Micro turbojet engine nozzle ejector impact on the performance and transient regimes analysis

This study investigates the influence of an ejector nozzle on the performance and transient behavior of a micro turbojet engine. The problem addressed is the improvement of thrust and fuel efficiency in micro propulsion systems and offering new insights into engine stability during startup, rapid acceleration, and deceleration. The methodology involved experimental testing of a JetCat P80 micro engine equipped with and without an ejector, under two ambient temperatures (11 °C and 22 °C). Parameters such as thrust, fuel flow, airflow rate, compressor pressure ratio, and combustion chamber temperature were measured, enabling the evaluation of both efficiency and stability. The use of the ejector resulted in an improvement, with an increase in thrust for the three operating regimes of the microturbine engine. Specifically, an increase of approximately 2.5% was observed for regimes 1 and 2, and approximately 6.1% for regime 3 when the ambient temperature was 11 °C. When the ambient temperature was 22 °C, the thrust increase was slightly higher, demonstrating the positive contribution of the ejector in all operating regimes, particularly in the maximum regime. Additionally, it was observed that the specific fuel consumption decreased by approximately 2.5% in the first two regimes and by approximately 5.5% in regime 3. The reduction in specific fuel consumption was slightly smaller when the ambient temperature was higher. Overall, the study confirms that ejectors can significantly improve the performance of micro turbojet engines, particularly in high-load regimes, and provides experimental evidence that complements and extends previous literature.