Simulation Study On The Law Of Gas Migration Under Buried Pipeline Drainage In Goaf Of Fully Mechanized Face

Based on theories such as Fluid Dynamics, Mass Transfer Theory and Dynamics of Fluids in Porous Media, this paper studies on three-dimensional numerical simulation of the law of gas migration in goaf for buried pipeline drainage by the software FLUENT, combined with the actual situation of30101working face in Shiquan coal mine. According to the general rule of cave-in characters in goaf, it has studied the distribution form of porosity and permeability in goaf, given the semi-empirical relationship for the distribution of "O" ring. The Basic equations are constructed by equation of continuity, momentum equation, diffusion equation and state equation, building a mathematical model with gas mixture nonlinear seepage in goaf. For the differential equations, discretization equations are acquired by the Finite Difference Method (FDM). These equations are solved by adopting the SIMPLE algorithm and quoting staggered mesh. Borrowed the idea of FLUENT6.3User’s Guide that formulas of viscous resistance coefficient and inertial resistance coefficient are derived from Ergun formula, the paper analyses Bachmat’s theory nonlinear seepage in porous medium, given formulas of viscous resistance coefficient and inertial resistance coefficient with gas mixture nonlinear seepage in goaf. The paper studies the effect of gravity,"guide gas zone" of the goaf, dip angle of coal seam on gas concentration distribution in goaf by simulation experiments, and draws conclusions that these three factors affects gas concentration distribution of goaf in three-dimensional numerical simulation. Considering the affects of three factors to reflect factually gas concentration distribution of goaf, the paper studies the law of gas migration in goaf in30101working face in Shiquan coal mine for buried pipeline drainage, gets function relationships of gas drainage concentration each for burial depth of drainage entrance and gas drainage flow. From the point of view of the use and effect of gas drainage, the best location of gas drainage in goaf is that the burial depth of drainage entrance is between25and35m, and the best of gas drainage flow in goaf is between17.1and18.4m3/min, those provide a theoretical basis to optimize parameters of gas drainage in goaf.