Integration assessment of conceptual design and intake aerodynamics of a non-conventional air-to-ground fighter aircraft

Abstract

The conception of non-conventional aircraft, whose goal is achieving a certain performance or operational improvement is undoubtedly, one of the biggest challenges in aeronautical engineering. This work presents the conceptual design of a non-conventional air-to-ground fighter aircraft, whose main design feature is an inverted-rectangular dorsal intake, followed by a three-dimensional transitioning S-duct diffuser with circular cross-section at aerodynamic interface plane. An in-house presizing tool was developed to define the key layout characteristics and select the optimal airframe-engine combination regarding the design requirements, whereas Reynolds-averaged Navier–Stokes (RANS) simulations were also conducted to assess the performance of both, the intake-airframe integration and the drag polar of the aircraft at several flight conditions. The results found in this work were evaluated separately. First, the analytic design method of the intake itself was compared with numerical simulations in order to check and maximize the total pressure recovery at the on-design condition. Subsequently, the intake-airframe integration assessment took place, showing that adequate performance and compatibility characteristics are maintained during subsonic and transonic maneuvers. However, at supersonic velocities, there is a flow expansion on the fuselage and wings that reduce the intake performance levels. These studies provided extensive data to evaluate the effects of specific aircraft design variables on dorsal intake performance, such as the integration of the cockpit, the boundary layer diverter, and several delta wing planforms. Results show that dorsal intakes are a promising alternative for aircraft that require only reasonable supersonic maneuverability capabilities and high subsonic and transonic capabilities, such as an air-to-ground fighter aircraft. In addition, dorsal intake coupled to S-duct diffuser provide line-of-sight blockage of the engine blades, satisfying the requirement of low radar signature, lightweight and low drag of the next generation of fighter aircraft.