煤田露头火区热力微循环供氧诱导燃烧蔓延机制

Outcrop coalfield fires are widespread in western China, which have become the major problem endangering energy strategic security and ecological harmony. This subject focuses on the key scientific issues which involve the characteristics of thermodynamic microcirculation for the gas transport outcrop in the coalfield fire area and interaction mechanism between heat transfer and oxygen supply in the combustion center. The main contents of this project are as follows: ① Through the similar simulation for the evolution of overburden cracks and combined with mechanical properties under temperature-pressure coupling, the development and distribution characteristics of overburden cracks will be analyzed to study the evolution of crack channel in the outcrop coalfield fire area. ② Through the similar simulation for the evolution of outcrop coalfield fire and combined with the distribution of crack channels, the dynamic distribution characteristics of heat pressure in crack channels will be investigated to reveal the mechanism of oxygen supply by thermodynamic microcirculation in the combustion center. ③ Based on the theories and methods dynamic heat balance, intrinsic relevance between the variations of heat transfer and oxygen supply in the combustion center will be studied. Furthermore, the mathematical model for combustion center spread will be established. After that, numerical simulation will be done to reveal the combustion evolution mechanism of outcrop coalfield fire induced by the oxygen supply from thermodynamic microcirculation. These studies will be significant for further determining the path of gas transport, understanding the evolution of outcrop coalfield fire, and promoting the progress of theory and technology for coal fire disaster prevention and control.

我国西部地区煤田露头火区分布广泛，严重危害能源战略安全与生态和谐。本项目围绕煤田露头火区气体输运热力微循环特征以及燃烧中心热迁移与氧气供给的关联机制等关键科学问题，开展以下研究：①通过覆岩裂隙演化相似模拟，结合温-压耦合作用下覆岩力学特性测试，研究覆岩裂隙发育及分布特征，揭示煤田露头火区裂隙通道的形成演化规律；②通过煤田露头火区演化过程相似模拟，结合裂隙通道分布规律，研究裂隙通道热力风压动态分布特征，揭示燃烧中心热力微循环供氧机制；③基于动态热平衡理论与方法，研究燃烧中心热迁移与氧气供给的内在关联性，建立燃烧中心蔓延数学模型，并进行数值模拟，揭示热力微循环供氧诱导煤田露头火区燃烧蔓延机制。项目的研究有助于进一步确定煤田露头火区气体输运通道，揭示煤田露头火区演化过程，推动煤火灾害防治理论与技术的发展。

大面积煤田火灾不仅危害当地生态环境，同时造成大量的煤炭资源被损毁或冻结。受煤层赋存条件限制，大部分煤田火灾发生在地下，漏风通道的形成演化十分复杂，火区气体输运与燃烧蔓延过程不清严重制约着煤火灾害防控理论与技术的进步。本项目研究煤田火区热力循环供氧诱导燃烧蔓延机制，取得的主要研究成果如下：①覆岩损伤量随着应变的增大呈指数增长。上覆粉砂岩损伤量随热破坏温度的升高而增大，而细粒砂岩的损伤量随温度的升高先增大后减小。②热破坏粉砂岩加载破坏时产生的表面宏观裂隙大多为轴向弯曲，中部破坏明显；细粒砂岩主要是径向劈裂，破坏集中区分布于两端。③火区覆岩主裂隙长度随煤层损毁距离增大而增大，贯通地表后，其长度降低；倾角随煤层损毁距离增大先减小后增大，贯通地表时倾角最小。此外，主裂隙贯通地表前覆岩垮落步距较小，贯通后覆岩垮落步距增大。④火区覆岩主裂隙倾角随燃煤温度的升高而减小、随着燃煤厚度的增大而增大，长度随煤厚和温度的升高而增大。贯通地表后，倾角随着燃煤温度和厚度的升高而增大，长度随着煤厚和温度的升高而减小。⑤火区煤温随时间的变化符合Logistic模型，与距离呈负指数关系。局部燃烧扩展过程中，初始裂隙进回风交界点逐渐向两端位置扩展，通风量增大。燃烧区沿煤层走向蔓延过程中，进、回风交界点逐渐向裂隙水平方向的一侧移动，通风量逐渐减小，产生新的裂隙后，初始裂隙转变为进风裂隙，由新的裂隙回风，通风量迅速增大。研究成果对判定煤田火区主要漏风通道，推动目前常用的火区封堵、覆盖隔氧防控技术的进步具有重要意义。