Design and Simulation of a Control System for a Single Spool Mixed-Flow Small Turbofan Engine

Small turbofan engines have received a lot of attention in recent years. These engines are usually made from the development of small turbojet engines and usually their core includes a microjet engine. The turbine's power in these engines is transferred directly or through a gearbox to the fan of the new engine. By adding the bypass duct to the microjet engine, a lot of thrust is created by the air passing through the bypass. In this paper, the design and simulation of a control system for a small single-spool mixed-flow turbofan engine is conducted. A thermodynamic model is considered to simulate the engine's behavior and a control structure is extracted to meet the engine's control requirements. Considering that in such engines, only the engine spool speed and exhaust gas temperature are measured by the sensors, using these two variables and the throttle degree, the designed algorithm fulfills the amount of requested thrust and the limitations governing the engine spool speed, turbine temperature, lean combustor blow-out, and the compressor surge margin. The presented method can also be applied to control a single spool unmixed-flow geared-turbofan engine. The results of a comprehensive simulation by changing the throttle degree between 25% to 100% show the effective performance of the controller in fulfillment of the thrust command and limit protection.