Improvement of the fuel mixing of ramp injector system via 4-lobe nozzle at scramjet engine

The ramp injection system has been extensively used for the fuel distribution and mixing inside the combustor of scramjet engines. This article presents a three-dimensional numerical study of the ramp injection system with an annular four-lobe nozzle at supersonic flow (Mach = 2). The finite volume approach is selected for the modeling of supersonic airflow and hydrogen jet near the ramp injector. The usage of internal air jets for enhancement of the fuel mixing is also investigated in the present study. Meanwhile, distribution of the fuel jet by the production of the vortex is fully analysed. The trails of fuel concentration and interactions of the injected fuel with the free stream behind the jet are fully investigated in this research. The obtained result shows that the 4-lobe nozzle results in three vortex pairs which considerably improve the fuel diffusion into the free stream air flow. Moreover, the addition of an air jet expands these vortex pairs, and consequently, fuel mixing is improved by 85 % near the 4-lobe injector. •A three-dimensional numerical analysis is performed on a ramp injection system with an annular four-lobe nozzle at Mach =2.•The finite volume method is employed to model the supersonic airflow near the ramp injector.•The impact of internal air jets on enhancing fuel mixing is also explored.•Results show that the 4-lobe nozzle generates three vortex pairs, significantly improving fuel diffusion into the free stream airflow.•The addition of an air jet leading to an 85 % improvement in fuel mixing near the 4-lobe injector.