Droplet deposition in steam turbines

Abstract

Research since the 1960s on the deposition of droplets from wet steam is reviewed, concentrating mainly on low-pressure turbines but also covering the limited work related to nuclear high-pressure turbines. The context is first set, outlining the motivation in terms of blade erosion and, to a lesser extent, wetness losses. Details of measurements in turbines and in simulated turbine flows are followed by descriptions of theoretical work on the main inertial and turbulent deposition mechanisms; possible additional contributory mechanisms are summarized. A major combined experimental and computational effort in the 1980s led to broad agreement between measured and calculated fog deposition fractions in low-pressure turbine final stages, attributed largely to the development of more accurate droplet size measurement and computational fluid dynamics techniques. An attempt has been made to correlate advances with the history of steam turbine development and to speculate on the future of deposition studies in the light of recent theoretical developments and trends in power generation.