DETERMINING REFERENCE VALUES OF LQI OUTPUT VARIABLES FOR A SMALL SCALE TURBOJET WITH VARIABLE EXHAUST NOZZLE

Abstract

Aero-engines are complex, non-linear systems from the perspective of engine control, thus designing engine control that is efficient throughout the operating envelope is also a complex task. Current aero-engine control researches, whose objective is to cover the operating range of the engine are mentioned to receive an insight from the engine control development trends. The aim of this work is to initiate the design process of a gain scheduling linear quadratic integral (LQI) control of a single spool variable exhaust nozzle small scale turbojet engine by applying an algorithm, that converts the thrust lever angle positions into rotor speed and engine pressure ratio reference values for the controller, while the thrust force of the engine changes linearly with the thrust lever angle position. This work presents the measurement that provides the dataset for the algorithm, and uses the linearized state space model of the turbojet to determine the variables for which the reference values must be obtained. Then the calculation process for the determination of reference points based on the measurement data is detailed. Finally, the results of the applied process for the investigated small scale turbojet engine are indicated.