The atomization of viscoelastic fluids in flat-fan and hollow-cone spray nozzles

This article reports experimental observations of the flow kinematics and stability of thin fluid sheets produced by a series of commercially available flat-fan and hollow-cone spray nozzles for a series of viscoelastic wormlike micelle solutions. As the flow rate through the nozzle is increased, the sheets of viscoelastic fluid grow larger and eventually becoming unstable and atomizing into drops. For the sheets of water produced by the flat-fan nozzles, the fluid rims of the sheets were found to destabilize first. The addition of viscoelasticity was found to stabilize the rim while simultaneously destabilizing the internal fluid sheet. What results is a series of novel flow structures comprised of highly interconnected filaments created by the growth of multiple internal holes that develop within the fluid sheet. Increasing viscoelasticity of the test fluid was found to stabilize the thin films produced by both the flat-fan and hollow-cone spray nozzles, thereby shifting the break-up of the sheets to larger flow rates. However, beyond the critical flow rate for sheet rupture, increases to the fluid elasticity were found to alter the dynamics of the atomization of the viscoelastic fluid sheets by increasing the number and growth rate of holes in the sheet while simultaneously reducing the initiation time for sheet rupture. (C) 2007 Elsevier B.V. All rights reserved.