Experimental Study On Temperature Attenuation And Smoke Deposition Of Circle Section Utility Tunnel Fire

As the urbanization process continues to advance,the construction of the utility tunnel is imperative.As an infrastructure to ensure the normal operation of the city,the utility tunnel will have a very serious impact in the event of a fire.Therefore,it is of great significance to explore the fire behavior of utility tunnel,find out the temperature distribution and smoke spreading process in the utility tunnels under fire conditions,and provide theoretical support for the early warning and rapid extinguishing of fires in urban underground utility tunnels.In this paper,a small circular section utility tunnel is used as the experimental platform to study the longitudinal temperature attenuation,maximum flue gas temperature of ceiling and flue gas settlement process,and the experimental scheme is determined.During the experiment,weight sensor,temperature acquisition system,laser source and image acquisition system were used for data recording.By analyzing the longitudinal temperature curve in the utility tunnel,it is found that the utility tunnel fire with a small leak at the bottom also follows the general fire development law-ignition stage,development stage,full development stage,attenuation stage,and no self-extinguishing phenomenon occurs.In this paper,the thermal boundary layer theory of the tunnel ceiling is used to derive the thermal boundary thickness parameters applicable to the circular utility tunnel.On the basis of determining the thickness of the thermal boundary layer,the formula of the longitudinal temperature attenuation of the jet flow in the ceiling of the circular utility tunnel is derived.Most of the previous formulas were based on the fire in a narrow and long space with a rectangular cross section,and basically did not consider the sealing situation.The calculation formula of temperature decay in this paper is based on the fire under the condition of the circular section tunnel clogging.Therefore,it is more accurate and targeted to use this formula to calculate the temperature decay of the circular tunnel with the bottom leak.In this paper,the previous model is applied to the circular utility tunnel structure,and it is found that the relatively closed utility tunnel is more likely to cause the maximum temperature rising speed higher than the tunnel.The maximum temperature calculation model of the ceiling is fitted,and the formula is(?).It was found that the maximum temperature of the ceiling in the utility tunnel rose at a faster rate.In this paper,based on the previous research results,the formula was adapted to the fire scene of circular section pipe gallery with leaky bottom,and the dimensionless formula to predict the smoke height of pipe gallery fire was deduced as(?).And the calculated results of the formula are in good agreement with the experimental data,which is very practical.This paper has 29 figures,11 tables and 94 references.