阶梯溢流坝面坡度对一体化消能工水力特性的影响

为探求高水头、大单宽流量下坝面坡度对一体化消能工水力特性的影响,以阿海水电站为原型,采用三维k-ε双方程紊流模型,引入水气两相流VOF计算方法,利用几何重建格式来迭代生成自由水面,对1∶0.80、1∶0.75、1∶0.65三种阶梯面坡比进行数值模拟研究。结果表明:①最大负压值均位于首级阶梯立面凸角下1/4附近,并随坡度增加而增大。坡度为56.98°时,最大负压值为61.02 kPa,超过了6×9.81 kPa。②水流空化数在宽尾墩水舌出口位置出现最小值,空化数随坡度变陡而减小。坡度为56.98°时,空化数最小为0.358。坡度为51.34°时,空化数最大,为0.381。③随着阶梯溢流坝坝面坡度变缓,消力池最大临底流速增大。当坡度为51.34°时,消力池最大临底流速最大,达到26.84 m/s,超过了25 m/s,易发生冲磨破坏。当坡度为56.98°时,消力池最大临底流速最小,为24.00 m/s。消力池尾坎前最大临底流速随坡度增加而减小,坡度为56.98°时最小,为9.63 m/s;坡度为51.34°时,消力池尾坎前最大临底流速最大,为9.96 m/s。④坡度的变化对一体化消能工消能率的影响不大,坡度从51.34°增加到56.98°,消能率只提升0.15%。     

Heat Transfer Analysis of MHD Power Law Nano Fluid Flow through Annular Sector Duct

Flow and heat transfer analysis of an electrically conducting MHD power law nano fluid is carried out through annular sector duct,under the influence of constant pressure gradient.Two types of nano particles(i.e.Cu and TiO2)are used in power law nano fluid.Strongly implicit procedure,(SIP)is used to simulate the discretized coupled algebraic equations.It has been observed that volume fraction of nano particles,ϕand magnetic field parameter,Ha are favourable for the heat transfer rate,however,both resist the fluid flow.Impact of applied uniform transverse magnetic field exceeds in the case of shear thickening fluids(i.e.n>1)by increasing the value of Ha as compared to that in shear thinning fluids(i.e.n<1).Therefore,enhancement in heat transfer rate is comparably more in shear thickening fluid.Furthermore,comparable limiting case study with published result is also carried out in this research paper.     

Flame Front Deformation Instabilities of Filtration Combustion for Initial Thermal Perturbation

The flame front deformation instability of low-velocity filtration combustion within an inert packed bed is studied based on the initial preheating non-uniformity. Based on the experimental phenomena, an initial thermal perturbation model is numerically proposed so as to predict the deformation behaviors of the flame front instabilities. The numerical prediction indicates that the assumption of an initial thermal perturbation is a feasible explanation as the cause of the flame front inclination instability. As the initial thermal perturbation increases, the phenomena of the flame front break and shrinking instabilities could easily occur at high filtration velocity or low equivalence ratio. Moreover, the evolutions of the flame front break rate and the shrinking rate are quantitatively analyzed.     

影响干式磁选机在石英除铁过程中的因素研究

本文通过对陕西某地石英矿进行干式磁选试验研究,介绍了给料速度、尾矿抛尾率、矿样含水率及含泥量等几个因素对干式磁选作用的影响,分析了干式磁选各因素在石英除铁过程中的规律,为后续工业应用提供一定的理论基础。     

不同镀层结构钢的耐盐雾腐蚀性能比较

通过盐雾试验模拟潮湿环境,对裸钢试片、电镀锌钢试片、化学镀镍-磷钢试片和化学镀镍-钴-磷钢试片进行了宏观形貌、微观形貌和腐蚀产物成分分析,比较了四个试片的耐盐雾腐蚀性能。结果表明:在盐雾环境中,四个试片均会发生电化学腐蚀,生成不同的腐蚀产物;在盐雾腐蚀周期内,裸钢试片的腐蚀速率最高,化学镀镍-磷钢试片和化学镀镍-钴-磷钢试片的腐蚀速率较低;四个试片在腐蚀过程中的阳极反应和阴极反应不同,腐蚀后的微观形貌存在明显差异。     

New observations and critical assessments of incipient plasticity events and indentation size effect in nanoindentation of ceramic nanocomposites

The ceramic nanocomposites (CNCs) like zirconia toughened alumina (ZTA) ceramics are important futuristic materials for structural and functional applications in advanced strategic systems, structural components, biomedical prostheses and devices. In all structural materials including the ZTA CNCs, the very early stages of plastic deformation i.e., the incipient plasticity events (IPE) are most important to be understood so that the microstructure and mechanical properties can be tuned to suit a given end application. Here we report for the first time the mechanisms of IPE in the nanoindentation experiments conducted at 10–1000 mN loads in the 40 ZTA CNCs. Here 40 ZTA CNC stands for 40 vol% of 3 mol% Yttria partially stabilized zirconia toughened alumina (40ZTA) CNC. The role of load ranges in variations of the IPE related parameters in the 40 ZTA CNCs is also studied. Further, an attempt is made to assess how the amount of zirconia content in ZTA CNCs affects the variations of the IPE related parameters. Through the extensive usage of field emission scanning electron microscopy (FESEM) and theoretical estimations, efforts are also directed to check out the linkage, if any, between the localized shear deformation and/or microcracking with the IPE events that occur in the present CNCs. In addition, a new concept of damage resistance is introduced for the first time in the present work to explain the presence of a strong indentation size effect (ISE) in the 40 ZTA CNCs. Finally, an attempt is also directed to understand how the indentation load (P) controls the relative size of interaction zones of dislocation loops as well as the damage resistance and thereby, engineer the acuteness of the ISE in ZTA CNCs. The implication of these findings in futuristic design of especially the ZTA CNCs for various applications is also discussed.     

Size-dependent separation of graphene oxide by deformation of packed-gel in a chromatographic column

ABSTRACT

A deformable gel-packed chromatographic column was used to separate as-synthesized graphite oxide with different sizes. The synthesized gel (56 µm) was deformed by pressure of the fluid flow and the gaps in the gels showed a range of sizes. A suspension of graphene oxide (0.1 g/L, 10 mL) was injected, and graphene oxide in the elution had a size at 0.56 μm and 0.14 μm, whereas in half upper and bottom domain of the gel layer graphene oxide had a size at 33 µm and 2.9 µm, respectively, demonstrating that graphene oxide suspension was separated by size through gel layer.     

高固气比技术在2 500 t/d水泥熟料线的改造案例介绍*

采用高固气比悬浮预热分解技术对宝江2 500 t/d生产线烧成系统进行技改后,预热系统出口温度从351℃降低至279℃,粉尘浓度(标况下,以下同)从151.6 g/m3减少至43.9 g/m3,系统分离效率大幅提高;入窑生料分解率从90.5%提高至98%,生产线熟料烧成煤耗从119.4kg/t降低至100.80kg/t,熟料产量从2744t/d提高至3840t/d,各指标均属领先水平。     

Comparison study of thermochemical waste-heat recuperation by steam reforming of liquid biofuels

The concept of thermochemical exhaust heat recuperation by steam reforming of biofuels is considered. Thermochemical recuperation can be considered as an on-board hydrogen production technology. A schematic diagram of a fuel-consuming equipment with thermochemical heat recuperation is described. The thermodynamic analysis of the thermochemical recuperation systems was performed to determine the efficiency of using various fuels, in particular, methanol, ethanol, n-butanol, and glycerol. The thermodynamic analysis was performed by Gibbs free energy minimization method and implemented using the Aspen Hysys program. The thermodynamic analysis was performed for a wide temperature range from 400 to 900 K, for steam-to-fuel of 1, and pressures of 1 bar. The maximum fuel conversion reaches for the following temperatures: methanol - 600 K, ethanol - 730 K, n-butanol - 860 K, glycerol - 890 K. The dependence of the reforming enthalpy on temperature is determined. It was shown that the reaction enthalpy determines the heat transformation coefficient, which shows the ratio of the low heat value of synthetic fuel and the low heat value of the initial fuel. For all studied fuels, the maximum value of the transformation coefficient is observed for steam reforming of ethanol and the maximum heat transformation coefficient is 1.187. The temperature range is determined at which the maximum efficiency of the use of thermochemical recuperation occurs due to the reforming of biofuels. For methanol, the effective temperature is about 600 K, for ethanol is about 700 K, for n-butanol is 850 K, for glycerol is more than 900 K. The results obtained make it possible to efficiently select the type of fuel for thermochemical recuperation due to steam reforming.     

福建某低品位金矿新型浸金剂浸金试验

福建某斑岩型金矿品位低、规模大,金主要以自然金形式存在,可见金的粒度较粗,为高效利用该低品位金矿,开展新型浸金剂金蝉全泥浸出试验和柱浸试验,结果表明：全泥浸出在磨矿细度为-0.074 mm占80%、矿浆浓度25%、加石灰调pH 值11.0左右、初始金蝉浓度为500 mg/L和过程中控制金蝉浓度不小于300 mg/L条件下浸出20 h,金的浸出率为93.43%,金蝉耗量为1.02 kg/t；柱浸在矿石粒度为-30 mm条件下喷淋浸出23天,金累计浸出率和金蝉累计耗量分别为86.54%和1.22 kg/t。