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Combustion, Explosion and Shock Waves

2018 year, number 6

Effect of the Wave Structure of the Flow in a Supersonic Combustor on Ignition and Flame Stabilization

M. A. Goldfeld1, Yu. V. Zakharova1, A. V. Fedorov1, N. N. Fedorova1,2
1Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
2Novosibirsk State University of Architecture and Civil Engineering, Novosibirsk, 630008 Russia
Keywords: сверхзвуковое течение, турбулентность, ударная волна, волна разрежения, камера сгорания, подготовленная смесь, воспламенение, supersonic flow, turbulence, shock wave, expansion wave, combustor, prepared mixture, ignition

Abstract

Results of numerical and experimental investigations of a high-velocity flow in a plane channel with sudden expansion in the form of a backward-facing step, which is used for flame stabilization in a supersonic flow, are presented. The experiments are performed in the IT-302M high-enthalpy short-duration wind tunnel under the following test conditions: Mach number at the combustor entrance 2.8, Reynolds number 30 × 106 m-1, and total temperature T0 = 2000 K, i.e., close to flight conditions at M = 6. The numerical simulations are performed by solving full unsteady Reynolds-averaged Navier-Stokes equations supplemented with the k-ω SST turbulence model and a system of chemical kinetics including 38 forward and backward reactions of combustion of a hydrogen-air mixture. Three configurations of the backward-facing step are considered: straight step without preliminary actions on the flow, with preliminary compression, and with preliminary expansion of the flow. It is demonstrated that the backward-facing step configuration exerts a significant effect on the separation region size, pressure distribution, and temperature in the channel behind the step, which are the parameters determining self-ignition of the mixture. The computed results show that preliminary compression of the flow creates conditions for effective ignition of the mixture. As a result, it is possible to obtain ignition of a prepared hydrogen-air mixture and its stable combustion over the entire channel height.