Fuel mixing and thermal enhancement behind an inclined strut in a supersonic combustor via single annular with air-assisted injector

In the present investigation, thermal and mixing efficiencies of the fuel jet behind the strut within combustor of scramjet engine have been extensively investigated. Combination of annular with/without internal air flow in two strut angles of 15° and 7.5 are analyzed via three-dimensional modelling of fuel jet released from single injector. Important flow features and vortex structure are evaluated to reveal the mixing nature of the proposed system. Computational fluid dynamic is used for the modelling of flow in combustor via solving RANS equations with SST turbulence model. The results reveal that the combination of a 7.5° strut angle with an internal air jet results in a 31% improvement over the baseline annular-only case at the same angle, achieving the highest mean mixing index of 0.495. Although the 15° strut with internal air jet produces the highest initial circulation strength (∼0.85), its mixing effect diminishes more rapidly downstream due to strong localized flow separation. In contrast, the 7.5° case with air assist maintains strong and consistent circulation (∼0.60 to 0.30) over a longer distance, leading to superior mixing uniformity. The internal air jet significantly enhances the breakup of the annular jet, introduces central vortices, and increases fuel-air interface area in all cases. These findings demonstrate that an inclined strut with integrated air-assisted annular injection, particularly at moderate angles, offers energy-efficient solution for improving fuel-air mixing in high-speed combustion applications.