直接空冷凝汽器加装扩压导流叶栅的性能分析

发布时间：2019-04-30 09:40

【摘要】：直接空冷系统经过近些年的发展,技术日趋成熟,目前正处于广泛应用的阶段。直接空冷系统采用环境空气作为介质冷却汽轮机乏汽,空冷凝汽器作为直接空冷系统的核心设备,其可靠的冷却性能是电厂稳定、经济运行的关键。由于空冷单元布置于自然环境流场中,其换热性能受环境风的影响较大。本文以某电厂600MW直接空冷机组单列空冷单元为例,针对直接空冷凝汽器换热性能受环境风影响大的问题,在直接空冷平台的边缘加装扩压导流叶栅。设计了8种不同叶型的扩压导流叶栅,利用Fluent软件,建立加装扩压导流叶栅后单列空冷单元的数值模型,模拟计算得到了各空冷单元的换热情况,分析了加装扩压导流叶栅对直接空冷凝汽器换热性能的改善作用。同时研究了叶片导流角度、叶片个数以及叶栅安装位置对直接空冷凝汽器换热性能的影响。结果表明,加装扩压导流叶栅能有效地改善环境风工况下空冷单元的流场,消除空冷单元内及风机入口处的涡旋,并且能够降低各轴流风机入口处冷却空气的平均温度,其中,越靠近迎风面的空冷单元改善效果越明显。其次,加装扩压导流叶栅提升了空冷凝汽器整体的换热性能;当环境风速较高时,优化效果显著;在8m/s的环境风速下,加装扩压导流叶栅后空冷单元整体换热效率提高了8%。对比结果显示,在所选的八种叶型中,NACA6412叶片所组成的叶栅对空冷凝汽器性能的提升最为显著。在此基础上对扩压导流叶栅的结构参数进行优化,得到最佳的叶片导流角度为45°;且叶片个数越多提升效果越明显;在空冷单元中间再加装一列叶栅,凝汽器整体换热性能够得到进一步的提升。
[Abstract]:With the development of direct air-cooling system in recent years, the technology of direct air-cooling system is becoming more and more mature and it is in the stage of extensive application. Direct air-cooling system uses ambient air as medium to cool steam turbine exhaust steam, air-cooled condenser as the core equipment of direct air-cooling system, and its reliable cooling performance is the key to stable and economical operation of power plant. Because the air cooling unit is arranged in the natural environmental flow field, the heat transfer performance of the unit is greatly affected by the environmental wind. Taking a single row air-cooling unit of 600MW direct air-cooling unit in a power plant as an example, in order to solve the problem that the heat transfer performance of direct air-cooled condenser is greatly affected by environmental wind, the expansion pressure guide cascade is installed on the edge of the direct air-cooling platform. Eight kinds of diffuser cascade were designed. The numerical model of single-row air-cooling element was established by using Fluent software, and the heat transfer of each air-cooling unit was obtained by simulation calculation, and the heat transfer of each air-cooling unit was obtained by using the numerical model of single-row air-cooling unit after adding the diffuser cascade. The improvement of heat transfer performance of direct air-cooled condenser with expanded pressure guide cascades is analyzed in this paper. At the same time, the influence of blade diversion angle, blade number and cascade installation position on the heat transfer performance of direct air-cooled condenser is studied. The results show that the installation of diffuser cascade can effectively improve the flow field of the air cooling unit under the ambient wind condition, eliminate the vortex in the air cooling unit and the inlet of the fan, and reduce the average temperature of the cooling air at the inlet of each axial flow fan, among which, the flow field of the air cooling unit in the air cooling unit and the inlet of the fan can be eliminated. The more close to the upwind surface, the more obvious the improvement effect of the air-cooling unit is. Secondly, the whole heat transfer performance of the air-cooled condenser is improved by adding the diffuser cascade, and the optimization effect is remarkable when the ambient wind speed is high. Under the ambient wind speed of 8m/s, the overall heat transfer efficiency of the air-cooled unit after installing the diffuser cascade is increased by 8%. The results show that the cascade composed of NACA6412 blades has the most significant improvement on the performance of air-cooled condenser among the eight selected blade profiles. On this basis, the structural parameters of the diffuser cascade are optimized, and the optimal blade diversion angle is 45 掳, and the more the blade number, the more obvious the improvement effect is. By adding a series of cascades to the air-cooled unit, the overall heat transfer of the condenser can be further improved.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM621

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