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.