核电汽轮机通流能力分析及优化

我国很多核电机组存在汽轮机调门开度小的现象,导致节流损失增大。根据压水堆核电机组的主汽压力运行特点和实际运行数据,分析了出现该现象的原因,并提出了解决方案。通过精确设计主汽门前压力、优化汽轮机通流能力等方法,可以减小节流损失,增加机组出力,进一步提高核电站发电效率。     

六高调门配置汽轮机喷嘴进汽模式对轴系稳定性影响的试验研究

首先针对六高调门汽轮机调门局部进汽模式下的配汽不平衡汽流力进行理论分析,在典型六高调门配置汽轮机调门开关试验的基础上,得到六高调门配置汽轮机进汽模式对轴系稳定性的基本影响规律:喷嘴配汽采用上缸进汽和下缸进汽时,后面开启的3个高调门存在一个最优开启顺序;极端情况下,还可采用两阀联合调节进汽模式;然而,对角进汽模式对轴系稳定性的影响仍为最小。这对在国内占一定比例的六高调门配置大功率汽轮机安全高效运行优化具有一定借鉴意义。     

高参数汽轮机高调门内流动失稳故障的一种经济性解决方法

目前,规模化随机波动不确定性新能源电源的并网进一步增大了电网的峰谷差,使得越来越多的高参数大功率火电机组不得不参与调峰。然而,部分负荷进汽方式极大影响着调峰机组的安全高效运行。本文针对高参数汽轮机高调门局部进汽时由于设计缺陷引发汽流流动失稳故障,基于理论分析和试验测试提出了一种基于高调门局部进汽策略设计的经济性解决方法,避免了直接停机更换高调门阀体部件或者直接切换至全周进汽方式运行等现场常用的根本性解决措施所带来的各种损失。最后,通过对几台机组进行实际改造的效果验证了该方法的有效性和实用性。这对提高大功率火电机组深度变负荷运行时的安全高效性具有极大的工程实践价值。     

基于神经网络预测模型和凝结水节流的超超临界机组协调系统智能优化控制

针对某1000 MW超超临界机组,建立了具有较高精度和良好动态性能、考虑机组回热循环特性的机组负荷及主汽压力神经网络预测模型.在此基础上,提出了一种协调系统综合智能预测优化控制方法.该方法利用负荷及主汽压力预测模型在机组变负荷过程中分别对除氧器水位调门开度、汽轮机调门开度及燃料量指令进行实时优化,改善协调控制效果.借助1 000 MW超超临界机组仿真机,进行了详细的协调优化控制仿真试验.结果表明:该方法可有效提高机组动态过程负荷的响应速度和调节精度,大大减小变负荷过程中主汽压力的控制偏差,具有较好的工程实用性.     

亚临界330MW供热机组汽轮机高调门大幅高频摆动问题的分析及解决

本文针对电厂中亚临界330 MW供热机组存在的汽轮机高调门的大幅高频摆动问题进行了一些相关研究,通过对机组实际运行参数的对比分析发现,顺序阀进汽规律与高调门实际流量特性不匹配是高调门发生大幅摆动问题的根本原因。最终,通过对机组进行阀门实际流量特性辨识和顺序阀进汽规律优化,有效地解决了此问题。这对于提高目前在国内供热机组中占主流的300 MW级别机组运行的安全和经济性等具有一定的借鉴意义。     

某火电机组汽电双驱引风机系统辅机故障控制仿真及试验分析

为了研究某火电机组风烟系统采用汽电双驱型引风机系统,不同设备故障条件下机组相应的控制策略,依据热力学原理及设备固有属性,并搭建了相应的动力学模型,对发电机跳闸、小汽轮机跳闸、引风机与小汽轮机同时跳闸3种故障下的控制策略进行分析。最后,通过3次实际试验验证了控制策略及模型仿真结论的正确性。研究表明：在发电机跳闸时,可以通过调门快速动作到一定开度来保证机组的安全运行;在小汽轮机跳闸或引风机与小汽轮机同时跳闸时,可以通过保证机组的水煤比、风煤比等参数实现机组的减负荷运行。     

1000MW超超临界汽轮机组配汽优化技术探究

国内已建成投产的超超临界机组中的3大类型,其汽轮机设计定型和制造完成后其设计效率已基本确定,若需通过优化运行方式来提高机组实际运行效率,高压调门配汽优化是其中一项非常重要的工作。三种汽轮机配汽方式各有特点,与之相对应发展了不同的配汽优化技术。在配汽优化理论分析的基础上对这三类技术进行了分析比较,这些技术都能在无需增加硬件投资的前提下,降低发电成本,实现节能减排。     

汽轮机定滑压曲线简化计算方法

为了简捷获得较精确的汽轮机定滑压曲线,分析了主汽压力变化时机组热力系统变工况实际特性,基于高压缸效率实际变化非线性假设,在忽略随主汽压力和热耗率线性变化的其它热力参数前提下,结合调门流量特性曲线,提出了汽轮机定滑压曲线简化计算方法,以某350MW和某600MW机组的性能试验数据为例进行验证,结果表明,简化计算获得的定滑压曲线斜率与试验结果偏差在3%以内。     

1GW超超临界机组阀点滑压的自动寻优与精确控制

滑压运行是提高机组部分负荷运行经济性的主要手段,为了进一步降低机组能耗,在汽轮机传统滑压运行的基础上,通过试验分析了阀点滑压对机组各项参数的影响,充分利用了新阀门配汽方式,确定合理的阀门重叠度,进一步采用了阀点滑压运行,得出汽轮机阀门最佳运行方式,并通过背压校正机前压力,实施新协调控制系统优化机组参数等控制策略,使汽机调门实时处于最佳阀点运行,并实现了机组全季节经济滑压运行,有效降低了机组能耗。     

1000MW超超临界机组单侧中压调门异常关闭应对策略

根据国内首台1 000 MW超超临界机组的实际运行经验,并针对汽轮机单侧中压调门异常关闭后对机组参数的影响,介绍了汽轮机单侧中压调门异常关闭的处理过程和应对策略,并对华能玉环电厂中压调门的动作原理进行了介绍,可为同类型机组单侧中压调门异常关闭后如何快速判断和事故处理提供借鉴。     

Contents in Volume 23,2014

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Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

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.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Controls on the Karaha–Telaga Bodas geothermal reservoir,Indonesia

Karaha–Telaga Bodas is a partially vapor-dominated, fracture-controlled geothermal system located adjacent to Galunggung Volcano in western Java, Indonesia. The geothermal system consists of: (1) a caprock, ranging from several hundred to 1600 m in thickness, and characterized by a steep, conductive temperature gradient and low permeability; (2) an underlying vapor-dominated zone that extends below sea level; and (3) a deep liquid-dominated zone with measured temperatures up to 353 °C. Heat is provided by a tabular granodiorite stock encountered at about 3 km depth. A structural analysis of the geothermal system shows that the effective base of the reservoir is controlled either by the boundary between brittle and ductile deformational regimes or by the closure and collapse of fractures within volcanic rocks located above the brittle/ductile transition. The base of the caprock is determined by the distribution of initially low-permeability lithologies above the reservoir; the extent of pervasive clay alteration that has significantly reduced primary rock permeabilities; the distribution of secondary minerals deposited by descending waters; and, locally, by a downward change from a strike-slip to an extensional stress regime. Fluid-producing zones are controlled by both matrix and fracture permeabilities. High matrix permeabilities are associated with lacustrine, pyroclastic, and epiclastic deposits. Productive fractures are those showing the greatest tendency to slip and dilate under the present-day stress conditions. Although the reservoir appears to be in pressure communication across its length, fluid, and gas chemistries vary laterally, suggesting the presence of isolated convection cells.     

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.