MEASUREMENTS AND PREDICTIONS OF A LIQUID SPRAY FROM AN AIR-ASSIST NOZZLE

Droplet size and velocity and gas velocity were measured in a water spray using a twocomponent Phase/Doppler Particle Analyzer. A complete set of measurements was obtained at axial locations from 5 to 50 cm downstream of the nozzle. The nozzle used was a simple axisymmetric air-assist nozzle. The sprays produced, using the atomizer, were extremely fine. Sauter mean diameters were less than 20 _m at all locations. Measurements were obtained for droplets ranging from l to 50 /._. The gas phase was seeded with micron sized droplets, and droplets having diameters of 1.4 _ and less were used to represent gas-phase properties. _easurements were compared with predictions from a multi-phase computer model. Initial conditions for the model were taken from measurements at 5 cmdownstream. Predictions for both the gas phase and the droplets showed relatively good agreement with the measurements. Nomenclature a acceleration of gravity Ci Cd constants in turbulence model drag coefficient d nozzle diameter dp k droplet diameter turbulence kinetic energy Le dissipation length scale of eddy mp droplet mass n number of droplet groups n i number of droplets per unit time in group i Re Reynolds number r radial distance *Aerospace Engineer, member AIAA. *'NRC Research Associate, on leave from Technion, Israel Institute of Technology, Haifa, Israel_ member AIAA. Associate professor, Dept. of Mechanical Engineering, member AIAA. _'Graduate student, Dept. of Mechanical Engineering. S source term Sp source term due to droplets t time t e eddy lifetime u axial velocity Vj volume of computational cell ) v radial velocity w angular velocity x axial distance Xp droplet position vector e rate of dissipation of turbulence kinetic energy p viscosity _t turbulent viscosity p density _i turbulent Prandtl/Schmidt number 0 generic property qXp relative path length of droplets in an eddy Vtp droplet residence time in an eddy Subscri_: c centerIine quantity o initial axial location p droplet property = ambient condition Superscripts: ( )' fluctuating quantity (-) time averaged value (*) vector quantity (~) Favre averaged value Copyright © 1990 by the American Institute of Aeronautics and Astronautics, Inc. No copyright is asserted in the United States under Title 17, U.S. Code. The U.S. Government has a royalty-free license to exercise all rights under the copyright claimed herein for Governmental purposes. All other rights are re_rved by the copyright owner.