Publications Repository - Gdańsk University of Technology

Almost entire fleet of steam turbines in Poland was designed between 1950 – 1980 with the use of the so-called zero dimensional (0D) calculation tools. For several years, design and modernization of the turbines occur in assistance with the state of the art methods that describe working fluid flow field based on 3D models and CFD codes. This cooperation between 0D and 3D codes requires exchange of overall, integral information such as: power, efficiency, heat and mass fluxes. In consequence the question arises regarding the cohesion of definitions, and particularly regarding the correctness of the definition for internal efficiency of the turbine’s stage and the turbine as a whole. In the present paper we formulate basic definitions of efficiency that are naturally adapted to the numerical 0D and 3D models. We show that the main reason of differences between the definitions in 0D and 3D is the definition of the theoretical (ideal) work of the stage. In the classical 0D models, mostly employed is the isentropic approach, and hence the isentropic efficiency occurs . Meanwhile, in the increasingly common 3D approach (most likely by CFD), we use more physically correct pathway by subtracting energy loss from the available energy, that leads to the polytropic definition of efficiency. We show an example of computing the efficiency and the 3D losses, denoted with additional subscript: CFD, and we also discuss benefits of this definition in comparison with the isentropic classical definition in 0D.

Authors

• Lucjan Nastałek link open in new tab ,
• Michał Karcz,
• Daniel Sławiński link open in new tab ,
• Witold Zakrzewski link open in new tab ,
• Paweł Ziółkowski,
• Czesław Szyrejko,
• Jacek Topolski,
• Janusz Badur,
• Robert Werner