天然气冷热电三联供系统的发展趋势分析

天然气冷热电联供系统是以天然气为一次能源建立在能量梯级利用基础的多联产总能系统。介绍了天然气三联供系统系统的组成、设计模型及配置方式,通过对比现存的典型三联供系统,得出了目前系统发展的难点并提出了相应的解决措施。最后针对如何提高三联供系统的经济性,充分发挥三联供系统的优势进行了探讨分析,提出了新型的三联供系统形式:可再生能源三联供系统,基于天然气三联供的能源集成系统以及能源总线系统。     

可变几何排气管增压系统与其他增压系统的对比计算研究

为了解决某船用8缸机高低负荷兼顾的问题,提出了1种全新的可变几何排气管增压系统,它通过安装在排气管上的可控阀门来实现增压方式的转换。利用GT-POWER对可变几何排气管增压系统进行了计算研究,根据油耗最优原则找出其阀门开和阀门关之间的切换点在50%负荷;又分别对四脉冲增压系统、PC系统、MPC系统和MIXPC系统进行了计算研究。计算结果表明:在25%、50%、75%、100%负荷,可变几何排气管增压系统的油耗均小于四脉冲增压系统、MPC增压系统和MIXPC增压系统的油耗,扫气系数均大于四脉冲增压系统、MPC增压系统和MIXPC增压系统的扫气系数。     

变风量空调系统模拟及能耗研究

应用DeST软件模拟分析了某大型办公建筑全年动态负荷 ,并对带有串联型末端装置的变风量系统及常规空调系统进行全年能耗计算。通过各系统能耗的比较 ,说明了该建筑使用VAV系统比常规空调系统具有良好的节能性及在系统的使用寿命内应用变风量空调系统是相当经济的。对变风量空调系统在国内的应用前景进行了合理评判。     

工业用太阳能并网发电系统防逆流技术探讨

<正>一前言目前,太阳能发电系统主要分为独立电源系统与并网发电系统两大类。并网发电系统可分为大规模太阳能电站、工业用太阳能发电系统和家用太阳能发电系统三大类。其中工业用太阳能发电系统因国内企事业单位环保意识的逐步提高,二氧化碳减排要求的规     

注水系统参数优化方法及其应用

油田注水系统参数优化方法是以减少系统能量损失,提高系统效率,达到系统高效经济运行的一套科学方法、它实现了全系统的合理运行,系统能量损失最小,因而为系统的运行或系统的综合治理提供了明确的方向和途径。     

IGCC系统中燃机岛特性研究

IGCC系统由气化岛、燃机岛、常规岛及其辅助系统组成,其中燃机岛对IGCC系统性能有较大的影响。本文利用ThermoFlex软件建立200MW级IGCC系统模型,从系统角度出发,研究IGCC系统中的燃机岛特性,分析燃机岛关键参数变化对IGCC系统的影响。研究结果表明：燃气轮机出力和系统发电量随着大气温度的升高而下降,随着大气压力升高而升高;系统的发电量和系统效率随燃气轮机负荷的下降而下降;燃气轮机出力和系统发电量随压气机进口空气量的减小而减少,随着通流面积的增加而增加。本系统最佳的氮气回注系数为60％及整体空分系数为20％。     

基于排风热回收的空气源热泵粮食干燥系统运行特性的研究

为探索稻谷在烘干过程中排风热回收应用于空气源热泵干燥系统的可行性,文章主要以进风温湿度、送风温湿度、系统耗功、系统性能系数COP、单位耗能除湿量SMER和含水率等作为性能评价指标,分别对半开式和开式系统的运行特性进行了实验对比研究。实验结果表明,这两种系统用来烘干稻谷均能使其含水率达到要求,但半开式系统整体性能要显著优于开式系统。半开式系统的进风温湿度分别为22～27℃,75.8%～95.3%,开式系统的进风温湿度分别为16.5～22.8℃,51%～90.5%,半开式系统蒸发器的进风温湿度均高于开式系统;半开式系统送风含湿量平均为16.8 g/kg干空气,开式系统送风含湿量平均为9.8 g/kg干空气,半开式系统的送风含湿量大于开式系统;半开式系统的送风温度为64～65.5℃,而开式系统的送风温度为62～65℃,开式系统送风温度有时不能达到要求;半开式系统和开式系统的平均耗功率分别为41.07,45.92 kW;半开式系统和开式系统的COP分别为2.86,2.74;半开式系统和开式系统的SMER分别为2.759,2.639 kg/（kW·h）。     

太阳能热发电系列文章(17) 70kW塔式大阳能热发电系统研究与开发(下)

阐述了塔式太阳能热发电系统中的接收器、燃气体轮机系统、辅助系统和控制系统的有关知识;介绍了南京江宁70kw。塔式太阳能热发电系统的接收器、燃气体轮机系统、辅助系统和控制系统的构成;总结了系统建设的目的和意义,并展望塔式太阳能热发电的前景。     

适应将来高速柴油机要求的喷油系统

为了满足今后MTV(德国发动机和涡轮联合有限公司)高速柴油机的要求,必须提供效能相应提高的喷油系统。本文对常规的直列泵供油系统、单体泵喷油系统和泵喷嘴喷油系统进行了比较,并对单体泵喷油系统作了分析。采用电磁阀控制的单体泵喷油系统可获得更高的使用灵活性和结构上的众多优点。文中亦指出了这种系统的一些缺点和限制。研究表明,最佳的喷油系统是共轨式喷油系统。共轨式喷油系统在喷油率成形方面具有最大的灵活性,并在设计制造成本低的发动机方面具有最明显的优越性。     

大型钢球磨煤机直吹式制粉系统提高出力的实践

介绍600MW机组锅炉为提高制粉系统出力而进行的制粉系统改造,包括制粉系统分离器改造和磨煤机改造;介绍对制粉系统运行参数进行的调整,以及制粉系统出力试验,并对制粉系统出力试验的结果进行分析,指出影响制粉系统出力的几个主要因素。通过制粉系统改造前后的出力对比试验,证明所采取的措施能显著增加制粉系统出力,使制粉系统出力从40t/h增加到约60t/h,提高了锅炉的安全经济运行水平。     

Combined vector control and direct torque control method for high performance induction motor drives

A new control method is proposed for three phase high performance induction motor drives. The control system enjoys the advantages of vector control and direct torque control and avoids some of the implementation difficulties of either of the two control methods. In particular, the proposed control system includes a current vector control in connection with a switching table. An extensive comparative performance evaluation of a motor under the proposed control method confirms the effectiveness of the method and its partial superiority over either vector control or direct torque control despite its relative structural simplicity.     

PLC、全数字直流调速器在辊道炉传动系统中的应用

介绍PLC、全数字直流调速器在辊道炉传动系统中的应用,并对系统的硬件配置及其工作原理、软件的参数设置、部分软件框图作了说明。该项改造具有较好的经济效益和社会价值。     

海上风电柔性直流输电变流器研究

简要分析海上风电柔性直流输电技术应用及变流器关键技术特点,设计基于柔性高压直流（HVDC）输电的风力发电机集中控制并网变流器主电路拓扑结构,基于电流峰值控制的三电平直流升压变换器双梯形波补偿方法,并利用滞环宽度可调的滞环比较器进行电流跟踪控制。仿真研究表明,该方法具有变流器功率管开关频率固定、减少开关应力及开关损耗、提高传输效率的特点,有助于减少开关器件电压应力和电抗器电流脉动值,提高系统运行的稳定性和可靠性。     

Eyewitness to dc history

This issue's history article offers eyewitness accounts of two important events, 125 years apart, in the history of electric utility service. Thomas Edison's famous Pearl Street direct current (dc) generating station and underground distribution system in New York City went into service on 4 September 1882 and ended its service on 14 November 2007.     

Exergy flow and energy utilization of direct methanol fuel cells based on a mathematic model

An exergetic analysis model for direct methanol fuel cell (DMFC) is established in the present paper. Expressions of electrical, thermal and total exergetic efficiencies have been deduced with consideration of methanol crossover and over potential in operation. Furthermore, energy utilization of a DMFC system is quantitatively calculated and changes of electrical efficiency and thermal efficiency at various current density, methanol concentration, operating temperature, and cathode pressure have been investigated. Some suggestions of optimal operating conditions of direct methanol fuel cell based on our findings are put forward. Results show that the thermal energy generated in a DMFC takes up a significant amount of exergy in total energy and should be sufficiently used to obtain high total efficiency in a DMFC, high methanol crossover rate is the predominant cause of energy loss when the fuel cell operates at low current density, and total exergetic efficiency of a DMFC reaches its peak value at relatively high current density.     

Current density measurements in direct methanol fuel cells

The current density in the fuel cell is the direct consequence of reactions taking place over the active surface area. Thus, measurement of its distribution will lead to identification of the location and nature of reactions and will give opportunity to improve the overall efficiency of fuel cells. Within this study, the current density distribution in a direct methanol fuel cell was analyzed by segmenting the current collector into nine sections. Besides, the effect of the different operating parameters such as molarity, flow rate and reactant gas on the current density distribution was analyzed.     

智能电网的发展对大电网可靠性评估的影响

智能电网是未来电力系统发展的重要方向。与传统电网相比,智能电网涉及到大量的新型发输电设备,必然会给大电网可靠性的评估带来影响。以计及储能装置的风力发电、高压/特高压直流输电、柔性直流输电系统、柔性交流输电技术、电动汽车等技术为例,分析了其对大电网可靠性的影响,以及新技术在接入电网时应注意的问题,最后结合智能电网的发展进程,提出了未来大电网可靠性评估领域重点发展方向。     

A method for evaluating the influence of wiring on the performance of components in a photovoltaic system design

This paper presents a simple method for evaluating the influence of wiring on the operating conditions of the direct current components in a photovoltaic system design. This method uses electrical circuit theory, electrical resistance modeling, and an iterative calculation approach to address the causality dilemma that exists when estimating voltage reductions in the wires that connect photovoltaic modules to power inverters. This method can be used to estimate the voltage, current output, and power output of each photovoltaic module in a system, and the corresponding total power available at the inverter, given current–voltage (I–V) models for the photovoltaic modules, and the lengths and thicknesses of the corresponding interconnection wiring. This paper uses this method to illustrate the influence that wiring can have on the direct current operating voltage that is needed at the power inverter to achieve maximum power performance for the system. The goal is that this method would be incorporated into software that analyzes the power performance and energy output of photovoltaic systems.     

A thermo-electric refrigerator powered by photo-voltaic solar collectors

In developing countries and remote areas where an electric supply is not available, a thermo-electric refrigerator is often needed for food and medical drugs storage. Such a refrigerator, which requires a direct current supply is suitable for matching with a photo-voltaic collector (PV). A normal automobile 12-volt lead-acid battery may be used as the storage system. This refrigerator is rugged and may be operated by unskilled people: a prototype has been built and its components are available commercially.     

Lightweight current collector based on printed-circuit-board technology and its structural effects on the passive air-breathing direct methanol fuel cell

To realize lightweight design of the fuel cell system is a critical issue before it is put into practical use. The printed-circuit-board (PCB) technology can be potentially used for production of current collectors or flow distributors. This study develops prototypes of a single passive air-breathing direct methanol fuel cell (DMFC) and also an 8-cell mono-polar DMFC stack based on PCB current collectors. The effects of diverse structural and operational factors on the cell performance are explored. Results show that the methanol concentration of 6 M promotes a higher cell performance with a peak power density of 18.3 mW cm⁻². The combination of current collectors using a relatively higher anode open ratio and inversely a lower cathode open ratio helps enhance the cell performance. Dynamic tests are also conducted to reveal transient behaviors and its dependence on the operating conditions. To validate the real working status of the DMFC stack, it is coupled with an LED lightening system. The performance of this hybrid system is also reported in this study.