The Research On Smoke Exhaust In The Atrium Of Malls Based On The Presence Of Combustible Materials

The Atrium of a shopping mall with a large number of combustibles is used as the research object,and the FDS fire numerical simulation software is used to model and analyze the numerical changes such as flue gas settlement height,temperature,carbon monoxide concentration and visibility in the shopping mall,in this paper.A 5-story shopping mall with a building height of 25 m was used as a physical model,and a total of 61 sets of fire scenes were set up to obtain the influence of fire source power,window opening area and window opening position on the smoke exhaust effect during natural smoke exhaust;The effects of fire source power and smoke exhaust system distribution on smoke exhaust effect during mechanical smoke exhaust,the results of the research show:(1)Field investigation of combustibles in the atrium of the mall,a one-year investigation of the type and time occupied by the atrium of the mall,statistics on the volume and quality of combustibles,and reference to the calorific value calculation formula of the material to obtain the fire load density of the combustibles in the atrium.The most unfavorable value of the fire source power is set to 12MW,and according to the different fire load density quantiles,the three sets of fire source power are designed to be 8MW,10MW and 12MW.With the increase of the fire load of the accumulated combustibles,the visibility,temperature,and toxic gas concentration on the top floor of the shopping mall atrium will also be shortened,which indicates that the increase of the fire load will adversely affect the smoke exhaust and evacuation of personnel in the early stage of the atrium fire,and the storage of combustible materials in the atrium should be paid attention to.(2)The natural smoke exhaust effect of the atrium will change depending on the position of the window,and the top window position of the atrium is located in the middle of the atrium,and the smoke exhaust effect is better than that of the surrounding area,under the same fire source power.In the design,attention should be paid to setting its open window near the middle,and when the fire occurs,the flue gas rises from buoyancy to the top of the atrium,reduces the spread and settlement to the surrounding area,and directly discharges from the smoke exhaust window,shortening the smoke exhaust time and improving the efficiency of smoke exhaust.(3)The natural smoke exhaust at the top of the atrium increases with the window area of natural smoke exhaust,and the arrival time of dangerous temperature,visibility and toxic gas concentration are delayed under different window area comparison conditions.The natural smoke exhaust can enhance the smoke exhaust effect by increasing the window area.(4)In the case of a fire with a large number of combustible materials in the atrium,the area of the exhaust window designed according to the"Technical Standards for Building Smoke Prevention and Exhaust System"is not enough to discharge the smoke in the atrium at the beginning of the fire,so as to ensure that the flue gas settlement in the atrium is above the safe height.When the natural smoke exhaust window area of the atrium accounts for 14%of the atrium area,the smoke settlement height,critical temperature,visibility and toxic gas concentration in the atrium are not higher than the critical value at the initial stage of the fire,and when the fire shutter fails,all indicators in the top staircase do not exceed the critical value.Therefore,the area of the natural smoke exhaust window of the atrium can be set to not lower than 14%of the atrium ground to optimize the smoke exhaust effect.(5)In case of fire with a large number of combustibles in the atrium,according to the smoke standard,the smoke exhaust volume of 105000 m~3/h in case of fire in the atrium is not enough to reasonably discharge the smoke in the atrium under the action of high-power fire load in the atrium.According to the calculation,it is proposed that in case of fire with a large number of combustibles in the atrium,the mechanical smoke exhaust volume should be greater than 225000 m~3/h,so as to ensure that the smoke settlement in the atrium is above the clear height and meet the safe evacuation of personnel.