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

Abstract

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.

Modeling of Geometric Change Influence on Blast-Wave Propagation in Underground Airways Using a 2D-Transient Euler Scheme

“…Each scenario was repeated three times to increase accuracy. For detailed instruction of experimental instruments and procedure please refer to our previous work [13].…”

Coupling Analysis of the Flame Emission Spectra and Explosion Characteristics of CH4/C2H6/Air Mixtures

“…Many scholars have performed experimental and numerical research on the explosion parameters of premixed CH 4 /air. − Several studies show that the initial system temperature and pressure, , addition of inert gas, , contribution of other flammable gas, − geometries of confinement − and existence of obstacles − have great influence on the explosion behaviors of CH 4 , such as the minimum ignition energy, flammability limit, explosion pressure, flame propagation, and intermediate products. The P max and (d P /d t ) max are the two most significant indicators to assess the risks in industrial processes.…”