| As one of the worst coal mine disasters, gas explosion has been restricting coal production for a long time. In order to control the occurrence of gas explosion and reduce the loss caused by it, investigation on propagation law of gas explosion and flame turbulence characteristics in gas explosion have become one hot topic in recent years. In this paper, the flame turbulence characteristics of gas explosion are studied through experiments and numerical and simulation. It aims to provide theoretical guidance for mastering gas explosion propagation law and reducing the loss taken by gas explosion.According to the actual situation in mine, an experimental facility with the size of 150 mm×150 mm×500 mm is designed and set up. The influences of staggered obstacles and hollow-squares on flame turbulence characteristics are studied through flame structure, flame propagating velocity and gas explosion overpressure. The results show that the staggered obstacles and hollow-squares all have an important influence on flame turbulence characteristics. It is more easily to induce flame distortion and surface wrinkles by staggered obstacles. This will be beneficial for higher flame turbulent intensity, flame propagation velocity and explosion overpressure. What’s more, the more obvious pressure fluctuations will be caused by staggered obstacles, and the destructive effects on mine roadway are significant. So the obstructions in coal mine should avoid staggered. The bigger area and shear strain of flame will be induced by triangle hollow-square compared with square and circular hollow-squares. This will be beneficial for higher flame turbulent intensity, flame propagation velocity and explosion overpressure. In addition, if the area(blocking rate) of the hole is fixed, the flame turbulence intensity, flame propagation velocity and explosion overpressure will reduce with the increase of the edge number of the hole.Furthermore, this paper has developed a geometric model with an extended zone, subgrid scale turbulence model, and user-defined turbulent combustion model. Based on the experiments, three-dimensional numerical calculations are performed using Large Eddy Simulation(LES) of to simulate some experimental conditions by comparing the experimental and simulation results, Charlette combustion model is proved to be available and applicative. According to the simulation results, the variation characteristics of some parameters such as flame structure, flame propagation velocity and explosion overpressure are analyzed to further verify the generation of turbulence induced by obstacle and explicitly reveal the obstacle-induced turbulence generation process. Combined with the variation of flow field traces and the distribution of vorticity in flame surface during flame propagation, the coupling process between flame and turbulence is revealed. After the explosion, the unburned gas in the front of flame is pushed to the exit of the chamber under the effect of thermal expansion which is generated by the burning. And disturbances occur in the role of the obstacles. As the reaction continues, the heat increases and strengthens the distension. At the same time the flow rate of the unburned gas improves and the eddy generates quickly in the downstream of the obstacles. The intensity and size of the vortex increases gradually. Then the subsequent flame involved in the vortex and the turbulent flame generates.The conclusions have certain theoretical significance to the item placement rules and the structural design of the hole under the mine. And they are also useful to enrich and improve gas explosion theory. |
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