Experimental Study On Characteristic Parameters Of Material Evidences In Gas(Coal Dust) Explosion

China is one of the largest coal production countries in the world, and also is the most seriously affected by various disasters, where the gas (coal dust) explosion often occurring has greatly affected the safe and high effective production and international reputation of coal mines in China. Considering the problems of the basic research of gas (coal dust) explosion is weak and the basic norm of material evidence analysis in accident investigation is few, the characteristic rule of explosion characteristic parameters, including explosion pressure, flame temperature and flame speed, was theoretically analyzed based on the data from the experiments of gas (coal dust) explosion done in the spherical vessel and the horizontal pipe of the gas (coal dust) explosion experimental system established in this paper. The structure of the flame in the gas explosion and gas and coal dust mixture explosion was analyzed by using high speed photography technique.The temperature and pressure of gas explosion were calculated by using thermodynamic theory and method, then the results were comparing analyzed with experimental results. The criterion determined the nature of explosion accident and explosion source were proposed initially based on the characteristic parameters and the characteristics of gas and solid residues. The results are as follows.(1) Experimentally studied on the change laws of the characteristic parameters such as pressure, flame temperature and propagation speed of gas explosion and gas and coal dust explosion in the sealed containers (20L explosion sphere, horizontal pipe).The characteristic parameters in temporal dimension all showed the trend of increasing first and decreasing after the peak value.(2) The affection of gas concentration, dust concentration, coal quality on the characteristic parameters was investigated systematically and the correlation effect of the characteristic parameters was analyzed. The results showed that within the explosion limit of methane, the explosion intensity was the largest and the pressure, flame speed and temperature were all at their maximum when the gas concentration reached 9.5%, and they have positive correlation. Under the condition of the same gas concentration, the explosion pressure reached to the maximum when the coal dust concentration was 400g/m3.(3) The structure of the flame in the gas explosion and gas and coal dust mixture explosion was analyzed by using high speed photography technique. The phenomenon of flame burst would be emerged in the gas explosion. The flame can be divided into dark area (unburned area), micro-bright area, red and yellow emission region and white emission region along the horizontal pipe in the process of the gas and coal dust mixture explosion. (4) Gas and solid components and their change law of the gas explosion and the gas and coal dust mixture explosion were studied. The main components were carbon monoxide, carbon dioxide, hydrogen, oxygen, nitrogen and methane after gas explosion. The greater the gas concentration was, the larger yield of carbon monoxide was, but the amount of carbon dioxide increased first and then decreased. Along with the increasing of the amount of coal dust which participated in explosion, the formation amount of methane, hydrogen, carbon monoxide increased gradually after gas and coal dust explosion. Meanwhile, the change law of carbon dioxide in gas and coal dust mixture explosion was similar to the situation in gas explosion. The industry composition of soft coal, anthracite and lignite which participated in the gas and coal dust explosion were analyzed comparatively. The volatile and fixed carbon of all kinds of coal decreased significantly but ash increased significantly after the explosion.(5) Variation characteristics of hydrogen generation are researched. The generation of hydrogen is rare when the gas concentration range is from 5% to 12% and hydrogen generation is increasing significantly when the gas concentration is more than 12%.Meanwhile, the generation of hydrogen is increasing greatly with coal dust concentration increasing. The exist of hydrogen decreased the lower explosive limits of gas (coal dust) which maybe the main reason lead to continuous explosion in coal mine. The main reason why the generation of hydrogen without danger of explosion within its explosive limit is the concentration of oxygen is lower in blast cavity.(6) The gas explosion process in the confined space is analyzed and the theoretical formula of the gas explosion pressure and temperature is established based on the energy conservation principle and used thermodynamic theory and method. Considering the premise of heat loss, the gas explosion pressure and temperature are calculated under the different gas concentrations. The calculated results are basically in accordance with the experimental results.(7) Based on the characteristic parameters of gas explosion and gas and coal dust explosion and the characteristics and change law of solid composition, the thesis tentatively proposed the synthetic criterion for determining the nature of explosion and location of explosion source in explosion accident investigation.The researches of the thesis are able to provide theoretical basis for further study of gas (dust) explosion evolution and material evidence analytic technique of gas (dust) explosion and have far-reaching theoretical significance and important potential of application for further revealing the microscopic mechanism of gas (dust) explosion and monitoring and forecasting of rock or coal dynamical disasters.