Law Of Temporal And Spatial Evolution Of Gas Explosion Hazard And Prevention And Controlling In Utility Tunnel

As one of the important symbols of the new urban municipal infrastructure construction in the 21 st century,the utility tunnel has the function of improving the urban function and enhancing the comprehensive capacity of the city.With “Technical Code for Urban Utility Tunnel Engineering”(GB 50838-2015)and the 2016 Meeting of the Ministry of Housing and Urban-rural Development to promote the construction of utility tunnel,the relevant requirements of "gas pipeline entering into the utility tunnel" are clarified.Once a gas leakage occurs inside the tunnel,it will pose a serious threat to urban security development and social stability.To study the temporal and spatial evolution law of gas explosion hazard in the utility tunnel and corresponding prevention and control strategies is of great significance for its safety operation.The main research contents are as follows:(1)Small scale experiment and numerical simulation validation.Based on the small scale methane explosion experimental platform built by ourselves and the large scale methane explosion experimental data in literature,the corresponding numerical model was established by using FLACS software.The simulation results were in good agreement with experimental data,which verified the effectiveness and applicability of the numerical method.(2)Analysis of spatial and temporal evolution law of gas explosion disaster in utility tunnel.The numerical model of gas explosion in the utility tunnel was established,the grid sensitivity was analyzed,and the optimal grid was determined.The temporal and spatial evolution of the explosion overpressure,flame and temperature when the tunnel is partially filled with premixed gas cloud was analyzed.The results show that the overpressure value and the overpressure amplitude at the end of the tunnel are larger than those at other positions due to the superposition of overpressure reflection.Gas explosion in the utility tunnel is typical deflagration and the length of flame zone is much longer than that of the premix zone.The explosion peak temperature decreases with the increase of distance,and the length from the ignition end to the position of temperature drop is consistent with the length of the flame region.(3)Analysis of the influence of different factors on the temporal and spatial evolution law of gas explosion in the utility tunnel.The results show that the increase of pipeline number and premixed gas cloud volume will increase the explosion overpressure and flame velocity.The influence of ignition source location on overpressure and flame velocity is more obvious on the other closed end than the ignition end.When the concentration is slightly higher than the stoichiometric ratio,the explosion consequence is more serious.However,these influencing factors have little effect on the peak temperature.(4)Gas explosion prevention and control in the utility tunnel.The effects of vent and pressure relief plates on the reduction of explosion consequence when the tunnel is full of premixed gas clouds were studied.The results show that the setting of vent has a significant effect on the reduction of the peak explosion overpressure and peak temperature in the utility tunnel.The larger the aspect ratio,the smaller the peak overpressure and the bigger the flame velocity.The higher the opening pressure of the pressure relief plates,the higher the peak overpressure and peak temperature.The flame velocity first increases and then decreases with the increase of opening pressure.