应用乳化油时柴油机的燃烧和热效率

从多成份液滴的燃烧机理出发,在柴油机中实验验证了燃烧乳化油时存在着微爆。实验也证明了柴油机性能与乳化油类型(油包水型或水包油型)无关。通过对示功图的分析,验证了柴油机使用乳化油时,热效率正比于燃烧定容度η_(?)和冷却效率η_(?)的乘积,由此提出了柴油机性能的优化方法,并以一个实例说明优化的效果。     

乳化油燃烧与微爆实验研究的现状

文章介绍了乳化油的蒸发,微爆和燃烧机理的实验研究现状,在乳化油的实验过程中,“微爆”的发现和提出“无水层”的概念来解释“微爆”机理具有重要的意义。鉴于乳化油喷雾的特点,为了进行深入的论分析,多脉冲激光全息摄影技术是比较有前途的研究方法。     

柴油混合燃料液滴微爆现象及规律研究

选用甲醇-柴油乳化液滴和正己烷-柴油互溶液滴作为试验对象,采用飞滴式单液滴方法,研究了高温环境下燃油液滴的微爆现象及其规律．通过研究甲醇-柴油乳化液滴和正己烷-柴油互溶液滴的微爆过程,对比了互溶柴油液滴及乳化柴油液滴进行膨胀破碎的差异性,结果发现：互溶燃油液滴可观察到明显的气泡融合过程;相比于互溶燃油液滴,乳化油液滴的破碎发生更早,膨胀速率更快,但膨胀比较小．探究了甲醇体积分数和液滴初始直径对甲醇-柴油乳化油液滴微爆过程的影响发现,甲醇体积分数增加对乳化油液滴微爆起先促进后抑制的作用．随甲醇体积分数的增加,乳化油液滴的破碎时刻先提前后推迟,膨胀比先增大后减小;在甲醇体积分数为30%时,乳化油的微爆效果达到最优．最后对比了两种不同程度的微爆现象发现,整体微爆的膨胀速率和膨胀比均大于局部微爆,发生整体微爆的液滴雾化效果更好．相同条件下液滴发生不同程度微爆的原因是气泡的生成位置不同．     

400号奥里乳化油的应用特性

奥里油的出现，顺应了世界能源结构变化的大趋势，经过近20年的研究和开发，奥里油的生产、储运和应用技术已相当成熟，产量逐步扩大。我国与委内瑞拉国签订了联合开发奥里诺科（Orinoco）油田的协议，在委国合资兴建年产500万吨奥里乳化油生产厂，将使奥里油浆（Orimulsion）（或称奥里乳化油）成为我国一种新型发电燃料。本文对我厂600MW机组锅炉设计使用的400号奥里油的应用特性进行阐述。     

乳化油微爆的统一模型

关于乳化油的微爆在以往的文献中提出过各种计算模型,对油包水与水包油两种乳化油的微爆有不同看法。提出一种油包水与水包油微爆的统一模型并给出了微爆强度的定义,试图对微爆的强弱做定量的描述。通过该模型讨论了一些主要因素,如液滴初始直径,分散相直径及水含量等对微爆强度的影响规律。计算结果表明,该模型的理论预测与实验事实基本一致。另外还讨论了其他因素如添加剂的性质、气体溶解度等的作用。     

乳化油燃烧技术在柴油机中的应用研究

在介绍微爆理论的基础上,就柴油机使用乳化油时微爆作用、水煤气反应和水的蒸发降温作用对柴油机燃烧效率的影响,以及使用乳化油对柴油机NOx的排放和微粒排放的影响作了详细的论述,并指出为使乳化油燃烧技术推广应用,进一步进行微爆效应的理论研究和新型乳化油的研究将是下一步研究的重点。     

柴油乳化液喷雾闪急沸腾与微爆现象的激光阴影试验研究(英文)

在常压定容室内,应用ND:YAG激光阴影法、高分辨率CCD照相机和粒径分析软件,对不同含水量的柴油乳化液雾油滴的闪急沸腾与微爆现象以及油滴粒径分布进行了试验测量与变参数对比分析,探讨了在130℃温度条件下,乳化油含水量对乳化油喷雾液滴闪急沸腾和微爆的影响,揭示了微爆效应在喷雾雾化和液滴碎化中的作用机理.试验结果表明,包覆于油中的水相颗粒受热闪急沸腾所形成的高压蒸气团冲破无水边界层是导致油滴发生微爆和进一步破碎分裂的首要原因;微爆现象随乳化油含水量的增高而趋强;喷雾索特平均直径(SMD)的细化率随乳化油含水量和喷雾贯穿距的增加而增大,且乳化油含水量对喷雾SMD细化率的影响程度也随喷雾贯穿距的增加更加显著.     

多组元液雾在高温高压气体中微爆过程的研究

结合乳化油滴和乳化油喷雾的燃烧微爆机理进行多组元液雾在高温高压气体中微爆过程研究不仅具有重要的理论价值，而且具有广泛的应用前景。     

柴油掺水乳化油雾化特性研究

作者采用高速纹影摄影和同轴激光全息技术，在定容燃烧弹中，从宏观和微观两个角度研究了乳化油束的雾化特性。研究表明，乳化油的雾化特性比纯油好，特别是在高温环境下，乳化油束中发现了单个大油滴“伞状”破碎的雾化现象。作者认为，乳化油中的内相油－水界面的非连接性和高温时水分蒸发汽化对液滴产生的内部扰动，是改善乳化油雾化质量和发生“微爆”的主要因素。     

_水包油_型乳化重油燃烧与排放的实验研究

实验研究了含水30%"水包油"型乳化重油的燃烧与污染物排放特性。燃烧在一维卧式炉上进行,采用专门针对乳化油设计的喷嘴、燃烧器和乳化油加热系统。实验过程中观察了喷嘴雾化和火焰状态,并测量了炉膛内不同剖面的温度分布、氧气浓度分布和NO分布。"水包油"型乳化重油的燃烧实验表明,此类乳化重油完全可以在工业设备上代替柴油使用,对缓解我国的能源形势紧张和环境保护具有重要意义。     

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.