Atomization and Sprays Journal of the International Institutes for Liquid Atomization and Spray Systems

ISSN for PRINT: 1045-5110

For Online Access

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1994, Volume4

Issue 2

128 pages

Issue price - $75.00

Qing-Hong Zhu
Department of Aerospace Engineering, Technion−Israel Institute of Technology, Haifa 32000, Israel

Yoram Tambour
Faculty of Aerospace Engineering, Technion—Israel Institute of Technology, Haifa 32000, Israel

Similarity solutions are presented for the dynamics of a vaporizing polydisperse spray in an isothermal flow field that is induced by a rotating disk. The host fluid, i.e., gas plus vapors, is considered to be incompressible, whereas the spatial distribution of the density of the spray varies due to droplet acceleration and droplet vaporization. The spray is introduced into the system far from the disk and is carried by the fluid flow field in the axial direction toward the disk, in the tangential direction due to the rotation of the flow, and in the radial direction along the disk due to centrifugal forces. Tambour's sectional approach is employed to describe the polydisperse spray. That is, the droplets of the spray are divided according to their size into (10) different size groups (sections), where droplets “move” from upper size sections to lower size sections due to the vaporization process. Each section is represented by a continuity equation and three momentum equations, since each droplet size section has a different velocity, which also differs from the velocity of the host fluid. Thus, for 10 sections, the spray is represented by 40 differential equations (which are intercoupled and also coupled to the host fluid flow equations), for which solutions are presented here. In the interaction of the droplets with the host gas we account for the interchange of momentum between the two phases resulting from the drag forces acting on the droplets due to the velocity lag between the droplets and the host gas. The mass of vapors added to the host gas is accounted for, but we neglect the differences in momentum between the vapors and the host gas due to differences in velocity between them. Results are presented for a polydisperse spray that is described by an initial arbitrary-size histogram. These results show the effect of droplet vaporization and acceleration on the spatial evolution in droplet size distribution and on the evolution of droplet mass fluxes in the axial, radial, and tangential directions.

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