Computational Investigation of Airframe Integration Effects on Turbojet Engine Aerodynamics and Combustion

This study employs high-fidelity, unsteady, three-dimensional CFD simulations to develop a comprehensive framework for engine-airframe integration, investigating the aerodynamic interactions between a commercial airframe model and a fully-annular turbojet engine, including heat propulsion components (combustor, turbine, and nozzle). The structural completeness of the engine ensures accurate internal aerodynamic and combustion modeling. Comparative analysis under varying incidence angles evaluates coupled engine-airframe configurations against standalone engine cases, emphasizing the propagation of airframe-induced aerodynamic effects on entire engine performance, particularly in heat propulsion components. The study reveals that the airframe-induced distorted inflow entering the engine compressor triggers circumferentially rotating low-energy vortices at approximately 10% of the impeller's rotational speed, along with strong shock waves. These phenomena reduce flow capacity by 4.5%, decrease pressure ratio by 3.4%, and increase aerodynamic instability. The airframe coupling effect persists through cross-component propagation, exacerbating internal aerodynamic and combustion processes in downstream heat propulsion components. Increased compressor instability disrupts combustor flow distribution, intensifies temperature non-uniformities, amplifies combustion oscillations, and promotes hotter streaks at the combustor exit. These effects result in an 8.0$%$ increase in swirl angle and a 9.3% rise in OTDF at the turbine inlet, which intensifies hot streak migration on turbine blades and alters their migration patterns. Additionally, external flow interactions cause substantial nozzle flow non-uniformities.