Mach reflection in detonations propagating through a gas with a concentration gradient

Ettner, F.; Vollmer, Klaus G.; Sattelmayer, Thomas

doi:10.1007/s00193-012-0385-8

Cited by 47 publications

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“…Ettner et al [4] performed Euler simulations of detonations in H 2 -air mixtures with transverse gradients. Curved multi-headed detonation fronts with a Mach-stem in the fuel-lean region were observed.…”

Section: Introductionmentioning

confidence: 99%

Detonation propagation in hydrogen–air mixtures with transverse concentration gradients

et al. 2015

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The influence of transverse concentration gradients on detonation propagation in H 2 -air mixtures is investigated experimentally in a wide parameter range. Detonation fronts are characterized by means of high-speed shadowgraphy, OH* imaging, pressure measurements, and soot foils. Steep concentration gradients at low average H 2 concentrations lead to single-headed detonations. A maximum velocity deficit compared to the Chapman-Jouguet velocity of 9 % is observed. Significant amounts of mixture seem to be consumed by turbulent deflagration behind the leading detonation. Wall pressure measurements show high local pressure peaks due to strong transverse waves caused by the concentration gradients. Higher average H 2 concentrations or weaker gradients allow for multi-headed detonation propagation.

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Section: Introductionmentioning

confidence: 99%

Detonation propagation in hydrogen–air mixtures with transverse concentration gradients

et al. 2015

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“…Such instabilities are characteristic of gas-phase detonations, and the question remains as to how the motions of these triple points affect the large-scale propagation and quenching behaviour of a detonation in a gradient. Preliminary work on this topic has been presented [29,30].…”

Section: Introductionmentioning

confidence: 99%

Gas-phase detonation propagation in mixture composition gradients

Kessler

Gamezo

Oran

2012

Phil. Trans. R. Soc. A.

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The propagation of detonations through several fuel-air mixtures with spatially varying fuel concentrations is examined numerically. The detonations propagate through twodimensional channels, inside of which the gradient of mixture composition is oriented normal to the direction of propagation. The simulations are performed using a twocomponent, single-step reaction model calibrated so that one-dimensional detonation properties of model low-and high-activation-energy mixtures are similar to those observed in a typical hydrocarbon-air mixture. In the low-activation-energy mixture, the reaction zone structure is complex, consisting of curved fuel-lean and fuel-rich detonations near the line of stoichiometry that transition to decoupled shocks and turbulent deflagrations near the channel walls where the mixture is extremely fuellean or fuel-rich. Reactants that are not consumed by the leading detonation combine downstream and burn in a diffusion flame. Detonation cells produced by the unstable reaction front vary in size across the channel, growing larger away from the line of stoichiometry. As the size of the channel decreases relative to the size of a detonation cell, the effect of the mixture composition gradient is lessened and cells of similar sizes form. In the high-activation-energy mixture, detonations propagate more slowly as the magnitude of the mixture composition gradient is increased and can be quenched in a large enough gradient.

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“…Further calculations showed that even if the hydrogen content on the bottom wall is reduced to zero, the maximum pressures observed there can still exceed those of the homogeneous mixture: the concentration gradient only needs to be strong enough to form a Mach stem. A simple method for predicting whether a detonation front in an inhomogeneous mixture develops a Mach stem can be found in [66].…”

Section: Resultsmentioning

confidence: 99%

Numerical Simulation of the Deflagration-to-Detonation Transition in Inhomogeneous Mixtures

Ettner¹,

Vollmer²,

Sattelmayer³

2014

Journal of Combustion

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In this study the hazardous potential of flammable hydrogen-air mixtures with vertical concentration gradients is investigated numerically. The computational model is based on the formulation of a reaction progress variable and accounts for both deflagrative flame propagation and autoignition. The model is able to simulate the deflagration-to-detonation transition (DDT) without resolving all microscopic details of the flow. It works on relatively coarse grids and shows good agreement with experiments. It is found that a mixture with a vertical concentration gradient can have a much higher tendency to undergo DDT than a homogeneous mixture of the same hydrogen content. In addition, the pressure loads occurring can be much higher. However, the opposite effect can also be observed, with the decisive factor being the geometric boundary conditions. The model gives insight into different modes of DDT. Detonations occurring soon after ignition do not necessarily cause the highest pressure loads. In mixtures with concentration gradient, the highest loads can occur in regions of very low hydrogen content. These new findings should be considered in future safety studies.

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Mach reflection in detonations propagating through a gas with a concentration gradient

Cited by 47 publications

References 13 publications

Detonation propagation in hydrogen–air mixtures with transverse concentration gradients

Detonation propagation in hydrogen–air mixtures with transverse concentration gradients

Gas-phase detonation propagation in mixture composition gradients

Numerical Simulation of the Deflagration-to-Detonation Transition in Inhomogeneous Mixtures

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