Study On Suppression Of Gas Explosion Propagation In Confined Space By Co-effect Of Cavity With Water Mist

Once coal mine gas explosion occurs,it will produce a large number of high temperature flame,poisonous gas and huge shock wave overpressure in an instant,and it will spread rapidly in confined space,destroy surrounding facilities and cause a large number of casualties and property losses,resulting in the extremely bad social impact.Therefore,it is of great scientific significance and application value for prevention and control of gas explosion accident in coal mine and underground pipe gallery to explore a new type of explosion suppression materials,explosion suppression devices and fire retardant materials,to avoid explosion or reduce explosion intensity as far as possible.By means of theoretical analysis,experimental study and numerical simulation,the propagation of gas explosion suppression by cavity and its mechanism,the synergistic effect of cavity with water mist and its performance are systematically and deeply studied in the study.The main findings of the study are as follows:(1)The basic equations of shock wave front were established on the basis of the conservation laws of mass,momentum and energy,the formulas for calculating shock wave front parameters were derived,and the wave front equation of shock wave when shock wave collides with each other during propagation,chasing and reflecting on rigid wall was obtained.The wave front parameter formula of explosion in the case of sudden change of cross section was derived,it is concluded that the shock pressure will attenuate when the shock wave enters the larger cross-section tunnel from the smaller cross-section tunnel,and will accelerate the attenuation process when the cross-section area of the tunnel change is great.The influence of reflected wave on the propagation of combustion wave was analyzed,and it is found that when the reflected wave meets the combustion flame,it will obviously restrain the propagation of the flame and even cause the flame to extinguish,the degree of influence is related to the intensity of reflection wave,the propagation speed of combustion wave and the structure of pipeline.(2)The experimental study on suppression of gas explosion propagation was carried out on 8 different cavities with different volume and ratios of length to width:0.03 m3(5/3,3/5),0.05 m3(5/2,1,4/25)and 0.08 m3(8/5,5/8,1/10),respectively.The results showed that the cavities with ratio of length to width 4/25(volume 0.05 m3),5/8(volume 0.08 m3)and 1/10(volume 0.08 m3)have effect on explosion suppression,and the explosion suppression performance of cavity with the ratio of length to width 1/10 is the best among the studied cavities.(3)The numerical model was established under the same conditions as the experimental study,and the numerical simulation of gas explosion propagation suppression in 12 cavities with different aspect ratio of 0.03 m3(aspect ratio 5/3,3/5,4/15),0.05 m3(aspect ratio 5/2,1,4/25)and 0.08 m3(aspect ratio 5/2,8/5,1,5/8,2/5,1/10)was carried out.The numerical simulation results are in good agreement with the experimental results,which shows that the numerical model,numerical method and mesh generation are reasonable,and the results of numerical simulation also verifies the correctness of the formulas for calculating attenuation coefficient of overpressure and flame velocity.The mechanism of suppressing gas explosion propagation in the cavity is revealed,on the basis of simulation of explosion flame and shock wave propagation process in the cavity.(4)The explosion suppression experiments were carried out with different cavities and water mist by using the three kinds of cavities with explosion suppression performance with length×width×height of(200×1250×200,200×2000×200 and 500×800×200)respectively.It is found that the co-effect of cavity and water mist has better explosion suppression performance,and its attenuation performance for shock wave is better than that for shock wave overpressure.The attenuation range of shock wave overpressure,flame size and flame velocity at the outlet of the cavity is the largest,followed by that at the inlet of the cavity,and slight at measurement point before rupture of the membrane.The study found that cavity with length×width×height of(500×800×200)and water mist has the best synergistic performance of explosion suppression.When the spray lasted for 45 seconds,the attenuation rate of shock wave overpressure,flame size and flame velocity at the outlet of the cavity reached 46.7%,98.7%and 56.6%respectively(compared with the test without water mist),and the flame almost disappeared.(5)On the basis of the experimental data analysis,it is found the law that the length of the cavity and the spraying time of the water mist effect on the synergistic performance of explosion suppression.The length of water mist can be increased by increasing the length of cavity,and the effect time of water mist with explosion shock wave and combustion wave can be prolonged to increase the effect of explosion suppression.The concentration of water mist in the cavity can be increased by prolonging the spraying time,thus the explosion suppression performance can be improved.However,with falling of water mist and coagulation caused by increase of water mist concentration,the water mist concentration will not continue to increase after reaching a certain concentration.In the experiment,the optimal spraying time was 45s.The research results provide a new technical way for explosion-proof and explosion-suppression of combustible gas in underground coal mines or underground pipe tunnels.Figures[94]Tables[51]Reference[98]...