柴油机轴瓦损伤的故障分析

针对柴油机在工作中常见的轴瓦故障现象及特征,阐述了轴瓦损伤故障判断与检查的方法,分析了造成这些轴瓦损伤的原因,最后对避免出现类似故障提出了几点安装和维护的对策。     

某二冲程发动机轴瓦失效分析及改进

某二冲程水平对置柴油机在性能试验中,由于内连杆始终受压,使连杆轴瓦的润滑状况较差,连续两次出现了连杆轴瓦烧瓦失效,针对故障现象,分析造成轴瓦损伤的原因,提出了轴瓦改进措施并在试验中实施,最终解决烧瓦故障,保证了试验顺利进行。     

柴油机轴瓦故障现象及原因分析

针对机车柴油机轴瓦故障现象，对故障原因进行了分析，表明引起轴瓦故障的原因主要是合金层碾片、合金层剥离、轴瓦工作表面穴蚀、磨损与拉伤及轴瓦高出度问题，并提出了相应的预防措施。     

发动机烧瓦的原因及防止措施

发动机烧瓦的原因及防止措施鞍钢矿山公司运输设备修造厂田谷蓁烧瓦是发动机在使用过程中常见的主要故障之一。发动机烧瓦所带来的损伤或后果往往比较严重；轻者，需要更换轴瓦和修整曲轴；重者，则需要更换轴瓦及曲轴，修复或更换缸体。所以，烧瓦不仅会因停机待修而影响...     

240、280柴油机轴瓦失效故障的分析与预防措施

通过对机车柴油机轴瓦几类典型失效故障的分析,探索了轴瓦失效故障的原因和规律,并针对各类型故障提出了相应的判定和预防措施。     

300 MW机组汽轮机轴瓦油膜振荡分析与处理

天津华能杨柳青热电有限责任公司8号机组汽轮机运行中3号轴瓦发生故障,通过分析轴瓦Y向振动趋势图、轴承Y向振动异常点频谱图,确定振动原因为油膜激振。分析出现故障的原因为轴承间隙配合超标、轴瓦压比小、轴瓦载荷分布不合理等。并采取调整轴瓦压比、减小轴瓦顶隙、调整轴瓦标高等手段来提高轴瓦稳定性,进而消除油膜振荡的隐患。     

1000MW机组低压缸轴瓦振动故障原因分析及治理

文章介绍了某电厂1 000 MW超超临界、单支撑汽轮机组在运行中发生的轴瓦振动故障,分析了轴瓦振动故障发生的原因并给出了成功治理的措施;在治理轴瓦振动的同时,解决了低压缸动静碰磨以及低压缸膨胀不畅的问题。振动故障的识别方法和处理措施对同类型机组振动故障的诊断和处理具有参考意义。     

连杆轴瓦的损伤剖析与解

通过检查连杆轴瓦在装配和试验中产生的损伤状态，进行寿命分析研究，采取有效的方法，提高连杆轴瓦的质量，降低消耗，提高柴油机的寿命和工作可靠性。     

柴油机连杆大头轴瓦磨损故障温度监测部位优化仿真研究

基于无源无线温度测量的监测方法,针对连杆大头轴瓦磨损故障温度监测部位的优化问题,建立了连杆大头轴瓦弹流润滑仿真模型,探究不同磨损程度下轴瓦接触力的变化规律和温度显著变化区域的分布情况.仿真计算结果给出了温度监测的理论优化部位,并与工程案例的实际情况相比较,结果一致.研究成果可为基于温度测量的连杆大头轴瓦磨损故障监测与诊...     

普及轴瓦失效预防和分析知识减少轴瓦使用故障

1 引 言 轴瓦早期失效是在其正常磨损寿命的初期或中前期发生的非正常损坏它会严重危及发动机的工作可靠性并造成巨大的经济损失这也是长期困扰内燃机行业的一大技术难题 国外轴瓦行业和主机厂都非常重视轴瓦失效分析研究经过长期努力通过理论与实践的结合总结了轴瓦非正常失效的各种规律积累了丰富的经验很多国际著名的滑动轴承公司和主机厂都将它们在这方面取得的成果专门编写成包括各种轴瓦失效分析图例的手册指导用户对轴瓦进行正确使用保养故障预防和分析以减少轴瓦故障的发生机率 与国外相比国内轴瓦失效分析研究工作一直是…     

New capability of graphene as hydrogen storage by Si and/or Ge doping: Density functional theory

We studied the adsorption of water molecules via the density functional theory on the pure and silicon and/or germanium doped graphene. We investigated the electrostatic surface potential of the structures to predict the possible interactions. Also, we examined the interaction between every possible side of the water molecule and possible sites of the pure and doped graphene. There was no interaction between the water molecule and the graphene. The only interaction was between the oxygen atom of the water molecule and the doped atoms. We also studied the decomposition of the water molecule on these doped graphene sheets and the possible intermediates and transition states and reaction pathway for the decomposition process. We calculated the interaction energies for the adsorption steps and the thermodynamic parameters for all steps of reaction pathway. The results showed that the adsorption of the water molecule on silicon and/or germanium doped graphene. Also, the decomposition of one of the hydrogen atoms of water molecule was thermodynamically favored at room temperature.     

Research progress on hydrate plugging in multiphase mixed rich-liquid transportation pipelines

The plugging mechanism of multiphase mixed rich-liquid transportation in submarine pipeline is a prerequisite for maintaining the fluid flow in the pipeline and ensuring safe fluid flow. This paper introduced the common experimental devices used to study multiphase flow, and summarized the plugging progress and mechanism in the liquid-rich system. Besides, it divided the rich-liquid phase system into an oil-based system, a partially dispersed system, and a water-based system according to the different water cuts, and discussed the mechanism of hydrate plugging. Moreover, it summarized the mechanism and the use of anti-agglomerates in different systems. Furthermore, it proposed some suggestions for future research on hydrate plugging. First, in the oil-based system, the effect factors of hydrates are combined with the mechanical properties of hydrate deposit layer, and the hydrate plugging mechanism models at inclined and elbow pipes should be established. Second, the mechanism of oil-water emulsion breaking in partially dispersed system and the reason for the migration of the oil-water interface should be analyzed, and the property of the free water layer on the hydrate plugging process should be quantified. Third, a complete model of the effect of the synergy of liquid bridge force and van der Waals force in the water-based system on the hydrate particle coalescence frequency model is needed, and the coalescence frequency model should be summarized. Next, the dynamic analysis of a multiphase mixed rich-liquid transportation pipeline should be coupled with the process of hydrate coalescence, deposition, and blockage decomposition. Finally, the effects of anti-agglomerates on the morphological evolution of hydrate under different systems and pipeline plugging conditions in different media should be further explored.     

烘焙对生物质热化学转化特性影响的研究进展

生物质是可再生能源的重要组成部分,储量巨大,但其含水量高、能量密度和热值低等缺点致使其研磨难度大、存储运输不便,难以资源化利用。本文对烘焙预处理技术的过程及特点、能耗分析和较为理想的烘焙标准进行了简述;并重点阐述了烘焙对生物质燃烧、热解和气化特性影响的研究进展。经烘焙处理后的生物质在炉膛内可快速、稳定燃烧,炉内温度迅速升高,产生的烟气量减少;热解产生的生物质焦油中水和乙酸含量明显减少,苯酚含量增加,热值总体升高;气化合成气品质明显提升,能量密度增大,总气化效率显著提高。此外,对烘焙预处理技术在城市固体废弃物处理的应用进行了简要的概述,并对其在生物质和城市固体废弃物研究方向上进行了展望。     

Semi-analytical method for heat and moisture transfer in packed bed of silica gel

A semi-analytical model for the heat and mass transfer of adsorption and desorption processes of the vertical solid desiccant packed bed dehumidifier is presented on the basis of quasi-steady state assumption, and is solved using close form integration with the limits equivalent to bed and time increments, and numerically by Runge-Kutta Fehlberg and forward scheme finite difference techniques. The most important parameters during the dehumidifier operation, namely, (i) exit air temperature and humidity, (ii) axial temperature distribution in the bed and (iii) water content are evaluated. Stability of the semi-analytical method is investigated and found that the main parameters affecting the model stability are the bed and time increments size. A dimensionless parameter combining time and bed increments size and air velocity named velocity ratio is defined and investigated. It is found that when the velocity ratio equals the ratio of particle diameter to bed length, the method is stable, and as the velocity ratio is made smaller beyond the stable velocity ratio, the results remain unchanged. The results of semi-analytical and numerical models agree well with the experimental results for both desorption and adsorption processes. Using the proposed semi-analytical model, the minimum and maximum relative errors for exit air temperature are 2.24% and 11.78%, respectively and for exit air humidity the minimum and maximum errors are 3.79% and 27.17% respectively.     

Energy use in Indian household sector – An actor-oriented approach

Over the years, significant changes have taken place with regard to the type as well the quantity of energy used in Indian households. Many factors have contributed in bringing these changes. These include availability of energy, security of supplies, efficiency of use, cost of device, price of energy carriers, ease of use, and external factors like technological development, introduction of subsidies, and environmental considerations. The present paper presents the pattern of energy consumption in the household sector and analyses the causalities underlying the present usage patterns. It identifies specific (groups of) actors, study their specific situations, analyse the constraints and discusses opportunities for improvement. This can be referred to “actor-oriented” analysis in which we understand how various actors of the energy system are making the system work, and what incentives and constraints each of these actors is experiencing. It analyses actor linkages and their impact on the fuel choice mechanism. The study shows that the role of actors in household fuel choice is significant and depends on the level of factors – micro, meso and macro. It is recommended that the development interventions should include actor-oriented tools in energy planning, implementation, monitoring and evaluation. The analysis is based on the data from the national sample survey (NSS), India. This approach provides a spatial viewpoint which permits a clear assessment of the energy carrier choice by the households and the influence of various actors. The scope of the paper is motivated and limited by suggesting and formulating a powerful analytical technique to analyse the problem involving the role of actors in the Indian household sector.     

考虑黏性效应的半潜浮式风力机动力特性研究

对半潜浮式风力机动力特性进行研究，推导考虑黏性阻尼的动力学方程及传递函数。对黏性效应的影响及其计算方法进行探讨，对比附加阻尼矩阵法、Morison单元法的优缺点，并提出考虑黏性阻尼效应水动力计算的混合法，在此基础上对半潜浮式风力机气动-水动-锚泊全耦合动力响应进行分析。结果表明：黏性效应主要影响共振周期附近的响应值，在数值分析时不可忽略；附加阻尼矩阵法在考虑水平面内运动黏性阻尼时有所不足，且无法考虑黏性效应对共振周期的影响，Morison单元法在考虑垂荡、转动黏性阻尼时有所不足，混合法是考虑黏性阻尼水动力计算的更有效方法；该半潜浮式风力机垂荡和纵摇响应主要受波浪控制，而水平面内运动受风、浪、流联合作用的影响；浮式风力机运动和加速度的最危险工况可发生在发电工况时，最大锚链张力发生在极端环境条件时。     

Theoretical and experimental investigations of a liquid desiccant filmed cellulose fibre heat and mass exchanger

This paper presented theoretical and experimental investigations of a liquid desiccant filmed cellulose fibre heat and mass exchanger, a new type of exchanger with the potential to be an alternative to a conventional exchanger. Owing to the complexity of the desiccant assisted heat and mass transfer and difficulty in determining its associated parameters, work started from the simulation of a clear fibre exchanger by developing a dedicated numerical model, and its validation by using the data from the manufacturer of the exchanger. Further to this, laboratory testing was carried out with the same exchanger, but filmed with a liquid desiccant fluid, i.e. LiCl. Comparison between the data of the clear and desiccant filmed exchangers suggested the use of correction factors for heat and mass transfer resistances with desiccant operation. A revised model for the desiccant filmed exchanger was then established taking into account the correction factors. By using the updated model, influence of geometrical sizes and operating conditions of the liquid desiccant filmed exchanger on the exchanger efficiency were studied and the optimal values of these were obtained. The results indicated that the exchanger efficiencies (heat, mass and enthalpy) are largely dependent upon the exchanger channel length, air flow rate and less related to the exchanger channel height, intake air temperature and intake‐to‐outgoing air moisture content difference. It was also suggested that the air speed across the channels should be in the range 0.5–1.5 m s^?1. The height of air channel (passage) should be set at 6.5 mm or below and its length should be 1.0 m or more. A simulation was carried out under UK typical summer operation conditions, i.e. the intake air streams at 30°C db and 70% rh and outgoing air streams at 24°C db and 50% rh, and the results indicated that the exchanger with the above recommended geometrical sizes can achieve an energy efficiency of 87%, which is 30% higher than for non‐desiccant filmed operation. Copyright © 2009 John Wiley & Sons, Ltd.     

Exergoeconomic analysis and optimization of basic,dual-pressure and dual-fluid ORCs and Kalina geothermal power plants: A comparative study

In present work, the basic, dual-pressure and dual-fluid ORCs and Kalina cycle for power generation from the geothermal fluid reservoir are compared from energy, exergy and exergoeconomic viewpoints. To do so, first thermodynamic models are applied to the considered cycles; then by developing cost flow rate balance and auxiliary equations using SPECO method for all components, the cost flow rate and unit cost of exergy for each stream are calculated. The results show that the turbine in basic and Kalina cycles and low pressure turbine in dual-pressure and dual-fluid ORCs have the maximum value of sum of total cost rate associated with exergy destruction and total capital investment cost rate. Thus, more attention should be paid for these components from the exergoeconomic viewpoint. The cycles are optimized to obtain maximum produced electrical power in the cycles as well as minimum unit cost of produced power. The optimization results show that among the considered cycles, dual-pressure ORC has the maximum value of produced electrical power. This is 15.22%, 35.09% and 43.48% more than the corresponding values for the basic ORC, dual-fluid ORC and Kalina cycle, respectively in optimal condition. Also Kalina cycle has the minimum value of unit cost of power produced and its value in optimum state is 26.23%%, 52.09% and 66.74% less than the corresponding values for the basic ORC, dual-pressure ORC and dual-fluid ORC, respectively in optimal condition. Finally a parametric study is carried out to assess the effects on thermodynamic and exergoeconomic parameters of the considered cycles of operating pressures and ammonia mass concentration.     

Recent research progress on polymer electrolytes for dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) have attracted large attention due to their easy fabrication, low cost and high conversion efficiency. Electrolytes play an important role in the photovoltaic performance of the DSSCs and many efforts have been contributed to study different kinds of electrolytes with various characteristics such as liquid electrolytes, polymer electrolytes and so on. Because the leakage and the volatilization of liquid electrolytes hinder their practical applications in the DSSCs, polymer electrolytes with high ionic conductivity, excellent thermal stability and long-term stability of the DSSCs based on them are alternatives to liquid electrolytes especially for the quasi-solid-state DSSCs. In this paper, research on solid polymer electrolytes is summarized and the influence of salt concentration on ionic conductivity of solid polymer electrolytes is described and thoroughly explained. On the other hand, the advantages of gel polymer electrolytes (GPEs) are introduced. The factors affecting the ionic conductivity of GPE and the performance of their DSSCs, consisting of the polymer concentration and type, the iodide salts, the solvents and the temperature are discussed. The tendency and the reasons of their influence are expounded in detail. To enhance the properties of GPE, many strategies are taken such as the fabrication of porous structure in the GPE membrane, the incorporation of proton donors, the introduction of inorganic nanoparticles and the addition of pyridine derivatives. Their improving effect and the causes for the enhancement are set forth.