在重点瓦斯采面应用高位钻孔抽放瓦斯

采用高位钻孔抽放瓦斯技术,可有效预防采面及上隅角瓦斯超限现象发生、确保重点瓦斯采面安全生产。     

煤矿湿润剂抑尘影响因素分析

通过室内实验选取了非离子型湿润剂和阴离子湿润剂进行复配,针对不同的变质程度煤样与除尘效率,湿润剂水溶液浓度与湿润时间的关系进行研究。实验表明非离子型湿润剂、阴离子湿润剂水溶液浓度为20%～40%最佳;同一种湿润剂随着煤的变质程度增加,非离子型湿润剂和阴离子湿润剂除尘效果越来越差。     

沸石抗菌剂的研究现状与展望

介绍了目前国内外沸石抗菌剂的研究现状,重点讨论了沸石抗菌剂的原料改性、抗菌机理、持久性、变色抑制性、结构化等方面的特点,简述了沸石抗菌剂在日常生活中的应用,并对沸石抗菌剂的发展方向进行了展望.     

Generation of hydrogen from aluminum and water - Effect of metal oxide nanocrystals and water quality

Metal Oxides nanocrystals such as TiO₂, Co₃O₄, Cr₂O₃, Fe₂O_3, Mn₂O₃, NiO, CuO and ZnO were used as modifiers on the metallic aluminum (Al) powders for the production of hydrogen in deionized water or tap water at room temperature. In particular, the influences of TiO₂ nanocrystals with various crystal sizes on the production of hydrogen from the reaction in tap water under ambient condition were investigated in details. It was found that hydrogen was barely generated from metal Al powders in tap water at 25-45 °C but significantly produced in deionized water above 35 °C without any modifiers. TiO₂, Co₃O₄, and Cr₂O₃ nanocrystals were very effective to promote hydrogen generation from the reaction of Al and deionized water at 25 °C. In addition, while other oxide nanocrystals were ineffective to promote hydrogen generation in tap water, TiO₂ nanocrystals (P90, ∼14 nm in diameter) were found to be highly effective in facilitating the production of hydrogen from the reaction of Al with tap water, comparable to the well-known γ-Al₂O₃. The production of hydrogen over time was found to be dependent on the passive layer of metal Al, where Al(OH)₃ plays an important role during reaction. Pitting is proposed as the major mechanism behind the production of hydrogen in the nanocrystals TiO₂ (P90)-modified Al/tap water system, which is thought to be originated from point defects, and differ considerably from the uniform corrosion model.     

Mixed convective peristaltic flow of Eyring‐Prandtl fluid with chemical reaction and variable electrical conductivity in a tapered asymmetric channel

The influence of inconstant electrical conductivity and chemical reaction on the peristaltic motion of non‐Newtonian Eyring‐Prandtl fluid inside a tapered asymmetric channel is investigated. The system is concerned by a uniform external magnetic field. The heat and mass transfer are considered. The problem is controlled mathematically by a system of nonlinear partial differential equations which describe the velocity, temperature, and nanoparticle concentration of the fluid. By means of long wavelength and low Reynolds numbers, our system is simplified. It is explained by using the multi‐step differential transform method as a semi‐analytical technique. The distributions of velocity, temperature, nanoparticle concentration, as well as pressure gradient and pressure rise are obtained as a function of the physical parameters of the problem. The effects of these parameters on these distributions are deliberated numerically and illustrated graphically through a set of figures. The results indicate that the parameters play a significant role in controlling the velocity, temperature, nanoparticle concentration, pressure gradient, and pressure rise.     

上进风燃气灶引射性能的数值模拟

利用CFD软件对上进风燃气灶进行三维稳态流动模拟,与实测的气相色谱分析数据进行了对比,验证了数值模拟来分析引射能力的可行性。对模拟得到的速度场、温度场进行了分析,为今后的设计改进提供了依据;将CFD技术用于燃烧器设计,可缩短新产品的开发周期、降低开发成本,实现燃气具开发、设计的自主创新。     

Transient response of high temperature PEM fuel cell

A transient three-dimensional, single-phase and non-isothermal numerical model of polymer electrolyte membrane (PEM) fuel cell with high operating temperature has been developed and implemented in computational fluid dynamic (CFD) code. The model accounts for transient convective and diffusive transport, and allows prediction of species concentration. Electrochemical charge double-layer effect is considered. Heat generation according to electrochemical reaction and ohmic loss are involved. Water transportation across membrane is ignored due to low water electro-osmosis drag force of polymer polybenzimidazole (PBI) membrane. The prediction shows transient in current density which overshoots (undershoots) the stabilized state value when cell voltage is abruptly decreased (increased). The result shows that the peak of overshoot (undershoot) is related with cathode air stoichiometric mass flow rate instead of anode hydrogen stoichiometric mass flow rate. Current is moved smoothly and there are no overshoot or undershoot with the influence of charge double-layer effect. The maximum temperature is located in cathode catalyst layer and both fuel cell average temperature and temperature deviation are increased with increasing of current load.     

Onset of Darcy‐Brinkman Convection in a Binary Viscoelastic Fluid‐Saturated Porous Layer with Internal Heat Source

The onset of Darcy‐Brinkman convection in a binary viscoelastic fluid‐saturated sparsely packed porous layer with an internal heat source is studied using both linear and nonlinear stability analyses. The Oldroyd‐B model is employed to describe the rheological behavior of binary fluid. An extended form of the Darcy‐Oldroyd law incorporating Brinkman's correction and time derivative is used to describe the flow through a porous layer. The onset criterion for stationary, oscillatory, and finite amplitude convection is derived analytically. There is a competition between the processes of thermal diffusion, solute diffusion, and viscoelasticity that causes the convection to set in through an oscillatory mode rather than a stationary mode. The effect of internal Rayleigh number, relaxation and retardation parameters, solute Rayleigh number, Darcy number, Darcy‐Prandtl number, and Lewis number on the stability of a system is investigated and is shown graphically. The nonlinear theory based on the truncated representation of the Fourier series method is used to find heat and mass transfer. The transient behavior of the Nusselt and Sherwood numbers is obtained using numerical methods. Some known results are recovered for the particular cases of the present study. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 42(8): 676–703, 2013; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21056     

两性聚合物钻井液降粘剂GCH—11的制备及评价

以烯类单体为主要原料,水溶液聚合物方法,合成了新型两性离子聚合物钻井液体降粘剂ＧＣＨ－１１。考察了ＧＣＨ－１１在不同钻井液体系的降粘效果和抗盐性能。结果表明,ＧＣＨ－１１在膨润土钻井液、聚合物钻井液及高密度聚合物钻井液中的降粘效果优于ＧＤ－１８和ＸＹ－２７,是高密度聚合物钻井液的理想降粘剂。     

Droplet–Droplet Interactions in Spray Drying by Using 2D Computational Fluid Dynamics

A 2D axisymmetric model of the spray drying process is presented. The two-phase flow theoretical model is based on a combined Eulerian-Lagrangian approach and takes binary interactions (coalescence or bouncing) between spray droplets into consideration. Validation of the model (incorporated in FLUENT 6.3.26) demonstrated good agreement and consistency with the literature data. The results of transient simulations showed that droplet–droplet interactions displace the region of heat and mass transfer from the central core toward the periphery of the drying chamber. It was also found that insulation of the spray dryer can substantially affect temperature and humidity patterns, whereas its influence on the velocity flow field is less marked.