CSE Seminar
SPEAKER: Sadegh Dabiri, University of California, Irvine
TITLE:
Effects of Cavitation on High-Pressure Atomization
DATE: Wednesday, November 12, 2008
TIME: 12:00 Noon
PLACE: 2240 DCL
1304 W. Springfield Ave., Urbana, IL
ABSTRACT
Improved knowledge of liquid jet breakup is necessary for advancing
propulsion systems. Control of fuel injection processes implies better
control of droplet size distribution and of spray penetration, and
therefore, better control of effciency and emissions. Experiments show
that occurrence of cavitation in high-pressure liquid injectors leads
to a better atomization of the emerged jet. In order to study these
phenomena in detail, numerical simulation of high-pressure atomizers
and breakup of liquid jets is performed. Cavitation in the orifice of
high-pressure fuel injectors is modeled and its contribution to
disintegration of jets is studied. Specific attention is paid to the
interaction between shear layers and cavitation bubbles, due to the
fact that cavitation inception occurs behind the sharp corners, where
strong shear is present.
This study has resulted in identication of two mechanisms that may be
responsible for increase of disturbances in the flow due to the
collapse of cavitation bubbles. One is by creation and impingement of
re-entrant jets, and the other is by cavitation induced roll-up of the
vortex sheets. These disturbances, caused by collapse of cavitation
bubbles, later will trigger the instabilities in the emerged jet and
cause a shorter breakup distance. Moreover, the new criterion of
cavitation based on the total stress in the liquids is compared with
the traditional pressure criterion.