基于继电保护隐性故障的电力系统连锁故障分析

继电保护隐性故障与显性故障相比危害性更大,因为在不受外界干扰的情况下,继电保护隐性故障不会影响系统的运行,但是一旦有干扰,隐性故障就会马上变成显性故障,影响系统的正常运行,进而出现了连锁故障,造成了更大严重的损失。本文首先介绍了引起故障的因素,进而概述了继电保护隐性故障的危害,最后探讨了其规避方法,仅此提供借鉴。     

基于模型的飞行器电源故障诊断与故障模式识别

设计了基于模型的电源故障诊断原型。它由电源各器件的正常工作模型,故障模型,冲突求解模块,HS树生成和修剪模块,故障信息报告和故障模式识别模块等组成。利用电源系统正常工作模型,实现了故障定位隔离功能。论证了仅仅使用正常工作器件就可以推理出诊断解中各个故障器件的参数值,将这些参数和故障模型相比较,能够识别故障模式。诊断结果表明本文能有效地进行故障定位并能识别故障模式。     

索纳塔轿车动力不足故障分析

简要分析了加速不良故障与动力不足故障的区别、加速不良故障与动力不足故障的可能故障原因、索纳塔轿车动力不足故障的检修过程,最后总结出了一种行之有效的、适用于电控轿车动力不足故障的检修思路。     

基于配电网抢修指挥中快速研判故障的方法分析

配网运行过程中容易出现多种故障问题,重视配网故障抢修工作,寻找有效的故障研判方法,提高故障研判工作效率,及时、准确地定位故障,无论对于配网自身还是用户都具有十分积极的意义。本文分析了配网故障抢修中存在的问题,并探究了配网抢修中故障研判的方法。     

齿轮传动系统断齿故障的机理研究

研究了含断齿故障的4自由度齿轮系统的动力学机理。考虑了断齿故障会引起齿轮系统微小的不平衡,及断齿故障对系统啮合刚度的影响,综合建立了齿轮—转子—轴承模型。数值仿真了故障信号,并通过时域图、相轨迹、Poincaré截面图及频谱分析研究了断齿故障引起的响应,及断齿故障的演化对系统动力响应的影响。最后实验模拟了齿轮断齿故障,通过实测振动信号的振动特征能够验证理论分析的结果,从而说明断齿故障理论模型的合理性,能为齿轮系统断齿故障的诊断提供理论依据。     

基于光纤光栅传感器的结构故障定位方法

提出了一种实现结构故障定位和故障实时监测的新方法.该方法利用光纤光栅传感网络测量结构应变,得到结构的挠度矩阵,分析故障前后挠度矩阵变化,计算得出故障定位向量,进而确定损伤区域,实现了结构故障准确定位和健康状况实时监测.实验结果表明,上述方法大大提高了故障定位的准确度和实时性.     

电气设备故障分析及检修技术

电气设备出现的故障是多种多样的,同一种故障可能会出现很多种不同的现象,不同类的故障又有可能出现相同的故障现象,像这种具有统一性和多样性的故障现象,给检修故障带来了困难性和复杂性。故障现象是查找电气故障的起点,也是基本依据。因此．要对故障现象的故障分析,找出故障现象中最要的方面和典型方面,查找出故障发生的具体时间和具体地点,具体环境。     

数字调幅发射机的欠激励故障的原因与维护

欠激励故障是DAM中波发射机经常出现的故障,它属于6类故障中的第二类故障,导致二类欠激励故障的原因较多,处理起来比较复杂。该文结合DAM10 kW中波发射机的实际使用情况细致地分析了数字调幅中波发射机产生欠激励故障的原因,并依据平时积累的经验,对处理欠激励故障的各种方法进行了总结,叙述了解决欠激励故障的各种方法和对策,提供给维护人员指导和参考。该文以10 kWDAM中波发射机为例,介绍了该类发射机有关欠激励故障的检修情况。     

一起电容器故障及处理

介绍2号电容器故障情况,分折了产生故障的原因,提出了相应的故障处理.     

航空发动机振动故障模式的量化方法研究

为快速、高效地排除复杂系统的振动故障,本文提出了振动故障模式的量化方法,可基于量化结果进行振动故障模式的重点验证。分析了振动故障树的技术特点,指出其不适用于复杂系统的振动故障分析;从故障模式的发生概率、故障模式的可验证性等维度对振动故障模式进行量化;结合某航空发动机核心机的振动故障,给出了振动故障模式量化方法的具体应用。实践证明振动故障模式的量化方法是可行、有效的,且具有较高的工程应用价值。     

容克式空预器漏风故障分析及处理

容克式空气预热器是大中型电站锅炉上广泛采用的尾部换热设备,漏风率高是该类设备常见故障。本文对漏风原因进行分析,提出密封间隙调整和加强吹灰治理等对策,从而有效降低空预器漏风率。     

空气源热泵回收空调系统排风能量的节能利用探讨

文章对目前空调系统排风中能量回收利用过程中存在的不足进行了理论分析和相关的技术数据比较,提出了基于空气源热泵空调排风的深度节能利用方案,即把空调系统排风引入到空气源热泵室外换热器,利用空调系统的排风具有的能量来加强空气源热泵室外换热器的换热强度,从而提高空气源热泵的制冷、制热系数和机组的制冷(热)量,减少电能消耗。该方案在技术上可行,初投资小、回收年限短、能量回收率高(可以达到100%)、节能效果显著。     

健康节能型空调器

健康和节能是空调器近十年来的研究主题,也是今后的发展方向。本文介绍一种既健康又节能且便于实施的空调器,即当室外空气温度低于室内温度设定值时,自动停止空调器内压缩机和室外机风机的运转,通过室内机风机将低于室内温度设定值的室外新鲜空气送入室内进行降温,室内空气质量得到改善,有利居室内人员的健康,此时只有室内机风机运转,空调器的消耗功率仅为几十瓦,与空调器内压缩机及室外风机同时运转时所消耗近千瓦功率相比,节省了大量能源,达到既健康又节能的目的。     

Centrifuge modeling of air sparging - a study of air flow through saturated porous media

The success of air sparging as a remedial technology for treatment of contaminated aquifers is well documented. However, there is no consensus, to date, on the mechanisms that control the flow of injected air through the saturated ground. Currently, only qualitative results from laboratory experiments are available to predict the zone of influence of a sparging well. Given that the patterns of air flow through the soil will ultimately determine the efficiency of an air sparging treatment, it is important to quantify how sparged air travels through a saturated porous medium. The main objective of this research is to develop a model that describes air transport through saturated porous media. This paper presents results from an ongoing study that employs centrifuge modeling to reproduce in situ air sparging conditions. Centrifuge testing is an experimental technique that allows reduced-scale duplication, in the laboratory, of the stresses and pressure distributions encountered in the field. In situ conditions are critical in the development of actual air flow patterns. Experiments are being conducted in a transparent porous medium consisting of crushed borosilicate glass submerged in fluids of matching indices of refraction. Air is observed as it flows through the porous medium at varying gravitational accelerations. Recorded images of experiments allow the determination of flow patterns, breakthrough velocities, and plume shapes as a function of g-level and injection pressure. Results show that air flow patterns vary from fingering, at low g-levels, to pulsing at higher accelerations. Grain and pore size distribution of the porous medium do not exclusively control air flow characteristics. Injector geometry has a definite effect on breakthrough velocities and air plume shapes. Experiments have been conducted to compare the velocity of air flow through the saturated porous medium to that of air in pure liquids. Results show that the velocity of air through the medium is lower than that in the pure fluid, as expected. At high g-levels however, plume breakthrough velocities are proportional to the velocity of the air in the pure fluid.     

Analysis of an air cycle refrigerator driving air conditioning system integrated desiccant system

This study presents theoretical investigation on the performance of air cycle refrigerator driving air conditioning system integrated desiccant system. Total system performance is evaluated and the system feasibility is examined. The system has such characteristics that (1) safe material of air and water are used as a refrigerant, (2) waste heat from air cycle refrigerator performs the regeneration of desiccant material for energy saving. It has been clarifying that (1) controlling the evaporative cooling process in air washer, the system can operate for a wide range of cooling loads, (2) the total coefficient of performance on air conditioning system is better than the conventional vapor compression system with reheating coil, and (3) the system performance highly depends on the ratio of the amount of outdoor intake air to the supply air.     

高大空间空气处理单元气流组织特性分析

高大空间空气处理单元是一种新型的分散式高大空间空调末端,可有效改善冬季室内温度分层现象。以武汉市某火车站候车厅为例,采用CFD模拟方法对高大空间空气处理单元的不同送风角度和送风口尺寸下的冬季候车厅温度分布进行模拟,并与采用分层空调系统时的温度分布进行对比分析,该末端系统可减小33.3%的垂直温度差,进而减小21.3%的热负荷。本研究结果将为高大空间空气处理单元的实际应用提供一定的指导与参考。     

R290空调器系统混空气实验研究

利用实验研究R290空调系统混合空气后运行参数的变化。研究结果表明,R290空调系统混入空气后,其运行压力及运行电流增大,其中,电流及高压压力与混入空气的质量呈近似正比关系变化。小充注量系统的运行压力对混入空气更敏感。另外,空调器安装及运行过程中,即使在异常情况下,可进入空凋系统内部的空气量也是有限的,系统内R290的浓度远高于其爆炸极限的上限,系统内部温度低于R290的引燃温度,系统运行安全。     

Differences between alveolar air and mouth air

Our breath contains an intraoral and an alveolar part, the latter being the last to be exhaled. As such, major differences in composition can be expected, with for alveolar air the inclusion of more metabolic compounds released during the blood-air exchange. This study explored the differences between breath air from the oropharynx and from the lungs in healthy volunteers. Mouth and alveolar air of 40 volunteers was analyzed using gas chromatography-mass spectrometry, together with a sample of room air. A chromatogram of a single person contains on average 145 different compounds. Altogether, 618 compounds were detected. A total of 35 compounds were common to all volunteers. The number of compounds was significantly higher in mouth air than in alveolar air. For 47 compounds, very significant differences in detection/concentration were recorded. Gas chromatography-mass spectrometry offers a detailed overview of the compounds in a person's breath. One should be aware of the distinction between alveolar air and oropharyngeal air.     

The effectiveness of air bags

Previous research has shown that the installation of air bags in vehicles significantly reduces crash related deaths, but these analyses have used statistical techniques which have not been capable of controlling for other major determinants of crash survival. This study analysed data from the US FARS database of fatal crashes using conditional logistic regression which is simultaneously able to estimate occupant protection effects for a range of variables. Results of the analysis provided a comparative quantification of both the effect of the air bag as well as other well known determinants of occupant crash survival (age, seat belt use, and gender). When potentially confounding variables were controlled, both the driver and passenger side air bag devices were shown to significantly reduce the probability of death in direct frontal collisions, but the effect size calculated was small compared to the effect of the seat belt. The effect size may also be very small in absolute terms depending on the severity of the crash involved. Given the limited benefit of the air bag, efforts to promote air bags seem particularly difficult to justify in countries such as the United States where the vastly superior occupant protection of the seat belt is under-utilised.     

空分设备调整阶段进塔空气量波动分析及操作

空分设备启动进入调整阶段时,常常会发生进塔空气量周期性波动的现象。文章分析了原因及其对空分设备安全、稳定运行的危害,并从生产实际出发,提出了相应的操作措施。