非対称二次元ノズルから放出された強制脈動噴流

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Mixing/diffusion enhancement is one of key technologies in various industrial aspects, and is needed in chemical reactors, heat exchangers, burners/combustors, low-noise jet engines, air conditioners and so on. Jets are known to be useful for such mixing/diffusion enhancement. In the present study, the authors research the jet from an asymmetrical two-dimensional nozzle, of which the asymmetry is introduced by a lip attached to only one side of the nozzle exit. Especially, the authors focus on the influence of forced jet's pulsation. Experiments are conducted at a Reynolds number of 6,000. The aspect ratio of a nozzle exit is fixed to 300, and a nozzle-lip length l which represents the geometrical asymmetry of the nozzle is equal to 0, 3.3h or 5.0h, where h denotes the height of the nozzle exit. Using a hot-wire anemometer, the authors show mean-velocity profiles, comparing the pulsating flow with the non-pulsating flow. As a result, the authors have successfully attained such a sufficiently-two-dimensional jet as the quasi-plain jet without the forced pulsation, at the reduced lip length l/h = 0 – 5.0 even for the pulsating flow. Then, the authors have clearly observed a jet-pulsation influence to enhance such an asymmetrical effect as the increase in entrainment flow rate. That is, the local time-mean flow rates of the pulsating flow is everywhere larger than that of non-pulsating flow for each l/h. Especially for l/h = 5.0, the jet's bias shows such features as (1) a lip-wards deflection and (2) a spacial meander of the jet axis. The forced pulsation also enhances the l/h effects upon these two features.
2013-10-00

非対称二次元ノズルから放出された強制脈動噴流

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