Browse Prior Art Database

Original Publication Date: 1977-Jun-30
Included in the Prior Art Database: 2004-Mar-29

Publishing Venue

Xerox Disclosure Journal


Rayleigh mode spraying is a well-known technique for breaking up a fluid stream into discrete, uniform-sized particles. This is accomplished by imposing a perturbation of the appro-priate wavelength onto the fluid stream. If the wavelength is in the appropriate range, the perturbation grows until the liquid stream is broken into droplets. This technique has utility in the process of converting a large mass of liquid material into discrete droplets which can be frozen to form spherical particles. Drop streams leaving the spray fixture experience viscous drag from the surrounding air which slows the droplets and may cause them to pile up and recombine, thus negating the beneficial effect of the Rayleigh method. At-tempts have been made to solve this problem by applying an electrostatic charge to the particles as they exit from the sprayer. Since like charges repel each other, the charged particles are less likely to recombine than are uncharged particles. This system is, however, satisfactory only when the number density of droplets is kept low as with a small number of or widely separated jets. A high-throughput spray fixture therefore becomes large and cumbersome, The limita-tion on droplet number density arises from the space charge field which the charged droplets establish, This space charge field causes the droplets to polarize, and the dipoles thus formed cause an attractive force between droplets which, at small droplet spacing, can be larger than the force of repul-sion due to the droplet net charge. Therefore, under the conditions of high droplet number density (high space charge field) , the process employed to reduce droplet recombination can actually cause reconibination.