Dynamic modelling of recuperative gas turbines

Abstract

This paper describes the mathematical model and the computational procedure adopted for the development of a modularly structured computer code able to simulate the dynamic behaviour of recuperative gas turbine power plants. For accurate simulation of the turbine components, the model includes a stage-by-stage procedure for the air-cooled turbine based on the blade geometry and the characteristics of the cooling system. The counter-flow surface heat exchanger, assumed as recuperator, is described by a set of partial differential equations, giving à One-dimensional description of the temperature for air, hot gas and metal. A single-shaft recuperated cycle gas turbine, provided with compressor variable inlet guide vanes, is analysed. The transient cases caused by a step variation in the fuel flow and compressor guide vanes geometry are simulated and a linearized model is obtained, in order to identify the dynamic behaviour of the gas turbine and to design a multivariable controller. Finally, the transient case of a controlled turbine after a sudden variation in the electric load is simulated.