Microwave and Direct-Current Discharges in High-Speed Flow: Fundamentals and Application to Ignition

DOI: 10.2514/1.24803 The main parameters and properties of an electrodeless freely localized microwave discharge, a surface microwave discharge, transversal in relation to the gas flow direct-current and pulse-periodic electrode discharges, andacombined microwavedirect-current dischargeareexperimentally investigated.It isshown thatalltypesof the discharges result in a reliable ignition of hydrocarbon fuel. Combustion of a propane–air supersonic stream is realized under condition of the combined surface microwave and direct-current discharge. To find out the influence ofdifferent channels ofenergy transfer onignition ofcombustible mixtures in asupersonic flow,the kinetic modelof ignition of hydrocarbons–air mixtures, and taking into account the influence of electric field on processes of dissociation molecules and creation of the active radicals, excited and charged (electrons, positive and negative ions) particlesunderconditionsofnonequilibriumplasmaofthegasdischargewasdeveloped.Mathematicalmodelinghas revealed a strong influence of the reduced electric field on induction period. The microwave discharges may find applications in different fields of supersonic plasma aerodynamics and in development of new-generation plasma sources for plasma chemistry, nano- and microelectronics purposes (plasma treatment of surfaces, etching, and film deposition), and so on.