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Title: An experimental study of the factors influencing the stability of liquid jets and sheets in laminar and turbulent flow
Author: Hooper, Peter Cyril
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 1960
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A study has been made of the stability and disintegration of flat sheets produced by spray nozzles at various ambient densities. For single hole fan spray nozzles it has been shown that a flat laminar sheet in vacuum conditions is stable, and that the perforations previously reported are not a fundamental property of the sheet. At higher densities the sheet is disrupted by aerodynamic waves and a theory has been developed predicting the wavelength and growth of these waves. It is shown theoretically that the form of the equations is critically dependent on the operating conditions and this has been verified by the experiments. Theoretical expressions for the size of drops produced from the sheets have also been developed. In contrast to all previous theories an increase in drop-size with increase of ambient density is predicted at high density. This prediction has been verified by experiments which showed that as the density was increased the mean drop-size initially decreased, passed through a minimum and then increased. The results from a two hole (impinging jet) fan spray nozzle did not show such good agreement with theory. The violent vibratory turbulence which occurs at the point of impact modified the disintegration of the sheet at all but the highest densities. Even in vacuum conditions the sheet still disintegrated by the growth of a wave disturbance. A study of single jets revealed some unexpected results regarding flow and stability. A new form of jet break-up has been discovered and it has been shown that laminar or turbulent flow in a tube can be obtained, at will, up to a Reynolds number of 12,000. The results of impinging two laminar or turbulent jets have shown the separate effects of stream and impact turbulence. An empirical drop-size equation has been developed for the turbulent jets which includes impingement angle as a variable.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available