Measurement and relationship between critical tube diameter and critical energy for direct blast initiation of gaseous detonations

Zhang, Bo; Ng, Hoi Dick; Lee, John H. S.

doi:10.1016/j.jlp.2013.07.011

Cited by 43 publications

(15 citation statements)

References 23 publications

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“…A high‐voltage electric spark was used to supply powerful initiation energy in our previous direct detonation initiation research . In this study, the spark energy (1/2 CV 2 ) generated by a slender coaxial electrode is 40 J, which is used to initiate all the mixtures and establish an identical ignition condition for all methane–air mixtures.…”

Section: Methodsmentioning

confidence: 99%

Explosion and flame characteristics of methane/air mixtures in a large‐scale vessel

Zhang

Chen

Xiu

et al. 2014

Process Safety Progress

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In this study, experiments of explosions and flame characteristics in methane/air mixtures are performed in a 10-m 3 vessel. Pressure gauges and a high-speed camera are utilized to record the pressure trajectories and the flame propagation process of ignition growth. The experimental results show that the maximum value of overpressure and the maximum rate of the explosion pressure rise are 0.596 MPa and 1.82 MPa/s for the methane (9.5% in volume)/air mixture at atmospheric conditions, respectively. Both values are higher than for other mixtures with different compositions. The results also indicate that the overpressure from the large-scale vessel in this study is lower than that of a smaller apparatus (e.g., 5-L closed cylindrical vessel). This difference occurs due to the cooling effect and because the reflected sonic disturbances by the vessel wall affect the explosion process and weaken the energy during the pressure attenuation stage, thus rendering the value of overpressure in the large-scale apparatus lower than in the tiny cylindrical vessels. The maximum overpressure is observed at 0.75 m for C 5 7% ("C" means the methane concentration) and 9.5% but at 1.3 m for C 5 5%, 6.5%, 11.2%, and 13%. These results indicate that methane/air is an easier means to generate overpressure and that the overpressure is higher near the stoichiometric condition. Based on the analysis of the flame propagation process, the mean value of the flame speed of methane (C 5 9.5%)/air is calculated to be approximately 2.43 m/s because the nonuniformity of the chemical reaction at the flame front results in a maximum fluctuation of flame speed of approximately 28.5%. The flame thickness (u) of methane (C 5 9.5%)/air fluctuates between 9.84 and 10.95 mm, with a mean value of 10.53 mm.

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Section: Methodsmentioning

confidence: 99%

Explosion and flame characteristics of methane/air mixtures in a large‐scale vessel

Zhang

Chen

Xiu

et al. 2014

Process Safety Progress

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“…Direct initiation of a detonation in a gas has been studied experimentally and theoretically [6][7][8]. Sufficiently large external energy addition at a timescale that is small relative to the acoustic timescale of the explosive mixture can result in a direct initiation of a detonation without first creating a measurable deflagration [16].…”

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Effect of decreasing blockage ratio on DDT in small channels with obstacles

Goodwin

Houim

Oran

2016

Combustion and Flame

116

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Multidimensional numerical simulations of an unconfined, homogeneous, chemically reactive gas were used to catalog interactions leading to the deflagration-to-detonation transition (DDT). The configuration studied was an infinitely long rectangular channel with regularly spaced obstacles containing a stoichiometric mixture of ethylene and oxygen, initially at atmospheric conditions and ignited in a corner with a small flame. The channel height is kept constant at 3200 µm and obstacle heights varied from 2560 µm to 160 µm to decrease the blockage ratio (br) from 0.8 to 0.05. The compressible reactive Navier-Stokes equations were solved by a high-order numerical algorithm on a locally adapting grid.The initially laminar flame develops into a turbulent flame with the creation of shocks, shock-flame interactions, shock-boundary layer interactions, a host of fluid and chemical-fluid instabilities, and DDT.Several different DDT mechanisms are observed as the br is reduced. For br in the range of 0.5 to 0.35, the shocks in the unburned material diffract over the obstacles and reflect against the channel wall, forming Mach stems that increase in strength with every obstacle traversed. Eventually, the Mach stem strength is sufficient for the unburned mixture to detonate after it reflects from an obstacle. For br outside of this range, DDT may occur either through Mach-stem reflection or through direct initiation due to shock focusing. Stochasticity of the turbulence leading to DDT in channels with low br is considered.

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“…In this direct initiation of detonation, detonation is formed instantaneously via the rapid deposition of a large amount of energy in a small volume of the combustible mixture. For direct initiation, the initiation source energy is the sole parameter governed success or failure of detonation initiation [17][18][19][20][21][22][23][24]. The detonation critical energy of the mixture provides important data for the characterization of the explosion sensitivity.…”

Section: Discussionmentioning

confidence: 99%

Detonation and deflagration characteristics of p-Xylene/gaseous hydrocarbon fuels/air mixtures

Zhang

Xiu

Chen

et al. 2015

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Measurement and relationship between critical tube diameter and critical energy for direct blast initiation of gaseous detonations

Cited by 43 publications

References 23 publications

Explosion and flame characteristics of methane/air mixtures in a large‐scale vessel

Explosion and flame characteristics of methane/air mixtures in a large‐scale vessel

Effect of decreasing blockage ratio on DDT in small channels with obstacles

Detonation and deflagration characteristics of p-Xylene/gaseous hydrocarbon fuels/air mixtures

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