Effect of Nonlinear Characteristic of the Gas Turbine Engine Fuel System With Hardware-in-the-Loop

Abstract

Fuel supply system, the regulation system for fuel delivery to the combustor, is one of the most important auxiliary systems in a gas turbine engine. Commonly, the fuel supply system was always simplified as a linear system. In fact, gas turbine engines almost use a hydromechanical main fuel control system which consists of electro-hydraulic servo actuator and fuel metering unit. These components have several nonlinear characteristics such as hysteresis, dead zone, relay, and saturator. These nonlinear characteristics can directly affect the performance a gas turbine engine. In this paper, a three-shaft gas turbine engine was taken as a research object. Firstly, a mechanism model of the fuel control system considering the nonlinear links was developed based on the hydro-mechanical theory. Then, the effect of dead zone-relay characteristic of the servo amplifier in electro-hydraulic servo actuator was analyzed. The results show that the dead zone width has great effect on the dynamic performance of the gas turbine engine. The fuel flow rate will be oscillating with small dead zone width. The parameters of the gas turbine engine will be stable with the increase of dead zone width. However, the larger dead zone width causes the hysteresis and the increase of the dynamic response time. At the same time, an improvement method with a two-dimensional fuzzy compensation was proposed. The results show that the fuzzy compensation can effectively solve the oscillation problem caused by the dead zone-delay. Finally, a Hardware-In-the-Loop (HIL) system is developed which is based on an electro-hydraulic servo actuator facility and a real-time software component of the gas turbine engine. An experiment is conducted on the HIL test rig to validate simulation result. The results show that the experiment matches well with the simulation results.