Atomization of Liquid by Means of a Rotating Nozzle : 4th Report, Effects of Physical Properties of Liquid on Droplet Sizes

Abstract

In order to develop the results obtained in the preveous reports in which only the water was used as the spraying liquid, the experiments were carried out on the solutions of glycerine and ethyl alcohol with viscosity ranging from 10 to 130 mP and with surface tension from 30 to 70 dyne/cm. The following conclusions were drawn : (1) When the rotating speed is low enough to form a continuous liquid jet, an increase in liquid viscosity up to μ_c=20∼40mP causes a decrease in the mean droplet diameter. The reason lies in an elongation of the continuous liquid jet. (2) In the state of spray the effect of viscosity on the droplet size becomes negligibly small. (3) The sizes of droplets can be reduced by decreasing surface tension in the whole range of the speed of rotation. (4) An empirical formula giving Sauter mean diameter d (μ) was derived in the spray region as follows : d=4.32×10³ (σ/ρ) ^0.25/υ^1.15 where σ=surface tension (dyn/cm), ρ=density (g/cm³) and υ=resultant velocity of the peripheral and the discharge velocitiy (m/s). (5) As shown in Fig. 15, the relation between the maximum diameter d_max and the mean diameter d, that is, d_max≒2d is not influenced by the physical properties of the liquids.