Simulation Of Explosion Flow Field Inside The Pipeline Of Gas Extraction

Gas extraction is a fundamental measure of coal mine gas control,the gas that was produced during the coal mining is pumped timely cangreatly reduce the incidence of gas explosion and asphyxiationaccidents; Mostly the way that was used in the gas extraction was coalrelief, which resulting in a lower concentration of gas in the extractingpipeline, approximately in the range of8%to12%, just in the explosionlimits. In this paper, we choose a section of the level elbow used in adomestic coal extraction as the research object, examine the distributionand dissemination characteristics of the temperature, pressure, speed,and reaction rate etc inside the tube when the elbow blew up, and makea comparative analysis of the impact on explosion flow field by the sizeof the diameter and structure of the pipeline.For the bending tube explosion process, continuous curve ofpipeline gas lead to turbulent kinetic energy and kinetic energydissipation rate increases, thus the reaction rate is accelerated, thebending tube gas combustion completion time compared with the samediameter and length of straight pipe within a short reaction time by7.4%. Temperature, pressure, speed, reaction rate of explosion gas in thebending tube are developing at a certain acceleration, the temperaturearriving at nozzle as high as2947k, the relative pressure of the gas getsto24.4MPa, gas flow rate is801m/s, the reaction rate is3.97kmol/m3·s.The combustion flame surface acts as "<" shape from beginning to the end in the straight tube. At80ms, the velocity wave, temperaturewave, reaction rate wave and pressure wave are very apparent in thepipe. The speed wave is the most advanced, which followed by thepressure wave and reaction rate wave, finally the temperature wave.Pipe diameter size has certain influence on the combustion flow field inthe straight tube, with the increase of pipe diameter. The temperature ofthe combustion gas decreases gradually, the highest instantaneousvelocity and the maximum relative pressure of the gas inside thestraight tube showed a trend of decrease after the first increase.The reaction rate in two types of piping both are rising slowly atfirst, and then accelerated. In the slow rising phase, the reaction rate haslittle difference; but in accelerated phase, the acceleration of thereaction rate in the elbow is larger. From the whole process ofgas-burning in the pipeline, the maximum temperature and themaximum reaction rate were almost the same in the two forms; and themaximum relative pressure and maximum flow rate of the gas instraight pipe were significantly higher than in the elbow to34.1%and13.4%.This study has important theoretical and practical value in thedesign and layout of gas drainage pipeline and is also valuable to thepost-processing and explosion protection measures when explosiontook place.