Research On Smoke Suppression Of Underground Space Fire By Water Mist Curtain

With the emergence of emerging buildings at home and abroad,the fire safety of underground space buildings needs to be further optimized.Fire smoke is the main factor threatening the safety of people’s lives.A convenient and effective fire safety system is an important part of protecting personal and property safety.The application of water mist curtain as a fire separation in underground space can effectively prevent the spread of smoke.Combined with the original smoke control and exhaust system of the building,it has engineering application value to explore the smoke control effect under the joint action of multiple factors.In order to improve the efficiency of building smoke control and exhaust system,starting from smoke control and exhaust design and equipment,fire control optimization strategy and smoke characteristics,theoretical analysis,design optimization and numerical simulation were used to explore the suppression of fire smoke spread in underground space by water mist curtain.With reference to the smoke resistance theory of water mist curtain and drawing on the legend of water mist curtain nozzle,the overall structure of water mist curtain nozzle is deeply analyzed.The internal cavity structure of water mist curtain nozzle and the external nozzle orientation are optimized and improved to form a comprehensive 360°water curtain barrier and prevent the smoke spread in the ceiling space and lower space with high efficiency.Taking a long tunnel as a model,using FDS numerical simulation,combined with the smoke control and exhaust system of the tunnel,the variation of different parameters such as temperature,smoke spread,radiant heat flow gas density,CO volume fraction,smoke optional density,distance between nozzle and ceiling with time was analyzed,and the smoke suppression and fire extinguishing effect of water mist curtain of upper nozzle was investigated.According to the specifications and cases,according to the tunnel structure layout and fire fighting facilities,different working conditions were set to compare the smoke blocking effect of the conventional water mist curtain and the upper spray nozzle water mist curtain.Results show that the flow rate of 12L/min,droplet size is 300 microns,under the condition of the spray nozzle type smoke efficiency of water mist curtain has more efficient than the conventional nozzle water mist curtain,the temperature reduced more than 40%,the tunnel roof CO volume fraction decreases about 33%,significantly lower ceiling smoke density,2m height of gas radiation heat flux density decrease about 47%,and the tunnel coupling effect is better under the action of smoke control system,ground 5m height of flue gas volume fraction with the nozzle decreases with the decrease of distance from the ceiling.The results verify that the upper spray nozzle water mist curtain can be used as a fire separation in the tunnel to prevent the spread of smoke with high efficiency,which provides a reference for the future application research of water mist curtain smoke suppression.On the basis of the research of the upper spray nozzle water mist curtain,the FDS model is established with reference to the actual size of an underground mechanical garage.Starting from the fire influence factors and different smoke parameters,the upper spray nozzle water mist curtain is applied In the underground mechanical garage instead of fire-proof rolling curtains and smoke-blocking vertical walls,the results show that the upper spray nozzle water mist curtain also has a good smoke-blocking and extinguishing effect.The following conclusions are drawn: when the flow rate is 12L/min,the droplet size is 300μm,the nozzle spacing is 1m,and the smoke prevention and exhaust system and the water sprinkler system are turned on,the fire partition of the underground garage is equipped with a fire shutter and smoke prevention efficiency Basically up to 100%,the smoke blocking wall can reduce the temperature at the ceiling by 40%,and the top spray nozzle water mist curtain can reduce the temperature at the ceiling by 65%.Under the same water mist curtain parameters,the smaller the nozzle spacing,the higher the efficiency of reducing the temperature at the top of the garage,and the greater the nozzle flow rate and the better the cooling effect.The gas density of radiant heat flux at the ceiling can be reduced by about 16.7% and the volume fraction of flue gas can be reduced by about 28.6% at the height of 6m.The volume fraction of CO in the ceiling decreases with the decrease of nozzle spacing,and the flow rate of nozzles increases,which has a better effect of blocking the ceiling flue gas.The smoke suppression effect of water mist curtain with upward spray nozzle under different parameters of underground garage is simulated,which provides a basis for the practical application of water mist curtain fitting smoke control system in the future.