偏转二次风对炉内结渣影响的研究

结合 1 2 5MW、660MW锅炉燃烧器偏转二次风系统的设计特点 ,结合数值模拟计算及炉内试验调整改造 ,说明偏转二次风对炉内结渣的影响 ,研究结果建议偏转二次风的角度应控制在 1 5°以内     

600 MW偏转二次风系统锅炉炉内结渣特性的数值模拟

偏转二次风系统已广泛应用于大型四角切圆燃烧锅炉，用以报制炉内结渣，防止水冷壁高温腐蚀等。为降低炉膛出口扭转残余，通常采和下部二次风大角度正切、上部二次风和OFA风反切的布置方式。本文对某台采用偏转二次风系统的600MW燃煤四角切圆燃烧锅炉的炉内结渣过程进行模拟，对炉内气固相流动、温度场、气固相燃烧、固相向水冷的输运过程和灰粒在水冷壁上的附生长过程进行了数值模拟，结果表明，偏转二次风系统具有较强的防结渣性能，这一点也被锅炉的实际运行所证实。     

600MW锅炉偏转二次风系统降低NOx排放的试验研究

某600MW机组四角切圆燃烧锅炉,采用顶部燃尽风并配合使用偏转二次风系统,炉膛下部二次风大角度正切,上部二次风和OFA风反切肖旋,在炉膛截面水平方向和炉膛高度方向形成分级燃烧.实际运行结果表明,该燃烧器布置方式能抑制炉内结渣,减轻炉膛出口旋转残余并能降低NOx排放量.通过对该600MW机组锅炉进行多工况试验,摸索该炉的NOx排放特性,并在试验中采用燃烧调整方法降低NOx排放,获得了良好的效果,将锅炉的氮氧化物排放水平降低到国家标准限定值以下,为采用偏转二次风系统的大型电站锅炉降低NOx排放提供参考.     

空气分级与偏转二次风联用对炉膛燃烧特性的影响

运用CFD软件对某210 MW煤粉锅炉的燃烧过程进行三维数值模拟,采用空气分级燃烧技术,研究不同空气分级深度及偏转二次风对锅炉的燃烧情况及NOx排放的影响,同时引入"敏感性指数",分析了不同空气分级深度下联用偏转二次风前后对锅炉运行的影响程度。结果表明:单独采用空气分级和偏转二次风均能降低NOx排放,二者联用时空气分级起主导作用,NOx排放降低25%~28%;在不同空气分级深度下联用偏二次风措施对炉内燃烧前后影响程度不同,温度场与组分场出现较为相同的影响规律,在一定燃尽风率区间,存在对应(温度、组分)敏感性系数最大的燃尽风率,敏感性指数随燃尽风率的增加呈先增加后减小的变化趋势,即影响程度先增强后减弱;联用偏转二次风改善炉内结渣和高温腐蚀的效果随燃尽风率先增强后减弱,燃尽风率在18%~25%时效果较好,但导致飞灰含碳率显著增加。     

300MW电站锅炉燃烧调整数值模拟研究

对300MW电站锅炉进行了燃烧调整的数值模拟,通过改变二次风配风方式,研究炉膛内火焰温度、氧浓度的变化,进而分析炉膛内结渣特性,为锅炉燃烧调整提供理论指导。     

燃用准东煤电站锅炉炉膛温度场分布及结渣特性试验研究

在掺烧准东煤电站锅炉试验中,通过改变SOFA风率和准东煤掺烧比,研究了SOFA风率和掺烧比对膛内火焰温度场分布及炉膛内结渣情况的影响。结果表明,一次燃烧区域火焰平均峰值温度随SOFA风率的增加而降低,而二次燃烧区域火焰平均峰值温度炉膛和烟气出口温度随SOFA风率的增加而升高。随着准东煤掺烧比增大,主燃烧区域温度升高,而在燃尽风区域火焰平均峰值温度则降低。SOFA风率最大时燃烧器中部区域结渣情况最为严重,而随着SOFA风率的减小,燃尽风上方区域的结渣情况越来越严重。随着掺烧比的增大,燃烧器中部区域和燃尽风上方区域的结渣情况均变得严重。里层渣样出现钠钙长石和赤铁矿的富集,随着结渣的发展,渣样中碱金属含量逐渐降低。     

塔式锅炉偏转二次风对NO_x排放影响的数值模拟

针对电站锅炉在运行过程中存在的NO_x排放浓度过高的现象,文中利用Fluent软件对某台1 000 MW塔式锅炉的燃烧过程进行数值模拟,并研究了不同偏转二次风角度对锅炉NO_x排放的影响。研究结果表明:以对角线45°为基准,偏转二次风偏转角度在30°以内时,炉膛内均能形成良好切圆;增大偏转二次风偏转角度,炉膛中心四周NO_x质量浓度明显下降;随着炉膛高度增加,NO_x质量浓度逐渐减少,偏置风偏转角度30°工况与偏转角度10°工况相比较,炉膛出口处的NO_x质量浓度下降了10.3%。     

210MW煤粉炉燃烧系统改进的数值模拟

运用CFD软件对某210 MW煤粉锅炉的燃烧过程进行三维数值模拟,针对锅炉实际存在温度分布不好、燃烧效率不高、结渣问题严重,对炉膛进行偏二次风、反切燃尽风及两者联用改进。结果表明:与设计工况相比,单独的小角度偏二次风改进下的炉膛燃烧区温度降低约300 K,水冷壁附近氧气浓度提高,减少了水冷壁的结渣和高温腐蚀;单独小风率反切燃尽风改造后的配风方式更合理,烟气的停留时间增加0.6 s,燃烧区温度提高约373 K,高温区域扩大,炉膛出口烟气热偏差系数减小约0.7%,提高了锅炉的燃烧效率和运行的安全性,但可能加重炉内结渣;二者联用改进既能够很好地改善炉膛的温度分布,扩大炉膛高温区域,提高燃烧区温度约353 K,同时能够减少燃烧器区域的结渣和高温腐蚀,减小炉膛出口烟气热偏差,采用二者联用改造对锅炉运行最为合适。     

某600MW超临界锅炉结渣原因分析及解决方法

某600MW超临界锅炉运行期间结渣现象频繁,冷态试验发现三次风气流在调节范围内贴壁严重,电厂对旋流燃烧器结构进行了改造,增加了三次风外侧扩锥,使三次风气流贴壁现象彻底消除,调节三次风门可以改变三次风的旋流强度,煤粉燃烧状况得以改善,进而避免了锅炉结渣现象,提高了机组运行的安全性。     

1000MW塔式锅炉燃烧结渣定量评价的数值研究

以某1 000MW塔式锅炉为研究对象,模拟了炉内煤粉燃烧过程,获得了炉内速度场和温度场,梳理汇总了包含碰撞壁面的颗粒质量、壁面结渣概率和结渣增长率等参数的结渣评价模型,基于炉内的燃烧数值模拟结果,给出了炉内煤粉颗粒燃烧后碰撞壁面的质量、壁面结渣概率和结渣增长率,对塔式锅炉进行了较为细致的结渣评价。结果表明:该塔式锅炉结渣概率较大区域主要分布在燃烧器区域及其下游和分离燃尽风(SOFA)的下游区域;壁面的结渣增长率在10-12 m/s的量级范围;相比于额定工况,该塔式锅炉70%负荷工况下可能结渣的区域缩小,结渣增长率也降低。     

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．