Experiment And Numerical Simulation Of Mitigating Methane Explosion By Ultrafine Water Mist

In recent years, gas explosion accidents in mine occurred frequently which seriously threatened the lives of mine workers and brought a great burden to the enterprises and society. So the emergence of an effective explosion suppression technology becomes extremely urgent. As a new type of explosion suppression media, because of its many advantages, ultrafine water mist has already got the attention of a large number of scholars. In this paper, both the experimental and simulation methods were used to study the mitigating effect of ultrafine water mist and influencing factors, and the preliminary analysis of the inhibition mechanism was done. The purpose of this paper is to summarize the suppression laws of ultrafine water mist and to provide a theoretical analysis basic for industrial applications.Firstly, the experiments of mitigating methane explosion by ultrafine water mist were conducted in a closed0.02025m3rectangular container, explosion overpressure development laws and flame propagation images under various experimental conditions were got. On this basis, the three-dimensional numerical simulation of mitigating explosion by ultrafine water mist was conducted, and we used the simulation results to analyze the change of flame temperature and morphology, as well as flow characteristics of flow field.By analyzing experimental and numerical simulation results, we can obtain the following conclusions:(1) When methane explodes, flame propagation speed first increases, then decreases, and finally tends to fluctuate, and the volatility trend will remain until the explosion ends. The appearance of tulip flame structure has some connections with the large-scale eddies’s motion near the flame.(2) After adding ultrafine water mist, the intensity of methane explosion lowers significantly, both the maximum explosion overpressure and the maximum flame propagation speed reduce, and the pressure rises slowly. When the amount of water mist reaches a certain-value, the explosion will be completed suppressed. The color and transparency of flame and combustion products zone change, and the temperature decreases. The overall trend of flame propagation speed does not change, but the flame acceleration process becomes slower. When the amount of water mist is large enough, tulip flame structure disappears. In the whole explosion process, the flow direction of unburned gas ahead of flame is always consistent with flame propagation direction. The flow direction of combustion products behind the flame is consistent with the flame propagation direction at the early stage of explosion, but is opposite at the late stage.(3) The heat of flame is absorbed by ultrafine water mist, which causes a decline of flame temperature and propagation speed. While water vapor dilutes oxygen concentration in the unburned area, which would make a choking effect on combustible gas.(4) The main factors affecting the inhibitory effect include the amount and particle diameter of water mist. When the amount of water mist is lager, the inhibition effect is better. When the amount of water mist is fixed, the inhibitory effect of water mist with15μm particle diameter is best.