Research Of Explosion Process On Premix Gas Of Methane-Air In Horizontal Pipeline

With the deep exploitation of coal mines, methane emission rises sharply and the threat caused by gas explosion disaster becomes more and more severe. Most of the serious accidents in coal mines are due to gas explosion. To avoid gas explosion, the influencing factors and pattern of gas explosion characteristic parameter (such as explosion limit, explosion pressure,flame velocity) must be firstly obtained.The common devices for gas burst as 20L cylinder tank and 1m3 spherical pot are unsuitable for gas explosion. Gas explosion needs to be carried out in analog tunnel or experimental channel. The characteristic parameters of gas explosion are obtained by experiment or analogue. Therefore, a set of new horizontal pipeline experiment system for gas explosion is built, in which the length, inner diameter and slenderness ratio of the longest pipe are 9.7m,0.14m and 70 respectively. It consists of horizontal pipeline explosion duct, blast pressure test macro and other facilities. Furthermore, a set of control system and flame velocity test system are designed and made. To meet the experiment requirements, installation and debugging for the system are completed.Methane is the main component of gas. So gas explosion can be considered as the explosion process of the mixture of methane-air initiated by external ignition source. Explosion characters for premix gas of methane-air were studied in the experiment system. Explosion limit for methane was measured in a short duct of 0.7m. The results indicate that under condition of this article the explosion limit for methane is 5.5%-14.5%, that five concentrations of methane were selected in the range of explosion limit and that the explosion pressure was measured under these concentrations. The results indicate that the optimal concentration is 10% and under this concentration the explosion pressure and the rate of explosion pressure rise become maximal, the time for the maximum explosion pressure is minimal. The flame velocity of methane was tested with the flame velocity test system. The flame velocity for methane in the pine with obstacles is greater than that in the pipe without obstacles. In closed pipe, the flame velocity reduces with the increment of propagation distance.The influence laws of pipe length, obstacles, distribution way and fitting depth of sensors to blast pressure were researched comprehensively. Explosion experiments in duct with three different lengths were done. The results indicate that the maximum explosion pressure and maximum rate of explosion pressure rise present in 3.1m duct and increase with the propagation distance. The effect of ring obstacle with 60% block ratio on the explosion pressure was studied by experiments. The results indicate the maximum explosion pressure and maximum rate of explosion pressure rise present when the quantity of obstacles is three. The two reduce initially and then increase with the increase of the propagation distance. According to the low evenness degree of two-way distribution, a set of distribution device and multi-ported and multimodal distribution methods were established. The new distribution methods remarkably advance the evenness degree and explosion pressure and rate of explosion pressure rise of 10% methane increase with the evenness degree. Varying installation depth can change the position of sensor sensitive area. The experiment research indicates that explosion pressure and rate of explosion pressure rise reduce with the increased distance of sensor sensitive area to pipe center, and the maximum explosion pressure of pipe center is 1.8 times to the pressure of wall.The explosion processes of premix gas of methane-air in the smooth ducts and those with obstacles were numerically simulated by the software of Fluent respectively. It shows that the numerical simulation coincides with the experimental results.