Multipoint design optimization of Busemann-based intakes for scramjet-powered ascent flight

Scramjet engines are one of the most promising hypersonic airbreathing propulsion technologies for robust, efficient, and economical access to space. Multi-objective design optimization has been conducted for Busemann-based intakes in inviscid and viscous regimes at single and multiple design points, respectively, by means of surrogate-assisted evolutionary algorithms coupled with computational fluid dynamics in the present research. Intake geometries are generated by applying geometric alterations to the full Busemann intake via leading-edge truncation, axial stunting, and radial contraction, aiming to simultaneously minimize intake drag and maximize the compression efficiency at two different design conditions (i.e., Mach 7.7 at an altitude of 30 km and Mach 10 at 33.5 km on a constant dynamic pressure ascent trajectory). The single-point inviscid optimization study has found that the nondominated solutions obtained from minimizing drag and maximizing compression efficiency are approximately the same as those obtained from maximizing total pressure recovery and minimizing static pressure ratio. From the multipoint viscous optimization study, the optimal solutions have been found to retain the original advantages of the inviscid full Busemann intakes in terms of high compression efficiency with shorter intakes and higher static pressure as well as adequately high mean exit temperature for both design conditions.