COMPARATIVE STUDY OF TWIN-FLUID ATOMIZATION USING SONIC OR SUPERSONIC GAS JETS

Abstract

To examine the effect of sonic and supersonic gas jets on twin-fluid atomization, a comparative study has been done for two different types of atomizers, using (1) an underexpanded sonic nitrogen gas jet from a converging nozzle (SN type), and (2) an overexpanded supersonic nitrogen gas jet from a converging-diverging nozzle (CD type, with an area ratio of 3). Water is used as the atomized liquid injected through a center orifice. The Malvern diffraction sizer measured the spray Sauter mean diameter (SMD) distributions on a line-of-sight basis and a tomographic transformation of the data found the radial distribution of drop SMDs. A Buckingham-PI dimensional analysis provided an experimental correlation of the spray SMD with the radial and axial location, liquid mass flux, and the gas jet stagnation pressure. The SMD correlation showed small distinctions (approximately 7.5%) between the two different nozzle types when other injection conditions remained fixed. The stagnation pressure showed a dominance over the nozzle configuration (SN or CD type) in determining atomization. Also, a modified energy model analysis provided a single correlation for spatially averaged SMDs for both SN- and CD-type nozzles. The stagnation pressure again played a dominant role when correlating the spatially averaged drop SMDs.