分置式斯特林发动机热力性能的仿真

对斯特林发动机的压缩与膨胀过程进行了变质量系统热力学分析。利用等温模型分析法,引入流动阻力损失的计算模型,模拟了分置式斯特林发动机内部工质的压力等参数的动态变化规律。仿真结果表明：斯特林发动机在运行过程中压缩腔与膨胀腔的气体压力并不时时相等;提高发动机的转速和高温热源温度,可以增加发动机的输出功率。     

碟式斯特林太阳能发电系统研究

设计了斯特林太阳能发电系统,构建了斯特林系统模型,并以此模型进行了发电系统仿真研究,结果表明,太阳能发电系统的发电效率变化处于持续平稳状态,而输出功率则与太阳直射强度变化状态相类似;系统热端温度基于太阳直射强度变大且超出设定值状态时,开启充气阀,则工质循环压力上升,而发动机转速不变时,发动机热端温度则呈现下降趋势;短时...     

基于斯特林循环的汽油机尾气余热回收系统设计与试验研究

建立了基于斯特林循环的汽油机尾气余热回收的试验及数据采集系统以提高汽油机能量利用率。针对2.0DCVVT汽油机某一常用转速下,低、中、高负荷下进行试验,确定了斯特林机转速与输出电压及转速与负载电阻之间的线性关系,便于循环系统工作过程中负载电阻的选取及斯特林机转速的控制。试验结果表明:斯特林机输出功率随着斯特林机转速呈先增大后减小的趋势,斯特林机在工作过程中存在最佳工作转速,且最佳工作转速随着工质压力的升高逐渐增大;在汽油机3 000r/min、90%负荷下,工质压力为1.4MPa时斯特林机输出功率最大达到254W;对应斯特林机转速为810r/min,汽油机尾气排气温度由720℃降为415℃,系统回收功率相当于汽油机功率的0.62%,而在30%负荷时回收功率可以达到汽油机功率的1.03%。     

斯特林发动机瞬态模型及特性分析

为获得斯特林发动机的动态特性和优化方案,将损失机制和压力梯度耦合进控制方程中,提出一维瞬态斯特林循环分析模型及分析方法,并针对GPU-3斯特林发动机进行模型验证和特性分析.模型的指示功率相对误差平均值约为4.8％,热效率的相对误差小于1％.当氦气工质在热源温度为977 K、平均压强为2.76 MPa时,输出功率随转速的...     

一种β型三曲拐斯特林发动机的建模与仿真

斯特林发动机作为一种外部燃烧的发动机,具有燃料来源广、污染小、噪声低和维修方便等优点,对节能与环保具有积极的意义,而其中的β型斯特林发动机更是具有体积小、传动平稳、易于密封等优点,具有广泛的应用前景。本文针对一款β型三曲拐闭式循环斯特林发动机,进行了工作过程数学建模、运用simulink软件进行仿真,根据仿真与分析结果,得到了不同气体工质功率输出与热效率随转速变化的规律。结果表明,在斯特林发动机不同转速运行范围内,应采用不同的气体作为工质,才能获得较高的功率输出与热效率。     

菱形传动斯特林发动机的相似设计及实验研究

重点研究基于相似方法的菱形传动斯特林发动机各关键参数设计以及实验台架搭建,并通过电加热系统模拟外部热源进行热力性能测试。实验过程中记录斯特林发动机的运行温度、充气压力、转速以及输出轴功率等性能参数。根据实验结果对影响斯特林发动机输出特性的参数进行分析,得到实验样机在工作温度为600℃,充气压力1.5 MPa时的最佳输出功率为289 W。     

运行调节方式对斯特林发电装置性能的影响分析

碟式斯特林发电系统是一种新型的具有广阔应用前景的新能源动力系统,其性能研究和开发利用受到世界许多国家的重视。本文以等温模型为基础,考虑各部件中工质流动损失、热损失,对20 k W级碟式太阳能聚光器双作用斯特林发电系统在两种不同运行调节方式下的性能进行模拟计算。结果显示:无论从发电量、发电功率、发电效率大小及波动性,还是运行调节参数的波动性、控制性等方面考虑,压力调节运行方式均优于温度调节运行方式。     

Thermal Economy Analysis of Steam-Organic Fluid Combined Cycle Power Generation Model Based on Different Working Fluids

以NZK660-24.2/566/566机组为例,建立了可减少汽轮机冷源热量、增加发电量的蒸汽-有机工质联合循环发电模型.为了筛选出适合新模型的工质,根据工质性质设定新模型的运行参数,通过采用排汽温度为55.3℃及35℃的原机组及新模型的热经济性指标对9种有机工质的热力性能进行了分析.结果表明：与原机组在排汽温度为35℃时相比,当机组热耗相同时,新模型的发电热效率提高,不同工质的发电效率提高幅度不同,而且空冷面积变小;随着工质临界温度的升高,低压缸2的进口压力和排汽压力呈下降趋势;新模型采用环保工质R365MFC时,低压缸2的进、出口压力较为适宜,且排汽未通过湿蒸汽区,可获得较高的热效率.     

曲柄转角对太阳能斯特林发动机性能的影响

基于斯特林发动机理想绝热分析法,对GPU-3β型斯特林发动机内部交变流动和换热过程进行数值模拟,获得不同腔体压力、容积、质量流量、循环功等参数的变化规律。结果表明:随着曲柄转角θ逐渐增大,工质的压力、容积曲线呈现先减小后增大的变化趋势,当θ=150°时,膨胀腔温度T_e和压缩腔温度T_c均达到最大值:1024 K和450 K;当θ=90°时,回热腔内换热量Q_r达到最大值为650 J;膨胀腔循环功W_e与总循环功W的变化趋势一致,呈现正弦规律变化。对比理想绝热模型与Schmidt模型,表明绝热模型能真实反映斯特林发动机中工质热流规律。采用多目标遗传算法对循环功和无因次功进行优化,获得最优解集为60 kW和1.44。     

太阳能斯特林发动机的性能模拟

太阳能盘式聚光器和斯特林发动机能够很好地结合成为一种新型的具有广阔应用前景的动力系统，其性能研究和开发利用受到世界许多国家的重视。该文以等温模型为基础，考虑各部件中的工质流动损失、导热损失及活塞的穿梭和泵气热损失等，对一个低压无转速调节装置的盘式聚光器—斯特林发动机在一典型晴天日照下的一天中热性能进行模拟。结果显示；早晨接收器的温度随太阳辐射的增加迅速上升，输出功率和系统效率也快速增加，而后接收器的温度基本处于恒定，因而膨胀腔的膨胀功不变，接受器接收太阳辐射的增加使斯特林发动机的转速上升。流动阻力及各种热损失占膨胀功的比例随转速的升高越来越大，在上午10～12点时，输出功率又略有下降，而下午又正相反。因此，一天中的系统效率曲线呈一马鞍形。此外，结果也显示，提高发动机的工质压力。系统效率也将升高。     

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.