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Experimental and Theoretical Study on Flow Behavior from a Fire Source under the downward Flow

向下流下火源流动行为的实验与理论研究

基本信息

批准号：
62550426
负责人：
SUGAWA Osami
金额：
$ 1.09万
依托单位：
Tokyo University of Science
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1989
项目状态：
已结题

项目摘要

An interaction between fire induced upward flow and downward ventilation flow in a clean room is a matter of some concerns in the fire safety and smoke detection. Generally, the buoyant plume from an early stage of fire is very weak and is easily diluted with ambient air flow of the ventilation before the fire products reaching to a fire detector. In order to ensure adequate fire safety for clean rooms, it is important to design the early fire detecting system depending on the flow behavior produced by the complex of upward fire flow and downward ventilation flow.Full scale model clean rooms, 6.4m(W) x 9m(L) x 3.2m(H) and 3.8m (W) x 3.8m(L) x 3.0m(H), were used with a line or a circular model fire source of 6kW. Methylalcohol was used as a fuel. Temperature, velocity, and dynamic pressure were measured every 10 sec and flow visualization by a smoke wire and/or smoke candles was also carried out simultaneously. Downward ventilation velocity ranging 20 cm/sec - 45 cm/sec was employed.Cen … More ter-line upward velocity in a characteristic form of v/Q^<1/5> and temperature rise (DELTAT) in a plume above a fire source were plotted against characteristic height with heat release rate of z/Q^<2/5>. These experimental data were obtained with downward ventilation flow. v/Q^<1/5> = A (z/Q^<2/5>)^n, DELTAT = B (z/Q^<2/5>)^<2n-1>. The values of A and B for the plume region with downward ventilation flow of 24 - 25 cm/sec are estimated as A = 0.2 - 0.3 and B = 3 - 5, respectively with n = -1/3. It was clearly found that the flow behavior based on temperature rise and velocity along the center-line of the fire plume are similar to those in the fire plume without downward ventilation flow except the flame intermittent region. The decreasing rates of A and B are greater than those in the flow without ventilation flow. Complex flow induced by upward flow of fire plume and downward ventilation flow made rapid diffusion of fire products (smoke and gas) within ;the clean room in a few minutes. There is no enough time to protect the cleanliness of the clean room from smoke diffusion from a fire unless very rapid fire detecting system will presents. Less

洁净室内火灾引起的上升气流与下降气流的相互作用是火灾安全和烟雾探测中的一个重要问题。通常，来自火灾早期阶段的浮力羽流非常弱，并且在火灾产物到达火灾探测器之前很容易被通风的环境空气流稀释。为了保证洁净室足够的消防安全性，根据向上的火灾流和向下的通风流的复合体产生的流动行为来设计早期火灾探测系统是重要的。全尺寸模型洁净室，6.4m（W）x 9 m（L）x 3.2m（H）和3.8m（W）x 3.8m（L）x 3.0m（H），与6 kW的线或圆形模型火源一起使用。甲醇被用作燃料。每10秒测量一次温度、速度和动态压力，同时还通过发烟丝和/或发烟蜡烛进行流动可视化。采用20 cm/sec - 45 cm/sec的向下通气速度。 ...更多信息用特征曲线v/Q^<1/5>表示三线上升速度，用热释放率z/Q^<2/5>表示火源上方羽流中的温升（Δ T）。这些实验数据是用向下通风气流获得的。v/Q^<1/5> = A（z/Q^<2/5>）^n，Δ T = B（z/Q^<2/5>）^<2n-1>。在n = -1/3的情况下，向下通风速度为24 ~ 25 cm/s的羽流区的A和B值分别估计为A = 0.2 ~ 0.3和B = 3 ~ 5。结果表明，除火焰间歇区外，沿火羽流中心线沿着方向的温升和速度与无向下通风时的相似。A和B的下降速率大于无通风流动时的下降速率。火灾羽流向上流动和通风气流向下流动形成的复杂流动使得洁净室内的火灾产物（烟气）在几分钟内迅速扩散。没有足够的时间来保护洁净室免受火灾烟雾扩散的影响，除非有非常快速的火灾探测系统。少