飛火顆粒點燃的實驗及機理研究
發(fā)布時間：2018-07-31 14:52
【摘要】：森林植被或建筑木質(zhì)結(jié)構(gòu)燃燒、亦或是高壓電線與樹木的相互作用會產(chǎn)生木質(zhì)飛火顆粒,還有煙花燃放(燃燒的微小顆粒)、電焊操作(高溫不燃燒的熱顆粒)、工業(yè)磨削或高壓電線碰撞等會產(chǎn)生高溫金屬顆粒,均可在外界火焰流場及環(huán)境風(fēng)作用下,運動到其源頭之外相對遠的區(qū)域,形成新的點火源,點燃森林可燃物、建筑屋頂?shù)冉ㄖ獠坎牧匣蚪ㄖ饬⒚姹夭牧系?導(dǎo)致新的火災(zāi)事故或加速跳躍式火勢蔓延。此類火災(zāi)現(xiàn)象稱為飛火。飛火是大尺度森林火災(zāi)及森林-城鎮(zhèn)交界域火災(zāi)中常見的火災(zāi)現(xiàn)象,飛火顆粒點燃森林可燃物或建筑結(jié)構(gòu)是導(dǎo)致森林大火及森林-城鎮(zhèn)交界域大火發(fā)生的重要潛在蔓延途徑。與大量研究的傳統(tǒng)火蔓延(直接明火接觸點燃和火焰輻射點燃)相比,飛火顆粒點燃森林可燃物或建筑結(jié)構(gòu)的點燃方式有很大不同,因此亟需研究飛火顆粒的點燃過程進而填補該研究領(lǐng)域的空白。本論文研究目的是認識高溫飛火顆粒點燃建筑外立面保溫材料和森林可燃物的基本點燃過程,并建立物理模型揭示其點燃現(xiàn)象及機理。本文的具體工作如下：采用非等溫?zé)嶂睾筒钍綊呙枇繜岱?研究低密度建筑外墻保溫材料的點燃及燃燒過程中的熱解動力學(xué)特性�；诠腆w材料的熱解失重曲線,采用等轉(zhuǎn)化率方法和模式函數(shù)法,研究了典型建筑保溫材料在空氣氣氛條件下的熱解動力學(xué)規(guī)律,并通過DSC曲線獲得了各個熱解失重階段的放熱量�；谏鲜鰺峤鈩恿W(xué)研究獲得的聚氨酯泡沫和聚苯乙烯泡沫氧化熱解階段的動力學(xué)參數(shù)及反應(yīng)放熱量,結(jié)合經(jīng)典熱點理論,分別以氧化鋁顆粒和金屬鎂顆粒為例,建立了高溫顆粒點燃聚氨酯泡沫和聚苯乙烯泡沫的臨界條件,模型初步預(yù)測了理想情況下熱顆粒對保溫材料的點燃規(guī)律。為深入研究熱顆粒的點燃行為,我們建立了熱顆粒點燃保溫材料的實驗平臺。實驗研究了惰性金屬熱顆粒(直徑6mm至14mm,溫度900℃至1100℃)點燃低密度聚苯乙烯泡沫(18或27kg/m3)的過程。實驗研究表明：熱顆粒對聚苯乙烯泡沫的點燃過程僅發(fā)生于顆粒在材料表面的滾動過程及顆粒在材料表面滾動停止且未完全進入燃料床的時間間隔內(nèi)。金屬熱顆粒對低密度聚苯乙烯泡沫的臨界點燃溫度與臨界顆粒尺寸呈現(xiàn)雙曲線關(guān)系,即顆粒直徑從6mm升高至14mm時,臨界點燃溫度將從1030℃降至935℃。與文獻中高密度森林可燃物對比發(fā)現(xiàn),聚苯乙烯泡沫的臨界點燃溫度較高,且點燃轉(zhuǎn)變區(qū)域較窄,導(dǎo)致熱顆粒點燃對顆粒尺寸呈現(xiàn)弱的依賴關(guān)系。實驗結(jié)果表明,燃料床的密度和厚度對點燃概率和質(zhì)量損失速率的影響較弱。理論分析表明,熱顆粒在聚苯乙烯泡沫的點燃過程中不僅充當加熱源的作用,而且充當先導(dǎo)點燃源的作用；熱顆粒對聚苯乙烯泡沫的點燃過程是材料熱解氣和周圍空氣的混合時間與顆粒在材料表面的滯止時間相互競爭作用的結(jié)果�；跓犷w粒點燃保溫材料的實驗現(xiàn)象,我們建立了描述熱顆粒點燃聚苯乙烯泡沫的氣相點燃數(shù)值模型,該模型耦合固相熱解反應(yīng)、氣相化學(xué)反應(yīng)及可燃熱解混合氣的自然對流作用。數(shù)值模型獲得了不點燃、不穩(wěn)定點燃及穩(wěn)定點燃三種點燃機制。數(shù)值模型可以較好地預(yù)測實驗獲得的熱顆粒點燃的臨界條件。鑒于建筑外立面保溫材料和森林可燃物的熱解、燃燒特性的差異,通過改造熱顆粒點燃的實驗平臺,進行標準化實驗操作,研究在環(huán)境風(fēng)(O～4m/s)作用下,惰性金屬熱顆粒(直徑6mm至14mm,溫度600℃至1100℃)對不同含水率的松針燃料床(6%至35%)的點燃過程。研究主要關(guān)注和討論熱顆粒直接明火點燃、陰燃點燃、陰燃向明火轉(zhuǎn)變的點燃過程。持續(xù)點燃的臨界顆粒溫度(Tp.crt=1800(1+4FMC)/d+500[℃]關(guān)系式)隨顆粒尺寸的降低和燃料床含水率的增加而減小,熱顆粒的最大加熱效率近似ηsp=10%。隨著熱顆粒尺寸的增加,燃料床含水率的影響會變?nèi)�。實驗測量了金屬熱顆粒對松針燃料床的兩種明火點燃時間。該時間隨顆粒尺寸和風(fēng)速的增加而減小,隨燃料床含水率的增加而增加。理論分析解釋了臨界點燃條件、點燃延滯時間以及直接點燃與陰燃之間的關(guān)系。理論分析也表明：在快速的熱顆粒直接明火點燃過程中,熱顆粒不僅充當加熱源的作用,而且充當先導(dǎo)點燃源的作用。而在陰燃點燃和陰燃向明火的轉(zhuǎn)變過程中,熱顆粒僅充當加熱源的作用,明火點燃的轉(zhuǎn)變過程是易燃混合氣體的自發(fā)點燃過程。
[Abstract]:The interaction of forest vegetation or building wood structure, or the interaction of high voltage wires and trees, can produce wood fire particles, and fireworks (small particles burning), electric welding (hot particles not burning at high temperature), industrial grinding or high pressure wire collisions, which produce high temperature metal particles, which can be used in the external flame flow field and environment. Under the action of the wind, a new fire source is formed, a new ignition source is formed, the forest combustibles are ignited, the exterior materials of building roofs or building exterior insulation materials, etc., lead to new fire accidents or accelerate the sprawl of jumping fire. This kind of fire is called flying fire. Fire is a large scale forest fire and forest town. Fire particles or building structures are an important potential spread way to cause forest fires and forest fires. Compared with the traditional fire spread (direct fire contact ignition and flame radiation point burning), flying fire particles ignite forest combustibles. The lighting process of building structure is very different. Therefore, it is urgent to study the ignition process of flying fire particles to fill the blank of the research field. The purpose of this paper is to understand the basic ignition process of high temperature fly fire particles to ignite the exterior insulating materials and forest combustibles, and to establish a physical model to reveal the ignition phenomena and mechanism. The specific work of this paper is as follows: using non isothermal thermogravimetry and differential scanning calorimetry, the pyrolysis dynamic characteristics of low density building external wall thermal insulation materials are studied. Based on the weight loss curve of solid material, the atmosphere atmosphere of typical building insulation materials is studied by using the equal conversion method and mode function method. The thermal kinetics of the pyrolysis was obtained by the DSC curve. The kinetic parameters and the reacting heat of the polyurethane foam and polystyrene foam were obtained by the kinetic study of the pyrolysis kinetics. For example, the critical conditions for high temperature particles to ignite polyurethane foam and polystyrene foam are established. The model has preliminarily predicted the ignition law of thermal particles under ideal conditions. In order to study the ignition behavior of hot particles, we set up an experimental platform for heat particles to ignite the thermal insulation materials. The process of ignition of low density polystyrene foam (18 or 27kg/m3) from 6mm to 14mm in diameter and temperature from 900 to 1100 C. Experimental study shows that the ignition of polystyrene foam by hot particles occurs only in the rolling process of the particles on the surface of the material and the stopping of the particles on the surface of the material and in the time interval of not completely entering the fuel bed. The critical ignition temperature of the low density polystyrene foam has a hyperbolic relationship with the critical particle size, that is, when the particle diameter increases from 6mm to 14mm, the critical ignition temperature will be reduced from 1030 to 935. The results show that the density and thickness of the fuel bed have a weak effect on the ignition probability and the mass loss rate. The theoretical analysis shows that the thermal particles not only act as the heating sources but also serve as the pilot igniting sources for the ignition of the polystyrene foam. The ignition process of hot particles on polystyrene foam is the result of the interaction between the mixing time of the material heat and the surrounding air and the lag time of the particles on the surface of the material. Based on the experimental phenomenon of the thermal particles igniting the thermal insulation material, a numerical model of gas phase ignition describing the hot particle point burning polystyrene foam is established. The model coupled the solid phase pyrolysis reaction, gas phase chemical reaction and the natural convection of combustible pyrolysis mixture. The numerical model obtained three kinds of ignition mechanisms, which are non igniting, unstable ignition and steady ignition. The pyrolysis of forest combustibles and the difference of combustion characteristics are carried out by standardized experimental operation by reforming the experimental platform of heat particle ignition. The ignition process of pine needle fuel beds (6% to 35%) with different moisture content of inert metal thermal particles (diameter 6mm to 14mm, temperature 600 to 1100 C) under the action of ambient wind (O to 4m/s) is studied. The direct ignition of hot particles, the igniting of the smoldering and the transition from the smoldering to the open fire. The critical particle temperature (Tp.crt=1800 (1+4FMC) /d+500[C) for continuous ignition decreases with the decrease of the particle size and the increase of the water content of the fuel bed, and the maximum heating efficiency of the hot particles is approximately sp=10%. with the increase of the thermal particle size. The effect of the water content of the fuel bed will become weaker. The time of two kinds of light igniting of the metal heat particles to the pine needle fuel bed is measured. This time decreases with the increase of particle size and wind speed, and increases with the increase of the water content of the fuel bed. The theoretical analysis also shows that heat particles not only act as the heating source, but also act as the pilot igniting sources in the process of quick hot particle direct fire, while the heat particles act only as the heating source during the transition of the smoldering and the smoldering to the open fire, and the transition process of the light ignition is a flammable mixed gas. The spontaneous ignition process.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：X932
本文編號：2155932
[Abstract]:The interaction of forest vegetation or building wood structure, or the interaction of high voltage wires and trees, can produce wood fire particles, and fireworks (small particles burning), electric welding (hot particles not burning at high temperature), industrial grinding or high pressure wire collisions, which produce high temperature metal particles, which can be used in the external flame flow field and environment. Under the action of the wind, a new fire source is formed, a new ignition source is formed, the forest combustibles are ignited, the exterior materials of building roofs or building exterior insulation materials, etc., lead to new fire accidents or accelerate the sprawl of jumping fire. This kind of fire is called flying fire. Fire is a large scale forest fire and forest town. Fire particles or building structures are an important potential spread way to cause forest fires and forest fires. Compared with the traditional fire spread (direct fire contact ignition and flame radiation point burning), flying fire particles ignite forest combustibles. The lighting process of building structure is very different. Therefore, it is urgent to study the ignition process of flying fire particles to fill the blank of the research field. The purpose of this paper is to understand the basic ignition process of high temperature fly fire particles to ignite the exterior insulating materials and forest combustibles, and to establish a physical model to reveal the ignition phenomena and mechanism. The specific work of this paper is as follows: using non isothermal thermogravimetry and differential scanning calorimetry, the pyrolysis dynamic characteristics of low density building external wall thermal insulation materials are studied. Based on the weight loss curve of solid material, the atmosphere atmosphere of typical building insulation materials is studied by using the equal conversion method and mode function method. The thermal kinetics of the pyrolysis was obtained by the DSC curve. The kinetic parameters and the reacting heat of the polyurethane foam and polystyrene foam were obtained by the kinetic study of the pyrolysis kinetics. For example, the critical conditions for high temperature particles to ignite polyurethane foam and polystyrene foam are established. The model has preliminarily predicted the ignition law of thermal particles under ideal conditions. In order to study the ignition behavior of hot particles, we set up an experimental platform for heat particles to ignite the thermal insulation materials. The process of ignition of low density polystyrene foam (18 or 27kg/m3) from 6mm to 14mm in diameter and temperature from 900 to 1100 C. Experimental study shows that the ignition of polystyrene foam by hot particles occurs only in the rolling process of the particles on the surface of the material and the stopping of the particles on the surface of the material and in the time interval of not completely entering the fuel bed. The critical ignition temperature of the low density polystyrene foam has a hyperbolic relationship with the critical particle size, that is, when the particle diameter increases from 6mm to 14mm, the critical ignition temperature will be reduced from 1030 to 935. The results show that the density and thickness of the fuel bed have a weak effect on the ignition probability and the mass loss rate. The theoretical analysis shows that the thermal particles not only act as the heating sources but also serve as the pilot igniting sources for the ignition of the polystyrene foam. The ignition process of hot particles on polystyrene foam is the result of the interaction between the mixing time of the material heat and the surrounding air and the lag time of the particles on the surface of the material. Based on the experimental phenomenon of the thermal particles igniting the thermal insulation material, a numerical model of gas phase ignition describing the hot particle point burning polystyrene foam is established. The model coupled the solid phase pyrolysis reaction, gas phase chemical reaction and the natural convection of combustible pyrolysis mixture. The numerical model obtained three kinds of ignition mechanisms, which are non igniting, unstable ignition and steady ignition. The pyrolysis of forest combustibles and the difference of combustion characteristics are carried out by standardized experimental operation by reforming the experimental platform of heat particle ignition. The ignition process of pine needle fuel beds (6% to 35%) with different moisture content of inert metal thermal particles (diameter 6mm to 14mm, temperature 600 to 1100 C) under the action of ambient wind (O to 4m/s) is studied. The direct ignition of hot particles, the igniting of the smoldering and the transition from the smoldering to the open fire. The critical particle temperature (Tp.crt=1800 (1+4FMC) /d+500[C) for continuous ignition decreases with the decrease of the particle size and the increase of the water content of the fuel bed, and the maximum heating efficiency of the hot particles is approximately sp=10%. with the increase of the thermal particle size. The effect of the water content of the fuel bed will become weaker. The time of two kinds of light igniting of the metal heat particles to the pine needle fuel bed is measured. This time decreases with the increase of particle size and wind speed, and increases with the increase of the water content of the fuel bed. The theoretical analysis also shows that heat particles not only act as the heating source, but also act as the pilot igniting sources in the process of quick hot particle direct fire, while the heat particles act only as the heating source during the transition of the smoldering and the smoldering to the open fire, and the transition process of the light ignition is a flammable mixed gas. The spontaneous ignition process.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：X932
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