<font face="Verdana">ABSTRACT: Steam turbine low pressure (LP) cylinder design<br/>aims at reducing the wetness loss. It requires knowledge of<br/>steam droplet diameter distribution in the flow tunnel, which<br/>tightly relates to the condensation process. However, currently<br/>available models of condensation theory and the experiment<br/>results obtained from the steam nozzle can not be directly<br/>applied to assessment of the real steam turbine condensation.<br/>This paper briefly introduced the nucleation mechanism of wet<br/>steam in LP cylinders of steam turbines and the working<br/>principle of the newly developed wet steam measuring<br/>instrument. The correlation of steam wetness parameters with<br/>the back pressure was analyzed based on actual measurement<br/>of steam wetness parameters behind the last stage of the<br/>direct-cooling LP unit and the condensation mechanism. The<br/>existence of heterogeneous condensation and the transition of<br/>dominating condensation from heterogeneous to homogeneous<br/>over the back-pressure change were demonstrated by the actual<br/>measurement results.<br/>KEY WORDS: turbine; wet steam; heterogeneous<br/>condensation; homogeneous condensation; measurement<br/>摘要:为减少湿蒸汽损失,汽轮机低压缸设计中需要知道湿<br/>蒸汽的水滴参数。水滴参数与凝结过程紧密相连,但目前已<br/>有的凝结理论模型和实验室中的喷嘴实验结果不能直接应<br/>用于真实的汽轮机中。简单介绍了汽轮机低压缸内湿蒸汽<br/>的凝结机制和新研制的改进型湿蒸汽测量系统的工作原理。<br/>基于实测变背压过程中直接空冷机组低压汽轮机末级后的<br/>蒸汽湿度参数并结合凝结机制,分析变背压过程中蒸汽湿度<br/>参数的变化规律及原因,证实了汽轮机中存在异质凝结现象<br/>以及凝结从异质为主向均质为主转变的过程。<br/>关键词:汽轮机;湿蒸汽;异质凝结;均质凝结;测量</font>
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