Influence of Cavity Width and Powder Filling in a Cavity on Overpressure Evolution Laws and Flame Propagation Characteristics of Methane/Air Explosion

Abstract

Passive explosion suppression remains an indispensable auxiliary method for gas explosion suppression due to its low cost. To explore a new type of explosion passive suppression technology, three rectangular cavities with different width-diameter ratios were designed and laid in a large-scale methane/air explosion experiment system, and its explosion suppression performance was evaluated by measuring the changes in the explosion flame and shock wave before and after passing through the cavity. The results show that the suppression effect of the cavity is affected by its width. The larger the width-diameter ratio, the faster the attenuation of the flame and shock wave. The cavity-combined aluminum hydroxide powder effectively improves the suppression effect. When the filling amount of the powder is 140 g, the flame is quenched. However, there is an optimal powder filling degree for the suppression of the shock wave in the limited space of the cavity. In the test range, the maximum decay rate of the overpressure and impulse are 49.4 and 39.4%, respectively. This study can provide theoretical guidelines for the suppression of gas explosion.

Figure 1

Schematic diagram of the gas explosion experiment system.

Figure 2

Rectangular cavity.

Figure 3

Photograph of the experimental system.

Figure 4

Flame signal at each measuring point under different conditions: (a) without a cavity, (b) with a cavity of 300 mm width, (c) with a cavity of 500 mm width, and (d) with a cavity of 800 mm width.

Figure 5

Overpressure curve at each measuring point under different conditions: (a) without a cavity, (b) with a cavity of 300 mm width, (c) with a cavity of 500 mm width, and (d) with a cavity of 800 mm width.

Figure 6

Maximum overpressure and decay rate under different experimental conditions.

Figure 7

Impulse and decay rate under different experimental conditions.

Figure 8

Schematic diagram of shock wave propagation.

Figure 9

Model of shock wave propagation at the section of variable width: (a) propagation diagram, (b) propagation equivalent diagram, and (c) propagation simplification diagram.

Figure 10

Particle size distributions of aluminum hydroxide.

Figure 11

Flame signal information when the cavity is filled with 120 g of powder.

Figure 12

Flame speed under different experimental conditions.

Figure 13

Maximum overpressure and decay rate under different experimental conditions.

Figure 14

Impulse and decay rate under different experimental conditions.

Figure 15

Internal environment of the cavity filled with aluminum hydroxide powder after explosion.

Figure 16

Thermal analysis results of aluminum hydroxide.