The Russian Central Institute of Aviation Motors (CIAM) performed a flight test of a CIAM-designed, hydrogen-cooled/fueled dual-mode scramjet engine over a Mach number range of approximately 3.5 to 6.4 on February 12, 1998, at the Sary Shagan test range in Kazakhstan. This rocket-boosted, captive-carry test of the axisymmetric engine. reached the highest Mach number of any scramjet engine flight test to date. The flight test and the accompanying ground test program, conducted in a CIAM test facility near Moscow, were performed under a NASA contract administered by the Dryden Flight Research Center with technical assistance from the Langley Research Center. Analysis of the flight and ground data by both CIAM and NASA resulted in the following preliminary conclusions. An unexpected control sensor reading caused non-optimal fueling of the engine, and flowpath modifications added to the engine inlet during manufacture caused markedly reduced inlet performance. Both of these factors appear to have contributed to the dual-mode scramjet engine operating primarily in a subsonic combustion mode. At the maximum Mach number test point, combustion caused transition from supersonic flow at the fuel injector station to primarily subsonic flow in the combustor. Ground test data were obtained at similar conditions to the flight test, allowing for a meaningful comparison between the ground and flight data. The results of this comparison indicate that the differences in engine performance are small.

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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.

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