High-speed flames and DDT in very rough-walled channels

Ciccarelli, G.; Johansen, Craig T.; Kellenberger, Mark

doi:10.1016/j.combustflame.2012.08.009

Cited by 33 publications

(11 citation statements)

References 5 publications

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“…The present methodologies (Ciccarelli and Dorofeev, 2008;Ciccarelli et al, 2013;Ivanov et al, 2011;Oran and Gamezo, 2007;Petchenko et al, 2007;Pinos and Ciccarelli, 2015;Starr et al, 2015;Zipf et al, 2014) for studying the interaction mechanism between the flame and shock wave usually involve experiments and simulations in long tubes, which can generate the turbulent flame and make flame acceleration to trigger the shock wave and even detonation. For a freely expanding flame, the initially smooth surface of the flame is wrinkled due to Darrieus-Landau instability with thermal diffusion effect.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Turbulent Flame Propagation and Pressure Oscillation in a Constant Volume Chamber Equipped With an Orifice Plate

Wei

Gao

Zhou

et al. 2017

Combustion Science and Technology

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In this work, the main contribution is an understanding of different combustion phenomena involving flame acceleration, flame propagation, and the pressure oscillation resulting from flameshock interactions. These physical phenomena were experimentally studied using a newly developed confined combustion chamber equipped with one or two orifice plates. The results showed that there are five stages of flame propagation when a laminar flame passes through the orifice plate in a confined space. These include the deceleration of the laminar flame, jet flame formation and rapid acceleration, deceleration of the flame, turbulent flame formation and acceleration, and turbulent flame propagation in the end-gas region. Flame acceleration and pressure oscillation were found to be strongly related to the aperture size of the orifice plate. The high amplitudes of pressure oscillations were found to be the results of two combustion mechanisms: the end gas auto-ignition and the interactions between the accelerated turbulent flame and shock wave. To further accelerate the flame and promote stronger disturbance in the end gas, another identical orifice plate was employed. Subsequently, strong flame-shock interaction caused end-gas auto-ignition with an extremely high-amplitude pressure oscillation. Eventually, the maximum amplitude of pressure oscillation exceeded 8 MPa as end-gas auto-ignition occurred in the end region of the combustion chamber.

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Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Turbulent Flame Propagation and Pressure Oscillation in a Constant Volume Chamber Equipped With an Orifice Plate

Wei

Gao

Zhou

et al. 2017

Combustion Science and Technology

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“…It is also difficult to account for these waves as a diffusionless phenomenon alone, since the auto-ignition delay in the gas compressed by the shock is not compatible with the reaction wave propagation, unless strong temperature fluctuations are present to trigger local ignition kernels (hot spots) with ignition delays compatible with the observed reaction wave propagation [5,6]. Based on indirect and often speculative experimental observations, it is believed that these fast deflagration velocities are maintained via the action of pressure waves within this deflagration complex (see [3] and references to earlier work by Lee and his collaborators [7]). These transverse pressure waves are believed to contribute to the increase of the level of turbulent mixing by the Richtmyer-Meshkov instability, similar to the action of transverse waves in highly unstable cellular detonations.…”

Section: Introductionmentioning

confidence: 99%

Influence of hydrodynamic instabilities on the propagation mechanism of fast flames

Maley

Bhattacharjee

Lau-Chapdelaine

et al. 2015

Proceedings of the Combustion Institute

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The present work investigates the structure of fast supersonic turbulent flames typically observed as precursors to the onset of detonation. These high speed deflagrations are obtained after the interaction of a detonation wave with cylindrical obstacles. Two mixtures having the same propensity for local hot spot formation were considered, namely hydrogen-oxygen and methane-oxygen. It was shown that the methane mixture sustained turbulent fast flames, while the hydrogen mixture did not. Detailed high speed visualizations of nearly two-dimensional flow fields permitted to identify the key mechanism involved. The strong vorticity generation associated with shock reflections in methane permitted to drive jets. These provided local enhancement of mixing rates, sustenance of pressure waves, organization of the front in stronger fewer modes and eventually the transition to detonation. In the hydrogen system, for similar thermo-chemical parameters, the absence of these jets did not permit to establish such fast flames. This jetting slip line instability in shock reflections (and lack thereof in hydrogen) was correlated with the value of the isentropic exponent and its control of Mach shock jetting instability (Mach & Radulescu).

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“…Turbulence acts as a perturbing force, increasing the flame surface and the overall burning rate. Channels with rough walls and obstacles are often used to study DDT, since in this case the run-up distance is better controlled [21][22][23][24]. This was presumably the reason why the first attempts to explain DDT were heavily based on the assumption that DDT might occur only if the flame becomes turbulent, and that turbulence is the primary reason for the flame acceleration.…”

Section: Is Ddt the Only Possible Way To Explain Unconfined Dust Explmentioning

confidence: 99%

Multipoint radiation induced ignition of dust explosions: turbulent clustering of particles and increased transparency

Liberman

Kleeorin

Haugen

2018

Combustion Theory and Modelling

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It is known that unconfined dust explosions consist of a relatively weak primary (turbulent) deflagrations followed by a devastating secondary explosion. The secondary explosion may propagate with a speed of up to 1000 m/s producing overpressures of over 8-10 atm. Since detonation is the only established theory that allows a rapid burning producing a high pressure that can be sustained in open areas, the generally accepted view was that the mechanism explaining the high rate of combustion in dust explosions is deflagration to detonation transition. In the present work we propose a theoretical substantiation of the alternative propagation mechanism explaining origin of the secondary explosion producing the high speeds of combustion and high overpressures in unconfined dust explosions. We show that clustering of dust particles in a turbulent flow gives rise to a significant increase of the thermal radiation absorption length ahead of the advancing flame front. This effect ensures that clusters of dust particles are exposed to and heated by the radiation from hot combustion products of large gaseous explosions sufficiently long time to become multi-point ignition kernels in a large volume ahead of the advancing flame front. The ignition times of fuel-air mixture by the radiatively heated clusters of particles is considerably reduced compared to the ignition time by the isolated particle. The radiation-induced multi-point ignitions of a large volume of fuel-air ahead of the primary flame efficiently increase the total flame area, giving rise to the secondary explosion, which results in high rates of combustion and overpressures required to account for the observed level of overpressures and damages in unconfined dust explosions, such as e.g. the 2005 Buncefield explosion and several vapor cloud explosions of severity similar to that of the Buncefield incident.

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High-speed flames and DDT in very rough-walled channels

Cited by 33 publications

References 5 publications

Experimental Investigation of Turbulent Flame Propagation and Pressure Oscillation in a Constant Volume Chamber Equipped With an Orifice Plate

Experimental Investigation of Turbulent Flame Propagation and Pressure Oscillation in a Constant Volume Chamber Equipped With an Orifice Plate

Influence of hydrodynamic instabilities on the propagation mechanism of fast flames

Multipoint radiation induced ignition of dust explosions: turbulent clustering of particles and increased transparency

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