Published 12 issues per year
ISSN Print: 1044-5110
ISSN Online: 1936-2684
Indexed in
EFFECT OF BUBBLE GENERATION CHARACTERISTICS ON EFFERVESCENT ATOMIZATION AT LOW GAS-LIQUID RATIO OPERATION
ABSTRACT
An experimental investigation into the performance of an effervescent atomizer operated with two different styles of air injectors during low gas-liquid ratio (GLR) operation is discussed. A typical multihole air supply tube and an injector that utilizes a porous media for gas injection are investigated. A preliminary study visualized the two-phase flow within the mixing chamber and the atomization mechanism at the nozzle exit to identify characteristic features of the two-phase flow. A shadowgraph droplet analyzer has also been applied to quantitatively compare the spray performance of the two atomizers in terms of droplet size distribution, droplet Sauter mean diameter (SMD), and the number of large droplets and ligaments within the spray field. The liquid breakup mechanism in the two atomizer configurations has also been quantitatively compared using shadowgraphy in the vicinity of the exit nozzle. The comparison demonstrated that the porous media air injector generates a higher number of smaller bubbles into the atomizer mixing chamber and consequently, a relatively constant GLR into the atomizer exit nozzle. The multihole injection generates large gas bubbles that leads to alternating liquid and gas slugs at the nozzle exit. This generates unsteadiness in the spray and the formation of large ligaments and droplets. The spray field of the porous media air injector, however, has a more steady spray behavior and generates a lower number of large droplets and ligaments. This indicates that bubble size relative to the exit nozzle size has an important impact on spray properties at low-GLR conditions.
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