Shock transition to detonation in channels with obstacles

Goodwin, Gabriel B.; Houim, Ryan W.; Oran, Elaine S.

doi:10.1016/j.proci.2016.06.160

Cited by 67 publications

(21 citation statements)

References 23 publications

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“…Currently, it is computationally very expensive to conduct high-resolution multi-dimensional detonation simulations solving the NS equations with detailed chemistry. The Arrhenius law that relates chemical reaction rates to temperature variation is widely used as the simplest mode for detonation simulations [24][25][26][27]. Here the reaction model is selected and fitted to the physical parameters of a H2/O2 detonation initially at 300 K T  and 6.67 kPa P  [20].…”

Section: Governing Equationsmentioning

confidence: 99%

Dynamic detonation stabilization in supersonic expanding channels

et al. 2019

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Section: Governing Equationsmentioning

confidence: 99%

Dynamic detonation stabilization in supersonic expanding channels

et al. 2019

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“…As shown below, however, flame acceleration and DDT are complex processes, and, in this section, we examine if one set of optimal reaction parameters is consistent or correct for the whole evolution of the flow. Goodwin et al [33,34] have simulated DDT in long rectangular channels containing a mixture of stoichiometric ethylene-air. The channel contained regularly spaced obstacles and the simulations were used to quantify the effects of decreasing the blockage ratio of those obstacles on the DDT mechanism [33].…”

Section: Evaluation Of Optimal Reaction Parameters In a Fluid-dynamicmentioning

confidence: 99%

“…The channel contained regularly spaced obstacles and the simulations were used to quantify the effects of decreasing the blockage ratio of those obstacles on the DDT mechanism [33]. Details of the computational geometry and simulation conditions can be found in [33,34]. Figure 4 shows a sequence of temperature images from a simulation in which the obstacle blockage ratio is 0.5.…”

Section: Evaluation Of Optimal Reaction Parameters In a Fluid-dynamicmentioning

confidence: 99%

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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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“…It should be noted that the DDT process is very complex and transient, and the complex mechanism cannot be observed in experiments. Numerical simulations have been done extensively in recently years [12][13][14][15][16] , but the mechanism is still unknown.…”

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confidence: 99%

Theoretical analysis on deflagration-to-detonation transition

et al. 2018

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The study on deflagration-to-detonation transition (DDT) is very important because this mechanism has relevance to safety issues in industries, where combustible premixed gases are in general use.However, the quantitative prediction of DDT is one of the major unsolved problems in combustion and detonation theory to date. In this paper, the DDT process is studied theoretically and the critical condition is given by a concise theoretical expression. The results show that a deflagration wave propagating with about 60% Chapman-Jouguet (C-J) detonation velocity is a critical condition. This velocity is the maximum propagating velocity of a deflagration wave and almost equal to the sound speed of combustion products. When this critical conation is reached, a C-J detonation is triggered immediately. This is the quantitative criteria of the DDT process.It is generally known that combustion waves propagating in a premixed detonable mixture can be classified into two modes, either deflagration or detonation. The detonation wave is initiated by two ways, one is direct initiation, and the other is deflagration-to-detonation transition (DDT). The direct detonation initiation needs extremely high ignition energy supplied to the premixed detonable mixture. Once the detonation is initiated directly, it will propagate self-sustainable with a Chapman-Jouguet (C-J) detonation velocity.Most of the detonation initiation is imitated by the DDT process. The flame is ignited by a small amount of energy at the initial stage and then the flame front is accelerated by natural or artificial reasons from laminar flame with velocities at the level of some meters per second to turbulent flame with speeds at the level of a hundred meters per second. Under certain critical conditions, the DDT process can occur and the C-J detonation is triggered immediately. There is a critical threshold inherent in the DDT process. Sufficient evidence from the previous studies

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Shock transition to detonation in channels with obstacles

Cited by 67 publications

References 23 publications

Dynamic detonation stabilization in supersonic expanding channels

Dynamic detonation stabilization in supersonic expanding channels

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

Theoretical analysis on deflagration-to-detonation transition

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