水滴撞击高温酥油表面的动力学过程模拟试验研究  

Simulated research into the dynamic process of water-drop impact on the hot ghee surface

作　　者：陈萍萍[1] 王喜世[1] 张毅[1] 

机构地区：[1]中国科学技术大学火灾科学国家重点试验室,合肥230027

出　　处：《安全与环境学报》2011年第6期213-218,共6页Journal of Safety and Environment

基　　金：国家自然科学基金项目(50774072);国家重大基础研究计划(973计划)项目(2012CB719704);中央高校基本科研业务费专项资金青年创新基金项目(WK2320000002)

摘　　要：细水雾与酥油池火相互作用的初始阶段,或细水雾不能有效抑制酥油池火时,往往会发生火焰燃烧被强化的现象。为了深入认识这一现象的发生机理,通过模拟试验研究水滴撞击到不同温度酥油表面的动力学过程。试验中水滴的初始直径为(2.61±0.1)mm,韦伯数为77.9;酥油温度变化范围为200～300℃。整个碰撞过程采用Photron Fastcam高速摄影仪进行拍摄记录。结果表明:水滴撞击到高温酥油油池时,水滴会迅速蒸发并在酥油中生成气泡,气泡上升到酥油-空气交界面时破裂,或者在油池内部发生蒸汽爆炸导致酥油液滴或酥油液柱飞溅;当酥油温度达到300℃时,水滴进入酥油后114 ms左右即发生剧烈的蒸汽爆炸,大量高温酥油被溅起,这应该是导致细水雾熄灭酥油池火时发生火焰燃烧被强化的主要原因之一。The paper is aimed to present our experimental research results of the flame combustion enhancement due to the cumulative impacts of the water drop onto the ghee surface. In order to enhance our understanding of the mechanism of such phenomena, we have laid out a dynamical process of water-drop impacting onto the hot molten-ghee surface with the initial diameter of the drop of （2.61±0.1） mm and its impact Weber number being about 77.9. Then let the temperature of the molten-ghee vary from 200 ℃to 300 ℃ and the whole process of the impaction recorded by using a high speed Photron Fastcam camera at 500 frames each second. When the water droplets impact the hot molten-ghee pool, it would get fragmented, and eventully lead to a vapor explosion. The experimental results of ours show that as the water drops impact on the hot molten-ghee, they would evaporate soon and produce bubbles inside the molten-ghee. And, afterwards, the little bubbles would break while rising at the ghee-air interface, or produce vapor explosion inside the molten-ghee and finally result in ghee droplet/jet splashing. From our experimental results, it can be concluded that if the temperature of the oil pool is kept below a certain degree, no vapor explosions would occur, for example, to keep the ghee oil below 200 ℃. At this temperature, water droplets would sank into and even stay at the bottom of the container, no matter how long the water droplets in the inside of the oil, there will be no possibility for the vapor explosion to tke place. However, if the temperature of the molten-ghee reaches 300 ℃, it it certain that the smart vapor explosion would take place 114 ms after the water droplets drop into molten-ghee, with a lot of molten-ghee splashed. Such phenomena would be found insistent with Avedisian CT reported that the measured superheat oil temperature range of water was 279-302 ℃, which can be said one of the chief reasons for the combustion enhancement when ghee fire being suppressed with water mist.

关 键 词：安全工程 油池火 古建筑火灾 灭火 抑爆 细水雾 

分 类 号：TH322[机械工程—机械制造及自动化]