煤粉切圆燃烧П型布置锅炉屏式过热器热力不均匀分析与优化布置

基于对煤粉切圆燃烧П型布置锅炉屏式过热器烟气侧热力不均匀特性举例分析,以及对现有减轻屏式过热器热偏差技术措施的总结,给出了解决煤粉切圆燃烧П型布置锅炉前屏过热器与后屏过热器各屏间热偏差的方法,利用结构不均、水力不均和热力不均相互匹配的方法给出了前屏过热器与后屏过热器的优化布置方案,对减轻煤粉切圆燃烧П型布置锅炉屏式过热器热偏差有参考价值。     

循环流化床锅炉屏式过热器设计探讨

文中指出了大中型循环流化床锅炉采用屏式过热器的必要性,概述了屏式过热器的布置方式,提出了设计质量流速的合理范围以及壁温计算应遵循的原则,总结了屏式过热器在结构设计中防磨、热膨胀、穿墙密封等方面的经验。     

锅炉屏式过热器集箱安装焊缝热处理工艺的改进

本文针对中电广西防城港电力有限公司锅炉屏式过热器集箱焊缝热处理硬度不合格，热处理曲线不能满足标准要求进行原因分析，并采取了相应的改进措施，解决了屏式过热器集箱焊缝现场热处理工艺技术难题，对屏式过热器集箱焊缝热处理工艺的编制具有参考作用。     

屏式过热器同屏热偏差的成因和计算方法

本文分析了屏式过热器同屏热偏差的成因,提出了计算方法;列出了六台电站锅炉屏式过热器同屏热偏差的计算结果与实测值的比较,并提出了减小同屏热偏差的结构措施.     

大容量锅炉屏式过热器利用系数的研究

采用三维数值计算方法,对1台660 Mw超超临界Ⅱ型锅炉分隔屏和后屏过热器在5种负荷工况下的传热情况进行了模拟,并结合锅炉热力计算标准方法对两类屏式过热器的利用系数进行了修正.结果表明:炉膛火焰辐射及烟气对管屏的不均匀冲刷导致了管屏壁面传热不均匀;锅炉负荷变化对屏式过热器利用系数的影响很大,在5种负荷工况下,两类屏式过热器的利用系数均随着锅炉负荷的提高而增大.     

300MW循环流化床锅炉屏式过热器传热特性及壁温研究

建立了循环流化床锅炉屏式过热器传热模型,采用分区段方法计算了受热面管子在锅炉3种典型负荷下,管内工质温度和管壁金属温度的沿程分布特性;利用实炉运行数据研究了锅炉在不同负荷下屏式过热器传热系数的变化规律,分析了低负荷下循环流化床锅炉屏式过热器超温的原因.结果表明:循环流化床锅炉屏式过热器热负荷较均匀,管壁温度没有明显的突升情况,最高管壁温度出现在75％ BMCR(锅炉最大连续蒸发量)负荷下.     

大型锅炉屏式过热器热力计算方法分析

对传统的屏式过热器的热力计算方法进行了分析研究,同时提出了一种更为严格的计算方法,并将两种方法的差异做了对比,分析了这种差异对锅炉屏式过热器的设计和运行产生的影响。结果发现传统的热力计算方法存在物理意义上的不严密以及计算结果对屏式过热器的安全不利等问题。     

电站锅炉屏式过热器管壁温度的数值分析方法

对屏式过热器的壁温计算方法进行了分析研究,通过对比分析,采用了一种更为严格的数值计算方法,并且编制了壁温数值计算程序。将屏式过热器各管离散化为小单元,按工质流动顺序逐次计算小单元的热负荷,进而求出壁温分布。对屏式过热器入口烟温进行二维离散,考虑了影响管子传热的结构、位置、流动等偏差因素。该方法便于在计算机上实现快速准确的管壁温度预测。     

浅谈600MW等级超临界工程屏过、末过异种钢焊口断裂问题

介绍了600MW等级超临界锅炉屏式过热器、末级过热器异种钢焊口断裂问题,原因分析及处理方法。     

屏式过热器同屏各管汽温偏差的计算方法

屏式过热器是高参数大容量锅炉中重要部件之一。1957版苏联的热力计算标准中有关屏式过热器壁温计算的方法没有将同屏各管之间很大的汽温偏差考虑进去,因此不符合实际情况。根据它的方法来设计屏式过热器有超温爆管的险险。本文中首先分析了造成同屏各管汽温偏差的四个原因,并在这个基础上导出了计算同屏各管汽温偏差的方法和公式。为了简化计算,在计算公式中引入了若干特性参数,并加以图表化。     

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.     

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.     

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.