小尺度薄层扬沸火灾特性实验研究

发布时间：2018-04-14 04:25

本文选题：薄层扬沸 + 水层过热　；参考：《中国科学技术大学》2017年硕士论文

【摘要】：当今社会经济发展离不开化石燃料的使用,但是人类过度依赖化石燃料带来了一系列问题。其中,我国地形多变,海拔差异巨大,由于可燃液体燃料的不均匀分布,导致成品油运输管道规模不断增长,为了保障高海拔地区油品需求,部分油料输运管道需要穿过高海拔地区。同时,高海拔地区本身储存并持续消耗大量油料,除了民生和商用以外,一个值得关注的特殊使用场景是高原机场。高海拔低压低氧环境会对燃烧过程产生影响,高海拔地区燃料泄露火灾也会呈现出同平原地区不同的新特性。薄层扬沸现象涉及众多基本物理、化学过程,其形成机制至今扔在探索过程当中。本文建立了小尺寸油品扬沸火灾特性实验平台。为了研究压力对小尺寸油盆扬沸的影响,以及油水交界面水层过热水的成因,在三个压力点:合肥(Alt:58m P:101kPa),丽江(Alt:2400m P:76kPa)、拉萨(Alt:3650m P:64kPa)开展实地小尺度垫水池火燃烧。同时,从燃烧控制因素的角度,选取了四种油盆直径:0.15m、0.18m(对流控制)、0.30m和0.40m(辐射控制):初始油层厚度为统一为0.5cm;垫水层厚度取1.0cm、1.5cm、2.0cm;实验油品的选择考虑到使用广度以及前文所涉及的高原机场油料安全,最终确定为航空煤油JetA和0#柴油。监测薄层扬沸火灾的特征物理量有:重量,温度,辐射和声音强度。从质量变化角度,分析了不同变量如何影响以下指标:稳定阶段质量损失速率,扬沸现象发生时剩余油品厚度,扬沸强度。从温度角度,重点分析了水油交界面水层温度过热现象。并得到以下结论:实验观察到扬沸过程由四个阶段构成,并且不同变量会导致扬沸阶段向着突变型和持续型两种趋势发展。油盆尺寸D作为单一变量,随着油盆尺寸的上升,稳定燃烧阶段的质量损失速率上升;扬沸发生时剩余油品的高度下降,扬沸强度下降;环境压力P作为单一变量,随着环境压力上升,稳定阶段的质量损失速率上升,油水交界面水层的过热温度上升,过热程度小幅上升,扬沸现象发生时剩余油品的高度上升,扬沸强度上升;水层厚度hw作为单一变量,随着水层厚度的上升,扬沸阶段的燃烧现象向持续型转变,扬沸强度下降,但需要指出的是,随着水层厚度上升,水层厚度对扬沸阶段的影响逐渐降低,可以预计当超过一定临界条件之后,水层厚度将不会对扬沸现象再造成影响;扬沸强度本身并无法说明扬沸现象是否发生,所以,统计了各个工况下扬沸现象是否发生的结果,得出结论如下:压力作为单一变量时,低压情况下更难发生扬沸现象;当燃料量过少,水层越厚越难以发生扬沸现象;上述这两点同扬沸强度的规律相似。但是,油盆直径作为单一变量时,油盆尺寸越小,扬沸现象越难以发生,这和扬沸强度变化的规律相反,结合扬沸现象发生时剩余油层的厚度规律,油盆尺寸越大,扬沸现象发生时剩余油层的厚度越薄,油水交界面积累的气泡越容易突破,所以,油盆尺寸大时,反而容易发生扬沸。并从气泡动力学、核态沸腾理论出发,分析了水油交界面上水层过热程度、沸腾强度与扬沸现象机制之间的关系。
[Abstract]:In today's economic development cannot do without the use of fossil fuels, but humans over reliance on fossil fuels has brought a series of problems. Among them, China's varied terrain, elevation difference is huge, due to the uneven distribution of flammable liquid fuel, leading to the growing oil transportation pipeline scale, in order to ensure the oil demand in high altitude area, need to pass through the high altitude of some oil transporting pipeline. At the same time, the high altitude region itself and continue to consume a large amount of oil storage, in addition to the people's livelihood and commercial, a special scene of concern is the Plateau Airport. High altitude hypoxia environment will influence the combustion process, high altitude fire fuel leak will show new features the same plain area. Thin-layer boilover phenomenon involves many basic physical and chemical processes, the formation mechanism has thrown in the exploration process. This paper built The size of boilover fire experiment platform. In order to study the effect of pressure on the small size of oil boilover, oil-water interface and causes hot water in the water, three pressure points: Hefei (Alt:58m P:101kPa), Lijiang (Alt:2400m P:76kPa), Lhasa (Alt:3650m P:64kPa) to carry out the field of small scale pool fire. At the same time pad and from the combustion control factors, selecting four kinds of pool diameter: 0.15m, 0.18m, and 0.30m (convection control) 0.40m (radiation control): initial reservoir thickness is uniform for 0.5cm; the thickness of cushion layer is 1.0cm, 1.5cm, 2.0cm; experimental oil selection taking into account the use of the breadth and above relates to the Plateau Airport oil security, eventually identified as JetA kerosene and 0# diesel. The characteristics of the physical quantity monitoring of thin-layer boilover: weight, temperature, radiation and sound intensity. From the angle of quality, analyzes the different factors that affect the following Subject: the stable stage of mass loss rate, occurrence of boilover phenomenon of residual oil thickness, boilover strength. From the angle of temperature, focus on the analysis of the water oil interface layer temperature overheating. And get the following conclusion: the observed boilover process consists of four stages, and different variables will lead to boilover stage toward mutation type and continuous type two trends. The size of the D as a single variable, with the rise of pool size, stable combustion phase of the mass loss rate increased; boilover occurs when the remaining oil height decreased, decreased boilover strength; the environmental pressure of P as a single variable, with the environmental pressure rise, stable stage of mass loss the rate rise, the overheating temperature of oil-water interface layer increased, degree of superheat increased slightly, boilover phenomenon occurred when residual height of oil boilover, rising strength; thickness of HW layer as a single variable, With the increase of the thickness of water layer, change the combustion phenomena of boilover stage to continuous decline, boilover strength, but it should be noted that, with the rising influence of layer thickness, layer thickness of boilover stage decreased gradually, can be expected when more than a certain critical condition, water thickness will not affect the boilover phenomenon strength; boilover itself is unable to explain whether the boilover phenomenon, so the statistics of boilover phenomenon under different conditions is the results, the conclusions are as follows: as a single variable pressure, low pressure situations more difficult to occur boilover phenomenon; when the fuel is too small, the thicker the aquifer to boilover phenomenon; these two points with the boilover intensity of the similar. However, as a single variable of pool diameter, the smaller size of boilover phenomenon is difficult to occur, and the variation of intensity of boilover in combination of boilover phenomenon The thickness of residual oil law occurs, the larger the size of oil, residual oil boilover phenomenon occurred when the thickness of the thinner, water at the junction area tired bubble is easy to break, so the oil of large size, but prone to boilover. And from the theory of bubble dynamics, nucleate boiling, analysis of oil and water the interface layer of overheating, the relationship between the strength and the boiling mechanism of boilover phenomenon.

【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE88

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