基于绩效评价的水利水电工程战略合作分包商选择

随着我国水利水电建设投资的不断扩大,对工程建设的要求亦不断提高,其中水利分包商的施工绿色程度及质量决定着整个工程目标的实现,因此与高品质分包商进行战略合作是实现目标的关键。通过分包商的绩效评价来选择战略合作分包商,即先参考鲁班奖评选标准,建立以绿色施工、高质量施工为准则的高品质分包商绩效评价指标体系;然后建立基于G1法和物元可拓模型的分包商绩效评价模型,对其工作绩效进行评价,将评价等级为良好及以上的分包商选入战略合作体系。实例分析表明,评价模型有效可行,为水利水电工程战略分包商的选择及绿色高品质工程建设提供了参考依据。     

基于Matlab的水利工程材料库存优化研究

水利工程材料的库存管理是水利工程材料管理的重要环节。针对水利工程材料的库存优化问题,考虑基于提前期的价格折扣策略及仓库容量有限的约束条件,假定经结构分解后的每道工序在正常条件下所需资源均衡,所耗材料速度均匀且供应商材料生产速率一定,以材料供应商和施工承包商的综合库存成本最小构建目标函数,建立数学模型,基于Matlab优化工具箱,运用粒子群算法求解联合库存系统成本最小值,确定最优订购策略。研究成果对水利工程材料采购方案的制定及水利工程项目的材料库存管理有指导意义。     

EPC总承包商费用控制的重要性分析

EPC项目下总承包商负责项目非设计、采购、施工直至交付全过程,需要协调多方开展项目,其费用控制难度大、风险高。分析了EPC总承包商的费用控制困境,并提出了费用控制的原则、方法及关键点,从招投标阶段、分包及设备采购阶段、设计阶段、施工阶段、工程结算阶段分析费用控制的重点内容。     

水务工程风险管理

加入世界贸易组织后,我国水务工程风险管理水平有待进一步的提高,目前我国在风险管理中使用的风险控制方法还仅停留在将风险简单、单纯的转移给承包商或分包商,这对于处理将建设项目中有可能遇到的风险还远远不够,这就需要引进国外的一些先进的风险控制方法,对加强我国在水务工程建设项目的风险控制有着极为重要意义.     

EPC总承包模式下质量管理的探索和实践

以设计为龙头的EPC总承包模式目前已被国内一些企业逐步接受,这种模式下工程建设的施工调试是通过分包完成的．总承包商如何做好施工和调试分包阶段的质量管理,成为EPC项目管理的新课题,结合我公司脱硫工程实践,按PDCA循环法对EPC总承包质量管理进行了探索。     

基于总承包商角度水电工程EPC项目设计管理研究

针对水电工程EPC项目设计管理存在的问题,基于总承包商角度探讨了EPC项目设计质量管理,建立了EPC项目设计管理集成模式,并构建了有效设计管理体系,为完善EPC项目总承包商设计质量控制机制提供了依据。     

基于二层决策系统的工程项目支付进度优化

针对工程项目建设时期业主和承包商在支付进度方面可能的利益冲突问题,分析了业主和承包商在项目组织层级上的纵向主从关系.构建了业主和承包商双方净现值最大化的二层决策系统数学模型,并借鉴多目标优化思想设计了基于Pareto和向量评价的微粒群算法,通过编写Matlab程序实现了模型的求解.实例计算结果表明,采用VEPSO-BP算法能获得多种工程施工进度计划方案和相应工程款支付方案,业主和承包商可根据双方利益选取共赢方案以安排项目进度计划.     

高墩翻模施工技术及施工测量控制

随着我国公路交通事业的迅猛发展,公路高墩连续桥已在桥梁工程领域广泛应用,其施工工艺和施工测量方法也在不断提高,老庄河特大桥建设实践中的高墩翻模及控制测量对工程建设的质量保证和技术控制均取得了满意效果,提高了工程建设质量,加快了工程进度.     

基于改进的ANP的国际水利工程投标决策

为帮助承包商面对多个投标机会进行投标选择,采用网络分析法(ANP)建立多层次的国际水利工程承包投标决策模型,分析了投标决策的主要影响指标,并将三角模糊数引入到模型的求解过程,增加了评估的准确性。以某施工企业选择A、B、C三个项目之一进行投标为例进行计算,结果表明改进的ANP模型为国际承包商投标决策提供了一种更准确的有效方法。     

水电工程EPC项目总承包商全面风险管理研究

从EPC总承包模式的特点出发,介绍了EPC项目风险的特点,阐述了全面风险管理的内涵,从总承包商的视角利用全面风险管理理论分类分析了总承包商风险,并建立了科学、系统、动态的总承包商风险控制流程图及全面风险管理集成模式,可为总承包商进行风险管理提供参考.     

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。     

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.