膨胀剂对超高性能混凝土抗裂性能的影响研究

超高性能混凝土(UHPC)因其优异的力学和耐久性能,具有广泛的应用前景。但是,UHPC存在收缩大、开裂风险高的问题。为了改善UHPC的抗裂性能,利用内掺MgO和HCSA膨胀剂,研究膨胀剂对UHPC力学性能、收缩、水化热和抗裂性的影响,利用微观测试研究膨胀剂的作用机理,采用不同指标对UHPC的抗裂性进行了评价。结果表明,膨胀剂会小幅度降低UHPC的强度和弹性模量,但具有良好的补偿收缩作用。抗裂性评价指标和平板开裂试验结果表明,膨胀剂可以提高UHPC的抗裂性能。     

模袋混凝土抗裂性能影响因素分析与评价

为分析模袋混凝土抗裂性能的影响因素,采用极限拉伸试验,以极限拉伸值和轴向抗拉强度作为混凝土抗裂能力的评价指标,研究等强度条件下粉煤灰掺量、含气量及粗骨料体积分数对其抗裂性能的影响规律。通过对比试验,探讨模袋布对混凝土抗裂性能的影响。结果表明,等强度条件下,粉煤灰掺量增加,混凝土的轴向抗拉强度和极限拉伸值提高;混凝土的轴向抗拉强度和极限拉伸值与含气量之间呈"中间高,两边低"的变化规律;混凝土的轴向抗拉强度和极限拉伸值与粗骨料体积分数呈单调递减趋势。模袋混凝土试件破坏时,其轴向抗拉强度和极限拉伸的峰值大约为素混凝土的1.1、1.3倍;模袋混凝土的极限变形能力提高,模袋布显著改善了混凝土的综合抗裂性能。研究成果可为模袋混凝土抗裂性能的理论完善提供试验数据和理论依据。     

粗粉分离器性能评价指标分析

给出了评价粗粉分离器性能的主要参数指标,指出存在最佳循环倍率使得粗粉分离器效率最高;分析了煤粉细度对锅炉燃烧的重要影响,指出对煤粉细度的调节性能是评价粗粉分离器的重要指标;分析了煤粉颗粒均匀性指数以及粗粉分离器内部通风阻力作为评价粗粉分离器性能指标的重要性。     

不同配合比参数对沥青混凝土低温抗裂性能的影响

依托易县抽水蓄能电站上水库沥青混凝土面板配合比设计,通过对沥青混凝土进行低温冻断试验,研究了在沥青混凝土面板防渗层配合比设计时使用不同厂家生产的沥青、不同填料含量、不同油石比及不同天然砂掺加比例对水工沥青混凝土低温抗裂性能的影响规律。结果表明,不同厂家生产的沥青对沥青混凝土低温抗裂性能影响不同且差别很大;不同填料含量对沥青混凝土冻断温度影响显著;不同油石比对沥青混凝土冻断应力影响显著;天然砂的掺加比例会影响沥青混凝土的低温抗裂性能。结果可为沥青混凝土面板防渗层配合比参数选择提供参考。     

冻融循环与硫酸盐侵蚀耦合作用下碾压混凝土性能研究

为研究冻融循环与硫酸盐侵蚀耦合作用下碾压混凝土层面的性能,设计并开展了碾压混凝土层面性能的相关试验,通过测试碾压混凝土质量变化、相对动弹性模量、硫酸根离子侵蚀浓度变化及层面损伤层厚度,分析了碾压混凝土在冻融与Na₂SO₄溶液耦合作用下的损伤机理。试验结果表明,水胶比对碾压混凝土层面各项性能影响显著,碾压混凝土水胶比越小,其水泥水化程度越高,骨料间的浆体粘结性能也越高,相应各项层面性能的抗侵蚀抗冻耐久性越好;当冻融循环次数达到75~100次后,双因素耦合作用下的试件各层面评价指标劣化速率增快,层面损伤程度开始逐步高于单一冻融破坏。     

纳米级掺合料粗合成纤维湿喷混凝土施工及抗裂性能分析

为考察纳米级掺合料粗合成纤维湿喷混凝土的施工及抗裂性能,开展了凝结时间、回弹率、抗压强度、干缩、平板开裂和温度应力试验,并将其与同配制强度的硅粉钢纤维湿喷混凝土进行比较。结果表明,与硅粉钢纤维湿喷混凝土相比,纳米级掺合料粗合成纤维湿喷混凝土的凝结时间变化不大;回弹率下降了27%;1d抗压强度提高了45%;干缩测值接近,平板总开裂面积降低,温度应力开裂时间延长,开裂敏感性降低。     

纳米级掺合料粗合成纤维湿喷混凝土施工及抗裂性能分析

为考察纳米级掺合料粗合成纤维湿喷混凝土的施工及抗裂性能,开展了凝结时间、回弹率、抗压强度、干缩、平板开裂和温度应力试验,并将其与同配制强度的硅粉钢纤维湿喷混凝土进行比较。结果表明,与硅粉钢纤维湿喷混凝土相比,纳米级掺合料粗合成纤维湿喷混凝土的凝结时间变化不大;回弹率下降了27%;1 d抗压强度提高了45%;干缩测值接近,平板总开裂面积降低,温度应力开裂时间延长,开裂敏感性降低。     

乌东德大坝低热水泥混凝土温控防裂效果研究

鉴于目前国内高混凝土坝尚无全坝应用低热水泥的先例,结合混凝土性能特点,研究了乌东德大坝中热、低热水泥混凝土的温度控制标准、最高温度控制措施及大坝抗裂安全系数,并采用有限单元法仿真计算了典型坝段施工期温度场和温度应力场。结果表明,大坝在采用低热水泥混凝土后,最高温度明显降低,富裕度增大,同时抗裂安全系数可提高至2.0以上。结果为乌东德拱坝全面采用低热水泥混凝土提供了参考依据。     

基于正交试验的水泥—乳化沥青混合料配合比设计

针对水泥—乳化沥青混合料的配合比设计问题,采用正交试验设计方法修正了马歇尔试验研究,引入极差分析法分析了沥青用量、级配、水泥用量和用水量4个典型因素对混合料马歇尔试验指标的影响,并辅以无侧限抗压强度试验,考虑经济性,提出了水泥—乳化沥青混合料的优化配合比.研究结果表明,对优化的AC-13矿料级配,沥青用量3.6％、水泥用量3％、用水量5.5％的水泥—乳化沥青混合料在路用性能上较普通乳化沥青混合料有显著改善,接近于热拌沥青混合料的性能,是一种经济性和路用性能良好的筑路材料.     

纳米粒子和PVA纤维增强水泥基复合材料抗碳化性能研究

为研究纳米粒子掺量和种类、PVA纤维掺量对水泥基复合材料抗碳化性能的影响,通过碳化试验测得各组水泥基复合材料碳化试件的碳化深度。纳米粒子的质量掺量分别为0.5%、1.0%、1.5%、2.0%、2.5%,纳米粒子种类为纳米SiO_2和纳米CaCO_3,PVA纤维的体积掺量分别为0.3%、0.6%、0.9%、1.2%。研究结果表明,纳米SiO_2可以显著提高PVA纤维增强水泥基复合材料抗碳化性能,且在纳米SiO_2掺量低于2.5%时,抗碳化性能随着纳米SiO_2掺量的增加不断增强;PVA纤维可明显提高纳米水泥基复合材料的抗碳化性能,当纤维体积掺量不大于1.2%时,纤维体积掺量较大的纳米水泥基复合材料具有较高的抗碳化性能;纳米CaCO_3与纳米SiO_2均能提高水泥基复合材料的抗碳化性能,纳米SiO_2的提高效果略优于纳米CaCO_3。研究结果为纳米粒子和PVA纤维在水泥基复合材料中的应用提供指导。     

基于D_S证据理论的煤粉细度融合诊断

针对电厂煤粉细度在线测量难的问题,提出利用数据融合技术识别煤粉过细、煤粉正常、煤粉过粗。在分析与煤粉细度相关的多个运行状态参量基础上,根据历史运行数据,确定煤粉细度的典型样本,然后对各状态参量应用D—S融合规则得到结果。而对于D—S证据理论应用中基本概率赋值难以确定问题,应用正态分布曲线构造相似度函数．继而得到基本概率赋值,减少了方法的主观性。根据运行数据验证,该方法能够有效诊断煤粉细度,且具有较好的鲁棒性,具有工程实用价值。     

Turkey’s short-term gross annual electricity demand forecast by fuzzy logic approach

This paper aims to forecast Turkey's short-term gross annual electricity demand by applying fuzzy logic methodology while general information on economical, political and electricity market conditions of the country is also given. Unlike most of the other forecast models about Turkey's electricity demand, which usually uses more than one parameter, gross domestic product (GDP) based on purchasing power parity was the only parameter used in the model. Proposed model made good predictions and captured the system dynamic behavior covering the years of 1970–2014. The model yielded average absolute relative errors of 3.9%. Furthermore, the model estimates a 4.5% decrease in electricity demand of Turkey in 2009 and the electricity demand growth rates are projected to be about 4% between 2010 and 2014. It is concluded that forecasting the Turkey's short-term gross electricity demand with the country's economic performance will provide more reliable projections. Forecasting the annual electricity consumption of a country could be made by any designer with the help of the fuzzy logic procedure described in this paper. The advantage of this model lies on the ability to mimic the human thinking and reasoning.     

国产引进型300MW“W”型锅炉煤粉分离器改造

为了解决某电厂2#锅炉自投产以来存在的煤粉偏粗、飞灰可燃物含量偏高等问题,从改善入炉煤粉细度,获取细煤粉（R90≤5％）入手,对原双蜗壳心型煤粉分离器进行技术改造,采用旋转式动静结合型分离器,配合燃烧调整手段,改造后锅炉效率提高1.28％,供电煤耗降低4.532g/kW·h.证明对于燃用低挥发分劣质无烟煤的“W”型锅炉,通过采用旋转式煤粉分离器,可以有效改善煤粉细度,降低飞灰和灰渣可燃物含量,有利于锅炉燃烧稳定性和经济性的提高.     

碾压混凝土渗透及溶蚀耐久性机理的简述

对碾压混凝土的溶蚀和渗透耐久性进行了化学、宏观、微观等方面的阐述,揭示了碾压混凝土的溶蚀机理,简述了碾压混凝土临界水力梯度及渗透、溶蚀耐久性的关系。为直接使用碾压混凝土作为大坝防渗体、减少防渗层厚度、进一步降低内部碾压混凝土的水泥用量和大量掺用粉煤灰提供了理论依据     

Implementation of coal development programs and the future role of indonesia as a potential coal supplier in the southwest Pacific region

The 1973 oil crisis and the increased domestic oil consumption during the 1970s made Indonesia aware of the vulnerability of its petroleum-based economy. Since oil—a limited energy resource—had formed the main source of foreign exchange earnings for decades, a policy of diversification of energy away from oil was imperative in order to meet the increasing energy demand in the country, while saving the valuable commodity for export purposes. An ambitious program to develop other energy resources, in particular coal, started with the rehabilitation and expansion of the two state-owned coal-mines in Sumatra. The coal produced was expected to fuel the newly built coal-fired power plants and the expanding cement industry.Aware of the limited available funds, the Government of Indonesia invited foreign investors to participate in the development of the nation's coal potential, especially in Kalimantan. The exploration efforts of these contractors resulted in the identification of vast reserves of coal that, when fully developed, would have been sufficient to meet the expected domestic coal demand. However, because of the world-wide recession and the sharp drop in oil revenue, ambitious construction programs in the power sector and the cement industry had to be restrained and coal consumption projections dropped substantially.In view of the vast coal potential identified, which in general is amenable to inexpensive openpit mining, and the large number of contractors involved in the development projects, it is anticipated that production capacity toward the end of the 1980s will far exceed domestic demand. Since the other ASEAN member countries and the northern industrialized Asian countries will be potential net importers of coal and in view of Indonesia's favorable geographic location, there is reason to believe that excess Indonesian coal can be allocated to the aforementioned export markets.     

Impacts of temporal precision in optimisation modelling of micro-Combined Heat and Power

When modelling the environmental and economic aspects of meeting a given heat and power demand with a combination of combined heat and power (CHP) and grid power, it is common to use a coarse temporal precision such as 1-h demand blocks in heat and power demand data. This may be appropriate for larger applications where demand is reasonably smooth, but becomes questionable for applications where demand exhibits substantial volatility such as for a single residential dwelling—an important potential market for the commercialisation of small-scale fuel cells and other micro-CHP. Choice of temporal precision is also influenced by the relative ease in obtaining coarse data, their compatibility with available energy price data, and avoidance of computational overheads when data sets expand. The thesis of this paper is that use of such coarse temporal precision leads to averaging effects that result in misleading environmental and economic outcomes for cost-optimal micro-CHP systems. Much finer temporal precision is required to capture adequately the specific characteristics of residential energy demand and the technical qualities of solid oxide fuel cell and stirling engine micro-CHP systems. This thesis is generally supported by the results of analysis, which shows that in some cases optimal design generation capacity of the CHP system is reduced by more than half between analyses using 1-h precision and 5-min precision energy demand data. When optimal dispatch of given generator and boiler capacities is considered, the quantities of energy delivered by the various components of the energy provision system (i.e. generation from CHP, heat from CHP, heat from an additional boiler, electricity from grid) varied by up to 40% between precisions analysed. Total CO₂ emissions reduction is overestimated by up to 40% by the analyses completed using coarse demand data for a given micro-CHP generator capacity. The economic difference is also significant at up to 8% of lifetime costs for a given micro-CHP generator capacity.     

制粉系统的性能调整试验

介绍了某电站锅炉配套制粉系统的性能调整试验,其中包括粗粉分离器挡板特性、磨辊加载压力调整试验和磨煤机出力特性等性能试验。分析了制粉系统运行的经济性,提出的优化运行参数可以大幅度地提高制粉系统出力,降低制粉系统单耗,而且煤粉细度达到设计要求,有利于煤粉的燃烬。     

负荷对电站锅炉运行参数影响特性分析及应达值的确定

运行参数对锅炉经济性的影响普遍采用偏差分析法进行分析,对锅炉各种运行参数的应达值而言其性质是不同的,在确定了应达值的基础上才能分析运行参数的偏差对锅炉经济性的影响。在分析了锅炉运行参数的静态特性后,对各类锅炉运行参数进行了分类,并分析了各类应达值的确定方法,为分析和提高电厂运行经济性提供了依据。