燃料电池发动机水热管理系统设计研究

介绍了质子交换膜燃料电池的工作原理与特点,分析了保持燃料电池内部水平衡和热平衡的必要性,根据东风电动汽车有限公司25kW燃料电池发动机的设计参数,计算出空气和氢气的加湿量及电堆的散热量,设计出了一套有效的燃料电池发动机水热管理系统方案。     

表面改性不锈钢双极板的性能研究

双极板是质子交换膜燃料电池的重要的多功能组件.不锈钢材料由于具有良好的耐腐蚀性能成为金属双极板理想的选择.但其表面高电阻的钝化膜会降低电池性能.测定了经过镀铬后再离子氮化的304不锈钢在模拟PEMFC环境下的电化学性能,测量了氮化层与碳纸之间的接触电阻.结果表明,该表面改性方法使304不锈钢在模拟PEMFC阴极和阳极情况下的钝化电流密度降低,均低于双极板设计标准16 μA/cm2;改性后的304不锈钢的接触电阻值降低,电性能得到了提高.     

质子交换膜燃料电池凝水的研究进展

分析了质子交换膜燃料电池(PEMFC)中凝水的生长过程,分析了运行时间、电流密度、流速、温度、压力、湿度、流场和扩散层等因素对凝水的影响,并介绍了凝水的处理方法。对PEMFC凝水的可视化观测已从宏观步入微观。     

基于不同电极位置的PEMFC运行特性研究

质子交换膜燃料电池(PEMFC)是一种有巨大发展潜力的发电装置,特别适合成为新一代便携式电源和电动汽车的动力源.水是影响燃料电池性能的关键因素,良好的水管理是使其安全稳定运行和提高其性能的必要条件.在PEM燃料电池的阴极侧安装风扇,向燃料电池提供氧化剂和降低电池温度,通过实验,观察到在电池堆方向发生变化的情况下,PEM燃料电池性能及其内部传质情况会发生明显变化.实验结果发现:当电流密度较小时,电极方向对PEM燃料电池的性能影响不明显;当电流密度较大时,阳极在上、阴极在下时燃料电池性能优于阴极在上、阳极在下的燃料电池性能.     

质子交换膜燃料电池气体扩散层研究进展

质子交换膜燃料电池(PEMFC)可以提供较高的功率/能量密度,是未来空间探索最有前途的动力设备之一,其性能主要取决于内部反应物的传输和水管理.气体扩散层(GDL)作为燃料电池中的重要组成部件,与燃料电池的质量、水、热和电的多相传输紧密相关,是反应物和液态水的主要传输场所.因此,要提高燃料电池性能,合理的气体扩散层的设计至关重要.从提升空间燃料电池的使用寿命、稳定性及电化学性能的角度出发,综述了气体扩散层的物理化学特性,并介绍了多种改性方法,包括疏水性、结构和新型一体式GDL以及其对燃料电池性能的影响,为未来空间燃料电池高性能GDL设计提供了参考.     

PEMFC膜水含量及水传输综述

燃料电池水管理的目的是维持电池内部的水平衡状态,实现长期稳定工作并保持最高输出性能。膜水含量是重要的状态参数,对电池的性能影响很大。综述质子交换膜燃料电池(PEMFC)内水的传输、转化过程以及膜水含量的研究进展。总结目前PEMFC膜水含量的测量方法,包括在线分析、数值模拟和间接法等,分析膜水含量对电流密度分布、质子传导能力和膜电阻等的影响机理。对比现有研究方法和检测方法的优缺点。当前,膜水含量的监测因成本、实时性和环境因素,仍有一定的局限性和误差。建立实时监测模型,维持水平衡状态,是提升电池性能和耐久性的关键。     

燃料电池质子交换膜研究现状与展望

质子交换膜燃料电池是目前研究的热点之一,研究方向包括提高燃料电池效率、减少成本、提高耐久性等。作为质子交换膜燃料电池的核心部件,质子交换膜性能的好坏直接影响燃料电池的性能与寿命。文中首先概述了燃料电池质子交换膜的工作原理。随后,总结了燃料电池质子交换膜的分类,主要分为全氟磺酸质子交换膜、部分氟化聚合物质子交换膜、复合质子交换膜以及非氟化聚合物质子交换膜四大类,同时还简述了质子交换膜的制备工艺。最后,介绍了燃料电池质子交换膜的优化方案,主要包括有机/无机纳米复合质子交换膜、改进质子交换膜的骨架材料、调整质子交换膜的内部结构、机械增强型质子交换膜以及自增湿型质子交换膜。     

车用PEM燃料电池堆绝缘电阻的实验研究

电动汽车应用的燃料电池发动机,一般具有100～600V的直流电源电压。应当对其绝缘性能进行相应的试验研究及在线监测,确保符合电动汽车(EV)的电气安全要求。我们利用绝缘电阻在线监视仪在线测量燃料电池发动机中质子交换膜燃料电池(PEMFC)堆的绝缘电阻,研究各种条件下(如:燃料电池电流输出、操作温度等)燃料电池绝缘电阻的变化规律,为提高和改善电动汽车用燃料电池的绝缘性能提供参考。     

车用燃料电池水故障的在线诊断

质子交换膜燃料电池(PEMFC)易发生水淹、膜干等健康故障。合理的水故障诊断有助于对PEMFC内部的工作状态进行实时监测、预警并及时应对。基于气体压力降的水故障诊断方法搭建PEMFC水故障在线诊断测试平台;介绍气体压力降的理论计算方法;针对某款PEMFC堆进行阴、阳极气体压力降和电压的测试研究及分析。由于实验过程中PEMFC内部水量的变化,前1 000 s时,阴极气体压力降快速升高,阳极气体压力降缓慢升高,电压值快速下降;1 500 s后,阴、阳极气体压力降和电压值趋于稳定。该方法能实现PEMFC水故障的在线诊断。     

Effect of fluctuation of surface sea water temperature and ambient pressure on evaporation rate of evaporator in barometric type OC-OTEC system

Global environmental problems, such as global warming and the effects of acid rain, are expected to become more serious in the future. One methodology for solving this problem uses harmless energy resources. Ocean energy is one of such energy resources. This research involves a study of the OC-OTEC system, which is one type of ocean thermal energy conversion technology. In this system, the steam that drives a turbine is generated in an evaporator and condenses in a condenser after passing through a turbine. However, the steam evaporating rate in an evaporator is affected by the fluctuations of surface sea water temperature and ambient pressure. Therefore, it is necessary to define the dynamic characteristics of the evaporator in order to gain constant power output. This paper presents an analysis as to how evaporation rate is affected when surface sea water temperature and ambient pressure change. Further, we clarify that the dynamic characteristics of the evaporator are more affected by fluctuations in the ambient pressure than in surface sea water temperature.     

An experimental study of autowave velocity during water boiling in a tube

The motion velocity and heat transfer at the front of temperature wave during the changeover from a film to nucleate boiling mode as functions of heat load and mass flowrate are determined for water at atmospheric pressure and zero inlet steam quality. It is shown that the essential change of heat transfer regularities in the zone of temperature waves is satisfactorily described by linear terms of expansion into the Maclaurin series of the sink function with respect to the temperature field gradient.     

空冷型PEMFC阳极排气周期实验研究

针对不同负载和阳极排气周期,对自制的空冷型质子交换膜燃料电池(PEMFC)进行实验。在实验过程中用单电池巡检系统监控各单体电池的电压,红外热像仪测量电堆表面的温度分布。在恒压输出模式下,随着阳极排气周期和负载的增大,单体电池的电压差逐渐扩大。当排气间隔为50 s(单体电池电压设定为0.6 V)时,平均电压最大偏差达0.2 V,出现该现象的原因是高负载输出时,如阳极排气不及时,更容易发生水淹。     

高拱坝表孔宽尾墩体型优化试验研究

高拱坝表孔溢流坝面短,作用水头低,堰前行进水流具有向心倾向.宽尾墩消能工应用在高拱坝泄洪表孔必须与此特点相适应.本文对宽尾墩应用在高拱坝坝顶泄洪表孔的体型布置进行了试验研究.结果表明,宽尾墩应用在高拱坝表孔时,出口角度不宜采用挑角,而应采用俯角:采用较大的宽尾墩墩尾折角有利于水流的纵向扩散和减小水垫塘底板冲击动压;同时为避免拱坝曲率造成的水流径向集中现象,两边表孔宽尾墩应采用非对称体型设计.优化后表孔水流能够在竖向及纵向充分扩散,空中呈窄而高且长的流态,在水垫塘中横向分区入水明显,不仅使水垫塘底板冲击动压减小和冲击点向下游偏移,而且为高拱坝表深孔水舌相互穿插无碰撞消能,减轻泄洪雾化创造了条件,对狭窄河谷中的高坝工程具有重要的工程应用价值.     

A study of partial discharges from water droplets on a siliconerubber insulating surface

This paper presents measurements of partial discharge (PD) from water droplets on a silicone rubber insulating surface in an ac field. Tests are done by placing droplets on the surface using a micro-pipette, and by condensing water in a controlled humidity chamber. The field enhancement factor due to droplets placed on the insulation surface is experimentally and numerically determined. Values in the range of 3.8 to 6.3 are obtained depending on the size and number of droplets. The time resolved analysis of PD from water condensation indicates a threshold field, between 3.0 and 3.5 kV/cm, above which the PD activity increases with time, and brings the insulation to a surface breakdown. The corresponding field enhancement factor obtained for the condensation experiments is between 5.8 and 6.8. The results therefore suggest that the PD activity on the hydrophobic surface can be used effectively to learn about the insulation surface conditions     

泾河东庄水库排沙试验研究

泾河东庄水库是拟建在典型的高含沙河流上的水利枢纽。本文运用河工动床模型相似理论和异重流运动相似条件的最新研究成果进行了模型设计和制作 ,并进行了典型组次的排沙试验 ,研究不同水沙条件、河床边界条件及库区蓄水条件下的排沙情况 ,得出了排沙比及排沙量与进出库流量、沙量、含沙量和初始库水位的关系     

Locating faults in a transformer winding: An experimental study

Based on terminal measurements on a single, continuous-disc winding of a transformer, it is demonstrated how faults introduced at different positions along the winding could be localized with reasonable accuracy. Fault in the present context represents a discrete change, e.g. short-circuiting a few turns within a disc (i.e. predominantly an inductive change) and/or addition of some tens of pico-Farad capacitance between a disc and ground (i.e. predominantly a capacitive change). Open-circuit and short-circuit natural frequencies are determined by sweep frequency measurements, in addition to measuring effective resistance, shunt capacitance and inductance, at the terminals. The proposed method aims at utilizing the measured data to iteratively synthesize a lumped-parameter ladder network, corresponding to each set of measurement. Comparison of such synthesized circuits with a reference (or fault-free) circuit reveals the location, quantum, and nature of fault. Results presented demonstrate the potential of this method.     

A basic study on the effect of voltage stress on a water droplet on a silicone rubber surface

Observations and analyses have been conducted on the behavior of water droplets deposited on the surface of polymer insulators. As an index to characterize the repellency of water droplets on the polymer surface, the contact angle was measured for different situations. Experiments were conducted to see the behavior of water droplets of different volumes and their size distribution on silicone rubber. Electric field strength calculation was performed to analyze the effect on water droplets. Finally, effects of the Maxwell stress and the Coulomb?s force were compared, to conclude that, even if there is some true charge on the water droplet, the Maxwell stress is predominant.     

Movement and evaporation of water droplets under conditions typical for heat-exchange chambers of contact water heaters

The macroscopic regularities and integrated characteristics of the motion and evaporation of sprayed water droplets in the field of high-temperature (1100 K) combustion products under the conditions typical for water heaters of contact type (economizers) were studied using a cross-correlation complex working on the basis of panoramic optical methods (particle image velocimetry, particle tracking velocimetry, shadow photography) and high-speed (10⁵ fps) Phantom video cameras. High-speed video recording devices with specialized software were used for continuously monitoring the motion and evaporation of droplets. Titanium dioxide nanopowder tracer particles were introduced to determine the rate of high-temperature gases. The characteristic distances covered by water droplets before their full retardation in the counter-flow of high-temperature combustion products were determined. The integrated dependences were obtained, and the main characteristics of evaporation were determined, which allow one to predict the intensity of the phase transformations of droplets (with sizes of 0.05–0.5 mm) and the distances covered by them before they completely turn in the opposite direction under the conditions corresponding to the heat-exchange chambers of contact water heaters: the vapor-droplet rate 1–5 m/s, gas flow rate 0.5–2 m/s, and gas temperature ~1100 K. Approximating expressions were derived to predict the characteristics of the processes. The performance of the economizers under study can be significantly increased by using the obtained experimental dependences, the corresponding approximating expressions, and the resulting conclusions. Conditions were determined under which the influence of phase transformations on retardation exceeds the contribution of the counter-motion and active retardation and evaporation of water droplets occur in the heat-exchange chambers of contact water heaters of typical sizes.     

An experimental study of acoustic vibration effects in opticalfiber current sensors

This paper presents experimental results comparing the susceptibility of two different optical fiber current sensors to environmental acoustic vibrations. Of the two sensors that are tested, one employs a uni-directional current detection scheme, and the other a bi-directional in-line Sagnac interferometer. Acoustic vibrations are applied to various optical components of the two different types of current sensors