單液滴撞擊受熱炭化可燃固體表面的動(dòng)態(tài)過(guò)程研究
發(fā)布時(shí)間：2018-12-06 18:11
【摘要】：氣候異常、溫室效應(yīng)、霧霾等已成為當(dāng)下中國(guó)乃至全球日益嚴(yán)峻的環(huán)境問(wèn)題。而傳統(tǒng)的哈龍滅火劑對(duì)臭氧層的破壞嚴(yán)重,細(xì)水霧作為哈龍滅火劑的良好替代品具有對(duì)環(huán)境友好、滅火高效、迅速、穩(wěn)定等特點(diǎn)而受到廣泛的關(guān)注。 當(dāng)今火災(zāi)研究工作者已認(rèn)識(shí)到研究細(xì)水霧機(jī)理和提高細(xì)水霧滅火效率對(duì)社會(huì)安全至關(guān)重要。而對(duì)液滴與高溫可燃固體的相互作用過(guò)程的研究有助于從微觀上認(rèn)識(shí)細(xì)水霧的滅火機(jī)理。 首先,本文進(jìn)行了小尺度的模擬實(shí)驗(yàn),采用高速攝影對(duì)水滴、含4%AFFF的液滴與不同溫度的紙張和木材表面碰撞后的形態(tài)變化進(jìn)行了研究。研究結(jié)果表明：紙張的加熱炭化對(duì)水滴撞擊紙張表面的動(dòng)態(tài)過(guò)程具有重要影響,水滴在粗糙度較大的受熱炭化檔案紙表面發(fā)生核沸騰并產(chǎn)生蒸發(fā)氣泡,水滴碰撞紙張表面后產(chǎn)生飛濺的臨界Weber數(shù)也受到了紙張加熱炭化后表面特性變化的影響。 比較純水滴與含4%AFFF液滴與常溫和加熱炭化楓樺木表面的相互作用過(guò)程。水滴撞擊受熱炭化楓樺木表面4ms后迅速飛濺生成次生液滴,小液滴滾動(dòng)蒸發(fā)聚合成一個(gè)高液柱,起伏多次后形成一個(gè)小液柱停留于楓樺木表面,且其最大鋪展因子較常溫木材表面大；含4%AFFF表面活性劑液滴撞擊受熱楓樺木炭化表面時(shí),液滴碰撞后與木材發(fā)生良好浸潤(rùn)現(xiàn)象。這從微觀上解釋了含4%AFFF添加劑的細(xì)水霧在到達(dá)高溫可燃固體表面后能更有效地與固體表面發(fā)生浸潤(rùn)。 為進(jìn)一步研究液滴與不同溫度可燃固體表面作用的微觀動(dòng)態(tài)過(guò)程,探究固體表面特性對(duì)整個(gè)動(dòng)態(tài)過(guò)程的影響。文章選取三種常用的木材檸檬桉、杉木和松木,并使木材表面從26℃均勻加熱到240℃。實(shí)驗(yàn)得到：隨著木材表面溫度升高,其表面粗糙度也相應(yīng)增大。水滴與不同溫度木材表面碰撞動(dòng)態(tài)過(guò)程顯示：當(dāng)溫度為26℃-120℃時(shí),水滴在粗糙度相對(duì)較高的檸檬桉表面并無(wú)氣泡和飛濺現(xiàn)象產(chǎn)生,當(dāng)溫度達(dá)到173℃時(shí),液滴在2ms時(shí)發(fā)生飛濺,在35ms時(shí)形成水晶式小氣泡,隨著溫度的升高,氣泡逐漸增大,而當(dāng)溫度升高到220℃時(shí)木材表面生成大量蒸氣。在粗糙度更高的松木表面,水滴在75℃就開(kāi)始出現(xiàn)飛濺現(xiàn)象,同時(shí),在松木表面液滴有較大的液柱生成,隨著松木表面溫度的升高,水滴形成的反彈液柱高度先升高后降低。此外,水滴在240℃松木表面也發(fā)生明顯增發(fā)氣泡現(xiàn)象。而在粗糙度最小的杉木表面,液柱也隨著溫度的升高而先增大后減小,然而在所有的杉木溫度工況下,水滴均未發(fā)生飛濺和產(chǎn)生蒸發(fā)氣泡現(xiàn)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，
本文編號(hào)：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，
本文編號(hào)：2366444
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