一类有限热源多级连续卡诺热机系统的最大输出功

对高低温热源均为有限热源的多级连续卡诺热机系统最大输出功的最优温度曲线进行了研究,利用最优控制理论得出了其最优温度曲线为驱动流体温度随流速和过程时间成指数变化,求出了其最大输出功,并与低温热源为无限热源下的结果进行了比较。     

辐射传热定律下外燃机最大输出功优化

以活塞式外燃机为研究对象,考虑工质与外热槽间传热服从辐射传热定律[q∝△(T4)],以循环输出功最大为优化目标进行了优化。给出了辐射传热定律下的数值算例,并与牛顿传热定律下的结果进行了比较。结果表明,热导率增加,最优完全循环和半循环的输出功和效率均减小,与完全循环相比,最优半循环的压缩比、输出功和效率较大;结果还说明虽然两种传热定律下最优完全循环和最优半循环的欧拉-拉格朗日(E-L)弧部分的工质体积随时间的变化曲线均类似于正弦曲线,并且均由3部分组成,但不同传热定律下工质体积随时间的变化曲线是不相同的。     

中低温地热发电有机朗肯循环工质筛选

针对进口温度为423.15 K的中低温地热驱动有机朗肯循环发电系统,采用与热源耦合的反问题方法,选取干工质与等熵工质共6种、湿工质6种,在回灌温度为333.15～353.15 K时进行计算比较,分析了地热水回灌温度对不同临界温度、不同干度工质循环性能的影响,进而筛选出最优工质。分析结果表明,在地热水进口温度为423.15 K条件下,随着回灌温度逐渐升高,大多数工质的净输出功呈先升高后降低的趋势;对相同类型工质进行比较,工质临界温度越高,其最大净输出功越低,且最佳回灌温度越高;湿工质在微过热循环(膨胀机出口为饱和汽态)下与干工质饱和循环最大净输出功相当。综合考虑工质循环性能、环境影响、毒性及易燃性,确定最优工质为R236fa。     

地热源双级喷射有机闪蒸循环热力分析及优化

为有效利用有机闪蒸循环（OFC）闪蒸后的饱和液态工质，提高中低温热源的回收效率，构建地热水驱动的双级喷射有机闪蒸循环（DEOFC）系统，探究关键参数对系统的影响，并对系统进行多目标优化。结果表明：DEOFC闪蒸压力和高压膨胀机出口压力最优时，热源温度升高，系统净输出功、热效率、效率增大；当温度升至工质的特征温度时，趋势发生变化。多目标优化时，R601a表现出最佳性能。与单级喷射有机闪蒸循环（SEOFC）相比，DEOFC净输出功和效率均存在较大优势。     

线性唯象传热规律下复杂系统的热力学优化

实际传热过程并不总是服从牛顿传热规律,传热规律对循环性能有很大影响.利用非平衡热力学中常用的传热规律--线性唯象传热规律,对复杂系统进行了研究.该复杂系统包括若干不同温度的热源、有限热容子系统和一个变换器(热机或制冷机).利用拉格朗日方程得到了变换器的工质最优温度和子系统的最优自由温度,求出了系统相应的最大功率输出,并与牛顿传热规律下的结果进行了比较,计算方法为计算实际复杂系统的温度分布和能量界限提供了一种途径.     

基于工质临界温度的带内回热ORC系统性能分析

为充分回收低温烟气余热,建立带有内回热的有机朗肯循环系统。选取硅氧烷类、HC类与HFC类共9种有机工质,基于工质临界温度与工质复杂度因子,讨论净输出功与质量流量变化规律;提出采用液态吸热系数、潜热系数、内回热吸热系数对ORC系统循环热效率的变化规律进行分析。结果表明:随蒸发温度的升高,热效率与效率升高,质量流量与损下降,而净输出功先升高后降低。对同种类型工质,临界温度越高,净输出功越低;对不同类型工质,单位工质做功能力表现为HC类硅氧烷HFC类,且对于不同类型工质影响工质质量流量的因素不同。对不同工质而言,工质临界温度越高,热效率与效率越大,净输出功越小,热源匹配性变差。综合考虑以上因素,所选工质临界温度不宜超出热源温度过多。     

分液冷凝有机朗肯循环系统R245fa/HFOs工质选择研究

有机朗肯循环是中低品位热能高效利用的有效技术之一,分液冷凝有机朗肯循环（LSCORC）是基于分液冷凝传热强化的新型热力循环。为寻找新型环保替代工质,建立LSCORC系统的热力学模型,以最大化净输出功为目标,重点考虑了雅各布数、冷热源换热匹配对系统性能的影响,对R245fa/HFOs工质进行了对比筛选。结果表明：工质的雅各布数越大,其净输出功越小;在基础工况下,R245fa/R1336mzz(Z)的热力性能及热经济性表现最佳;当热源参数变化时,雅各布数较小工质的性能表现普遍优于雅各布数较大的工质组合;当冷源参数变化时,在分液冷凝器两个流程中温度滑移和冷源温升匹配越好的工质组合,其系统净输出功越大。     

中低温热水发电系统循环参数和工质的选择

针对热源为80～150℃热水的有机朗肯循环（ORC）发电系统,以发电功率和效率为评价指标,分别分析了以R134a、R123和R245fa三种工质为循环介质时的系统,确定了最佳循环参数和工质。一般来说,最佳蒸发温度对应着最大的输出电功,且随着热流体温度的升高而升高;当热源温度大于120℃时,R134a的系统不存在最佳蒸发温度,此时输出电功随着蒸发温度的升高而增大。对于80～135℃的热水,工质R245fa的发电功率最大;当热水温度超过135℃时,工质R134a的发电功率最大。工质R245fa的发电效率始终是最大的。     

低温地热有机朗肯循环(ORC)工质选择

对低温(60～150℃)地热有机朗肯循环(ORC)系统,以净输出电功和系统能量损失作为评价指标,分析不同地热流体温度下有机工质R290,R134a,R600a,R600,R601a的做功能力,确定最佳循环工质.分析结果表明:对于湿流体工质,由于临界温度较低,当地热流体温度高于其临界温度20℃时,不存在最佳蒸发温度:对于60～80℃的地热流体,工质R601a的最大净输出电功最大;对于90～120℃的地热流体,工质R134a的最大净输出电功最大;对于125～150℃的地热流体,工质R290的净输出电功最大.这些结果为中低温地热利用提供设计依据.     

二热源机的全息热效率与利润率谱

1、内可逆卡诺热机的最佳热效率、利润率谱考虑工作于T_H、T_L热源的内可逆卡诺热机,设工质与高、低温热源间的传热系数分别为α、β,工质与热源间的传热服从牛顿定律,则工质的吸、放热量为     

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.