 2 . Oscillator strengths for the CN red and violet systems are deduced from the measurements. The/ value results indirectly give support to a dissociation energy of 7.7 ± 0.1 ev for the CN radical.

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“…This property is called a "binary scaling" law of nonequilibrium radiation. 6 ' 8 Assuming that the gas radiation is optically thin, the radiative power emission per unit volume was obtained by dividing the observed radiative power into the side-on direction by the path length of the emitting medium. The radiative heat flux in the direction of gas flow, that is, in the end-on direction shown in Fig.…”

Section: Laboratory Datamentioning

confidence: 99%

Radiation enhancement by nonequilibrium in earth's atmosphere

Park

1985

Journal of Spacecraft and Rockets

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The status of knowledge of shock-layer radiation in the low-density nonequilibrium regime, as appropriate to the flight of the proposed aeroassisted orbital transfer vehicle, is surveyed. The existing laboratory data and the flight data from Apollo and Fire are scrutinized. Nonequilibrium radiation is found to be significant in the flight regime of the vehicle, but a factor-of-three uncertainty is found in its magnitude. The available theoretical models are reviewed, their weaknesses are pointed out, a computer code that approximately reproduces the existing data is introduced, and recommendations are made for future research. NomenclatureA = reference surface area of a vehicle AJJ =rate coefficient of radiative transition from state / to state j B-= matrix consisting of collisional and radiative transition rates in the left-hand side of quasisteady-state master equation (9) C d =drag coefficient Cj = vector in the right-hand side of quasi-steady-state master equation (9) D = diffusion coefficient G = gravitational constant g = statistical weight of an internal state h -altitude hj = enthalpy of species / / = intensity of radiation I s = specific impulse of a rocket engine KJJ = rate coefficient of collisional transition from state / to state j k = thermal conductivity Le = Lewis number M = mass of vehicle N e = electron number density n -number density of an internal state n, = number density of state / Pr =Prandtl number p = pressure q =heat flux Rj.= forward reaction rate R r = reverse reaction rate T = heavy-particle translational temperature T e = electron translational temperature t =time u = flow velocity in tangential direction V r 00 = flight velocity X = number density of unspecified species x -distance from shock wave a = species mass fraction e -ionization fraction p = densityPresented as Paper 83-0410 at the AIAA 21st Aerospace Sciences Meeting, Reno, Nev.,

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Absolute intensity of non-equilibrium radiation in air and stagnation heating at high altitudes

Cited by 37 publications

References 5 publications

Modeling of nonequilibrium radiation phenomena - An assessment

Modeling of nonequilibrium radiation phenomena - An assessment

Experimental measurements of nonequilibrium and equilibrium radiation from planetary atmospheres.

Radiation enhancement by nonequilibrium in earth's atmosphere

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