The thermodynamic properties of humid air at high pressure and temperature

A computer program for calculating the thermodynamic properties of humid air at high pressure and temperature taking into account the imperfect properties of components (an ideal mixture) is presented. Information is given on the equations used for the components of humid air and on the effect the consideration of imperfect properties of components has on the limiting partial pressures of steam and on the density and enthalpy of humid air.     

高温高压蒸汽管道应变测量及应力分析

火力发电厂蒸汽管道是一个庞大复杂的结构体系,运行数年后,由于高温引起的安装应力使管道支吊架松驰,管道结构发生变形,导致非计划性停机检修,影响电网经济和安全运行。为找出管道的最大应力及应力分布,提出了用高温应变测量分析方法,对高温压力下的蒸汽管道进行现场应力测试,通过重新合理调整支吊架,大幅降低了管道结构应力并达到延寿的目的,实际验证表明该方法具有良好的降应力效果。     

Carrier mobility in ethylene-vinylacetate copolymer estimated bytransient space charge

Carrier mobility in an ethylene vinyl acetate (EVA) copolymer film was measured by a new technique. The time-dependent charge distribution was monitored by the pulsed-electroacoustic method when a pulse voltage was superposed on a dc bias voltage. A positive charge packet was injected from the anode soon after the pulse application, and moved towards the cathode. It was suggested from the movement of the charge packet that the mobility of the positive carrier at 10 to 60 MV/m was in the order of 10^-13 m²/Vs at room temperature. When the pulse voltage was very high, a charge packet appeared within the bulk, suggesting that carrier dissociation takes place     

磷酸铁锂常温常压环境下时效性能研究

对常温常压环境下保存1、30、180、360、720、1 080天的磷酸铁锂进行了研究。采用比色法比较不同时效样品Fe3+含量,化学滴定法测定不同时效样品LiOH、Li2CO3含量变化,并对不同时效样品进行了电化学性能测试。随保存时间的延长,Fe3+含量、LiOH和Li2CO3含量急剧增加,充/放电比容量降低,而且充电比容量降低得更多。     

MEMS接触电容式高温压力传感器的温度效应

介绍了一种基于SOI／硅片键合技术制作的接触电容式高温压力传感器结构,并对传感器的测试装置、测试方法进行详细的介绍后,对传感器进行压力测试和温度特性测试。压力测试结果表明,传感器线性工作区压力为110～280kPa,灵敏度约为0．14pF／kPa;温度特性测试结果表明,传感器具有正温度效应,在30～300％,传感器输出误差约为0．5％。文中还分析了热胀冷缩及介电常数温度系数对传感器温度效应的影响,以及设计了参考电容及运算放大器式传感器测量电路来消除温度效应。     

High-field dissipation current waveform in e-beam-irradiated XLPEfilm at high temperature

We developed a detection method of ac dissipation current waveforms combined with a fast rising ac ramp voltage application as a new technique to evaluate the high-field dielectric properties and the dissipation current waveform over a very short time range. This measurement was carried out on electron beam irradiated crosslinked polyethylene film. At high temperature the high field tan δ and ac dissipation current show nonlinear electric field dependence and the dissipation current during decreasing field becomes larger than that during increasing field, suggesting the contribution of carrier injection from electrodes. The dissipation current waveforms in the high temperature region show the peak in the first part of each half cycle of a full waveform, and fast decrease in the latter part. This result is probably due to the hetero and home space charge formation caused by the injected carriers from the electrode     

Characteristics of laminated tape insulation in high vacuum at cryogenic temperature

A composite insulation system of laminated tape and high vacuum is newly proposed for a superconducting bus-line cable operated at relatively low voltage. Its breakdown characteristics were investigated using model cable specimens with different kinds of laminated tapes such as semisynthetic paper, polypropylene film, and kraft paper of insulation thickness less than 1 mm. First, ±dc, ac, and —Imp breakdown stresses of the semisynthetic papers were investigated. +dc breakdown stress was 21.7 kV/mm for a specimen of insulation thickness 1 mm and −dc breakdown stress was 41.5 kB/mm, so that the remarkable polar effect was observed. ac breakdown stress was 18 kV/mm. Also, the ratio of −Imp breakdown stress was about 3. Furthermore, ac breakdown stresses of other tapes were investigated, but remarkable differences among their stresses were not observed. Most of the specimens were broken from the “butt gap” between tapes. To understand this cause, measurements of the partial discharge were carried out. It was found that the inception stress of partial discharge of butt gap located just on the conductor was about 20 kV/mm, not dependent on the kind of tape. This value is much lower than the breakdown stress of the same length of vacuum gap. Therefore, it is considered that the trigger of the breakdown of this insulation system is the surface discharge along the edge of the butt gap. © 1998 Scripta Technica, Inc. Electr Eng Jpn, 121(3): 20–26, 1997     

SOI高温压力传感器专用集成电路设计

针对压力传感系统高温条件下无法稳定工作、性能下降等问题,设计了一种基于SOI CMOS高温工艺的压力传感器专用集成电路(ASIC),主要由零温度系数恒流源、仪表运算放大器(由恒定跨导运放组成)和零温度系数电压基准组成,具有为压力传感器供电、放大输出信号及调节零点的功能,重点介绍了零温度系数恒流源、仪表运放及组成仪表运放的运算放大器等相关电路。仿真结果表明,-55~225℃温度范围内,恒流源温度系数为109ppm/℃,运算放大器输入MOS管跨导几乎与温度无关,仪表运放输入输出电压成正比且共模抑制比高达125 d B。测试结果显示该压力传感器专用集成电路可在225℃下正常工作。     

On PD mechanisms at high temperature in voids included in an epoxyresin

In this paper the effects of temperature on partial discharge (PD) activity taking place inside a spherical void in epoxy resin system are studied. Indeed, some experimental tests previously performed on specimens, having different void shapes, under multi-stress condition of temperature and voltage, have shown very different PD amplitude distributions at temperatures higher than ambient. However, this phenomenon cannot be explained only by taking into account the different thermobaric conditions of the enclosed gas. In consequence of the general physical inaccessibility of such voids, a study is here performed using a numerical model based on an evolutionary optimization algorithm. This is used to evaluate the range values for the physical parameters of the insulating system influencing the observed changes in PD activity. Finally, comments are presented about the adopted criteria by which the comparison between the experimental data and the simulated ones is performed, and about the interpretation of the dependence on temperature of the experimental PD     

The optical properties of microbulb alumina ceramics at high temperature

The normal spectral emissivity of two types of high-temperature ceramics made of alumina microbulbs as a function of the wavelength and temperature was investigated experimentally for the first time. Data for samples of various thicknesses (2–8 mm) at wavelengths of 1.0–5.0 μm and temperatures of 1073–1873 K were obtained. The ceramics optical properties in the forms of an effective absorption factor and a radiation diffusion factor were calculated in the wavelength band from 3.2 to 4.6 μm using the dependence of emissivity on thickness. The effect the porosity of ceramics has on its optical properties was analyzed.     

高温高速气流温度测量方法的研究

本文提及的测量方法是针对高温高速气流在温度测量过程中存在着气流温度本身在变化与温度传感器有一定响应时间这2个难点而设计.它是通过启动弹射装置,把热电偶测量端射入气流中,经过一规定时间后,将其自动收回,测出热电偶测量端的瞬时温度,进而就可推算出被测气流的真实温度值.通过此方法测量后,可确定热电偶的时间常数,而当测量时间大于3倍热电偶的时间常数时,动态响应误差可以减到最小.另外,热电偶的测量端体积要尽可能小,这样不仅能提高响应时间,把动态响应误差可以减少到最小,而且还能克服滞后带来的影响.     

大型超高压循环流化床锅炉高温热烟气烘炉实践研究

针对大型超高压循环流化床锅炉采用明火烘炉、局部烘炉不能有效控制烘炉过程、温度分布不均匀等问题,阐述了义马锦江矸石电厂DG-440/13.7-Ⅱ2型循环流化床锅炉炉衬材料的分布情况和养护要求,采用了高温热烟气整体烘炉法,能够对烘炉的全过程进行有效的控制,节省了烘炉时间和烘炉费用,保证了烘炉质量.     

Partial discharge endurance life of polymer insulating materials at high temperature

This paper describes the partial discharge (PD) characteristics and V‐t characteristics of several insulating materials, such as liquid crystal polymer, epoxy resins, polyimide, and polyethylene‐terephthalate (PET) with a needle‐plane electrode system at elevated temperature. The life index n for an applied electric field less than 20 kV/mm is found to be about 9 and that for more than 20 kV/mm is found to be less than 4. The PD characteristics of the insulating materials varied. These V‐t characteristics due to PD degradation were similar to those at room temperature except for the absolute life time. © 1998 Scripta Technica, Electr Eng Jpn, 126(1): 15–22, 1999     

锂离子电池高温反应及其影响因素

锂离子电池热稳定性能的研究是近年来锂离子电池研究的一个热点。锂离子电池内部高温反应有SEI膜分解反应,嵌锂碳(LixC6)与电解液的反应,嵌锂碳与粘接剂的反应,电解液分解反应．以及正极材料的分解反应,分别对其研究现状作了综述;并分析了影响锂离子电池内部高温反应的各种因素。     

高加解列引发主汽温度升高的原因分析及调整措施

高压给水系统在运行中经常会发生泄漏现象,导致高加频繁解列,解列后所带来的负面影响一是降低机组出力,二是引起锅炉过热器汽温超标,所以,在运行过程中,尤其是在给水操作平台不设主给水调整门这一优化方案的系统的运行中,有必要掌握高加解列的原因,并有针对性地采取措施加以应对。本文根据现场情况认真分析原因,总结出一点经验和体会,基本解决了高加解列、机组限出力和主汽温超温的问题。     

Resistive states in strontium titanate thin films: Bias effects and mechanisms at high and low temperature

A study on charge transport properties of thin film Fe-doped SrTiO₃ epitaxially grown on Nb-doped SrTiO₃ is reported. Electric measurements between 350 °C and 750 °C show a transition from predominant ionic to electronic conduction and lower conductivity of the thin films compared to the bulk of polycrystalline samples. Defect chemical changes at elevated temperature were investigated by applying a bias voltage. A model is described which successfully predicts additional features such as inductive loops or extra semicircles measureable by impedance spectroscopy as well as the complicated time dependence of electric DC-measurements. With this model it is also possible to calculate the negligibly small ionic conductivity next to the dominating electronic conductivity in the high temperature regime. The ionic conductivity is referenced by oxygen isotope depth profiling. Changes of resistive states in Fe-doped SrTiO₃ thin films at high temperature and moderate fields are compared to room temperature resistive switching phenomena at high electric fields. A conductive filament based switching process is observed at room temperature, and the capability for forming such filaments and their electric properties is further analysed using microelectrodes.     

高温PEMFC进气压力突变下的瞬态性能模拟

高温质子交换膜燃料电池(HT-PEMFC)以其水管理简单,对CO的耐受性强等优点得到越来越多的关注。而基于燃料电池在实际中的应用,它的瞬态性能研究也逐渐增多。通过建立一个三维非等温瞬态模型对基于磷酸掺杂聚苯并咪唑(H3PO4/PBI)膜的HT-PEMFC进气压力突变下的瞬态性能进行了相关研究。在这个模型中考虑了磷酸掺杂程度、入口相对湿度等对膜电导率及电池瞬态性能的影响。结果表明,在进气压力变大时,较小的磷酸掺杂程度、较小的入口相对湿度、较大的负载都会使电池更快地达到新的稳定状态。     

LDPE中介入聚合物阻挡层后其交流电场下的电树特性分析

为了研究低密度聚乙烯(LDPE)的电树老化特性,观察电树在LDPE中的生长情况,以及在频率50Hz交流电压作用下电树老化引起的破坏现象和电树生长过程中的形态变化,采用在LDPE样品的两电极之间介入阻挡层,且阻挡层分别选用不同材质的聚合物薄膜。对介入了聚合物阻挡层的LDPE与纯LDPE样品电树的生长形态及电树的生长方向进行比对,观察阻挡层对电树的影响情况,并探讨了不同阻挡层对电树阻挡作用的差异。结果表明,当在针-板电极中放入阻挡层时,可以减缓电树的生长,对于增加其击穿时间有一定的研究价值;对击穿时间的影响取决于阻挡层材料本身的性质和结构特点以及空间电荷的作用。     

动力锂电池大倍率放电时内外部温度场的研究

利用数值模拟的方法建立了3.2 V/50 Ah LiFePO_4动力电池放电过程的电热耦合模型,研究其在自然环境中不同放电倍率条件下的内外部温度分布。并且为验证模拟结果的准确性,比较了模拟所得数据与实验所得数据的一致性。结果显示:模拟所得温度与实验测得温度最大的偏差小于1℃;放电过程中,电池内部中心区域的温度最高,正负极极柱上的温度最低,温度场不均匀性随着放电倍率的增大而增加。