Study On Mechanism And Load Characteristics Of Indoor Methane Gas Vented Explosion

The gas explosion in a confined space is a complicated process that is affected by many factors.The load characteristics of the explosion are not only related to the nature of the explosive gas,but also closely related to the constraints of the surrounding environment.Indoor gas explosion usually accompanied by weak surface damage(such as doors,windows destroyed)forms a vent condition.The explosion process of indoor flammable gas under the venting explosion condition is more complicated,because the venting process changes the flow field conditions,which in turn affects the explosion process.Venting explosion is different from the explosion in the hermetic space and the explosion under the open space.The explosion process and load characteristics is difficult to determine.Frequent gas explosions accidents have shown that the indoor gas explosions under such complex real conditions,such as venting and built-in obstacles,are very harmful.The current research is not enough.Only experimental study can not explain the combustible gas explosion and venting process under complex conditions well,especially the interaction mechanism between flow field and chemical reaction in the process.In addition,experimental studies on the complex load formed during the explosion have not been a good theoretical explanation.In this paper,we take this problem as the research object,and use the numerical simulation method to study the explosive process and load characteristics of indoor flammable gas with weak surface,and understand the physical characteristics of explosive process and the load characteristics under different conditions.The main work is as follows.(1)A physical model of gas explosion with venting explosion was established.The physical process of methane gas explosion in the presence of weak surface was studied,and the research has deepened the understanding of the mechanism of gas explosion under the condition of venting.The interaction between chemical explosion of methane gas and the movement of fluid in the process of explosion under the condition of venting explosion shows that the process of gas explosion leads to the increase of turbulence intensity in the flow field.So the change in turbulence intensity counteracts the chemical reaction process.In this way,the flow field interacts with the chemical reaction process,making the explosion process changeable,forming the characteristics of multi-peak and long-term explosive load,and the load characteristics depend on the specific explosion and venting conditions.(2)The numerical model is used to study the complex explosion load types obtained by experiments.The characteristics of overpressure load caused by several kinds of indoor explosions under different pressure and different methane concentrations are explained.The results explained the influence of different gas initial conditions and venting conditions on the explosion process and load characteristics.At the low vent pressure and near the stoichiometric concentration,indoor methane gas explosion will produce more than two explosion overpressure peaks.With the venting pressure increases,the number of overpressure peaks will be reduced to 2.When venting pressure is high and methane concentration is rich/lean,the explosion will produce only a single overpressure peak.(3)The numerical simulation was used to simulate the explosion process and explosion load characteristics of indoor methane-air premixed gas under different conditions.The influence of indoor obstacle on gas explosion was analyzed.When there are obstacles in the room,the explosion load of combustible gas is obviously increased,and indoor overpressure increased by 30%.With the increase of the blockage ratio,the overpressure,temperature and gas flow velocity indoor explosion increase first and then decrease,and there is a maximum value.Outdoor temperature and gas flow rate decreases with increasing blockage ratio.The influence of ignition position on explosion load was analyzed.The results show that the blast overpressure and the temperature generated by the rear wall ignition is higher than the center ignition.Gas flow rate indoors is not much difference.The explosion load of the outdoor rear wall is higher than the center ignition.Explosion temperature increases with increasing blockage ratio.Indoor gas flow rate is not much difference,and the outdoor flow field will gradually decrease with the increase of the weak surface ratio.The explosion process and venting process of indoor methane under different vent area were studied.The results show that with the increase of weak surface ratio,explosion overpressure gradually decreased.Explosion temperature will increase with the blockage ratio increases.(4)Based on the numerical analysis results,the explosion disaster effects were analyzed.The overpressure-impulse criterion was used to evaluate the level of damage caused by indoor methane gas explosion to brick-framed buildings.The results show that obstacles will increase the damage effect,and with the increase of vent area,the impact of explosion on the brick wall structure gradually reduced.In this paper,the modeling and analysis of indoor gas explosion under different venting conditions are carried out.The complex load mechanism formed by explosion is discussed,and the understanding of the explosion process and mechanism is deepened.The research in this paper has important theoretical guidance and application value for the research on gas explosion accident and disaster prevention.