Study On The Characteristics Of Methane-air&Coal Dust-air Mixing Process And Explosion In Large Scale Conditions

The methane explosion or methane-coal dust explosion in coal mine is the main formof accident, which received extensive attention of society. The mixing process andexplosive characteristics of methane-air mixture and coal dust-air mixture are basicproblems of explosion accident, thus carrying out this research has important theoreticalsignificance and practical significance.Based on the gas mixing idea of space structure matching, a experiment system ofmultiple gas mixing process and concentration monitoring was build with the help oflarge-scale confined container (10m3explosion vessel). Via the systematic experiment,study the influence of air-intake device structure size, inlet velocity and differentdifferential pressure on the effect of methane-air mixing. The results show that when thehole diameter of air intake system is1.5mm, hole spacing is100mm, inlet velocity controlin8m3/h and0.04MPa for initial vacuum degree, gas mixing effect achieve the best state.Under the condition of methane-air quick mixing, we tested the methane explosionlimit in air in large-scale confined container (10m3explosion vessel), through thedevelopment of pressure and optical test criteria, according to a certain degree of "absolutesafety", we determined the explosion limit range in10m3explosion vessel of5.5%~15.5%.Focusing on explosion state of pressure field of different methane concentrations nearlower explosive limit, after the analysis, it was found that when the concentration of naturalgas was close to lower limit, three types of pressure curves existed. Former shock wavegenerated in the beginning of explosion was found as well with the further combustionwave.This paper is based on the relative theory and basic research achievements of soliddispersion driven by explosion wave, built the method of the uniform and stable coal dustcloud formation suitable for large-scale space; We dynamic analyze the process ofexplosion wave driven coal dust by systematic experiment and found that the coal dustcloud boundary layer velocity present three stages: acceleration, deceleration and turbulentstage; Through the analysis of the influence of different drive energy on coal dust cloud’s boundary layer velocity and cloud volume, we found the cloud boundary layer velocityincrease with the increase of center charge quality, but when the percentage of centercharge quality is1.3%, coal dust quality range from320g to1110g all get the maximumcloud volume.We take advantage of AutoReaGas to study the influence of some factors in idealisticroadway (such as methane concentration, methane accumulation zone length, obstaclesblocking ratio, initial pressure and initial temperature) on the explosion characteristicparameters of methane-air mixture; We contrast the explosion characteristic parameters ofmethane-air mixture with that of methane-coal dust-air mixture. We found that combustionand explosion process had more destructive with coal dust; We obtain that the more mixtureexplosion intensity, the closer the maximum overpressure appear to the location of ignitionsource.The above achievement of research on the characteristics of methane and coal dustmixing process and explosion in large scale conditions, laid the foundation for the coalmine explosion prevention and control.