Numerical investigation of hydrogen jet penetration and mixing enhancement in a scramjet combustor: Effects of a 4-lobe nozzle strut injector in supersonic crossflow

The role of a strut injector as a conventional fuel mixing enhancer in the scramjet combustion chamber has been computationally investigated, with a focus on hydrogen-air mixing dynamics. This study analyzes a strut-based injection system coupled with a 4-lobe annular injector, emphasizing the interplay between vortical structures, hydrogen penetration, and mixing mechanisms. The influence of an internal air jet on hydrogen dispersion and its interaction with the free stream is rigorously examined. Simulations employ the RANS equations with the SST turbulence model to resolve the flowfield, revealing critical insights into the strut-generated vortices and their role in distributing hydrogen fuel downstream. Results demonstrate that the lobe-shaped injector promotes hydrogen penetration by leveraging shock-induced vortices, while the air jet significantly amplifies mixing efficiency (up to 25 % improvement) near the injector by enhancing hydrogen-air contact. The analysis highlights the dominance of large-scale vortices in entraining air into the hydrogen core, a key mechanism for rapid mixing in the combustion chamber. Furthermore, the study identifies challenges in predicting post-Mach disk pressure drops, underscoring the sensitivity of hydrogen-air mixing to localized turbulence and grid resolution. These findings establish a framework for optimizing strut-based injection systems to achieve efficient hydrogen-air mixing, critical for sustaining stable combustion in high-speed flows.