Energy Efficiency of Plasma-Assisted Combustion in Ram/Scramjet Engines
Analysis of energy and power requirements for shortening the ignition delay time in hydrocarbon-fueled scramjet engines using nonequilibrium plasma generation of radicals shows that the uniform volumetric plasma ignition would be associated with extremely high power budget and substantial losses of total pressure. A multi-point, repetitively pulsed plasma ignition scheme is proposed that would reduce the power budget by several orders of magnitude. The paper also explores an approach where the fuel is injected into the core flow as a liquid jet, and low-power electron beams are used to electrostatically charge the droplets and thus to control droplet break-up, atomization, and mixing. With a subcritical microwave field applied to the injection region, local enhancement of electric field strength at the surface of droplets, due to both the electric charge and the field increase near the polarized dielectric body, together with seed electrons and ions produced by the electron beam, would create subcritical microwave discharges and thus initiate combustion in multiple spots. The multi-spot ignition would help in spreading the flame across the combustor. Additionally, the initiation of combustion at the droplet surface, where local equivalence ratio is high, could help ignite lean (in average) mixtures. 2005 by the authors.