Abstract

This work introduces two new lost cost, electronically controlled fuel metering systems for small gas turbine engines, particularly applicable in remotely piloted vehicles. The first one incorporates a diaphragm operated flat-seat bypass valve to maintain a constant differential pressure across the metering valve, which is actuated by a digital linear actuator. In the second one, both the metering and the bypass valves are controlled by two independently operated digital linear actuators. The mathematical models for the first fuel metering system, were created and used for computer simulation. Next, after preparing the experimental test set-up, the manufactured prototype was tested and the models for both the steady state and the dynamic response were validated. Three design optimization criteria, fuel flow linearity, low sensitivity to the design parameters changes and fast dynamic response were examined to improve the performance of the proposed fuel metering system. Finally, a multi-objective optimization technique was developed and implemented to obtain the best design parameters of the system. For the second fuel metering system, first the mathematical models for both the steady state and dynamic response were developed. Next, due to the flexibility offered by this system, different control strategies for controlling the digital linear actuators during the normal operation mode of the actuators and also during the back-up operation modes were introduced and investigated. Finally, to investigate the impact of different control strategies on the dynamic response of the engine, a dynamic model for the engine was also developed and used. At the end, four available fuel metering systems, including the two new ones, were compared regarding their deviation from the fuel flow linearity, dynamic response and the cost.