Development of a chevron–air jet injection strategy for improving fuel mixing mechanism in high-speed combustors

Abstract

Efficient fuel–air mixing in supersonic combustors remains one of the key challenges in scramjet propulsion due to the extremely short residence time and the strong compressibility effects within the high-speed flow. This study numerically investigates the three-dimensional flow and mixing characteristics of a novel chevron annular injector integrated into a strut, operating under a Mach 2.2 crossflow with and without an internal air jet. Three chevron geometries (Chevron No.1, No.2, and No.3) were analyzed using high-fidelity computational fluid dynamics (CFD) simulations to examine the effects of chevron depth and air jet interaction on jet penetration, vortex formation, shock structures, and overall mixing efficiency. The boundary conditions were defined by a static pressure of 100 kPa, a freestream temperature of 340 K, and a hydrogen injection total pressure ratio of 0.1. Results reveal that the inclusion of the internal air jet significantly enhances the mixing performance and flow uniformity while reducing total pressure loss compared to configurations without air injection. The air jet strengthens streamwise vortices, stabilizes the barrel shock, and increases shear-layer entrainment, leading to faster and more homogeneous hydrogen–air mixing. Among the investigated geometries, Chevron No.2 with internal air jet provides the optimal balance between effective mixing, controlled jet expansion, and minimal total pressure loss. The results confirm that the combined use of a chevron annular injector and an internal air jet presents a highly promising approach for achieving efficient fuel–air mixing in compact, high-performance scramjet combustors.