Effervescent Atomizers with Enhanced Spray Characteristics

Abstract

en

Effervescent atomizer belongs to twin fluid atomizers and is characterised by relatively simple construction. It produces fine spray even at low pressure and with low amount of atomising gas. Regardless of it there is still potential to improve their atomization characteristics such as too narrow spray cone angle of the single hole atomizer in combustion applications and a presence of large droplets in the spray border which worsen exhaust gas emissions. In this work we studied a single-hole effervescent atomizer spraying light heating oil with air as an atomising medium in the "outside-in" gas injection configuration. We focused on modification of geometry of the atomizer exit section. Two atomizers, one with moderate, and one with intense helical swirler in front of the exit orifice were designed to expand the spray cone angle by a swirl of the gas-liquid mixture. Performance of the atomizer modifications were compared with plain orifice atomizer. An experimental study of atomization process was performed on cold test bench. Swirling the mixture led to a significant increase of the spray cone angle at low gas to liquid ratio by mass. An increase of the gas mass fraction in the mixture inhibits the swirl action on the spray shape. The swirl effect diminishes with GLR rising above 15 %. An atomizer with secondary air at the exit orifice and an atomizer with secondary air beyond the exit orifice were designed to reduce droplet size in outer spray region. The secondary air at the exit orifice gave by 5 % lower overall Sauter mean diameter, using the same total amount of atomising air, compared to the plain orifice atomizer. The secondary air beyond the exit orifice did not bring any spray improvement while induced an undesirable contact of the liquid with exit port wall.

Effervescent Atomizer, Atomizer Design, Spray Cone Angle, Droplet Size

2009-07-26

University of Denver

Denver, Colorado USA

Proceedings of the 11th Triennial International Conference on Liquid Atomization and Spray Systems, Vail, Colorado USA

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