Coupled Propulsion-Aerodynamics Analysis of a Turbojet-Powered Small-Scale Supersonic Unmanned Aerial Vehicle

Small-scale supersonic unmanned aerial vehicles (SSUAVs) require powerful and robust propulsion systems that can accelerate the vehicle through the transonic regime. While turbojet, turbofan, ramjet, and combined-cycle engines have been used on larger supersonic vehicles, the feasibility of a miniature turbojet engine to break the sound barrier, particularly in the context of small-scale, supersonic applications, remains underexplored. Therefore, the primary objective of the current work is to quantify the performance of an SSUAV powered by a miniature turbojet. In particular, the key flight conditions (e.g., Mach number, altitude) that correspond to the performance of the turbojet propulsion system will be identified. Due to the large number of possible conditions for evaluation, a combination of one-dimensional (1-D) propulsion modeling and computational fluid dynamics (CFD) simulations is employed instead of full combustion modeling, which would require prohibitively high computational time and hardware resources. The in-house 1-D propulsion model includes details on the streamtube, Fanno flow, conservation of mass correction, and choked flow condition correction. The CFD solver uses pimpleCentralFoam in OpenFOAM with Reynolds-average Navier-Stokes (RANS) turbulence modeling. An assessment process was conducted to quantify the uncertainty associated with aerodynamics and propulsion modeling based on a systematic comparison of key flow variables predicted by the propulsion model with those obtained from CFD simulations. Simulation results will be analyzed to provide generalized insights and design guidelines for SSUAV propulsion with turbojets.