No abstract

It is pointed out in the literature that the vacuum chamber has the effect of explosion suppression. The effect of explosion suppression depends on the volume of the vacuum chamber, while the vacuum degree has little effect on the performance of explosion suppression. Inspired by this, to explore a new method of gas explosion suppression, a rectangular steel cavity with a wall thickness of 10 mm, a length of 500 mm, a width of 800 mm, and a height of 200 mm was designed. The cavity was installed in a pipeline system to carry out experimental research and to investigate the law of attenuation of gas explosion flames and shock wave overpressure after passing through the cavity. The results show that the single cavity has the function of flame-out and wave attenuation, which attenuates the explosion flame and shock wave overpressure by 42.5% and 11%, respectively, and that the dual cavity further improves the performance of flame-out and wave attenuation, which attenuates flame and shock wave overpressure by 75.4% and 26.7%, respectively. On the basis of the experimental study, a numerical model was established, and a numerical simulation was carried out under the same conditions as the experimental study. The results show that the single cavity inhibits the propagation of the shock wave and attenuates the shock wave overpressure by 10.61%. The dual cavity further improves the suppression performance and attenuates the shock wave overpressure by 28.88%. Finally, by simulating the propagation process of the gas explosion shock wave and flame in the cavity, the mechanism of inhibiting gas explosion propagation by the cavity structure is analyzed.

This study aimed to investigate the influence of cavity width on the attenuation characteristic of gas explosion wave. Attenuation mechanism of gas explosion wave through cavity was obtained by numerical simulation. The gas explosion shock wave energy can be greatly attenuated through the cavity structure in five stages, namely, plane wave, expansion, oblique reflection, Mach reflection, and reflection stack, to ensure that it is eliminated. Cavities with various width sizes, namely, 500   ∗ 300   ∗ 200, 500   ∗ 500   ∗ 200, and 500   ∗ 800   ∗ 200 (length   ∗ width   ∗ height, unit: mm), were experimented to further investigate the attenuation characteristics through a self-established large-size pipe gas explosion experimental system with 200 mm diameter and 36 m length. Results showed an evident attenuation effect on flame duration light intensity (FDLI) and peak overpressure with increasing cavity width. Compared with 300 mm, the overall FDLI decreased by 83.0%, and the peak overpressure decreased by 71.2% when the cavity width was 800 mm. The fitting curves of the FDLI and peak overpressure attenuation factors to width-diameter demonstrated that the critical width-diameter was 2.19 when the FDLI attenuation factor was 1. The FDLI attenuation factor sharply decreased at the width-diameter ratio range from 1.5 to 2.5 and basically remained steady at 0.17 at the width-diameter ratio range from 2.7 to 4.0. The peak overpressure attenuation factor gradually decreased with the increase of width-diameter ratio and changed from 0.93 to 0.28 with width-diameter ratio from 1.5 to 4.0. The research results can serve as a good reference for the design of gas explosion wave-absorbing structures.

The essence of both rockburst and coal and gas outburst lies in fast energy release. In order to explore the energy action mechanism of coal and gas outburst induced by rockburst in rockburst and coal and gas outburst combined mines, the split Hopkinson pressure bar (SHPB) experimental device was firstly used to conduct uniaxial impact failure test of coal specimens prone to outburst under different strain rates, and their energy dissipation laws under impact loading were obtained. Next, under the engineering background of coal and gas dynamic phenomena induced by rockburst with different intensities in Xinyi Coal Mine and Pingdingshan Coal Group No. 12 Colliery in Henan Province and Dingji Coal Mine of Huainan Mining Group in Anhui Province, experimental study results were combined with numerical simulation analysis to discuss the energy mechanism of coal and gas outburst induced by rockburst. The study results show that the outburst can be divided into two different processes—critical outburst and outburst—according to the evolution law of outburst energy, and the critical energy conditions for coal and gas outburst are proposed. The minimum destructive energy range for the critical outburst of coal mass is obtained as (5–10) × 104 J/m3. Under some low gas, high stress, or strong disturbance conditions, applied loads can become the main energy sources causing critical failure and even crushing and throwing of coal mass. The coal mass will present an interval splitting structure under dynamic loading, which is obviously different from the failure mode of coal mass under static actions.