Effect of scale on flame speeds of methane–air

Zhang, Q.; Pang, Lei; Zhang, S.X.

doi:10.1016/j.jlp.2011.06.021

Cited by 36 publications

(12 citation statements)

References 9 publications

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“…The effects of initial temperature in the experiments on the combustion pressure data for methane‐air mixtures have been reported in a previous article . Gieras et al .…”

Section: Introductionmentioning

confidence: 77%

“…The effects of initial temperature in the experiments on the combustion pressure data for methane-air mixtures have been reported in a previous article [3]. Gieras et al measured maximum explosion pressure, maximum rate of explosion pressure rise, lower explosion limit, upper explosion limit (UEL) of methane-air mixtures at normal and elevated temperatures [4].…”

Section: Introductionmentioning

confidence: 88%

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Ignition Characteristics for Methane‐Air Mixtures atVarious Initial Temperatures

Zhang

2013

Process Safety Progress

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This study was aimed at determining the effects of initial temperature on minimum ignition energy (MIE) and combustion parameters of methane‐air mixtures. A series experiments were carried out with an ignition energy measurement system and two combustion vessels (5 L and 20 L). The results described in this article include: (a) the MIE of methane‐air mixtures reached their lowest values at a concentration of 8.5%, instead of 9.5% stoichiometric concentration, (b) the MIE of methane‐air mixtures decreases as initial temperature increases, (c) the combustion temperature and maximum rate of combustion temperature rise of methane‐air mixtures decrease as initial temperature increases, and (d) the combustion pressure of methane‐air mixtures decreases as initial temperature increases. © 2013 American Institute of Chemical Engineers Process Saf Prog 32: 37–41, 2013

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“…The effects of initial temperature in the experiments on the combustion pressure data for methane‐air mixtures have been reported in a previous article . Gieras et al .…”

Section: Introductionmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 88%

Ignition Characteristics for Methane‐Air Mixtures atVarious Initial Temperatures

Zhang

2013

Process Safety Progress

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“…Accidental explosions often occur and cause casualties and severe property losses at industrial facilities, and they have received considerable attention in recent years in connection with the safety aspects of large‐scale transport and underground coal mines. Explosions represent the main type of accidents responsible for casualties in underground coal mines ; therefore, numerous researchers have contributed toward discovering the phenomena and the mechanisms of explosions .…”

Section: Introductionmentioning

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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“…However, the absolute mesh size changes with scaling factors; e.g., for a geometry when FLSF equals 2 and HDSF equals 4, the mesh size is 0.8 mm in the axial direction and a 1.6 mm by 1.6 mm cross-sectional dimension. The change of the absolute dimensions of cells will not cause considerable errors, which has been proven up to the scale of 1:100 (both longitudinal and horizontal) [4]. The combination of eight HDSFs The temporal discretization of the time duration for an appropriate time step size has significant influence on the calculation stability.…”

Section: Discretizationmentioning

confidence: 99%

Scale Effect of Premixed Methane-Air Combustion in Confined Space Using LES Model

et al. 2015

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Gas explosion is the most hazardous incident occurring in underground airways. Computational Fluid Dynamics (CFD) techniques are sophisticated in simulating explosions in confined spaces; specifically, when testing large-scale gaseous explosions, such as methane explosions in underground mines. The dimensions of a confined space where explosions could occur vary significantly. Thus, the scale effect on explosion parameters is worth investigating. In this paper, the impact of scaling on explosion overpressures is investigated by employing two scaling factors: The Gas-fill Length Scaling Factor (FLSF) and the Hydraulic Diameter Scaling Factor (HDSF). The combinations of eight FLSFs and five HDSFs will cover a wide range of space dimensions where flammable gas could accumulate. Experiments were also conducted to evaluate the selected numerical models. The Large Eddy Simulation turbulence model was selected because it shows accuracy compared to the widely used Reynolds' averaged models for the scenarios investigated in the experiments. Three major conclusions can be drawn: (1) The overpressure increases with both FLSF and HDSF within the deflagration regime; (2) In an explosion duct with a length to diameter ratio greater than 54, detonation is more likely to be triggered for a stoichiometric methane/air mixture; (3) Overpressure increases as an increment hydraulic diameter of a geometry within deflagration regime. A relative error of 7% is found when predicting blast peak overpressure for the base case compared to the experiment; a good agreement for the wave arrival time is also achieved.

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Effect of scale on flame speeds of methane–air

Cited by 36 publications

References 9 publications

Ignition Characteristics for Methane‐Air Mixtures atVarious Initial Temperatures

Ignition Characteristics for Methane‐Air Mixtures atVarious Initial Temperatures

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

Scale Effect of Premixed Methane-Air Combustion in Confined Space Using LES Model

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