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Atomization and Sprays
Импакт фактор: 1.737 5-летний Импакт фактор: 1.518 SJR: 0.814 SNIP: 1.18 CiteScore™: 2.2

ISSN Печать: 1044-5110
ISSN Онлайн: 1936-2684

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Atomization and Sprays

DOI: 10.1615/AtomizSpr.v6.i2.10
pages 127-143

UNSTEADY AND QUASI-STEADY VAPORIZATION OF SPHERICAL DROPLET CLOUDS

Martin Sichel
Department of Aerospace Engineering, The University of Michigan, Ann Arbor, Michigan 48109, USA
Muh Hsiung Yang
Chung Shan Institute of Science and Technology, Lungtan, Taoyuan, Taiwan 325, Republic of China

Краткое описание

Group phenomena for droplets in a spray have often been analyzed on the basis of the quasi-steady assumption even though this assumption has not been completely justified. In this article the applicability of the quasi-steady assumption to the vaporization of spherical droplet clouds is first analyzed qualitatively by considering the magnitudes of appropriate characteristic scales. Then the governing equations for the unsteady vaporization of a droplet cloud are formulated and solved by numerical methods. The numerical results indicate that cloud vaporization is inherently unsteady and consistent with the analysis of characteristic scales. The unsteady vaporization of saturated clouds nearly follows a "D law," where D refers to the cloud diameter, rather than the well-known "D2 law" for single droplet vaporization and combustion. Further, it is found that saturation conditions within the cloud cannot be uniquely determined as shown by the quasi-steady theory. However, the quasi-steady theory still provides a good prediction of cloud lifetime if both of the following two conditions are satisfied: (1) droplet mass loading ratio О (1); (2) the existence of a thin vaporization layer or wave at the cloud edge.


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