摘要
水成膜泡沫(AFFF)的发展和应用是消防泡沫的重大变革,水成膜泡沫内含有氟表面活性剂,具有很强的流动性和成膜性。在灭火过程中,灭火时间是消防员最关心的问题,它是验证系统灭火效能的唯一指标,也是决定消防损害管制成败的重要指标。影响AFFF灭火时间的最重要因素是泡沫的蔓延过程,泡沫蔓延速度快、覆盖面积广、抗烧能力强,则灭火时间短。冷态缓释放条件下,AFFF在方形浅油面上的蔓延模型研究可以定量分析泡沫蔓延距离与时间及其他影响因素的联系,对大面积油火消防设计有重要的理论指导意义。由于AFFF蔓延的过程中伴随泡沫沉降,所以假设泡沫在油面蔓延过程是准静态过程,在较短的时间范围内,不考虑泡沫沉降对泡沫流量的影响,泡沫蔓延的主要作用力是泡沫的静压力和泡沫、油面界面间的黏性阻力,忽略惯性力。通过假设建立连续方程和动量守恒方程,得到冷态缓释放条件下AFFF在圆形油面上蔓延距离和泡沫高度函数。研究发现,冷态下泡沫的蔓延距离与流量和时间呈指数关系,与泡沫燃油界面间的黏性阻力呈负指数关系。
The development of the Aqueous Film Forming Foam （AFFF） heralds a revolution in the study on fire fighting foams. Fluorosurfactants are added in the AFFF to facilitate the spread of a thin film of water on oil fire. In fighting against fire, time is a very important parameter, which decides whether the damage can be effectively controlled. The spreading process is closely related with the fire fighting time. If foams spread quickly, the cover area will be large and the burning resistant ability can be improved. Since there is a foam drainage, in the model it is assumed that the AFFF foam spreading process is in a quasi steady state and the drainage will not affect the flow within a short time. The main driving force is the hydrostatic pressure and the viscosity shear between the AFFF foam and the oil interface. The foam spreading distance and the foam height are obtained based on the continuity equation and the momentum equation. The calculation results based on the model show that with a larger AFFF flux and a longer time, we will obtain longer spreading distance. With given AFFF and oil, the viscosity shear between AFFF foam and oil interface is the main parameter. In the test, it is found that resistance of the channel can also affect the spreading distance, by which the distance can be reduced. The AFFF drainage will also reduce the spreading distance. In order to improve the model, the resistance of the channel and the AFFF drainage are to be considered. A good model for a cold AFFF foam spreading on the circular oil surface under a gentle application is necessary for the AFFF foam to be used on large area oil fire, to predict the fire fighting time.
出处
《科技导报》
CAS
CSCD
北大核心
2009年第21期95-98,共4页
Science & Technology Review
基金
海军武器装备研制项目
关键词
水成膜泡沫
黏性阻力
预测
aqueous film forming foam
viscosity shear
prediction
