二氧化碳（CO2）防灭火技术，因其具有较好的大范围惰化降温效果，已成为多数煤矿防治采空区煤自燃的主要方法之一。其中以液态形式输送压注的 CO2 在进入采空区松散介质区域后，其运移物态主要是非饱和气相状态，而现有分析 CO2 在松散介质中的扩散运移规律以及预测惰化降温范围均是以饱和气相的物性条件进行的，导致技术应用存在参数设计不合理、效果不理想。为了解决上述问题，本文围绕松散介质内液态 CO2 泄放后的相态变化以及非饱和气相 CO2 的渗流特征进行实验研究，结果表明：
（1）基于采空区直注液态 CO2防灭火过程，自主搭建了 CO2泄放渗流测试平台，该装置可用于测试液态 CO2 直注过程中的相态变化以及渗流降温规律，同时可以对非饱和气相 CO2的渗流特性进行研究。
（2）利用液态 CO2泄放实验系统研究了直注过程中松散介质内液态 CO2的相态变化，发现液态 CO2 压入松散介质后瞬间相变形成了大量干冰以及非饱和气相 CO2，实验结果表明干冰扩散范围是松散介质内产生大幅温降的主要区域，随后给出了泄放量，粒径影响下的干冰运移速度计算公式。最后基于沿程压力损失，拟合得出了非饱和气相 CO2在射流方向上的压力计算模型。
（3）开展了不同非饱和气相 CO2渗流实验，研究了不同非饱和气相 CO2在各粒径介质下的流速-压降规律，分析了雷诺数，渗透系数 K，渗流状态转变流速等关键渗流参数的变化规律，同时基于非饱和气相 CO2 真实物性参数以及非达西方程建立了关于非饱和气相 CO2在松散介质中的渗流模型。
（4）基于液态 CO2 泄放实验以及非饱和气相 CO2 渗流模型，通过 COMSOL 软件自定义模块构建了模拟松散介质内非饱和气相 CO2 渗流的数值模型，得到了非饱和气相 CO2 运移过程中的压力以及温度等参数的变化特征，确定了压注口孔径以及介质粒径是影响其渗流传热行为的关键因素。

Carbon dioxide (CO2) fire-fighting technology has become one of the main methods for preventing coal spontaneous combustion in gobs in most coal mines because of its good largescale inerting and cooling effect. However, after the CO2 transported and injected in liquid form enters the loose medium area of the goaf, its migration state is mainly in the unsaturated gas phase state, and the existing analysis of the diffusion and migration law of CO2 in the loose medium and the prediction of the range of inerting and cooling All of them are carried out under the physical properties of saturated gas phase, resulting in unreasonable parameter design and unsatisfactory effect in technical application. In order to solve the above problems, this paper 
conducted an experimental study on the phase change of liquid CO2 in loose coal after the release and the seepage characteristics of unsaturated gas-phase CO2.The results shows :

Based on the process of direct injection of liquid CO2 in the goaf, a CO2 discharge seepage test platform was independently built. This device can be used to test the phase state change and seepage cooling law during the process of liquid CO2 direct injection. The seepage characteristics of gas phase CO2 were studied.

The phase change of liquid CO2 in the loose medium during the direct injection process was studied by using the liquid CO2 release experimental system. The diffusion range of dry ice is the main area where a large temperature drop occurs in the loose medium. Then, the calculation formula of dry ice transport velocity under the influence of flow rate and particle size is given. Finally, based on the pressure loss along the way, the pressure calculation model of unsaturated gas phase CO2 in the jet direction was obtained by fitting.

Conducted CO2 seepage experiments in different unsaturated gas phases, studied the flow rate-pressure drop laws of different unsaturated gas phase CO2 under various particle sizes, and analyzed key seepage parameters such as Reynolds number, permeability coefficient K, and seepage state transition flow rate. At the same time, a seepage model of unsaturated gas-phase CO2 in loose medium was established based on the real physical parameters of unsaturated gasphase CO2 and the non-Darcy equation.

Based on the liquid CO2 release experiment and the unsaturated gas-phase CO2 seepage model, a numerical model for simulating the unsaturated gas-phase CO2 seepage in the loose medium was constructed through the custom module of the COMSOL software, and the pressure during the unsaturated gas-phase CO2 migration process was obtained. As well as the changing characteristics of parameters such as temperature, it is determined that the pore size of the injection port and the particle size of the medium are the key factors affecting its seepage heat transfer behavior.

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