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Title: The internal flow physics of swirl atomizer nozzles
Author: Chinn, John Joss
ISNI:       0000 0001 3544 9105
Awarding Body: University of Manchester : UMIST
Current Institution: University of Manchester
Date of Award: 1996
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The internal flow of pressure swirl atomizers is studied with the ultimate aim of developing a design tool for such atomizers, particularly to enable the production of the finest possible water sprays (for any given supply pressure) for fire suppression purposes. The primary direction of the research was in computationally modelling this flow with a two-dimensional assumption and a methodology is described which is capable of determining the velocity profiles and, for the first time in the literature, the air-core topology and discharge coefficient, for nozzles which approximate the axially-symmetric condition. The results are compared with the experimental results from both the literature and also from research which was carried out under the supervision of the author. The predictions show important flow features, which are found in the experiments and have not been recognised in the "classically" assumed internal flow. These include concentration of the axial flow near the air-core and toroidal vortices, similar to Taylor-Göertler vortices found in Taylor-Couette flow, which are visible in planes through the nozzle axis. The secondary direction of the research is in both reviewing and improving upon simplified analytical techniques which have been used to estimate the size of the air-core radius at the nozzle exit together with the values of the discharge coefficient and the cone angle of the resultant spray. A critical review is given of many of the existing analytical techniques and a new analytical theory is presented which is based upon a balance of the axial momentum across a control volume. The results of the new theory are compared with the experimental findings reported in the literature and show the need to include the swirl chamber/nozzle orifice ratio as an independent variable. Suggestions are given on how the computational methodology might be employed to determine the spray drop size for a given atomizer design and on the direction the computational work might take in order to predict a full two-phase internal flow using volume of fluid (VOF) techniques.
Supervisor: Yule, A. J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available