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71.
随着电压等级的不断提高,超高压输电线路发展非常迅速.但是这些架空输电线路在运行时,附近存在较高的电场,对周围物体和公用走廊的其它线路会产生影响.电压等级越高,产生的电场影响越大.输电线路产生的电场越来越受到人们的重视.尤其是对于超高压输电线路,由于在电力铁塔上同塔悬挂全介质自承式光缆(ADSS),因此分析工频电场对ADSS光缆特性的影响非常必要. 相似文献
72.
73.
Theoretical and numerical investigation of flow stability in porous materials applied as volumetric solar receivers 总被引:1,自引:0,他引:1
M. Becker Th. Fend B. Hoffschmidt R. Pitz-Paal O. Reutter V. Stamatov M. Steven D. Trimis 《Solar Energy》2006,80(10):1241-1248
This article reports results of a theoretical analysis as well as a numerical study investigating the occurrence of flow instabilities in porous materials applied as volumetric solar receivers. After a short introduction into the technology of volumetric solar receivers, which are aimed to supply heat for a steam turbine process to generate electricity, the general requirements of materials applied as solar volumetric receivers are reviewed. Finally, the main methods and results of the two studies are reported. In the theoretical analysis it is shown that heat conductivity as well as permeability properties of the porous materials have significant influence on the probability of the occurrence of flow instabilities. The numerical study has been performed to investigate the occurrence of unstable flow in heated ceramic foam materials. In the simulations a constant heat flow of radiation, that is absorbed in a defined volume, and constant permeability coefficients are assumed. Boundary conditions similar to those of the 10 MW Solucar Solar project have been chosen. In a three dimensional, heterogeneous two phase heat transfer model it was possible to simulate local overheating of the porous structure. The parameters heat conductivity, turbulent permeability coefficient and radial dispersion coefficient have been varied systematically. Consequently, for a heat flux density of 1 MW/m2 a parameter chart could be generated, showing the possible occurrence of “unstable” or “stable” thermal and fluid mechanical behaviour. These numerical results are beneficial for the design of optimized materials for volumetric receivers. 相似文献
74.
风力发电机组塔架仿真和分析 总被引:1,自引:0,他引:1
简单介绍了风力发电机组塔架的类型和风力发电机组塔架设计的重要性。分别在某种参考风速及其风向改变90°和180°条件下,运用风力发电机组设计软件Bladed for Windows对风力发电机组塔架风载荷进行了仿真分析。最后,结合仿真结果和实际情况分析了叶片安装角、风轮锥角、风轮仰角、悬距、塔架气动阻力系数和塔架线密度等对塔架风载荷的影响。为风力发电机组的塔架设计提供了参考。 相似文献
75.
进气系统阻力对柴油机性能影响的试验研究 总被引:1,自引:0,他引:1
余兀 《柴油机设计与制造》2006,14(1):42-44
通过发动机台架试验,研究进气系统阻力对柴油机性能的影响。得到D9-220柴油机进气系统和空滤器的最大阻力限值,为进气管路的设计和空滤器的选择提供了依据。 相似文献
76.
改善冷却塔冷却负荷方法的探讨 总被引:4,自引:0,他引:4
本文分析制冷剂冷凝温度、循环冷却水温和流量对制冷量的影响,并根据华南沿海地区夏季气候湿热,冷却塔负荷过大而冷却水温往往达不到额定工况的特点,结合冷凝热回收和喷泉冷却系统的工程实例,探讨降低冷却塔负荷及冷却水温的方法。 相似文献
77.
This study presents a methodology to assess suitability of a site for small scale concentrated solar power (CSP) systems for its energy conversion efficiency and make‐up water requirement. Energy conversion efficiency of CSPs relies not only on the level of direct solar radiation but also on the performance of the cooling system. Regions with high solar potential have to deal with heat rejection at elevated temperatures which causes reduced energy conversion efficiencies due to high condenser temperatures. It is desirable to utilize wet cooling systems as they can achieve temperatures lower than the dry bulb temperature by evaporative cooling. On the other hand, such regions usually lack water resources which deteriorate the sustainable nature of CSP applications. This study combines various available models for both solar resource estimation and cooling systems' performance considering (i) the influence of ambient temperatures, and (ii) the influence of humidity levels. These models are integrated together to analyze the use of dry or wet cooling systems in terms of overall energy output and water consumption at a selected site in northern Cyprus. The model inputs consist of only annual hourly surface weather data and the location of the site of interest. The results show that dry cooling unit at northern Cyprus is capable of saving water about 18.7 ton/MWh while it produces 27% less energy compared to the wet cooling alternative for the representative annual weather data. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
78.
Model improvements for evaluating the effect of tower tilting on the aerodynamics of a vertical axis wind turbine 下载免费PDF全文
If a vertical axis wind turbine is mounted offshore on a semi‐submersible, the pitch motion of the platform will dominate the static pitch and dynamic motion of the platform and wind turbine such that the effect of tower tilting on the aerodynamics of the vertical axis wind turbine should be investigated to more accurately predict the aerodynamic loads. This paper proposes certain modifications to the double multiple‐streamtube (DMS) model to include the component of wind speed parallel to the rotating shaft. The model is validated against experimental data collected on an H‐Darrieus wind turbine in skewed flow conditions. Three different dynamic stall models are also integrated into the DMS model: Gormont's model with the adaptation of Strickland, Gormont's model with the modification of Berg and the Beddoes–Leishman dynamic stall model. Both the small Sandia 17 m wind turbine and the large DeepWind 5 MW are modelled. According to the experimental data, the DMS model with the inclusion of the dynamic stall model is also well validated. On the basis of the assumption that the velocity component parallel to the rotor shaft is small in the downstream part of the rotor, the effect of tower tilting is quantified with respect to power, rotor torque, thrust force and the normal force and tangential force coefficients on the blades. Additionally, applications of Glauert momentum theory and pure axial momentum theory are compared to evaluate the effect of the velocity component parallel to the rotor shaft on the accuracy of the model. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
79.
本文结合工信部联通[2008]235号文,对已完成的铁塔标准化设计的共建场景和范围进行了深入分析,针对不能满足需求的场景进行了调研分析,提出并完成了共建铁塔标准化设计的范围和技术经济指标,最终将其纳入铁塔标准化体系。 相似文献
80.