高海拔地区500kV线路中相V串优化

高海拔地区空气稀薄,输电线路金具电晕现象较平原地区更为严重。以建塘500kV变电站和玉龙500kV变电站之间线路为例,应用Ansys有限元分析软件,计算了500kV交流单回线路中相V串金具电场和绝缘子串电位分布,获得了不同管径和环径的均压环配置下绝缘子串的电压分布、均压环表面场强结果,并根据海拔校正公式,按18.2kV/cm表面控制场强限值给出了V串金具优化设计建议,结果可供参考。     

330 kV输电线路均压环优化研究

通过有限元法建立均压环仿真计算模型,对4种不同管径以及2种不同曲率半径330kV交流输电线路均压环表面场强进行计算分析,在特高压户外试验场以及特高压交流试验基地环境气候实验室开展均压环可见电晕试验研究,获得不同结构型式均压环表面电场分布规律、结构优化试验对比结果以及不同海拔条件下均压环电晕起始电压特性曲线。研究结果表明,通过优化均压环管径以及曲率半径方法,可有效降低均压环表面电场强度,提高电晕起始和熄灭电压,推荐校正算式校正误差小于CB311．1—1997和IEC60071—2：1996所提方法,可为高海拔地区输电线路均压环选型及优化设计提供参考依据。     

超高压交流变电站金具电晕特性与选型研究

为消除电晕放电造成的能量损耗和电磁干扰,对不同种类金具的电晕特性以及不同电压等级下金具选型进行研究。利用紫外成像仪对几座超高压交流变电站的电晕放电现象进行观测,找出易发生电晕放电的金具;对此金具结构建立三维有限元仿真模型,计算在施加500 kV和750 kV电压等级下,不同尺寸金具表面电场强度分布情况,并针对场强较大的结构进行优化设计。研究结果表明,随着均压环、屏蔽环管径和屏蔽球球径的增大,其表面电场强度逐渐减小;结合金具表面起晕场强控制限值,给出了500 kV和750 kV电压等级下,耐张绝缘子串屏蔽环、V型绝缘子串均压环以及导线屏蔽球的尺寸选型。     

750 kV变电站门形构架双联耐张绝缘子串均压环选型研究

变电站门形构架绝缘子金具表面电场强度超过规定限值后,会在金具尖端或均压环外端面形成电晕放电,增加了站内整体电磁噪声和电能损耗,尤其海拔高度对电晕放电场强限值影响较大。以海拔高度大于1 000 m的750 kV沙州变电站为例,采用ANSYS仿真计算了变电站门形构架双联耐张串绝缘子金具不同均压环管径、连接板表面的电场强度,获得了相应的电场分布图,通过对比确定了750 kV变电站门形构架双联耐张串绝缘子均压环优化选型方案。在天气较好条件下,分别测量了沙州750 kV变电站门型构架四分裂母线与跨线处的噪声,1～6 kHz频段内噪声最大值均低于相关标准的昼间要求,这验证了金具优化后效果较好。     

750 kV输电线路杆塔间隙和塔宽对操作冲击放电电压的影响

在现有750 kV输电线路工程模拟真型塔试验条件下,通过调整模拟横担和模拟塔腿来实现模拟风偏角,施加标准操作冲击电压,求取在风偏情况下杆塔联合间隙50%放电电压,对比单独间隙的标准操作冲击50%放电电压。研究了750 kV同塔双回线路风偏情况下联合间隙对操作冲击放电电压的影响。在不同塔宽情况下,通过调整导线与塔腿的最小间隙,施加长波前(720μs)操作冲击,求取50%放电电压来研究750 kV同塔双回线路塔宽对操作冲击放电电压的影响。     

高海拔地区220kV同塔双回耐张换位方式

针对高海拔地区220 kV同塔双回线路绝缘子串较长、间隙大的特点,通过分析与比较,提出了一种采用同塔双回耐张内绕跳换位新技术,其特点是安装方便、便于运行、保护环境、节约资源,并且适用于导线垂直排列的同塔双回线路工程,这一技术成功解决了新都桥一甘孜等高海拔同塔双回长线路的耐张换位问题,具有推广应用价值。     

750kV输电线路杆塔间隙和塔宽对操作冲击放电电压的影响

在现有750kV输电线路工程模拟真型塔试验条件下，通过调整模拟横担和模拟塔腿来实现模拟风偏角，施加标准操作冲击电压，求取在风偏情况下杆塔联合间隙50％放电电压，对比单独间隙的标准操作冲击50％放电电压。研究了750kV同塔双回线路风偏情况下联合间隙对操作冲击放电电压的影响。在不同塔宽情况下，通过调整导线与塔腿的最小间隙，施加长波前（720μs）操作冲击，求取50％放电电压来研究750kV同塔双回线路塔宽对操作冲击放电电压的影响。     

500 kV输电线路跳线金具电晕放电特性

输电线路相邻耐张段导线之间一般采用跳线方式连接,跳线金具结构复杂,产生的电晕严重。为获得跳线金具的电晕放电特性,利用紫外成像仪对不同结构、安装数量及位置的500 kV输电线路跳线间隔棒进行试验,获得了间隔棒的起晕电压值;同时对间隔棒中的线夹结构进行试验,并利用有限元法计算其电场分布。分析结果表明,不同试验方法获得的金具电晕放电特性存在差异,实际应用中应根据工程需要及现场具体情况,选择合适的跳线金具。     

750 kV同塔双回线路接地开关的选择研究

针对750kV西宁-永登-白银输变电工程,使用电磁暂态程序(EMTP)计算了750kV同塔双回线路的感应电流、电压。通过对计算结果的分析并结合IEC标准,提出本工程750kV同塔双回线路接地开关的参数要求:电磁感应电流和电磁感应电压及静电感应电流满足B类标准要求,静电感应电压超出B类标准,要求为55kV。     

750kV同塔双回线路接地开关的选择研究

针对750kV西宁-永登-白银输变电工程，使用电磁暂态程序（EMTP）计算了750kV同塔双回线路的感应电流、电压。通过对计算结果的分析并结合IEC标准，提出本工程750kV同塔双回线路接地开关的参数要求：电磁感应电流和电磁感应电压及静电感应电流满足B类标准要求，静电感应电压超出B类标准，要求为55kV。     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.     

Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

Contents in Volume 23,2014

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汽轮机数字电液调节系统挂闸异常的技术完善

分析了200MW汽轮机数字电液调节系统在运行中存在的挂闸异常问题,采取了相应的技术处理措施,且运行实践效果良好。     

新型高压共轨ECU升压模块的数字化开发与优化

为了提高喷油器电磁阀的响应速率,提出了一种基于CPLD(复杂可编程逻辑器件)应用于高压共轨ECU的数字升压模块。鉴于该升压电路结构参数多,其升压电压的恢复响应要求高等特征,基于Pspice建立了升压电路的仿真模型,研究了不同电路参数下升压模块的输出特性,全面优化了该升压模块的性能。结果显示,该升压模块的最大转换效率可以达90%以上。在柴油发动机上对ECU的试验表明,升压电压最大波动不超过10%,其恢复时间仅为1.3ms,功率管最大温升仅为41℃,满足整机运行范围内ECU的需求。     

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.     

Assessment methods of material ageing using Sdobyrev''s creep rupture model

The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σ_red = σ₁ β + (1 − β)σ_i, where: σ₁-maximal principal stress, σ_i-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures.     

Production of hydrogen from sewage biosolids in a continuously fed bioreactor: Effect of hydraulic retention time and sparging

Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H₂ kg⁻¹ VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min⁻¹ successfully prevented a decline in hydrogen production and resulted in a yield of 27.0  L H₂ kg⁻¹ VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production.