基于RNG k-ε湍流模型的3D采空区瓦斯上浮贮移

Simulation of gas migration in 3D goaf based on RNG k-ε turbulence model

为研究工作面后方采空区3D空间瓦斯上浮特征,根据质量守恒、动量守恒和Fick定律,建立综放采空区风流-瓦斯变密度混合气体非线性渗流-扩散控制方程。结合大兴矿N2-706工作面实例,运用CFD软件模拟三维采空区瓦斯运移及分布的状态;流场冒落非均质按照"O"型分布描述,计算采用RNGk-ε湍流模型,并考虑重力场条件。理论计算调整与现场实际条件和瓦斯监测记录数据相拟合,指出三维采空区形成的瓦斯分布及上浮态势,是风流移动、瓦斯组分扩散-弥散和含瓦斯风流密度差引起上浮迁移的结果,也是流场瓦斯不断解吸涌出与漏风不断流入所形成的一种动态平衡结果。研究结果表明,采空区高位抽采流量与抽采获得的瓦斯体积分数近似呈反比例函数关系、与回风巷瓦斯体积分数呈负指数函数关系。

For the study of gas floating characteristics and distribution in 3D goal, according to mass conservation, conservation of momentum, and Fick＇ s law, suitable for fully mechanized goaf, describing the variable density of the airgas mixture, nonlinear flow-diffusion equations were built. Combined N2-706 coal face in Daxing Mine, using CFD software, the author simulated the transport and distribution of gas in 3 D goal. Heterogeneity of caving in flow field was described as the ＂0＂ type. RNG κ-ε turbulence model was used, and taking into account the gravity field conditions. The results of theoretical calculations were consistent with the actual conditions and gas monitoring data. Authors point out that gas floating characteristics and distribution in 3D goaf, is due to the air flow moves, gas diffusion-dispersion, and the floating migration of gas-flow which caused by its density difference, and it is also a dynamic balance, which depends on constant desorption of gas in flow field and continuous inflow of air leakage. The results show that the flux of extracting gas from high drill holes is approximately inversely proportional to the volume percent concentration of extracting gas, and has a negative exponential relationship with volume percent concentration of gas in return air tunnel.