Dissociated Carbon Dioxide Research Articles

Reacting gas-surface interaction and heat transfer characteristics for high-enthalpy and hypersonic dissociated carbon dioxide flow

Hypersonic carbon dioxide reacting gas-surface interaction occurs on the heat shield of high-speed Mars entry capsules, which has great influences on the heat transfer characteristics. Based on hypersonic reacting flow solver with complex surface thermochemistry, the hypersonic chemical non-equilibrium flow with oxygen/carbon gas mixture was numerically simulated, and the interaction between non-equilibrium flow and surface reactions was numerically analyzed to reveal the mechanism of aerodynamic heating from surface thermochemistry. Numerical results of catalytic effects show that the near-wall thermochemical behaviors are essentially dominated by the near-wall diffusion and chemical reactions. Various surface reactions alter the flow structure in the boundary layer, and generate different aerodynamic heating patterns. Results from ablating simulations indicate that the ablating surface can induce additional near-wall diffusion and injection energy though their influence on the thermal boundary layer structure is neglectably small. The modeling of reacting gas-surface interaction can be of benefit to promoting the fidelity and precision of aerodynamic heating with complex surface thermochemistry.

Effects of catalytic recombination on the surface of metals and quartz for the conditions of entry into the Martian atmosphere

Heat transfer to water-cooled surfaces of metals and quartz is studied experimentally in subsonic jets of dissociated carbon dioxide at a stagnation pressure of 80 hPa and enthalpy of 9 and 14 MJ/kg, corresponding to the descent conditions of the ExoMars space vehicle into the Martian atmosphere, using an RF induction plasmatron at the Institute for Problems in Mechanics, Russian Academy of Sciences. The measurements of heat fluxes to surfaces of different materials showed the significant effect of the catalytic properties of surfaces that can be arranged in the following descending order of the heat flux: silver, copper, stainless steel, quartz. The effect of strong modification of the silver surface is recorded during the tests; the maximum value of the heat flux is achieved after 15-min exposure of the surface to the jet. In the computational analysis of heat transfer, we used a two-parameter model of heterogeneous recombination of O atoms and CO molecules at the surface. With this model, the effective recombination coefficient of CO molecules is determined on the water-cooled surfaces of quartz and stainless steel, based on the experimental data on heat fluxes.

Correlation of the conditions of model heat transfer in underexpanded dissociated carbon dioxide jets and in hypersonic flow past a sphere in the Martian atmosphere

On the basis of the local modeling of heat transfer the parameters of supersonic flow past a cylindrical flat-nosed model in underexpanded dissociated carbon dioxide jets are recalculated to the case of spherical body entry into the Martian atmosphere on a wide range of the operating conditions of the VGU-4 plasmatron. The heat transfer parameters, similar in the experiment and hypersonic carbon dioxide flow past bodies are determined.

Flow and heat transfer in underexpanded nonequilibrium jets of carbon dioxide: Experiment and numerical simulation

The results of experimental and numerical investigations of heat transfer on a cylindrical model with a 10-mm-radius flat face in underexpanded jets of dissociated carbon dioxide under conditions of operating parameters of a 100 kW high-frequency plasmatron are presented.

Investigation of the Influence of Different Heterogeneous Recombination Mechanisms on the Heat Fluxes to a Catalytic Surface in Dissociated Carbon Dioxide

A kinetic model of heterogeneous recombination in dissociated carbon dioxide on high-temperature heat-shield coatings is developed; the model takes into account the nonequilibrium adsorption-desorption reactions of oxygen atoms and their recombination in the Eley-Rideal and Langmuir-Hinshelwood reactions. On the basis of a comparison of the calculated heat fluxes in dissociated carbon dioxide with those measured in the VGU-3 plasma generator of the Institute for Problems in Mechanics of the Russian Academy of Sciences (IPM RAS) and the available literature data, the parameters of the catalysis model are chosen for the glassy coating of the Buran orbiter tile heat shield based on the SiO2–B2O3–SiB4 system. The effects of heterogeneous recombination proceeding in accordance with the Langmuir-Hinshelwood mechanism, as well as the processes involving carbon atoms and those involving physically adsorbed oxygen atoms, on the heat fluxes to the glassy coating are analyzed on the surface temperature range from 300 to 2000 K.

Precursor radical recombination and its attendant effects on the surface of solids in a dissociated carbon dioxide medium

The atomic-hydrogen-initiated ejections of materials from the surface of solids (ZnS, Ni) preliminary treated with dissociated carbon dioxide are revealed. The glow of a crystalline phosphor and the dynamic effect of the reaction are observed in the dissociated carbon dioxide medium. It is found that the observed variations in the dynamic effect of the reaction are unrelated to changes in the reaction rate. These effects are used to elucidate the mechanism of heterogeneous radical recombination on the surface of solids (Al2O3, ZnS, Ni) in dissociated carbon dioxide. It is revealed that, under the experimental conditions, the reaction rate is independent of the chemisorbed radical concentration, because the reaction involves radicals entrapped into the precursor state with a short lifetime at the surface.

Study of Quartz Surface Catalycity in Dissociated Carbon Dioxide Subsonic Flows

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Modeling of the catalytic properties of high-temperature surface insulation in a dissociated carbon dioxide — Nitrogen mixture

A model of the heterogeneous catalysis of a dissociated carbon dioxide — nitrogen mixture on high-temperature heat-shield coatings is developed; the model takes into account nonequilibrium adsorption-desorption reactions of nitrogen and oxygen atoms and carbon dioxide molecules and their recombination in the Eley-Rideal reactions. On the basis of a comparison of the calculated heat fluxes in dissociated carbon dioxide with those measured on the VGU-4 plasma generator of the Institute for Problems in Mechanics of the RAS, the parameters of the catalysis model in question are chosen for three modern oxidant-resistant coating materials. The performances of these coatings are compared for the conditions of Mars Miniprobe entry into the Martian atmosphere. Their usability for the entry path considered is shown.

Erratum to Determination of the Effective Probabilities of Catalytic Reactions on the Surfaces of Heat Shield Materials in Dissociated Carbon Dioxide Flows

Erratum to Determination of the Effective Probabilities of Catalytic Reactions on the Surfaces of Heat Shield Materials in Dissociated Carbon Dioxide Flows

Determination of the Effective Probabilities of Catalytic Reactions on the Surfaces of Heat Shield Materials in Dissociated Carbon Dioxide Flows

The effect of heterogeneous catalysis on the heat transfer to cold and heated surfaces in subsonic dissociated carbon dioxide jet flows is studied experimentally, using a 100 kW inductive plasma generator, and simulated numerically. The effective probabilities of the heterogeneous reactions CO + O → CO2 and O + O → O2 on molybdenum (Tw=300 K) and quartz (Tw=470–620 K) surfaces, the Buran heat shield tile coating (Tw = 1470—1670 K), and two oxidation-resistant carbon-carbon coating materials (Tw=1420—1840 K) are determined by comparing the experimental and calculated data on the heat fluxes at the stagnation point of models at a pressure of 0.1 atm.

Drag measurements in a hypervelocity expansion tube

A technique is described for the measurement of aerodynamic drag in a hypervelocity expansion tube in which the test flow period may be as short as 50 μs. The technique is an application of the stress wave force balance first proposed by Sanderson and Simmons (1991). The experiments were conducted in a test flow of partially dissociated Carbon Dioxide where the flow speed was in excess of 7 kms−1. The validity of the technique is first demonstrated by comparing the forces measured on a range of sharp cones with those expected theoretically. Agreement to within 10% is achieved. Two re-entry type heat shield geometries were then tested with the experimental drag forces being compared with a Modified-Newtonian prediction. In both cases agreement to within 11% was obtained.

Recombination radiation from a nonequilibrium jet of dissociated carbon dioxide

Recombination radiation from a nonequilibrium jet of dissociated carbon dioxide

Decomposition of Carbon Dioxide by Ionizing Radiation. Part I

The irradiation of gaseous carbon dioxide with radon or in a nuclear reactor, produces about 0.1 percent decomposition of primarily dissociated carbon dioxide, correlating with previous results in the literature. The irradiation of solid carbon dioxide with radon produces carbon monoxide and oxygen with a G value of 9 to 10. The irradiation of gaseous carbon dioxide, containing a small amount of nitrogen dioxide, by radon or in a nuclear reactor, produced carbon monoxide and oxygen, with a G value of 9 to 10. Percentages as small as 0.5 percent of nitrogen dioxide are sufficient to stop the back reaction to carbon dioxide. A new mechanism has therefore been proposed for the ineffectual decomposition of carbon dioxide by ionizing radiation, and the effective decomposition when nitrogen dioxide is present. With the proposed mechanisms, the classical experiments of Lind, the carbon monoxide oxidation and the carbon monoxide decomposition, are quantitatively explained.