采空区气体流场多尺度数值模拟及热蒸发效应分析

Multi-scale numerical simulation of gas flow field in goaf and thermal evaporation effect analysis

采空区漏风是诱发采空区遗煤自然发火的主要原因之一,然而在不同研究尺度下,采空区气体流动服从不同的规律。利用多尺度关联型分析方法分别从宏观尺度和介观尺度研究了采空区内自由流动域和多孔介质域内稳态流场的速度和压力分布情况;构建了热-流-湿多场耦合模型,并在此基础上使用多物理场模拟软件模拟了煤中水分受气体流动和热蒸发效应影响下的变化情况。结果表明:煤中水分含量会在热蒸发效应下逐渐降低,与热重分析实验得到的结果相吻合;背风侧受流场影响水蒸气的浓度较高;另外受到蒸发吸热的影响,煤体温度场不断发生变化,靠近背风侧煤体内部温度下降较慢。

Air leakage in goaf is one of the main reasons for spontaneous combustion of residual coal. However, under different research scales, the gas flow in goaf follows different laws. In this paper, the velocity and pressure distribution of steady-state flow field in free flow domain and porous media domain in goaf are studied by using multi-scale correlation analysis method from macro scale and meso scale respectively. The heat flow moisture multi-field coupling model is constructed, and on this basis, the change of moisture in coal under the influence of gas flow and thermal evaporation is simulated by using multi-physical field simulation software. The results show that the moisture content in coal will gradually decrease under the effect of thermal evaporation,which is consistent with the results of thermogravimetric experiment. The concentration of water vapor on the leeward side is higher affected by the flow field. In addition, under the influence of evaporation and heat absorption, the temperature distribution of coal body will change continuously, and the internal temperature of coal body near the leeward side decreases slowly.