【作者】 陆秋琴；

【导师】 王成军；

【作者基本信息】 西安建筑科技大学 ， 管理科学与工程， 2010， 博士

【摘要】 地下煤矿的主要灾害有煤和瓦斯突出以及瓦斯爆炸,而瓦斯爆炸主要由瓦斯积聚超限引起。为了预防瓦斯积聚超限,防止瓦斯爆炸灾害事故发生,有必要对地下煤矿瓦斯运移流场进行数值模拟计算并对瓦斯积聚的可能性进行评价,以便掌握地下煤矿瓦斯运移规律,为矿山安全管理提供决策依据。地下煤矿瓦斯运移行为是具有多组分、多相态、渗流、浮升和紊流等复杂非线性流动现象的特殊流体运动。格子Boltzmann方法(Lattice Boltzmann Method,LBM)作为一个崭新的求解流体系统偏微分方程的方法以及为物理现象建模的手段,在多相流、多组分流、渗流等问题的模拟中已经得到广泛应用。因此,本文应用LBM对地下煤矿瓦斯运移进行模拟。主要完成了如下研究工作：1.集中涌出瓦斯在巷道中运移的LBM模拟。应用速度-浓度双分布格子Boltzmann模型,建立了基于LBM的瓦斯蔓延速度和浓度模型。在该模型中,采用基于分块耦合算法的速度-浓度LBM模型将巷道分成若干规则的块,对各块分别独立计算,仅在边界处交换数据,简化了网格计算,提高了系统资源利用效率。提出了在LBM模型中增加流动阻力来处理凹凸不平巷道和工作面边界的方法。模拟结果表明,该模拟方法可得到集中涌出瓦斯在通风网络中蔓延的直观信息和其速度、体积分数、压力等大量数据,还可以得到每条巷道内瓦斯体积分数峰值及其个数、位置和到达时间,从而能提供有效的人员避开高浓度瓦斯的方案。2.采场瓦斯运移LBM模拟。基于修正的Brinkman-Forchheimer-Darcy定律,建立了非均质采空区瓦斯运移的控制方程组；基于该方程组分别建立了瓦斯渗流速度场和浓度场的格子Boltzmann模型,实现了采空区瓦斯运移的数值模拟,并对控制采空区瓦斯向上隅角移动的措施进行了模拟对比研究。此外,构建了采场统一的三维LBM数值模拟模型,通过采用不同的松弛时间和平衡分布函数来体现采场气体在工作面的紊流和在采空区的渗流运动特征。模拟结果表明,用该方法可以模拟和分析采场瓦斯运移状况并得到采场瓦斯运移的相关数据：如任何时刻采场内任意位置瓦斯和大气混合气体的流动速度和瓦斯体积分数等数据,同时也可以得到采场流线分布、速度变化和采空区瓦斯运移的规律。3.煤层瓦斯运移LBM模拟。分别建立了等温和非等温煤层孔隙吸附瓦斯扩散和裂隙游离瓦斯渗流的三维双重网格LBM模型。在这些模型中,对于同一煤层采用双重网格技术模拟瓦斯在双重介质的扩散与渗流过程,即一套网格为细网格,用它来模拟吸附瓦斯从煤层孔隙中解吸,变成游离瓦斯,扩散到裂隙的过程；另一套网格为粗网格,用它来模拟游离瓦斯在裂隙中渗流过程。两套网格通过插值实现数据交换,从而实现瓦斯从吸附、解吸到渗流过程的模拟。模拟结果表明,用该方法可以得到任何时刻煤层内任意位置瓦斯的流动速度、压力以及瓦斯浓度等数据,同时也可以得到煤层瓦斯流线分布、速度变化、压力变化和瓦斯运移的规律。该方法可用于揭示煤层瓦斯运移、涌出、突出规律及瓦斯涌出量,为煤层瓦斯涌出、突出的危险性分析与评价提供依据。4.反风期间采场瓦斯运移LBM模拟。分析了反风时期流场的特点,建立了模拟反风时期瓦斯运移的速度场、浓度场和温度场等三场耦合的LBM模型,给出了反风状态下瓦斯运移模型算法和模拟实例。该模拟方法可以为矿山生产期间发生火灾时能否采用反风方式来控制火灾蔓延提供依据。模拟结果表明,用该方法可以得到反风状态下任何时刻巷道和采空区任意位置瓦斯的流动速度、压力、温度以及瓦斯体积分数等数据。该方法可用于揭示反风状态下瓦斯运移规律,为反风的危险性分析与评价提供依据。5.基于双枝模糊Petri网的瓦斯积聚危险性评价。综合考虑对瓦斯积聚的发生有促进作用和抑制作用的影响因素,将模糊Petri网和双枝模糊集理论融合,提出基于双枝模糊Petri网通风巷道瓦斯积聚危险性评价方法。实例表明,该评价方法建立的模型形象直观,充分地利用双枝模糊Petri网描述系统动态行为的能力,描述瓦斯积聚影响因素之间的传播关系。推理过程采用矩阵计算方式,提高了瓦斯积聚危险性评价的效率。本文应用格子Boltzmann方法对地下煤矿瓦斯运移过程进行数值模拟,揭示瓦斯涌出、弥散扩散、运移、上浮和积聚的规律,并因此获得地下煤矿瓦斯运移规律和积聚形成位置及其可行的调控方法。应用模糊Petri网模型对瓦斯积聚的危险性进行评价,为预防瓦斯超限积聚,防止瓦斯爆炸灾害事故发生提供科学的依据。更多还原

【Abstract】 The main disasters of underground coal mine are coal and gas outburst and gas explosion. As is known, gas migration in underground coal mine often results in the gas excessive and even coal-mining pit explosion. To explore the regularity of such gas migration and risk, it is necessary to simulate gas migration and evaluate the risk of gas aggregation in underground coal mine, and then provide decision basis for mine management. The behaviors of gas migration in underground coal mine are special fluid flow with characteristics of multicomponents, multiphase, seepage, buoyancy and turbulence. Lattice Boltzmann method (LBM)is a new method to solve the partial differential equation of fluid systems and a means of modeling for physical phenomenon. It can simulate a rich variety of behaviors, including multiphase flow, multicomponent flow, seepage, et al. So, this paper wishes to propose an approach to the coal-mining gas migration simulation based on the lattice Boltzmann method, major achievements of this thesis are as follows:1.Simulation of concentrative emission gas spreading in tunnel systems based on LBM. A simulation model of concentrative emission gas spreading in tunnel systems has been developed, in which a double distributed velocity-concentration LBM was adopted. In the model, in order to simulate the complicated situations, tunnels were separated into some relative regular blocks through the block coupling algorithms. Each block was calculated in parallel, with the data exchanged only on boundaries. As a result, the redundant grids are removed and the grid computation has been simplified with the system resource efficiency ameliorated. A method which can process rough surface of tunnel or working face by adding flow resistance in LBM model was provided. The simulation results showed that the so-called LBM model is in a position to obtain essential data and information on the velocity, pressure and visual information about the gas in the tunnels. The simulation results also help to disclose the regularities on the distribution of gas bulk fraction in the tunnels, and those on the speed, pressure and bulk fraction of the gas in different points and places in the tunnels, which are of great benefit for mine safety control and management.2. Simulation of gas migration in mining stope based on LBM. Studying the Brinkman-Forchheimer-Darcy amended law, this paper wishes to propose a control system which can reflect the characters of gas migration regularity in heterogeneous goaf of coal mines. To make the complicated control system simple, a Lattice Boltzmann(LB) model constructed to simulate the gas seepage velocity field with another LB model constructed to simulate the gas concentration change have been established. Simulation contrasts in control gas migration methods were also done. This paper also constructed a unified simulation model of gas migration in mining stope based on LBM. The mixed air movement in mining stope is very complex with turbulent flow in the working face and seepage movement in the goaf with heterogeneous porous media. The mining stope unified simulation model reflects the characters of these two fields by different relaxation times and distribution functions. A case study showed:This method can simulate and analyze the situation of gas migration in mining stope and get mass data about gas migration such as speed and gas bulk fraction in every time and every space of the mining stope, and many laws are gained such as laws of streamtrace, speed and gas distribution.3.Simulation of gas migration in coal seam based on LBM. Two 3D double grid LB models which can simulate diffusion of gas adsorbed in pore space and seepage of free gas in fracture have been constructed for Isothermal and non-isothermal coal seam respectively. Double grid technique has been adopted to simulate gas diffusion and seepage in double-porosity of same coal seam, that is, a fine grid was used to simulate adsorbed gas desorbing form pore space, becoming free gas and diffusing to fracture; another coarse grid was used to simulated free gas seeping process in fracture. Two grids exchanged data by interpolation. By this way, simulation of gas migration in coal seam is realized. A case study showed, this method can simulate gas migration in coal seam effectively and get gas mass data such as speed and gas concentration in every time and every space of coal seam, and also obtain law of gas flow streamtrace, speed, press and gas migration. This method can provide a new method for revealing law of gas migration, emission, outburst and volume of emission, and also provide basis for risk evaluation and analysis. 4. Gas migration in stope when reversing air-current. A multi-field coupled model with fields of speed, concentration and temperature has been constructed after analyzing the flow field characteristics when reversing air-current. The paper presented algorithm and simulation case of gas migration in reversing air-current status. The simulation results present basis for decision making when fire accident occurs whether we can control the fire smoke flow by using reversing air-current method. A case study showed, the simulation can get mass data such as gas flow speed, pressure, and temperature and gas bulk fraction in tunnel and goaf when reversing air-current. It can provide a new method to reveal gas migration when reversing air-current, and provide basis for risk evaluation and analysis of reversing air-current.5.Risk evaluation method of gas aggregation based on both-branch decision-making and fuzzy Petri net. After comprehensively considered with factors such as promoting and counteracting influencing factors, an evaluation risk method of gas aggregation in tunnels which based on both-branch decision-making and fuzzy Petri net is presented. A case study showed:The Evaluation risk method can effectively describe the propagation relationship of gas aggregation factors. The model is expressed by figure and is easy to understand, which fully reflects the ability of both-branch fuzzy Petri net to depict the dynamic behaviors of system. The reasoning process adopts simple matrix calculation which improves the efficiency of the risk evaluation.This paper researches on numeric simulation of gas migration in underground coal mine. It discloses the regularities on the gas emission, diffusion, migration, buoyancy and aggregation, and then provides the regularities of gas migration, aggregation position and the control methods. The risk evaluation method of gas aggregation based on both-branch decision-making and fuzzy Petri net can provide decision basis for preventing gas aggregation and coal-mining pit explosion.更多还原