Municipal Tobacco Distribution Warehouse Fire And Smoke Control Numerical Test

When the tobacco warehouse catch fire, it is not just an ordinary warehouse fire, but spreads in a short time and beyond control rapidly because of its highly inflammable storage, destroying a large number of tobacco products, machinery and equipment, causing huge economic losses. Studying the break out and development law of warehouse fire has a great significance to the elimination and control of fire hazard, and the protection of personnel and property. This thesis takes a cigarette distribution warehouse as the research subject, carries out numerical tests on the fire and smoke flow and control by use of FDS fire simulation software.Firstly, we choose a typical finished cigarette in warehouse as a sample for the thermogravimetric analysis. Through the pyrolysis experiment measured the ignition temperature, combustion characteristic index and activation energy value of tobacco, provided the basis for parameter settings of the numerical test.Secondly, set up the physical model according to the actual warehouse size, using FDS large eddy simulation method respectively simulated the fire situation under no smoke extraction measures, natural draught system and mechanical smoke extraction system, obtained the smoke diffusion law and temperature distribution under the three condition, compared the effect of natural draught system and mechanical smoke extraction system. Results show that under natural draught system, the fire develops rapidly, the temperature, concentration of CO and visibility quickly reach people’s risk tolerance limits, the evacuation time is only326s. Although the mechanical smoke extraction system improves the visibility and reduces the CO content, it will aggravate the fire because of large quantity of fresh air brought by the mechanical negative pressure. According to the height of smoke layer and fire intensity calculation method in NFPA92B, set the smoke layer at the height of4.5m, compared with the specification for design of high-rise building fire, volume ventilation design method is more reasonable.Finally, in accordance with the principle of mathematical statistics, permuted the four factors of the position, number, wind velocity and smoke level of the exhaust vent, simulated the fire condition with FDS, discussed their impact on the exhaust effect. The results show that ceiling smoke extraction is superior to the side wall smoke extraction, increasing the number of smoke vent improves the extraction effect in the case of a certain amount of smoke. Increasing the smoke amount helps the exhaust of smoke, but aggravates the fire at the same time. The oversized speed of exhaust vent will lead to smoke plugholing phenomenon, thus reduce exhaust efficiency. The setting of the exhaust speed should be based on the specific parameters of the building to achieve the desired smoke exhaust effect.