CFD modelling of longwall goaf gas flow to improve gas capture and prevent goaf self-heating

CFD models have been developed to investigate the longwall goaf gas flow patterns under different mining and geological control conditions. The longwall goaf was treated as porous regions and gas flow was modelled as a momentum sink added to the momentum equation. Gas desorption from the caved goaf and destressed coal seams within the mining disturbed area was modelled as additional mass sources in the continuity equation. These CFD models were developed according to specific longwall layouts and calibrated against field monitoring data. Two case studies were presented demonstrating the application of CFD modelling of goaf gas flow characteristics for improved goaf gas capture and the reduction of oxygen ingress into the goaf areas for self-heating prevention. Results from the case studies indicate that the optimum goaf drainage strategy would be a combination of shallow (near the face) and deep holes to improve the overall drainage efficiency and gas purity. For gassy longwall faces retreating against the seam dip, it is recommended to conduct cross-measure roof hole drainage targeting the fractured zones overlying the return corner, rather than high capacity surface goaf drainage deep in the goaf.     

采空区瓦斯流动规律的CFD模拟

采用CFD数值模拟方法对采空区瓦斯流动及分布规律进行了研究.阐明了计算流体力学CFD模拟的理论基础，介绍了运用FLUENT程序开发CFD模型的方法，并运用所开发的CFD模型对张北矿11418工作面采空区瓦斯流动规律以及地面钻孔抽放条件下瓦斯流动规律进行了模拟，模拟结果表明:采空区回风巷侧的最大瓦斯浓度可达80％.同时表明:采用CFD模型研究采空区瓦斯流动规律是可行的方法之一.     

The development of a CFD model of a submerged arc furnace for phosphorus production

A computational fluid dynamics (CFD) based model of a submerged arc furnace for the production of phosphorus was developed. The model was constructed to investigate the influence of changing operating conditions on energy distribution within the burden and reaction characteristics such as the position of the solid–gas reaction zone. Two user-developed models generate a volumetric distribution of the mass sources and energy sinks within the packed bed region. Boundary conditions, initial values and material specifications are provided by industrial measurements, laboratory experiments and a combination of empirical and thermodynamical data. The results provide three-dimensional furnace characteristics of gas flow, energy distribution and chemical reactions that will give decision support for a predictive, Dynamic-CFD hybrid model [Scheepers, E., Yang, Y., Reuter, M., Adema, A., 2006. A dynamic-cfd hybrid model of a submerged arc furnace for phosphorus production. Minerals Engineering 19 (3), 309–317].     

乏风氧化装置进气导流的流动均匀性研究

 运用计算流体力学（CFD）方法对乏风氧化装置内气流流动规律进行数值计算。研究不同导流板安置方式、板形、板长以及导流板数量对流动均匀性的影响。模拟结果表明：末端悬空的导流板对流动均匀性的影响明显好于末段封闭的导流板;弯板对改善氧化床内气流均匀分布的效果最明显,梯形板次之,直板最差;板长也是影响流动均匀性的重要参数之一,全板的流动均匀性最好,导流板相对板长越短,氧化床内气流分布均匀性越差;导流板的数量对流动均匀性也有较大影响,导流板数量越多流动均匀性越好,对应靠近入口处的氧化床内速度也越低。     

煤与瓦斯突出流体动力学机理研究

煤与瓦斯突出是威胁煤矿安全生产的重大灾害,近年来随着对深部煤炭资源需求增加,煤和瓦斯突出次数和强度也日趋严重。运用流体动力学基本原理探讨突出过程中瓦斯气体压强和流速变化,研究表明游离态瓦斯气体在煤岩体内高速流动时产生的压强波可在煤层裂隙网中不断积累传播。而煤层中压强波的出现不仅能够改变裂隙中瓦斯气体流速和压力并扩展煤层裂隙,使含瓦斯煤岩体孔隙结构破坏,最终导致煤与瓦斯突出灾害发生。     

CFD modelling of fluid flow in a Peirce–Smith converter with more than one injection point

Copper converting is mainly conducted in Peirce–Smith converters. Extensive work has been conducted to understand fluid flow phenomena as air is injected into molten mattes. High momentum must be transferred from the gas to the melt in order to refine the metal. In this work, we present a CFD analysis of gas injection with one and three tuyeres. Results show that by increasing the number of injection points, the flow pattern within the converter change considerably. Such changes result in the development of large recirculation zones and localised eddy formation. Additionally, it was found that the gas plumes in the melt are asymmetrical thus flow paths constantly interfere between themselves. Bubbling–jetting transition is found to be better represented by the Kutateladze number.     

KYF型浮选机三相流仿真研究初探

CFD方法在浮选机三相流动仿真中的应用,对于揭示浮选过程和优化浮选设备具有重要意义。本文以大型浮选机KYF-160为研究对象,揭示了浮选机内三相流动特征以及气、固两相含率的分布。本文研究了矿石不同单一粒径下,固相含率的分布特点及其影响。矿石颗粒固相含率的分布特点与工程实际一致。矿石粒径的增大,会导致浮选机底部矿粒沉积现象严重,顶部固相含率变低。本文探究了多粒径体系下,浮选机内固相含率的分布特点。较粗的颗粒更难悬浮,因此,浮选机对于矿石入选粒径有一定要求。     

Computational study of gas quenching on carburizing hypoid ring gear

Due to its pure convective heat transfer, flexible process parameters, and clean nontoxic quenching medium, gas quenching has become a solution to traditional quench distortion and growing environmental problems. To further improve the productivity of gas quenching, the present quench pressure and flow velocity have been increased to five or more times greater than those common 10 to 20 years ago. Thus, the nonuniformity problem of gas quenching has arisen. Previous works have shown that, by varying the quench pressure, flow velocity, gas type, rack design, and furnace ducts, the uniformity of gas quenching process can be improved. In this paper, the relationships among gas pressure, flow velocity, and cooling-speed uniformity were investigated by CFD analysis coupled with experimental validation. Results indicate that the uniformity of the gas-quenching process can be improved by increasing the quench pressure and decreasing the flow velocity. This can be explained by the smoother gas flow around parts treated with higher quench pressure and lower flow velocity. In addition, it is found from the obtained results that the configuration of parts may influence the cooling capability and uniformity of a gas-quenching process significantly.     

回转窑内流动传热和燃烧过程数学模型的研究现状及其发展趋势

对国内外有关回转窑内流动传热过程数学模型进行了全面系统地综述,分别探讨了料床传热模型、自由空间气体传热模型、窑壁传热模型以及全炉整体模型。其中根据需要提到了料床运动状态的研究,料床混合状况的影响,以及料床运动模型的建立等。此外,对相关文献中提及到的动态模型、燃烧模型以及煅烧化学反应模型等也进行了系统综述,在此基础上对回转窑内流动传热和燃烧过程数学模型的发展趋势进行了展望。     

膏体充填管道输送数值模拟与分析

首先介绍了膏体充填技术的基本情况,接着提出了FLOTRAN CFD（计算流体动力学）的基本分析过程,在建立管道几何模型和提出膏体充填管道输送的基本假设的基础上,运用ANSYS软件中的FLOTRAN CFD模块进行模拟分析.通过改变荷载或参数,对FLOTRAN CFD进行重启动,得出一系列结果,符合科学基本规律,说明了该方法的科学性和有效性.     

煤矿乏风瓦斯热逆流氧化反应器的数学模型和试验

建立了低浓度甲烷热氧化逆流反应器的数学模型,运用计算流体力学方法进行数值计算,得到各种操作参数下的温度分布及甲烷浓度分布曲线,并将数值计算结果与实验结果进行了对比,并对影响氧化床运行特性的几个主要因素进行了分析。结果表明,氧化床内温度分布基本成M型,高温区以及甲烷浓度分布曲线沿气体流动方向周期性往复移动;进口甲烷混合气的浓度越大,温度分布峰值就越高并而且更靠近进口端,高温区域的宽度也增宽,而且高温区域中间凹度加深,进出口温度梯度也会增大;预混甲烷气体的流速从0.15 m/s增大到0.70 m/s时,最高温度峰值和高温区变化不大,因为流速增大一方面使单位时间进入氧化床内反应物的数量增加,放出了更多的热量,但是另一方面气体流速升高而带走的对流换热量也会大量增加。     

铁矿粉流态化还原过程黏结机理分析

为探究常压下铁矿粉颗粒在流化床中进行还原时的颗粒间黏结失流情况,指导用流化床还原铁矿粉的工业化应用,以澳大利亚某铁品位为61.42%、颗粒粒径为0.63~1.0 mm的铁矿粉为原料,添加与铁矿粉质量比为2%的MgO粉末,在还原温度为923～1 023 K、H²与CO体积比为4∶1的混合气体为还原气体、还原气体线速度为0.6 m/s、还原时间为60 min条件下,考察铁矿颗粒在流化床中还原时的受力情况。结果表明：颗粒在流化床中的存在状态主要受气体对颗粒的曳力、颗粒间的黏结力以及颗粒自身重力作用的影响。颗粒在竖直方向上所受向上的合外力大于零时,处于流化状态;合外力等于零时,铁矿粉处于临界黏结状态;合外力小于零时,处于黏结失流状态。温度相同时,颗粒间黏结力随着固体桥半径增大而增大;当固体桥半径相同时,高温条件下颗粒间的黏结力比低温条件下要大,黏结失流的临界固体桥半径范围为82~106 nm。     

Computational modeling of reactive multi-phase flows in porous media: Applications to metals extraction and environmental recovery processes

A computational modeling framework is described for the analysis of multi-phase flows in reactive porous media targeted at the metals recovery through stockpile leaching and in environmental recovery processes. These systems involve a complex suite of interacting fluid, thermal and chemical reaction physics in complex geometries, which in the case of heap leaching actually grow with time, and varying environmental conditions. The computational models of such processes need to account for variably saturated liquid flow in porous media, gas flow through porous media, together with the transport of many species in one of these fluid phases plus multi-phase heat transfer and mass transfer arising from a range of phase change and gas–liquid–solid chemical reaction processes. This contribution describes just such a development of a three dimensional modeling framework which is applied to the heap leaching of gold, silver and copper in a variety of contexts.     

基于CFD的反循环钻头内喷孔直径参数研究

孔底流场是反循环钻井取样的关键流场,主要由内喷孔、底喷孔和中心通道形成。为提高反循环取样能力,增强反循环效果,对交汇型和螺旋型内喷孔直径参数开展研究。借助计算流体动力学软件CFD,模拟内喷孔产生的压力场和速度场,引入内喷孔抽吸系数比较进口和出口的质量流量,探讨内喷孔直径变化对增强反循环效果的影响。研究结果表明：交汇型内喷孔产生的流场受直径参数影响较大,螺旋型内喷孔产生的流场受直径参数影响较小;相同直径条件下交汇型内喷孔压力变化范围高于螺旋型内喷孔压力变化范围;随直径增大,交汇型和螺旋型内喷孔抽吸能力均升高,但是交汇型内喷孔抽吸能力随直径变化幅度更大。     

Applicability of a coarse-grained CFD–DEM model on dense medium cyclone

The combined computational fluid dynamics and discrete element method (CFD–DEM) approach has been proved to be an effective tool to study the fundamentals of different particle–fluid flow systems, but suffers high computational cost problem. Recently, various treatments such as parcel–particle concept, coarse-grained model, similar particle assembly and representative particle model have been developed to reduce the computational cost of CFD–DEM approaches. These treatments are basically empirical and thus their applicability is likely system-dependent. Until now, there are still no general agreements on the formulation of those models and their accuracy and general applicability are largely unknown.In this work, a coarse-grained (CG) (CFD–DEM) model is developed to model the swirling multiphase flow in a dense medium cyclone (DMC) and the error caused by the CG concept is quantified by carrying out controlled numerical calculations to directly compare the simulated results between a standard CFD–DEM model and a CG CFD–DEM model. It demonstrates that when the flow is dilute, the results are independent on the size of the grain (also called as parcel or model particle in this work). Nonetheless, when the flow is dense, small discrepancies are observed between the two models. This work suggests that the CG CFD–DEM model is indeed a useful tool to quickly evaluate the flow and performance of large-scale DMCs and the simulation results should be useful at least qualitatively, if not quantitatively.     

三产品重介旋流器分选锰矿石模拟与试验研究

针对-8 mm+1 mm锰矿石分选工艺及设备不尽完善导致的分选困难等问题,提出了三产品重介旋流器分选回收精矿工艺。采用计算流体动力学软件对三产品重介旋流器内部流场及分离性能进行了数值模拟和 试验研究。模拟结果表明：在一定的入口速度区间内,三产品重介旋流器的流场比较稳定,切向速度和轴向速度均随着入口速度的增大而增大,所以适当增大入口速度,有利于锰矿石的分选。通过预测重介质悬浮液 密度场分布,获取了旋流场流动特征,为流场结构优化提供了理论依据。分选试验结果表明：采用无压给料重介质三产品旋流选矿工艺可以实现精矿与脉石的有效分选,分选效率显著提高。二段旋流器悬浮液密度为 2.6 g/cm3、压力为0.08 MPa时,精矿产率为36.00%。Mn在原矿中的品位为28.25%,分选后所得精矿中Mn品位达44.58%,回收率高达56.81%。本工艺较好地实现了难分选锰矿石的有效回收。 关键词 锰矿分选|三产品重介旋流器|数值模拟     

Study on flow mode of combined converter for methanol synthesis from coal-based syngas

The mathematic model of combined converter with two different flow modes of gas-cooled reactor was established. The effects of gas flow mode in gas-cooled reactor on combined converter was investigated with the yield of methanol was 1 400 kt/a. The results show that if the flow mode of the cooling pipe gas and the catalytic bed gas change from countercurrent to concurrent, the catalytic bed temperature distribution does not fit the most optimum temperature curve of reversible exothermic reaction and the heat duty of heat changer in whole process increased seriously, which means that there is much more equipment investment and more operating cost. The gas flow mode of gas-cooled reactor affects the methanol yield slightly. Therefore, the countercurrent gas flow mode of gas-cooled reactor is more lucrative in the combined converter process.     

Numerical simulation on turbulent flow field in convergent-divergent nozzle

Because of the complication of turbulence’s mechanism and law as well as the jet pressure in nozzle is difficult to test by experiment, five turbulent models were applied to numerically simulate the turbulent flow field in convergent-divergent nozzle. Theory analysis and experiment results of mass flow rates conclude that the RNG k-ɛ model is the most suitable model. The pressure distribution in the convergent-divergent nozzle was revealed by computational fluid dynamic (CFD) simulating on the turbulent flow field under different pressure conditions. The growing conditions of cavitation bubbles were shown; meanwhile, the phenomena in the experiment could be explained. The differential pressure between the upstream and downstream in nozzle throat section can improve the cavitating effect of cavitation water jet.     

我国煤层气开发的合理生产规模研究

煤层气是一种新型的洁净能源 ,在煤层气开发利用过程中 ,投资规模的大小直接影响投资效益。因此 ,本文从分析我国煤层气开发利用的投资活动入手 ,通过充分的分析、研究 ,建立了确定我国煤层气开发利用投资的最低生产规模、警惕生产规模、安全生产规模和最佳生产规模的数学模型 ,并进行了实例分析 ,为煤层气开发利用的投资者提供了一种行之有效的定量分析手段     

KYZ-B浮选柱发泡器喷嘴流体动力学数值模拟

从设计角度出发.将计算流体力学(CFD)数值模拟软件CFX应用于KYZ-B型浮选柱发泡器喷嘴流体动力学的研究.对喷嘴内气体流动状态进行了数值模拟.通过分析计算结果中流体流动速度场特征,预测出喷嘴内气体超声速流动比低速流动更有利于提高发泡器的充气性能。