1100t_h塔式炉水冷壁热负荷及变形趋势的数值模拟

通过自行编制的数值模拟软件,对蒲城发电厂1号炉进行了热态空气动力场和燃烧过程的数值模拟,并通过水冷壁热负荷分布的情况来讨论水冷壁开裂趋势的问题.数值模拟的结果表明:燃烧器喷口射流旋向向上时,炉膛火焰中心偏高,且炉膛出口的温度偏差较大;燃烧器喷口射流旋向向下时,炉膛火焰中心位于炉膛下部,炉膛温度的均匀性较好;炉膛四面炉墙的热负荷差异很大,水冷壁的4个角落热膨胀不均匀,而导致较大的开裂趋势.在将燃烧器喷口射流旋向调整为向下以后,墙面之间的热负荷偏差减小,水冷壁开裂的可能性减小;每面炉墙自身的热负荷偏差也很大,若水动力工况不佳时,也可导致炉墙水冷壁变形.     

1000MW塔式直流锅炉炉膛水冷壁管壁温度和热负荷分布的试验研究

对2台1 000MW超超临界压力塔式直流锅炉炉膛水冷壁管壁温度和热负荷分布进行了测量和计算,并对不同负荷工况、不同磨煤机投运方式下的热负荷和管壁温度分布规律以及炉膛上部垂直水冷壁的热负荷分布进行了分析.结果表明:1 000MW塔式直流锅炉炉膛热负荷的分布规律与其他四角切圆燃烧锅炉炉膛热负荷的分布规律基本一致.由于在最上层的燃烧器上方布置了燃尽风,对炉内烟气的扰动加强,导致沿管长方向的热负荷在54m标高处波动较大;在燃尽风喷嘴中心线以上,因受到燃尽风进入炉膛的影响,水冷壁热负荷大幅度下降.为了避免炉膛大比热区传热恶化,可以将处于拟临界点附近的水冷壁布置在低热负荷区域.     

1000吨/时燃油直流锅炉炉膛热负荷分布的测定

望亭发电厂12号炉系燃油直流锅炉,其燃烧器为前后墙平行错列布置方式,水冷壁采用一次上升、中间二次混合的管圈型式。炉膛热负荷分布情况是分析和研究水冷壁水动力特性、传热特性以及炉内燃烧过程的重要基础。经多次测定,在20～28万瓩负荷下,沿炉膛高度方向热负荷分布不均匀系数K_(qy)=1.50～1.60,沿炉膛深度方向热负荷分布不均匀系数K_(qx)=1.12～1.15,最高局部热负荷q_(max)=300～330×10~3(大卡/米~2时)。     

负荷变化对900 MW超临界锅炉炉内燃烧影响的数值模拟

利用Fluent软件对1台900 MW四角切圆燃烧锅炉在不同负荷下炉内燃烧过程进行了数值模拟,分析了负荷变化对炉内流动和传热的影响规律.结果表明:在高负荷工况下运行时,炉内燃烧充分且稳定,但是炉内火焰更容易冲刷水冷壁,可能发生局部结渣现象;在低负荷工况下运行时,炉内火焰充满度较差,切圆燃烧的稳定性显著下降,炉膛水冷壁灰污表面温度也相应降低,水冷壁表面结渣的倾向弱化,沿高度方向水冷壁吸热不均匀性增大.由于该锅炉的低NOx燃烧器采用了分离燃尽风,使得高温区扩展,火焰中心高度比采用有关标准推荐的方法计算所得结果高4~5 m.     

超超临界直流锅炉垂直管屏水冷壁壁温分布特性

以燃用高钠煤的660MW超超临界压力直流锅炉为例,对不同工况下垂直管屏水冷壁壁温分布特性进行了试验研究.结果表明:提高高钠煤的掺烧比例,可降低燃烧区域热负荷,有利于水冷壁壁温分布的均匀性;超临界压力下低负荷运行时,水冷壁壁温偏差值会增大,节流孔圈未完全发挥控制工质质量流量的作用是造成水冷壁壁温偏差较大的原因之一;通过调整锅炉运行方式,可在一定程度上改善水冷壁壁温分布的均匀性.     

1000MW超超临界锅炉水冷壁壁温计算

采用分区计算简化大容量高参数超超临界锅炉炉内辐射、对流传热模型,研究炉膛水冷壁热负荷及壁温的空间分布情况,并与试验数据进行了对比,计算结果与试验值之间的偏差较小,最大为5.72%.该模型与算法可给出不同锅炉负荷条件下,水冷壁壁面热负荷与壁温沿炉膛宽度方向的分布规律.结果表明,水冷壁热负荷与壁温均呈现出中间高两端低的弧形分布.四角切圆燃烧锅炉火焰位置对炉内传热有很大影响.模拟计算可为超超临界锅炉的运行提供参考,预测了在材料允许温度范围内,火焰中心偏斜最大不超过2 m.     

超临界压力W火焰锅炉运行方式对炉内热负荷影响的试验研究

对某600 MW超临界压力W火焰锅炉炉膛水冷壁壁温进行了测量,获得了炉膛水冷壁热负荷分布,调整锅炉运行方式(如磨煤机投运方式、前后墙的总风门挡板开度、煤粉细度和三次风风门挡板开度等),测量并计算炉内热负荷.结果表明:煤粉细度对炉内热负荷几乎没有影响;前后墙总风门挡板开度会影响炉内火焰行程,应该采用"前墙压后墙"的运行方式;三次风风门挡板开度变化会改变上、下炉膛热负荷的分布;不投运的磨煤机所对应区域的热负荷明显下降.     

700℃超超临界锅炉壁温特性研究

采用分区简化一维电站锅炉炉内气动一传热模型,理论计算了700℃超超临界锅炉炉膛水冷壁及管内工质温度的空间分布特性。计算结果表明:沿炉膛高度方向上煤粉燃烧器区域水冷壁热负荷较高,炉膛中间热负荷高,而上下炉膛的热负荷偏低;水冷壁周向温度呈中间高两侧低的抛物线型分布,700℃、35 MPa超超临界状态下,锅炉在BMCR工况下的水冷壁管内工质为单相流体,无明显大比热区域,壁温最大高达到619℃。因此,在5%左右的设计裕度下,建议水冷壁管材应选用许用温度大于650℃的材料。     

超临界直流锅炉水冷壁广义全工况能量分析

传统的机组全工况分析是基于机组稳定运行状态的分析,由于非稳态工况的出现日益频繁,提出了同时包括稳态和非稳态工况的广义全工况的概念,给出了其相应的热力学第一定律评价指标——热利用率和热储率。在此基础上,采用水冷壁分段的计算方法,建立了超临界直流锅炉水冷壁广义全工况热力学第一定律分析模型。以某1 913t/h锅炉水冷壁为例进行了计算,获得了水冷壁广义全工况的热量组成和分布结果。结果表明:对于本例中的多种升负荷的非稳态过程,水冷壁的热储率约为0.9%~4.1%;亚临界压力下的蒸发段和热水段蓄热约占水冷壁总蓄热的95.8%~98.2%,而超临界压力时不存在蒸发段,其余各段的蓄热所占比例基本相当;当负荷固定时随负荷变化率的增大,热储率增大,热利用率降低,当负荷变化率固定时,热储率随负荷的增大而减小,热利用率升高。     

600MW超临界循环流化床锅炉水冷壁热应力分析

为研究超临界循环流化床锅炉水冷壁的变形问题,在实炉测量某600 MW超临界循环流化床锅炉炉膛水冷壁壁温分布的基础上,采用数值模拟方法对距离布风板30m高度处4.6m×2m区域的水冷壁管进行了热应力分析。结果表明:80%负荷工况下,距离布风板30m高度处区域的水冷壁管沿炉膛高度方向的温度变化率较大,热应力分布极不均匀;计算区域的水冷壁管整体向下膨胀,由于存在膨胀偏差,水冷壁向火侧向炉内凸起变形,最大变形量约1.14mm;对于整个水冷壁管屏而言,存在的变形量叠加会加剧水冷壁磨损,甚至造成爆管事故。     

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．