可攜式含添加劑細水霧滅火系統對池火滅火性能評估研究

Abstract

本文基於可攜式含添加劑細水霧滅火系統的噴灑方法對池火的滅火性能及其相對應滅火機制的影響進行一系列的研究。不同的油料種類、噴頭噴灑角度、添加劑溶液的體積濃度、油量及油盆截面積為主要實驗參數。使用油料分別為庚烷、汽油、柴油；噴頭噴灑角度分別為與水平夾角30度、45度、60度；添加劑溶液的體積濃度分別為0%、3%、6%、10%。油量分別為250、500與1000毫升；油盆直徑分別為25與50公分。高噴灑角度時的主要滅火機制為火焰冷卻和氧氣置換；低噴灑角度時為油氣的阻隔與稀釋。本實驗使用的可攜式細水霧滅火系統擁有良好的熱輻射稀釋與降溫能力，對使用者能供良好的保護。細水霧加入添加劑後可使滅火性能極明顯提升，但過多的添加劑反而會造成滅火性能下降。在固定油盆大小的情況下，不同油量的滅火趨勢基本上是相似的。雖然因水霧噴灑造成的不均勻油料表面會稍微減低其燃燒率，這種不均勻的情況在油料厚度到達1公分以上即可改善。固定油料厚度的測試中，油盆直徑50公分的結果異於25公分的，因其較差的水霧覆蓋、較弱的水霧反彈與較多的水霧進入所致。滅火效率不僅受到水霧效應影響,亦同時受添加劑效應影響。因此對滅火效能而言，必然存在某個細水霧與添加劑間最理想的混合比率。

A series of tests subjected to various discharge methodologies and fire scenarios are carried out based on a portable water mist fire extinguishing system with additive on pool fires. Different fuel types, nozzle discharge angles, additive solution volumes, amount of fuels and cross-section area of pans are selected as the major experimental parameters. The fuels used are heptane, gasoline, and diesel, the nozzle discharge angles are 30°, 45°, and 60° with respect to the horizon, and the additive solution volumes are 0%, 3%, 6% and 10%. The amounts of fuel used are 250ml, 500ml and 1000ml, and the diameters of pan are 25cm and 50cm. The dominant mechanisms of restraining fire in the higher nozzle discharge angle regime (>45□) are flame cooling and oxygen-displacement, and in the lower one (<45□) are fuel vapors blocking and dilution. The portable water mist fire extinguishing system used has a good ability for radiation attenuation and temperature reduction that can provide a good protection for the operators. By using water mist with additive, the fire extinguishing efficiencies are significantly improved. However, if too much additive is provided, the fire extinguishment efficiency will decrease. The tendencies of the fire extinction times for different amount of fuel in a size-fixed pan are similar. Although the situation of non-uniform fuel surface resulted from water mist impingement slightly reduces the burning rate, it can be ameliorated as the height of liquid fuel attains at 1cm. In the tests with fixed fuel height, the results of 50cm diameter pan different to the ones of 25cm diameter since the interactions of its poorer mist coverage, weaker mist jet rebound and more mist reaching. The fire extinguishing efficiency is not only influenced by mist effects but also by additive ones. Therefore, there must be an optimal mixing ration between the mist and additive for fire suppression.