Study On The Effect Of Smoke Control On Antechamber Positive Pressure Ventilation In High-rise Building Fire

With the fast development of social economy and implementation of urbanization strategy, high-rise buildings are getting more popular. As it has these characteristics including complicated internal function, many pathways of fire spread, personnel evacuation difficulty and so on, high-rise civil office building fire has become an important research direction in domestic and international fire protection scientific and technological field. Toxic and high temperature smoke released from high-rise building fire is a major factor causing a lot of death. Therefore, strengthening the study of smoke prevention and exhaustion in high-rise building has an important practical significance to reduce fire casualties and property losses.Through the analysis on the comparison of the characteristics of various fire models and the scope of application, numerical model is established with field model FDS and smoke flow of corridor-antechamber zone of the fire floor is simulated in high-rise building fire by use of LES method. The paper focused on the analysis of the following aspects:to discuss the effect on control the smoke in antechamber by changing the main parameters of antechamber positive pressure air supply system when the second door of antechamber is in a open state partly, such as different fire power, different air-supply volumes, different sizes of outlet, different heights of outlet; to study the effect on control the smoke in corridor and antechamber by natural smoke exhaust and mechanical smoke exhaust under antechamber positive pressure ventilation; the effectiveness of fire smoke control is verified by numerical simulation through setting buffer zone between corridor and antechamber. The distribution and variation law of major components within fire smoke, the concentration, temperature, visibility is studied and analyzed basing on the above situation, which lies in the first door nearby of antechamber (people assemble zone in evacuation passageways) and at the horizontal height of1.6meters (human eye’s feature height) of central line of corridor monitor points. The results are as follows:different fire power and air-supply volumes have significant effect on the concentration of CO and CO2, temperature, visibility. When air-supply volumes are certain, reducing the section area of outlet properly can help improve the effectiveness of positive pressure ventilation. Different heights of outlet in high-rise building antechamber have different effects on smoke control. When air-supply volumes and the section area of outlet are certain, raise the center height of outlet can help improve the effectiveness of positive pressure ventilation. In natural smoke exhaust conditions, the concentration of CO content in fire smoke is higher relatively in corridor of the fire floor, and the performance is more obvious with high fire power than low. In mechanical smoke exhaust conditions, the concentration of CO content and temperature of smoke both increased at the beginning, then decreased and went up again within six hundred seconds, which is slightly better than the effect of natural smoke exhaust for its buffer action to personnel evacuation in certain extent. And after setting buffer zone between corridor and antechamber, there is almost no effect on the concentration of smoke, temperature, visibility in the buffer zone and antechamber by fire, which is an effective means to strengthen the effect of controlling fire smoke in corridor-antechamber zone of the fire floor and has more obvious advantages than natural smoke exhaust and mechanical smoke exhaust.The above results provide an analyses path for evaluating the effect and mode of controlling smoke of corridor-antechamber zone in high-rise building and a certain reference and theoretical support to the high-rise buildings performance smoke control design and personnel evacuation.