Based on the suppression mechanism of multilayer wire meshes to the propagation of gas explosion,the mathematical model on multilayer wire mesh structure restraining conflagration and detonation is set up,which shows the relationship among flame propagation parameters,explosion reaction wave parameters and wire mesh structure parameters.
A multicomponent wetting model of coal-water-methane-hot flue gas was hereby constructed to investigate the influence of complex components of hot flue gas on coal wettability. Besides, whether it is feasible to use the NIST method to capture the system pressure was verified from a microscopic perspective. Moreover, how the interaction energy and hydrogen bonds between water and coal, the spreading length of water nanodroplets in the
Abstract Understanding a safety distance necessary to avoid the harms of a shock wave to underground personnel may have great significance to the safety of underground personnel, disaster relief efforts, and the treatment of the gas explosion in coal mines. Through a roadway model with a cross-section area of 80 × 80 mm2 and a length of 100 m, the explosive attenuation characteristics of a methane/air mixture with a fuel concentration of 9.5% and a filling ratio of 10% were simulated by using AutoReaGas software for various initial temperatures (248–328 K) and initial pressures (20–200 KPa). The results show that the safety distance increases with the increase of the initial temperature and follows the changing trend of decreasing, increasing, and decreasing again with the increase of the initial pressure. The time of flame arrival to each point away from initiation and the maximum distance of flame propagation both increase with the increase of the initial temperature, but they are almost the same for various initial pressures. Before the attenuation of the shock wave occurs, increasing the initial temperature increases the maximum temperature, but decreases the peak overpressure, the maximum density, the maximum combustion rate, and the maximum gas velocity. However, increasing the initial pressure increases the peak overpressure, the maximum density, and the maximum combustion rate. The influences of the initial temperature and the initial pressure on these parameters at the longer distance points from the ignition source are greater than those at the shorter distance points. Keywords: Gas explosionInitial pressureInitial temperatureSafety distanceShock wave ACKNOWLEDGMENTS This work was partly supported by the Major State Basic Research Development Program of China (973 Program) (No. 2011CB201205) and the Open Fund Program of the State Key Laboratory of Explosion Science and Technology (No. KFJJ10-19 M).
Permeability enhancement by injecting acidified flue gas to dissolve minerals within coal fractures offers a novel approach to solve the problem of gas drainage from deep, strongly adsorbent, and low-permeability coal seams. However, the dynamic response mechanisms of the internal expansion coefficient, fracture bulk modulus, and permeability during mineral dissolution in coal fractures remain unclear. To address this problem, we constructed a permeability model that considers the dynamic changes of the internal expansion coefficient and fracture bulk modulus during mineral dissolution based on the "matrix-rock bridge-fracture" physical model of coal. Then, the permeability changes of mineral-containing coal under a constant gas pressure, a constant effective stress, and a constant confining pressure at different reaction times were tested and analyzed using the self-built CO2–H2O–Coal interaction and permeability test system. Based on the fitting results between the constructed permeability model and the experimental data, we delved into the dynamic evolution patterns of the internal expansion coefficient and the fracture bulk modulus during mineral dissolution in coal fractures. Ultimately, the separate and coupling influences of key parameters of the model (soluble mineral content variation, initial fracture porosity, Langmuir strain constant, Langmuir pressure constant, and average molar volume of soluble minerals) on the coal permeability were clarified by utilizing local and global sensitivity analysis of the verified permeability model. This study can provide a theoretical reference for engineering permeability enhancement by mineral dissolution using flue gas.
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