An investigation of wet steam flow in a 300 MW direct air-cooling steam turbine. Part 3: heterogeneous/homogeneous condensation

摘要

Steam condensation in steam turbines is a complex problem and its process is still not clear. To investigate the condensation process in the steam turbine, measurements were carried out with an optical/pneumatic probe in a 300 MW direct air-cooling steam turbine by changing the backpressure from 42 to 24 kPa. The thermodynamic states of the exhaust steam were changed from superheat to wet steam too. The existence of heterogeneous condensation was demonstrated by the actual measurement results. The process of condensation in the steam turbine was found to be from heterogeneous condensation, to heterogeneous/homogeneous condensation and then to homogeneous condensation. The mean diameter of droplets formed by both condensations is completely different. During the transition stage from heterogeneous condensation to homogeneous condensation, all parameters have huge oscillation. Flow parameters of steam are strongly related to the condensation.