Analytical and experimental researches on the characteristics of a three-shaft gas turbine are presented in the paper. The concerned gas turbine engine includes a twin-shaft gas generator and a third shaft — the free turbine for power generation. The free turbine uses a variable-angle nozzle (VAN) for fuel saving and load-adjusting flexible.
The engine performance is calculated by using the multi-dimensional Newton-Raphson method, which is based on a set of matching constraints described by the error matrix and the performance maps of the related components. It has a better accuracy and stability than those of some other methods (e.g. parameter cycle method) and is well suitable for solving the off-design problem. The suggested prediction method, presented as a computer program written in Fortran 95, is extremely flexible and can be employed to various engine configurations.
Experiments are carried out on the concerned engine by controlling the stagger angle of the VAN, then adjusting the fuel consumption for different outputs. The accuracy of the prediction method is validated by the experiment.
Detailed performance characteristic of the engine is investigated under five different stagger angles of the VAN when the T3 value was controlled from 85% to 105% of its design value, revealing how the T3 and the stagger angle of the VAN affect the gas turbine performance. The results are useful for the engine operation and components optimization.
Performance prediction method of the modern gas turbine is an important tool for the engine design and performance analysis. This paper integrates a hybrid cooling model to the previous research of gas turbine performance prediction method which is applied to predict the multi-shaft gas turbine performance. The cooling model, combined with the semi-empirical model and analytical model, had been originally proposed for the investigation of turbine convective cooling or film cooling performance. The aim of the work is to apply the hybrid model to effectively estimate the coolant requirement in the gas turbine performance prediction, therefore to improve the reliability of the analysis in the innovative gas turbine cycle.
The analysis involved a three-shaft gas turbine. Experiments were carried out on the engine, and the effectiveness of the prediction method is validated by the experiment. Consequently detailed performance characteristic of the engine is investigated under different stagger angles of the variable-angle nozzle, revealing how the stagger angle of the variable-angle nozzle and the turbine inlet temperature affect the gas turbine performance. The analysis is considered valuable for the engine operation and components optimization.
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