高海拔环境下燃料着火特性及燃烧强化研究

发布时间：2018-04-18 08:10

本文选题：高海拔环境 + 着火特性　；参考：《中国科学技术大学》2017年博士论文

【摘要】：燃烧是受流动、传热传质和化学反应控制的极其复杂的物理化学过程。燃烧过程会不同程度地受到外部环境条件的影响,尤其是外部环境压力和氧气浓度,对燃烧的影响极大。而在我国广阔的高原地区,特别是中印边界,其较高的海拔高度造成了低压、低氧(主要指氧气密度)、低温的独特环境条件。这种环境条件的差异将会导致燃料在这些地区独特的着火和燃烧特性。研究发现,随着海拔高度的增加,不断降低的环境压力会使燃料的火灾危险性显著提高,同时在燃烧时发生严重的燃烧衰减现象。一个典型实例是高原燃烧炉在实际应用过程中会出现诸如点火难、燃烧效率低、燃烧不充分、炭烟生成量高、燃烧不稳定等诸多问题。这些问题严重制约着高原能源利用效率,在军事和民用的众多方面造成了严重的资源浪费和技术难题。因此,研究高海拔低压低氧环境条件下燃料的着火和燃烧特性,不仅事关高原地区的火灾安全防控,而且对提高高原地区的能源利用效率具有重要意义。本文以高原常用的-35#柴油(多组分复杂燃料的代表)为研究对象,依托青藏高原天然的海拔高度差,优选包括合肥在内的6个不同海拔高度的地区(合肥(50m)、西宁(2270m)、格尔木(2830m)、拉萨(3650m)、羊八井(4300m)、沱沱河(4780 m))开展实地的着火和燃烧实验,采用实地实验、数值模拟及理论分析等研究手段,将燃料基础着火及燃烧特性研究,燃料的高原燃烧强化研究与燃烧器优化设计有机结合。具体内容概括如下:研究主要分别两部分:第一部分为燃料高原着火特性研究;第二部分是燃料的高原燃烧特性及燃烧强化研究。着火特性的研究方面分为两步,首先关注液态燃料的闪点随海拔高度(压力)的变化规律及其预测模型的建立。利用全自动闭口闪点测定仪,通过实地实验,揭示了液体燃料的闪点随海拔高度升高而呈现非线性降低的变化规律。进而以 Clausius-Clapeyron 方程和 Le Chatelier's flammability rule 为基础,建立了两种闪点预测模型,这两种模型能够准确预测单一组分燃料和复杂多组分燃料在不同海拔高度的闪点值。之后,我们利用FDS 6.0对燃料的气相着火过程进行数值模拟研究,通过对PMMA热解着火过程中的对流热损失、气体扩散系数、热解气层厚度以及热解气层浓度梯度等通过实验难以测量的参数的研究,深入探究压力对燃料着火过程的影响机制。燃烧特性及燃烧强化方面,主要探究高海拔低压低氧环境对燃料燃烧的削弱作用,同时提出两种可能的燃烧强化方法:一是通过火旋风改变燃烧炉的燃烧形式的方法来进行燃烧强化。通过对比火旋风和池火的燃烧特性,如燃烧速率、热释放速率、燃烧效率以及火焰温度等,对火旋风的燃烧强化的效果进行量化。二是通过使用过氧化物添加剂改变燃料特性的方法进行燃料的着火和燃烧强化。通过对比实验研究添加剂含量对着火和燃烧强化效果的影响,并对其着火和燃烧强化效果进行量化。获得的实验数据为新型火旋风高原燃烧炉的设计和制造提供理论依据。最终,在燃料高原着火特性和燃烧特性的实验和理论研究基础上,结合高原燃烧强化方法的研究,设计新型火旋风高原燃烧器,通过实地测试和改进,针对性的解决现有高原炊事燃烧器实际应用中出现的点燃难、燃烧效率低、能源利用率低、炭烟生成量高、燃烧不稳定、设备故障率高等问题。
[Abstract]:The combustion is affected by flow, extremely complex physical and chemical process of heat and mass transfer and chemical reaction control. The influence of the combustion process in different degrees by the external environment, especially the external pressure and oxygen concentration, great effect on combustion. In the plateau region of our country broad, especially India, its high the altitude caused by low pressure, hypoxia (mainly oxygen density), unique environmental conditions at low temperature. This will lead to differences of environmental conditions in these areas unique fuel ignition and combustion characteristics. The study found that, along with the altitude increasing, decreasing the environmental pressure will make the fire risk of fuel increased significantly, at the same time the occurrence of serious burning in the combustion of attenuation phenomenon. A typical example is the plateau combustion furnace will appear such as ignition difficult in the actual application process, low combustion efficiency, combustion is not sufficient, carbon Smoke generation, combustion instability and other problems. These problems restrict the high energy efficiency, resulting in waste of resources and serious technical problems in many aspects of military and civilian. Therefore, the combustion and ignition characteristics of high altitude conditions under hypobarichypoxicconditions fuel, not only related to fire safety prevention and control in plateau area moreover, it has important significance to improve the efficiency of energy utilization in plateau area. The plateau used -35# (on behalf of diesel fuel complex multi-component) as the research object, based on the natural elevation of the Qinghai Tibet Plateau height difference, preferably including Hefei, 6 different altitude regions (Hefei, Xining ((50m) 2270m), Golmud (2830m), Lhasa (3650m), Yangbajing (4300m), Tuotuohe (4780 m)) to carry out field ignition and combustion experiments, using the field experiment, the research means of numerical simulation and theoretical analysis, the Study on ignition characteristics and combustion of fuel, fuel combustion burner plateau to strengthen research and optimization design of organic combination. The specific contents are summarized as follows: To study the main two parts: the first part is the fuel ignition characteristics of the plateau; the second part is the study of combustion characteristics of fuel and combustion enhancement. On the plateau combustion characteristics is divided into two steps. Focus first on liquid fuel flash point with altitude (pressure) to establish the rules and prediction model. By using automatic closed flash point tester, through field experiments, reveals the liquid fuel flash point with the increase of altitude variation and nonlinear decreases. Then the Clausius-Clapeyron equation and Le Chatelier's flammability rule as the foundation, set up the two flash point prediction model, the two model can accurately predict the single component and multicomponent gas fuel The material in different altitude flash point value. After that, we use FDS 6 for fuel gas ignition process is simulated, by burning the convective heat loss in the process of PMMA pyrolysis, gas diffusion coefficient, the thickness of gas reservoir and Study on pyrolysis pyrolysis parameters by concentration gradient experiments is difficult to measure, in-depth exploration of the the mechanism of ignition process pressure on fuel. Combustion characteristics and combustion enhancement, mainly to explore the high altitude hypobaric hypoxia on the weakening effect of fuel combustion, and proposes two kinds of possible combustion enhancement methods: one is through the fire whirlwind combustion furnace combustion method change form to combustion enhancement. Through the contrast and combustion characteristics of fire whirl pool fire, such as burning rate, heat release rate, combustion efficiency, flame temperature, to quantify the fire whirl combustion enhancement effect. The two is the Method of changing fuel properties with peroxide additives for ignition and combustion enhancement of fuel. By comparing the experimental study of additive content on ignition and combustion enhancement effect, and the ignition and combustion enhancement effect was quantified. The experimental data provide a theoretical basis for the new type of cyclone combustion fire plateau design and manufacture of furnace. In the end, the fuel ignition characteristics and combustion characteristics of the plateau based on the experiments and theoretical studies, combined with the research methods of combustion enhancement plateau, design of a new type of fire whirlwind plateau burner, through field test and improvement, solve the existing plateau cooking burner used in the ignition difficult, low combustion efficiency, low energy utilization, carbon smoke generation of high combustion instability, high rate of equipment failure.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ038.1

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