Spray unsteadiness in coaxial airblast atomizers

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:442729

Hardalupas, Y; Tsai, R F; Whitelaw, J H ^[1]

---

1. Imperial Coll. of Science, Technology and Medicine, London (United Kingdom). Mechanical Engineering Dept.

Experiments have been performed with two coaxial atomizers, the first with an annular stream of air surrounding a central jet of water and the second a commercial airblast atomizer with air swirl. They quantify the deterministic unsteadiness of the droplet flow caused by the break-up process in terms of the mean and temporal fluctuations of the droplet surface area and provide links between atomizing air and liquid flow conditions and the amplitude of the droplet flow unsteadiness with distance from the nozzle exit. Time dependent measurements of droplet surface area in the spray were obtained by image processing of high speed photographs to detect the temporal fluctuations of the attenuation of the incident light and by a Mie scattering technique to detect the intensity of the light scattered by droplets illuminated by a laser sheet. Mie scattering was preferred, because of improved measurement accuracy and lower cost. The spray unsteadiness due to the break-up process was quantified in terms of the spectrum of the energy of the fluctuations of the droplet surface area within a frequency range associated with the break-up process. With the coaxial atomizer. the energy of the deterministic unsteadiness varied between 50% and 65% of the total energy of the spectrum and remained in the droplet flow at least up to 150 liquid jet diameters downstream of the break-up region and its energy increased with the reduction of the air or liquid flowrates, although higher energy was correlated with faster attenuation with the downstream distance from the exit plane, caused by the redistribution of droplets by the gas flow turbulence.

• Sponsoring Organization: Commission of the European Communities, Brussels (Belgium)
• OSTI ID: 442729
• Report Number(s): CONF-961105--; ISBN 0-7918-1523-4
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
ATOMIZATION
DIAGNOSTIC TECHNIQUES
DROPLETS
FLUID MECHANICS
FUEL INJECTION SYSTEMS
LIQUID FUELS
SURFACE AREA