Multivariable Modelling of Gas Turbine Dynamics

Abstract

The linear multivariable modelling of an aircraft gas turbine is presented. A frequency-domain identification method is employed to estimate a family of models from engine data at a range of operating points. It is found that the fuel feed to shaft speed dynamics can be represented by second-order models. This matches the results obtained for the reduced-order linearised thermodynamic models derived from the engine physics. A direct comparison can thus be made between the estimated and thermodynamic models, which shows significant discrepancies between them for the engine tested. This work illustrates how modern system identification techniques can be used to verify engine models. The multivariable framework employed means that additional inputs and outputs can be easily incorporated into the model.

Engineering Creative Design in Robotics and Mechatronics

“…Evans et al presented the linear multivariable model of a twin-shaft aero gas turbine (a typical Rolls Royce Spey military turbofan) using a frequency-domain identification technique (Evans et al, 2001). The technique was employed to estimate s-domain multivariable models directly from test data.…”

“…The techniques investigated in the research can be used to verify the linearized thermodynamic models of gas turbines. Figure 10 shows the Rolls Royce Spey engine modelled by Evans et al (2001).…”

“…Figure 11 shows a Figure 10. A typical Rolls Royce Spey engine (Evans, et al, 2001) simple structure of a typical ANN with two inputs, one output and five neurons in the hidden layer (Wikimedia Commons, 2012).…”

Global Nonlinear Modelling of Gas Turbine Dynamics Using NARMAX Structures

“…This provides an accurate representation of the system, incorporating the pure time delay in the model, and a physical interpretation can be made of the model poles and zeros. This work has been recently extended to the multivariable case [13], where frequency-techniques were used to estimate linear state-space models.…”

Static and Dynamic Mathematical Modeling of a Micro Gas Turbine

“…With regard to existing powerful tools to verify the linear model, linear analysis is chosen to simulate the MGT in transient conditions. This is possible by linearization of thermodynamic equations around an operating point to obtain a simplified model that is more appropriate for control system design [21,25], and since there is not any integration of dynamic variable, the simulation procedure need very little computer time [24]. In section 4, the thermodynamic transient equations for each component are presented, linearized, and their state-space form is derived.…”