Small Size Experiment And Dynamic Simulation Of Fire Characteristics In Confined Space

With the rapid development of the global economy, the fire occurred more and more frequently. The fire situation is increasingly grim. Fire brings threat to human life, leads to the loss of economic property and the destruction of the ecological environment. It is a common problem faced by the people all over the world. Study of fire is a long-term process. Based on the theory, scientific and technological progress, it’s very necessary to fully understand the basic phenomena and harm of full understanding of fire, study the development of fire process more comprehensive and deeply under limited conditions.Based on fire dynamics, a small size fire wind tunnel experimental platform was designed and set up by the author to study the effect of different wind speeds on different scale fires. Butane Bunsen and diesel oil pool were used to achieve different scale fires. Combined with modern scientific measurement technology, a series of experiments were conducted. The results showed that the temperature of the oil pool fire was about 30 oC to 200 oC higher than the Bunsen. The temperature distribution of the two kinds of fire was the same. The temperature above the fire source is the highest. The nearer to the fire source, the higher the temperature was. At the same measuring point, the larger the wind speed, the lower the temperature was. The farther to the fire, the higher temperature of the cross section was. For small scale fire, when v=0, flame shaked up and down without deviation, the width is constant. With the increase of the wind speed, flame height and flame area reduced, while flame lateral offset length increased. When the wind speed increased to a certain value, flame jittered like horizontal wavy. For large scale flame, with increase of the wind speed, flame height decreased first and then increased; flame area reduced; flame lateral offset length maximum increased first and then decreased. Vortex appeared in the flame. When the wind speed was large enough, the flame appeared the phenomenon of crack.According to the wind tunnel experiment platform, a strip-shaped confined space fire model was established by the fire dynamics simulation software Pyrosim. The simulation results were verified by the experimental results. Study further on temperature and smoke spread rules. The results showed that the simulation results were in good agreement with the experimental results. When the wind speed is 0, the temperature and the smoke were all centered on the fire source and distributed symmetrically. The temperature above the fire was the highest. The high temperature region and the smoke were mainly concentrated on the top of the wind tunnel. With the increase of wind speed, there was no smoke before the fire source and its temperature kept constantly. Smoke region and the high temperature region offset rearward. The maximum temperature and the area of the high temperature region of the transverse section of the fire source decreased. The offset angle increased.Pyrosim was also used to simulate the fire of large space dormitory. Two different fire conditions were set, including opening all windows and doors, closing fire room windows and opened the door after 20 s.The model was imported into the personnel evacuation software Pathfinder to reconstruct the personnel evacuation scenes. Results showed that the fire room temperature was the highest in the whole building. The fire floor temperature was higher than other floors. The closer to the fire source, the lower the visibility was. The heat flow rate of the fire room window was higher than that of the door. There had been no correlation between fire development and the two conditions mentioned above during the first 20 s since the fire broke out. After that, in the condition of doors and windows opened, the fire room temperature and heat flow rate was much lower; the smoke layer height was much higher. During the whole process, the upper stories of the fire room were seriously influenced by the smoke when the windows and doors of the fire room were opened. In contracts, the corridors and stairs were more seriously influenced by the smoke when the fire room window was closed and opened the door after 20 s. The best time to escape was 164.8s. In order not to affect the personnel safety evacuation, the width of exit door should be no less than 3 m and stair should be no less than 1.75 m.