Effect of Fuel Injection Strategy on Generic Scramjet Combustor Operation

Parameters such as fuel injector orientation, fuel flow rate, and stagnation temperature affect scramjet engine operation. In this work, three fuel injection methods were used to supply the combustor of a generic cavity-based scramjet flowpath with gaseous ethylene: upstream normal (up1), upstream angled (up2), and downstream normal (down1). Various combinations of fuel flow rates and fuel injection methods were explored using two stagnation temperatures ([Formula: see text] and [Formula: see text]) and one stagnation pressure ([Formula: see text]) for a Mach-1.8 facility nozzle. The pre-ignition local equivalence ratio ([Formula: see text]) in the cavity was leaner and less sensitive to global [Formula: see text] with up1 fueling than up2 fueling. For reacting conditions, up1 fueling required a higher global [Formula: see text] than up2 fueling to obtain the same specific stream thrust metric, calculated from pressure measurements along the flowpath. Redistributing fuel from up2 to down1 resulted in a lower specific stream thrust metric, but redistribution from up1 to down1 produced a higher specific stream thrust metric. The range of attainable global [Formula: see text] shifted to richer values with a step increase in stagnation temperature due to the reduced ratio of heat release from a given quantity of fuel relative to the total flow enthalpy.