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ICLASS 94<br>Proceedings of the Sixth International Conference on Liquid Atomization and Spray Systems

ISBN:
978-1-56700-019-1 (Print)
978-1-56700-445-5 (Online)

ATOMIZATION OF NON-NEWTONIAN LIQUIDS

Adel Mansour
Spray Systems Technology Center, Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA

Norman Chigier
Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA

Abstract

The changes in the physical processes of atomization as a result of adding a high molecular weight polymer in low concentrations to liquid have been studied. Both Newtonian and non-Newtonian liquids were investigated with particular emphasis on the non-Newtonian rheological characteristics. Non-Newtonian viscosities were measured over five decades of shear rates γ for 12 solutions of polymeric materials. By using the die-swell technique, the first normal stress difference N1 was determined for all solutions. It was found that viscoelastic liquids are much more difficult to atomize than viscoinelastic liquids. Viscoinelastic liquids showed a breakup behavior similar to that of water sprays. Viscoelastic materials showed remarkably different breakup patterns. The ligaments were seen to undergo a very large stretching motion before they breakup, resulting in long threads of liquid attached to droplets. The normal stresses developed in viscoelastic materials are much higher than their associated shear stresses. Consequently, the development of the large normal stresses appears to be the most important rheological mechanism that inhibits breakup. For shear thinning viscoinelastic materials it was found that the atomization quality is closely related to the apparent viscosity of the fluid in the limit of infinite shear rates (η). The functional dependence of the SMD on η is: SMD α η0.43 .