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Characteristics of transient, swirl-generated, hollow-cone sprays

Characteristics of transient, swirl-generated, hollow-cone sprays
Characteristics of transient, swirl-generated, hollow-cone sprays
The near-nozzle, global, spatial, and temporal characteristics of a hollow-cone spray produced by a pressure swirl-type atomizer have been investigated experimentally. Particular attention is given to the transient phase just after needle opening, which, for pulsed or intermittent atomizers, plays an all-important role in defining the global spray behavior and, more significantly, atomization quality. Qualitative and quantitative spray measurements have been achieved via the combined diagnostic techniques of high-magnification charge-coupled device (CCD) imaging and phase Doppler anemometry (PDA), which provides useful data not only in terms of improving the design and performance of pressure swirl atomizers, but also for the validation and refinement of numerical spray models. High-magnification CCD images of the intact near-nozzle liquid sheet reveal a certain degree of helical swirl motion, although laser Doppler velocimetry (LDV) results indicate that the tangential swirl motion imparted on the liquid sheet decays rapidly within the first few millimeters of the atomizer orifice to near-negligible levels. Images of the poorly atomized “preswirl spray” formed during the early transient phase of injection also revealed the presence of large, nonspherical liquid masses up to 1 mm in size, even as far as 72 nozzle diameters downstream. The spray-induced gas phase flow, which results in the characteristic toroidal vortex, was found to have a significant influence on droplet trajectories and segregation of the fast-moving large (D32 between 25 and 30 ?m) and small (1?5 ?m) droplets within the spray. Estimates of characteristic droplet Weber numbers have also been made, which, in general, were found to be less than the critical values required for secondary droplet breakup to occur.
1045-5110
498-510
Kashdan, Julian T.
151a1a96-2bf2-406f-92fa-3840b7edc9f0
Shrimpton, John S.
9cf82d2e-2f00-4ddf-bd19-9aff443784af
Kashdan, Julian T.
151a1a96-2bf2-406f-92fa-3840b7edc9f0
Shrimpton, John S.
9cf82d2e-2f00-4ddf-bd19-9aff443784af

Kashdan, Julian T. and Shrimpton, John S. (2006) Characteristics of transient, swirl-generated, hollow-cone sprays. Atomization and Sprays, 16 (5), 498-510. (doi:10.1615/AtomizSpr.v16.i5.20).

Record type: Article

Abstract

The near-nozzle, global, spatial, and temporal characteristics of a hollow-cone spray produced by a pressure swirl-type atomizer have been investigated experimentally. Particular attention is given to the transient phase just after needle opening, which, for pulsed or intermittent atomizers, plays an all-important role in defining the global spray behavior and, more significantly, atomization quality. Qualitative and quantitative spray measurements have been achieved via the combined diagnostic techniques of high-magnification charge-coupled device (CCD) imaging and phase Doppler anemometry (PDA), which provides useful data not only in terms of improving the design and performance of pressure swirl atomizers, but also for the validation and refinement of numerical spray models. High-magnification CCD images of the intact near-nozzle liquid sheet reveal a certain degree of helical swirl motion, although laser Doppler velocimetry (LDV) results indicate that the tangential swirl motion imparted on the liquid sheet decays rapidly within the first few millimeters of the atomizer orifice to near-negligible levels. Images of the poorly atomized “preswirl spray” formed during the early transient phase of injection also revealed the presence of large, nonspherical liquid masses up to 1 mm in size, even as far as 72 nozzle diameters downstream. The spray-induced gas phase flow, which results in the characteristic toroidal vortex, was found to have a significant influence on droplet trajectories and segregation of the fast-moving large (D32 between 25 and 30 ?m) and small (1?5 ?m) droplets within the spray. Estimates of characteristic droplet Weber numbers have also been made, which, in general, were found to be less than the critical values required for secondary droplet breakup to occur.

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Published date: 2006

Identifiers

Local EPrints ID: 64559
URI: http://eprints.soton.ac.uk/id/eprint/64559
ISSN: 1045-5110
PURE UUID: a02fcff0-6ec4-48b2-9e3d-7fb24f7272a6

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Date deposited: 23 Dec 2008
Last modified: 15 Mar 2024 11:54

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Author: Julian T. Kashdan

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