The role of spontaneous waves in the deflagration-to-detonation transition in submillimetre channels

Houim, Ryan W.; Ozgen, Alp; Oran, Elaine S.

doi:10.1080/13647830.2016.1249523

Cited by 49 publications

(14 citation statements)

References 33 publications

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“…It is known [12] that for a flame propagating in a tube with no-slip walls viscous dissipation in the flow ahead of the advancing flame heats the gas mixture increasing the temperature in the boundary layer by 150-200K higher than the gas temperature in the bulk flow near the tube axis. According to simulations of the flame propagating in submillimetre two-dimensional channels with a one-step model [49][50][51][52] viscous heating in the boundary layer induces local explosions near the boundary, which in turn leads to DDT. In simulations using a one-step model, this leads to the autoignition producing a spontaneous wave, which occurs during the time about 10 µs for submillimetre channels (about 60 µs for 2cm channel) that elapse between the passage of the precursor shock and the flame arrival.…”

Section: Discussionmentioning

confidence: 99%

Influence of chemical kinetics on spontaneous waves and detonation initiation in highly reactive and low reactive mixtures

Liberman

Wang

Qian

et al. 2018

Combustion Theory and Modelling

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Understanding the mechanisms of explosions is important for minimizing devastating hazards. Due to the complexity of real chemistry, a single-step reaction mechanism is usually used for theoretical and numerical studies. The purpose of this study is to look more deeply into the influence of chemistry on detonation initiated by a spontaneous wave. Results of high resolution simulations performed for one-step models are compared with simulations for detailed chemical models for highly reactive and low reactive mixtures. The calculated induction times for H2/air and for CH4/air are validated against experimental measurements for a wide range of temperatures and pressures. It is found that the requirements in terms of temperature and size of the hot spots, which produce a spontaneous wave capable to initiate detonation, are quantitatively and qualitatively different for one-step models compared to the detailed chemical models. The time and locations when the exothermic reaction affects the coupling between the pressure wave and spontaneous wave are considerably different for a one-step and detailed models. The temperature gradients capable to produce a detonation and the corresponding size of hot spots are much shallower and, correspondingly, larger than those predicted with one-step models. The impact of detailed chemical model is particularly pronounced for the methane-air mixture. In this case, not only the hot spot size is much greater than that predicted by a one-step model, but even at elevated pressure the initiation of detonation by a temperature gradient is possible only if the temperature outside the gradient is so high, that can ignite thermal explosion. The obtained results suggest that the one-step models do not reproduce correctly the transient and ignition processes, so that interpretation of the simulations performed using a one-step model for understanding mechanisms of flame acceleration, DDT and the origin of explosions must be considered with great caution.

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Section: Discussionmentioning

confidence: 99%

Influence of chemical kinetics on spontaneous waves and detonation initiation in highly reactive and low reactive mixtures

Liberman

Wang

Qian

et al. 2018

Combustion Theory and Modelling

View full text Add to dashboard Cite

show abstract

“…One mechanism involves viscous heating of the boundary layers in the flow induced by the precursor shock that forms ahead of the flame. The shock and viscous dissipation can heat the reactive material in the boundary layer to a condition where autoignition can occur in the time between the passage of the shock and the arrival of the flame [5][6][7][8]. Another mechanism involves localized pressure increases near the flame, which enhances the local burning rate, which, in turn, leads to further local pressure increases.…”

Section: Introductionmentioning

confidence: 99%

Experimental and theoretical observations on DDT in smooth narrow channels

Melguizo-Gavilanes

Ballossier

Faria

2021

Proceedings of the Combustion Institute

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A combined experimental and theoretical study of deflagration-to-detonation transition (DDT) in smooth narrow channels is presented. Some of the distinguishing features characterizing the late stages of DDT are shown to be qualitatively captured by a simple one-dimensional scalar equation. Inspection of the structure and stability of the traveling wave solutions found in the model, and comparison with experimental observations, suggest a possible mechanism responsible for front acceleration and transition to detonation.

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“…The channel had a diameter of 17.4 cm and blockage ratio br = 0.3 to match the experimental configuration of Kuznetsov [31]. Figure 6 shows reaction front position vs. reaction front speed for these simulations using FAST (Flame Acceleration Simulation Tool) [35], in which the mesh was dynamically refined around shocks, flame fronts and in regions of large gradients of density, pressure or composition. In addition to the simulation results, Fig.…”

Section: Comparison Between Ga-nm Graphical Approach and Experimentamentioning

confidence: 99%

Chemical-diffusive models for flame acceleration and transition-to-detonation: genetic algorithm and optimisation procedure

Kaplan

Ozgen

Oran

2018

Combustion Theory and Modelling

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One of the most important and difficult parts of constructing a multidimensional numerical simulation of flame acceleration and deflagration-to-detonation transition (DDT) in a reacting flow is finding a reliable and affordable model of the chemical and diffusive properties. For simulations of realistic scenarios, full detailed chemical models (with hundreds of chemical reactions and many species) are computationally prohibitive. In addition, they are usually inaccurate for high-temperature and high-pressure shock-laden flows. This paper presents a general approach for developing an automated procedure to determine the reaction parameters for a simplified chemical-diffusive model to simulate flame acceleration and DDT in stoichiometric methane-air and ethylene-oxygen mixtures. The procedure uses a combination of a genetic algorithm and Nelder-Mead optimization scheme to find the optimal reaction parameters for a reaction rate based on an Arrhenius form for conversion of reactants to products. The model finds six optimal reaction parameters (ratio of specific heats, activation energy, preexponential factor, heat release rate, thermal conductivity coefficient, and overall molecular weight) that reproduce six target flame and detonation properties (adiabatic flame temperature, constant volume equilibrium temperature, laminar flame speed, laminar flame thickness, Chapman-Jouguet detonation velocity, and detonation half-reaction thickness). Results from the optimization procedure show that the optimal reaction parameters, when used in 1-D reactive Navier-Stokes simulations, closely reproduce the target flame and detonation properties for the stoichiometric methane-air and ethylene-oxygen mixtures. The effects of uncertainties in the values of target flame and detonation properties can be minimized to have little effect on the resulting optimal reaction parameters, and the reaction parameters can be tailored, if necessary, for the different regimes of flame acceleration and DDT. When the reaction parameters are used as input in a 2-D simulation of flame acceleration and DDT in an obstacle-laden channel containing stoichiometric methane-air, the simulation results closely follow the transition to detonation observed in experiments. This automated procedure for finding parameters for a proposed reaction model makes it possible to simulate the behavior of flames and detonations in large, complex scenarios, which would otherwise be an incalculable problem.

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The role of spontaneous waves in the deflagration-to-detonation transition in submillimetre channels

Cited by 49 publications

References 33 publications

Influence of chemical kinetics on spontaneous waves and detonation initiation in highly reactive and low reactive mixtures

Influence of chemical kinetics on spontaneous waves and detonation initiation in highly reactive and low reactive mixtures

Experimental and theoretical observations on DDT in smooth narrow channels

Chemical-diffusive models for flame acceleration and transition-to-detonation: genetic algorithm and optimisation procedure

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