Study On The Effect Of Different Factor On Smoke Control Using Negative Pressure Produced By Shaft

In order to provide people with all kinds of office, living, entertainment, high-rise buildings have sprung up in the case of limited land resources. It is very convenient for people and they can have a good time when they are free. Although high-rise building has many advantages, it also has a great potential safety hazard from the fire accident occurred in recent years. Due to the existence of elevator shaft, stairwell, vertical channel pope wells and other vertical shaft in high-rise building, once the room fire, the smoke will spread quickly through the shaft. For the fire accidents, the main factor that causing casualties is the hot flue gas generated by the fire. But the evacuation is very slow, the firefighting and rescue work is very difficult in the high-rise building, so it is important to control the smoke and confine it within a certain range.The stack effect is the main driving force in the high-rise building when the fire happens. The hot smoke flow into the shaft, and spread outside because of the difference in temperature of inside and outside. As the room connected with a shaft in high-rise building and the room fire, the negative pressure will produced at the bottom of the shaft and the room due to the stack effect. It is to say, the pressure in the room is smaller than the pressure outside, the smoke cannot overflow form the air-supply opening, it just spread out from the shaft. So injuries can greatly reduce and protect the safety of people. In the real life, the chimney was used to smoke as a channel, so the hot smoke can be controlled by using the shaft correctly. The feasibility of smoke and control the smoke by using the shaft are studied by some domestic researchers. The results proved that the hot smoke can be controlled by take advantage of the shaft structure in high-rise building. The stack effect can influenced by many factors, the research about how to use the shaft reasonable is very less. This paper mainly studies the effect of the various factors on the smoke control by using negative pressure.According to the theory of stack effect, the influencing factors are analyzed and the critical condition for confine the smoke within the fire room is obtained. It can be seen form the analysis, the main factors is the power of fire, the shaft height, ventilation factor, the area of the smoke vent. The critical value of influencing factor can be calculated by the formula.By using the CFD simulation, establish a model and set a series of cases through changing the shaft height, ventilation factor and the area of the smoke vent. The temperature, pressure, velocity in the shaft and the air-supply opening as well as the indoor temperature are measured and analyzed, and then the effects of the shaft height, ventilation factor and the area of the smoke vent on the stack effect are studied respectively. It can be known that the smoke overflow or not from the mount of smoke overflow under different conditions. So the effects of the shaft height, ventilation factor and the area of the smoke vent on the smoke control are researched. The static pressure value between the top and bottom of the shaft is calculated, and compared with the negative pressure value from the simulation, it can be found that the result of the simulation is reliability. The critical values of the shaft height, ventilation factor and the area of the smoke vent are calculated respectively, and compared with the results of FDS simulation, so the critical condition of control the smoke overflow is verified.Through the transformation of small size1/3stairwell experiment platform, established a small scale shaft model. A series of experiments are carried by changing the size of oil tank and air vent. By measurement and analysis of temperature, pressure, velocity in the shaft and air vent, the effect of the fire power on the smoke control is studied, and the influence of the ventilation factor on the smoke control is analyzed.