4吨/时凹型布风板组装式沸腾炉及其冷态流动特性试验

在凹型布风板流化床试验台上进行的冷态流动特性试验表明,床内形成了固体颗粒的循环运动,它延长了细颗粒在床内的停留时间。得到了包括表观气速、细粒粒径和密度、床料组分特性和平均粒径、细粒初始浓     

循环流化床内气粒两相传热的萘升华模拟实验研究

在循环流化床试验台上对床中气体与颗粒两相间的传热特性进行了试验研究，试验中首次将萘升华热质类比技术应用于循环流化床内气粒两相间传热的研究中，考察了不同的固体颗粒循环量、一次风风速和床料平均粒径对气粒间换热的影响。试验表明：随着一次风风速的增加，循环床中气体和颗粒之间的表现热换系数变大，当固体颗粒循环量增加或颗粒平均粒径减小时，表征相间换热特性的Nu数增大。图5表1参4     

一种改善循环流化床锅炉性能的方法

循环流化床锅炉出口几何结构对炉内气固两相流动特性和传热有特性很强烈的影响,称为循环流化床锅炉出口端头效应。该文通过试验分析了循环流化床锅炉出口端头效应的机理。结果表明,采用合理的出口几何结构,可以使其具有初级内分离器的功能,进而增强颗粒的内循环,延长颗粒在炉内的停留时间,增强炉内传热,全面改善循环流化床锅炉的性能。     

循环流化床流动特性分析

基于循环流化床 ( CFB)的流动特性 ,提出了一个求解其流动结构的模型。模型综合考虑了床内粒子空间分布的轴向和径向不均匀性 ,可以预测各种运行条件下床内颗粒浓度分布情况 ,并能清楚地表示床的几何尺寸、运行工况对循环流化床流动特性的影响。     

鼓泡流化床宽筛分颗粒气固两相流动的流体动力学

应用颗粒动理学，考虑气体与颗粒、颗粒组分以及组分内颗粒间的相互作用，建立宽筛分颗粒气固两相流双流体计算模型。研究鼓泡流化床内气固两相流体动力特性和颗粒分层的机理。数值模拟结果表明：鼓泡流化床内的流体动力学受颗粒尺寸分布以及颗粒间能量耗散和传递的影响。为了从基本流体动力模型中获得真实的床内气固两相流体动力行为，正确地考虑颗粒尺寸分布及颗粒能量耗散的作用是十分重要的。     

燃煤循环流化床模型与试验研究

利用循环流化床内气－固两相流动等基础方面的研究成果,根据本文床内气固浓－淡流动模型,建立适用不同结构参数的循环流化床燃烧模型,考虑了床内气体、固体颗粒的返混、循环过程,以及煤燃烧、ＮＯ的生成和分解、颗粒磨损等因素。在循环流化床燃烧试验台上进行实验研究,模型仿真结果和实验数据吻合良好,表明气固两相浓－淡流动模型所建立的循环流化床燃烧系统模型可以正确地模拟循环流化床的燃烧过程。     

循环流化床内颗粒运动的PIV测试

作为一种瞬时全场测速技术,PIV测试技术被尝试用于测量循环流化床(CFB)内颗粒运动,以进一步了解循环流化床内复杂的气固两相流动特性。初步实验已在一个截面为200mm×200mm高为4m的冷态循环流化床实验台上完成,并运用二值化互相关图像处理算法,获得了床内截面上的颗粒流动矢量图。初步测试结果较好地反映了循环流化床内颗粒流动的一些特性,表明PIV技术在循环流化床气固两相流体特性研究中具有较好的应用前景。     

300 MW循环流化床锅炉气固流动特性的CPFD模拟

采用计算颗粒流体力学（CPFD）的方法对300 MW循环流化床锅炉内的气固两相流体动力学参数进行全床数值模拟研究,重点分析了循环流化床锅炉炉膛以及回料阀的气固流动特性,获得固相颗粒浓度和速度场在炉膛内的分布以及固体循环流量、系统压力平衡、回料阀的运行情况等锅炉关键参数。结果表明：颗粒浓度的轴向分布呈现明显的密相区和稀相区两部分,模拟得到的轴向压力分布与实际工况吻合较好,验证了CPFD方法模拟循环流化床锅炉的准确性;锅炉回料阀内压降最大,这与床料分布相符;回料阀返料室流化程度较高,而输运室流化程度较小,呈现鼓泡床状态,气泡大都贴壁逃逸。     

大型循环流化床锅炉固体颗粒流动及分布的数值模拟

对引进的４１０ｔ／ｈＰｙｒｏｆｌｏｗ商用循环流化床锅炉燃烧系统固体的流动过程及其分布特性进行了数字模拟,建立的流动模型采用小室模型模拟气固两相沿轴向的流动,采用“核心－环”流动结构模拟气固两相在径向的不均匀性,模拟时考虑了给料,固体颗粒磨损以及床料的宽筛分等特性,为引进大型商用循环流化床锅炉技术的消化吸收进行了初步的基础研究,并为进一步分析研究该循环流化床锅炉的整体特性奠定了基础。     

循环流化床锅炉流体动力学研究

在循环流化床锅炉炉膛内，分为湍流床与快床两个区域。本文论述了由鼓泡流化床和从气力输送状态向循环流化床转化过程中的流体动力学现象。研究了湍流床开始出现到完全转化为湍流床及快床时，炉内气体迅速变化的规律和相应的计算公式。对转化过程中的主要影响因素，如床的当量直径、床的温度以及固体颗粒供给速度等进行了试验研究。     

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.