Effect of liquid preheating on high-velocity airblast atomization: From water to crude rapeseed oil

• Published in: Experimental thermal and fluid science 2019-04, Vol.102, p.137-151
• Main Authors: Urbán, András, Malý, Milan, Józsa, Viktor, Jedelský, Jan
• Format: Article
• Language: English
• Subjects: Airblast atomizer; Atmospheric conditions; Atmospheric correction; Atmospheric models; Atomizing; Brassica napus; Constraining; Crude oil; Droplets; Health care; Heating; Kinematic viscosity; Kinematics; Light heating oil; Liquids; Oil; Oilseeds; PDA; Preheating; Rapeseed; Rapeseed oil; SMD; Spray characteristics; Surface tension; Temperature; Velocity; Viscosity; Weber number
• ISSN: 0894-1777; 1879-2286
• DOI: 10.1016/j.expthermflusci.2018.11.006

•Airblast atomization was investigated in a wide range of dimensionless parameters.•Above the value of limiting viscosity, the viscosity affects the atomization process.•The spray SMD is governed by the Weber and Ohnesorge numbers.•Liquid preheating temperature linearly affects the coefficient of Weber number.•Liquid viscosity on the power of −0.5 affects the coefficient of Ohnesorge number. Airblast atomization is a suitable model platform to understand atomization physics since the atomizer geometry has an insignificant influence on the spray formation. Besides its theoretical relevance, this configuration is used in several practical applications ranging from healthcare to combustion. Presently, a plain-jet airblast atomizer has been investigated experimentally under atmospheric conditions at various atomizing pressures and liquid preheating temperatures. To cover a wide range of liquids by viscosity and surface tension, water, diesel oil, light heating oil, and crude rapeseed oil were atomized to evaluate the droplet size-velocity correlations when the spray is fully developed. Increasing the temperature of high-viscosity liquids prior to atomization improves the spray characteristics until their kinematic viscosity decreases to a certain value that is newly introduced as a limiting viscosity. Further preheating has a marginal effect on droplet size-velocity plots, and the spray becomes more homogeneous. Several SMD-estimating formulae were analyzed and improved to consider the effect of liquid preheating and to extend their range of validity. When the kinematic viscosity exceeded the limiting viscosity, the part containing the Weber number was corrected linearly by the preheating temperature. The coefficient of the Ohnesorge number was corrected by the inverse of the kinematic viscosity, without considering the limiting viscosity. The above results help to correct the SMD of atmospheric measurements to elevated liquid temperatures and to contribute to advanced atomization models for numerical software.