炉内温度速度耦合场声线弯曲特性研究

为了实现声波法测量热物理量场的可靠重建,弄清介质温度和流速对声速的耦合作用机理,采用三角形前向展开法和Lagrangian法建立追踪模型,针对仿真的不同炉膛典型温度场和流场,研究了声波传播路径的弯曲效应,同时建立一维流场模型以从理论角度验证上述方法的可行性和可靠性.结果 表明:炉内烟气温度、流速耦合场对声波传播路径影响复杂,若不考虑声线弯曲,必将导致相应声学法温度场和流场测量重建结果的失真;基于上述不同理论方法计算追踪出的对象场声线分布彼此吻合,证明所建声线追踪模型可靠.     

考虑声波折射的声学锅炉温度场测量技术的研究

根据炉膛断面理想的温度分布函数,给出了二维单峰圆对称模型温度场,数值计算了声波在模型温度场中沿直线路径的传播时间,用声学CT算法进行了温度场的重建仿真。根据光学Fermat原理和数学变分方法建立的声波传播路径的数学模型,数值计算了声波在模型温度场中的折射传播路径,发现声波在非均匀温度场中不沿直线传播,其传播路径朝向温度较高的区域发生弯曲。利用得到的声波实际传播路径,用声学CT算法重建了温度场,结果表明考虑声波折射后建立的声学法二维温度场精确度得到提高。图5参7     

基于声学测温的水冷壁局部超温监测研究

以理论和试验相结合的方法,对锅炉热态时水冷壁附近的温度场及声线分布进行了研究,开发了基于声学测温的水冷壁局部超温监测系统,并在国内某300MW锅炉机组上进行了试验研究.结果表明：声学测温技术应用于水冷壁局部超温监测是完全可行的;锅炉热态时,水冷壁附近的声线会朝着炉膛内高温侧发生弯曲;系统测得的烟气温度作为基准量能很好地反映水冷壁向火侧壁面温度的变化情况;线性扫频信号可以作为监测系统的声源信号,扫频区间在500～3 000Hz为宜;此系统中,互相关时延估计法能准确地计算出声波飞渡时间.     

旋流燃烧室内煤粉多相湍流流动与燃烧的数值模拟

提出了考虑湍流-颗粒反应相互作用的颗粒随机轨道模型,以此为基础建立煤粉燃烧综合理论模型并应用于旋流燃烧室内煤粉多相湍流流动与燃烧的数值模拟.模拟结果给出了气相温度场、速度场与温度脉动均方根值分布、颗粒相温度场、速度场与表观密度场以及颗粒瞬时温度与质量随时间的变化.研究表明,考虑湍流-颗粒反应相互作用对气相与颗粒相温度场的模拟结果有一定的影响,使气相温度分布与实验数据更为接近.     

基于CFD数据库的炉膛压力管道泄漏定位研究

对非均匀温度场内定位方法进行研究,以解决炉膛热态情况下压力管道泄漏定位问题。使用广义互相关方法进行远距离时延值测量实验并进行低信噪比仿真;使用球型插值法进行三维空间定位仿真;在CFD数据库的基础上,假设声波直线传播,使用初值迭代寻优模型对泄漏定位。实验中,传感器相距10 m,仿真环境为-6 db,三维空间深9 m、宽9 m、高5 m。单峰温度场下,将温度场平均与假设声波直线传播的时延值误差对比。结果表明,广义互相关测量时延值在大空间、低信噪比环境下可行;单峰温度场情况下,假设声波直线传播、温度场平均的情况下所得时延值误差分别在0.2和2.2 ms范围内,由此导致的定位误差分别为0.4和8 m范围内,初值迭代寻优模型能够有效解决非均匀温度场中声速不固定而导致被动定位算法时延值无法反推距离差的问题;假设声波直线传播的时延值误差及由此导致的定位误差满足工程精度要求。     

强声波在电站锅炉中传播特性的研究

对位于可听声频率范围的强声波在电站锅炉中的传播特性进行了研究.基于简单波假设理论,对声压级达到160dB的强声波传播过程中畸变和谐波生成的机理进行了分析研究,并计算了不同频率下声波的冲击波形成距离;计算得到炉内黏热流体介质中伯格斯方程的严格解,研究了发生非线性效应与耗散效应下强声波的传播特性;采用数值计算方法求解了弛豫流体介质中强声波传播的非线性波动方程,讨论了弛豫介质中声波的传播特性.结果表明:冲击波形成距离与声波频率成反比,随着声波频率的增大,非线性效应减弱,耗散效应增强.     

炉排型垃圾焚烧炉燃烧过程的数值模拟

针对城市生活垃圾焚烧发电厂运行优化的需要,采用计算流体力学的方法建立了垃圾焚烧炉燃烧过程的数值计算模型,通过联合求解质量方程、动量方程、k-ε方程、能量方程,模拟得到了炉内热解气体组分分布、炉内温度场等参数。利用该模型计算得出了炉膛温度、NO_x排放浓度随过量空气系数、生物质掺混比变化的特性曲线,并与实验结果进行了对比。结果表明：该模型能够预测炉内焚烧过程的变化趋势,且计算值与实验值吻合较好,模型误差在8%以内。     

锅炉管阵列中的声二极管效应与冷态缺陷研究

基于声子晶体理论,通过设定管阵列的几何参数和温度等环境参数,采用数值计算方法分析了声波通过2种不同结构管阵列的传播特性,得到在某些频率范围内存在声波的单向导通特性,并对冷点缺陷位于管阵列中不同位置处的声传播特性进行了计算.结果表明:声波的单向导通特性与2种管阵列过度位置的结构排布方式有关;管阵列中存在冷点缺陷时其声传播特性会发生变化;研究声波通过不同管阵列的声传播特性对管阵列中声源定位有重要意义.     

曲轴红套感应加热有限元仿真和优化

根据电磁感应和热传导理论,导出了工件感应加热的电场、磁场、温度场分布基本方程,建立了三维有限元分析模型,并考虑了工件材料属性随温度变化的非线性特性。制定了新的热加工方案,利用ANSYS分析感应加热过程曲柄的温度场分布和热变形。借助多学科优化软件iSIGHT集成ANSYS,将多目标优化算法NSGA-Ⅱ引入感应加热线圈电流、频率等参数的寻优中。最后对仿真优化得到的线圈参数进行试验验证。试验结果与仿真结果误差在4%以内,验证了有限元模型的准确性及多目标优化算法的可靠性。     

超临界锅炉水冷壁鳍片超温现象分析

为了得到某电厂受损水冷壁鳍片的失效模式及其影响因素,对其进行了金相分析并建立一个圆柱体导热模型,推导出鳍片温度场的微分方程。运用边界条件得到方程的特解,计算出该锅炉运行参数下超温处鳍片半径上限值。利用有限元模拟的方法,得到鳍片的温度场云图,并给出鳍片温度随其厚度、宽度和热流密度等因素的关系式。结合理论公式,提出相应预防措施。     

Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

Exergetic evaluation of 5 biowastes-to-biofuels routes via gasification

This paper presents the exergy analysis results for the production of several biofuels, i.e., SNG (synthetic natural gas), methanol, Fischer–Tropsch fuels, hydrogen, as well as heat and electricity, from several biowastes generated in the Dutch province of Friesland, selected as one of the typical European regions. Biowastes have been classified in 5 virtual streams according to their ultimate and proximate analysis. All production chains have been modeled in Aspen Plus in order to analyze their technical performance. The common steps for all the production chains are: pre-treatment, gasification, gas cleaning, water–gas-shift reactions, catalytic reactors, final gas separation and upgrading. Optionally a gas turbine and steam turbines are used to produce heat and electricity from unconverted gas and heat removal, respectively. The results show that, in terms of mass conversion, methanol production seems to be the most efficient process for all the biowastes. SNG synthesis is preferred when exergetic efficiency is the objective parameter, but hydrogen process is more efficient when the performance is analyzed by means of the 1st Law of Thermodynamics. The main exergy losses account for the gasification section, except in the electricity and heat production chain, where the combined cycle is less efficient.     

液压系统常见的故障诊断及处理

任何工程机械式液压设备使用时出现故障是不可避免的。但是怎样确定故障的原因及找到好的解决方法，这是使用者最关心的问题。讲述了液压系统常见的故障及其排除方法。     

Economie d'énergie en trigénération

Trigeneration is defined as the production of three useful forms of energy—heat, cold and power—from a primary source of energy such as natural gas or oil. For instance, trigeneration systems typically produce electrical power via a reciprocating engine or gas turbine and recover a large percentage of the heat energy retained in the lubricating oil, exhaust gas and coolant water systems to maximize the utilization of the primary fuel. The heat produced can be totally or partially used to fuel absorption refrigerators. Therefore, trigeneration systems enjoy an inherently high efficiency and have the potential to significantly reduce the energy-related operation costs of facilities. In this paper, we describe a model of characterization of trigeneration systems trough the condition of primary energy saving and the quality index, compared to the separate production of heat, cold and power. The study highlights the importance of the choice of the separate production reference system on the level of primary energy saving and emissions reduction.     

Mineralogical characterization of the intraseam layers of Lofoi lignite deposits in Florina basin (western Makedonia,northwest Greece)

The mineralogical composition of intraseam layers from Lofoi lignite deposits (northwest Greece) is the subject of the present study. The samples were examined by means of X-ray diffraction (XRD), thermo-gravimetric (TG/DTG) and differential thermal analysis (DTA), and Fourier transform infrared (FT-IR) spectrometry. The clay minerals prevail in most samples, with illite-muscovite being the dominant phase, and kaolinite and chlorite being the other major clay components. No smectite was found. Quartz and feldspars, dominate in two cases. The studied materials are characterized as clays to clayey sands, showing significant similarities with the intraseam layers of the adjacent Achlada lignite deposits.     

Innovative methodologies in renewable energy: A review

This paper is concerned with innovative approaches to renewable energy sources computation methodologies, which provide more refined results than the classical alternatives. Such refinements provide additional improvements especially for replacement of fossil energy usages that emit greenhouse gas (GHG) into the atmosphere leading to climate change impact. Current knowledge gap among each renewable energy source calculation is rather missing fundamentals of plausible, rational, and logical explanations for the interpretation of results. In the literature, there are rather complicated and mechanically applicable methodologies, which require input and output measurement data match with missing physical explanations. The view taken in this review paper is to concentrate on quite plausible, logical, rational, and effectively applicable innovative energy calculation methodologies with simplistic fundamentals. For this purpose, a set of renewable energy methodological approaches is revisited with their innovative structures concerning solar, wind, hydro, current, and geothermal energy resources. With the increase in the renewable energy utilizations to combat the undesirable impacts of global warming and climate change, there is a need for better models that will include physical environmental conditions and data properties in the probabilistic, statistical, stochastic, logical, and rational senses leading to refined and more reliable estimations with application examples in the text. Finally, new research directions are also recommended for more refined innovative energy system calculations.     

Constrained Optimization of Heat Transfer from an Extended Surface

Two different zero‐order optimization techniques are used to maximize the rates of heat transfer from a fin assembly of a specified cost and in the shape of several annular fins that are mounted on a central stem. The problem is formulated to account for two‐dimensional steady‐state heat transfer that is limited by several inequality constraints. The dimensionless governing equations are used to identify the relevant decision variables. The number of fins making up the assembly is treated as an input parameter. A digital computer is used to determine the required temperature distributions and to implement the optimization search algorithms. Three different fin materials are assessed—aluminum, copper and carbon steel. Design optimizations of the extended surface assembly were made over a range of operating conditions, encompassing several different convection heat transfer coefficients that are representative of free and forced convection in air, and several different overall temperature differences between the substrate surface and air. A few recommendations based on trends in the predicted results are given. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 43(6): 504–521, 2014; Published online 3 October 2013 in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21093     

CY6D78Ti型柴油机的开发研制

本文介绍了CY6D78Ti型柴油机的开发研制过程及现状,CY6D78Ti型柴油机能满足国内中、重型卡车和豪华客车市场对柴油机动力性、经济性、可靠性的需求。由于该机型的高档配置,保证了其排放达到欧Ⅱ标准,同时为进一步提高性能、降低排放,采用电控及高压共轨等技术手段搭建了平台。     

我国车用柴油机的技术现状及发展趋势

本文根据国内外信息和资料，分析了我国目前车用柴油机制造技术方面与国际水平所存在的差距，预测今后若千年内车用柴油机要向节能降耗、应用增压技术、提高可靠性、降低排放、采用电控技术方面发展，以尽快接近和赶上国际先进水平．