The structure of sprays formed by a two-phase flow in an effervescent atomizer is investigated. The spray structure is seen to be distinctly different for bubbly, slug, and annular flows. While the break-up of gas bubbles at the edge of the spray cone contributes to atomization in the bubbly flow regime, the expansion of the core bubbles causes atomization in the slug flow regime. The wave mode of atomization is seen in the annular flow regime. The influence of gas to liquid ratios and injection pressures on spray characteristics is discussed. Copyright ©2007 Begell House, Inc.

K. Ramamurthi

Atomization

BUBBLE CHAMBERS

CONES

flow rate

flow visualization

Two phase flow

Annular flows

SPRAY STRUCTURE

ATOMIZERS

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Flow Visualization and Image Processing

Gas bubbles introduced into a liquid in the mixing chamber help to break up the liquid into fine droplets on being expanded to the ambient pressure. The passage of gas bubbles through the orifice of the nozzle requires that the size of the bubbles be much smaller than the diameter of the orifice. In the present work, the effectiveness of 20. kHz ultrasound to increase number density of fine bubbles within the mixing chamber of an effervescent atomizer by breaking up bubbles introduced in it by an aerator was investigated. Bubbles of initial size in the range of 5-10. mm were shown to get disintegrated into clusters of micron and sub-micron sized bubbles. A fine spray was produced in the presence of ultrasound at a gas-to-liquid mass flowrate ratio (GLR) of 0.063%. The half-cone angle of spray was in the range of 6-10°, which compares favorably with conventional atomizers. The experimental findings of bubble breakup were theoretically modeled by the Rayleigh-Plesset equation. The results of the model indicate that bubbles having initial radius less than 3. mm undergo growth and subsequent disintegration at 20. kHz for the given acoustic pressure of 0.3. MPa. © 2011 Elsevier B.V.

Chemical Engineering and Processing: Process Intensification

Effect of ultrasound on bubble breakup within the mixing chamber of an effervescent atomizer

Flow visualization of sprays formed by bubbly, slug, and annular flows in an effervescent atomizer

Journal	Journal of Flow Visualization and Image Processing
ISSN	10653090
Open Access	No