Constantinidis, Adonis , GONZALEZ ALMENARA, RAFAEL, Glos, Stefan , Sanchez, David
No
Appl. Therm. Eng.
Review
Científica
1
1
01/02/2026
001644039700001
The windage effect in steam turbines operating under low-load conditions is a critical phenomenon that can lead to excessive heating, reduced efficiency, and compromised mechanical integrity. This study aims to review the state of the art of the low load windage effect and to develop a physical understanding of the phenomenon, given the increasing relevance of supercritical CO2 turbine technology, particularly due to its potential to provide operational flexibility in the electricity grid in a clean, efficient, and compact manner. The paper begins with a review of the physical fundamentals and classifications of windage losses in turbomachinery, including losses in labyrinth seals, rotor-stator cavities, and shaft-casing gaps. Special attention is given to the low-load regime, discussing its triggering mechanisms, development, and consequences as reported in the literature. Key design parameters influencing windage losses are studied, such as shape of the vane passages, blade height, pitch-to-chord ratio, number of guide and rotor blades, tip clearance, flow coefficient, exhaust size and axial length between rotor and stator blades. A comparative case study is then presented, involving the design, low load simulations and analytical analyses of HP steam and sCO2 turbines in a non-reheat cycle configuration. The results indicate that the HP steam turbine exhibits a better performance, while the sCO2 turbine shows greater overheating and ventilation power, even reaching negative power output under very low load conditions. Moreover, a thermodynamic analysis based on heat transfer coefficients is complemented with an engineering oriented evaluation to estimate the thermal load distribution across turbine components. Supercritical CO2 turbine presents a similar or equal to 21 times higher heat transfer coefficient than steam's, and a larger convective capacity of two orders of magnitude difference, where blades show up as the most critical component. These findings highlight the importance of further research into the windage behaviour of sCO2 turbines, particularly as this technology advances towards commercial application.
Windage effect; Low-load operation; Flexibility; Ventilation losses; Axial turbines