High-enthalpy test environments, flow modeling and in situ diagnostics for characterizing ultra-high temperature ceramics

Marschall, Jochen; Fletcher, Douglas G.

doi:10.1016/j.jeurceramsoc.2010.01.010

Cited by 38 publications

(13 citation statements)

References 61 publications

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“…Failure of these materials will be due to a combination of melting, vaporization, sublimation, oxidation, ablation, and spalling caused by the high temperatures and chemical attacks experienced [134]. Aerothermal testing has been conducted mostly on ZrB 2 -SiC composites [135][136][137][138][139] however some studies have also been conducted on HfB 2 [140], HfC [140,141], and TaC [142] based composites.…”

Section: Aerothermal Testingmentioning

confidence: 99%

Graphene NanoPlatelets Reinforced Tantalum Carbide consolidated by Spark Plasma Sintering

Nieto¹

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Section: Aerothermal Testingmentioning

confidence: 99%

Graphene NanoPlatelets Reinforced Tantalum Carbide consolidated by Spark Plasma Sintering

Nieto¹

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“…copper) as this approach is electrode-less as opposed to using arc jets in which particles from the electrodes are often found in the free stream. 1 The primary components of the facility are the power supply, plasma generation system and the test chamber. The power is supplied by an induction heating generator that can deliver up to 30 kW of energy.…”

Section: B Experimental Techniquementioning

confidence: 99%

“…The prolonged exposure to high temperature and chemical reactions can cause the TPS materials to fail. 1 The need to design a reliable TPS necessitates good understanding of the physical and chemical processes that determine the aerothermal heating environment.…”

mentioning

confidence: 99%

Computation of Surface Catalysis for Graphite Exposed to High-Enthalpy Nitrogen Flow

Anna

Boyd

2012

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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The high temperatures on a hypersonic vehicle surface caused by heat loads encountered during (re-)entry through a planetary atmosphere require a reliable Thermal Protection System (TPS) that makes a good understanding of the physical and chemical processes essential for its design. Surface catalysis is a crucial chemical process that directly impacts aerothermal heating of the vehicle TPS. To study the effects of this process, a binary catalytic atom recombination model is implemented in a computational fluid dynamics (CFD) code. The study examines the effects of surface catalysis for graphite exposed to high enthalpy nitrogen flow. As expected, surface catalysis strongly affects the boundary layer gradients of temperature and species concentration, and heat transfer to the surface. A fully catalytic surface causes the heat flux to increase by a factor of approximately 3.5. The physical accuracy of the model is assessed using data from experimental tests conducted in the Inductively Coupled Plasma (ICP) Torch Facility at the University of Vermont. Comparisons are presented of computed results with measured experimental data for translational temperature and relative nitrogen atom number density in the flow in front of the test article. NomenclatureD 12 binary diffusion coefficient between species 1 and 2 [m 2 /s] J sp species diffusion flux [kg/m 2 /s] M mass flux [kg/m 2 /s] N sp number of species in the mixture [dimensionless number] T translational-rotational temperature [K] Y mass fraction [dimensionless number] h sp species enthalpy [J/kg] k B Boltzmann constant k w wall catalytic speed [m/s] m particle mass [kg] q total heat flux [W/m 2 ] q conv convective heat flux [W/m 2 ] q dif f diffusive heat flux [W/m 2 ] γ wall catalytic efficiency [dimensionless number] κ thermal conductivity [W/m/K] ρ density [kg/m 3 ] subscripts w wall value tr translational-rotational energy mode ve vibrational-electronic energy mode ∞ reference freestream conditions sp species value * Graduate Student, Student Member AIAA. † James E. Knott Professor, Fellow AIAA.

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“…Therefore, such vehicles use a thermal protection system (TPS) that provides insulation from the severe aerodynamic heating encountered during hypersonic flight through a planetary atmosphere. The TPS is a single point-of-failure system, as the prolonged exposure to high temperature can cause the materials to fail [2,3]. The need to design a reliable TPS necessitates good understanding of the physical and chemical processes that determine the aerothermal heating environment.…”

mentioning

confidence: 99%

Numerical Analysis of Surface Chemistry in High-Enthalpy Flows

Anna

Boyd

2015

Journal of Thermophysics and Heat Transfer

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The effects of surface-chemistry processes of a graphite sample exposed to a subsonic high-enthalpy nitrogen flow are investigated using a coupled computational fluid-dynamics/surface-chemistry model. The results obtained are assessed for the accuracy of the model using experimental data from tests conducted in a 30 kW inductively coupled plasma torch facility at the University of Vermont. Significant discrepancies are observed between the computational and experimental results. Therefore, a study is performed to determine sensitivities of flow and surface parameters to variations in testing input conditions, as well as physical modeling parameters. Measurements of the absolute number density are required to draw firm conclusions about the surface-chemistry models, as well as the surface reactions involved.Nomenclature C k = concentration of gas species k, mol∕m 3 D k = diffusion coefficient of species k, m 2 ∕s E ad = energy barrier for adsorption, J∕mol E ER = energy barrier for Eley-Rideal recombination, J∕mol h = species enthalpy, J∕kg K = total number of species K g = total numbers of gas species K nb = number of species in bulk phase nb K ns;na = number of species in active site set na on surface phase ns k B = Boltzmann constant k fi , k bi = forward and backward reaction rates for reaction i M k = molar weight of species k, kg∕mol _ m b = mass blowing rate due to surface reactions, kg∕m 2 ∕s N = total number of phases N nb = number of bulk species N g , N s , N b = number of gas, surface, and bulk phases N ns;a = number of active site sets in surface phase ns N R = number of surface reactions P = pressure, Pa q = total heat flux, W∕m 2 q conv = convective heat flux, W∕m 2 q diff = diffusive heat flux, W∕m 2 R u = universal gas constant, J∕mol∕K r i;ns = reaction flux of reaction i on surface phase ns, mol∕m 2 ∕s S, S 0 = sticking coefficient T = translational-rotational temperature, K ν ki = net stoichiometric coefficient for species k in reaction i ν s = sum of the stoichiometric coefficients of all surface reactants ν k = thermal speed of gas-phase species k, m∕s ν 0 ki = reactant stoichiometric coefficient for species k in reaction i ν 0 0 ki = product stoichiometric coefficient for species k in reaction i _ w k = production rate of species k in all reactions, mol∕m 2 ∕s _ w ki = production rate of species k in reaction i, mol∕m 2 ∕s, Y = mass fraction Γ k = impingement flux of gas species k, m 2 ∕s γ = reaction efficiency θ ns;k = fraction of active sites occupied by species k on surface phase ns ρ = density, kg∕m 3 σ = Stefan-Boltzmann constant, W∕m 2 ∕K −4 Φ ns = active site density on surface phase ns, mol∕m 2 Φ ns;k = concentration of species k on surface phase ns, mol∕m 2 χ k = mole fraction of species k χ nb;k = mole fraction of bulk species k in bulk phase nb Subscripts b = bulk phase e = empty site g = gas phase na = number of active sites nb = number of bulk phases ns = number of surface phases s = surface phase tr = translational-rotational energy mode ve = vibrational-electronic energy mode...

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High-enthalpy test environments, flow modeling and in situ diagnostics for characterizing ultra-high temperature ceramics

Cited by 38 publications

References 61 publications

Graphene NanoPlatelets Reinforced Tantalum Carbide consolidated by Spark Plasma Sintering

Graphene NanoPlatelets Reinforced Tantalum Carbide consolidated by Spark Plasma Sintering

Computation of Surface Catalysis for Graphite Exposed to High-Enthalpy Nitrogen Flow

Numerical Analysis of Surface Chemistry in High-Enthalpy Flows

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