Study On Synergistic Inhibition Of Ultra-fine Water Mist And Porous Media On Gas Explosion

With the change of energy supply structure in China,the development of unconventional natural gas has solved the problem of energy security in China.Gas is a potentially dangerous substance produced in the process of coal mining,but is can also be used as clean energy and unconventional natural gas to reduce its pollution to the environment.However,in the process of gas extraction,transportation and storage,once leaking or encountering open fire will cause serious consequences,so how to effectively suppress the spread of gas explosion is particularly important.In this paper,the mechanism of the influence of ultra-fine water mist and porous media on the propagation characteristics of gas explosion was deeply explored through experiments and numerical simulation,and the law of synergistic inhibition was summarized and the mechanism of inhibition was discussed.It can provide some technical support for improving the explosion suppression measures and equipment in the process of gas transportation.In this thesis,the suppression of 9.5%methane-air premixed gas explosion by ultra-fine water mist and porous media was studied by two parts of experiments.The flame structure,flame front propagation velocity and explosion overpressure were emphatically analyzed.First of all,the study of porous foam metal and ultra-fine water mist synergism inhibited gas explosion.It was found that with the increased of ultra-fine water mist concentration,the peak value of flame front propagation velocity decreased gradually,the explosion overpressure decreased little by little,and the occurrence time of the explosion overpressure peak was also shortened.With the decreased of pore size of porous materials,the flame front propagation velocity decreased and the pressure attenuation rate increased obviously.Under the conditions of ultra-fine water mist concentration 1453.1 g/m~3,porous material porosity 87%and pore density 20 PPI,the inhibition effect was the best.Compared with 9.5%methane/air premixed gas,flame front propagation velocity and explosion overpressure were reduced by 44.23%and 40.62%,respectively.Secondly,the synergistic suppression of gas explosion by one-dimensional porous media and ultra-fine water mist was studied.The study found that the trend was similar to that of porous materials and ultra-fine water mist.However,when the pore size of porous media was too large,which like an obstacle.Although the flame propagation in the upstream of porous media was blocked and reduced,the flame passing through the porous media caused quenching failure,and the turbulence intensifies,which leads to an increase in risk,and changes from explosion suppression to explosion promotion.With the increased of ultra-fine water mist concentration,the quenching ability of porous media could be improved,and the flame can not pass through porous media.The effect of synergistic suppression of gas explosion was better than that of single suppression method.Finally,the EDC model and the LED model were used to simulate the co-suppression explosion of ultra-fine water mist and porous media.The simulated flame structure,the trend of flame propagation velocity and the trend of overpressure rise were similar to the experimental results.The results shown that the addition of ultra-fine water mist absorbs a large amount of heat energy in the reaction zone and reduces the reaction rate.In addition,when the explosive shock wave was incident on the surface of the porous material,most of the shock wave entered the porous medium along the porous channel,and the shock wave was continuously reflected and consumed in the porous medium.This effect enables the porous medium to effectively absorbed part of the precursor shock wave and destroy the positive feedback mechanism.The existence of porous media increased the blockage rate of pipeline and results in the blockage of gas flow.Turbulence in porous media area was very obvious,which only affected the propagation speed of flame front,but does not change the flame structure.There was a good synergistic effect between ultra-fine water mist and porous media.