This study clarifies the heat transfer characteristics of flow boiling in a narrow vertical rectangular channel at each stage and optimizes the performance of a heat exchanger. The flow pattern and local heat transfer characteristics in a narrow vertical rectangular channel of steam heating with dimensions of 1400 x 250 x 2.75 mm (l x w x s) were experimentally investigated using deionized water as the working medium. Based on the visualization data, the mechanical model and empirical formulas in previous literature, a preliminary derivation of the flow pattern transition criterion for steam heating in a vertical rectangular narrow channel was obtained. The effects of the inlet temperature, mass flux, and heating power on the local heat transfer characteristics were analyzed in conjunction with the flow patterns. Based on the parametric analysis of the experimental data, a new flow boiling heat transfer correlation formula was obtained and applied to the experimental conditions. The results showed that an increase in the inlet temperature had a positive effect on the nucleate boiling section, whereas the effect on the local heat transfer coefficient was minimal after entering the churn flow phases. The increase in mass flux decreased the local heat transfer coefficient in the nuclear state boiling stage and enhanced the local heat transfer coefficient in the evaporation zone of the liquid film flow. The peak of the local heat transfer coefficient tended to shift to the left as the heating power increased. The proposed heat transfer correlation equation could well predict the local heat transfer coefficient of flow boiling in a vertical rectangular narrow channel heated by steam under these experimental conditions.
With its large scale and high flexibility, liquefied air energy storage is very suitable for integrated operation with existing power generation systems to improve the regulation ability of the grid. A novel liquified air energy storage system coupled with coal-fired power unit for heat exchange through the water/steam and the compression/expansion air is proposed. The thermodynamic model of a novel liquified air energy storage system is established with a 307 MW coal-fired power unit as the coupling object. And the parameters design and performance analysis of the coupling system are carried out. The results show that the efficiency of the system can reach 51.64 %. At this time, the corresponding energy storage/release pressure is 18/7.2 MPa. The highest return on investment of the system can reach 19.59 %, and the shortest dynamic payback period can reach 4.73 years. The sensitivity analysis shows that decreasing the heat transfer end difference of the regenerator and increasing the adiabatic efficiency of the compressor are conducive to reducing the exergosy destruction of equipment and improving the efficiency of the system. It is beneficial to improve the economic performance of the system to increase the difference between peak and valley electricity prices and the amount of peak regulation subsidy.
In order to analyze the internal combustion mechanism of the biomass circulating fluidized bed boiler and realize the optimization of combustion control, the combustion process and combustion mechanism in the furnace were analyzed through the analysis of the characteristics of biomass fuel and the application of the instantaneous carbon combustion theory, and the combustion process was established. The dynamic change process of carbon burning in the furnace was analyzed to realized the prediction of load, furnace temperature, carbon monoxide emission and flue gas oxygen content. Results show that the combustion rate of instant carbon formed after the fuel devolatilization is slower than that of volatile matter, and the fuel feeding fluctuation directly affects the instant carbon stock in the furnace. As the main source of heat when the feed fluctuates, the oxygen required for instant carbon combustion is less and the combustion is more sufficient. At the same time, the CO valume fraction in the flue gas is lower and the oxygen content is higher. the predicted values of furnace temperature, furnace load, CO valume fraction and flue gas oxygen content are basically the same as the actual values.
利用数值模拟方法研究了循环流化床(CFB)锅炉一次风风量偏差对流化均匀性的影响规律,提出了布风均匀性的料层厚度偏差判据,进而提出了循环流化床锅炉布风均匀性改进的试验方法.结果表明:一次风室两侧进口风量偏差超过10％时,床料流化均匀性较差,此时对应布风均匀性的最大许可偏差,即最高、最低床料高度差不宜超过20 cm,床料高度与平均高度最大偏差不超过 12 cm.
To study the economic feasibility of coordinated frequency regulation for a system combined energy storage battery with gas turbine, an operation strategy was proposed, in which the gas turbine was responsible for low frequency component of frequency demand signal, while the energy storage battery compensated for its power output, and the state of the battery charge was considered. A dynamic model of heavy-duty gas turbine was established based on Matlab/Simulink platform, and an economic evaluation model for the system was constructed. Under a period of actual frequency regulation demand signal, the total system costs of single energy storage system and combined system of energy storage and gas turbine were compared when they achieve the same frequency regulation performance. Results show that the energy storage battery capacity required for frequency regulation of combined system is reduced, which leads to a decrease in the system total costs. The combined system thus becomes a more economically competitive frequency regulation resource.
为了研究热电联供系统中机组的热电负荷优化分配策略,针对传统灰狼优化算法中繁琐的更新机制导致的时效性差等问题,提出了一种改进的多 目标灰狼优化(MOGGWO)算法,直接利用前三等级狼的位置和高斯采样完成进化过程,最后将该算法应用于某600 MW双机热电联供系统的多 目标热电负荷优化分配中.结果表明:MOGGWO算法能极大缩短负荷分配的求解时间,且在多 目标优化下提升系统经济性的同时其可再生能源消纳能力将会减弱,应根据现场实际情况权衡,进而选择热电负荷最优分配策略.
针对传统故障诊断方法抗噪性能差,对振动信号中的故障信息挖掘不充分的问题,提出了一种基于变分模态分解(VMD)与改进的稠密连接网络(DenseNet)相结合的滚动轴承故障诊断模型.首先利用VMD将含有噪声的振动信号分解为多个本征模态分量,选取与原始信号相关性较大的若干分量并重构,得到降噪后的信号.然后将重构信号送入DenseNet网络中提取特征,并通过增加通道注意力机制对提取的不同特征赋予不同的权重,进一步强化特征的区分度.最后,通过Softmax层完成故障分类.结果表明:该模型对含有不同强度噪声的振动信号均能有效提取故障特征,具有良好的诊断性能.
基于汽轮机变工况原理,提出了一种在线计算汽轮机排汽焓的新方法——多变指数法.通过考虑低压缸进汽流量、进汽温度、进汽压力和排汽压力对做功能力的影响,建立了低压缸做功多变指数模型,并采用多变指数法得出针对单个机组热力特性的精确模型以及适用于不同机组的改进通用模型.结果表明:由精确模型得到的排汽焓计算值与设计值的平均相对误差为0.165％,最大相对误差为0.738％;由改进通用模型得到的排汽焓计算值与设计值的平均相对误差为0.93％,最大相对误差为3.52％,可满足工程计算精度要求.
对比了 0号高压加热器、省煤器给水旁路和省煤器烟气旁路等宽负荷脱硝系统的宽负荷性能及瞬态特性.结果表明:在30％THA～100％THA负荷、旁路流量均为50％时,采用低过侧省煤器烟气旁路的SCR入口温度升高幅度最大,达31.2 K;采用各省煤器旁路方案均使机组标准煤耗率增大,采用低过侧省煤器烟气旁路和低再侧省煤器烟气旁路时,标准煤耗率每增大1 g/(kW· h),可分别提高SCR入口温度42.16 K和27.56 K;采用低过侧省煤器烟气旁路时,SCR入口温度变化滞后时间短且变化率高(达到34.65 K/min);投运0号高加后SCR入口温度变化滞后约1 min,功率平均变化率为10.22 MW/min.
为探究环境条件的时空分布差异性对太阳能直膨式光伏光热(PVT)热泵系统运行性能的影响,进行数学建模与性能仿真,分析了系统在不同地区采暖季内的运行性能.结果表明:由于入射太阳辐射的效应,在不同地区,系统的采暖季平均蒸发温度都提高至接近甚至超过环境温度的水平,显著改善了系统的热力性能;当冷凝温度为50 ℃时,系统在北京、拉萨、兰州的采暖季平均COP分别为3.67、5.01和3.41;采暖季平均单板得热功率分别为541 W、810 W和504 W,得热因子分别为71.7％、62.0％和79.3％,光伏发电增益分别为4.76％、8.67％和6.10％.
针对西北地区可再生能源大规模分配、运输和储存等问题,设计了一种面向高比例可再生能源消纳的光储氢醇一体化系统.首先,在保证降低弃光率的同时,以系统全年总收益最大化为目标构建了光储氢醇的数学模型并通过McCormick法进行线性化处理;其次,以全年数据为基础分析并确定了系统最佳设备容量与运行调度;最后,分析了甲醇价格、售氧价格、购碳价格以及设备成本对总收益的影响.结果表明:经过联合设计调度优化,新型光储氢醇一体化系统可在不增加电网压力的前提下,大幅消纳可再生能源并保持甲醇稳定生产,同时系统具备初步经济效益;而随着甲醇价格的提升和设备成本的降低,系统经济收益可进一步提升.
基于扇形孔的实验数据,提出了一种预测气膜冷却效率的新关联式.综合考虑孔形参数和孔内外流动条件对气膜冷却效率的影响,构建关联式特征系数的代理模型.结果表明:通过实验设计(DOE)获得的优化孔与采用特征系数代理模型获得的优化孔的气膜冷却效率和最优孔形参数基本一致;应用新关联式加速气膜孔形的多置信度优化或优化多气膜孔阵列的具体布局具有显著的工程应用价值.
以某660 MW机组回转式空气预热器为研究对象,采用弯扭合成当量弯矩方法对回转式空气预热器主轴截面进行应力计算和强度校核.结果表明:相较于其他工况,在BMCR工况下回转式空气预热器主轴所受的倾覆力矩达到最大,产生的弯曲应力在合成应力中占比52％,是影响主轴弯曲变形的重要因素;相较于不考虑倾覆力矩影响的情况,考虑倾覆力矩后主轴强度的安全裕度降低了 40％.
以某300 MW火力发电机组的大型湿式冷却塔为研究对象,建立填料非均匀布置耦合分区配水的三维数值模型.填料内外区分别布置30 mm和26 mm S波填料,改变配水分区半径R1,重新分配配水内外区配水占比,研究不同工况下填料非均匀布置耦合分区配水对冷却塔热力性能的影响.结果表明:填料非均匀布置耦合分区配水可显著降低塔心区的高温,提高气水比.设计工况下,随着填料分区半径R2和内区配水占比P的增大,冷却数和体积传热系数均先增大后减小.当R1=15～35 m时降低P,而当R1=40 m时增大P,均可提高湿式冷却塔整体热力性能.此时相对最佳的耦合布置方案为R1=25 m、R2=25 m和P=35％,与原始塔相比,冷却数和体积传热系数分别增大0.09和17.0 W/(m3·K).
采用COMSOL软件构建了全三维全陶瓷微封装(FCM)燃料元件模型,提出了一种FCM燃料元件内TRISO颗粒随机分布的高效建模方法,可以实现较高填充率的颗粒弥散填充.分析了不同颗粒填充率(35％、40％和45％)下以及不同颗粒随机分布下FCM燃料元件的温度分布特性.结果表明:FCM燃料元件中心区域温度高,沿径向温度降低;TRISO燃料颗粒特别是燃料核芯的温度明显高于周围基体的温度,温差可达130 K甚至更高,其中最大的温度梯度出现在Buffer层;在相同线功率下,随着颗粒填充率的增加,燃料芯块的最高温度降低,平均温度略有升高;受到颗粒分布随机性的影响,当颗粒填充率减小时,平均温度和最高温度分布的离散程度均增加,但总体上颗粒随机分布对燃料芯块平均温度的影响较小.
针对水轮机空化声发射(AE)信号非线性强,导致水轮机空化状态识别准确度不高的问题,建立基于混沌理论和卷积神经网络结合优化支持向量机(CNN-OSVM)的水轮机空化状态识别方法.对不同空化状态下的水轮机空化AE信号进行相空间重构,获得相图作为数据集,通过卷积神经网络提取不同空化状态下的相图特征,输入经网格搜索算法结合K折交叉验证算法全局参数寻优的优化支持向量机分类器完成空化状态识别.结果表明:输入混沌相图数据集的CNN-OSVM模型能够准确识别4种空化状态,平均准确率高达98.8％;同时证实相较于CNN模型、OSVM模型,CNN-OSVM模型对非线性信号分类具有更高的识别准确率和泛化性.
针对堆芯功率的非线性控制问题,提出了一种自耦PID(SCPID)功率控制方法.该方法将系统内部所有已知或未知复杂因素及外部扰动定义为一个总扰动,建立了以总扰动为激励的受控误差系统,进而设计了基于SCPID控制理论的堆芯功率控制系统,并在复频域对闭环控制系统的稳定性进行严格的数学分析和证明.结果表明:与其他方法相比,SCPID控制方法简单高效,在堆芯功率系统控制领域具有实际应用价值.
为研究漂浮式海上双转子风力机的动态响应特性,采用OC3-Hywind Spar漂浮式平台,搭建了漂浮式海上双转子风力机仿真系统.采用自由涡尾迹法(Free Vortex Wake,FVW)和OpenFAST水动力计算模块,建立了漂浮式海上双转子风力机的气动-水动耦合分析模型,并进行了风浪耦合分析与控制仿真.结果表明:主副转子功率波动幅值随风浪夹角变大而逐渐减小;主副转子间流场比陆上双转子风力机更加复杂,多 目标变桨控制既可减小功率波动又可缓解副转子的疲劳损伤;风浪夹角在0°和90°的工况下,平台运动响应波动较为明显.
为了对燃气轮机透平轮盘的概率疲劳寿命和可靠性分析展开充分研究,针对透平轮盘材料13Cr10MoW1VNbN开展了低周疲劳试验并进行结果分析及误差优化,基于Manson-Coffin公式及材料试验数据,建立了应变-寿命预测模型.分别采用蒙特卡洛法与包络线法,获得轮盘疲劳寿命数据样本,开展了统计分析及可靠性研究.结果表明:基于蒙特卡洛法得到的可靠度曲线比基于包络线法得到的可靠度曲线下降趋势更平缓,考虑的不确定因素更多,安全裕度更大.
对基于超临界二氧化碳工质的热泵储电系统展开研究,建立了热力学与技术经济性分析模型,并对系统热力参数进行优化,分析了压缩机等熵效率、透平等熵效率、换热器压损以及最小换热温差等关键设备参数对系统性能的影响.此外,提出了以燃气轮机排气为外热源的集成系统构型,对独立热泵储电系统及集成外热源的系统性能进行分析.结果表明:独立储能系统的最高往返效率可达62.91％;集成外热源后,单位能量的投资成本降低,系统能量效率随放电时间和放电功率的增加而降低.
