Modeling of nonequilibrium CO Fourth-Positive and CN Violet emission in CO 2 –N 2 gases

Johnston, Christopher O.; Brandis, Aaron M.

doi:10.1016/j.jqsrt.2014.08.025

Cited by 96 publications

(38 citation statements)

References 39 publications

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“…The shock detachment distance was inversely proportional to the density ratio across the shock for hypersonic blunt bodies [40]. The Johnston model, which provided higher probabilities for third-body and neutral exchange reactions involving CO and CN in particular [25], resulted in a higher post-shock density as compared to the Park model. This was the reason for the smaller shock detachment distance.…”

Section: B Flowfield Resultsmentioning

confidence: 95%

“…The Millikan-White model with the Park high-temperature correction was used for vibrational relaxation, whereas the Appleton-Bray ion or neutral models were applied for translation-electron energy exchange. Chemistry-vibration coupling was accounted for by Treanor [25], comprising 16 species and 34 reactions for CO 2 -N 2 flows, which presented tuned kinetic rates to match CO fourth-positive and CN Violet band radiation measured at NASA's Electric Arc Shock Tube facility. The Gupta-Yos mixing rule [26,27] was applied, with the relevant collision integrals [28,29], to calculate the viscosity and thermal conductivity of the mixture.…”

Section: A Flowfield Modelingmentioning

confidence: 99%

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Venus Entry Flow over a Decomposing Aeroshell in X2 Expansion Tube

Banerji¹,

Leyland²,

Fahy³

et al. 2018

Journal of Thermophysics and Heat Transfer

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The effects of phenolic decomposition on shock-layer radiation were investigated experimentally in X2 expansion tube for a Venus entry flow. A carbon-phenolic composite aeroshell was subjected to a flow with a flight equivalent velocity of 9.35 km ⋅ s −1 . Emission spectroscopy was used to measure boundary-layer radiation in parts of the ultraviolet (380-480 nm) and visible (620-700 nm) spectrum, and it was compared to control measurements taken with a cold steel model. With the composite model in place, the calibrated spectral radiance measured was seen to increase for the O (645.598 nm) atomic line and the N 2 (391.22 nm) band head, but it decreased for the C 2 Swan band (420-480 nm). The recorded data were then compared to numerical spectra produced by two-dimensional axisymmetric computational fluid dynamic simulations coupled to a radiation solver. Both of the applied chemistry models overpredicted CN violet Δν 0 band radiation, which demonstrated strong self-absorption at these conditions. Better comparisons were achieved for the C 2 Swan band radiation. At visible wavelengths, peak intensities were underestimated by the numerical simulations. Several possible reasons were hypothesized for these discrepancies.

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Section: B Flowfield Resultsmentioning

confidence: 95%

Section: A Flowfield Modelingmentioning

confidence: 99%

Venus Entry Flow over a Decomposing Aeroshell in X2 Expansion Tube

Banerji¹,

Leyland²,

Fahy³

et al. 2018

Journal of Thermophysics and Heat Transfer

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“…As shown in [10], different models match the data at different velocities, the result of which would be a shift when the data are compared with only one model as a function of velocity. Other works have explored adjustments to the chemical kinetics at higher velocity and shown significant impact on radiative heating in nonequilibrium [18,20,21].…”

Section: Radiative Heating Predictionmentioning

confidence: 99%

Radiative Heating During Mars Science Laboratory Entry: Simulation, Ground Test, and Flight

Cruden

Brandis

White

et al. 2016

Journal of Thermophysics and Heat Transfer

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The heat shield of the Mars Science Laboratory was equipped with thermocouple stacks to measure in-depth heating of the thermal protection system during atmospheric entry. The heat load derived from the thermocouples in the stagnation region was found to be 33% lower than corresponding postflight predictions of convective heating alone. It was hypothesized that this difference could be attributed to radiation from the shock-heated gas, a mechanism not considered in preflight analyses of flowfields. To test the hypothesis and quantify the contribution of shock-layer radiation to total surface heating, ground tests and simulations (both flow and radiation) were performed at several points along the best-estimated entry trajectory of the Mars Science Laboratory. The present paper provides an assessment of the quality of the radiation model and its impact to stagnation point heating. The impact of radiative heating is shown to account for 43% of the heat load discrepancy. Additional possible factors behind the remaining discrepancy are discussed. Nomenclature B λ T = Planck (blackbody) function at temperature, T, W∕cm 2 · sr · μm D = shock-tube diameter, m d = shock standoff distance, m e λ x = emission coefficient at position x, W∕cm 2 · sr · μm L λ x = spectral radiance at position x, W∕cm 2 · sr · μm L λ x; θ = spectral radiance at position x at off-normal angle θ, W∕cm 2 · sr · μm _ m = mass blowing rate, kg∕m 2 · s q = heat flux or irradiance Tx = temperature at position x, K v = velocity, m∕s x = position along stagnation line or perpendicular to heat shield, cm or m y = position along heat shield surface, m δ = boundary-layer thickness, m θ = off-normal angle, rad λ = wavelength, nm p c = ablation product density, kg∕m 3

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“…The kinetic data set used for LAURA is detailed in Ref. 18 and the kinetic data set used for DPLR is detailed in Ref. 19.…”

Section: B Kinetic Modelsmentioning

confidence: 99%

“…The most current models employed in HARA for Martian atmosphere kinetic processes which affect radiation are presented in Ref. 18. The radiative processes included in these simulations were the CO, CO 2 and O 2 molecular band systems.…”

Section: Radiation Transport Solversmentioning

confidence: 99%

Blunt-Body Heating and Pressure Database from High-Enthalpy, CO₂ Testing in an Expansion Tunnel

Hollis

Prabhu

MacLean

2016

46th AIAA Thermophysics Conference

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An extensive database of heating, pressure, and flow field measurements on a 70-deg sphere-cone blunt body geometry in high-enthalpy, CO 2 flow has been generated through testing in an expansion tunnel. This database is intended to support development and validation of computational tools and methods to be employed in the design of future Mars missions. The test was conducted in an expansion tunnel in order to avoid uncertainties in the definition of free stream conditions noted in previous studies performed in reflected shock tunnels. Data were obtained across a wide range of test velocity/density conditions that produced various physical phenomena of interest, including laminar and transitional/turbulent boundary layers, non-reacting to completely dissociated post-shock gas composition and shock-layer radiation. Flow field computations were performed at the test conditions and comparisons were made with the experimental data. Based on these comparisons, it is recommended that computational uncertainties on surface heating and pressure for laminar, reacting-gas environments can be reduced to ±10% and ±5%, respectively. However, for flows with turbulence and shock-layer radiation, sufficient validation-quality data were not obtained in this study to make any conclusions with respect to uncertainties for those phenomena, which highlights the need for further research in these areas. NomenclatureA f,j = rate coefficient for forward reaction j (m 3 /kmol.s) D f,j = characteristic temperature of forward reaction j (K) H 0 = total enthalpy (J/kg) H w = wall enthalpy (J/kg) K c = equilibrium constant (-) or (kmol/m 3 ) k b,j = backward rate for reaction j (m 3 /kmol.s) or (m 6 /kmol 2 .s) k f,j = forward rate for reaction j (m 3 /kmol.s) M ∞ = free stream Mach number P ∞ = free stream pressure (Pa) P 0,2 = post-shock pitot pressure (Pa) q w = heat-transfer rate at the wall (W/m 2 ) Re ∞,D = free stream Reynolds Number based on diameter -ρ ∞ U ∞ D/μ ∞ Reθ = momentum thickness Reynolds Number -ρ e U e θ/μ e T a,j = controlling temperature for forward reaction j (K) T ∞ = free stream temperature (K) T w = wall temperature (K) U ∞ = free stream velocity (m/s) * Associate Fellow AIAA, Senior Technical Lead, Aerothermodynamics Branch, Research Directorate † Associate Fellow AIAA, Senior Scientist ‡ Senior Member AIAA, Senior Research Scientist Downloaded by PURDUE UNIVERSITY on June 25, 2016 | http://arc.aiaa.org |

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Modeling of nonequilibrium CO Fourth-Positive and CN Violet emission in CO 2 –N 2 gases

Cited by 96 publications

References 39 publications

Venus Entry Flow over a Decomposing Aeroshell in X2 Expansion Tube

Venus Entry Flow over a Decomposing Aeroshell in X2 Expansion Tube

Radiative Heating During Mars Science Laboratory Entry: Simulation, Ground Test, and Flight

Blunt-Body Heating and Pressure Database from High-Enthalpy, CO₂ Testing in an Expansion Tunnel

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Modeling of nonequilibrium CO Fourth-Positive and CN Violet emission in CO 2 –N 2 gases

Cited by 96 publications

References 39 publications

Venus Entry Flow over a Decomposing Aeroshell in X2 Expansion Tube

Venus Entry Flow over a Decomposing Aeroshell in X2 Expansion Tube

Radiative Heating During Mars Science Laboratory Entry: Simulation, Ground Test, and Flight

Blunt-Body Heating and Pressure Database from High-Enthalpy, CO2 Testing in an Expansion Tunnel

Contact Info

Product

Resources

About

Blunt-Body Heating and Pressure Database from High-Enthalpy, CO₂ Testing in an Expansion Tunnel