直接空冷汽轮机末级蒸汽异质／均质成核凝结过程的在线测量

On-line Measuring of Steam Condensation Process with Heterogeneous/Homogeneous Nucleation in the Last Stage of Direct Air-Cooled Steam Turbine

采用新研制的改进型联合探针测量了某300 MW直接空冷机组低压汽轮机末级后部分区域变背压过程中的汽流参数,包括马赫数、攻角、偏转角、静压、流速和蒸汽湿度及水滴尺寸等参数.结果表明:空冷低压汽轮机末级在较高背压时并不处于湿蒸汽状态,随背压降低先出现异质成核凝结,而后才出现均质自发成核凝结.2种凝结状态之间存在着2种凝结机理共存的阶段,在此阶段凝结会出现很大波动.异质成核凝结产生的水滴尺寸大于均质自发成核凝结的水滴.

The steam flow parameters in rear zone of the last stage of a 300MW direct air-cooled steam turbine＇s LP cylinder, including Mach number, pitch angle, yaw angle, static pressure, velocity, wetness and droplet size, were measured by a newly developed and improved combined probe during the process of variable back-pressure. The results show that the exhausted steam under higher backpressure is not wet steam. With the reduction of the backpressure, heterogeneous condensation occurred firstly, then, homogeneous nucleation spontaneous condensation appeared. Between these two states there was a state that two kinds of condensation occurred together. During this period the wetness fluctuated greatly and the size of droplets formed by heterogeneous condensation was much bigger than that by homogeneous nucleation spontaneous condensation.