采空区非均质多孔介质渗透特性三维建模及应用
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摘要
为了减小采空区渗透率分布对流场数值模拟精确程度的影响,在岩梁理论和"O"型圈理论研究的基础上,分析了采空区非均质多孔介质孔隙分布规律,建立了采空区孔隙率及渗透率三维分布数学模型;以姚桥煤矿7271综放工作面采空区注CO_2防灭火技术为研究背景,采用FLUENT数值模拟方法,分别研究了采用渗透率三维分布模型及不同固定常数渗透率时采空区气体运移规律,并进行了现场实测对比分析。研究结果表明,沿采空区深度方向,采空区的孔隙率在靠近工作面侧较大;沿工作面倾向,采空区内靠近煤柱侧的孔隙率变化较大,压实稳定区的孔隙率较小。随着渗透率的增大,工作面漏入采空区的漏风量增大,CO_2不易在采空区中聚集;当渗透率减小时,CO_2的体积分数由回风巷侧逐渐向进风巷侧升高。数值模拟采用渗透率三维分布函数得出的结果与实测数据的平均误差为8.0%,小于固定常数渗透率,可为采空区风流场数值模拟研究提供了基础参数依据。
The permeability of goaf has a significant impact on the accuracy of numerical fluid dynamic simulation in goaf.In this paper,the distribution of heterogeneous porous media is analyzed on the basis of Rock Beam Theory and"O"-Ring Theory. Then,a three dimensional mathematical model is established to compute the porosity and permeability of goaf. A numerical model is also built to simulate the CO_2 injection fire prevention and extinguishing technology in No.7271 fully-mechanized caving face of Yaoqiao Coal Mine. The gas migration for different coal permeability are studied in the model with FLUENT and compared with field measurements.The results show that the porosity of coal is larger near the working face. The porosity changes dramatically along the inclined direction of the working face.The porosity changes are larger in the area near coal pillars than that in compacted area.It is also found that it is more difficult for CO_2 to accumulate when the porosity is larger as the amount of air leakage increases.When permeability decreases,the concentration of CO_2 increases gradually from return air roadway side to intake air roadway side.The average difference of permeability between the numerical simulation results using permeability obtained from the 3D permeability distribution model and the measured data is 8.0%,which is smaller than the difference when using constant permeability.The paper provides a basic reference for numerical simulation of air flow in goaf.
The permeability of goaf has a significant impact on the accuracy of numerical fluid dynamic simulation in goaf.In this paper,the distribution of heterogeneous porous media is analyzed on the basis of Rock Beam Theory and"O"-Ring Theory. Then,a three dimensional mathematical model is established to compute the porosity and permeability of goaf. A numerical model is also built to simulate the CO_2 injection fire prevention and extinguishing technology in No.7271 fully-mechanized caving face of Yaoqiao Coal Mine. The gas migration for different coal permeability are studied in the model with FLUENT and compared with field measurements.The results show that the porosity of coal is larger near the working face. The porosity changes dramatically along the inclined direction of the working face.The porosity changes are larger in the area near coal pillars than that in compacted area.It is also found that it is more difficult for CO_2 to accumulate when the porosity is larger as the amount of air leakage increases.When permeability decreases,the concentration of CO_2 increases gradually from return air roadway side to intake air roadway side.The average difference of permeability between the numerical simulation results using permeability obtained from the 3D permeability distribution model and the measured data is 8.0%,which is smaller than the difference when using constant permeability.The paper provides a basic reference for numerical simulation of air flow in goaf.
引文
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[12]郑斌,李菊花.基于Kozeny-Carman方程的渗透率分形模型[J].天然气地球科学,2015,26(1):193-198.ZHENG Bin,LI Juhua.A new fractal permeability model for porous media based on kozeny-carman equation[J].Natural Gas Geoscience,2015,26(1):193-198.
[13]高莎莎,王延斌,倪小明,等.CO2注入煤层中煤储层渗透率变化规律研究[J].煤炭科学技术,2014,42(2):54-57,62.GAO Shasha,WANG Yanbin,NI Xiaoming,et al.Study on laws of coal seam permeability change in CO2-ECBM[J].Coal Science and Technology,2014,42(2):54-57,62.
[14]孟艳军,汤达祯,许浩,等.煤岩气水相对渗透率研究进展与展望[J].煤炭科学技术,2014,42(8):51-55.MENG Yanjun,TANG Dazhen,XU Hao,et al.Progress and prospect of gas-water relative permeability of coal and rock[J].Coal Science and Technology,2014,42(8):51-55.
[2]YUAN L M,SMITH A C.Numerical study on effects of coal properties on spontaneous heating in longwall gob areas[J].Fuel,2008,87(15):3409-3419.
[3]余明高,晁江坤,褚廷湘,等.承压破碎煤体渗透特性参数演化实验研究[J].煤炭学报,2017,42(4):916-922.YU Minggao,CHAO Jiangkun,CHU Tingxiang,et al.Experimental study on permeability parameter evolution of pressure-bear broken coal[J].Journal of China Coal Society,2017,42(4):916-922.
[4]SZLAZAL J.The determination of a coefficient of long wall gob permeability[J].Archives of Mining Sciences,2001,46(4):451-468.
[5]邓军,徐精彩,文虎.采空区自然发火动态数学模型研究[J].湘潭矿业学院学报,1998,13(1):11-16.DENG Jun,XU Jingcai,WEN Hu.Study of dynamic mathematical model of coalspontaneous combustion in mined-out areas[J].Journal of Xiangtan Mining Institute,1998,13(1):11-16.
[6]周西华,王继仁,卢国斌,等.回采工作面温度场分布规律的数值模拟[J].煤炭学报,2002,27(1):59-63.ZHOU Xihua,WANG Jiren,LU Guobin,et al.The numerical simulation of distribution law of temperature field in coal face[J].Journal of China Coal Society,2002,27(1):59-63.
[7]高光超,李宗翔,张春,等.基于三维“O”型圈的采空区多场分布特征数值模拟[J].安全与环境学报,2017,17(3):931-936.GAO Guangchao,LI Zongxiang,ZHANG Chun,et al.Numerical simulation for multi-fielddistribution characteristic features ofthegoaf based on 3D“O”type circle[J].Journal of Safety and Environment,2017,17(3):931-936.
[8]WOLF H K,BRUINING H.Modelling the interaction between underground coal fires and their roof rocks[J].Fuel,2007,86:2761-2777.
[9]梁运涛,张腾飞,王树刚,等.采空区孔隙率非均质模型及其流场分布模拟[J].煤炭学报,2009,34(9):1203-1207.LIANG Yuntao,ZHANG Tengfei,WANG Shugang,et al.Heterogeneousmodel of porosity in gobs and its airflow field distribution[J].Journal of China Coal Society,2009,34(9):1203-1207.
[10]高建良,王海生.采空区渗透率分布对流场的影响[J].中国安全科学学报,2010,20(3):81-85.GAO Jianliang,WANG Haisheng.Influence of permeability distribution on airflow field of leakage in gob[J].China Safety Science Journal,2010,20(3):81-85.
[11]王伟,程远平,刘洪永,等.基于sigmoid函数的采空区渗透率模型及瓦斯流场模拟应用[J].采矿与安全工程学报,2017,34(6):1232-1239.WANG Wei,CHENG Yuanping,LIU Hongyong,et al.Permeability model of gob based on sigmoid functionand application in the airflow field simulation[J].Journal of Mining&Safety Engineering,2017,34(6):1232-1239.
[12]郑斌,李菊花.基于Kozeny-Carman方程的渗透率分形模型[J].天然气地球科学,2015,26(1):193-198.ZHENG Bin,LI Juhua.A new fractal permeability model for porous media based on kozeny-carman equation[J].Natural Gas Geoscience,2015,26(1):193-198.
[13]高莎莎,王延斌,倪小明,等.CO2注入煤层中煤储层渗透率变化规律研究[J].煤炭科学技术,2014,42(2):54-57,62.GAO Shasha,WANG Yanbin,NI Xiaoming,et al.Study on laws of coal seam permeability change in CO2-ECBM[J].Coal Science and Technology,2014,42(2):54-57,62.
[14]孟艳军,汤达祯,许浩,等.煤岩气水相对渗透率研究进展与展望[J].煤炭科学技术,2014,42(8):51-55.MENG Yanjun,TANG Dazhen,XU Hao,et al.Progress and prospect of gas-water relative permeability of coal and rock[J].Coal Science and Technology,2014,42(8):51-55.