The formation of drops from viscous Newtonian liquids sprayed through fan-jet nozzles

Abstract

The effect of viscosity on the formation of spray drops of Newtonian liquids from fan-jet nozzles has been examined both photographically and quantitatively. The break-up of the liquid is governed by the flow properties of the liquid through the nozzle orifice and can be described in terms of four ranges of Reynolds numbers. Range 1 corresponds to turbulent flow in the nozzle: viscosity. has no significant effect on drop size. Range 2 is the critical region of Reynolds numbers corresponding to the transition between turbulent and laminar flow; in this region there is a tendency for the drop size to decrease with increasing viscosity. Laminar flow occurs in ranges 3 and 4 and drop size increases with increasing viscosity. In range 3 ligaments are formed at the edges of the spray sheet and they become more pronounced as the viscosity increases until, in range 4, sheet formation is suppressed and drop formation is due wholly to the break-up of ligaments. Theoretical expressions have been developed for use with static or slow-moving nozzles, to describe both the mechanism of break-up of the spray sheet in ranges 1, 2 and 3 and break-up of the edge ligaments in ranges 3 and 4. The way in which these expressions may be modified to cover rapidly moving nozzles has been discussed.