Experimental Study Of Suppressing The Methane/Air Explosion By Heptafluoropropane

In the field of industrial production,gas explosion accidents always happen,especially in coal mining industry,methane-air explosion accidents happen frequently,which pose a great threat to people's life and property safety.For this reason,the work of prevention and control of gas explosion has been the research focus of relevant scholars.The footsteps of exploration and development of efficient explosion inhibitor have never stopped.The gas explosion suppressant can be mixed with combustibles and oxidant molecules at molecular level,thus playing a better suppressing effect.Heptafluoropropane,as one of halon replacement agents,because of its excellent chemical inhibition effect,which has attracted much attention from scholars.But the previous study for heptafluoropropane is more concentrated in the field of fire suppression but not explosion suppression,the summarize for the enhancement and inhibition effect of heptafluoropropane has not enough to be systematic,the mechanism of inhibiting flame of heptafluoropropane has not yet formed a unified conclusion.Threrfore,in this paper,heptafluoropropane suppress methane-air explosion is regarded as the research object,experimental research and numerical simulation are combined to study the effect rule and suppression mechanism of heptafluoropropane to gas explosion.The main contents are as follows:(1)Visual closed experimental apparatus was set up to study the suppression effect of heptafluoropropane to methane-air explosion,including closed explosion chamber,gas distribution system,ignition system and data acquisition-control system,which could realized the high speed taking of dynamic picture of explosion flame propagation process and high frequency acquisition of the change process of explosion pressure.(2)The experimental research of heptafluoropropane affect different equivalent ratio methane-air explosion was carried out.The effects of the addition of different concentrations of heptafluoropropane on the flame propagation process and the explosion pressure were investigated under the conditions of methane-air as lean-burn,stoichiometric ratio and rich-burn condition.In the lean and stoichiometric ratio condition,as the concentration of heptafluoropropane increases,explosion intension first increases and the n decreases,in condition of equivalent ratio is 0.6,the explosion overpressure is always greater than that without inhibitor,while equivalent ratio is 0.8 and 1,just when the concentration of heptafluoropropane reach 8% and 6%,the explosion overpressure is lower than that without inhibitor;In the rich condition,heptafluoropropane adding could lead to suppression result;In the condition of equivalent ratio is 0.6/0.8/1/1.2/1.4,the critical inhibitory concentration of heptafluoropropane is 10.5%/9.5%/6.5%/4%/3% respectively.(3)The suppression mechanism of heptafluoropropane to methane-air explosion was discussed,sensitivity analysis and reaction rate analysis were used to explore the chemical reaction mechanism of heptafluoropropane on methane air explosion.it was carried out that the adsorption of oxygen molecule with fluorine radicals and the endothermic decomposition process of heptafluoropropane molecule play a key role in suppression effect,but the process of oxidation of fluorine radical promote the combustion;At the same time,the decomposition path of heptafluoropropane in methane-air explosion was got,and the process heptafluoropropane influence the methane burning chain reaction was discussed.(4)The experimental research of mixed heptafluoropropane-inert gas(nitrogen and carbon dioxide)affect different equivalent ratio methane-air explosion was carried out.Under the condition of each equivalent ratio,heptafluoropropane-inert gas would show the synergistic suppression effect,that is the mixed inhibitor suppression effect is better than that of the two ones when they act alone,especially carbon dioxide played a better role in inhibiting than nitrogen,because of its excellent dilution and endothermic effect,inert gas could weaken the enhancement effect of heptafluoropropane in lean condition.