Numerical Simulation Of Deflagration Of Flammable Gases In Built-in Obstacles Confined Space

Combustible gas explosion is one of the main topics in the field of security. Itoften occurs in many industries of industrial sector.and having a great harm, withindustrial development and expansion of production scale, the degree of explosionhazard increases, Practice has proved, the existence of an industrial environmentconstraints object (the supports of house, the stent of duct, the devices of plant, etc.)has a great influence on the acceleration of flame and induced explosion. obstaclesencountered during propagation can cause secondary explosions, making damagestrengthened. Currently, most of the premixed gas explosion tests are conducted inthe pipeline, Given the experimental contrast, This paper simulates the explosionprocess propagation of premixed gas in pipeline.Based on the experimental of Patel in the literature, this paper has carried onnumerical simulation for premixed gas deflagration process of methane-air, Using alarge eddy turbulence and premixed combustion model. This paper solves thedeflagration pressure and deflagration velocity in the tube. The simulation resultswere compared with Patel’s experiment by contrasting the change of flameconfiguration, deflagration pressure and flame velocity. the results show thatsimulation results match well with the experimental results, to verify the reliabilityof the mathematical model, showing that numerical simulation can effectively thedeflagration process and pressure variation law: Pressure time history indicates thatthe deflagration pressure through the following four stages：pressure slowly risingphase, pressure rapidly rising phase, pressure falling fast phase and pressurefluctuation phase. Flame speed is increased overall, first increases and thendecreases trend around an obstacle. Maximum value occurred in about1.2ofequivalent ratio. Because of disturbance to the flame surface by the obstacles, flamesurface deformation increases with the increase of number of obstacles and blockingrate of barriers. The large the surface area of flame, the greater the flame speed anddeflagration pressure rising. Wall for adiabatic condition, the quantity of heat ofdeflagration with stones can be extended to accumulate, the flame temperature,explosion pressure.On this basis, This paper further discusses the impact on flame propagationprocess by changing the equivalent ratio of premixed gas, number of obstacles,blocking rate of obstacles, location of obstacles and length of the tube. themaximum explosion pressure and the maximum flame speed increases with theincrease of equivalent ratio, first after decreasing trend, Because of the influence of the laminar burning velocity and chemical reaction, the maximum occurred in theabout1.2of equivalent ratio. Because of the disturbance of obstacles to the flamesurface. flame surface deformation increases with the increase of number ofobstacles and blocking rate of barriers. The larger the flame surface area, the greaterthe flame speed and deflagration pressure, Wall for adiabatic condition, the quantityof heat of deflagration process with pipe length can be extended to accumulate, theflame temperature increase, explosion pressure increase. The farther Obstacledistance ignition position, the higher the temperature when the flame surface arrivedat obstacles, the greater the speed and pressure.In addition, this paper simulates flame surface deformation, pressure and speedvariation in the process of explosion of methane-air premixed gas in closed system.in the beginning of a period of time, Flame surface changes consistent with opensystem, after a silence, flame burning curled downwards by wall constraint.Pressure began to change slowly, Later, rising fast, after finally reached7.5MParemain unchanged, Due to the role of obstacles, the flame speed appeared threepeaks.