两级热电热机的有限时间热力学分析

建立了考虑外部传热影响的两级半导体热电热机模型,用有限时间热力学对牛顿传热规律下两级半导体热电热机的性能进行分析,导出了功率、效率与工作电流的一般关系式,得到了两侧换热器的最优面积分配和热电单元数的最优分配,并分析了多种因素对其性能的影响。     

热电发电机驱动热电热泵联合循环热力学分析

建立了新型的热电发电机驱动热电热泵联合循环模型,基于非平衡热力学理论,对装置性能进行分析,导出了供热率、无量纲供热率和供热系数与热电单元比等参数的解析式,研究了该型装置最大供热率和最大供热系数对应的最优工作电流和最优热电单元分配,分析了发电机高温热源温度、热泵供热空间温度等对装置供热率、供热系数、最优工作电流和最优热电单元分配的影响,并给出了不同发电机热源温度下,供热系数与无量纲供热率的关系曲线.     

变工况下热泵供热及膨胀机供热的热力性能对比分析

通过对各设备进行建模,以某300 MW热电联产机组为例,对热泵供热及利用小型膨胀机发电后排汽供热两种方案进行变工况分析。结果表明,对于热泵供热方案,在不同的主蒸汽流量下,都存在一个最佳出口热网水温,使系统煤耗最低;采用热泵最佳参数与膨胀机方案进行变工况对比,发现在采暖抽汽参数较低时,热泵方案的煤耗高于膨胀机方案,随着采暖抽汽参数的增大,当热泵出口最佳热网水温超过70℃时,热泵方案的煤耗开始低于膨胀机方案;同样,在采暖抽汽参数较低时,热泵供热效率比膨胀机方案低,当热泵出口最佳热网水温超过64℃时,热泵方案供热效率开始超过膨胀机方案;提出等效节能量指标,并通过计算表明该指标可用于对比两方案的节能效益。     

基于热泵的耦合供热系统能量综合利用研究

为充分利用热电联产机组供热过程中余热余压，降低供热系统热电耦合度。以大型燃煤机组抽汽供热系统为研究对象，应用Ebsilon软件对供热系统进行数学及热力学建模，对3种不同供热模式下的热电负荷特性进行了多变量耦合下的系统运行参数寻优，得到不同工况下的热电负荷范围。结果表明，应用GOTPR方法明显优于GOTR方法和GPR方法，热泵系统COP最高可提升0.05。直接供热模式的热负荷调节范围是0～400MW,热泵供热模式热负荷调节范围是150MW～550MW,耦合供热模式热负荷调节范围220MW～525MW。在相同的主蒸汽流量下，随着供水温度、回水温度的及热网回水流量的增加，耦合供热模式可提供更大的热电比，同时降低热负荷与电负荷的耦合性。     

吸收式热泵耦合大型抽凝机组供热的经济性分析

针对供热需求与供热能力之间的矛盾和电站低品位冷凝热利用不充分的问题,以300MW抽凝供热机组为实例制定了吸收式热泵耦合抽凝机组供热方案。结合耦合供热方案提出供热面积扩容率的概念,通过对耦合供热与传统热电联产供热两种供热方式的定流量热力计算,以供热面积扩容率、能源综合利用率和热电总收益三个经济性指标为比较标准,进行了经济性指标对比分析。结果表明:耦合供热方式在机组不增容的前提下能够扩大供热面积,提高能源利用率,并增加热电厂的经济收益。     

四热源吸收式热泵的传热面积优化

建立一种不可逆的四温度位吸收式热泵模型，导出其最小传热面积与四热源熵变化率的关系并得到了热力学第二定律的类比表达式，获得了最佳供热率、性能系数和传热面积之间的优化关系，所得结论可为四热源吸收式热泵的优化设计和最佳工况选择提供新的理论途径。     

用热泵机组改造低真空供热系统节能减排分析

分析了热电真空供热系统运行的状况,叙述了在热电凝汽器循环水系统中采用的常规压缩热泵工艺,指出,使用溴化锂热泵比常规泵更经济,节能效果更明显。     

太阳能热泵供热系统的实验研究

开发新能源和节能是寻求能源出路的两大重要途径，太阳能热泵供热系统以其显著的节能性和环保性具有广阔的发展前景。该文简单介绍了太阳能热泵供热系统实验台及实验台测试系统的建设，着重介绍了太阳能热泵冬季供暖工况的实验研究，考察了系统的整体供热性能及主要设备的工作性能。根据实验研究的结果，提出了有关系统设计方面的参考数据。     

电厂循环水水源热泵供热系统的热经济性研究

为研究电厂循环水水源热泵供热系统的热经济性,建立了热泵供热系统计算模型,对循环水水源热泵供热与抽汽供热两种方式进行了热经济性比较,引入单位供热负荷功耗差指标定量表征热泵供热的热经济性,提出了采用循环水水源热泵进行供热的可行性判据。对某200 MW典型机组进行了计算,发现供热温度越低、供热负荷越小、供热抽汽压力越大、制热循环效率越高,电厂采用循环水水源热泵供热的可行性越好。     

热电联产机组热电解耦改造方案的调峰特性及能耗分析

以某电厂330 MW抽汽凝汽式汽轮发电机组为研究对象,计算分析了低压缸切缸、高低压旁路改造、增设储热罐、电锅炉及吸收式热泵5种改造方案对供热机组安全运行可行域及热电解耦能力的影响规律,并采用EBSILON建立案例机组的热力学模型,模拟了各改造方案的能耗状况。结果表明：5种改造方案均可使热电联产机组的安全运行可行域增大,其中两级旁路改造方案的机组最大供热能力增幅最大;除低压缸切缸改造外,其余4种方案的热电解耦能力均有不同程度的提高,其中电锅炉改造方案在电热负荷较低时的热电解耦能力最强;在相同条件下,各改造方案的机组标准煤耗量由高到低分别为电锅炉、两级旁路、低压缸切缸、储热罐和吸收式热泵。     

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.     

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。     

Contents in Volume 23,2014

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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.