Development of a Micro-Turbojet Engine Control Unit for Component Level Efficiencies Monitoring

This paper presents the design and analysis of an additive manufactured fuel manifold integrated into a 22 lbf thrust micro-turbojet. The motivation for this study to attain reliable operation and improved maintainability in attritable micro turbojets for small, high-speed unmanned aircraft. A combustor rig was developed for experiments utilizing a JetCat P100 RX. Aft of the engine, static and total pressure were measured to calculate the mass flow rate. Downstream of the diffuser, total pressure was measured to calculate pressure loss across the combustor. Internal thermocouples were used to map the profile factor across in the combustor. An analytical study was done to determine the optimal number and inner diameter of the fuel line for reliability. Ansys Fluent was used for a numerical flow study to evaluate candidate design. The final design of the fuel manifold was 6 fuel lines that have an inner diameter of .05 in. and 6 y-shaped vaporization tubes. The fuel manifold was integrated in the combustion chamber liner to reach the necessary temperature for fuel vaporization in the vaporization tubes. This resulted in 240 F fuel exiting the fuel manifold at the maximum flow rate condition. The pressure ratio across the burner, combustion loading parameter, and fuel preheat were measured and compared against those of a stock JetCat P100 RX. Observations from this study lead to a new fuel manifold design approach that has improved start reliability and reduced flame-out for small, high-speed unmanned aircraft.