西北内陆河流区间洪水设计计算方法比较分析

鉴于西北内陆河流进行区间设计洪水计算时所选方法对堤防工程设计安全性的影响,采用推理公式法、地区综合经验法、洪峰模数法计算了克孜河卡拉贝利站—卡甫卡站、卡浪沟吕克站卡甫卡站区间设计洪峰流量,并对比分析了三种方法的计算结果。结果表明,对于西北内陆河流,洪峰模数法计算结果相对更准确、合理,另外两种算法误差较大。     

国外工程中的小流域洪水计算方法探讨

为了解决国外工程中小流域洪水计算方法选择的难题,以土耳其小流域洪水计算为例,选取了推理公式法和SCS模型两种常用的小流域洪水计算方法,探讨了两类方法应用于土耳其小流域设计洪水计算的适用性,并将两种方法计算结果与土耳其常用洪水计算方法 DSI Synthetic Method的结果进行比较。结果表明,推理公式法与SCS方法进行小流域洪水计算时仅需要降雨、地形图和下垫面资料,对资料的需求较少,对无资料地区的适应性较强;从工程安全角度推荐采用DSI Synthetic Method计算结果作为土耳其工程设计洪峰流量最终结果更符合当地特点。     

推理公式法在复杂丘陵地貌设计洪水计算中的适用性分析

为研究推理公式法在复杂丘陵地区设计洪水计算中的适用性和误差来源，采用Morris筛选法分析了推理公式法参数的敏感性，通过与水文比拟法、历史洪水调查等结果进行对比，分析了推理公式法在不同流域面积的适用性。结果表明，面平均雨量是推理公式法主要的误差来源，误差随流域面积增大呈增加趋势，通过合理选择参数，对于面积在500～1 000 km²的流域，推理公式法仍具有适用性；以蒲江河流域为例，采用传统面雨量计算方法(不折减),当控制断面集雨面积分别为100 km²左右、100～500 km²、大于500 km²时，误差分别为5.1%～5.3%、11.2%～16.0%、25.2%～25.5%,当流域面积大于500 km²时，通过面雨量合理折减后，计算结果比历史调查资料仅小约0.2%。     

城市山丘区突发性洪水模拟与情景分析

为准确模拟、预测山区城市地区的洪水量并提供防灾减灾依据,以贵州省望谟县20110606山洪为例,利用简单可行的推理公式法模拟了突发性山洪洪量,再结合情景分析法模拟分析了望谟县城区洪涝情景。结果表明,基于推理公式法的洪水计算方法可较好地模拟无资料城市山丘区洪量;山丘区和城区同时遭遇高强度降雨情景下,洪涝规模及其破坏力将会大大增加;降雨量发生在很短时间内,降雨强度越大,汇流时间将会缩短,洪涝规模将大大增大。     

革什扎河两河口水电站设计洪水分析

水库设计洪水分析是水电站规划设计中一个重要环节。以革什扎河两河口水电站为例,根据设计洪水理论与实际资料,分析了该流域水文特性,计算了历史调查洪水资料的洪峰流量,并分别采用推理公式法和水文比拟法计算坝址设计洪水和洪峰模数。综合比较两种方法选用结果表明,革什扎河流域从上游到下游洪峰模数递减,符合暴雨洪水特性规律。     

混合煤气热值对折算标煤的影响

阐述混合煤气热值的两种计算方法:公式计算法,化验热值法。通过工况分析、数据比对,认为在混合煤气组分变化较大情况下,选择公式计算方法更为合理。     

应用推理公式推求不同形状小流域设计流量

针对采用推理公式推求小流域设计洪水,当净雨历时小于汇流历时时引进流域矩形概化假定使计算获得的洪峰流量偏小,基于矩形、菱形、椭圆形流域形状应用推理公式推导了倒三角形、扇形流域的最大共时径流面积,并归纳了洪峰流量的统一表达式,减小了因流域最大宽度的随意取值导致的误差.实例结果表明,该方法为不同形状小流域设计流量提供了有效可行的计算方法.     

一种发电系统可靠性评估的混合加速算法

针对使用时序蒙特卡洛法的可靠性评估计算效率低下、收敛特性较差等问题,提出一种结合基于交叉熵的重要抽样法和全概率公式法的混合时序蒙特卡洛评估算法,将其应用于发电系统可靠性评估中。基本思想是利用交叉熵优化过程获得近似零方差重要抽样密度函数,然后根据此时各元件故障率的扭曲程度确定对系统可靠性最重要的元件,对这些最重要的元件使用全概率公式,然后利用得到的各元件的新参数进行发电系统可靠性评估。由于两种基于不同原理的方差技术被组合使用,所以计算效率进一步提高,收敛速度进一步加快。最后使用可靠性测试系统IEEE-RTS以及修改后的测试系统对提出的方法进行验证,将所提方法(TP-CEMCS)的测试结果与传统时序蒙特卡洛法(MCS)、基于交叉熵的时序蒙特卡洛法(CE-MCS)和基于全概率公式的时序蒙特卡洛方法(TP-MCS)得到的结果进行比较,表明该方法在保证评估精度的基础上更进一步提高了计算速度。     

垣曲抽水蓄能电站设计洪水分析

设计洪水分析是抽水蓄能电站工程设计的关键内容之一,以垣曲抽水蓄能电站为例,根据我国现行设计洪水理论,利用相关水文资料,结合历史调查洪水成果,分别采用水文比拟法、瞬时单位线法、推理公式法、经验公式法计算该电站坝址设计洪水,综合比较最终选择水文比拟法作为设计洪水结果,并利用地区综合法进行合理性检验。结果表明,垣曲抽水蓄能电站设计洪水符合区域暴雨洪水特性,研究结果可为山西省小流域设计洪水分析提供重要参考价值。     

铁岗水库分期洪水调度研究

分别从气象成因、三防办和历史资料三方面分析了铁岗水库控制流域的暴雨洪水时程分布及分期规律,对汛期洪水的时域划分进行了研究.由实测暴雨资料推求设计洪水方法进行P-Ⅲ适线,并采用点面折算系数计算面雨量、采用广东省综合单位线法和推理公式法推求设计洪水过程.在确保大坝和下游防洪安全的前提下对水库进行调洪演算分析,发现三个分期在设计、校核情况下汛限水位均未超过原设计值,特别在前后汛期尤为明显.结果表明,可在汛期采用动态汛限水位进行水库调度,分期提高防洪限制水位,以增加蓄水库容,进一步发挥水库的综合效益.     

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

<正>~~     

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.