Research On The Flame Microstructure And Characteristics Of Gas Explosion In Limited Space

The accidents of gas explosion occurred most frequently in the production process of coal mine, so how to prevent and control gas explosion for the safety of coal mine is the main problem. Therefore, it's necessary to study the gas explosion process and related parameters of the flame structure. In this paper, the structure characteristics of flame propagation were studied by experiments, numerical simulation and analysis methods.The experimental system was built up to detect the microstructure of flame and the flame propagation of 9.5 percent methane-air mixtures in pipes, which was consisted of 50cm x 8cm x 8cm square pipe, the high-speed video, the ion current and the thermocouple el. With the help of high-speed video, the characteristics of gas explosion process and the structure change of "tulip" flame formation was successfully and clearly captured. The picture of flame structure combined with the physical parameters was used to analysis on the changes of temperature, the rising rate of pressure and other related parameters' variations in the pipeline, which revealed the characteristics of premixed fine structure and the flame propagation. The research also showed that in the process of flame propagation in pipes, the flame structure sometimes experienced "smooth-center concave-instability" process, which showed the unstable of flame. During the process of flame propagation, the speed of flame traveled faster at first and then slowed down, which due to the pressure wave reflection, and "tulip" flame was formed not only in the rapid decrease speed of the region, but also the acceleration of the deceleration phase was near to maximum. The flame structure changes accomplished with turbulent flow, and the thickness of the flame also changed.The mathematical model and similar physical model of pipe was established to study the numerical simulation of the flame propagation with premixed methane-air. Then the related parameters such as temperature, pressure, rate of speed, etc. was obtained during the burning process. Experiment and numerical simulation results revealed the rational of the experiment. Finally the numerical simulation method was used to analyze the related parameters near the flow field of flame when the concentration, pipe length-diameter ratio, pipe pressure ratio and the obstacles changed especially. The results of this topic research could not only be further used to prevent and control gas explosion accidents, but also significant for the study of how to prevent flammable pipeline effectively and safety in gas explosion accidents.