Coupling Effect Of Side Vent And Mesh Firestop Structure On Gas Explosion Characteristics In A Duct

Gas explosion accidents are one of the common types of accidents in the mining industry and manufacturing industry.The characteristics of gas explosion accidents are sudden,instantaneous and destructive.Once a gas explosion occurs,it will often cause devastating consequences and adverse effects,threatening the personal and property safety of employees.When the flammable gas is in a relatively closed space,due to its flammable and explosive characteristics,excessive air or abnormal fluctuations of methane concentration may result in unexpected gas explosion accidents and severe losses.In order to reduce the losses caused by accidental explosion accidents,this paper combines two widely used emergency disaster mitigation measures to study the coupling effects of setting side vents and mesh firestop structures on gas explosion characteristics in the duct.In this paper,a closed simulation duct with a length of 3000 mm and an internal dimension of 120 mm × 120 mm is constructed.The experiment was carried out with premixed methane gas with a concentration of 10% as a typical flammable gas.A singlelayer wire mesh was selected as the wire firestop structure.Side vents were set at different positions on the side of the duct,and single-layer wire meshes with different specifications were set at different positions inside the duct to analyze the premixed flame propagation and overpressure characteristics of methane explosion under various experimental conditions.Based on this,the coupling effects of the combination of two emergency disaster mitigation measures on the explosion characteristics of flammable gas are obtained,and the following main conclusions are drawn:(1)The single effect of side explosion vents at different positions in the duct on explosive characteristics of a methane explosion was studied.The closer the side vents are to the ignition source,the more pronounced the suppression effect on premixed flame propagation.At the same time,when the side vent connected to the outside area is located downstream of the explosion flame,its inductive effect stimulates the propagation of the premixed flame;for the premixed flame after passing through the side vent,since the flame development direction is opposite to the induced direction,the flame spreads in a short period.Instead,it was inhabited by the induction effect.In addition,the release effect of the side venting port has a significant effect on suppressing the explosion overpressure in the duct.It is worth noting that in the late stage of explosion development,the premixed flame will develop again when it propagates downstream of the side vent,and a backfire may occur in the area of the side vent.(2)In the duct configuration of the side explosion vent,when 30 mesh wire meshes are installed in different positions.The wave-absorbing and endothermic properties of the wire mesh are more effective for the experimental configuration with lower flame velocities.The side vent near the ignition source effectively suppresses the undeveloped premixed flame,and the quenching performance of the porous medium is fully exerted.The side vent and the wire mesh complement each other to suppress the premixed flame.However,the opposite is true for side vents downstream of the duct.The premixed flame propagation is continuously stimulated by the inductive effect of the downstream side vent,and the resulting high-speed turbulent flame is difficult to be effectively suppressed by the downstream wire mesh and the side vent,which leads to the failure of the premixed flame suppression in such conditions.(3)Wire meshes of different meshes are set in the duct configuration of the side venting outlet.The low-mesh wire mesh is not effective in suppressing the premixed flame propagation,and the flame propagation characteristics are close to the data of the no-load duct.When the high-mesh wire mesh is set,as the mesh number of the singlelayer wire mesh in the duct increases,the suppression effect on the premixed flame is more significant.However,at the end of the duct,the premixed flame propagates in the form of turbulent combustion,the velocity development law is relatively disordered.(4)The coupling effect of the side vent and the wire mesh on the overpressure in the duct is mainly affected by the characteristics of the side vent.However,the wire mesh of different meshes still further suppresses the overpressure in the duct,especially after the premixed flame passes through the explosion suppression area where the mesh flame arrester is located.However,in the late stage of explosion development,the peak overpressure of the premixed flame propagating in the form of turbulent combustion increases significantly in the high mesh condition.However,it is still lower than the peak overpressure of the no-load duct.