Testing and modeling gas turbines using multisine signals and frequency-domain techniques

The frequency-domain identification of gas turbine dynamics is discussed. Models are directly estimated from engine data and used to validate linearized thermodynamic models derived from the engine physics. This work is motivated by the problems previously encountered when using time-domain methods. A brief overview of frequency-domain techniques is presented and the design of appropriate multisine test signals is discussed. Practical results are presented for the modelling of the fuel feed to shaft speed dynamics of a twin-spool engine. The gathered data are analyzed and the frequency response functions of the engine are estimated. The identification of parametric s-domain models is discussed in detail and a comparison made between the identified models and the linearized thermodynamic models. The influence of engine nonlinearities on the linear models is also examined.