精炼30Cr2Ni4MoV低压转子材料在超超临界机组上的应用

采用Ansys有限元方法计算了超超临界机组低压转子的温度场,并整理了精练30Cr2N i4MoV低压转子材料的物理化学特性。通过对两者的分析对比,认为超超临界机组的低压转子采用精练30Cr2N i4MoV完全可以满足设计要求。     

Synthesis and electrochemical studies of the 4 V cathode, Li(Ni2/3Mn1/3)O2

Layered Li(Ni_2/3Mn_1/3)O₂ compounds are prepared by freeze-drying, mixed carbonate and molten salt methods at high temperature. The phases are characterized by X-ray diffraction, Rietveld refinement, and other methods. Electrochemical properties are studied versus Li-metal by charge–discharge cycling and cyclic voltammetry (CV). The compound prepared by the carbonate route shows a stable capacity of 145 (±3) mAh g⁻¹ up to 100 cycles in the range 2.5–4.3 V at 22 mA g⁻¹. In the range 2.5–4.4 V at 22 mA g⁻¹, the compound prepared by molten salt method has a stable capacity of 135 (±3) mAh g⁻¹ up to 50 cycles and retains 96% of this value after 100 cycles. Capacity-fading is observed in all the compounds when cycled in the range 2.5–4.5 V. All the compounds display a clear redox process at 3.65–4.0 V that corresponds to the Ni^2+/3+–Ni^3+/4+ couple.     

Interactions between electricity-saving measures and carbon emissions from power generation in England and Wales

The relationship between electricity demand reduction and the consequent change in carbon emissions is central to greenhouse gas emissions policy. This paper examines this relationship for the power system of England and Wales. Previous analysis showed that the commonly used conversion factor based on the system average emission factor significantly underestimates these savings (Hitchin and Pout, 2002. The carbon intensity of electricity: how many kgC per kWhe?. Building Serv. Eng. Res. Technol. 23(4)). Thus any policy analysis based on the system-average emission factor will under-estimate the potential for carbon savings from reductions in electricity demand. The present paper extends the previous analysis by using more detailed modelling to explore differences between demand reductions of differing load shape and magnitude; and the sensitivity of these figures to changes of the fuel mix of the generation system.     

可充碱性锌锰电池进展

本文综合介绍了可充碱锰电池的最新进展,重点论述了目前国际上正在研制开发的两种可充二氧化锰电极,即奥地利kordesch的加压式二氧化锰电极和美国Ford公司的改性二氧化锰电极,对各自的特性进行了分析对比,阐明了可充碱锰电池的发展方向。     

大型汽轮发电机转子材料26Cr2Ni4MoV钢疲劳性能的研究

本文研究了大型汽轮发电机转子材料26Cr2Ni4MoV钢的疲劳性能。疲劳裂纹扩展门槛值△K_(th)和扩展速率da/dn的试验结果表明.应力比R严重影响门槛值△K_(th)和扩展速率da/dn。随着应力比的增加,门槛值下降。通过应变片法测量出裂纹尖端的闭合载荷,用裂纹闭合机制合理解释了应力比R对门槛值△K_(th)扩展速率da/dn的影响,提出了门槛值和扩展速率随应力比变化规律。     

金属尾矿中的FeS2在水泥烧成中的节能作用分析

金属尾矿的堆弃是自然环境的一大公害，如果能所废弃的金属尾矿变成商品生产的一种原料，将是十分理想的，对含FeS2较高的金属尾矿做了多方面的实验研究，分析其应用于水泥原料中产生的各种效益，结果得出其能产生明显的节能效果，此外还可降低成本，保护环境。     

Sprayed CuInS2 films grown under Cu-rich conditions as absorbers for solar cells

CuInS₂ films were prepared by the spray pyrolysis method using either copper-rich solutions or the recrystallization of low-crystallinity film in the presence of an intentionally deposited Cu_xS layer. KCN-etched films were characterized by XRD, SEM and EDX. The Cu/In molar ratio of 1.5–4.0 in the solution resulted in well-crystallized CuInS₂ films with the mean crystallite size of 120 nm. SEM study showed nonuniform surface with irregularly placed large grain domains in the flat film. The two-step process resulted in a uniform film with the crystallite size of 50 nm. Films exhibited an In-rich composition. Solar cells based on a recrystallized absorber showed an improved quantum efficiency spectrum.     

Multiobjective optimisation of integrated energy systems for remote communities considering economics and CO2 emissions

The methods for designing, planning and managing integrated energy systems, while holistically considering the major economic and environmental factors, are still embryonic. However, the first phase of the design is often crucial if we want to manage resources better and reduce energy consumption and pollution. Considering integrated energy systems implies dealing with complex systems in which the synergy between the various components is best exploited (for example the thermal energy of a diesel engine produced during the night is complimented by the Rankine organic cycle of a solar thermal plant). The context of isolated communities further increases the difficulties when considering the long distance of transport required to supply fossil fuels. These sites are often located in very precarious environments, with limited or nonexistent resources except for solar energy, and with frequent additional needs for desalination (in arid zones).This paper illustrates a holistic method to rationalize the design of energy integrated systems. It is based on a superstructure (collection of models of all envisaged technologies) and a multi-objective optimisation (resources, demand, energy, emission, costs) using an evolutionary algorithm. The approach proposed allows the identification of more complete and more coherent integrated configurations characterizing the most promising designs (also taking into account the time dependency aspects). It also allows to better structure the information in view of a participative decision approach. The study shows that the economic implementation of renewable energy (solar) is even more difficult, compared to diesel based solutions, in cases of isolated communities with high load variations. New infrastructure or retrofit cases are considered.     

Distributed grid-connected photovoltaic power system emission offset assessment: statistical test of simulated- and measured-based data

This study assesses the pollutant emission offset potential of distributed grid-connected photovoltaic (PV) power systems. Computer-simulated performance results were utilized for 214 PV systems located across the US. The PV systems’ monthly electrical energy outputs were based on a performance calculator called PVWATTS. Offset emissions of sulfur dioxide (SO₂), carbon dioxide (CO₂), and nitrogen oxides (NO_x) were determined from PV system outputs and average utility emissions data from each state. For validation, the simulated monthly results were statistically compared with measurement-based data (both production and corresponding emissions data) from 29 PV systems installed at different sites across the US.

While the data shows high (geographic) variability, the substantial number of measurements allows reliable statistical analysis. The methods are found to give consistent results in spite of the necessity to employ some even quite crude input approximations—such as the use of statewide rather than specific emissions data for the systems. No significant differences between simulated and measured monthly means for any of the pollutants were noted on the basis of individual monthly analyses, though the results for NO_x suggest the possible existence of some difference in that case. A more detailed statistical modeling using all monthly data in one combined analysis (allowing improved variability estimation) confirms these conclusions. Even the shorter confidence intervals for expected offsets obtained through the combined analysis show no significant differences between simulated and measured methods for SO₂ and CO₂. The differences for NO_x are statistically significant but consistent—suggesting useful prediction by the simulations via a constant correction factor. As expected, significant differences between months are evident for both simulated and measured offsets.     

Effect of polymorphic phase transformations in Al2O3 film on oxidation kinetics of aluminum powders

Thermogravimetry was used to study the oxidation of aluminum powders at elevated temperatures. Aluminum powders of various particle sizes and surface morphologies were heated in oxygen up to 1500 °C at different heating rates. Partially oxidized samples were recovered from selected intermediate temperatures and the oxide phases present were analyzed by X-ray diffraction. The experimental data were related to current information on stabilities and phase changes of Al₂O₃ polymorphs. Aluminum powders were observed to oxidize in four distinct stages in the temperature range from 300 to 1500 °C. During stage I, from 300 to about 550 °C, the thickness of the natural amorphous alumina layer on the particle surface increases. The rate of this process is controlled by the outward diffusion of Al cations. At about 550 °C, when the oxide layer thickness exceeds the critical thickness of amorphous alumina of about 4 nm, the oxide transforms into γ-Al₂O₃. The specific volume of γ-Al₂O₃ is less than that of amorphous alumina; therefore, the newly formed γ-Al₂O₃ only partially covers the aluminum surface. The oxidation rate increases rapidly at the onset of stage II, but it decreases when the γ-Al₂O₃ layer becomes continuous. During stage III oxidation, the γ-Al₂O₃ layer grows and partially transforms into the structurally similar θ-Al₂O₃ polymorph. Finally, oxidation stage IV is observed after the transition to stable -Al₂O₃ results in an abrupt reduction of oxidation rate. Qualitative analysis of the rates of oxidation at the different stages enables one to understand the wide range of aluminum ignition temperatures observed for particles of different sizes.