Multiparameter Temporal And Spatial Evolution Of Gas Explosion And Its Suppression Using Gas-solid Jet Curtain

Gas explosion is one of the most serious disasters in the coal mining accidents,and it can cause a large number of losses of human lives and property. More and moreinputs to gas drainage have been made in order to prevent gas aggregation at source.But in China, the amount of low concentration coal mine gas drainage accounts for alarge proportion, the serious safety hazards still exist in the process of gastransmission by long distance pipelines. Considering the parameters of a gasexplosion are multiple, the gas explosion propagation may present some particularitiesand complexities. So it is necessary to study on the multiparameter temporal andspatial evolution of gas explosions in roadways (or gas transmission pipelines), thento develop a new explosion suppression equipment which may control the gasexplosion disasters in a small area.In this paper, the methods of theoretical analysis, numerical simulation, andexperimental research were used to study on the coupling relationships of the gasexplosion overpressure and the flame instantaneous speed respectively with thepropagation distance, the multiparameter acceleration and attenuation characteristicsof gas explosions, and the explosion-proof safety distance and flameproof distance ofgas explosions. Based on these above, the active explosion suppression and inertingdevices using high-pressure gas-solid jet curtain were developed, and their responsetime and explosion-suppression effectiveness were also tested. The main innovativeresults are shown as follows.Based on some assumptions, the formulae for the coupling relationships of theoverpressure, the gas velocity, and the shock-wave propagation speed respectivelywith the propagation distance after the strong shock wave of a gas explosionattenuated were established. It was found that the overpressure was inverselyproportional to the propagation distance and the roadway cross-sectional area, anddirectly proportional to the total energy of the gas explosion. However, the gasvelocity and the shock-wave propagation speed were both inversely proportional tothe square root of the propagation distance and roadway cross-sectional area, and bothdirectly proportional to the square root of the total energy of the gas explosion. Undersome experimental conditions, the formula for the theoretical coupling relationshipbetween the flame instantaneous speed of a gas explosion occurred in a straight steelpipe filled with fuel and the propagation distance was built. It was found that the flame instantaneous speed increased with increasing distance from the ignition source,but the increasing amplitude gradually decreased.The explosion-proof safety distances and the flameproof distances of gasexplosions for various initial temperatures, initial pressures, initial spherical flameradii, and fuel volumes were calculated, and the influences of these factors on themultiparameter attenuation characteristics and explosion-proof distances of gasexplosions were also revealed. It was found that increasing initial temperaturedecreased the maximum overpressure, the maximum density, the maximum gasvelocity, and the maximum combustion rate linearly, increased the maximumtemperature and the flameproof distance linearly, and increased the explosion-proofsafety distance gradually. Increasing initial pressure increased the maximumoverpressure, the maximum density, and the maximum combustion rate linearly, butits effect on the explosion-proof safety distance had no obvious regularity and theeffect on the flameproof distance could be ignored. The effect of changing the initialspherical flame radius on the maximum overpressure, the maximum density, themaximum temperature, the maximum gas velocity, and the maximum combustion ratewas small, had no obvious regularity on the explosion-proof safety distance and couldbe ignored on the flameproof distance. Increasing fuel volume increased themaximum overpressure, the maximum density, the maximum gas velocity, themaximum temperature, and the explosion-proof safety distance, and increased theflameproof distance linearly.The explosion suppression and inerting devices using high-pressure gas-solid jetcurtain were developed, and the explosion suppressant was the two-phase mixture ofnitrogen and ABC dry powder. The spurt efficiency increased24.73%than thereference value setting by national standard AQ1079-2009, the spurt completion timeshortened by20%, and the total time from accepting flame sensor signal to spurtingthe maximum quality of ABC dry powder decreased by24.86%. If the difference offlame arrival time between the flame sensor in front of spurting powder position andthe trigger flame sensor was in117~919ms, the explosion suppression would besuccessful. By explosion suppression experiments, it was found that spurting nitrogenand ABC dry powder had an obvious suppression effect on the explosion overpressureand the flame speed, and the maximum decreasing amplitudes of overpressure andflame speed were76.7%and100%respectively. The flame extinction position waswith the scope of3m around the position of spurting explosion suppressant, less than 6m referred to the national standard. After the high-pressure nitrogen and ABC drypowder had suppressed the gas explosion propagation successfully, the surplusexplosion suppressants would still prevent at least five gas explosions. The successfuldevelopment of the explosion suppression technology using gas-solid two-phase jetcurtain might provide a new technical way for the isolation and suppression of gasexplosions in underground roadways of coal mines or the gas transmission pipelines.Research results might have very important scientific value and practical significanceon preventing the expansion of gas explosion disasters.