600 MW机组排汽管道内湿蒸汽的数值模拟

建立了600 MW发电机组直接空冷排汽管道内湿蒸汽两相流动和传热的数学模型.利用计算流体力学软件FLUENT,对典型工况下汽轮机的排汽状况进行了数值模拟,对二维管道内湿蒸汽速度场、温度场和两相场进行了分析和研究.结果表明:在典型工况下,流经各蒸汽分配管的流量不均,压降不同,应进行结构的改进.     

SPX直接空冷排汽管道系统内湿蒸汽的数值研究

建立了斯必克斯(SPX)公司设计的某2×135MW发电机组直接空冷排汽管道内湿蒸汽两相流动和传热的数学模型.利用计算传热学软件FLUENT,对典型汽轮机工况下的排汽状况进行了的数值模拟.对二维管道内湿蒸汽速度场、温度场和两相场的模拟、分析和研究,为空冷排汽管道系统的优化设计提供帮助.     

直接空冷枝状排汽管道系统内导流装置的优化设计

对德国基伊埃(GEA)公司发明专利——枝状直接空冷排汽管道系统进行研究。建立某2×600MW机组直接空冷排汽管道内湿蒸气两相流动和传热的数学模型;利用数值传热学软件Fluent对典型汽轮机工况下的排汽状况进行了数值模拟;对二维管道内湿蒸气速度场、温度场和两相场的模拟、分析和研究。模拟结果表明:专利提出的简单几何原则分流方法,无法实现排汽的均匀分配。针对不同形式的直接空冷枝状排汽管道系统应进行详细的优化设计,并提出了枝状排汽管道系统导流装置的基本设计原则。     

大直径负压排汽管道系统内流场的数值模拟

利用计算流体力学软件FLUENT,对大同600 MW发电机组直接空冷三维排汽管道内的水蒸汽流场进行了数值模拟.结果显示:流经各蒸汽分配管的水蒸汽压降不同,流量分配不均.研究结果为直接空冷排汽管道系统结构的优化设计提供帮助.     

超临界直接空冷排汽管道系统内流场的数值模拟

排汽管道布置形式和内部结构是直接空冷排汽系统优化设计的基础,直接影响各蒸汽分配管内的流动阻力和流量分配。利用计算流体动力学软件（CFD）,对某660MW超临界直接空冷机组排汽管道内的水蒸汽流场进行了数值模拟。通过对三维排汽管道内水蒸汽流场的模拟、分析和研究,为直接空冷排汽管道系统的优化设计提供帮助。     

2种典型直接空冷排汽管道布置的数值比较

研究直接空冷机组排汽管道的重点是在确保安全的基础上均衡各蒸汽分配管内的流量和降低流程压降。利用计算流体力学软件FLUENT对某600 MW直接空冷机组排汽管道的典型高位布置和Y型布置方式的湿蒸汽流场进行了数值模拟,并对模拟结果进行对比、分析,研究,为直接空冷系统的优化设计提供了指导。     

1000MW直接空冷机组排汽管道内湿蒸汽的数值模拟

排汽管道是空冷岛重要的系统和部件,其管线布置方式是否合理,管内压降及蒸汽流量分配均匀性是否满足设计和使用要求,影响到空冷凝汽器的运行效率和冬季的防冻维护,是直接关系到发电机组经济运行和安全的大问题。应用ANSYS、FLUENT等计算流体力学软件(CFD)对某1000MW直接空冷机组排汽管道内的湿蒸汽进行了数值模拟,并对模拟结果进行了简要分析、研究。为直接空冷机组排汽管道的设计选型提供了参考依据,并对直接空冷机组排汽管道的进一步优化设计提供帮助。     

基于流固耦合的330MW直接空冷机组排汽管道流场及应力分析

为研究某330MW直接空冷机组排汽管道内水蒸汽的流动特性和壁面的结构强度,利用FLUENT对该排汽管道内部流场进行了数值模拟,分析其流场特性以探寻排汽管道内压应力集中的部位,进而采用CAESAR II与ANSYS的流固耦合模块相结合的方法,对这些部位进行数值模拟,求出其所受等效应力,改变水平歧管的弯头非标件宽度(500mm、600mm、700mm、800mm)对其所受等效应力和内部流场进行了数值模拟。结果表明:分流器和水平歧管处压力梯度较大,是排汽管道内压应力集中的主要部位;在设计工况下,二者所受等效应力均在许用应力范围之内,水平歧管弯头非标件的最佳设计宽度为600mm。研究方法和结果可为330 MW直接空冷排汽管道设计提供参考。     

直接空冷机组排汽管道流量分配特性数值模拟

对某电厂1000MW直接空冷机组的排汽管道系统进行研究,建立处于高位布置的排汽管道上升管段的几何模型。利用流体力学软件Fluent对汽轮机处于不同工况下,管道内蒸汽流动情况进行模拟,得出机组不同流量下管道压损和流量分配特征并采用变管径的方法降低了压损,均衡各分配管流量。模拟结果表明:蒸汽流量大小对汽机排汽管道蒸汽分配情况基本无影响,通过增大支管管径的方法可以显著改善排汽管道流量分配不均现象。     

直接空冷系统排汽管道特性研究

为了研究直接空冷机组排汽管道内水蒸汽的流动特性,采用CFD技术,对某台200MW直接空冷机组排汽管道内的水蒸汽流场进行了三维数值模拟.根据数值计算结果,在直接空冷大直径排汽管道内的弯头和三通等处安装导流叶,不仅有利于减小工质在管道内的流动阻力和实现管道内工质的均匀分布,而且有利于提高直接空冷系统的整体热效率.     

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%.     

Contents in Volume 23,2014

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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.     

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。     

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.     

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.