Effect of specimen thickness on the growth rate of chromia scales on Ni-base alloys in high- and low-pO2 gases

Two types of experiments were carried out to study the oxidation behaviour of NiCr-base model alloys; thermogravimetric measurements for up to 72 h exposure at 1000 °C in synthetic air and isothermal exposures for up to 100 h at 1000 °C in laboratory air and in Ar–4%H₂–2%H₂O. It was found that there is a significant effect of specimen thickness on the oxidation rate of all studied alloys. The growth rates of the chromia scales decrease with increasing specimen thickness in both air and the Ar–H₂–H₂O mixture. Based on the present results in combination with recent literature data for ferritic steels, it is postulated that the decrease in rate is the result of compressive growth stresses in the scales which can relax by plastic deformation of the substrate for thin specimens but are maintained at significant levels for thick specimens.     

Voltage–time behavior of a polymer electrolyte membrane fuel cell stack at constant current discharge

Empirical equations were developed to describe the voltage–time behavior of polymer electrolyte membrane fuel cell (PEMFC) stacks at constant current discharge. When either ambient temperature or discharge current is too high, the experimental voltage–time curves exhibit rapidly falling cell voltage within a short discharge time. Various experimental voltage–time curves have been fitted very well with empirical equations at different discharge currents and ambient temperatures. The effect of parameters of the empirical equations on the shape of voltage–time curve is also analyzed. Inadequate mass-transfer is likely a reason for the voltage falling down rapidly, and polymer electrolyte membrane dehydration is responsible for the inclination of the voltage–time curves. The empirical equations are helpful for forecasting and explaining the long-term discharge performance of the PEMFC stacks.     

600MW超临界机组轴振异常原因分析及处理

某电厂一台600 MW超临界汽轮发电机组投产后,1号轴振逐步爬升,经多次检修均未能稳定。试验分析表明振动异常是由高中压转子受汽流激振力和轴承轻载共同作用所引发。通过轴系中心调整和优化高压调门开启顺序,使振动得到较好控制。     

Pyrolysis of asphalt in the presence and absence of water

The bitumen used for the embedding of nuclear wastes has been pyrolysed in confined and hydrous systems, in order to evaluate while an elevation of the temperature in the deep geological repository could induce chemical transformations of the bitumen matrix, which could influence its confining properties. The pyrolysates have been extracted in chloroform and the extract has been separated in aliphatic and aromatic hydrocarbons, resins and asphaltenes. These different fractions have been analyzed by GC-MS and μ-IRTF. Few modifications of the bitumen structure are observed up to 300 °C. Above this temperature, the pyrolysis of the bitumen generates light hydrocarbons and an aromatic and condensed insoluble residue. The use of the time–temperature index allows to estimate the temperatures which have to be reached in the repository in order to observe the first transformations of the bitumen.     

生物质发电及能源化综合利用

以生物质发电项目为依托,阐述了生物质利用的意义,生物质能源化综合利用技术展望,分析了生物质燃料的特性,生物质燃烧发电技术,生物质气化及发电技术,指明了生物质能综合利用将是未来生物质能利用的主要方向。     

Effect of Two-Level Over-Fire Air on the Combustion and NOx Emission Characteristics in a 600 MW Wall-Fired Boiler

This paper accomplishes a numerical investigation on the effect of two-level over-fire air (OFA) on the combustion and NO_x emission in a supercritical 600 MW wall-fired boiler. Different arrangements of two-level OFA nozzles and different airflow ratios between the two layers are set to examine NO_x emission and the carbon content in fly ash. According to the simulation results, the two-level OFA case releases the NO_x between the single upper layer and the single lower layer of the two-level OFA nozzles in operation. Moreover, the two-level OFA arrangement gives a lower carbon content in fly ash than the single-level OFA cases. In addition, both low NO_x emissions and low carbon content in fly ash can be obtained simultaneously when the two levels of OFAs are injected from Layers 1 and 4 with r_lower at 0.5.     

空冷风机单元振动故障原因分析及处理

针对山西右玉电厂330MW直接空冷机组空冷风机单元振动问题,对风机单元进行了测试和分析,给出了风机、减速机及风机桥架的振动规律。通过采取风机桥架加固、将风机由5叶改为6叶等措施,消除了空冷风机单元振动故障。此次振动故障的处理过程及相关试验结果,对风机单元设计及施工具有一定的借鉴意义。     

A robust surrogate model of a solid oxide cell based on an adaptive polynomial approximation method

Surrogate models that predict the behaviors of solid oxide cells (SOCs) accurately at low computational cost are crucial to the control and optimization of SOC plants. Lumped physical models of SOCs, while widely used in such applications, lack accuracy because of neglected physical details. Data-driven models are the other options of surrogate models, which are proved to be more accurate because these models are identified directly from experiments or numerical simulations. However, due to the time cost of experiments and numerical simulations of SOCs, it is hoped that data-driven models can be constructed from a minimum amount of data. Also, the trained data-driven models should be robust, in other words, insensitive to the data set as well as the initial settings. These requirements are hard to be achieved by existing data-driven models of SOCs, such as lookup tables and artificial neural networks (ANNs). Aiming to preserve robustness and reduce the required amount of data, this paper introduces an adaptive polynomial approximation (APA) method, which is derived from the latest findings of numerical computation science, to the surrogate modeling of SOCs. The obtained models by the APA method are validated by both experiments and simulations. By analyzing the models, the coupling relationship among operating parameters of SOCs is revealed. The physical interpretability makes the APA method distinctive from common data-driven modeling methods. Performance comparison shows that the APA method is more accurate and robust than the existing ones with similar sampling costs. Additionally, the APA method can control the accuracy of the model by setting an error criterion in the algorithm iteration, endowing the APA method with an error control ability as per different accuracy requirements for SOC modeling.     

山西省燃气发电建议

在分析山西省煤层气资源情况的基础上,结合电力系统负荷特性,燃气电厂的运行特点,新能源发电的发展和电网调峰需求,提出了电网对燃气电厂发展的相关要求,围绕新能源发电的协调发展提出相应建议和措施。