Numerical Simulation And Experimental Study On Typical Gas Combustion And Explosion In Urban Road

At present,the urbanization of China is in the stage of accelerating development,and the problem of urban public safety is becoming more and more prominent,in recent years,Urban Road gas burning and explosion accident(including the jet fire caused by the damage to the low pressure gas pipeline and inspection well explosion because of the leakage gas or biogas meets fire)occurred frequently,the accidents caused casualties,property loss and bad social impact.In order to reduce the losses caused by the accident,this paper focuses on the law and the degree of influence of initial conditions to the consequences of the accidents,the numerical simulation of Jet fire of medium and low pressure gas pipeline is carried out,inspection well explosion accident were studied with numerical simulation and full size experiment.The main contents and conclusions are as follows.1)The theoretical knowledge of gas combustion and explosion are generalized and summarized,the main characteristics and damage forms of the two types of accidents studied in this paper are analyzed,and the damage criteria related to thermal radiation and shock wave overpressure have been arranged.2)According to the typical accident case,the town road buried gas pipeline leak scene is set up,geometric model was established and the model was divided into the grid,Fluent is used for simulation calculation.The jet fire flame temperature distribution,jet fire flame length and the heat flux in the adjacent area under the condition of different leak port apertures,different break shapes and different pressures in the pipe were obtained.By comparing data of different working conditions,it is found that the length of this kind of jet fire can reach tens of meters,the maximum temperature of the flame is about 2000 K and the height of the maximum temperature location does not exceed 30%of flame length.When the leak port area is 19.6 cm~2 and pressure in gas pipeline is 0.38 MPa,in the downwind direction,the heat flux of the shuttle-shaped leakage port is 15.2%larger than that when the shape of the leakage port is round.When the horizontal distance between the observation point and the leakage is less than 10 m,the heat flux of the downward wind is stronger than that in the other directions,heat flux in the vicinity of the flame and the leak port aperture have a positive correlation,however,with the decrease of the pressure in pipe,the heat flux decreases first and then increases.3)After analysis different conditions of jet flame length and the heat flux data,a rapid risk assessment model for heat radiation damage for medium and low pressure gas pipelines is proposed,whose input parameters are the length of the flame,the time of the people exposed to the heat radiation and the distance of people from the leakage.4)Based on the theoretical calculation and numerical simulation(Fluent,AUTODYN),the inspection well explosion was studied and it was found that under the premise of relatively complete reaction of combustible gas and air in the inspection well,the peak value of shock wave overpressure decreases with increasing distance from the center of wellhead,the bigger of the depth of the inspection well,the greater of ambient shock wave overpressure peak of the inspection well around.5)The design of the inspection well explosion experimental working conditions is based on the methane volume fraction,the ignition position,the weight of the inspection well cover and the volume of the inspection well,effective data of 14 working conditions are obtained by experiments.The results of the experiment under experimental condition show that:The inspection well explosion shock wave maximum peak overpressure is not the monitoring point from the center of the nearest manhole,the maximum overpressure peak value of the shock wave is within the range from 1 m to 1.5 m from the center of the wellhead,and the reasons for this rule are analyzed;the consequences of the explosion are the most serious when the volume fraction of methane in inspection well is 10%(stoichiometric ratio is 9.5%),when the volume fraction of methane is 12%,the consequences of the explosion is more serious than that of the methane volume fraction of8%;The ignition position is far away from the bottom of the inspection well,the explosion shock wave peak overpressure is smaller,the amplitude of the reducing increases with the increase of distance between the ignition position and inspection well bottom;the more heavy the cover of the inspection well is,the greater the pressure relief values,the more serious the consequences of the explosion;the inspection well explosion risk control recommendations is put forward based on experimental results.6)Comparing the respective advantages of the simulation and experimental methods to the explosion of inspection well.Simulation methods can more fully reflect the severity of the consequences of the accident,while experimental methods can show the special law of the variation of the peak pressure of the shock wave with the distance,and combining two methods can accurately assess the consequences of the accident.