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Atomization and Sprays
Fator do impacto: 1.189 FI de cinco anos: 1.596 SJR: 0.814 SNIP: 1.18 CiteScore™: 1.6

ISSN Imprimir: 1044-5110
ISSN On-line: 1936-2684

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Atomization and Sprays

DOI: 10.1615/AtomizSpr.v20.i6.30
pages 513-524

CAVITATION IN NOZZLES OF PLAIN ORIFICE ATOMIZERSWITH VARIOUS LENGTH-TO-DIAMETER RATIOS

Akira Sou
Kobe University
Shigeo Hosokawa
Kobe University
Akio Tomiyama
Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe, 657-8501, Japan

RESUMO

Cavitation in two-dimensional and cylindrical nozzles with various length-to-diameter (L/D) ratios and its effects on liquid jet deformation are investigated by carrying out simultaneous high-speed visualization of the cavitation and jet. The applicability of a modified cavitation number to quantitative prediction of supercavitation formation for nozzles with various L/D ratios is also examined. As a result, the following conclusions are obtained. (1) The modified cavitation number σc can predict supercavitation in nozzles of various shapes and L/D ratios. (2) When cavitation length Lcav is less than twice the nozzle diameter D, the cavitation length normalized by the diameter (Lcav/D), rather than by the nozzle length (Lcav/L), can be expressed as a unique function of σc. (3) Once a cavitation film is formed in long nozzles (L/D ≥ 4), the cavitation zone suddenly extends to near the exit even for very long nozzles (L/D = 8). (4) In short nozzles (L/D = 2), incipient cavitation consisting of tiny bubbles can reach the vicinity of the exit. However, a hydraulic flip instead of a cavitation film is formed even at a low flow rate. (5) In long nozzles (L/D = 8), hydraulic flip does not occur even at very high flow rates, which is preferable for a plain orifice atomizer. (6) Cavitation clouds are shed and collapse near the exit to induce a large deformation of the discharged jet, not only in moderately long (L/D = 4) but also in shorter and longer nozzles.