Entropy generation and exergy destruction in condensing steam flow through turbine blade with surface roughness. (15th September 2019)

• Record Type: Journal Article
• Authors: Ding, Hongbing; Li, Yiming; Lakzian, Esmail; Wen, Chuang; Wang, Chao
• Is Part Of: Energy conversion and management. Volume 196(2019)
• Page Start: 1089
• Page End: 1104
• Publication Date: 2019-09-15
• Subjects: Steam turbine -- Non-equilibrium condensation -- Entropy generation -- Exergy destruction -- Transition SST model -- Surface roughness; Direct energy conversion -- Periodicals; Energy storage -- Periodicals; Energy transfer -- Periodicals; Énergie -- Conversion directe -- Périodiques; Direct energy conversion; Periodicals; 621.3105
• DOI: 10.1016/j.enconman.2019.06.066
• Languages: English
• ISSNs: 0196-8904

Abstract

Highlights: Entropy generation and exergy of condensing flow in turbine blade with roughness. Non-equilibrium condensation model and entropy transport equation. Transition SST model with roughness correlation to capture viscous boundary layer. Entropy generations due to viscous, heat, phase change and aerodynamic losses. The performance loss coefficient and exergy destruction ratio. Abstract: In the steam turbine, the wetness loss due to vapor condensation is one of the most crucial losses at low-pressure stage. This study focused on entropy generation and exergy destruction of condensing steam flow in turbine blade with the roughness. The governing equations including entropy transport equation combined with condensation model, transition SST model and roughness correlation were established and verified by experiments and theory. Flow field behaviors, such as wetness fraction, intermittency and turbulent viscosity distributions, controlled by the deviation angle were obtained to evaluate effects of back pressure ratio and surface roughness. The mass-averaged wetness fraction at outlet was also extracted considering the influence of uneven mass flux. Finally, each part of entropy generation derived from viscous, heat conduction, phase change and aerodynamic losses and exergy destruction ratio were analyzed. Research shows that roughness plays an important part in the intermittency and turbulent viscosity. The mass-averaged wetness fraction at outlet sharply drops with back pressure ratio but slightly decreases with the roughness. With the roughness rising or back pressure dropping, the entropy generation grows resulting in more exergy destruction. The maximum value of the total entropy generation is 84.520 J·kg −1 ·K −1, corresponding exergy destruction is 25.187 kJ·kg −1 and exergy destruction ratio is 4.43%.