Super-Mixing High-Speed Combustion Enhanced by Unsteady Fuel Injection with Timescale of Micro Shear Layer

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In order to embody extremely high-speed diffusion combustion, micro shear layers formed near the planar nozzle of 0.5。ォ1 mm in width were excited by acoustic resonance. For nonreacting jet experiments, Schlieren visualization and flow measurement by a hot-wire anemometer show that the marked amplification of turbulence is induced by the acoustic excitation with the frequencies proportional to the nozzle-exit velocity. Analogously, visual observation, temperature and concentration measurements for the reacting jet demonstrate that combustion is much enhanced under the resonant condition. For the planar jets injected from the nozzles of 0.5。ォ1 mm in width, acoustic excitation was applied. In both the nonreacting and reacting jets, resonant phenomena were clearly confirmed. The Strouhal number for the resonant condition was almost constant for each case, but varies largely depending on reacting or nonreacting conditions. The dramatic changes observed in the present experiments are ascribed to the combination of acoustic excitation and micro shear layers.