Experimental and numerical studies on spray characteristics of an internal oscillating nozzle

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© 2019 by Begell House, Inc. An open atomization test bench based on high-speed Schlieren technology and a Malvern particle size analyzer was developed to investigate the effects of different injection pressures (0.12 MPa to 0.24 MPa) on spray characteristics of an internal oscillating nozzle, including the spatial distribution of flow rate, oscillation frequency, spray cone angle, spatial distribution of spray particle size, and velocity. A numerical investigation that simultaneously considered the internal flow field and the external spray within the same computational field was performed to reveal the oscillation mechanism. The experimental results indicated that the spray of the internal oscillating nozzle shows a fan shape distribution with small flow in the middle and large distribution on both sides. The flow rate gradually increases with the rising of injection pressure and reaches its maximum at 0.24 MPa when the distance from the nozzle is constant. The oscillating frequency keeps an upward tendency with a maximum growth rate when the injection pressure ascends from 0.15 MPa to 0.18 MPa. The spray cone angle does not change significantly with the increase of the injection pressure, fluctuating at approximately 41.8 degrees. Moreover, a critical injection pressure is obtained, below which the droplet size increases with the rise of the injection pressure and above which the droplet size declines moderately. The numerical investigation revealed that the oscillation phenomenon was generated due to the periodic establishing and vanishing of the pressure gradient within the feedback channels, and the Coanda effect occurred in the main flow passage.

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Atomization and Sprays