Mathematical modeling of heterogeneous detonation in gas suspensions of aluminum and coal-dust particles

Sci. China Phys. Mech. Astron.

Jiang

2013

Modeling aluminum (Al) dust detonation is difficult due to uncertainties in the product species and fractions. Recent experiments indicate both gaseous and solid alumina may appear in the detonation product, but only the gaseous one was considered before. To resolve this drawback, we study the effects of different product phases on the detonation parameters with the hybrid combustion model proposed recently. Numerical results demonstrate that the assumption of gaseous product induces high velocity and pressure, while the assumption of solid product induces low velocity and pressure. To clarify how close-to-experiment results have been obtained with one phase assumption, we revisit previous studies and analyze the models. The inconsistency between the product phase and heat release is found, and then one model with variable heat release dependent on the product phase is proposed. Then simulations with both the gaseous and solid products are carried out, and results reveal the necessity of establishing a relationship between the heat release and reaction products. Re s = two-phase Reynolds number t= time, s T= gas temperature, K T p =particle temperature, K u= gas velocity, m/s u p = particle velocity, m/s W i =molecular weight, g/mol x= distance, m = thermal conductivity of gas, W/(m·K) = bulk density of particle, kg/m 3  = dynamic viscosity coefficient, kg/(m·s) Teng H H, et al. Sci China-Phys Mech Astron November (2013) Vol. 56 No. 11 2179 v i = stoichiometric coefficient  = gas or particle density, kg/m 3

Section: Mathematical Model and Numerical Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of different product phases in aluminum dust detonation modeling

Sci. China Phys. Mech. Astron.

Jiang

2013

“…Papalexandris [13,14] developed a two-phase model by applying the classical theory of irreversible processes and the generalized concept of a low-Mach-number approximation. Federov et al [15,16] applied a non-equilibrium model of steady Al-oxygen detonations to calculate parameters for one-and two-dimensional cellular detonations. Recently, numerical simulation has become a very useful tool in dusty detonation research.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of one-dimensional aluminum particle–air detonation with realistic heat capacities

Jiang²

2013

Combustion and Flame

a b s t r a c t Aluminum (Al) particle-air detonation is very complicated because it includes multi-phase combustion phenomenon. Thus numerical simulations are often over-simplified. Here, the detonation is simulated by solving one-dimensional equations with more realistic heat capacities that vary with the dust mixture temperature. The effect on detonation parameters from the realistic heat capacities for the solid particles is investigated with a hybrid combustion model. The calculated results indicate that the detonation pressure, temperature and velocity vary significantly with changes in the heat capacity. Except for the velocity, these parameters are overestimated in numerical simulations when a constant heat capacity of the pre-shock mixtures is used. Furthermore, the realistic heat capacities have a strong effect on small diameter particles, but a weak effect on large diameter particles. Thus, when constant heat capacities are used, the combustion characteristic lengths are a function of the particle diameters with a power dependence of 1.77, whereas the power dependence decreases to 1.49 when realistic heat capacities are used. Moreover, if realistic heat capacities are applied, an ''abnormal'' strong detonation wave may appear in a dust mixture having large diameter particles. This phenomenon is consistent with the current combustion model, but it indicates that the value of heat released should also vary with the gas temperature in a fashion similar to that of the heat capacities.

“…Kand k 0 are chemical reaction constants. Following previous studies (Bazyn, Krier, Glumac 2006;Hayashi 2006, 2003;Briand, Veyssiere, Khasainov 2010;Brooks and Beckstead 1995;Fedorov and Fomin 1999;Fedorov, Fomin, Khmel' 2009;Fedorov, Khmel, Kratova 2008Lynch, Fiore, Krier et al 2010;Lynch, Krier, Glumac 2009;Papalexandris 2004aPapalexandris , 2004bPapalexandris , 2005Tanguay, Goroshin, Higgins et al 2009;Varsakelis and Papalexandris 2011;Veyssiere, Khasainov, Briand 2008;Zhang, Gerrard, Ripley 2009), the constants used in the chemical model are K ¼ 4 Â 10 6 s=m 2 , k 0 = 1.2 × 10 3 kg.m/mol.s, and E ¼ 71:7kJ=mol.…”

Section: Combustion Model and Numerical Methodsmentioning

confidence: 99%

“…The earliest two-phase model of the considered problem was proposed by . Fedorov et al (Fedorov and Fomin 1999;Fedorov, Fomin, Khmel' 2009;Fedorov, Khmel, Kratova 2008) developed a non-equilibrium model to calculate detonation parameters as well as both ideal and cellular detonation diffraction to reveal the special characteristics of dusty detonation. Papalexandris (Papalexandris 2004a(Papalexandris , 2004b(Papalexandris , 2005 Varsakelis and Papalexandris 2011) developed a two-phase model by applying the classical theory of irreversible processes, and examined the structure and stability of detonations in mixtures of gases and solid particles that were either combustible or inert.…”

mentioning

confidence: 99%

Cellular Aluminum Particle-Air Detonation Based on Realistic Heat Capacity Model

Xiang

Yang

Combustion Science and Technology

et al. 2019

Modeling aluminum (Al) particle-air detonation is extremely difficult because the combustion is shock-induced, and there are multi-phase heat release and transfer in supersonic flows. Existing models typically use simplified combustion to reproduce the detonation velocity, which introduces many unresolved problems. The hybrid combustion model, coupling both the diffused-and kinetics-controlled combustion, is proposed recently, and then improved to include the effects of realistic heat capacities dependent on the particle temperature. In the present study, 2D cellular Al particle-air detonations are simulated with the realistic heat capacity model and its effects on the detonation featured parameters, such as the detonation velocity and cell width, are analyzed. Numerical results show that cell width increases as particle diameter increases, similarly to the trend observed with the original model, but the cell width is underestimated without using the realistic heat capacities. Further analysis is performed by averaging the 2D cellular detonations to quasi-1D, demonstrating that the length scale of quasi-1D detonation is larger than that of truly 1D model, similar to gaseous detonations. ARTICLE HISTORY Aluminum (Al) particle-air detonations have many engineering applications, from catastrophic accident prevention to rocket propellant combustion (Bartlett, Ong, Fassell et al. 1963;Eckhoff 1993;Melcher, Krier, Burton 2002). The Al-air mixture detonation propagates similar to a gaseous detonation: its post-shock wave combustion produces intensive heat release followed by a sustained, strong leading shock. The Al particle is generally thought to vaporize first, however, which makes the combustion diffusion-controlledthis manner of combustion is characteristic of liquid fuel detonations, whereas gaseous fuel detonation is kinetics-controlled (Glassman, Yetter, Glumac 2014). Al-air detonation has several unique features, for example, Al particles are covered by an aluminum oxide (Al 2 O 3 ) shell affecting detonation ignition by generating solid combustion product Al 2 O 3 . These multi-phase interactions make Al combustion very complicated, resulting in many unresolved problems (Dreizin 2000;Zhang 2012).The chemical reaction time and length scales are much longer for heterogeneous postshock combustion than those for homogeneous combustion. It is very difficult to carry out dusty detonation experiments, so there have been relatively few Al-air detonation experiments reported in the literature (A J and Selman 1982;Borisov, Khasainov, Saneev et al.