船舶采用万向节偏移传动螺旋桨提高推进效率的分析

历来船舶的推进系统都采用桨－轴－机三位一直线，且它们的公共轴心线都几乎平行船种的传动方式，这种方式存在着推进效率低等问题。本文从实用出发提出采用万向节偏移传动螺旋桨的方法，可使单桨船的推进效率提高７％～１０％，双桨船的推进效率提高５％左右。     

基于多功率耦合的风光互补制氢系统容量配置优化方法

为保证风光互补制氢系统平稳运行及蓄电池容量最优化,提出一种结合实际环境的改进蓄电池容量确定法,综合考虑制氢装置平均功率、蓄电池所需容量、制氢功率切换及工作功率波动等多因素影响,并针对单功率、双功率和三功率等不同制氢功率模式进行系统分析。结果表明,选取双功率模式能使蓄电池容量大幅减少,同时高低功率差距在允许范围内,功率切换不频繁,控制相对简单。     

非反向Buck-Boost变换器的三段式ZVS控制策略

目前文献中的四边形控制方法及其改进方案，能实现非反向Buck-Boost变换器各开关管的ZVS，但存在如下问题：需使用多维查找表或外部存储设备而无在线检测实时计算的闭环、较大的通态损耗和多模式切换引起的输出电压波动等。该文针对上述3个问题提出一种三段式变频ZVS控制策略。首先，去除四边形控制中电感电流的环流续流环节，以减小电感电流有效值并提高效率。其次，在不添加任何额外有源或无源器件的条件眄，将整个宽输入电压范围分成3个模式，分析每个模式的特点，以增加控制条件和简化计算过程，同时实现各模式的在线实时恒压闭环和通态损耗最小ZVS而无需使用多维查找表和线性插值，整体控制简单易实现。然后，提出基于三段式ZVS控制的多模式平滑切换控制策略，可保证在模式切换时各开关管占空比跳变前后，闭环输出始终保持稳定。最后，本文给出了各模式区间划分的理论依据，并搭建500 W实验样机验证了所提方案的有效性。     

单机双缸主汽轮机组实现单缸运行的快速切换

本文介绍了单机双缸式主汽轮机组实现单缸运行快速切换的工作原理，并对其切换装置的结构设计方案进行了论证比较，提出了两种快速切换装置设计方案：盲板切换阀和快开法兰。这两种新型的切换装置具有结构简单、性能可靠、布置安装方便、切换时间短等优点。     

某型混合动力系统大功率轴带电机平稳启动并网的控制方法及实船应用

在双机双桨混合动力系统的并车推进/电机推进模式切换过程中,采用小电机辅助启动控制方法与主机辅助启动控制方法可实现大功率轴带电机平稳启动并网控制,避免其直接启动并网造成大电流危害船舶电网等问题。经实船验证,小电机辅助启动控制方法与主机辅助启动控制方法可靠且有效,在轴带电机启动过程中能够保障船舶安全航行,同时降低动力系统设备成本、节省船舶安装空间。     

热工联锁保护系统配置优化技术

本书共分6章，分别为热工联锁保护基本原则与要求、锅炉侧联锁保护系统、汽轮机保护系统、辅机程控联锁保护系统、保护用控制设备与测量元件、机炉联锁保护配置优化方案示例。     

DF4B型机车DLS防护罩改进

1概述 DF4B型机车DLS(电磁联锁)是控制柴油机起机、停机的装置.它的防护罩安装在联合调节器上,对DLS起着防止磕碰、防止上部水箱涨水溅落以及接线被刮断等保护作用.     

2M无损切换装置与继保极控装置互联的可靠性测试

文章介绍了目前广泛应用在国调直调通信系统中的2 M无损切换装置的工作原理,并通过在实验室条件下对该装置的主要性能进行测试,分析了该装置对继保极控装置及电网运行情况的影响,以期为该类装置的使用限定和通道切换时延、掉电瞬断时间等技术标准的制定以及出现故障时的定位和判断提供参考。     

渔船用柴油-LNG双燃料发动机电控系统研究及应用

基于一台型号为NT6135ZCzA的渔船用增压柴油机,加装了一套LNG多点喷射供给装置和油泵齿条限制机构;利用Infineon高性能32位TC1766单片机开发了柴油-LNG双燃料发动机电控硬件系统,并设计了混燃调速控制策略及燃烧模式切换控制策略。台架试验证明改装后的柴油-LNG双燃料发动机在替代率为70%时,扭矩与原柴油机相比下降1.6%,两者基本相当,碳烟排放减少,排气温度降低。采用本系统设计的混燃调速方案二在低负荷和中高负荷区的燃料经济性均高于方案一,通过燃烧模式切换策略,在负荷低于35%时自动切换到纯柴油模式,可进一步改善低负荷区的燃料经济性。     

发电厂热工联锁保护系统可靠性分析

1　热工联锁保护的作用及其重要性热工联锁保护系统是发电厂安全运行的非常重要设备之一 ,其作用是当被测参数超过允许极限值时 ,保护系统装置准确可靠地动作 ,实行紧急停机 ,以保证机组的安全 ,防止事故的扩大。一旦保护系统失灵 ,轻者造成一定的经济损失 ,重者可能造成机毁人亡的恶性事故。　　　　　能源研究与利用 2 0 0 0年第 4期2　热工联锁保护系统工作的准确率保护系统工作时可能会出现三种情况 ,第一是在系统规定的条件下正常工作 ;第二是保护系统在该动作时不动作 ,称之为拒动 ;第三是保护系统不该动作时动作 ,称之为误动。因此可…     

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.