Experimental exploration of methane-coal dust explosion suppression by expandable graphite: From the point of view of pressure, flame, spectrum, and flow field

Expandable graphite (EG) has been proposed as a more efficient material for suppressing methane-coal dust explosions. The suppression effect was evaluated based on pressure, flame, spectrum, and flow field. The influence of particle size, expansion ratio, and suppressant concentration on the suppression effect was considered, and the suppression mechanism was analyzed. The explosion characteristics and OH* emission spectrum indicated that EG effectively suppressed methane-coal dust explosions. Higher concentrations, smaller particle sizes, and higher expansion ratios resulted in a stronger suppression effect. The influence of EG parameters on suppression effectiveness was ranked from highest to lowest in terms of the concentration, particle size, and expansion ratio. Schlieren imaging showed that EG can partially suppress the initial flame. However, the significant suppression effect occurs during the pressure-increase stage. The flow field was also analyzed using proper orthogonal decomposition. The results showed that EG suppressed flow-field fluctuations, with the mode coefficient trends aligned closely with the pressure-change curve.