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Turbine stage expansion model including internal air film cooling and novel method of calculating theoretical power of a cooled stage

Trawiński Paweł

Archives of Thermodynamics

2022

Vol. 43, no 3

3--27

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.

Ocena pomiarów ruchowych turbin na podstawie obliczeniowej linii ekspansji

Chmielniak T., Łukowicz H.

Zeszyty Naukowe. Elektryka / Politechnika Opolska

2002

Vol. 280, z. 51

93-98

W referacie przedstawiono metodę korekty pomiarów ruchowych parametrów pary w turbinie na podstawie obliczeniowej linii rozprężania. Wielkości pomiarowe można wykorzystać w analizie układu cieplnego turbiny, np. do wyznaczenia sprawności i mocy wewnętrznej turbiny (jej części). W niektórych przypadkach otrzymuje się jednak błędne rezultaty. Dlatego pomiary powinny być uzupełnione obliczeniami parametrów pary w turbinie.

In the article, the correction method of pressure and temperature measurements in the turbine, on the base of expansion line calculation has been presented. The operation measurements of steam parameters (pressure, temperature and mass flow) in turbine inlet, outlet and bleeding points can be use to evaluate turbine efficiency and power (some parts of it). In some causes it is possible to obtain incorrect results. It could be caused by turbine construction as well as wrong measurement instruments indication and bad location of them. In calculations of the expansion line in the turbine stages, 1-D and 2-D models of flow have been applied. The special attention was paid to the determination of profile and boundary losses in blades.