COMBUSTION INITIATORS FOR HIGH SPEED AIRCRAFT APPLICATIONS

The high air velocity and relatively low air temperature in the combustors of hydrocarbon-fueled scramjet engines lead to long ignition delays, and problems with flame holding, combustion stability and heat release. These problems are particularly severe near the ram/scram mode transition. High internal air velocities and long ignition delays can require long combustor lengths to allow heat release from the fuel before it passes into the exhaust nozzle. Excessive combustor lengths and large flameholding recirculation zones cause large fuel heat loads and internal total pressure losses, hurting cycle performance and limiting the maximum flight speed. Use of a combustion initiator to improve the reactivity of the fuel and shorten the ignition delay could allow the combustor to be shortened and eliminate the draggy flameholding recirculation zones. This would substantially improve overall cycle performance, decrease the heat loads imposed on the fuel, decrease engine weight, and allow higher flight speeds. Metering of the initiator compound into the fuel could also allow control over the heat release profile within the engine.