Study On Fire Spread And Protection Of Cigarette Workshop Building

Along with the improvement of automation in industry, joint workshops are more and more widely used in tobacco industry. However, application of joint workshop brings new challenge to fire protection of building because of difficulties in fire compartmentation. Theoretical and experimental analysis are carried out to study characteristics of combustibles, smoke movement and control, evacuation, and fire-resistance of grid structure of steel of tobacco joint workshop in this dissertation. Achievements of this study are listed as the following:(1) Characteristics of tobacco combustibles are studied using cone-calorimeter. Maximum heat release rate of samples of tobacco combustible is 20-100 kW/m2 and average heat release rate is 10-50 kW/m. Increase rate of heat release rate of tobacco leaves and threads fire is between that of slow t-square fire and medium t-square fire, and increase rate of heat release rate of tobacco sticks is less than that of slow t-square fire, since there are great differences in form and texture between tobacco leaves, threads and sticks. The combustion efficiency of tobacco thread is high, while there is considerable dust in the smoke.(2) Mathmatic models for ceiling jet and wall jet with negative buoyancy are proposed. Numerical solutions for the models are provided for the models based on simplification. Variation of smoke depth, temperature and velocity along with the coordinates are obtained. Experimental results are used to compare with the predictions of mathematic models, good agreements are observed(3) Reduced-scale experiments are performed to study smoke filling in a model joint workshop with natural ventilation and mechanical exhaust. Profiles of temperature and smoke layer height are obtained. It is demonstrated from the experimental results that there is evident stratification of temperature in the model workshop under fire. However, smoke layer height varies with positions because of the effect of local flow such as ceiling jet and wall jet. Smoke layer heights near wall are lower than other position because of the wall jet with negative buoyancy, which results in affecting the evacuation at the exits. Based on the characterics of wall jet with negative buoyancy, two means are proposed to weaken the influence of wall jet.(4) 2 modes of evacuation (personnel-pace-control mode and exit-width-control mode) are proposed to describe the evacuation in building, criterion and calculation of evacuation time of 2 modes are also provided. Quantitive study on effect of fire on personnel movement, pre-action time and flow capacity of exit are performed. Case simulation with a factual workshop is carried out, which shows that the mode of evacuation in joint workshop is personnel-pace-control and there are barely jam at the exits.(5) According to the breakage criterion of steel structure, method and process for risk assessment of grid structure of steel under fire is proposed. Case study with a factual workshop roof is performed and it is showed that risk assessment of grid structure of steel under fire should combine conditions of fire, heat transfer with conditions of loading, geometrical restriction of the structure itself. Considering the heating condition of structure under fire merely is not enough to judge the reliability of structure.It is a systematic project of fire protection of tobacco joint workshop. A number of theoretical and engineering subjects are involved. Therefore, the study in this paper is helpful to fire protection design of tobacco joint workshop with the theoretical models and experimental data.