Experiments in Fluids

, Volume 45, Issue 3, pp 371–422

On the experimental investigation on primary atomization of liquid streams

Review Article

DOI: 10.1007/s00348-008-0526-0

Cite this article as:
Dumouchel, C. Exp Fluids (2008) 45: 371. doi:10.1007/s00348-008-0526-0

Abstract

The production of a liquid spray can be summarized as the succession of the following three steps; the liquid flow ejection, the primary breakup mechanism and the secondary breakup mechanism. The intermediate step—the primary breakup mechanism—covers the early liquid flow deformation down to the production of the first isolated liquid fragments. This step is very important and requires to be fully understood since it constitutes the link between the flow issuing from the atomizer and the final spray. This paper reviews the experimental investigations dedicated to this early atomization step. Several situations are considered: cylindrical liquid jets, flat liquid sheets, air-assisted cylindrical liquid jets and air-assisted flat liquid sheets. Each fluid stream adopts several atomization regimes according to the operating conditions. These regimes as well as the significant parameters they depend on are listed. The main instability mechanisms, which control primary breakup processes, are rather well described. This review points out the internal geometrical nozzle characteristics and internal flow details that influence the atomization mechanisms. The contributions of these characteristics, which require further investigations to be fully identified and quantified, are believed to be the main reason of experimental discrepancies and explain a lack of universal primary breakup regime categorizations.

List of symbols

a

liquid jet radius (mm)

A

spray angle parameter

AL, AG

fluid flow exit section area (mm2)

d

nozzle diameter (mm)

D

drop diameter (μm)

D32

Sauter mean diameter (μm)

D43

arithmetic mean diameter of the volume-based drop-size distribution (μm)

f

undulation frequency (Hz)

g

gravitational acceleration (m/s2)

k

wave number (m−1)

K

liquid sheet thickness parameter (cm2)

L

nozzle length (mm)

LBU

breakup length (mm)

LC

liquid jet core length (mm)

Lp

boundary-layer length (mm)

LPC

liquid jet potential core length (mm)

LPP

liquid presence probability

m

mass flux ratio

M

momentum flux ratio

Oh

Ohnesorge number

Pamb

gas ambient pressure (MPa)

r

radial coordinate (mm)

rb

radial position of a flat sheet breakup (mm)

Re

Reynolds number

T

Taylor number

t

time (s)

tBU

breakup time (s)

tL, tG

liquid and gas flow thickness (mm)

U

average velocity (m/s)

ULC

critical liquid jet velocity (m/s)

UL0

minimum liquid jet velocity (m/s)

We

Weber number

WeGc

critical gaseous Weber number

WeR

relative gaseous Weber number

x

axial distance from nozzle (mm)

Greek symbols

δ

air vorticity thickness (mm)

ΔPi

injection pressure (MPa)

ρ

fluid density (kg/m3)

λ

wavelength (cm)

Λ

radial spatial integral length of turbulence (μm)

μ

fluid dynamic viscosity (kg/ms)

σ

surface tension (N/m)

η

interface displacement (mm)

η0

initial interface displacement (μm)

ω

pulsation (s−1)

Subscripts

L

related to the liquid flow

G

related to the gas flow

max

maximum

opt

optimum

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  1. 1.CNRS UMR 6614–CORIAUniversité de RouenSaint Etienne du RouvrayFrance