Dynamics of radiation in a CO:N2 mixture behind strong shock waves

Anokhin, E. M.; Ivanova, T. Yu.; Kudryavtsev, N. N.; Starikovskii, Andrei

doi:10.1134/s0018151x07060028

Cited by 9 publications

(4 citation statements)

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“…In 2008, a shock-tube campaign was carried out in the Moscow Institute of Physics and Technology (MIPT) under a contract from the European Space Agency (ESA). ,− The objective of the study was to validate the existing CFD tools employed in the design of the EXOMARS mission. Among the deployed diagnostics, a mercury lamp was used to measure the absorbance of the flow in the hot CO 2 (B → X) UV band around 253.7 nm.…”

Section: Resultsmentioning

confidence: 99%

Heavy Particle Impact Vibrational Excitation and Dissociation Processes in CO₂

2021

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A heavy particle impact vibrational excitation and dissociation model for CO2 is presented. This state-to-state model is based on the forced harmonic oscillator (FHO) theory, which is more accurate than current state-of-the-art kinetic models of CO2 based on first-order perturbation theory. The first excited triplet state 3B2 of CO2, including its vibrational structure, is considered in our model, and a more consistent approach to CO2 dissociation is also proposed. The model is benchmarked against a few academic zero-dimensional (0D) cases and compared to decomposition time measurements in a shock tube. Our model is shown to have reasonable predictive capabilities, and the CO2 + O ↔ CO + O2 reaction is found to have a key influence on the dissociation dynamics of CO2 shocked flows, warranting further theoretical studies. We conclude this study with a discussion on the theoretical improvements that are still required for a more consistent analysis of the vibrational/dissociation dynamics of CO2.

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Section: Resultsmentioning

confidence: 99%

Heavy Particle Impact Vibrational Excitation and Dissociation Processes in CO₂

2021

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“…Many comparisons with convective heating measurements have been performed to assess this model for convective heating predictions. 3 Although some comparisons with radiation measurements have been made recently using this model, [5][6][7][8][9][10] the experimental conditions were far from flight relevant and the main radiating band system, the CO 4th Positive band, was not measured. Recent measurements by Cruden et al 11 in the NASA Ames EAST facility have provided measurements of the CO 4th Positive and CN Violet bands at pressures and velocities relevant to HIAD entries.…”

Section: Introductionmentioning

confidence: 99%

Shock Layer Radiation Modeling and Uncertainty for Mars Entry

Johnston

Brandis

Sutton

2012

43rd AIAA Thermophysics Conference

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A model for simulating nonequilibrium radiation from Mars entry shock layers is presented. A new chemical kinetic rate model is developed that provides good agreement with recent EAST and X2 shock tube radiation measurements. This model includes a CO dissociation rate that is a factor of 13 larger than the rate used widely in previous models. Uncertainties in the proposed rates are assessed along with uncertainties in translational-vibrational relaxation modeling parameters. The stagnation point radiative flux uncertainty due to these flowfield modeling parameter uncertainties is computed to vary from 50 to 200% for a range of free-stream conditions, with densities ranging from 5e-5 to 5e-4 kg/m 3 and velocities ranging from of 6.3 to 7.7 km/s. These conditions cover the range of anticipated peak radiative heating conditions for proposed hypersonic inflatable aerodynamic decelerators (HIADs). Modeling parameters for the radiative spectrum are compiled along with a non-Boltzmann rate model for the dominant radiating molecules, CO, CN, and C2. A method for treating non-local absorption in the non-Boltzmann model is developed, which is shown to result in up to a 50% increase in the radiative flux through absorption by the CO 4th Positive band. The sensitivity of the radiative flux to the radiation modeling parameters is presented and the uncertainty for each parameter is assessed. The stagnation point radiative flux uncertainty due to these radiation modeling parameter uncertainties is computed to vary from 18 to 167% for the considered range of free-stream conditions. The total radiative flux uncertainty is computed as the root sum square of the flowfield and radiation parametric uncertainties, which results in total uncertainties ranging from 50 to 260%. The main contributors to these significant uncertainties are the CO dissociation rate and the CO heavy-particle excitation rates. Applying the baseline flowfield and radiation models developed in this work, the radiative heating for the Mars Pathfinder probe is predicted to be nearly 20 W/cm 2 . In contrast to previous studies, this value is shown to be significant relative to the convective heating.

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“…Measurements of the absolute radiation intensity in mixtures identical (with respect to their compositions) to the atmosphere pen etrated by a spacecraft are of great importance for both fundamental and applied studies. Presently, there exists only a limited number of experimental investi gations in which the intensity of the radiation flux beyond a strong shock front has been measured in absolute units [2][3][4].The results reported below significantly comple ment the bulk of experimental data available in the lit erature. These results also allow us to verify kinetic schemes and chemical reactions that proceed under the conditions of noticeable nonequilibrium existing beyond the strong shock front.…”

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confidence: 73%

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Measurement of the radiation intensity beyond the front of strong shock waves for a methane-nitrogen gas mixture

et al. 2011

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593Study of processes occurring beyond a strong shock front is an urgent problem inherent in the devel opment of projects aimed at space flights to objects of the solar system that possess an atmosphere. In order to save fuel, we have to use aerodynamic damping in the atmosphere. Thus, the right choice and adequate calculation of the thermal screen for a descending spacecraft become basic problems. When entrance into the upper layers of the atmosphere takes place, the shock wave arises ahead of the spacecraft. Under the conditions of high velocities and low gas densities, the radiation flux beyond the shock front can substantially contribute to the summary energy flux onto the ther mal screen surface [1].In the framework of the problem on optimizing the mass, shape, and material of the thermal screen, it is also important to calculate the radiation flux and to choose the least stressed input trajectory of a space craft in the atmosphere, which makes it possible to realize the necessary maneuver. Measurements of the absolute radiation intensity in mixtures identical (with respect to their compositions) to the atmosphere pen etrated by a spacecraft are of great importance for both fundamental and applied studies. Presently, there exists only a limited number of experimental investi gations in which the intensity of the radiation flux beyond a strong shock front has been measured in absolute units [2][3][4].The results reported below significantly comple ment the bulk of experimental data available in the lit erature. These results also allow us to verify kinetic schemes and chemical reactions that proceed under the conditions of noticeable nonequilibrium existing beyond the strong shock front.In order to perform experiments aimed at measure ments of the gas radiation intensity beyond the shock front, we used a shock tube composed of three parts. These were the high pressure chamber (HPC), the low pressure chamber (LPC), and the expansion vol ume. The chambers were separated by a 50 µm brass membrane, whereas the LPC was separated from the expansion volume by the output aluminum dia phragm. The internal LPC diameter and length were 77 mm and 5.5 m, respectively. Preliminarily, the LPC was pumped down to pressures of 5 × 10 -3 Torr and then was filled with the gas mixture under study up to the pressure required.The HPC was filled with a stoichiometric hydro gen-oxygen mixture up to a pressure of 3 atm. Then, with the use of helium and argon, summary pressure was elevated up to 10 atm. Once the mixture was inflamed, the brass membrane between the HPC and the LPC was broken, and the shock wave was formed in the gas under study. By variation of the helium to argon ratio in the HPC, we attained various shock wave velocities in the LPC. In the course of a given experimental series, the shock wave velocity equaled 8.3 km s -1 (for an initial pressure of 0.2 Torr in the LPC).Two piezoelectric pressure sensors were installed in the last two LPC sections to determine the shock wave velocity. There were also two quartz windows...

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Dynamics of radiation in a CO:N2 mixture behind strong shock waves

Cited by 9 publications

References 1 publication

Heavy Particle Impact Vibrational Excitation and Dissociation Processes in CO₂

Heavy Particle Impact Vibrational Excitation and Dissociation Processes in CO₂

Shock Layer Radiation Modeling and Uncertainty for Mars Entry

Measurement of the radiation intensity beyond the front of strong shock waves for a methane-nitrogen gas mixture

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Dynamics of radiation in a CO:N2 mixture behind strong shock waves

Cited by 9 publications

References 1 publication

Heavy Particle Impact Vibrational Excitation and Dissociation Processes in CO2

Heavy Particle Impact Vibrational Excitation and Dissociation Processes in CO2

Shock Layer Radiation Modeling and Uncertainty for Mars Entry

Measurement of the radiation intensity beyond the front of strong shock waves for a methane-nitrogen gas mixture

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Product

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Heavy Particle Impact Vibrational Excitation and Dissociation Processes in CO₂

Heavy Particle Impact Vibrational Excitation and Dissociation Processes in CO₂