T92钢管长时高温组织稳定性及性能研究

对国产T92钢管进行了650℃高温时效试验、蠕变断裂试验和组织研究.结果表明:经650℃高温时效和蠕变断裂试验后,3种现象同步发生,即位错密度下降、亚晶粒数量增加以及析出相的演变;M23C6型碳化物的迅速粗化长大以及Laves相的析出与粗化主要出现在3 000 h附近;在3 000 10 000 h时效过程中,M23C6型碳化物的长大速率并不明显,形态较稳定,这与Laves相从基体中析出并迅速粗化有关;经10 000 h时效后,T92钢管仍然保持稳定的马氏体板条形态,但蠕变断裂试验后,部分板条马氏体开始向等轴亚晶转变.     

620℃高效超超临界机组用FB2钢高温持久过程组织演变分析

为研究长期服役过程中FB2钢组织的变化规律,在620℃下对FB2钢进行高温持久试验,并对持久试样进行微观组织观察,分析其组织及析出相的演变规律.结果 表明:在高温持久过程中,FB2钢的组织仍为回火马氏体;随着持久时间的增加,马氏体组织发生回复,板条略微变宽,位错密度略减小;M23C6碳化物尺寸未发生明显粗化,持久时间达...     

HR3C钢内压蠕变试验后显微组织与力学性能试验研究

研究了HR3C钢管试样在不同内压蠕变试验时间下显微组织和力学性能的变化,分析了HR3C钢析出相对力学性能的影响.结果表明:内压蠕变试验后,HR3C钢管试样晶内和晶界上均析出弥散分布的NbCrN相,此外M23C6碳化物在晶界形成连续链状分布,并随着试验时间的延长发生聚集和粗化,M23C6碳化物在晶内析出弥散分布的方形颗粒,在孪晶界以长板状析出;弥散分布的NbCrN相和M23C6碳化物以及晶界连续分布的M23 C6碳化物产生弥散强化和晶界强化,导致内压蠕变试验后HR3C钢的强度和硬度均明显增大,随着试验时间的延长,不断聚集的M23C6碳化物弱化了晶界强化效果,使得HR3C钢抗拉强度略有下降;内压蠕变试验后,晶界连续分布的M23C6碳化物导致HR3C钢室温下冲击吸收功和断后伸长率明显减小.     

一种含Re超超临界汽轮机叶片钢的应用性能研究

11Cr10Co2W2MoReVNbNB钢是一种含Re的超超临界汽轮机高温叶片用钢,使用温度高达630℃,也就是电站铁素体钢的使用温度极限。通过试验研究11Cr10Co2W2MoReVNbNB钢的高温瞬时拉伸性能、长期组织稳定性等应用性能,并介绍了各种应用性能的理论基础和钢的强化机理。试验结果表明:(1)随温度升高,钢的强度逐渐降低,在低温阶段塑性略有上升,在中温阶段塑性最差,进入高温阶段后塑性大幅升高;(2)经670℃、400h时效后,钢中M23C6等强化相的尺寸有所长大,但仍具有良好的高温拉伸性能,说明钢具有良好的组织稳定性;(3)钢主要通过弥散分布的颗粒状细小析出物M23C6相强化,Re主要存在于基体中,起固溶强化作用。试验证明11Cr10Co2W2MoReVNbNB钢是一种理想的高参数、大容量超超临界汽轮机高温叶片材料。     

长期服役的12%Cr马氏体耐热钢中的碳化物及其变化

以X20CrMoV12.1耐热合金钢管为研究对象,重点研究了管道材料的显微结构变化,特别是碳化物沉淀相的形态和成分变化,探讨了材料性能变化的微观原因.结果表明:12%Cr耐热合金钢主蒸汽管线在550℃高温条件下经180 000 h长期服役后,材料的组织结构发生明显变化,出现马氏体分解,形成板条亚晶结构,表现出典型的蠕变特征;合金碳化物沉淀相大多分布于晶界和板条亚晶界,且相对于原始态粗化严重;晶界和亚晶界分布的碳化结构是M23C6,晶内相对细小的碳化物结构也大多数是M23C6,另有少量方形片状的富V碳化物MX;M23C6碳化物中合金含量随服役时间的延长明显富集,且分布在不同区域的碳化物不仅形态不同,其化学成分也存在明显差异.长期服役过程中碳化物产生这些演变现象与碳化物的粗化进程相关,并受热力学条件和扩散方式的影响.     

先进超超临界机组用候选材料Alloy 263的组织稳定性

对用于先进超超临界机组锅炉的候选高温合金Alloy 263在固溶处理、沉淀硬化处理和750℃时效3 000 h过程的组织演变行为进行了研究并分析了其组织的稳定性.结果表明：在固溶处理状态下的Alloy 263组织晶粒度为4~5级,较多的一次（Ti、Mo）C弥散分布于γ基体上,且γ′相形核于晶内;沉淀硬化处理主要在晶内共格析出颗粒状γ′相,在晶界析出大量的M23C6;在750℃长期时效条件下,γ′相发生Ostwald熟化,且与基体的错配度增加,M23C6和MC继续析出与长大;在时效1 000 h下基本处于稳定状态,当时效为3 000 h时,有针状η相生成;高温合金Alloy263在750℃下具有良好的组织稳定性.     

620℃汽轮机用CB2钢高温时效过程组织与析出相演变分析

为获得长时服役过程中CB2钢的组织演变规律和老化特征,研究了CB2钢在620℃高温时效过程中显微组织和析出相的演变行为。结果表明：CB2钢在高温时效过程中显微组织仍为回火马氏体,板条形态清晰、位错密度未见明显下降,组织稳定性良好,供货态中析出的M₂₃C₆碳化物大量弥散分布在马氏体板条边界、原奥氏体晶界,在时效过程中尺寸无明显增大,时效8000h后仍在200nm以内,这是CB2钢保持良好高温强度的重要原因。CB2钢高温时效过程中微观组织的变化主要表现为Laves相的析出和长大,它依附于M₂₃C₆碳化物优先形核析出并以吞噬机制长大,随时间延长颗粒尺寸呈线性增大、不断粗化,这是造成CB2钢时效脆化的重要原因。     

620℃汽轮机转子13Cr9Mo2Co1NiVNbNB钢的组织稳定性分析

对620℃汽轮机转子锻件(13Cr9Mo2Co1NiVNbNB)进行高温持久考核,并采用光学显微镜(OM)、场发射扫描电镜(FESEM)和透射电子显微镜(TEM)对高温持久试验后的试样和原始试样进行了微观组织对比,分析了高温持久试样的组织稳定性。结果表明,B元素在初生奥氏体晶界聚集,进入M23C6碳化物中替代C形成M23(C,B)6,并限制M23(C,B)6的长大。持久试样的组织由板条马氏体+M23C6碳化物+MX相组成,马氏体板条宽度略有增大,M23C6碳化物密度显著提高,分布更加弥散,其尺寸也略有增加。马氏体板条内形成位错胞亚晶,细小的MX相沿位错胞亚晶边界析出,对提高材料蠕变强度作用明显。     

IN625合金76O℃时效析出相对冲击性能的影响

研究了IN 625合金在760℃时效过程中组织结构变化及其对室温冲击性能的影响,并利用光学、扫描和透射电镜对时效前后的合金组织结构和冲击断口进行了观察与分析.结果表明:该合金在时效过程中,析出相有M23C6、γ′和γ＂;M23C6主要沿晶界分布,晶内分布较少,γ″相垂直于晶界方向析出,γ′颗粒分布于晶内;长时间时效对晶内M23C6和γ′相影响小,但导致晶界M23C6相聚集长大,γ＂相沿长度方向长大且数量明显增多;时效后,冲击吸收能量明显降低,断裂模式由韧性断裂转变为脆性断裂.     

IN625合金760℃时效析出相对冲击性能的影响

研究了IN 625合金在760℃时效过程中组织结构变化及其对室温冲击性能的影响,并利用光学、扫描和透射电镜对时效前后的合金组织结构和冲击断口进行了观察与分析.结果表明:该合金在时效过程中,析出相有M23C6、γ′和γ″;M23C6主要沿晶界分布,晶内分布较少,γ″相垂直于晶界方向析出,γ′颗粒分布于晶内;长时间时效对晶内M23C6和γ′相影响小,但导致晶界M23C6相聚集长大,γ″相沿长度方向长大且数量明显增多;时效后,冲击吸收能量明显降低,断裂模式由韧性断裂转变为脆性断裂.     

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.     

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.     

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.