Development of moisture loss models in steam turbines

This paper describes physics-based moisture loss models for designing wet-steam turbines. Steam turbines operating under wet-steam conditions experience thermodynamic and mechanical losses caused by the presence of moisture. The developed moisture loss models are composed of six categories: supersaturation loss, condensation loss, acceleration loss, braking loss, capturing loss, and pumping loss. These losses are calculated according to the wetness levels in the stationary blade and moving blade rows, and defined by the functions of steam properties and design factors of turbine stages. The supersaturation loss produced by non-equilibrium expansion of the wet steam is modeled using the pressure ratio and the isentropic exponent of the supersaturated steam. The loss models are compared to full-size test turbine data for prediction of the overall moisture losses. As a result, the developed loss models are found to be very effective for estimating the moisture losses of turbine stages. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 42(7): 651–664, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.20395