地热热泵循环工质的开发及系统匹配

通过实验方法开发中高温地热热泵工质．该工况要求是：冷凝温度80～100℃，蒸发温度25～35℃，同时保持系统内最高压力不超过2500kPa。实验表明非共沸工质R123/R290(质量百分比50％／50％)和R123／R290／R600a(质量百分比40％／50％／10％)能满足上述条件，且系统的COP在3．0以上。     

自然工质复叠式制冷热泵系统的性能分析

介绍了以自然工质CO2为高温循环工质,R290为低温循环工质,同时制冷和供热的CO2/R290复叠式制冷热泵系统,通过对CO2/R290复叠式制冷热泵系统的性能分析,得到了气体冷却器的入口压力和出口温度,复叠式循环的蒸发温度,低温循环的冷凝温度对复叠式制冷热泵系统性能的影响,为今后的CO2/R290复叠式制冷热泵系统的优化设计和开发应用打下了一定的基础。     

中高温热泵混合工质R13I1/R290/R600a替代R134a的理论研究

针对普通R134a热泵制取中高温热水过程中存在的冷凝压力过高、系统效率低、不环保及无法直接替代等问题,提出一种新型中高温热泵混合工质R13I1/R290/R600a。建立基于该工质的热力循环模型,计算该循环的热力特性。结合气象数据,对其进行多工况计算并与已有的工质R134a、MIX1和MIX2对比分析。研究结果表明该新型混合工质的循环性能与同模型常温热泵工况下R134a的循环性质大致相同,且其环境性能优良:ODP为零,GWP小于20,温度滑移小于4℃。单位容积制热量略低于R134a,分别比MIX1和MIX2平均高16.7%、1.3%;COP分别比R134a、MIX1和MIX2平均高9.2%、4.1%和0.7%。综合循环性能较对比工质更优越,适用于冷凝温度为70～90℃,循环温升低于75℃的热泵工况。     

用于高温热泵蒸汽系统的几种工质的循环性能

建立了高温热泵蒸汽系统的热力学模型。在蒸发温度为60℃,冷凝温度为120~140℃的工况下,进行经过初步筛选的4种高温热泵纯工质(R123,R141b,R245ca,R245fa)和传统高温热泵工质(R114)的循环性能对比研究。结果表明:R245fa的综合循环性能良好,单位容积制热量最高,其性能系数(COP)比R114平均高13.65%,压缩比与R114最接近;在符合干压缩要求的前提下,排气温度较低,而且环境友好,可作为高温热泵蒸汽系统的工质。     

R404A在低温空气源热泵中替代传统工质的性能研究

基于制冷剂物性软件Cool Pack,通过计算对R404A、R22、R407C、R410A在螺杆式单级压缩热泵系统理论循环中的制热量、排气温度、压缩比、压缩机功耗、COP、质量流量进行了对比分析,系统工况设定为冷凝温度50℃,蒸发温度在-40~10℃范围内变化。计算结果表明:R404A作为低温空气源热泵系统的工质具有稳定的低温适应性。     

二氧化碳/丙烷用于热泵系统循环性能分析

在热泵热水器名义工况条件下,对二氧化碳(R744)/丙烷(R290)自然混合工质与四种常见的热泵工质R22、R134a、R410A和R407C的亚临界循环性能进行了分析对比。结果表明:R744/R290的最优质量配比为21/79,系统的制热循环性能系数(COPh)比R22系统提高了10.46%、比R134a系统提高了22.67%、比R410A系统提高了11.93%、比R407C系统提高了9.52%;在10%~35%、0%~35%、10%~35%和10%~35%的R744质量配比内,R744/R290可分别实现对四种常见热泵工质的替代;在最优质量配比下,R744/R290系统的冷凝压力低于R410A系统,压比仅为3.271,排气温度为80.9℃。     

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.     

二氧化碳/二甲醚混合工质热泵系统循环性能分析

在相同的工况条件下,对二氧化碳(R744)/二甲醚(RE170)混合工质与四种常见的热泵工质R22、R134a、R410A和R407C的亚临界循环性能进行了分析计算。结果发现,在R744/RE170质量配比为30/70下,系统的制热循环性能系数最大,其值为4.922,分别比R22、R134a、R410A和R407C系统提高了17.53%、30.52%、19.09%和16.52%;此时,系统的冷凝压力为2.276MPa仅高于R134a系统,压缩机压比为3.708,压缩机出口工质排气温度为92.6℃。     

HFC245fa用于高温热泵系统的循环性能评价

以寻求冷凝温度为80～110℃的高温热泵工况范围内的适用工质为目的,对臭氧破坏势COP为零、温室效应势GWP较低的工质HFC245fa进行了循环性能理论和实验研究。结果表明,HFC245fa的理论循环性能优于传统工质CFC114;在实验工况范围内,HFC245fa系统的实际循环性能随运行工况温度的提高而提高。实验中,系统的热输出温度达到了102℃。     

不同工况下非共沸混合工质有机朗肯循环系统性能研究

采用MATLAB软件模拟非共沸混合工质在不同冷热源条件下对有机朗肯循环(ORC)系统性能的影响。选取R245fa/R1234ze和R245fa/R600a作为混合工质,热源温度取120和200℃,分别在冷凝露点温度为40℃和冷却水温升为5,10,15℃的工况条件下,利用热力学第一定律和火积理论对系统性能进行分析。结果表明：热源温度为200℃时,R245fa, R1234ze和R600a系统净输出功率分别为89.83,61.87和77.74 kW,使用R245fa系统性能优于其混合工质;热源温度为120℃、固定冷凝露点温度时,混合工质R245fa/R600a(90%∶10%)净输出功率比R245fa和R600a分别提高了27.6%和27%,R245fa/R1234ze(60%∶40%)净输出功率比R245fa和R600a分别提高了26%和20.5%;火积耗散和单位面积做功量与净输出功率变化相反,提高冷却水温升时,增大了系统火积耗散,且流向环境中的火积耗散在总火积耗散中占比增大,导致系统的传热不可逆损失增加。     

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.