Research On Temperature Distribution Of Fire Smoke In Different Forms Of Building Corridors

In most building fires,fire smoke is the main cause of death and injury,and corridor is an important channel for evacuation of people inside the building to the outside.Temperature is an important parameter to characterize the harmfulness of fire smoke.Previous studies had shown that the distribution characteristics of other toxic and harmful gases were closely related to temperature distribution characteristics,when the heat loss of building space was small or the ventilation rate was large,this kind of close connection was manifested in a high degree of consistency in most cases.The study of the temperature distribution characteristics of fire smoke in the building corridor structure has very important guiding significance for studying and judging the distribution of toxic and harmful gases under fire conditions,the selection of personnel evacuation strategies,and the formulation of firefighting and rescue plans.In view of the influence of different fire source heights on the ceiling temperature distribution,previous studies focusd on tunnels with openings at both ends.In the fire research of a corridor structure with one end closed,the former researchers mainly considered the influence of the horizontal distance between the fire source and the end wall on the ceiling temperature distribution.The influence of different fire source heights on the temperature distribution of fire smoke was not considered in the previous full-scale fire experiments concerning the corridor structure with one end closed.Ambient wind has a significant impact on the migration and spread of fire smoke in the corridor.In previous studies on the impact of external ambient wind on the corridor fire characteristic parameters distribution,the ventilation direction was against one opening of the fire source room,utilizing the combustion wind tunnel to simulate the ambient wind field and the ambient wind direction was against one opening of the corridor,in this condition,the influence mechanism of the external wind on the characteristics of the fire smoke temperature field in the corridor structure connected to the fire source room was not clear.In previous studies on the influence of smoke extraction methods on the distribution of fire characteristic parameters distribution in corridor,the main concern was the mechanical smoke extraction based on the smoke extraction shaft,the natural smoke extraction based on the window opening on the corridor wall and the influence of the chimney effect of the shaft.The research on the temperature characteristics of corridor fire through the mechanical smoke extraction system which was formed by reusing the existing shaft structure in the buildings was not considered in the former researchers.Based on these analyses,this paper mainly studied the influence of fire source height,ambient wind,mechanical ventilation on the temperature distribution of fire smoke in the building corridor through full-scale,smallscale fire experiments and theoretical analysis methods.The main research work was as follows:Firstly,in order to obtain the temperature characteristics of the fire smoke layer in the structure of the long passage corridor with one end closed,we chosed to carry out a serious of full-scale fire experiments in a long passage corridor in Hefei,and carried out the corresponding scaled fire experiments.The expressions of the attenuation coefficient of the average temperature rise and maximum temperature rise of the fire smoke layer in the corridor structure considering the influence of the distance between the ignition source and the ceiling was proposed,and the average temperature rise and maximum temperature rise attenuation models of the fire smoke layer in the open and the closed end direction were established.A double-power function model considering corridor width and ignition source height was proposed to predict the combustion strengthening coefficient in the restricted long channel corridor,and revealed the mechanism of combustion enhancement of narrow corridor structure further.The flow field morphology of fire smoke in scaled experiments was obtained by the sheet light source,and the interaction between the return smoke formed after the smoke hit the end wall of the corridor and the incoming smoke was proposed to be the reason for the formation of a larger temperature attenuation rate in the upstream of the fire source.Then,aiming at obtaining the characteristics of the fire smoke temperature field in the corridor connected with the fire source room under the effect of external wind,based on the results from the scaled experiments conducted in the large-scale combustion wind tunnel using fire source room-corridor experimental setup,the influence mechanism of the external wind on the characteristics of the fire smoke temperature field in the corridor structure connected with the fire source room was revealed through theoretical analysis.When the fire room was located on one side of the corridor,the effective heat release rate in the corridor was quantified through theoretical analysis,and the form of the sum of two exponential attenuation function was proposed to predict the ceiling temperature rise along the corridor;Under the condition that both ends of the corridor were open and partially "sheltered",the promotion and suppression effect of the external wind on the smoke overflow behavior from the fire source room was quantified.When the fire room was located in the middle of the corridor,based on the relationship between dimensionless temperature rise and dimensionless wind speed,the influence process of external wind on the maximum temperature of the corridor ceiling was revealed;The change trend of dimensionless temperature rise with dimensionless distance was well fitted by single-phase exponential function.Furthermore,a theoretical model based on dimensionless wind speed was proposed to predict the ceiling temperature in the upstream and downstream directions of the corridor.Finally,scaled experiments were conducted to explore temperature distribution of fire smoke in experimental setup of corridor-front room-shaft.According to the location of fire source,the corridor could be divided into two regions-upstream and downstream region,and the fire smoke temperature beneath the ceiling of the corridor in these two regions was analyzed.It was found that due to the coupling effect of multiple driving force in the upstream and downstream region(pressure caused by the shaft and thermal buoyancy due to fire source),the temperature attenuation below the ceiling incorporated with different fitting functions.Through numerical simulation,it was found that the assumption of homogeneous thermal parameters of fire smoke existed in the horizontal direction of the shaft was not applicable in the condition of relatively large exhaust fan speed.