On the Aero-Thermo-Structural Performance of Rectangular and Axisymmetric Scramjet Configurations 2024-26-0441

Scramjet-based hypersonic airbreathers are needed for next-generation defense and space applications. Two scramjet configurations, namely, rectangular and axisymmetric, are primarily studied in the literature. However, there is no quantitative comparison of the performance metrics between these two scramjet configurations. This study investigates the aero-thermo-structural performance of rectangular and axisymmetric scramjet engines at Mach 7 and 25 km altitude. A numerical framework involving computational fluid dynamics and computational structural dynamics is established. The aero-thermo-structural loads on the scramjet flow path are estimated using RANS/FANS simulation. A finite element-based coupled thermo-structural analysis is performed to understand the thermo-structural response. Before using the numerical models for the study, CFD and CSD modules are validated with literature data. The presence of oblique shocks in rectangular scramjets provides better compression than conical shocks in axisymmetric scramjets. Thus, the rectangular scramjet shows improved aerodynamic efficiency from a high lift-to-drag ratio. However, rectangular scramjet suffers from a high convective heat transfer rate due to high compression and shows large thermo-structural deformations and stress. Axisymmetric scramjet performs better mass capture than rectangular scramjet, influencing the propulsive efficiency. The large surface area available in axisymmetric scramjet allows for improved heat dissipation. Both scramjet configurations have associated advantages and disadvantages that are quantified through the aero-thermo-structural performance metrics. A unified scramjet configuration can combine rectangular and axisymmetric scramjets, such as Rectangular-to-Axisymmetric Shape Transition or REST scramjet.