HTFFR kinetics studies of Al+CO2→AlO+CO from 300 to 1900 K, a non-Arrhenius reaction

Fontijn, Arthur; Felder, W.

doi:10.1063/1.434986

Cited by 82 publications

(23 citation statements)

References 32 publications

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“…Under conditions of 10 1 -10 2 atm and 1-50 m particles, however, it has been found that the burning rate of aluminum particles is greater than that in 1 atm air, thus resulting in a dependence on pressure but a smaller power n between 1 and 2 [7][8][9][10][11]. For the combustion of Al particles smaller than 30 m, even under atmospheric conditions, the diffusion theory could lead to an overprediction of the burning rate [12][13][14]. The power n < 2 implies the contribution of finite chemical kinetics and possibly convective flow effects [5].…”

Section: Introductionmentioning

confidence: 98%

Reaction Mechanism of Aluminum-Particle-Air Detonation

Zhang

Gerrard

Ripley

2009

Journal of Propulsion and Power

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Both in-tube and unconfined experimental evidence showed strong dependence of micrometric aluminum-air detonability on initial pressure and highly nonlinear behavior of abrupt deflagration-to-detonation transition, thus indicating dependence of the aluminum reaction mechanism of the detonation waves on chemical kinetics. On the other hand, the observed aluminum-air detonation manifested itself in a weak transverse wave structure, as revealed by the small-amplitude oscillation that rapidly degenerates behind the shock front in the pressure histories. This suggests a functional dependence that is weaker than the nonlinear Arrhenius kinetic behavior for the later aluminum combustion. Hence, a surface kinetic oxidation and diffusion hybrid reaction model with a degree of condensed detonation products was suggested, and the unsteady two-phase fluid dynamics modeling showed the success of the hybrid reaction model, capable of capturing both the kinetics-limited transient processes of detonation initiation, abrupt deflagration-to-detonation transition and detonation instability, and the diffusion-limited combustion of aluminum in the long reaction zone, supporting the weak transverse wave structure.Nomenclature a e = equilibrium sound speed, m=s a g = phase-frozen sound speed, m=s C = mole concentration, mol=m 3 C D = drag coefficient D = detonation velocity, m=s D g = gas-phase diffusivity, m 2 =s d p = particle diameter, m E = activation energy, J=mol e = specific internal energy, J=kg f p = rate of momentum transfer between the solid and the gas phase, N=m 3 J p = rate of mass transfer between the particles and the gas phase, kg=m 3 s K = diffusion reaction coefficient, s=m 2 k = mass depletion flux, kg=m 2 s k d = rate coefficient of diffusion reaction, kg m=mol s k s = rate coefficient of kinetic reaction, kg m=mol s k 0 = kinetic reaction coefficient, kg m=mol s L b = latent heats of evaporation, J=mol L m = latent heats of melting, J=mol Nu = Nusselt number n p = particle number density, 1=m 3 Pr = gas-phase Prandtl number p = pressure, N=m 2 Q p = rate of heat transfer between the particles and the gas phase, J=m 3 s q p = heat release of particles, J=kg R = universal gas constant, J=mol K Re = two-phase Reynolds number r p = particle radius, m T = temperature, K T ign = particle ignition temperature, K t b = particle burning time, s u = flow velocity, m=s W = molecular weight, g=mol w = species reaction rate, kg=m 3 s x = distance in the shock-propagation direction, m Y = mass fraction of species g = thermal conductivity of the gas phase, W=m K = stoichiometric coefficient = material density, kg=m 3 = partial density or mass concentration, kg=m 3 = volume fraction p = rate of particle number production, 1=m 3 s Subscripts g = gas-phase index oxi = index for oxidizing gases p = particle-phase index s = index for particle surface 0 = initial state

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Section: Introductionmentioning

confidence: 98%

Reaction Mechanism of Aluminum-Particle-Air Detonation

Zhang

Gerrard

Ripley

2009

Journal of Propulsion and Power

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“…The existence of diffusion micro-flames around the particles leads to local micro-gradients of aluminum vapor concentration and temperature within the suspension. The high reactivity of aluminum vapor with various oxidizers [34,35], generally prevents the formation of a premixed aluminum-oxidizer mixture, such that the aluminum vapor can only exist in the bulk gas of a fuel-rich mixture once the oxidizer has been nearly consumed. For nearly stoichiometric mixtures, a small amount of aluminum vapor forms due to natural dissociation process of aluminum sub-oxides at high temperatures.…”

Section: Al Emission Self-reversal and The Regime Of Combustion In Thmentioning

confidence: 99%

Emission and laser absorption spectroscopy of flat flames in aluminum suspensions

Soo

Goroshin

Glumac

et al. 2017

Combustion and Flame

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Imaging emission spectroscopy, spatially resolved laser-absorption spectroscopy, and particle image velocimetry (PIV) are applied to a flat flame stabilized in a suspension of micron-sized aluminum. The results from the combination of diagnostics are used to infer the combustion regime of the particles and to estimate the characteristic combustion time of the suspension. It is observed that the reaction zone of the flame in stoichiometric aluminumair suspensions exhibits strong self-reversal of the atomic aluminum emission lines. These lines also exhibit high optical depths in both emission and absorption spectroscopy. The strong self-reversal and high optical depths indicate high concentrations of aluminum vapor within the reaction zone of the flame at multiple temperatures. These features provide evidence of the formation of vapor-phase micro-diffusion flames around the individual particles in the suspension. In aluminum-methane-air flames, the lack of self-reversal and lower optical depths of the aluminum atomic lines indicate the absence of vapor-phase micro-diffusion flames, and point to a more heterogeneous, and likely kinetically-controlled, particle combustion regime. The reaction zone thickness is estimated from the spatially resolved profiles of aluminum resonance lines in both absorption and emission through the flame. The emission measurements yield a reaction zone thickness on the order of 1.7±0.3 mm in aluminum-air flames, and the absorption measurements yield a thickness on the order of 2.3±0.5. It is demonstrated that the combination of the combustion zone thickness measurement, flame temperatures determined from molecular AlO emission spectra, and particle velocity measurements from the PIV diagnostic permits an estimation of the burning time in the suspension. The burning time in stoichiometric aluminum-air suspensions using the suite of diagnostics is estimated to be on the order of 0.7 milliseconds.

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“…The condensation reactions occurred in a thin zone whose location was determined by specification of a condensation temperature. Experimental kinetic data [49] were used for the gas-phase reaction, and all other reactions were assumed to be infinitely fast. It was shown that the use of finite kinetics leads to the lower than 2 exponent in a power law for the particle-size dependence of the burning time, observed for Al by many authors [63].…”

Section: Modelingmentioning

confidence: 99%