The Control Research Of Fire Smoke Of Atrium Buildings Based On The Hybrid Ventilation

With the development of our national economy, the atrium buildings are increasing continuously, fire has become the biggest security hidden danger in an atrium building. The high temperature and poisonousness of smoke and the suffocation are the main reasons causing casualties, so the smoke needs to be controlled and the smoke control system needs to be set to prevent the gas dropping to the bottom of atrium in order to guarantee the personnel safe evacuation. The present research situation of atrium smoke control mode is analyzed systematically in this paper. The study is carried out by the atrium fire smoke flow mathematical model that is established using the two layer zone model, the Fire dynamics simulation software(FDS, Fire Dynamics Simulator) and the 1/10 scale fire experiment. According to the characteristics of smoke flow of atrium fire, the hybrid ventilation that combines natural smoke exhausting and mechanical air supply is proposed to improve indoor smoke environment when the atrium fire happens.Based on the two layer model, the mathematical models of smoke natural filling and natural smoke exhausting are established in this paper, which provides basic theory research for experiment and numerical simulation.The feasibility research that combines top opening natural smoke exhausting and middle-upper side mechanical air supply to prevent the smoke sinking is carried out in this paper. A 1/10 scale model of the atrium is built. The top opening and multiple sets of air supply outlets are arranged on middle-upper part of the walls. Multi conditions of the temperature, wind speed and smoke sedimentation test are conducted. Firstly, the empirical equation that is derived by plume model is used to verify the feasibility of the 1/10 atrium model experiment, and then the model experimental datas and the FDS full-size numerical simulation results are compared to verify the validity of the FDS full-size numerical model. The results of the experiment and simulation show:the temperature rise of smoke is maximum under natural filling; the smoke layer is disrupted and the falling of the smoke layer is fastest under mechanical smoke exhausting; the top opening has well effect on natural smoke exhausting, but the smoke layer is also dropped obviously; under the model that combines natural smoke exhausting and mechanical air supply, the height of the smoke layer is maintained above 0.4m and the personnel safe evacuation is guaranteed when the velocity of air supply reaches 1.3m/s, the range of each side reaches 3/7 of the atrium size along air-supply direction and the fan open time is 30s.In this paper, the fire smoke diffusion in atrium is simulated by using field simulation numerical method FDS based on large eddy simulation theory. For further research of the smoke control mode that combines natural smoke exhausting and mechanical air supply, the idea that uses supply air curtain to replace the multi air inlet is put forward and the quantitative relation of relevant parameters of supply air curtain, atrium and fire is established. It is obtained that the effect of smoke exhausting is the best when the ratio of air inlet height of supply air curtain to atrium height is 0.66, the ratio of air inlet width to length is 0.01, the air inlet velocity is 2.8m/s, the fan open time is 60s, the atrium opening rate is 0.084, the shape factor is up to 3.06, the indoor temperature is lower and low to 10℃, the fire heat release rate is smaller and small to 1.5MW and the fire is located in the wall corner.