Variable Geometry Inlets for Hypersonic Scramjets: Effects on Boundary Layer Behavior and Performance
DOI:
https://doi.org/10.58445/rars.3372Keywords:
Boundary layer, hypersonic flight, scramjet propulsion, variable geometry inletsAbstract
Scramjet propulsion offers the potential for sustained hypersonic flight, but inlet design remains a central challenge. At Mach 5 and above, boundary layers thicken rapidly, interact with shocks, and often cause separation, flow distortion, and unstart. These effects reduce pressure recovery and threaten engine stability. Variable geometry inlets, proven effective in supersonic aircraft such as the SR-71 and Concorde, present a possible solution by dynamically adjusting shock structures and mitigating boundary layer growth. While no scramjet has yet flown with true variable geometry, computational and experimental studies suggest that adaptive features could expand operability and improve efficiency. This paper reviews the evolution of inlet theory, examines boundary layer effects in hypersonic scramjets, and evaluates the potential of variable geometry. The analysis concludes that adaptability may be key to practical scramjet propulsion, though advances in materials and morphing structures will be necessary for implementation in the extreme conditions of hypersonic flight.
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