Off-design characteristics of a scoop-type streamline-tracing scramjet inlet

Abstract

This study investigates the off-design characteristics of a scoop-type streamline-tracing inlet, focusing on identifying its operable envelope using numerical and experimental methods, with experiments primarily conducted for validation purposes. The fixed geometry of streamline-tracing inlets necessitates this research, and a scoop-type inlet is targeted because it has the minimum viscous drag owing to the minimum wetted area between the streamline-tracing inlet variants. A scoop inlet with a cruise Mach number (M) of 6 and contraction ratio of 4.14 was designed, with three different values of M and various angles of attack (AoAs) used to simulate its flight in on- and off-design freestream conditions. Computational results were used to delineate the unstart boundaries with regard to AoA for each tested M. Predictably, the inlet exhibited the widest operable range for the on-design M. The flow fields for the on- and off-design conditions were compared, as were the contraction ratio, captured mass flow rate, pressure ratio, inlet exit, M, and total pressure recovery. The results indicated that the inlet performance deteriorated when the flow condition deviated from the on-design condition. However, the scoop-type inlet maintained its performance for a relatively wide range of off-design conditions, confirming its potential versatility for various flight missions.