The Production of Sprays and Mists of Uniform Drop Size by Means of Spinning Disc Type Sprayers

Abstract

Spray of almost uniform drop size is formed when liquid is fed under suitable conditions on to the centre of a rotating disc and centrifuged off the edge. This method of spraying has been studied over a wide range of variables and homogeneous clouds have been produced in the drop-size range from 3 mm. to 15 μ diameter. The size of the spray drops is given approximately by the equation d=3.8 (T/Dρ)½/ω where d=drop diameter, D=disc diameter, ω=angular velocity of disc, T=surface tension of liquid, ρ=density of liquid. The spray thus formed also contains a proportion of fine satellite drops, but their smaller distance of projection from the disc enables them to be removed from the cloud when their presence is undesirable. Relatively coarse sprays are easily produced by means of a simple electric motor-driven disc. The finer spray sizes require rotor speeds up to several thousands of revolutions per second and high speed air driven "tops" have been used for this purpose. Suitable designs of apparatus are described.