我国煤田火区分布广泛，严重影响着当地的生态环境与居民生活健康水平，其形成与蔓延过程复杂，是我国煤炭行业所面临的严峻挑战。加强对煤田火区燃烧蔓延裂隙供风流场变化规律的研究，有助于掌握煤田火区演化机制，为煤火灾害防控提供基础。

       本文通过搭建煤田火区物理相似模型，研究煤田火区燃烧蔓延过程温度场分布及裂隙位置特征，掌握火区煤层温度传播及其燃烧特征参数。结合数值模拟，研究煤田火区燃烧蔓延裂隙供风流场变化规律。其主要研究成果如下：

       设计优化煤火灾害热动力过程模拟测试装置，以陕西神木炭窑渠煤田火区为模拟原型，搭建物理相似模型，模拟其燃烧蔓延热动力过程。通过热重实验，确定出煤氧燃烧特征温度点，以着火温度为界限，划分煤层燃烧锋面向两端蔓延过程为局部燃烧阶段，而燃烧锋面扩展至整个面后向前蔓延过程为整体燃烧阶段。结果表明：煤岩体温度场呈椭圆形弧面传播形式，而高温区集中分布在燃烧区并逐渐向四周蔓延。其上覆岩层中沿径向方向上形成的贯通地表裂隙位于距点火位置上方330 mm处；在竖直切面形成“U”型裂隙。通过定量计算发现燃烧阶段内煤层温度随时间的变化规律符合Logistic模型。而燃烧蔓延过程中煤层温度随着距离的增大而降低，呈指数函数负相关关系；煤层平均燃烧半径以及边界方向的蔓延速率随时间增加而增大，呈指数函数正相关关系；而煤层方向的蔓延速率随时间的增加而减小，呈指数函数负相关关系，最终稳定在约0.36 mm/h。

       基于物理相似模拟实验参数以及热物理特性参数建立煤田火区几何模型，进行煤田火区燃烧蔓延裂隙供风流场数值模拟，并对比实验与模拟温度场分布特征，验证模型的合理性。对比分析煤田火区形成扩展并蔓延至不同位置时的流场分布发现，在火区扩展并蔓延过程中，初始裂隙同时作为进风与回风通道，待煤层覆岩垮落产生新的裂隙后，初始裂隙作为主要进风路径，而新裂隙则成为主要回风路径。随着火区继续燃烧蔓延，初始裂隙垮落封堵，产生新的裂隙，如此循环往复。其中，在局部燃烧阶段内裂隙贯通地表边界上不同位置处的流速呈“W”形状，其极小值点为进风与回风区域的交界点；随着高温区的不断扩展，交界点逐渐向两端扩展，且裂隙内的进风量与回风量均逐渐增大。在整体燃烧阶段内随着燃烧区向前蔓延，交界点逐渐向裂隙水平方向一端移动，直至部分回风区域完全消失。同时，裂隙内的进风量与回风量逐渐减小，待产生新裂隙后，大幅度增加，约为初始状态的1倍左右。

        Coalfield fire areas are widely distributed in China, which seriously affect the local ecological environment and residents’ life and health. Its formation and spread process is complex, which is a severe challenge faced by China’s coal industry. Strengthening the research on the variation law of fracture air supply flow field in the process of combustion spread in coalfield fire area will help to master the evolution mechanism of coalfield fire area and provide the basis for coal fire disaster prevention and control.

        In this paper, the physical similarity model of coalfield fire area is established to study the distribution temperature field and the characteristics of fracture position in the process of combustion spread in coalfield fire area, and master the variation law of coal seam temperature spread and combustion characteristic parameters in fire area. Combined with numerical simulation, the variation law of air supply flow field of combustion spread fracture in coalfield fire area is studied. The main research contents are as follows:

        The thermal dynamic process simulation test device of coal fire disaster is designed and optimized, and a physical similarity model is built to simulate the thermal dynamic process of combustion spread, taking Shaanxi Shenmu coal kiln canal coalfield fire area as the simulation prototype. The characteristic temperature points of coal oxygen combustion are determined through thermogravimetric experiment. Taking the ignition temperature as the boundary, the spreading process of coal seam combustion front towards both ends is divided into local combustion stage. The process of spreading forward after the combustion front extends to the entire face is the overall combustion stage. The results show that the temperature field of coal and rock is in the form of elliptical arc, while the high temperature area is concentrated in the combustion area and gradually spreads to the surrounding area. The through surface fracture formed along the radial direction in the overlying strata is located at 330 mm above the ignition position, and a “U” shaped fracture is formed in the vertical section. Through quantitative calculation, it is found that the variation law of coal seam temperature with time in the combustion stage conforms to the “Logistic” model. In the process of combustion spread, the coal seam temperature decreases with the increase of distance, showing a negative correlation of exponential function. The average combustion radius of coal seam and the spread rate of boundary direction increase with the increase of time, showing a positive correlation of exponential function. However, the spreading rate in the direction of the coal seam decreases with the increase of time, which is negatively correlated with an exponential function, and finally stabilizes around 0.36 mm/h.

        Based on the physical similarity simulation experimental parameters and thermophysical characteristic parameters, a geometric model of the coal field fire area was established, and the numerical simulation of the air supply flow field in the combustion propagation fracture in the coalfield fire area is carried out, and the distribution characteristics of the experimental and simulated temperature fields are compared to verify the rationality of the model. The comparative analysis of the flow field distribution when the coalfield fire area expands and spreads to different locations shows that in the process of fire area expansion and spread, the initial fracture acts as both the inlet and return air channels. After the collapse of coal seam overlying rock produces new fracture, the initial fracture acts as the main inlet air path, and the new fracture becomes the main return air path. As the fire area continues to combustion spread, the initial fracture collapse and seal, creating new ones, and so on. In the local combustion stage, the flow velocity at different positions of the fracture boundary on the surface is in the shape of “W”, and its minimum point is the nodal point of the inlet and return air areas. With the continuous expansion of the high temperature area, the nodal point gradually expands to both ends, and the air intake and return air volume in the fracture gradually increase. In the whole combustion stage, as the combustion area spreads forward, the nodal point gradually moves to one end of the fracture in the horizontal direction until part of the return air area completely disappears. At the same time, the inlet and return air volumes in the fracture decrease gradually, and increase greatly after the new fracture is generated, which is about 1 times of the initial state.

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