【作者】 陈东梁；

【导师】 孙金华；

【作者基本信息】 中国科学技术大学 ， 安全技术及工程， 2007， 博士

【摘要】 煤炭将在较长的一段时期内是我国能源的重要来源，虽然国家加大了对煤矿井下安全生产的监管力度和技术投入，但煤矿瓦斯、煤尘爆炸事故仍然时有发生，给国家和人民带来了巨大的伤害和损失。而煤矿井下的爆炸事故往往是瓦斯和煤尘共同参与的，对瓦斯和煤尘共同参与的复合体系的火焰传播特性和机理进行研究，可以为煤矿井下爆炸灾害的预防和控制提供理论基础。本文利用燃烧管道对甲烷／空气预混气体和甲烷／煤尘复合火焰进行了实验研究，对甲烷／空气预混火焰的传播特性进行了分析，对甲烷／煤尘复合火焰的传播特性和机理及其影响因素进行了深入的研究。利用高速纹影仪等技术对闭口管道内甲烷／空气预混气体火焰的传播过程进行了研究，对火焰的传播过程和特征进行了分析。当甲烷含量接近当量值时，预混气体火焰传播中会发生火焰阵面由向未燃区弯曲到向已燃区弯曲的转折过程，逐渐由层流燃烧向湍流燃烧转变并形成Tulip火焰这种特殊的火焰结构。Tulip火焰结构形成于火焰传播速度迅速降低的区间里，且只有当减速阶段的最大加速度绝对值大于某一特定值时（本实验条件下约为156.8m／s²），Tulip火焰结构才能够形成。Tulip火焰结构是预混火焰由层流燃烧向湍流燃烧转变的一个中间过程。研究了燃料组分构成λ（λ=复合体系中甲烷的理论耗氧气量／复合体系中煤尘的理论耗氧气量）、煤尘粒径和煤尘种类对复合火焰传播特性的影响，得到了不同实验条件下的火焰形态、火焰温度和火焰传播速度等表征火焰传播特性的参数，分析了燃料组分构成λ、煤尘粒径和煤尘种类变化时复合火焰传播特性的变化规律。在实验研究的基础上，分析了甲烷／煤尘复合体系燃烧反应特性，提出了甲烷／煤尘复合火焰结构。对燃料组分构成、煤尘粒径和煤尘种类对复合体系燃烧反应特性和火焰结构的影响进行了深入的研究，揭示了复合体系燃烧反应特性和火焰结构的影响因素及其影响规律。甲烷／煤尘复合火焰的传播机理可以描述为：预热区（Z₀）受到火焰前沿的热对流和热辐射而升温；气相火焰区（Z₁）主要为甲烷气体的燃烧，它的燃烧放热一部分传递给未燃区，同时使得煤尘粒子的温度升高；多相燃烧反应区（Z₂）主要为煤尘粒子燃烧构成，在这个区域中，煤尘粒子迅速的热解，挥发分迅速燃烧，形成的焦炭也逐步的开始燃烧；在上一燃烧过程中形成的焦炭在火焰区Z₃中持续的燃烧直至燃烧完毕。复合火焰中甲烷的燃烧决定了温度的上升时刻，而煤尘的燃烧决定了复合火焰温度的最大值。对于甲烷／煤尘复合火焰，和单一的甲烷火焰或者煤尘火焰相比，由于甲烷的参与，使得复合火焰比单一的煤尘火焰具有更高的传播速度；由于煤尘的参与，使得复合火焰比单一的甲烷火焰持续更长的时间，燃烧火焰在更大的区域中存在。更多还原

【Abstract】 The energy supplied by coal will always be an important part of the energy sources in our country in a long term. Although the administration and techniques in the coal mines were enhanced, the methane and coal dust explosion accidents happens frequently in the coal mine. These explosion accidents always carry great damages and losses to the coal miners and our country. Many facts indicate that coal mine explosions were almost induced by the hybrid system of methane and coal dust. However, few investigations focus on the hybrid system of methane and coal dust. The studies on the propagation characteristics and mechanism of methane/coal dust mixture will form the theoretical bases to prevent and control the methane and coal dust explosions in the coal mines. In this study, flame propagating through methane/coal dust hybrid was observed experimentally. The coal dusts were dispersed by premixed methane/air mixture in a vertical rectangle chamber and ignited by an electric spark. High-speed video camera was used to record the images of the propagating flame, photodiode was used to study the emitting light characteristics of the flame, micro-thermocouples and ion current probes were used to measure the flame temperature profile and the reaction behavior of the combustion zone respectively. Combustion behaviors and flame structure of methane/coal dust hybrid propagating flame were analyzed in detail.First, the propagation characteristics of the premixed methane/air flames propagating through a closed tube are explored. The techniques of high-speed Schlieren photography etc are used to study the propagating flames of the premixed gases with different methane concentration in the closed tube. Based on experimental results, Combustion behaviors and characteristics of the premixed gases are analyzed. The results show that, the transformation process of the flame front bend to unburned zone turning into bend to burned will happen during the premixed flame propagation while the equivalence ratio volume approaches to 1, thus the typical tulip flame structure form during the transformation. The premixed flame show typical laminar combustion and the transformation process of the flame front will not happen while the equivalence ratio volume deviates from 1 to a certain extent. The results show also that, the tulip flame structure is a middle stage during the transformation from laminar combustion to turbulent combustion of the premixed flame. The tulip flame structure forms during the period with velocity decrease greatly and it forms only while the acceleration absolute value of the velocity decrease period is larger than a certain quantity （about 156.8m/s² in this experimental condition）.The effects of the fuel ingredient constitutionλ（λ=the theoretical oxygen consumed by the methane in the mixture/the theoretical oxygen comsumed by the coal dust in the mixture）, the diameter distribution of coal dust and coal category on the propagation characteristics of the mixture flame are explored. The parameters of the flame shape, flame temperature and velocity in different experimental conditions are got. Based on the experimental results, the conversion rules between the fuel ingredient constitutionλ, the diameter distribution of coal dust and coal category and the flame propagation characteristics are analyzed in detail.Based on the expmerimantal results, the combustion reaction characteristics of the methane/coal dust mixture are anylized and the flame structures of the methane/coal dust mixture flames are concluded. The effects of the fuel ingredient constitution X, the diameter distribution of coal dust and coal category on the combustion reaction characteristics and the flame structure are explored, and the conversion rules between the fuel ingredient constitution X, the diameter distribution of coal dust, coal category and the combustion reaction characteristics, the flame structure are analyzed in detail.The propagation processes of the methane/coal dust mixture flame could be described by: the temperature of the preheated zone （Z₀） increases according to the thermal convection and radiation from the combustion front; The gaseous combustion zone （Z₁） consists of methane combustion mainly, and the heat produced by Z₁ not only increases the temperature of the preheated zone but also increases that of the coal dusts; Multiple combustion zone （Z₂） consists of heterogeneous coal dust combustion mainly, in which the coal dusts pyrolyze and the volatile matters combust quickly; The coal chars formed in the last combustion process keep combusting till the carbon is exhausted in the combustion zone Z₃.The onset time of the methane/coal dust mixture flame temperature is affected by the methane comsbustion and the maximum volume of that is affected by the coal dust combustion. Comparing with the single methane combustion or single coal dust combustion, the methane participation make the mixture flame propagate with a higer velocity and the coal dust participation make the mixture flame combust in a longer time and a larger zone.更多还原