单液滴撞击受热炭化可燃固体表面的动态过程研究
发布时间：2018-12-06 18:11
【摘要】：气候异常、温室效应、雾霾等已成为当下中国乃至全球日益严峻的环境问题。而传统的哈龙灭火剂对臭氧层的破坏严重,细水雾作为哈龙灭火剂的良好替代品具有对环境友好、灭火高效、迅速、稳定等特点而受到广泛的关注。 当今火灾研究工作者已认识到研究细水雾机理和提高细水雾灭火效率对社会安全至关重要。而对液滴与高温可燃固体的相互作用过程的研究有助于从微观上认识细水雾的灭火机理。 首先,本文进行了小尺度的模拟实验,采用高速摄影对水滴、含4%AFFF的液滴与不同温度的纸张和木材表面碰撞后的形态变化进行了研究。研究结果表明：纸张的加热炭化对水滴撞击纸张表面的动态过程具有重要影响,水滴在粗糙度较大的受热炭化档案纸表面发生核沸腾并产生蒸发气泡,水滴碰撞纸张表面后产生飞溅的临界Weber数也受到了纸张加热炭化后表面特性变化的影响。 比较纯水滴与含4%AFFF液滴与常温和加热炭化枫桦木表面的相互作用过程。水滴撞击受热炭化枫桦木表面4ms后迅速飞溅生成次生液滴,小液滴滚动蒸发聚合成一个高液柱,起伏多次后形成一个小液柱停留于枫桦木表面,且其最大铺展因子较常温木材表面大；含4%AFFF表面活性剂液滴撞击受热枫桦木炭化表面时,液滴碰撞后与木材发生良好浸润现象。这从微观上解释了含4%AFFF添加剂的细水雾在到达高温可燃固体表面后能更有效地与固体表面发生浸润。 为进一步研究液滴与不同温度可燃固体表面作用的微观动态过程,探究固体表面特性对整个动态过程的影响。文章选取三种常用的木材柠檬桉、杉木和松木,并使木材表面从26℃均匀加热到240℃。实验得到：随着木材表面温度升高,其表面粗糙度也相应增大。水滴与不同温度木材表面碰撞动态过程显示：当温度为26℃-120℃时,水滴在粗糙度相对较高的柠檬桉表面并无气泡和飞溅现象产生,当温度达到173℃时,液滴在2ms时发生飞溅,在35ms时形成水晶式小气泡,随着温度的升高,气泡逐渐增大,而当温度升高到220℃时木材表面生成大量蒸气。在粗糙度更高的松木表面,水滴在75℃就开始出现飞溅现象,同时,在松木表面液滴有较大的液柱生成,随着松木表面温度的升高,水滴形成的反弹液柱高度先升高后降低。此外,水滴在240℃松木表面也发生明显增发气泡现象。而在粗糙度最小的杉木表面,液柱也随着温度的升高而先增大后减小,然而在所有的杉木温度工况下,水滴均未发生飞溅和产生蒸发气泡现象。
[Abstract]:The climate anomaly, the greenhouse effect, the haze and so on have become increasingly serious environmental problems in China and even the world. and the traditional halon fire-extinguishing agent has serious damage to the ozone layer, and the fine water fog as a good substitute for the halon fire-extinguishing agent has the characteristics of environment-friendly, high-efficiency, rapid and stable fire-extinguishing, and the like. In today's fire research workers, it has been recognized that the study of the mechanism of fine water mist and the improvement of the efficiency of water mist fire-extinguishing to the safety of society to the close The study of the interaction between the liquid drop and the high-temperature combustible solid can help to realize the de-excitation of the fine water mist from the microscopic level. In this paper, a small-scale simulation experiment is carried out, and the morphological changes of water droplets and 4% AFFF on the surface of paper and wood with different temperatures are carried out by high-speed photography. The results show that the heating and carbonization of paper has an important influence on the dynamic process of water drop impact on the surface of paper. The critical Weber number after the air bubble and water droplets collide with the paper surface is also affected by the change of the surface property after the paper heating and carbonization. The effect of pure water droplets on the surface of the birch wood with 4% AFFF and the normal temperature and the heating of the carbonized maple in that proces of mutual action, after the water drops hit the surface of the birch wood of the heated carbonized maple, the surface of the birch wood is rapidly splashed to generate secondary liquid drops, the small liquid drops are roll and evaporated and polymerized into a high-liquid column, and after the fluctuation, a small liquid column is formed to stay on the surface of the maple birch, and the maximum spreading factor thereof is higher than that of the normal temperature. The wood surface is large; when the droplets of the surface active agent containing 4% of the AFFF are impacted and heated to the surface of the carbonized birch wood, the liquid drops collide with the wood after the liquid drops collide. Good wetting. This is a microscopic explanation of the fact that the fine mist containing 4% of the AFFF additive can be more effective in contact with the solid form after reaching the surface of the high temperature combustible solid In order to further study the micro-dynamic process of the surface action of the liquid droplets with different temperature, the surface properties of the solid were investigated. The effects of three kinds of common wood, Lemon, Chinese fir and pine wood, were selected, and the surface of wood was made uniform from 26 鈩，
本文编号：2366444
[Abstract]:The climate anomaly, the greenhouse effect, the haze and so on have become increasingly serious environmental problems in China and even the world. and the traditional halon fire-extinguishing agent has serious damage to the ozone layer, and the fine water fog as a good substitute for the halon fire-extinguishing agent has the characteristics of environment-friendly, high-efficiency, rapid and stable fire-extinguishing, and the like. In today's fire research workers, it has been recognized that the study of the mechanism of fine water mist and the improvement of the efficiency of water mist fire-extinguishing to the safety of society to the close The study of the interaction between the liquid drop and the high-temperature combustible solid can help to realize the de-excitation of the fine water mist from the microscopic level. In this paper, a small-scale simulation experiment is carried out, and the morphological changes of water droplets and 4% AFFF on the surface of paper and wood with different temperatures are carried out by high-speed photography. The results show that the heating and carbonization of paper has an important influence on the dynamic process of water drop impact on the surface of paper. The critical Weber number after the air bubble and water droplets collide with the paper surface is also affected by the change of the surface property after the paper heating and carbonization. The effect of pure water droplets on the surface of the birch wood with 4% AFFF and the normal temperature and the heating of the carbonized maple in that proces of mutual action, after the water drops hit the surface of the birch wood of the heated carbonized maple, the surface of the birch wood is rapidly splashed to generate secondary liquid drops, the small liquid drops are roll and evaporated and polymerized into a high-liquid column, and after the fluctuation, a small liquid column is formed to stay on the surface of the maple birch, and the maximum spreading factor thereof is higher than that of the normal temperature. The wood surface is large; when the droplets of the surface active agent containing 4% of the AFFF are impacted and heated to the surface of the carbonized birch wood, the liquid drops collide with the wood after the liquid drops collide. Good wetting. This is a microscopic explanation of the fact that the fine mist containing 4% of the AFFF additive can be more effective in contact with the solid form after reaching the surface of the high temperature combustible solid In order to further study the micro-dynamic process of the surface action of the liquid droplets with different temperature, the surface properties of the solid were investigated. The effects of three kinds of common wood, Lemon, Chinese fir and pine wood, were selected, and the surface of wood was made uniform from 26 鈩，
本文编号：2366444
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