Research On Characteristic Of Long-Distance Ventilation And Fire Fighting Of Urban Utility Tunnel

With the development of the city's comprehensive pipe corridors,the impact of the wind pavilion that frequently exposes the ground on the appearance of the city and the impact of fan noise on the surrounding residents is becoming more and more serious.In order to reduce the number of wind tunnels on the city's ground,it is the most straightforward way to increase the length of the ventilation zone of the pipe gallery,but blindly increasing the length of the ventilation zone also has many negative effects,such as excessive energy consumption and more power.Fans bring more serious noise effects and so on.Therefore,this paper studies the key technologies of long-distance firefighting and ventilation of urban comprehensive pipe corridors through numerical simulation + field experiments.The main research contents and research conclusions are summarized as follows:(1)The CFD software Fluent is used to study the long-distance ventilation of the pipe corridor.The normal ventilation conditions of the cable compartment and the smoke exhaust conditions after the disaster were studied respectively.The relationship between the average wind speed,local resistance,total resistance of the ventilation and the length of the ventilation section is analyzed;the distribution law of the cross-section wind speed in the middle of the cabin(non-ventilation-affected section);In addition,the effect of the size of the fire door on the total ventilation resistance was also studied.It is found that the total ventilation resistance is composed of local ventilation resistance and extended ventilation resistance,and the local ventilation resistance accounts for a relatively high proportion.The greater the length of the ventilation interval,the greater the local resistance and the total ventilation resistance,and there is an exponential function relationship with the length of the ventilation interval.By increasing the area of the fire door to 1.37 times the area of the original size fire door,the ventilation resistance can be reduced by more than half.(2)Use FDS software Pyrosim to study the smoke exhaust ventilation across the fire door.By numerically simulating the two stages of fire combustion in the cable compartment with a ventilation area of 400 m and smoke exhaust ventilation across the fire door,the diffusion of smoke in the cable compartment and the decrease in visibility caused by the smoke were studied in these two stages The temperature distribution and change law of the ignition zone,the adjacent fire zone,and the compartment next door in the two stages were studied.The oxygen,carbon dioxide,and carbon monoxide content changes in the fire zone and the adjacent fire zone in the two stages were studied.During the smoke exhaust ventilation,the high-temperature smoke caused by the cross-fire door ventilation has a small impact range.Only the section within 27 m near the fire door will have a maximum temperature of 40 ?,and the temperature in most sections is still within the human body's suitable range.There was no obvious change in the temperature of the comprehensive compartment next door,and the temperature change in the middle of the compartment was less than 0.1 ?.It shows that the concrete partition wall with a thickness of 0.3m is enough to block the influence of a certain scale of cable fire on the temperature of the next compartment.(3)FDS + EVAC was used to establish the coupling model of fire and evacuation to study the evacuation of cable cabin personnel.Twenty cases were simulated,namely the evacuation of 10,20,30,40 and 50 persons in the 200 m,250m,300 m and 350 m fire zones.Mainly studied the influence of the number of personnel and the length of the fire compartment on the speed of evacuation of personnel in the cable compartment fire.And by analyzing a special case,the process of tube corridor fire causing death was studied.The behavior of the personnel in the cable fire and the whole process of death caused by the fire are obtained.When the length of the fire compartment is constant,the more people in the cable compartment,the longer the probability of evacuation time.When the same number of people are distributed in different lengths of fire prevention intervals,the longer the fire prevention interval,the longer the probability of evacuation time is,and the growth rate is large.(4)Through field experiments,six different working conditions were drawn up,and the length of the ventilation section and the ventilation method(mechanical air intake + mechanical exhaust air,mechanical air intake + natural air exhaust,natural air intake + mechanical air exhaust)were studied respectively.The influence of wind speed distribution and resistance of pipe corridor ventilation.It is learned that if the ventilation method of the pipe gallery cabin is a combination of natural air outlets and mechanical air outlets,the change trend of wind speed must be decreasing from the mechanical air outlet to the natural air outlet.If there is a branch pipe corridor along the way,the cross-sectional wind speed of the branch pipe corridor will decrease to a certain extent.The reduction depends on the cross-sectional area of the branch pipe corridor,that is,the amount of air shared by the branch pipe corridor.And the change of ventilation mode has little effect on ventilation resistance.