甲醇发动机燃烧特性研究

甲醇发动机开发过程中发动机的燃烧特性研究至关重要,为了获得最佳的发动机性能,对进气道喷射甲醇发动机的燃烧特性进行了试验研究,并与汽油机进行了对比。结论显示:在相同循环油量的条件下,与汽油机相比,甲醇发动机的燃烧速率较快,压力升高量较大,燃烧压力峰值较高,着火延迟期短,下止点附近缸内平均温度较低,循环变动较小,泵气损失小,摩擦损失大,有效热效率可提高4%～5%。     

基于双区模型的汽油机燃烧过程可用能及不可逆损失分析

为考察汽油机燃烧过程中的能量转化规律,建立了汽油机燃烧过程的热力学双区模型,考虑了可用能变化及不可逆损失.求解了燃烧期间缸内压力及温度随曲轴转角的变化规律、缸内工质可用能及不可逆损失的变化规律,分析了未燃区和已燃区的可用能以及与放热规律的关系.工质可用能转化包括对外做功、传热转移可用能和可用能损失3部分,燃烧结束时,工质总可用能占燃烧初始总可用能的比例约为47.0%.在整个燃烧阶段,燃烧可用能损失约为18.4%,由于向缸壁传热造成的可用能损失约为12.3%.缩短燃烧持续期和适当推后着火有利于降低燃烧过程可用能不可逆损失.     

利用废气滞留改善缸内直喷汽油机部分负荷性能的研究

废气滞留比传统的废气再循环具有更好的稀释和加热混合气作用,有利于减小汽油机中小负荷泵气损失,降低油耗.在一台缸内直喷汽油机(GDI)上对比研究了部分负荷下利用负阀重叠(NVO)产生废气滞留对于发动机性能的影响.结果表明,利用废气滞留方法可使发动机油耗降低5%～16%,并且随着负荷减小节油效果明显.分析表明,废气滞留可以提高进气歧管压力,明显降低泵气损失;混合气温度提高促进燃烧更完全,使燃烧效率得以提高;但燃烧速度会有一定程度降低,循环波动有所增大;综合作用下使得有效热效率提高.同时,废气滞留作用可降低缸内直喷汽油机HC、CO排放,尤其可显著降低NOx排放达70%以上.     

汽油机双火花塞燃烧室点火控制策略的测试分析

为分析158FMI汽油机双火花塞燃烧室对发动机缸内燃烧放热速率、循环变动和爆震燃烧等的影响,设计了五种不同的单/双火花塞点火控制策略。燃烧测试诊断证明:双火花塞可有效促进缸内燃烧过程,其最高燃烧压力和压力升高率均大幅升高,最高燃烧压力对应曲轴转角提前,燃烧持续期缩短,循环变动率降低;在低负荷工况,双火花塞加速缸内燃烧、缩短燃烧持续期、提高燃烧稳定性和降低循环变动率的效果更加显著。测试数据的分析揭示如下现象:全负荷工况双火花塞加速缸内燃烧的总体效应主要体现在已燃质量分数10%~50%的前期燃烧阶段,双火花塞比单火花塞更易出现爆震燃烧,双火花塞提升发动机动力性和燃油经济性的潜力很大程度取决于点火提前角的匹配优化;而双火花塞同相点火和非同相点火对缸内燃烧特性的影响并不明显。基于点火控制策略的优化,158FMI双火花塞汽油机通过热力学循环效率的提高获得5%~6%的动力性提升。     

对置活塞二冲程汽油机燃烧特性试验

通过对置活塞二冲程缸内直喷汽油机进行原理样机燃烧特性试验,研究了对置活塞运动相位差、扫气压力、点火正时和点火方式等对燃烧过程和整机性能的影响规律.对置活塞二冲程汽油机缸内放热规律试验结果与传统汽油机一致,可分为火焰发展期、快速燃烧期和燃烧后期.对置活塞运动相位差过小会导致缸内扫气效率较低、残余废气量较高,不利于燃烧过程的组织;同时,对置活塞相对运动速度过快会导致内止点过后气缸工作容积变化率较大,缸内压力和温度下降较快.对置活塞运动相位差为15°,CA时,可有效改善扫气过程和燃烧组织.随着转速的升高,需要提高扫气压力,在提高扫气效率的同时增加混合气质量,提高燃烧速率.扫气压力为0.12,MPa时可兼顾中、高转速下缸内扫气过程和燃烧组织.对置活塞采用平顶结构时,需要配合双火花塞对置点火且点火提前角为20°,CA,可保证中、高负荷具有最高的指示热效率.     

高海拔条件下压气机结构优化及其对柴油机性能的影响

基于二级可调增压柴油机高海拔性能试验,采用计算流体力学(CFD)和柴油机工作过程计算方法,开展高海拔条件下压气机叶轮结构优化及其对柴油机性能影响的研究.研究结果表明:海拔5 500 m,压气机叶轮主叶片及分流叶片前缘前掠6.27°、分流叶片向主叶片压力面偏折12.09°,压气机叶轮流道内流动损失明显降低,出口处流动稳定性提高,压比、效率及流量范围分别提高4.16%、2.63%及6.58%;压气机叶轮优化后,二级可调增压柴油机中低转速燃烧过程得到明显改善,滞燃期和燃烧持续期缩短;柴油机1 200 r/min全负荷工况最高燃烧压力升高9.53%,累计放热量提高8.78%,转矩提高5.82%,燃油消耗率降低4.42%.     

空燃比选择对稀燃汽油机指示效率影响模拟分析

搭建汽油机数值模型,按照汽油机燃烧效率随空燃比增大而升高、缓慢下降及大幅下降等现象,将空燃比划分为3个阶段,分析了不同阶段内工质绝热指数、压缩比、燃烧持续时间及传热损失对指示效率的影响规律.结果表明,随空燃比升高,绝热指数对指示效率的影响变小,提高压缩比使得末端气体温度升高,加长燃烧持续时间,导致热量转化为功的能力下降.综合分析可知,在第2阶段实现汽油机稀燃其指示效率增幅较大.     

PFI/DI喷射对米勒循环汽油机燃烧特性的影响

为削弱泵气损失大、压缩比和工质比热容低等问题对汽油机常用部分负荷热效率的制约作用,基于配备进气道喷射(portfuelinjection,PFI)和缸内直喷(directinjection,DI)双喷系统的高压缩比米勒循环汽油机,系统探究了进气门早关策略对汽油机部分负荷热效率的影响规律.研究表明,应用米勒循环可有效调控歧管压力和泵气损失,通过综合优化气门相位、点火策略和节气门开度,相较于原机在2000 r/min,平均指示有效压力(IMEP)0.36 MPa工况指示热效率由32.4%提升至36.4%.针对高压缩比米勒循环小负荷燃烧稳定性恶化问题,提出采用分层火焰引燃(stratifiedflameignition,SFI)混合燃烧技术实现对燃烧放热过程的优化控制.研究表明,SFI燃烧可有效提高燃烧稳定性,平均指示有效压力的循环变动COVIMEP降幅达64.9%.而后期自燃的参与使得放热更为集中迅速,指示热效率由纯米勒循环下的36.4%提升至37.8%.     

进气压力和喷油对二冲程汽油机稀燃特性的影响

利用三维数值模拟软件CONVERGE研究了在循环喷油量和点火时刻固定的大负荷条件下,进气压力对二冲程直喷汽油机缸内燃油分布和稀燃特性的影响.结果表明,在相同的第2次喷油比例下,随着进气压力的升高,气缸内燃油浓度降低.在相同的进气压力下,随着第2次喷油比例的增加,火花塞附近的燃油浓度先减小后增加.在第2次喷油比例为70%,时燃油分层形式最有利于燃烧.在相同的第2次喷油比例下,随着进气压力的升高,着火时刻逐渐提前,燃烧持续期先略有缩短后又增长,最大压力升高率先增加后减小.在相同的进气压力下,随着2次喷油比例的增加,着火时刻先略有推迟后提前,燃烧持续期先增长后缩短,最大压力升高率先减小后增加.气缸内燃油浓度和温度分层形式影响火焰传播过程中气缸周围混合气的自燃特性.提高进气压力能降低气缸周围混合气的浓度,抑制自燃的发生.     

废气再循环率对高压缩比增压直喷汽油机燃烧与排放特性的影响

以一台采用废气再循环（exhaust gas recirculation,EGR）技术的增压直喷汽油机为研究样机，试验研究了高压缩比15.0时不同EGR率（0%、5%、10%、15%）下该机的燃烧和排放特性。研究结果表明，与常规的压缩比11.5相比，采用高压缩比15.0时，该机缸内最高燃烧压力升高，点火正时提前，燃烧持续期延长，平均指示压力变动系数增大，有效热效率显著提高；碳氢化合物（hydrocarbon,HC）排放和颗粒物数量增加，CO排放和颗粒物质量降低，NO_x排放略有升高。采用EGR技术能够有效抑制爆震和降低NO_x排放。相同工况下，随着EGR率升高，该机的燃烧持续期延长，平均指示压力变动系数增大，低负荷(制动平均有效压力（brake mean effective pressure,BMEP）为0.5 MPa)下的缸内最高燃烧压力逐渐下降，有效热效率变化不大。高负荷（BMEP为1.0 MPa）下的缸内最高燃烧压力先上升后下降，有效热效率整体呈上升趋势，高压缩比情况下该机EGR率为10%时的热效率最高，为38.45%;CO排放先减小后增加...     

过热器再热器爆漏事故的原因分析及对策

过热器、再热器爆漏事故严重影响了锅炉机组的安全性和经济性,而造成过热器、再热器爆漏事故的主要因素有超温爆管、磨损、高温腐蚀、热疲劳、质量失控等。通过对这些因素的主要原因和爆口特征的分析,提出了一些过热器、再热器爆漏事故的防治措施。     

具有智能化特征的安全稳定分析与控制决策技术

安全稳定预警与控制辅助决策是智能电网调度技术支持系统不可缺少的应用类功能。在分析安全稳定分析与控制决策计算工作特点的基础上,提出安全稳定分析与控制决策支持智能化的主要特征：自动化和自适应性。介绍了自动化的安全稳定分析计算技术,包括输入数据准备、任务执行和输出结果的自动化处理;阐述了自适应电网运行工况、外部环境和硬件运行状态的安全稳定分析技术,包括调整应用功能的输入数据和妥善处理安全稳定性交互影响,以及根据分析计算任务要求动态优化调度计算资源。这些技术已用于安全稳定综合防御系统,提高了分析结果的适应性和分析计算的效率,在电网运行规划、计划安全校核、超短期安全态势预测、调度操作安全校核和在线分析与控制等电网调度运行管理中发挥作用。     

Hydrophilic and hydrophobic materials and their applications

Wettability of a material’s surface plays a significant role in how fluids interact with such surfaces. Wetting behavior is universal but can vary depending on the chemical nature of the solid and liquid phases. Plants and animals adapt to their environment by having evolved special properties. These properties are such as hydrophilic and hydrophobic. Hydrophilic surface has a strong affinity to water and spreading of water on such surface is preferred. The degree of hydrophilicity of the substance can be measured by measuring the contact angle between the liquid and solid phases. Hydrophobic materials are known as non-polar materials with a low affinity to water, which makes them water repelling. A contact angle of less than 90° indicates hydrophilic interaction where as an angle greater than 90° indicates a hydrophobic interaction. More recently, superwetting such as superhydrophilicity has been receiving an increased focus in the literature due to its potential significance. Superhydrophilic surface has a contact angle of less than 5°.

The fabrication of hydrophilic materials can be carried out in two main ways: depositing molecules on surfaces or modification of surface chemistry. Both methods have been successful historically in achieving their intended purposes. Hydrophobic and superhydrophobic materials can be produced with many fabrication methods such as layer-by-layer assembly, laser process, the solution-immersion method, sol-gen techniques, chemical etching, and Hummer’s method.

The applications of such an important property are significant. For example, hydrophilic surfaces can be used in anti-fogging applications, biomedical, filtration, heat pipes, and many others. Hydrophobic and superhydrophobic materials have been successfully applied in many sectors, such as: (I) the removal of petroleum from aqueous solutions, (II) applied to plastic, ceramics, and mesh to contribute to the oil removal from aqueous solutions, (III) hydrophobic layers have a strong self-cleaning effect on plastics, heat pipes, metals, textiles, glass, paints, and electronics, (IV) hydrophobic layers improve the anti-freezing behavior of heat pipes which prevents unwanted build-up and (V) they function as a water and dust protecting coat on electronics.

The presence of this property is historic but there is still a huge potential for development for its applications in many sectors such as water treatment, heat transfer applications, biomedical devices, and many more.     

Defect and impurity diagnostics and process monitoring

The review focuses on four areas of defect and impurity diagnostics: (i) the determination of parasitic resistances, (ii) quantum efficiency analysis including light-beam-induced current measurement systems which use spectrally resolved currents to determine local recombination in solar cells, (iii) methods to determine the recombination properties in solar cell precursors and (iv) techniques suitable for the recognition of the type of impurity or defect, which is responsible for increased recombination. In general, emphasis is on those methods, which are capable of delivering spatially resolved information. The use of the specific metastability features of a defect for its identification is exemplified. In addition, carrier lifetime spectroscopy methods utilising the temperature or the injection dependence of defect recombination are outlined.     

铁道机车车辆轮轨的摩擦磨损与节能降耗

阐述了铁道机车车辆轮轨摩擦磨损的现状;研究了内燃机车车轮、闸瓦和钢轨的消耗数量及相应的维修费用;指出了采用适当的新技术之后,在节能降耗方面会产生显著的经济效益。     

Hydrogen and electricity from water and light

Four self-driven photoelectrochemical hydrogen producers: n-TiO₂/p-CdTe, n-TiO₂/p-GaP, n-SrTiO₃/p-CdTe and n-SrTiO₃/p-GaP were constructed and examined in 1 M NaOH. the current-potential curves of the individual electrodes and the current-cell voltage relationships were measured. Cell current-density measurements versus time demonstrated that the output of each cell is stable for at least 12 h. the n-SrTiO₃/p-GaP cell under xenon light irradiation was the most efficient at 0·7 per cent. the n-TiO₂/p-GaP cell was estimated as the most efficient under solar light at 0·1 per cent. the stability of p-CdTe and its energy gap of 1·5 eV make it a prospect for use as a photocathode in future photoelectrochemical hydrogen producers.     

能源的开发利用与节能

在节能与环保问题成为当今全球性重要研究课题的情况下,笔者对中国能源的现状、新能源开发问题和在用车辆的环保节能问题进行了研究探讨。认为我国应加大开发可再生能源、核能源的力度,开发城市生活垃圾的新能源,找出在用柴油车实现环保节能的一些新措施。     

国内外能耗监测控制管理理论与实践

能耗监测是能源管理中的重要环节,国外不少国家在这方面都进行了积极的努力,制定了一些相关政策,并取得了一部分研究成果.我国于上世纪90年代初就出台了关于能耗监测的有关规定,2007年颁布的《单位GDP能耗监测体系实施方案》规定了能耗监测的主体、主要内容和指标.工业、交通运输和建筑是我国三大“耗能大户”,因此能耗监测研究和管理实践也主要集中在这三个领域.信息技术的发展为工业企业的能耗监测提供了基础平台,运用计算机信息技术对能耗实行现代化管理,成为企业实现信息化管理、降低成本的一种重要手段.道路交通约占我国交通运输业能耗的75％,因而对道路交通能耗的监测是交通运输业能耗监测的主要任务,而对机车能耗的监测是铁路运输能耗监测的主要内容之一.建筑能耗监测主要针对大型公共建筑,通过信息化手段进行信息采集及能耗监测.目前有关能耗监测的研究还处于起步阶段,尚未全面展开,能耗监测技术还不成熟,监测设备也不齐全.今后除了要继续探索能耗监测技术以外,还应重点加强对主要行业能耗监测控制管理体系的研究.     

The roles of science and technology in energy and environment research and development

Countries are becoming increasingly aware of the importance of science and technology in relation to national development and the necessity of formulating a concise science and technology policy. The need to strengthen and orient the scientific and technological infrastructure in line with national development goals, through more effective use of an available qualified work force and the higher education system, is becoming widely recognized. Consequently, appropriate methods of assessing the impact of science and technology on national development are needed so that efforts are concentrated on areas potentially having substantial impacts. Numerous planning studies have been undertaken to this end, particularly by international organizations such as UNESCO, UNIDO, OECD and IEA. This study examines the inter‐relationships of the disciplines of science and technology with energy and environment research and development (R&D) activities, particularly for developing countries. The connections between these topics are discussed along with some basic methods that can be used to exploit the relations. Some illustrative examples are presented. It is anticipated that the present study will serve as a preliminary step for more comprehensive work by providing an example of the utilization of formal methods in formulating science and technology policy for energy and environment R&D. Copyright © 2001 John Wiley & Sons, Ltd.     

火电厂TSI安装调试及常见故障诊断和处理

火电机组TSI探头的安装与调试是一个较为复杂和精细的工作.是火电厂热控安装不可或缺的最重要的组成部分.文章对各种测量探头的原理进行了分析,理论结合实际,将原理图和现场安装图进行对照,通俗易懂.对这些TSI探头在实际安装时应注意的细节问题做了详尽的阐述,同时对试车过程中出现的问题进行了分析并提出了处理措施.对火电机组汽轮机本体热工仪表安装工作有一定的指导意义.