Study On Synergistic Inhibition Of Wire Mesh And Inert Gas On Methane Explosion Mechanism

In the safe extraction,transportation,storage,utilization and other links of methane,if there is gas leakage or open flame,it will cause serious consequences.Therefore,it is very important to deeply explore the method of explosion suppression of premixed gas.In this thesis,the mechanism of the explosion propagation characteristics of 9.5%methane-air premixed gas affected by wire mesh and carbon dioxide was deeply studied through numerical simulation,and the law of explosion suppression was summarized,which provided data support for improving explosion suppression measures and equipment optimization.In this thesis,the inhibitory effect of wire mesh on the explosion of 9.5% methaneair premixed gas was studied experimentally.The explosion overpressure,the fitting curve of the peak attenuation rate of the overpressure and whether the flame quenched through the wire mesh were analyzed to characterize the effect of the wire mesh structure on the explosion inhibition of methane.The study found that with the superposition of the number of layers of wire mesh and the increase of the mesh number,the explosion overpressure in the tube attenuated,and the time to reach the peak overpressure gradually shortened.Among them,when the wire mesh was 80 mesh and 6 layers,the inhibition effect was the best,and the peak overpressure attenuation reached 47.24%;the different parameters of the wire mesh showed two different effects of suppressing and promoting the explosion reaction.Under the conditions of 30 mesh 4 layers,12 mesh 6 layers,and30 mesh 6 layers,although the blockage reduced the spread of the upstream flame on the wire mesh,but due to the failure of flame quenching,part of the flame penetrated the wire mesh and continued to spread forward.After a short delay,the explosion occurred again,and two obvious peaks appeared.At this time,the excitation effect of the obstacle on the flame led to the intensification of turbulence,and the effect of suppressing the explosion changed to the effect of promoting the explosion.Secondly,with numerical simulation as the main means,LES was used to establish a numerical model to simulate the inhibition of methane explosion by wire mesh and inert gas alone,and the explosion inhibition performance of carbon dioxide and nitrogen was compared and analyzed.The study found that the explosion suppression law of the wire mesh treated as a porous area was similar to the experimental results,and the model was reliable;the explosion inhibition effect of single-phase carbon dioxide as an inhibitor was better than that of nitrogen.When 20 %carbon dioxide and 32 % nitrogen were added into the system respectively,the explosion inhibition effect of methane was the most significant.Finally,a simulation study on the synergistic suppression of methane explosion by metal mesh and carbon dioxide was carried out.The study found that the explosion suppression effect was better when the metal mesh and carbon dioxide were used together than when they were used alone.The two have a synergistic effect on the suppression of methane-air premixed gas explosion.Among them,under the conditions of 16 % carbon dioxide and 80 mesh wire mesh,the two had the best explosion suppression effect.Under this condition,the flame front velocity was 8.05 m/s,and the explosion overpressure was13.13 kPa,and compared with 9.5% methane-air premixed gas,it decreased by 64.29%and 75.54% respectively.The heat absorption and cooling capacity of carbon dioxide and the cold wall effect of pore wall caused the heat in the reaction zone to be absorbed and the reaction rate to reduce.At the same time,the wall effect of the mesh destroyed a large number of free radicals,carbon dioxide reduced the concentration of free radicals in the system.The ternary collision transferred the energy carried by free radicals,resulting in the slow down or interruption of the chain reaction process.In addition,a large number of non-uniform pores in the network structure not only blocked the influence of thermal radiation on the preheating of unburned gas,but also inhibited the generation and development of shear wave.Therefore,there was a good synergy between carbon dioxide and metal mesh.