LSM粉末设计及其对SOFC阴极性能的影响

采用大气等离子喷涂在粒子完全熔化条件下制备的Sr掺杂LaMnO3(LSM)阴极由于三相反应界面和贯通孔隙数量不足,其阴极阻抗较大.针对这一问题,通过在LSM微粉中加入20％(体积分数)亚微米石墨经团聚造粒获得LSM/石墨复合粉末,采用大气等离子喷涂在不同功率下制备了LSM阴极,采用扫描电子显微镜法(SEM)、能量散射光...     

Effect of ambient relative humidity and surface modification on the charge decay properties of polymer powders in powder coating

Back corona on a powder layer deposited via the electrostatic powder-coating process using corona guns has a strong influence on the corrosion resistance and appearance of cured powder films. The presence of the back corona is often evidenced by orange peel, micro-dents, and pinholes on the film surface. The surface resistivity of the sprayed powder governs the charge decay process and, hence, the onset of back corona. The polymer powders used in powder coating are highly resistive, with surface resistivity often greater than 10/sup 15/ /spl Omega///spl square/. Surface resistivity can be altered by the adsorption of moisture on the surfaces of the powder particles. The objectives of this research were: (1) investigate the effect of decreasing surface resistivity on the appearance of the powder-coated film and (2) enhance hydrophilic properties of polymer powder by plasma treatment. By changing the relative humidity (RH) of powder during the spraying process, it was observed that the surface resistivity could be lowered by orders of magnitude. For example, the surface resistivity for an acrylic powder decreased from 2.96/spl times/10/sup 13/ /spl Omega///spl square/ at 25% RH to 9.6/spl times/10/sup 11/ /spl Omega///spl square/ at 70% RH. The plasma treatment of this powder further improved its charge decay properties. The effects of variation of RH on the appearance of powder-coated panels surface layer are presented for an acrylic polymer powder. The film texture has been characterized by microstructural surface analysis using an optical scanning instrument. Methods of plasma and corona treatments of the powder for increasing moisture adsorption on the surface and decreasing surface resistivity are discussed along with analysis of surface morphology using the atomic force microscope.     

Dielectric recovery of a residual SF6 plasma between twoparallel plane electrodes

The present work is a theoretical investigation into the dielectric strength of a thin column of hot SF₆ gas left between two contacts after the thermal quenching of an arc at current zero in a modern HV gas-blast circuit breaker. Because of time rapid decay of arc temperature during current zero, this hot gas is still in a plasma state (referred to as the residual plasma) with sufficiently high charge density (both electrons and ions) although electrical conductivity is low. The dielectric recovery of such a residual plasma differs from that of an infinitely large, uniform plasma in two aspects. Firstly, the presence of space charge can distort severely the local electric field and can influence strongly the generation and loss of charged particles by ionization and chemical reactions. Secondly, due to the finite size of the plasma column, electrons diffuse in an ambipolar manner, thus enhancing the loss of charged particles in the plasma. In the present investigation, the gap length between the contacts (electrodes) is 1.0×10^-2 m and the diameter of the plasma column varies between 50×10^-6 and 500×10 ^-6 m. Distribution of the number density of charged species on the axis is obtained by solving their continuity equations using the method of MacCormack with Shuman filter. It is found that formation of space charge creates strong ionization layers close to the electrodes and that the whole column could deviate from electrical neutrality due to the drift of charged particles. The breakdown field of such a bounded plasma at atmospheric pressure or above is approximately equal to the critical field for an infinite plasma within a numerical uncertainty of 5%     

结构尺寸对预膜式雾化喷嘴雾化特性的影响

通过改变预膜式气动雾化喷嘴空气射入角、空气通道直径和环形液膜厚度等关键参数，研究了喷嘴结构参数对雾化特性的影响，得出雾化粒子索太尔平均直径的变化规律，为喷嘴的优化设计提供了依据。     

基于能效的数据包长度自适应算法的研究

随着无线移动网络3G、4G技术的不断发展和普及,利用无线数据传输终端进行数据交互已经成为信息化发展的重要环节.数据传输终端通信模块消耗的能量是终端各模块消耗的总能量的主要部分,而数据包长度作为通信的主要参数直接影响了终端能耗.在公网条件下,针对节省数据传输终端能耗,延长电池使用寿命的问题,提出了基于SPSA的数据包长度自适应算法ASPSA(adapted simultaneous perturbation stochastic approximation).该算法可根据信道状况,快速计算出该网络状况下最优数据包长,从而保证数据传输终端能耗最低.理论分析及仿真表明ASPSA算法在公网条件下可以有效提高无线数据传输终端的能效.     

中储式热风送粉系统三次风速偏高的试验研究

在鸡西发电厂1号、2号机组调试过程中，发现2号机组制粉系统存在三次风速偏高等问题，经过对原设计制粉系统的热力计算进行重新校核验算，增加了三次风燃烧器喷口的截面积，降低了三次风速，使锅炉的热风温度能够满足制粉系统干燥出力的要求。     

Calculation of transient puffer pressure rise takes mechanical compression, nozzle ablation, and arc energy into consideration

Thermal puffer-type gas circuit breaker (GCB) has a high dielectric and current interruption capability. In order to design a good thermal puffer GCB, it is important to know the blast pressure for arc cooling. Although pressure calculation programs have been developed and used for design work, the basic characteristics, such as contribution of nozzle ablation gas to puffer pressure rise, amount of back flow gas to puffer chamber, and pressure distribution along gas passages during current interruption, are not well known. In this paper, pressure rise, mass flow, and temperature calculations were carried out using a new calculation model, which takes mechanical compression by puffer piston, nozzle ablation in the nozzle throat and arc energy into consideration. By analysis of the calculation results, we found the pressure rise mechanism is as follows. While fixed contact located in the divergent part of nozzle, all of the ablation gas generated from the nozzle wall cannot be exhausted from the nozzle and it leads to high-pressure generation in the nozzle throat. This pressure causes transfer of hot ablation gas back to the puffer chamber via gas passage. The puffer pressure increases thermally due to temperature rise by this mechanism. At a longer arcing time, as high puffer pressure was already established in the puffer chamber, the nozzle ablation gas cannot flow back to the puffer chamber. Besides as mass flow through nozzle is limited by low gas density, the puffer pressure rise is obtained by the mechanical compression of puffer piston.     

碱锰电池用大功率无汞锌粉的雾化装置

设计了自由降落式喷嘴雾化装置,采用六孔啧料架,通过改进喷射孔间距、喷射角,降低雾化能耗,增加锌粉比表面积,提高碱锰电池的大功率性能.在0.8 MPa的气压下,获得粒径小于150μm的锌粉超过80％;不规则形态的锌粉比表面积达0.013 m2/g,体积平均粒径达141 μm.用该锌粉制备的LR6电池的1 500 mW、6...     

Synthesis of dysprosium oxide by homogeneous precipitation

Nanocrystals of uniform dysprosium oxide (Dy₂O₃) particles have been prepared by homogeneous precipitation technique. The particles were produced by aging DyCl₃solution in presence of urea at elevated temperature. The particles were characterized with respect to their size, shape, and thermal decomposition behavior. It was found that the precipitated particles were spherical, uniform in size, and amorphous in nature. Upon heating in air, these particles decomposed into oxide and no change in morphology was observed. The dysprosium ion concentration was found to have significant effect on the particle size and its distribution.     

粒子尺寸和速度对喷嘴叶栅磨蚀特性的影响

应用PIV激光测速仪对某调节级喷嘴叶栅(73A)进行了气固两相流场测量,以研究粒子的尺寸和速度对喷嘴叶栅内粒子运动轨迹及磨蚀特性的影响。实验结果表明:随着固粒尺寸的增加,撞击速度减小,撞击角度和撞击次数增大,叶栅磨蚀大都是大、中粒子造成。粒子的撞击速度与气流速度成正比,气流速度越高,粒子对喷嘴壁面的磨蚀越严重。     

Morphology and luminescence properties of BaMgAl10O17:Eu2+ blue phosphors by Aerosol Flame Deposition

BaMgAl₁₀O₁₇:Eu²⁺ (BAM:Eu) is widely used as a blue phosphor for fluorescent lamps and plasma display panels (PDP). The improvement of the luminescence efficiency is a significant issue for applications in plasma display panels. In this study, the Aerosol Flame Deposition (AFD) was applied to fabricate BaMgAl₁₀O₁₇:Eu²⁺ (BAM:Eu) particles with spherical shape and fine size in order to improve their luminescence. The sub-micrometer powder was synthesized in spherical shape in an oxy-hydrogen flame and deposited on a substrate in the form of porous film. The particle size of as-prepared powder increased with increasing the concentration of precursor solution and the heat treatment under reducing atmosphere increased particle size additionally with surface roughening due to the needle-like crystallized phases. Photoluminescence spectrum was observed at about 450nm due to the 5d–4f transition of Eu²⁺ and the intensity of phosphor was as high as 70% of that of the commercial phosphor.     

脱硫废水旁路塔雾化蒸发数值模拟

脱硫废水成分复杂难以回用，一些电厂已开始采用烟道雾化蒸发处理技术对其进行处理。脱硫废水直接喷入烟道会带来腐蚀、积灰、堵塞等问题，设置旁路蒸发塔对脱硫废水进行干燥是一种较好的选择。为研究此项技术，以某330 MW 机组为例，通过计算脱硫废水与烟气的热质平衡，确定了烟气抽取量，建立了物理模型，利用数值模拟的方法对烟气流场进行优化，对喷嘴布置方式、液滴直径、烟气温度等的选择进行稳态模拟。结果表明：抽取烟气量仅占总烟气量的2.27%，烟气流场即能够充满整个蒸发塔；三喷嘴的雾化蒸发效果可以使蒸发塔出口温度达到设计值120℃；液滴直径80 μm 以下，液滴颗粒无贴壁，液滴直径60 μm时蒸发效果好。为延长颗粒停留时间，使颗粒无贴壁、少团聚，宜采用烟气旋流方式、三喷嘴、60 μm雾化粒径以及600 K以上的入口烟气温度。     

等离子电弧法制备纳米SnO2的试验研究

采用等离子电弧法制备粒径小、纯度高的纳米SnO2粉末.利用X射线衍射(XRD)和透射电子显微镜(TEM)对样品的物相、形貌、粒度进行了表征,研究了SnO2纳米粒子在等离子电弧焰流中的形核和长大机理,探讨了温度和过饱和度对纳米粒子形核率及粒径大小的影响.     

Heat Exchangers for Utilization of the Heat of High-Temperature Geothermal Brines

The basic component of two-circuit geothermal systems is the heat exchanger. When used in geothermal power systems, conventional shell-and-tube and plate heat exchangers cause problems related to the cleaning of the latter from salt-deposition and corrosion products. Their lifetime does not exceed, as a rule, 1 year. To utilize the heat of high-temperature geothermal brines, a heat exchanger of the “tube-in-tube” type is proposed. A heat exchanger of this design has been operated for several years in Ternair geothermal steam field; in this heat exchanger, the thermal potential of the saline thermal water is transferred to the fresh water of the secondary circuit of the heating system for apartment houses. The reduction in the weight and size characteristics of the heat exchangers is a topical problem that can be solved with the help of heat transfer enhancers. To enhance the heat transfer process in the heat exchanger, longitudinal ribbing of the heat exchange surface is proposed. The increase in the heat exchange surface from the heat carrier side by ribbing results in an increase in the amount of the heat transferred from the heating agent. The heat exchanger is easy to manufacture and is assembled out of components comprised of two concentrically positioned tubes of a definite length, 3–6 m, serially connected with each other. The method for calculation of the impact of the number and the size of the longitudinal ribs on the heat transfer in the well heat exchanger is presented and a criterion for the selection of the optimal number and design parameters of the ribs is formulated. To prevent the corrosion and salt deposition in the heat exchanger, the use of an effective OEDFK (oxyethylidenediphosphonic acid) agent is proposed. This agent has a long-lasting corrosion-inhibiting and antiscaling effect, which is explained by the formation of a strongly adhesive chelate layer difficult to wash off the surface. The passivating OEDFK layer is restored by periodical pulsed introduction of the agent solution into the brine at the heat exchanger inlet.     

低温等离子体放电管发光光谱的检测分析

为解析放电等离子体形成过程,对过程参数进行优化,以低温等离子放电管作为研究对象,在常温常压下用组合式多功能光栅光谱仪对放电光进行测量,经计算机处理,可得到空气体系中放电光的近紫外段的发射光谱.通过对放电光谱的检测分析,可以察知放电等离子体形成的途径,了解各种粒子乃至电子的能量,从而可对放电管作出相应的评价.     

超临界机组汽轮机固体颗粒侵蚀的综合研究

章在调查国内外超临界和非超临界汽轮机固体颗粒侵蚀(Solid Particle Erosion，SPE)损伤及其对机组安全经济性影响的基础上，介绍了固体颗粒的生成和特性以及采用数值计算方法研究固体颗粒在超临界汽轮机调节级和再热级内的运动特性的主要结果，并分析了汽轮机通流部分喷嘴和动叶片的侵蚀机理和侵蚀特性；章还介绍了为预防汽轮机喷嘴和动叶片免受固体颗粒侵蚀所采用的表面硬化处理技术，包括等离子喷涂层和扩散渗层在内；最后，给出了防范超临界火电机组固体粒子侵蚀的综合有效的措施，这些措施对预防非超临界机组的固体粒子侵蚀同样也是有效的。     

Study of heat exchange in cooling systems of heat-stressed structures

Increasing working parameters of the cycle of gas-turbine engines, complicating design of gas-turbine plants, as well as growing aerodynamic, thermal, static, and dynamic loads, necessitate the development of promising cooling systems for heat-stressed structures. This work is devoted to an experimental study of heat exchange in ducts equipped with systems of inclined and cross walls (fins). It has been found that an increase in the Reynolds number Re from 3000 to 20000 leads to a decrease in the heat exchange, which is characterized by the relative Nusselt number \(\overline{Nu}\), by 19–30% at the angle of inclination of the walls φ = 0, 40°, 50°, and 90° if the length of the walls x _w is comparable to the spacing b _s and by 12–15% at φ = 30° and 90° if x _w ? b _s. If cross walls are used in cooling ducts, the length of the walls x _w plays the governing role; an increase in this characteristic from 1.22 × 10^–3 to 3.14 × 10^–3 m leads to an increase in the intensity of heat exchange by 30–40% and to a decrease in the capacity of the entire system of the walls. It has been shown that, on surfaces with wavy fins, the intensity of heat exchange is closest to that determined in the models under study. For example, values of the Colborne criterion StPr^2/3 for ducts equipped with wavy fins and for the models under study differ only slightly (by 2–20% depending on the value of the angle φ). However, the difference for surfaces with short plate fins and ducts equipped with inclined walls is high (30–40%). This is due to the design features of these surfaces and to the severe effect of the inlet portion on heat exchange, since the surfaces are characterized by a higher ratio of the duct length to the hydraulic diameter L/d _h at small fin thicknesses ((0.1–0.15) × 10^–3 m). The experimental results can be used in developing designs of nozzle and rotor blades of high-temperature gas turbines in gas-turbine engines and plants.     

Size dependence of THz region dielectric properties for barium titanate fine particles

Barium titanate (BaTiO₃) crystallites with various particle sizes from 22 to 500 nm were prepared by the two-step thermal decomposition method of barium titanyl oxalate. Various characterizations revealed that these particles were impurity-free, defect-free, dense BaTiO₃ particles. The powder dielectric measurement clarified that the dielectric constant of BaTiO₃ particles with a size of around 58 nm exhibited a maximum of over 15,000. To explain this size dependence, the THz region dielectric properties of BaTiO₃ fine particles, especially Slater mode frequency, were measured using the far infrared (FIR) reflection method. As the result, the lowest Slater mode frequency was obtained at 58 nm. This tendency was completely consistent with particle size dependence of the dielectric constant.     

Effects of post-treatments on the electrochemical properties of solid-state reacted Li4Ti5O12—high energy milling and annealing

This study is designed and performed to verify whether nano-sized Li₄Ti₅O₁₂ particles can be acquired by simple high energy milling from the economic solid-state reacted coarse powder for high power lithium ion battery applications. For this, Li₄Ti₅O₁₂ is synthesized by heat treatment at 800 and 850°C for 3?h using Li₂CO₃ and TiO₂, followed by high energy milling. Even though a comparable particle size to that of expensive wet chemical methods, or even a smaller particle size of 25?nm, can be acquired by 5?h of milling, the electrochemical properties of the particles are found to be deteriorated due to the decrease in Li₄Ti₅O₁₂ crystallinity associated with the milling. On the other hand, a subsequent annealing at 750°C for the milled powder is shown to recover both the capacity and rate capability of the anode electrode owing to the increased crystallinity, indicating the importance of particle crystallinity besides a fine particle size for the enhanced electrochemical properties for high power applications.     

直接空冷机组空冷单元内喷雾增湿系统的结构优化

基于SIMPLE算法,采用k-ε模型,在综合两相流、传热传质理论并结合实际运行效果的基础上,对600 MW直接空冷机组空冷岛中的1个单元进行数值模拟,分析喷嘴纵向双层四排布置时喷嘴位置、喷雾方向、喷嘴孔径及喷雾压力对空冷凝汽器压力的影响。结果表明:喷嘴双层四排布置时,压力越大喷雾增湿效果越明显;综合考虑雾化效果和喷雾距离,1 mm为孔径的最佳值;当外排喷嘴距风机栈道中心线4 m、距风机平面高度为0.6 m、内排喷嘴距风机栈道中心线2 m、距风机平面高度1.9 m、喷雾方向在xy平面内与y轴正方向夹角为120°、喷雾压力为1.2 MPa、孔径为1 mm时,空冷凝汽器压力降幅最大,可降低8.13 kPa。