温度分层型水蓄冷槽布水器的斜温层试验分析

为了分析温度分层型水蓄冷槽中布水器的开口间距和直径对温度分层的影响,对四种不同开口间距的布水器在充放冷过程中的温度分布以及两种口径布水器在充冷时蓄冷槽的温度分布。试验结果表明,孔口开孔直径和开口间距对温度分布有很大的影响,在相同流量下,空口开口直径大的布水器比开口直径小的布水器形成的斜温层更薄、更稳定;开口间距与开口高度比值在1～2之间的布水器的蓄冷效果较好。     

自然分层型水蓄冷槽布水器的模拟

介绍了自然分层型水蓄冷技术的国内外研究现状，分析影响自然分层型水蓄冷槽蓄冷特性的主要因素。采用CFD商业模拟软件FLUENT6对三种不同类型的布水器建立模型，模拟其充冷过程中的温度分布和速度场，并进行比较分析，优化布水器的设计。     

多孔布水器蓄冷水槽性能影响因素分析

自然分层蓄冷水槽中的出流流动是多孔平行射流流动，决定蓄冷效率的因素是布水器的性能及蓄冷水槽的几何因素。首先对布水器的性能进行了分析，通过对单孔出流控制方程组进行数量级分析得到了无因次方程组；对无因次方程组的分析得到了影响布水器出流性能的决定因素是R8数和Fr数，并且指出Re数和Fr数中应选择单孔的几何尺寸作为定型尺寸。进一步对蓄冷水槽出流流动的影响因素进行了分析，指出蓄冷水槽的几何因素对蓄冷效率有影响。     

盘管式外融冰槽融冰过程试验研究(Ⅱ)--温度分布

准确掌握盘管式外融冰取冷规律对外融冰系统的控制至关重要。在前一部分考察取冷各种因素对冰槽宏观取冷特性影响的基础上，重点研究了取冷过程冰槽内温度分布的动态变化过程，从温度分布变化的角度分析了各种因素对取冷特性的影响过程。分析表明：当取冷流量较小时，冰槽内自然对流作用得以体现，出现明显温度分层；各种因素对于取冷特性的影响直接影响浮升力和惯性力的对比关系，进而影响斜温层和槽内温度分布，最终导致取冷特性发生变化。     

Effect of obstacles with different opening means on thermal stratification in hot water storage tanks

为研究具有内置隔板的太阳能蓄热水箱隔板开孔尺寸及位置对其内部热分层效果的影响,对9种隔板开孔位置的太阳能蓄热水箱内温度场进行了数值分析,结果显示：在相同的流动参数及开孔面积条件下,隔板中心开1个圆孔的水箱热分层效果最好。对于多开孔的水箱,开孔位置对水箱内热分层影响不大,但对蓄热量影响显著。对于隔板中心开1个圆孔的水箱,在不同流动参数条件下,冷、热水出口温差随着冷水入口流速的增大呈先增后减的趋势,当冷水入口流速大于0.9 m/s时,减弱了热分层的稳定性。     

喷雾增湿对间接空冷机组散热器影响的数值研究

通过建立350MW间接空冷机组空冷散热器喷雾增湿系统的三维数值模型,利用Fluent软件对该系统进行数值模拟,分析了喷嘴位置及喷雾方向对散热管束换热效果的影响。模拟结果表明:在喷水量一定的前提下,喷嘴双排布置时散热管束的换热效果优于单排布置;而在塔外布置喷雾增湿装置,改变喷嘴的喷射方向时,散热管束外表面温度进一步降低,并且喷射角度为60°和90°时温度最低,散热器换热效果好。     

进风角度对椭圆管翅式换热器流动性能的影响

基于多孔介质模型,对两排椭圆管翅式换热器实验元件在不同进风角度(30°、45°、60°和90°)下的流动性能进行了数值模拟,并与实验结果进行对比,研究了不同进风角度下换热器迎风面气流速度的分布.结果表明:在进风角度测试范围内,随着进风角度的减小,换热器流动阻力损失增大;不同进风角度时总压差Δp计算结果与实验结果的差别均小于7%;进风角度为90°时两相邻椭圆管间通道速度分布最均匀.     

入射角度对缩放槽缝孔气膜冷却效果的影响

基于有限体积法对三维定常不可压缩N-S方程进行离散,采用两层k-ε湍流模型,在吹风比M为0.5、1.0、1.5和2.0的情况下,数值研究了入射角度(α=25°、45°和60°)对缩放槽缝孔气膜冷却效果的影响,对不同入射角度的气膜冷却整体效果进行了对比分析。结果表明:在任何吹风比的情况下,α=25°喷射时的冷却效率高于其它喷射角的冷却效率,并且随着吹风比的增大,小角度喷射优于其它喷射角的趋势也越来越大;入射角度为45°和60°的气膜孔沿孔排下游的冷却效率在下降过程中重新升高然后又继续下降,60°喷射角的上升趋势略大于45°角的上升趋势;大角度喷射时,在气膜孔下方生成了强度较强的反向涡旋对,两个旋涡之间的距离较近,冷却气流的附壁性较差,冷却效率较低。小角度喷射时,所生成的反向涡旋对与大角度喷射相比尺度较小、强度较弱,冷气射流对主流的阻碍作用比较小,冷却效率较高。     

超临界CO2/R41混合工质在螺旋槽管内冷却流动传热特性的数值研究

为降低超临界CO₂的工作压力并强化传热,在恒热流冷却工况下对螺旋槽管内超临界状态下CO₂和CO₂/R41混合工质的流动传热过程进行了数值模拟,分析了热流密度、质量流速和倾斜角度等因素对流动传热过程的影响。结果表明：相较于超临界CO₂,超临界CO₂/R41混合工质在临界压力差更大的情况下,其最大传热系数提高了7.7%,且传热系数衰减幅度更小;螺旋槽管在高温区的传热系数相较于低温区有明显提升,且热流密度越大,传热系数越大;受浮升力影响,倾斜角度小于0°时传热系数较大,倾斜角度在45°～90°时会发生传热恶化,且倾斜角度为-45°～45°时凹槽处会形成涡旋。     

基于分层蓄热水箱的相变球释热实验研究

相变蓄热水箱可有效调节集热器和负载端之间供求不匹配的矛盾,设计了环形布水器进水结构和蓄热水箱,并搭建相变蓄热水箱性能测试平台,对比直进型蓄热水箱和环形布水器蓄热水箱的温度分层,探究孔隙率、进水流速和变温进水等变量下相变蓄热水箱的热分层和相变球的释热性能。实验研究表明：环形布水器能有效抑制进水水流对温度场的扰动,保持良好的温度分层,使相变球逐层放热,增大相变球与传热流体（HTF）的温差,提高释热效率,保证高温水能够源源不断地提供给用户端;孔隙率越小分层效果越好;流速越大分层效果越差,但是释热效率有所提高;变温进水比恒温进水,释热时间延长约40%。     

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。     

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.