Performance and Mission Profile Analysis of a Water-Injected Micro Turbojet Engine

With the recent increase in the strategic use of unmanned aerial vehicle (UAV), micro gas turbine (MGT) has received renewed attention as compact, high-power density propulsion systems for UAV. From an operational perspective, thrust augmentation is a crucial performance parameter for the UAV mission, and water injection is a relatively simple and less complex technique capable of providing instantaneous thrust augmentation. This study analyzes the changes in engine performance when water is injected at either the compressor inlet or the combustor inlet of a 100 N-class micro turbojet engine. Furthermore, by integrating the engine simulation model with a flight mission profile, the study examines how water injection-induced thrust augmentation affects the operational performance of the UAV during an entire mission profile. The simulation reveals that water injection produced a maximum thrust increase of up to 24.3 %. Even after accounting for the mass p enalty of the water p ayload and the injection system, flight performances such as mean climb angle, mean climb rate, and thrust-to-weight ratio were enhanced during the whole mission profile due to a thrust augmentation. These results indicate that water injection is a practical means of augmenting thrust in a micro turbojet engine and contributes to improved UAV mission capability through enhanced flight performance.