ITEMS

modern scholarly publishers in the finest tradition

Journals

	Search

Atomization and Sprays

Journal of the International Institutes for Liquid Atomization and Spray Systems

ISSN for PRINT: 1045-5110

Institutional price:	$787.00
Issues per year:	8

Best Paper Award Selection - Editorial Board Site

2003, Volume13

136 pages

Issue price - $75.00

SIMULATION OF WATER AND OTHER NON-FUEL SPRAYS USING A NEW SPRAY MODEL

James C. Beck
Atomization and Sprays Research Group, Mechanical, Aerospace and Manufacturing Engineering Department, UMIST, Manchester, United Kingdom

A. Paul Watkins
Atomization and Sprays Research Group, Department of Mechanical, Aerospace and Manufacturing Engineering, University of Manchester Institute of Science and Technology, Manchester, U.K.

ABSTRACT

Hitherto, all polydisperse spray models have been based on discretizing the liquid flow field into groups of equally sized droplets. The work assessed here involves the implementation of a spray model [1-3] that captures the full polydisperse nature of the spray flow without using droplet size classes. The parameters used to describe the distribution of droplet sizes are the first four moments of the droplet number distribution function. Transport equations are written for the two moments which represent, per unit volume, the liquid mass and surface area, and two more moments representing the sum of the droplet radii and droplet number are approximated via use of a presumed distribution function which is allowed to vary in space and time. The velocities to be used in the two transport equations are obtained by defining moment-average quantities and constructing further transport equations for the relevant moment-average velocities. An equation for the energy of the liquid phase and standard gas-phase equations, including a k-e turbulence model, are also solved. All the equations are solved in a Eulerian framework using the finite-volume approach, and the phases are coupled through source terms. Effects such as droplet breakup and droplet—droplet collisions are also included through the use of source terms, and all the source terms are expressed in terms of the four moments of the droplet size distribution in order to find the net effect on the whole spray flow field.
In previous journal publications, the model has been qualitatively assessed by examining the predicted structures of narrow-cone, wide-angle full-cone and hollow-cone sprays, and the dependence of the results on parametric changes. Quantitative verification using experimental data has largely been confined to macro features of the sprays, such as penetration rates.
In this article the model is further assessed by examining the microstructure of the predicted sprays. Comparisons are made with experimental data on local values of drop sizes, mass fluxes, and drop velocities for wide-angle full-cone, hollow-cone, and evaporating sprays. In most cases, good agreement is achieved. The one exception to this is the mass flux distributions predicted for wide-angle full-cone water sprays. Suggestions for improvement are made to the modeling for this, and for other features of sprays.