Experimental And Numerical Studies On Methane Explosion And The Suppression Effect Of CO₂in Vessel

Burning and explosion caused by gas under uncontrolled conditions can bring enormouslife and property losses. Based on the huge destructive effect of flammable gas explosion, it isincreasingly urgent to study its destructive patterns, mechanism of explosion andcorresponding suppression method, so as to put forward the measures of disaster preventionand mitigation.In this paper, combining with the relevant mechanism of combustible gas explosion andspread, XKWB-S gas explosion flame propagation characteristics test system and professionalgas explosion simulation software FLACS were employed to study the explosioncharacteristics of methane in different concentration of small size explosive pipe and processof CO2to suppress the explosion.The result shows that the explosion limitation of methane in the quartz glass pipe is4.95%~12.65%, which its inner diameter of88mm and1600mm long (L/D=18). Inductionperiod of methane shortens with the increase of concentration. After methane being ignited,the production process of flame can be divided into the two parts,which is the spherical flameand inner flame stretching and moving forward. The thickness and the speed of flameincreases with the increase of the spread distance of explosion, and the closer theconcentration of methane gets to its equivalence, the greater the thickness of the flame in theexplosive propagation process. During the explosive propagation process of methane, theexplosive overpressure goes through the pressures of build-up, spread of pressure, pressurebackflow, shocking and recovery of normal pressure stage; Temperature rises rapidly after theexplosion, then fell down as the explosion flame propagation is affected by the wall. Aftervented explosion, gas in the open position move to the closed end under the action of negativepressure backflow, which leads to the temperature in the closed end rises. 9%volume fraction of CH4will still explode in the6~18%volume fraction CO2.Withthe increase of CO2, the explosion pressure decreases, the intensity of the flame and brightnessare reduced gradually, and the velocity is decreasing gradually. Due to the effect of turbulencein explosive propagation process, the speed of flame propagation fluctuates. Because of theinfluence of pressure wave, reflection wave, the wall action and the turbulence, the pressureand the speed is a certain degree of fluctuating. Influenced by the change of gradient andturbulence during the explosion propagation and vented explosion in the pipe, explosionpressure and gas movement speed of every groups of mixed gas did not reach maximum at thesame time. When the content of CO2increases to18%, explosion pressure peak value of9%CH4decreases about77%, time of reaching the pressure peak is about3.35times,concentration of explosion product increases with the increase of CO2.21%~27%of the CO2inhibits the explosion of CH4completely.