The role of shock–flame interactions on flame acceleration in an obstacle laden channel

Ciccarelli, G.; Johansen, Craig T.; Parravani, Michael

doi:10.1016/j.combustflame.2010.05.003

Cited by 132 publications

(41 citation statements)

References 17 publications

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“…Through the experimental phenomenon, it is sure that, due to the low pressure in an open duct, the pressure drag in the upper duct without obstacle was small enough, which caused the flame front to pass over the obstacle fleetly. It was quite different from what was exhibited in the closed duct [9][10][11][12][13][14][15][16]. The flame shape turned to be sharp and the curvature became larger.…”

Section: Edc Modelmentioning

confidence: 65%

“…Lots of experimental and numerical investigations of flame vortexes induced by obstacle aimed at explaining the mechanisms responsible for its formation [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], including the experiment study on acceleration of flame front [12,15], overpressure [9,10,13,14,16], influence of blockage ratio [16], and obstacle shapes [9]. Flow field and reaction rate were also studied by numerical simulation [17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

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Premixed CH₄-Air Flame Structure Characteristic and Flow Behavior Induced by Obstacle in an Open Duct

Chen

Zhang

et al. 2014

Advances in Mechanical Engineering

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To study the fuel gas combustion hazards, the methane/air flame structure and flow characteristic in an open duct influenced by a rectangular obstacle were explored by experiment and realizable -model (RKE). In the test, the high-speed schlieren photography technology and dynamic detection technology were applied to record the flame propagation behavior. Meanwhile, the interaction between flame front and flame flow field induced by the obstacle was disclosed. In addition, the laminar-turbulence transition was also taken into consideration. The RKE and eddy dissipation concept (EDC) premixed combustion model were applied to obtain an insight into the phenomenon of flow change and wrinkle appearing, which potently explained the experimental observations. As a result, the obstacle blocked the laminar flame propagation velocity and increased pressure a little in an open duct. Some small-scale vortices began to appear near the obstacle, mainly due to Kelvin-Helmholtz instability (KHI), and gradually grew into large-scale vortices, which led to laminar-turbulent transition directly. The vortices thickened the reaction area and hastened the reaction rate; reversely, the higher reaction rate induced larger vortices. The RKE model result fitted the test data well and explained the wrinkle forming mechanism of two special vortices in the case.

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Section: Edc Modelmentioning

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Premixed CH₄-Air Flame Structure Characteristic and Flow Behavior Induced by Obstacle in an Open Duct

Chen

Zhang

et al. 2014

Advances in Mechanical Engineering

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“…Specifically, vorticity generated from the interaction of pressure waves with the density gradient in the reaction zone results in an enhancement of the burning rate (via enhanced mixing of fresh and product gases) that is required to achieve such high front velocities. The photographic evidence obtained by Ciccarelli et al [15] indicates that in the choking regime the final steady velocity is controlled by the interaction of the flamefront with the reflected shock waves coming off the obstacle face. For lower blockage obstacles (as in figure 2), the flame is able to propagate through the obstacle pair relatively unaffected by the converging reflected shock waves as seen in images 5-8.…”

Section: (B) Steady-state Propagation Regimesmentioning

confidence: 99%

“…Schlieren video of flame propagation in a 7.62 cm square channel with 2.54 cm high obstacles spaced at the channel height: (a) inter-frame time is 1.67 ms, (b) inter-frame time is 0.67 ms [15]. accessible 76.2 mm square channel with obstacles mounted on the top and the bottom surfaces have shown that there is a change in the propagation mechanism during flame acceleration from subsonic to supersonic velocities [14,15]. The obstacles are characterized by the flow blockage ratio (BR) defined as the ratio of the open area and the channel cross-sectional area.…”

Section: (A) Flame Acceleration In Obstructed Channelmentioning

confidence: 99%

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Explosion propagation in inert porous media

Ciccarelli

2012

Phil. Trans. R. Soc. A.

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Porous media are often used in flame arresters because of the high surface area to volume ratio that is required for flame quenching. However, if the flame is not quenched, the flow obstruction within the porous media can promote explosion escalation, which is a well-known phenomenon in obstacle-laden channels. There are many parallels between explosion propagation through porous media and obstacle-laden channels. In both cases, the obstructions play a duel role. On the one hand, the obstruction enhances explosion propagation through an early shear-driven turbulence production mechanism and then later by shock-flame interactions that occur from lead shock reflections. On the other hand, the presence of an obstruction can suppress explosion propagation through momentum and heat losses, which both impede the unburned gas flow and extract energy from the expanding combustion products. In obstacle-laden channels, there are well-defined propagation regimes that are easily distinguished by abrupt changes in velocity. In porous media, the propagation regimes are not as distinguishable. In porous media the entire flamefront is affected, and the effects of heat loss, turbulence and compressibility are smoothly blended over most of the propagation velocity range. At low subsonic propagation speeds, heat loss to the porous media dominates, whereas at higher supersonic speeds turbulence and compressibility are important. This blending of the important phenomena results in no clear transition in propagation mechanism that is characterized by an abrupt change in propagation velocity. This is especially true for propagation velocities above the speed of sound where many experiments performed with fuel-air mixtures show a smooth increase in the propagation velocity with mixture reactivity up to the theoretical detonation wave velocity.

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Experimental and Numerical Study of the Impact of Initial Turbulence on the Explosion Behavior of Methane‐Air Mixtures

Chen

2021

Chem Eng & Technol

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The experimental parameters that significantly affect the gas explosion process were determined, investigating the pressure, temperature, and velocity in the methane‐air explosion process under quiescent and turbulent conditions. Experiments and computational fluid dynamics simulations were integrated to optimize the experimental parameters and elucidate the impact of the initial turbulence on the explosion behavior of methane‐air mixtures. Good agreement was achieved between the computed results and experimental data. For a certain CH4 concentration within the explosive limit range, an initial turbulence can increase the maximum explosion pressure and the maximum rate of the pressure rise, shorten the time to reach the maximum explosion pressure and enhance the explosion strength and destructive power of CH4‐air mixtures. Turbulent flow can significantly broaden the explosive limits of CH4‐air mixtures. The ignition delay time affects the distribution of the initial turbulence and thus the extent and severity of the explosions.

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The role of shock–flame interactions on flame acceleration in an obstacle laden channel

Cited by 132 publications

References 17 publications

Premixed CH₄-Air Flame Structure Characteristic and Flow Behavior Induced by Obstacle in an Open Duct

Premixed CH₄-Air Flame Structure Characteristic and Flow Behavior Induced by Obstacle in an Open Duct

Explosion propagation in inert porous media

Experimental and Numerical Study of the Impact of Initial Turbulence on the Explosion Behavior of Methane‐Air Mixtures

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The role of shock–flame interactions on flame acceleration in an obstacle laden channel

Cited by 132 publications

References 17 publications

Premixed CH4-Air Flame Structure Characteristic and Flow Behavior Induced by Obstacle in an Open Duct

Premixed CH4-Air Flame Structure Characteristic and Flow Behavior Induced by Obstacle in an Open Duct

Explosion propagation in inert porous media

Experimental and Numerical Study of the Impact of Initial Turbulence on the Explosion Behavior of Methane‐Air Mixtures

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Product

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About

Premixed CH₄-Air Flame Structure Characteristic and Flow Behavior Induced by Obstacle in an Open Duct

Premixed CH₄-Air Flame Structure Characteristic and Flow Behavior Induced by Obstacle in an Open Duct