AN ANALYSIS ON ENTRANCE REGION EFFECT OF THE LAMINAR RADIAL FLOW BETWEEN TWO PARALLEL DISKS

In this paper, B. B. Golubef method is used for calculating the radial diffuse flow between two parallel disks for the first step. The momentum integral equation together with the energy integral equation is derived from the boundary layer momentum equation and the expression of secondary approximation explicit function in which the channel length of entrance region varies with the boundary layer thickness can be obtained by using Picard iteration in the solution of the energy integral equation. Therefore, this has made it possible to analyze directly and analytically the coefficients of the entrance region effect. In particular, when the outer diameter of disk is smaller than the entrance region length, the advantage of this method can be prominently manifest. Only because the energy integral equation is employed, the terms in the pressure loss coefficient can be independently derived theoretically. The computable value of the pressure loss coefficient presented in this paper is nearer to the testing v     

THE SOLUTION OF LARGE DEFLECTION PROBLEM OF THIN CIRCULAR PLATE BY THE METHOD OF COMPOSITE EXPANSION

In this paper, the method of composite expansion in perturbation theory is used for the solution of large deflection problem of thin circular plate. In this method. the outer field solution and the inner boundary layer solution are combined together to satisfy all the boundary conditions. In this paper, Hencky's membrane solution is used for the first approximation in outer field solution, and then the second approximate solution is obtained. The inner boundary layer solution is found on the bases of boundary layer coondinate. In this paper, the reciprocal ratio of maximum deflection and thickness of the plate is used as the small parameter. The results of this paper improves quite a bit in comparison with the results obtained in 1948 by Chien Wei-zang.     

THE METHOD OF TRANSFORMATION OF THE BOUNDARIES FOR STRUCTURE THE ADMISSIBLE DISPLACEMENTS

In this paper the method of transformation of the boundaries for structure theadmissible displacements with various boundary conditions is presented What is called themethod of transformation of the boundaries is that. first we transform the actual systeminto the basic system and additional boundary forces and displacements on the basis of thesuperposition principle, then apply variational principles to the basic system,finally find thepermissible displacement of the actual system by means of the method of transformation ofthe series.In this paper, we also give mixed energy prinapies under Variation of boundaryconditions. The mixed energy principles as the potential and complementary energyprinciples under variation of boundary conditions are all the chief theoretical fundamentalof the method of transformation of the boundaries.Applying the method of transformation of the boundaries. we form the permissibledisplacements of rectangular plates of plane stress and bending problems with various edgeconditio     

Modeling coal pyrolysis in a cocurrent downer reactor

In this paper,a model for fast coal pyrolysis in a cocurrent downer reactor is developed,in which both hydrodynamics and coal pyrolysis kinetics are simultaneously considered.The results of simulations based on this model display reasonable agreement with experimental data obtained using Huolinhe coal as the feedstock,and this model is therefore suitable for predicting the fast pyrolysis of specific coal types.A series of simulations of fast coal pyrolysis in a cocurrent downer demonstrated that coal devolatilization is almost complete in the inlet region within a time span of 0.4 s,and that higher temperatures improve the pyrolysis efficiency.However,the yield of liquid products is decreased with increasing pyrolysis temperatures,especially above 670 ℃,because of additional cracking of the liquids.     

Sino-German Workshop on Energy Utilization of Biomass

Need for Energy Utilization of Biomass in China China is on the way to be the most important energy market of the world. Economic growth and improvement in peo-ple抯 livelihood are leading to enormous increases in energy consumption. In view of the mainly coal dominated structure of the energy supply in China, however, this growth not only leads to increasing pressure on the available resources, but also possesses long-range effects on matters of the environment. At present, the national en…     

THE BENDING, STABILITY AND VIBRATIONS OF RECTANGULAR PLATES WITH FREE EDGES ON ELASTIC FOUNDATIONS

This paper discusses the problems of the bending, stabilio, and vibrations of the rectangular plates with free boundaries on elastic foundations, In the present paper we select a flexural function, which satisfies not only all the boundary Conditions of free edges but also the conditions at free corner points, and consequently we obtain a better approximate solution. The energy method is used in this paper.     

THE STRAIN ENERGY CRITERION OF MIXED-MODE BRITTLE FRACTURE

In this paper, we proposed a new criterion of mixed-mode brittle fracture, i.e., the strain energy criterion, which can be stated as This criterion is shown to be in good agreement with known experimental data. In this paper, an experimental criterion: is also proposed.     

NUMERICAL SOLUTION OF THE SINGULARLY PERTURBED PROBLEM FOR THE HYPERBOLIC EQUATION WITH INITIAL JUMP

In this paper we consider the initial-boundary value problem for a second orderhyperbolic equation with initial jump.The bounds on the derivatives of the exact solutionare given.Then a difference scheme is constructed on a non-uniform grid.Finally,uniformconvergence of the difference solution is proved in the sense of the discrete energy norm.     

THE EXPRESSION OF FREE ENERGY FOR THERMOELASTIC MATERIAL AND ITS RELATION TO THE VARIABLE MATERIAL COEFFICIENTS

The expression of free energy is expanded in a power series, in which there aren't any terms of order higher than third in the temperature increments θ~* and second in the strains γ_(ij) in this paper. The regular patterns of the material coefficients changing with temperature increments can be derived from this expression, These regulations accord with the experimental graph in references but the constants in the expression of free energy must be determined by experimental data. It is pointed out that the variable modulus of elasticity E and shearing modulus of elasticity G are independent of each other, but the rest of the coefficients are related to them.     

THE CREEPING MOTION OF MULTIPLE SPHERICAL LIQUID DROPS

This paper deals with the drag factor of the multiple spherical liquid drops in thecreeping motion by means of the Sampson singularities and collocation technique.The dragfactors of the drops are calculated under distinct conditions:different number of liquiddrops in the chain and different sphere spacing.From the results the influence of theviscosity ratio on the shieding effect and end effect are revealed.The convergence of themethod is also studied in this paper.In this paper the collocation technique developed by Gluckman etal.in treatingthe rigid sphere case is applied to deal with the creeping motion of multiplespherical liquid drops which has important applications in bioengineering andchemical engineering.Writing the general solutions in inner and outer regions ofthe spheres and satisfying the kinematic and dynamic matching conditions at thecollocation points on the interfaces,a set of linear algebraic equations is obtainedto determine the unknown coefficients in the solutions.By means of any ma     

钻井式煤炭地下气化技术的发展及关键力学问题

煤炭地下气化技术是有希望解决我国能源危机的重要手段之一,是煤炭资源高效清洁利用的有效手段之一,是拓展天然气资源实现战略资源接替的有效方法之一.本文通过调研国内外煤炭地下气化技术,将煤炭地下气化技术分为两类,即钻井式技术和巷道式技术,并重点叙述了钻井式煤炭地下气化技术开发模式.钻井式煤炭地下气化技术的发展可分为4个阶段:...     

瓦斯爆炸载荷作用下矿用柱壳救生舱抗爆性分析及结构优化

矿用救生舱是矿井安全生产中必备的救生装备,其稳定性和抗爆性能决定着逃生人员的生存概率。本文中设计了一种圆柱壳结构救生舱,优化了该救生舱在瓦斯爆炸载荷作用下的抗爆性能:首先,采用ANSYS/LS DYNA软件模拟并验证了爆炸流场载荷;其次,采用ALE流固耦合算法揭示了真实环境下爆炸流场与救生舱的耦合作用;然后,对其进行抗爆性模拟分析及结构设计优化;最后,对比分析了原模型和优化模型的动力响应、强度及能量变化特征,结果表明优化后的救生舱抗爆性满足国家规范要求。     

基于仪器化压入实验的煤体微纳尺度非均质力学响应特征

煤炭是我国的主体能源,煤矿井下冲击地压、煤与瓦斯突出等灾害的频繁严重影响煤炭的安全生产.煤体是典型的混合物,其内部不同组分的力学性质差异较大,使其在外部扰动的作用下容易产生内部应力集中,导致煤体的失稳、破坏,形成煤矿动力灾害.本文以非均质煤体为研究对象,利用微焦CT、扫描电子显微镜和纳-微米压入实验,研究了煤体微纳尺度的非均质结构和力学性质,实验研究结果表明:煤体是有机物和多种矿物组成的混合物,矿物以点填充、丝状填充和条带状侵入等结构存在于煤体有机物中,不同的矿物填充或侵入区域中矿物含量和结构具有差异,这导致煤体微纳尺度的物理力学性质具有非均质性;纳米尺度压入实验可以捕捉矿物在有机物中的填充或侵入结构,测量煤体混合物中矿物和有机物单组分的力学参数,识别两者力学性质的巨大差异;微米尺度的压入实验可以表征煤体混合物整体的力学性质,矿物填充量越多,煤体混合物的力学性质越强,同时煤体混合物微观尺度的破裂模式会受到矿物填充结构的影响.研究结果揭示了煤体微观结构和力学性质的非均质特征,探讨了煤体混合物的非均质结构可能引起的脆性破坏,为煤矿井下冲击地压和煤与瓦斯突出等动力灾害的预测与防治提供了理论基...     

煤层节理及其工程地质意义

煤层节理在煤层中普遍发育, 它不仅是矿井构造研究的重要内容, 同时也是极其重要的工程地质因素。煤层节理影响煤层的结构构造和物性特征, 从而影响煤层采落特征、顶板工程性质、瓦斯运移规律和煤层气储运采工程地质条件。研究掌握煤层节理几何和力学特征, 可指导井巷工程布置、采掘工艺的选择、安全措施的采用和煤层气开发方案的制定。     

Mathematical modeling of methane flow in a borehole coal mining system

Safety in coal mining is greatly increased by the drainage of the methane content of coal seams through boreholes, simultaneously producing significant energy. The design of suitable drainage technology is based on the mathematical modeling of methane flow in coal seams. In the calculation of the methane pressure, the new mathematical model presented in this paper considers both the sorption phenomenon of methane depending upon the methane pressure and the fact that the variation in methane pressure can create a change in the stress condition of the rock and, as a consequence of this, a change in the permeability of the coal. The new mathematical model can be used for the numerical simulation of the flow processes in coal seams and methane drainage technology can be designed more accurately.     

Tandem fluidized bed elutriator—Pneumatic classification of coal particles in a fluidized conveyer

Coal moisture control (CMC) in coking process, which reduces coal moisture before loading the coal into the coke oven, allows substantial reduction in coking energy consumption and increase in coke productivity. The technology is seeking to integrate the coal classification, thus calling it the coal classifying moisture control (CCMC), to separate the fine and coarse coal fractions in the CMC process so that the downstream coal crushing can only treat the coarse fraction. CCMC adopts a reactor that integrates a fluidized bottom section and a pneumatic conveying top section. The present work investigates the pneumatic classification behavior in a laboratory CCMC reactor with such a configuration by removing the coal fraction below a given size (e.g., 3.0 mm) from a 0 to 20.0 mm coal feed. The results show that the coal classification were dominated by the gas velocity in the top conveying section, and the required gas velocity for ensuring the maximal degree of removing a fine coal fraction could be roughly predicted by the Richardson and Zaki equation. The effect of bottom fluidization on the performance of CCMC is also examined.     

门帘石及其地质意义

本文以大同煤田区域地质构造特征为基础, 对门帘石的定义、岩性特征、形态与产状、分布和成因进行了分析研究, 指出其与井田发育的准同生岩溶陷落柱具有成生联系。因此, 门帘石的存在具有重要的地质与生产意义。     

峰后岩石非Darcy渗流的一维非定常严格简明解析解

煤炭是中国近期的主要能源,仍需要大力研究. 而煤矿采动围岩大多处于峰后应力状态或破碎状态,其渗流一般不符合Darcy定律. 探讨非Darcy渗流系统, 对其研究既有理论创新价值,尤其在煤矿安全中更有重要的实用价值. 用近年发展的求解偏微分方程新的分离变量法------加法分离变量法,得出了Ahmed-Sunada型非Darcy渗流的3套非常简明的一维非定常严格解析解,以发展相应的渗流理论,以及作为标准解推进渗流数值计算的水平.      

深井提升动力学研究

随着浅部煤炭资源的日益枯竭, 我国煤炭开采朝着深部化和大型化方向发展, 新建和改扩建的大型立井年生产能力已达1000万吨, 开采最大深度已达1500 m. 千米深井在提升过程中, 造成提升钢丝绳、容器振荡, 特别是自由悬挂平衡尾绳大幅度摆动, 严重影响多绳摩擦提升系统向高速度、深度化发展. 在国家重点研发计划“深地资源勘查开采”重点专项“煤矿深井建设与提升基础理论及关键技术”支持下, 建立了单元数量自动调整的自由悬挂平衡尾绳提升系统动力学模型, 揭示了传统提升系统诱发平衡尾绳大摆动的机理; 提出了深井SAP提升新模式, 构建了多元耦合下的SAP提升系统动力学模型与非光滑动力学模型, 揭示了多参数影响下系统的非光滑动力学特性及非线性振动演化规律; 研发了适用于深部提升的SAP提升技术与装备, 开展了SAP提升技术与装备的现场研究, 解决了大强煤矿立井提升系统运行过程中尾绳大摆动、提升容器大振动等关键问题, 提高了提升系统高速运行的安全性, 消除了尾绳大摆动难控制的问题.      

Nano-scale pore distribution characterisation of coal using small angle X-ray scattering

In the process of coal seam fracturing with liquid nitrogen (LN₂), the change of coal pore structure has an important influence on the efficiency of coalbed methane (CBM) extraction. The nano-scale pore size distribution (PSD) in coal particles before and after freezing with LN₂ are experimentally studied in this work. Coal samples are collected from four coal mines, where coal and gas outburst accidents have occurred. Small angle X-ray scattering technology (SAXS) and scanning electron microscopy (SEM) are used to study the pore structure changes of coal samples quantitatively and qualitatively. It is found that the scattering intensity of coal samples increases after freezing. The PSD of all samples significantly changes in the range of 0.8–7 nm, showing new pore spaces in 0.8–4 nm and fewer pores in the 4–7 nm range. Both the pore fractal dimension and the radius of gyration of coal samples increase after freezing and are mainly affected by the changes in pores and the anisotropy of the coal matrix. Crack expansion and pore connections are observed in the surface structure of the coal sample using SEM. This study provides a better understanding of the nano-scale mechanism of coal seam fracturing with LN₂ for the prevention of coal and gas outbursts.