Design, implementation, and testing of a digital control system for a small gas turbine engine

Digital control systems have increasingly replaced the once ubiquitous hydromechanical control system in gas turbine engines. Digital systems offer many advantages over hydromechanical controls including the ability to Implement complex control laws, potential for built-in diagnostics, and greatly improved flexibility.; In this study, a digital control system was designed for an Allied Signal GTCP 85-97, a small, single spool gas turbine with fixed geometry. The design objective was to duplicate the performance of the engine's hydromechanical control system and provide a platform for future control system research.; Fuel schedules for the control system were determined experimentally by measuring the fuel flow to the engine during start up and in other modes of operation. A new fuel metering system comprising a metering valve and a bypass valve, to maintain a constant pressure drop across the metering valve, was designed. Stepper motors were selected as actuators for both valves.; Approximate linear models were generated for the fuel metering system and the engine. Two distinct control systems, one to position each fuel valve, were synthesized using the root locus method and frequency response techniques. The control systems were implemented using LabVIEW software on a notebook computer. The software, fuel system hardware, and necessary instrumentation were integrated into a functioning system and the system was tested on a test bench followed by on-engine testing.; Although the system performance was hampered by slow actuator response and instrumentation signal noise, the gas turbine was successfully started and run using the digital control system. The system displayed very good potential and demonstrated greatly improved flexibility over the mechanical system.