Two-Dimensional Scramjet Engine Inlet Design and Computational Fluid Dynamics Analysis for Mach 6 Flight

Abstract

Because it uses the forward momentum of the vehicle to compress the incoming air rather than spinning compressor and turbine hardware, the supersonic combustion ramjet (scramjet) is one of the most promising air-breathing propulsion ideas for sustained flight beyond Mach 5. Performance at the inlet directly affects the efficiency of combustion downstream and net thrust in this configuration because it is responsible for capturing air from the free stream, increasing its pressure through a sequence of oblique shocks, and delivering a relatively uniform, high-pressure flow to the combustor while limiting total-pressure loss. In this work, we detail the planning and analysis of a two-dimensional scramjet intake with two ramps, optimized for Mach 6 operation at 30 km altitude. We used standard oblique-shock relations and a shock-on-lip criterion to size the inlet geometry, which consists of two compression ramps, a cowl, and a constant-area isolator duct. We then built the model as a solid in CATIA V5. After that, we imported it into ANSYS Fluent to do compressible-flow analysis with a density-based solver and the SST k-ϋ turbulence model. Before applying the same meshing strategy to the designed inlet for an inviscid run, a twodimensional viscous run, and a three-dimensional viscous run capturing sidewall effects, a meshdependency study was performed on a previously validated two-ramp inlet geometry to fix an appropriate cell size. We compare the threedimensional analysis, the inviscid and viscous CFD findings, and the one-dimensional design calculations. As compared to the inviscid case, the results demonstrate that the captured air is gradually compressed through the ramp shock system while the flow remains supersonic all the way to the isolator exit. In the viscous solution, there is measurable shock displacement and localized flow separation near the ramp-cowl shoulder. Additionally, the threedimensional analysis reveals that there is sidewalldriven non-uniformity that fades within about 8 mm of the side surfaces. The design point pressure recovery and flow uniformity are both within acceptable ranges, suggesting that the geometry is a good starting point for a Mach 6 scramjet inlet. However, there are some areas that need further refinement, specifically viscous, off-design, and sidewall effects.