本文關(guān)鍵詞：典型非碳化聚合物材料熱解及逆流火蔓延實驗和理論研究　出處：《中國科學(xué)技術(shù)大學(xué)》2014年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 非碳化聚合物材料 熱解 火蔓延 有限尺寸 環(huán)境壓力影響

【摘要】：固體可燃物熱解及火蔓延是火災(zāi)初始和發(fā)展階段的重要分過程,決定著后續(xù)火災(zāi)的發(fā)展,因此一直是國內(nèi)外眾多學(xué)者重點研究的對象。熱解又是火蔓延的子過程,兩者有著密切的關(guān)系。非碳化聚合物材料作為現(xiàn)代建筑中廣泛應(yīng)用的裝飾材料,其在火災(zāi)中表現(xiàn)出的諸多特殊蔓延行為越來越多地受到研究者的關(guān)注。在外部熱流作用下,非碳化聚合物材料受熱后發(fā)生熱解反應(yīng),熱解產(chǎn)生的可燃?xì)馔ㄟ^形成氣泡等方式從材料內(nèi)部傳輸?shù)讲牧媳砻孢M(jìn)而析出到外界空氣中。熱解釋放出可燃性氣體與空氣混合形成可燃預(yù)混氣,經(jīng)點燃后會在材料表面發(fā)生燃燒化學(xué)反應(yīng)形成火焰。燃燒產(chǎn)生的熱量一部分用來加熱燃燒產(chǎn)物,一部分通過輻射散失到環(huán)境中,剩下的一部分則通過對流、輻射和熱傳導(dǎo)的方式反饋回材料表面形成反饋熱流而對未燃材料進(jìn)行預(yù)加熱,當(dāng)未燃材料被加熱后發(fā)生熱解又進(jìn)一步釋放出熱解可燃?xì)庖跃S持氣相燃燒,如此不斷的循環(huán)進(jìn)而形成材料表面持續(xù)的火蔓延過程。與傳統(tǒng)的碳化材料(如紙張、木材等)不同,非碳化材料在熱解的過程中基本沒有碳層形成,不會阻礙外部熱流對材料的預(yù)加熱,因此其熱解速率要遠(yuǎn)大于碳化材料的熱解。此外,材料的熔融和流動特性也會增加材料的蔓延速率。 本文首先在錐型量熱儀氮氣氣氛下對PMMA (Poly(methyl methacrylate))、 ABS(Poly(acrylonitrile butadiene styrene))和HIPS(High Impact Polystyren)三種典型非碳化聚合物材料進(jìn)行了不同熱流下的熱解實驗研究,在此基礎(chǔ)上對非碳化聚合物材料有限尺寸自然條件下逆流火蔓延過程進(jìn)行了實驗和理論研究,其中包括材料厚度、寬度、環(huán)境壓力和三維效應(yīng)等參數(shù)對逆流火蔓延過程的影響。具體內(nèi)容概括如下： 熱解方面,在低、中、高三種熱流下對PMMA、ABS和HIPS的一維熱解過程進(jìn)行了實驗研究。通過對比熱電偶和紅外熱像儀材料背面溫度的測量結(jié)果,驗證了非接觸測溫方法的可行性。利用實驗所測得的材料背面溫度和質(zhì)量損失速率,并結(jié)合Stanislav I. Stoliarov的ThermoKin模型得到材料的導(dǎo)熱系數(shù)與溫度的分段線性關(guān)系。進(jìn)而在實驗的基礎(chǔ)上建立了一個考慮材料表面熱流吸收方式和熱解化學(xué)反應(yīng)的非碳化聚合物材料的一維熱解模型,模型對文獻(xiàn)中廣泛采用的深度吸收和表面吸收這兩種假設(shè)分別進(jìn)行了研究和對比,結(jié)果表明不同吸收方式對材料表面溫度和熱穿透層內(nèi)溫度分布有較大影響,這種不同在空氣氣氛下體現(xiàn)在著火時間的明顯差異。而在宏觀熱解方面,即不考慮材料內(nèi)部熱解細(xì)節(jié)的情況下,兩者的模擬結(jié)果均在可接受的范圍之內(nèi)。通過對比失重速率和背面溫度的實驗和模擬結(jié)果驗證了此一維熱解模型的正確性。 火蔓延方面,在熱解研究的基礎(chǔ)上對自然對流和不同環(huán)境壓力下的逆流火蔓延過程進(jìn)行了實驗和理論分析。結(jié)果表明在材料寬度較小的情況下,逆流火蔓延速率隨厚度的增大而增加,這與二維無限寬條件下的結(jié)論有較大差別。主要原因是有限尺寸條件下,材料兩側(cè)的燃燒過程加速了蔓延速率。在厚度固定情況下,火蔓延速率反比于材料寬度。在合肥、西寧和拉薩不同環(huán)境壓力條件下,失重速率、火焰高度和火蔓延速率均隨壓力的增大而增大。在低壓條件下,氣相化學(xué)反應(yīng)動力學(xué)和火焰反饋熱流是影響火蔓延速率的主要因素,當(dāng)表征氣相化學(xué)反應(yīng)的Damkohler數(shù)小于一個臨界值會產(chǎn)生熄火現(xiàn)象。本文還從傳熱和傳質(zhì)角度出發(fā)對火蔓延過程進(jìn)行了理論分析并得到簡化模型,模型中材料的火蔓延速率是材料尺寸、火焰前沿角度和材料熱物理參數(shù)的函數(shù)。另外此模型還提供了通過測量火蔓延速率估算熱解區(qū)和預(yù)熱區(qū)火焰反饋熱流大小的方法。同樣,模型與實驗結(jié)果較好的一致性說明了簡化模型的正確性。
[Abstract]:Solid combustible pyrolysis and fire spread is an important branch of fire and initial stage of development, determines the development of subsequent fire, so it has been the focus of the study of many scholars at home and abroad. The pyrolysis is the fire spreading process, the relationship between them. The non carbide polymer material is widely used in modern architecture the decoration materials, which exhibit in the fire spread many special behavior more and more attention of researchers. In the external heat flux under non carbide were pyrolyzed polymer material after heating, the pyrolysis of combustible gas through the formation of bubbles from inside the material transfer to the material surface and precipitation to the outside air. Thermal release of flammable gas pre mixed with air to form combustible mixed gas, the formation of flame combustion chemical reaction on the surface of the material will ignite after combustion heat. A part is used to heat the combustion products, part of a loss to the environment by radiation, the remaining part is by convection, radiation and conduction of the way back to the surface of materials and heat feedback to pre heat the unburned material, when unburned after pyrolysis and pyrolysis gas can be further released to maintain gas phase combustion the material is heated, this constant cycle and the formation of continuous material surface fire spread process. With the traditional carbon materials (such as paper, wood, etc.), non carbide materials in the pyrolysis process of no carbon layer is formed, will not hinder the external heat flux of pre heating of the material, so it should be far greater than the pyrolysis rate of pyrolysis carbide materials. In addition, the melt flow characteristics of materials and materials will also increase the rate of spread.
Firstly, in the cone calorimeter under nitrogen atmosphere of PMMA (Poly (methyl methacrylate) (Poly), ABS (acrylonitrile butadiene styrene)) and HIPS (High Impact Polystyren) three kinds of non carbonized polymer materials were studied under different thermal pyrolysis experiments, on the basis of non carbonized polymer material Co. the size of the fire spread process under natural conditions countercurrent experiments and theoretical research, which includes material thickness, width, ambient pressure and three-dimensional effects of parameters such as the spread of countercurrent fire. The specific contents are summarized as follows:
The pyrolysis, in low, high heat flux of PMMA, ABS and HIPS in the process of one-dimensional pyrolysis was studied. By measuring the results of thermocouple and infrared camera on the back of the material temperature, verify the feasibility of the non-contact temperature measurement method. By using the experimental material on the temperature and mass loss rate. Combined with ThermoKin model Stanislav I. Stoliarov are piecewise linear relation between thermal conductivity and temperature of the material. Then on the basis of experiment established a one-dimensional model of heat absorption material surface pyrolysis and pyrolysis reactions of non carbonized polymer materials, the absorption depth and surface model is widely used in the literature of the two absorption the hypothesis were studied and compared, the results showed that different absorption layer temperature distribution have great effect on the material surface temperature and thermal penetration, this kind of Different in the atmosphere is reflected in the difference in ignition time. In the macro aspect that is not considered material pyrolysis, pyrolysis and internal details of the case, the simulation results of both were in the acceptable range. By comparing the experimental and simulated weightlessness rate and the temperature of the results validate the correctness of the one-dimensional pyrolysis model.
The fire spread, based on the research on the pyrolysis of natural convection and different environment under the pressure of the counter current fire spread processes are analyzed theoretically and experimentally. The results show that the width of material under the condition of low increase rate increases with the thickness of the fire spread countercurrent increased, and the two-dimensional unconditional width limit the conclusion has great difference the main reason is that the finite size conditions, the combustion process of material on both sides of the spread rate. In the case of fixed thickness, the fire spread rate is inversely proportional to the width of material. In Hefei, Xining and Lhasa under different environmental stress conditions, the weight loss rate, flame height and fire spread rate increases along with the pressure increases at low pressure. Under the condition of gas phase chemical reaction kinetics and flame heat feedback are the main factors influence the fire spread rate, the number of Damkohler when the characterization of gas phase chemical reaction is less than a critical value will have stalled This phenomenon. From the view of the heat and mass transfer of fire spread process is analyzed and simplified model, the model of material fire spread rate is the size of the material, the function of flame front angle and thermal physical parameters. In addition, this model also provides by measuring the fire spread rate estimation method of flux flame pyrolysis zone and preheating zone feedback. Also, the models and experimental results illustrate the validity of the simplified model is in good agreement.

【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】：2014
【分類號】：TU564

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本文編號：1436827