10Cr转子钢的低周疲劳特性试验研究

对国产转子钢14Cr10NiMoWVNbN和国外同种转子钢TOS107的拉伸性能及低周疲劳特性进行了试验研究,将国产和国外转子钢的循环特性、循环应力-应变特性及应变寿命特性进行了对比.结果表明:在室温及600℃下,国产和国外转子钢的拉伸强度无明显差异;国外转子钢的低周疲劳强度略优于国产转子钢.根据593℃下国产转子钢低周疲劳寿命的试验结果,通过虚拟应力转换并选取合适的安全系数,得到了10Cr转子的疲劳设计曲线,该曲线可用于估算10Cr钢制转子的疲劳寿命.     

高效超超临界汽轮机转子钢FB2的低周疲劳特性研究

对再热温度为620℃的高效超超临界机组FB2转子钢的微观组织、拉伸性能进行了研究,采用轴向等幅低循环疲劳试验方法对FB2转子钢在室温和620℃下的低周疲劳性能进行了对比分析,并根据低周疲劳试验结果,建立了FB2转子钢塑性应变能和应变幅与循环周次间的关系。结果表明:FB2转子钢的微观组织为完全回火马氏体结构,有大尺寸BN夹杂析出;转子各取向的拉伸性能均匀,室温下的Rp0.2700 MPa,满足COST522项目要求;低周疲劳条件下表现为循环软化,循环应变-寿命满足Manson-Coffin关系;FB2转子钢的塑性应变能与对应的总应变幅和疲劳寿命在双对数坐标下呈线性关系,该关系可用于估算低周疲劳寿命。     

30Cr2MoV转子钢常温低周疲劳软化规律的实验研究

针对国产200MW机组汽轮机转子上广泛使用的30Cr2MoV钢材料进行了常温下应变控制低周疲劳试验,在试验的基础上研究了30Cr2MoV钢在常温下的循环应力应变特性。得到了该材料的低周疲劳特性参数、循环应力－应变曲线和具有95％置信度,误差限为5％不同存活率下的应变－寿命曲线,并分析了与文献结果存在差异的原因。     

加载速率对3OCr1Mo1V汽轮机转子钢低周疲劳特性的影响

以30Cr1MolV汽轮机转子钢为研究材料,选取0.1%/s、0.3%/s和0.5%/s的加载速率,采用控制总应变的方法,在RDL 05电子蠕变疲劳试验机上研究了加载速率对材料低周疲劳特性的影响.同时,还提出在538℃下加载速率对30Cr1Mo1V汽轮机转子钢应力和低周疲劳寿命影响的关系式以及低周疲劳寿命与总应变幅值的关系式.结果表明:在538℃时,随着加载速率的提高,转子钢循环应力增大,低周疲劳寿命延长;在同一应变下,加载速率越大,所对应的应力幅值越大;随着应变幅值的增大,应力增大,低周疲劳寿命缩短.     

超超临界汽轮机转子蠕变对低周疲劳应变的影响

对某超超临界汽轮机高压转子多次启停和间隔分段稳态高温运行下的低周疲劳应变进行了全时域连续有限元计算与分析,给出了蠕变条件下低周疲劳应变的变化量级和变化图谱.结果表明:超超临界汽轮机转子低周疲劳寿命消耗需进行全时域连续计算,不能采用一次启停数据乘以启停次数的简单算法;蠕变对低周疲劳产生的影响具有长期性,但影响程度随时间逐步递减.     

30Cr1Mo1V转子钢低周疲劳性能及损伤演变规律研究

对３０Ｃｒ１Ｍｏ１Ｖ转子钢进行３组不同温度的低周疲劳试验，分析了该转子钢低周疲劳特性，给出了应变——寿命关系式，讨论了该转子钢的循环特性，推导了该转子钢在各个温度下的应变疲劳损伤演变方程和寿命估算方程。     

基于有限元分析的汽轮机转子低周疲劳损耗研究

采用有限元法建立了基于某电厂汽轮机转子温度场和热应力场的数学模型。在对汽轮机的冷态启动、温态启动、热态启动以及滑参数停机4个工况下的瞬态温度场以及热应力场进行模拟分析基础上,确定转子最大热应力点作为监测点,对监测部位的温度与热应力进行了疲劳损耗仿真计算。根据最小二乘法获得转子钢材料的疲劳特性曲线,利用MATLAB进行多项式拟合,获得转子应变与疲劳寿命损耗的函数关系式,求得汽轮机转子启停下的低周疲劳寿命。研究结果表明:该机组累积十年运行条件下形成的疲劳损耗为2. 506%。机组冷态启动过程中,转子承受最大温差与热应力,最大热应力值445 MPa;当温升率由3℃/min提高到4℃/min时,转子的低周疲劳寿命损耗由0. 040%上升到0. 103%,寿命损耗明显增大。     

核电低压转子钢30Cr2Ni4MoV低周疲劳性能研究

对30Cr2Ni4MoV进行了拉伸试验和低周疲劳试验,对30Cr2Ni4MoV的拉伸性能进行了分析,得到了大直径转子不同部位力学性能的分布特征和30Cr2Ni4MoV的塑性模量。采用应变控制对30Cr2Ni4MoV进行不同应变幅的低周疲劳试验,结果表明,30Cr2Ni4MoV有明显的循环软化特征,30Cr2Ni4MoV转子钢的芯部与表面低周疲劳性能体现出较好的一致性,并拟合得到该材料Manson-Coffin公式与应变-寿命三参数公式。两种拟合公式都能较好地拟合原始数据,应变-寿命三参数公式能更好地反映材料高周疲劳性能。     

30Cr2MoV转子钢高温低周疲劳性能研究

通过对３０Ｃｒ２ＭｏＶ钢汽轮机转子进行不同温度的应变控制下低周疲劳试验，给出了该材料在不同温度下的循环稳定应力－应变曲线，应变－寿命关系，应力－寿命关系，并在疲劳数据服从对数正态分布的假定基础上，给出了具有９５．４％置信度的下限应变－寿命方程，试验材料取自多个不同的２００ＭＷ机组的供货转子，数据结果具有比较广泛的代表性，对于汽轮机转子的设计和寿命估算具有一定的实际应用价值。     

高参数汽轮机转子启停机疲劳损伤分析

借助数据分析和有限元模拟计算,研究了高参数超超临界汽轮机高压转子在启动和停机过程中的低周疲劳寿命损耗。通过分析现场实测数据,并据此进行有限元模拟,总结出高压转子在机组极冷态启动和常规滑参数停机过程中的热应力分布规律,确定转子的危险区域,并得到危险点的应力在机组启停中的变化规律。结合材料的疲劳特性,计算出转子在一次实际启停循环中的低周疲劳寿命损耗,为今后机组的运行提出建议,为高参数超超临界汽轮机转子的设计及运行控制提供参考和借鉴。     

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。     

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.