A comprehensive analysis of the efficiency of an approach based on the injection of a thin oxygen stream, subjected to a tailored electric discharge, into a supersonic H 2 -air flow to enhance the combustion performance in the mixing layer and in the scramjet combustor is conducted. It is shown that for such an approach there exist optimal values of reduced electric field E/N and transversal dimension d of the injected oxygen stream, which provide the minimal length of induction zone in the mixing layer. The optimal values of E/N and d depend on air flow parameters and the specific energy put into the oxygen. The injection of a thin oxygen stream (d = 1 mm) subjected to an electric discharge with E/N = 50-100 Td, which produces mostly singlet oxygen O 2 (a 1 g ) and O 2 (b 1 + g ) molecules and atomic oxygen, allows one to arrange stable combustion in a scramjet duct at an extremely low air temperature T air = 900 K and pressure P air = 0.3 bar even at a small specific energy put into the oxygen E s = 0.2 J ncm −3 , and to provide rather high combustion completeness η = 0.73. The advance in the energy released during combustion is much higher (hundred times), in this case, than the energy supplied to the oxygen stream in the electric discharge. This approach also makes it possible to ensure the rather high combustion completeness in the scramjet combustor with reduced length. The main reason for the combustion enhancement of the H 2 -air mixture in the scramjet duct is the intensification of chain-branching reactions due to the injection of a small amount of cold non-equilibrium oxygen plasma comprising highly reactive species, O 2 (a 1 g ) and O 2 (b 1 + g ) molecules and O atoms, into the H 2 -air supersonic flow.

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The possibility of the combustion enhancement in a supersonic flow of H 2 -O 2 mixture by activation of molecular oxygen in electrical discharge is analyzed. It is demonstrated that abundance of excited oxygen molecules O2(a 1 ∆g) and O2(b 1 Σ + g ) in the oxygen plasma is responsible for accelerating chain-branching reactions and allows one to arrange the stable combustion in a low temperature supersonic flow at a small discharge energy deposited to the gas. : 51.50.+v, 52.77.-j, 52.80.-s PACS

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Specific features of formation of an oblique detonation wave in a supersonic hydrogenoxygen mixture flow over a plane wedge are analyzed. Preliminary excitation of molecular vibrations of H 2 is shown to lead to a noticeable (severalfold) decrease in the induction-zone length and the distance at which the detonation wave is formed. These effects are manifested even if H 2 molecules are excited in a narrow region in the vicinity of the flow centerline. The reason for these effects is intensification of chain reactions in the H 2 -O 2 (air) mixture owing to the presence of vibrationally excited hydrogen molecules in the flow.