Study On Control Effect Of Mechanical Ventilation And Water Mist In Underground Garages

Car convenient for people to travel,improve the quality of life at the same tight parking spaces has become a social focal point for urban development need governance.Rational use of underground parking space construction can effectively solve the problem of urban parking and land resource constraints contradiction.At present,China's increasing emphasis on the use of underground space,development of underground garage is also very fast.With the development of spatial structure technology underground garage increasingly complex,single area has continued to grow,underground garage fire suppression method of enhancement requests is also increasing.As a new environmentally friendly water mist extinguishing technology,but also has a gas fire and water fire dual advantages,it has great significance for the study of water mist fire suppression technology.In this paper,a fire laboratory prototype Underground Engineering,Northeastern University,the use of FDS fire dynamics simulation software to simulate the experimental system and experimental data were analyzed.The results showed that:FDS numerical model calculations and experimental measurement points corresponding temperature curve fit is good,simulation results can be taken high reliability,can be extended to calculate other parameters of the fire scene and acquisition.The simulation results show floor open space with the law of development of different fire,confined space after the occurrence of flashover fire appeared to walk.The case of underground ventilation is restricted,and fuel combustion amount of smoke in the direction of height can be divided into the upper portion of the high temperature and low temperature cold hot gas layer zone.Computer simulation program to establish dual-zone model numerical calculation is reasonable.Near the flame zone temperature is higher,with increasing distance from the source of fire,the space environment temperature dropped significantly.Flame burning zone temperature curve was centered symmetrically distributed.By analyzing combustion characteristics of rubber materials,and changes in radiative heat flux in the fire surface temperature and the room is when the rubber is ignited hot gas layer and the average temperature of the space radiation heat flux was accepted to meet flashover occurred in critical condition.By FDS fire dynamics simulation software to model the size of the numerical simulation of the evolution of fire 106m 42m 7m of two underground parking garage of a shopping mall,the analysis is limited in building underground complex environment,with the development of fire smoke distribution and Variation floor space and fire a study of energy.In this set of conditions did not inhibit mechanical ventilation flashover occurs,but effectively reducing the heat release rate and the average temperature of the smoke layer.Makeup air oxygen into the combustion reaction will intensify.Fire reasonable temperature fire damage assessment is the basis for the partition,the fire in the height direction have significant temperature stratification,can be divided into hot and cold hot gas zone area can be divided into the direct flame fire heat by the horizontal direction the role of the flame zone;fire near a fire source by source heat radiation of the temperature region;and cold air farther away from the fire source area.By analyzing the isotherm plot height in different directions on the scene,according to concrete physical and chemical changes in the fire was a reasonable partition provides data support for fire damage assessment.Using the same model for comparative analysis of distribution and change and without water mist fire extinguishing action space temperature field,the evidence of inhibition of water mist fire crashing underground garage.In the mist conditions herein set effectively inhibit the occurrence of flashover,not only reduces the heat release rate of the fire source directly reduce the fire source temperature,and effective absorption of the heat of the flue gas layer,the hot smoke layer the average temperature controlled at below 400?,to prevent the spread of fire.Water mist to flow field flow field disturbance promotes regional turbulence,enhanced heat exchange between regions,the temperature fluctuations but there is still significant stratification phenomenon versus time,while small water fog can effectively cut off heat radiation,preventing the fire source adjacent combustibles ignited by high temperature thermal radiation.