TY - JOUR N2 - Systematic attempts to maximise the efficiency of gas turbine units are achieved, among other possibilities, by increasing the temperature at the inlet to the expansion section. This requires additional technological solutions in advanced systems for cooling the blade rows with air extracted from the compressor section. This paper introduces a new mathematical model describing the expansion process of the working medium in the turbine stage with air film cooling. The model includes temperature and pressure losses caused by the mixing of cooling air in the path of hot exhaust gases. The improvement of the accuracy of the expansion process mathematical description, compared with the currently used models, is achieved by introducing an additional empirical coefficient estimating the distribution of the cooling air along the profile of the turbine blade. The new approach to determine the theoretical power of a cooled turbine stage is also presented. The model is based on the application of three conservation laws: mass, energy and momentum. The advantage of the proposed approach is the inclusion of variable thermodynamic parameters of the cooling medium. The results were compared with the simplified models used in the literature: separate Hartsel expansion, mainstream pressure, weighted-average pressure and fully reversible. The proposed model for expansion and the determination of theoretical power allows for accurate modelling of the performance of a cooled turbine stage under varying conditions. L1 - http://journals.pan.pl/Content/124792/PDF/art01_int.pdf L2 - http://journals.pan.pl/Content/124792 PY - 2022 IS - No 3 EP - 27 DO - 10.24425/ather.2022.143169 KW - Gas turbine KW - Expansion line KW - Air film cooling KW - Theoretical stage power A1 - Trawiński, Paweł PB - The Committee of Thermodynamics and Combustion of the Polish Academy of Sciences and The Institute of Fluid-Flow Machinery Polish Academy of Sciences VL - vol. 43 DA - 2022.10.20 T1 - Turbine stage expansion model including internal air film cooling and novel method of calculating theoretical power of a cooled stage SP - 3 UR - http://journals.pan.pl/dlibra/publication/edition/124792 T2 - Archives of Thermodynamics ER -