Spectroscopic Measurements of Shock-Layer Flows in an Arcjet Facility

Park, Chung S.; Newfield, Mark E.; Fletcher, Douglas G.; Gökçen, Tahir

doi:10.2514/2.6401

Cited by 23 publications

(25 citation statements)

References 4 publications

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“…They deduced rotational, NO-vibrational, and electronic excitation temperatures from the obtained spectra. The measured temperatures were T r 560, T v NO 950, and T ex 11; 500 K. In 1998 and 1999, Park et al [7,8] of NASA Ames Research Center also reported calibrated NO spectra measured in the same facility. The spectra [7] taken at 34.5 cm from the nozzle exit in 1998 have exactly the same shape as the spectra [8] obtained at 30 cm from the nozzle exit in 1999.…”

Section: Introductionmentioning

confidence: 94%

“…But such strong " radiation was not found in the measured spectra. These abnormal phenomena of NO and " in the arcjet flows were often simply attributed to non-Boltzmann excitations of NO electronic states [2,7,8]. But detailed excitation mechanisms have not been systematically investigated.…”

Section: Introductionmentioning

confidence: 96%

“…In the measurement of Park et al [7,8], NO " radiation was expected to be strong at wavelengths shorter than 2200 Å if the NO D 2 state was populated under the Boltzmann distribution. But such strong " radiation was not found in the measured spectra.…”

Section: Introductionmentioning

confidence: 99%

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Rate Parameters for Electronic Excitation of Diatomic Molecules: NO Radiation

Hyun

Park

Chang

2009

Journal of Thermophysics and Heat Transfer

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This is one of an ongoing series of papers on collisional excitation of electronic states in N 2 , O 2 , NO, CO, CN, and N 2 . In this paper, NO radiation observed in the test section of an arcjet wind tunnel is studied. In the experiments, NO and were seen, was not seen, and " was seen to be very weak. NO radiation is calculated with the use of the code SPRADIAN07 to explain the measured spectra. It was found that inverse predissociation is mainly responsible for the population of the NO C 2 r state during recombination of N and O atoms. The population of the NO A 2 state is mostly due to the radiative decay from the NO C 2 r state. The NO D 2 state is excited from the C 2 r state by collisions. The NO B 2 r state is populated by complicated collisional transition paths by passing through the intermediate states a 4 r and b 4 . These interpretations at least qualitatively explain the experimental data. Electronic excitation temperature is only remotely related to electron temperature. Nomenclature A = electronic state of the NO molecule, A 2 A h = excitation rate parameter, cm 3 =s A r = radiative transition probability, s 1 a = electronic state of the NO molecule, a 4 B = electronic state of the NO molecule, B 2 r b = electronic state of the NO molecule, b 4 C = electronic state of the NO molecule, C 2 r D = electronic state of the NO molecule, D 2 E = electronic term energy, cm 1 ; energy, cm 1 g = statistical weight (multiplicity, degeneracy) h = Plank constant, 6:6261 10 34 J s I = total band intensity, W=cm 3 I = specific intensity, W=cm 2 m sr i = electronic state i of the NO molecule J = rotational quantum number; rotational state j = electronic state j of the NO molecule K e = excitation rate by electron collision, cm 3 =s K h= excitation rate by heavy-particle collision, cm 3 =s K ivpr = rate coefficient for inverse predissociation, cm 3 =s K prd = rate coefficient for predissociation, s 1 k B = Boltzmann constant, 1:3807 10 23 J=K k = absorption coefficient, cm 1 M = colliding heavy particle or electron m = mass, g=mol n = number density, cm 3 ; excitation rate parameter, Eq. (10) p = pressure, atm Q = partition function S = spin angular momentum quantum number S J 0 0 J 00 00 = rotational line strength factor (Hönl-London factor) s = distance along a ray, cm T = heavy-particle translational temperature, K T d = activation temperature, K T e = electron temperature, K T ex = electronic excitation temperature, K T r = heavy-particle rotational temperature, K T v = vibrational temperature, K t = time, s v = vibrational quantum number, vibrational state X = ground electronic state of the NO molecule, X 2 r x = distance from the nozzle exit = NO B 2 r X 2 r transition = NO A 2 X 2 r transition = NO C 2 r X 2 r transition K = Kronecker delta " = NO D 2 X 2 r transition " = emission coefficient, W=cm 2 m sr = nonequilibrium factor = wavelength, Å or nm = orbital angular momentum quantum number about the internuclear axis = frequency, Hz = cross section, cm 2 = total mole fraction Subscripts A = electronic sta...

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Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 96%

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Rate Parameters for Electronic Excitation of Diatomic Molecules: NO Radiation

Hyun

Park

Chang

2009

Journal of Thermophysics and Heat Transfer

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“…In past studies, spectroscopic measurements and numerical calculations were conducted to characterize the arc plasma flow for air as a test gas. [6][7][8] Emission characteristics and the thermochemical state in the flow were clarified. Recently, spectroscopic measurements of CO2 arc plasma flow were conducted and flow temperatures were obtained.…”

Section: Introductionmentioning

confidence: 99%

Temperature Measurements of CO2 and CO2 - N2 Plasma Flows around a Blunt Body in an Arc-Heated Wind Tunnel

Yamada

Otsuta

Matsuno

et al. 2013

AEROSPACE TECHNOLOGY JAPAN

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The purpose of this research is to characterize the thermochemical states of CO2 and CO2-N2 arc plasma flows via temperature measurements. To do this, radiation from the stagnation streamline around a disk model is measured using the newly developed multipoint spectroscopic measurement system and temperatures are deduced by applying the spectrum fitting method to the measured spectra. It is found that the vibrational temperature is nearly constant and higher than the rotational temperature along the stagnation streamline, showing the vibrational nonequilibrium process. The rotational temperature is also nearly constant and does not increase in the shock layer. This may be caused by the fact that measured temperatures are averaged temperatures along the line-of-sight (LOS). In conclusion, the thermochemical states of CO2 and CO2-N2 arc plasma flows are vibrational nonequilibrium states in the free stream region. However, the thermochemical state in the shock layer cannot be clarified accurately using LOS averaged temperatures. In the future, LOS effects should be examined using spectroscopic measurements along a radial direction.

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“…The calculation of internal energy mode temperatures using radiation signals from NO band systems via comparison with numerical spectra simulation has been successfully demonstrated on numerous occasions in air plasma experiments. In the NASA Ames 20 MW arcjet wind tunnel, vibrational temperatures have been measured by using the emission spectra of the NO (A-X) and (C-X) bands [27,28]. In the same facility, rotational temperatures have also determined using the NO 0; 4, 0; 0, 0; 1, 0; 2, and 0; 3 bands [29].…”

Section: Introductionmentioning

confidence: 99%

NO and OH Spectroscopic Vibrational Temperature Measurements in a Post-Shock Relaxation Region

et al. 2010

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In this paper, spatial temperature profiles are examined in the nonequilibrium relaxation region behind a stationary shock wave in a hypervelocity air Mach 7.42 freestream. The normal shock wave is established through a Mach reflection from an opposing wedge arrangement in an expansion tube facility. Schlieren images confirm that the shock configuration is steady and the location is repeatable. Emission spectroscopy is used to identify dissociated species and to make vibrational temperature measurements using both the nitric oxide and the hydroxyl radical A-X band sequences. Temperature measurements are presented at selected locations behind the normal shock. LIFBASE is used as the simulation spectrum software for OH temperature-fitting; however, the need to access higher vibrational and rotational levels for NO leads to the use of an in-house developed algorithm. For NO, results demonstrate the contribution of higher vibrational and rotational levels to the spectra at the conditions of this study. Very good agreement is achieved between the experimentally measured NO vibrational temperatures and calculations performed using an existing state-resolved, three-dimensional forced-harmonic oscillator thermochemical model. The measured NO vibrational temperatures are significantly higher than the OH temperatures.

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Spectroscopic Measurements of Shock-Layer Flows in an Arcjet Facility

Cited by 23 publications

References 4 publications

Rate Parameters for Electronic Excitation of Diatomic Molecules: NO Radiation

Rate Parameters for Electronic Excitation of Diatomic Molecules: NO Radiation

Temperature Measurements of CO2 and CO2 - N2 Plasma Flows around a Blunt Body in an Arc-Heated Wind Tunnel

NO and OH Spectroscopic Vibrational Temperature Measurements in a Post-Shock Relaxation Region

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