Effect of concentration and obstacles on flame velocity and overpressure of methane-air mixture

Wang, Cheng; Huang, Fenglei; Addai, Emmanuel Kwasi; Dong, Xinzhuang

doi:10.1016/j.jlp.2016.05.021

Cited by 56 publications

(12 citation statements)

References 15 publications

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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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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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“…Their results show that the speed of flame propagation will rapidly increase with obstacles, and the resulting shock wave may increase the power of gas explosion. Wang et al investigated the effect of concentration and obstacles on methane‐air mixture deflagration to detonation transition in a long duct. They found that the larger the obstacle blockage ratio, the stronger the interaction of the unburned mixture with a shock wave, which is highly beneficial for the acceleration of explosion flame.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of low‐concentration gas explosion in large‐scale pipeline

Zhang

Liu

et al. 2020

Energy Science & Engineering

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Low‐concentration gas is one of the most realistic and reliable supplementary or alternative energy sources of conventional natural gas, which has a wide range of applications. However, this gas is flammable and explosive during pipeline transportation and easily causes an explosion. In order to achieve safe transmission, the explosion characteristics and propagation law of low‐concentration gas are systematically studied through a large‐scale pipeline experimental system. We found that the peak pressure of low‐concentration gas explosion in pipeline has a quadratic function relationship with the propagation distance. Moreover, the peak pressure of gas explosion initially decreases from the explosion source, and then a turning point appears after a certain distance of propagation, which is followed by a sharp increase of peak pressure of gas explosion. The explosion pressure becomes maximum at the outlets of a pipeline. The arrival time of explosion flame is logarithmically relevant to propagation distance, while the speed of flame propagation gradually increases along with the increase of propagation distance. The flame propagation is faster at the exit point. In addition, the diameter of pipeline has also an important influence on the explosion propagation process of low‐concentration gas. So, the larger the diameter, the higher the explosion pressure. The explosion pressure of DN700 pipeline is obviously higher than that of DN500, and the explosion pressure rises faster; the speed of flame propagation of gas explosion in DN700 pipeline is also higher than that in DN500 pipeline. This study provides a theoretical reference for the prevention and control of explosion accidents in low‐concentration gas pipelines.

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“…As part of a wider assessment of the effects of obstacles on gas explosions, a number of experimental studies have established a strong influence of obstacle separation distance [3][4][5][6][7][8][9][10][11][12][13]. In most cases many repeat obstacles were spaced closely ranging from 1.3 to 10 obstacle scales, b.…”

Section: Introductionmentioning

confidence: 99%

Explosion flame acceleration over obstacles: Effects of separation distance for a range of scales

Na’inna

Phylaktou

Andrews

2017

Process Safety and Environmental Protection

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Effect of concentration and obstacles on flame velocity and overpressure of methane-air mixture

Cited by 56 publications

References 15 publications

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

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

Experimental study of low‐concentration gas explosion in large‐scale pipeline

Explosion flame acceleration over obstacles: Effects of separation distance for a range of scales

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