不同温度煤裂隙流动优势性的热流固耦合数值模拟

Numerical simulation of thermal-fluid-solid coupling of the flow dominance of coal under different temperature conditions

煤层温度因采深加大而不断升高,煤体孔裂隙中的流体在不同温度条件下的优势流动方向和流动优势参数均不同。研究不同温度条件下煤体孔裂隙中的瓦斯流动优势性,对防治煤与瓦斯突出灾害的发生具有重要意义。采用COMSOL Multiphysics有限元软件建立了含瓦斯煤体的热流固耦合数值模型,并基于Monte-Carlo法模拟煤体裂隙,在4种试验温度条件下研究了瓦斯在全贯通裂隙、部分连通裂隙和孔隙中的流动特征。结果表明:在模型边界载荷恒定、边界渗流瓦斯压力差恒定以及煤体温度处处相同的情况下,煤体温度越高,煤体孔裂隙中的瓦斯压力、瓦斯压力场范围以及瓦斯压力梯度越大。煤体温差变化越大,煤体孔裂隙中的瓦斯渗流速度、瓦斯渗流速度场范围以及煤体孔裂隙的渗透性变化越大,具体表现为:全贯通裂隙较其他孔裂隙的瓦斯压力、瓦斯压力场范围和瓦斯压力梯度更大;全贯通裂隙较其他孔裂隙中的瓦斯渗流速度、瓦斯渗流速度场范围和煤体孔裂隙的渗透率更大。因此,在4种试验温度下,温度越高且温差越大时,煤体全贯通裂隙中的瓦斯流动优势性越大,瓦斯更易沿全贯通裂隙进行渗流。

The temperature of the coal seam continues to rise due to the increase of coal seam mining depth,and the fluid in the pores and cracks of the coal body has different flow directions and flow advantages parameters under different temperature conditions,and it is of great significance to study the dominance of gas flow in pores and crackss of coal seams at different temperatures to prevent coal and gas outburst disasters.In this paper,finite element software COMSOL Multiphysics was used to establish a thermal-fluid-solid coupling numerical model gas-containing coal,and based on the Monte-Carlo Method,the coal seam crack was simulated.The flow characteristics of gas in partially connected fractures and fully connected fractures were studied at four different temperatures.The results show that under the condition of constant model boundary load,the boundary seepage gas pressure difference is constant,and the coal body temperature is the same everywhere.The higher the coal temperature is,the greater the gas pressure and the gas pressure gradient and the range of gas pressure field are.The greater the change in coal temperature difference,the greater the gas flow velocity,gas seepage velocity field in the pores and fissures of the coal,and the permeability of the pores and fissures of the coal.The results show that:the gas pressure,gas pressure gradient and gas pressure field range of the full-through fracture is larger than that of other fractures.Compared with other pores and fractures,the gas seepage velocity,gas seepage velocity field range and the permeability of coal pores and fissures are larger in allthrough fractures.Therefore,under four kinds of test temperature conditions,the higher the temperature and the greater the difference in temperature,the greater the advantage of gas flow in the full-through fractures of the coal body,and the easier it is for gas to seep along the full-through fractures.