Begell House Inc.
Atomization and Sprays
AAS
1044-5110
28
2
2018
PENETRATION OF AERATED SUSPENSION SPRAY IN A GASEOUS CROSSFLOW
91-110
Amr
Saleh
Department of Mechanical and Industrial Engineering, Concordia University,
Montreal, Quebec, Canada
Ghobad
Amini
Department of Mechanical and Industrial Engineering, Concordia University,
Montreal, Quebec, Canada
Ali
Dolatabadi
Department of Mechanical and Industrial Engineering, Concordia University,
Montreal, Quebec, Canada
The breakup of a suspension in the atomization process differs from that of a pure liquid by the influence of the suspended particles on the fragmentation kinetics. In the suspension spraying process, different types of atomizers are used but clogging problems can occur due to the suspension properties. Effervescent atomizers have shown to be a good alternative to the conventional atomizers to
solve clogging issues when liquids with a large variety of viscosity and density such as suspensions are atomized. In this study, effervescent atomization of suspensions in a crossflow of air is investigated experimentally. The tests have been performed at different liquid-to-air momentum flux ratios and different gas-to-liquid mass ratios. Different types of suspended solid particles, hydrophilic and
hydrophobic, at different concentrations are tested. Shadowgraphy and image processing have been employed in order to capture the penetration height of the spray. New correlations have been developed to predict the spray penetration height of suspensions in crossflow for nonaerated and aerated liquid jets.
FLASH-BOILING INITIALIZATION FOR SPRAY SIMULATIONS BASED ON PARAMETRIC STUDIES
111-140
Sampath K.
Rachakonda
University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA
Yue
Wang
ANSYS Inc
David P.
Schmidt
Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA
Nondimensional groups were identified and correlations were established to initialize flash-boiling spray for use in Lagrangian/Eulerian spray simulations. The objective was realized through CFD simulations with nonequilibrium interphase heat transfer and an Eulerian-Eulerian spray model. Parametric studies were carried out on 2D axisymmetric straight and stepped nozzles to study
the effects of geometric and operating conditions on the near-nozzle spray. The effects of the inlet corner radius, nozzle diameter, counter-bore diameter and the inner nozzle length were assessed along with the effects of varying injection and ambient pressures and the fuel temperature as part of this study. The influence of these parameters on the coefficient of discharge, the spray-cone angle, and the Sauter mean diameter (SMD) were analyzed both qualitatively and quantitatively. Results indicate that the inlet corner radius dominates the coefficient of discharge; the time available for the fuel to vaporize determines the magnitude of the spray-cone angle. The SMD is dominated by the
extent of the fuel superheat, defined as a ratio of the ambient to the saturation pressure of the fuel.
The established correlations were incorporated using a user-defined function as a means to initiate flash-boiling Lagrangian spray. The simulated downstream spray angle and SMD were validated against experimental results.
FINITE PARTICLE METHODS FOR COMPUTING INTERFACIAL CURVATURE IN VOLUME OF FLUID SIMULATIONS
141-160
Everett A.
Wenzel
Department of Mechanical Engineering, University of Minnesota, 111 Church
Street SE, Minneapolis, Minnesota 55455-0111, USA
Sean C.
Garrick
Department of Mechanical Engineering, University of Minnesota, 111 Church
Street SE, Minneapolis, Minnesota 55455-0111, USA
The volume of fluid (VOF) method is a useful tool for multiphase flow simulation. However, smallscale
interfacial structures introduce significant computational challenges. One difficulty is determining interface curvature at low resolutions—a requirement in turbulent spray simulation. In this work we evaluate two finite particle schemes for computing curvature of poorly resolved interfaces in the context of VOF simulations. Curvature is computed from the convolved VOF in the first scheme and directly from the VOF in the second scheme. Both cell-centered and interface-centered calculations are considered in the first scheme, while only cell-centered calculations are considered in the second scheme. The methods are evaluated via the L2 and L∞ error norms corresponding to the curvature of spheres. Results yield L2 errors less than 1% and L∞ errors less than 3% for nearly all resolutions considered. Additionally, a hybrid implementation of the first scheme demonstrates greater accuracy than a contemporary variant of the height function method for resolutions relevant to spray simulations. The results suggest the finite particle method to be a valuable tool for computing interfacial curvature in flows with a poorly resolved dispersed phase.
EFFECT OF FLOW RATE AND ELECTRIC FIELD ON ELECTROSPRAY DIFFUSION FLAME OF ETHANOL AND BUTANOL
161-178
S.
Jowkar
Department of Aerospace Engineering, Sharif University of Technology, Tehran,
Iran
Mohammad Reza
Morad
Department of Aerospace Engineering, Sharif University of Technology, Tehran,
Iran
S.
Ghorbani
Department of Aerospace Engineering, Sharif University of Technology, Tehran,
Iran
Diffusion flame from electrospray of liquid ethanol and butanol is investigated experimentally. Stable flames were observed at two distinct modes recognized at different flow rates, applied voltages, and distances between the nozzle and counter electrode. The first mode occurred at minimum voltages in which individual larger droplets are dominantly generated. The second mode at higher voltages corresponds to multijets, which produce finer distribution of droplets. Using flame-imaging analysis, flammability margins are introduced and flame lengths are measured versus nondimensional parameters for both fuels and modes of spraying. The fluctuation of the flames is characterized and
the frequency of the fluctuations is measured for butanol fuel and both modes of electrospray as well.
LARGE EDDY SIMULATION OF POLYDISPERSE PARTICLE DEPOSITION IN AN IDEALIZED MOUTH-THROAT
179-193
X. G.
Cui
Joint Bioenergy Institute, Lawrence Berkeley National Laboratory, Berkeley,
California, USA
E. M.
Littringer
Research Center Pharmaceutical Engineering GmbH, Graz, Austria
N. A.
Urbanetz
Daiichi Sankyo Europe GmbH, Munich, Germany
Eva
Gutheil
Interdisciplinary Center for Scientific Computing, Heidelberg University, Heidelberg, 69120, Germany
The present study investigates the polydisperse particle deposition in an idealized mouth-throat. The scope is the identification of the properties of polydisperse particle deposition in the human upper airways with respect to the aerosol drug delivery to the lung. Both one-way and two-way
coupling between the gas and the particle phases are implemented to model the two-phase flow. Large eddy simulation (LES) with the Smagorinsky subgrid model is used to simulate the laminar-transitional-turbulent gas flow, and themodel is combined with Lagrangian equations to describe the particle motion. User-defined solvers based on the open-source software OpenFOAM are developed to solve the governing equations. An experimental particle size distribution from a dry powder inhaler with 200 μ;g dosage corresponding to one actuation is used. The numerical results show that the polydisperse particle deposition in the human mouth-throat is dominated by the particle size
distribution and the geometric characteristics of the idealized mouth-throat. Moreover, simulations with two different monodisperse aerosols with different particle sizes are used for comparison: the representative Sauter mean diameter and the mass median diameter of the reference polydisperse particle size distribution. The particle deposition efficiency of the polydisperse particle distribution is much higher than that of both monodisperse particle distributions, which cannot represent the
polydisperse particle deposition characteristics. The particle deposition efficiency is higher using
one-way coupling compared to two-way coupling for the polydisperse particle size distribution. It is concluded that a representative polydisperse particle distribution should be used to simulate the aerosol drug deposition in the human respiratory system using two-way coupling.