Examining Distributed Fueling Schemes Using Tandem Cavities in a Mach 8 Scramjet

A fundamental investigation of combustion behavior in an ethylene-fueled Mach 8 axisymmetric scramjet combustor was numerically conducted using US3D Reynolds-averaged Navier–Stokes to evaluate the impact of fueling strategies employed with a tandem cavity-equipped combustor. Five fueling configurations with a consistent total fuel-to-air equivalence ratio at 75% of stoichiometric were assessed using a combination of injector ports, located either upstream of, within, between, or downstream of the cavities. Cold-wall and hot-wall conditions were examined, representing shock tunnel equivalent test conditions with minimal wall heating and steady, in-flight wall temperatures, respectively. Two distributed fueling schemes resulted in higher combustion performance when operating in cold conditions and comparable performance when operating in hot conditions. Total pressure losses sustained under each distributed fueling method were equivalent to or lower than those sustained by cases with fuel injected only upstream of the cavities. All distributed schemes examined delayed the onset of flow separation, resulting in improved operational stability and higher resistance to engine unstart.