Streamwise porthole fuel injection for boundary-layer combustion inside a scramjet engine

Due to its low practicality, an alternative to slot injection is desirable for boundary layer fuel injection in scramjet engines. An array of porthole injectors in the face of a backward step is examined as a possible alternative. Skin friction drag reductions predicted through CFD are compared to slot injection for a variety of porthole spacings with constant fuel mass flow. While the fuel did not ignite within the domain of the simulation, film-cooling induced drag reductions show that porthole injection can provide comparable performance when injectors are spaced sufficiently close. Mixing of the fuel and mainstream air is shown to increase as jet spacing goes up; after ignition, wider jet spacing may lead to improved combustion and therefore further improvements to skin friction drag reduction