煤自燃过程的介尺度特性研究

The coal mine fire in our country is type various, dangerous and wide covered, which has seriously affected the safe production of the coal mine enterprise. The existing researches on coal spontaneous combustion are mostly focused on individual behavior of single particle and bulk coal, which cannot fully explain the nature of the coal spontaneous combustion. To reveal the mechanism of coal spontaneous combustion, this project combines the macro characteristics of coal spontaneous combustion process with the microscopic changes by using the mesoscale research method. Firstly, the concept of the mesoscopic scale on coal spontaneous combustion are presented, following which the reconstruction algorithm based on the structure evolution of coal pile is developed and the formation mechanism of the mesoscale structure (namely the particle cluster) is explored. Secondly, the physical field distribution is studied through simulation based on the reconstructed mesoscale structure. Thirdly, by using the correlative mesoscale methodology, the general rules of flow and heat transfer inside the mesoscale structure is summed up, the parameter transfer function between different scales is proposed, and the mesoscale numerical model of coal spontaneous combustion is established. Fourthly, the experiment platform of coal spontaneous combustion with multi-scale characters is set up, and the mathematical model is verified by the experimental results. Lastly, taking a typical coal pile as an example, the multi-scale model is used to reproduce the self-heating behavior of coal, and the occurrence and development of high temperature zone.

我国煤矿火灾类型多、危险性大、覆盖面广，已严重影响到煤矿企业的安全生产。现有的煤自燃研究多集中在单颗粒和堆积煤体的个体行为上，不能完全解释煤自燃的本质。本项目利用介尺度研究方法，将煤自然发火过程的宏观特征与微观变化相关联，以进一步揭示煤自然发火机理。首先明确煤自燃介尺度现象的概念、内涵及外延，给出各尺度的定义描述和划分原则，提出堆积煤体空间结构衍化的重构算法，探索颗粒聚团的介尺度结构形成机理；基于颗粒聚团重构结构，通过仿真模拟研究介尺度结构下物理场分布规律；以关联型介尺度研究方法为指导，以不同聚团结构为控制条件，归纳聚团内部流动和传热的共性规律，提出尺度间的参数传递函数，建立煤自燃介尺度数值模型；搭建具有多尺度模型特征的煤自然发火实验台，利用实验测试结果验证数学模型的合理性；最后以典型煤堆为例，利用构建的多尺度模型，重现煤体自热行为及高温区发生发展规律。

煤炭自然发火存在明显的介尺度特性，应用介尺度科学理论将煤炭自然发火的微观反应机理与宏观变化特征相关联，有助于进一步解释煤自燃的本质，推进煤自燃领域的深入研究。本项目给出了煤自燃现象中各尺度的定义描述与划分原则，探索了单煤颗粒、煤颗粒聚团及煤堆3个尺度的区别及相互联系，并由此明确了煤自燃研究中介尺度II所在的堆积态煤体层次的物理过程与数学概念；基于显微断层扫描实验重构方法与离散元模拟数字重构方法，发展了颗粒聚团介尺度堆积结构分形理论，提出了介尺度孔隙结构的中轴提取重构算法，明确了颗粒聚团空间结构特性；基于颗粒聚团重构结构，建立介尺度数值计算模型，模拟计算了颗粒聚团内隙间流动、共轭传热与扩散等多耦合物理过程，归纳了颗粒聚团内各颗粒分辨物理场的共性规律；基于不同尺度之间有效参数的本构关系，提出从孔隙尺度获取宏观控制方程中孔隙率、渗透率、惯性系数和对流换热系数的尺度上联方法，从数学上实现了孔隙尺度微观模型到表征体元尺度宏观模型之间的信息传递，从而完成了从孔隙尺度到表征体元尺度的多尺度物理建模和数学建模；建立了煤自燃多尺度预测模型，以采空区内现场实测数据验证了数学模型的合理性，重现了多物理过程耦合作用下的煤体自热行为，获得了煤自然发火过程中高温区域发生发展与蔓延规律。