Primary Break-up of a Viscous Liquid Jet in a Cross Airflow

Based on the linear stability analysis, a mathematical model for the stability of a viscous liquid jet in a coaxial twisting compressible airflow has been developed. It takes into account the twist and compressibility of the surrounding airflow, the viscosity of the liquid jet, and the cavitation bubbles within the liquid jet. Then, the effects of aerodynamics caused by the gas–liquid velocity difference on the jet stability are analyzed. The results show that under the airflow ejecting effect, the jet instability decreases first and then increases with the increase of the airflow axial velocity. When the gas–liquid velocity ratio A = 1, the jet is the most stable. When the gas–liquid velocity ratio A > 2, this is meaningful for the jet breakup compared with A = 0 (no air axial velocity). When the surrounding airflow swirls, the airflow rotation strength E will change the jet dominant mode. E has a stabilizing effect on the liquid jet under the axisymmetric mode, while E is conducive to jet instability under the asymmetry mode. The maximum disturbance growth rate of the liquid jet also decreases first and then increases with the increase of E. The liquid jet is the most stable when E = 0.65, and the jet starts to become more easier to breakup when E = 0.8425 compared with E = 0 (no swirling air). When the surrounding airflow twists (air moves in both axial and circumferential directions), given the axial velocity to change the circumferential velocity of the surrounding airflow, it is not conducive to the jet breakup, regardless of the axisymmetric disturbance or asymmetry disturbance.

Download Full-text

Linear Instability Analysis of an Annular Swirling Viscous Liquid Jet

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.66-68.1556 ◽

2011 ◽

Vol 66-68 ◽

pp. 1556-1561 ◽

Cited By ~ 1

Author(s):

Kai Yan ◽

Ming Lv ◽

Zhi Ning ◽

Yun Chao Song

Keyword(s):

Viscous Liquid ◽

Liquid Velocity ◽

Aerodynamic Force ◽

Numerical Procedure ◽

Liquid Sheet ◽

Linear Instability ◽

Viscous Force ◽

Liquid Jet ◽

Instability Analysis ◽

Linear Instability Analysis

A three-dimensional linear instability analysis was carried out for an annular swirling viscous liquid jet with solid vortex swirl velocity profile. An analytical form of dispersion relation was derived and then solved by a direct numerical procedure. A parametric study was performed to explore the instability mechanisms that affect the maximum spatial growth rate. It is observed that the liquid swirl enhances the breakup of liquid sheet. The surface tension stabilizes the jet in the low velocity regime. The aerodynamic force intensifies the developing of disturbance and makes the jet unstable. Liquid viscous force holds back the growing of disturbance and the makes the jet stable, especially in high liquid velocity regime.

Download Full-text

Three-dimensional simulation of primary break-up in a close-coupled atomizer

Applied Physics A ◽

10.1007/s00339-012-6966-7 ◽

2012 ◽

Vol 108 (4) ◽

pp. 783-792 ◽

Cited By ~ 6

Author(s):

N. Zeoli ◽

H. Tabbara ◽

S. Gu

Keyword(s):

Three Dimensional ◽

Break Up ◽

Dimensional Simulation ◽

Primary Break

Download Full-text

Numerical Jet Atomization: Part II — Modeling Information and Comparison With DNS Results

Volume 1: Symposia, Parts A and B ◽

10.1115/fedsm2006-98166 ◽

2006 ◽

Cited By ~ 3

Author(s):

P. A. Beau ◽

T. Me´nard ◽

R. Lebas ◽

A. Berlemont ◽

S. Tanguy ◽

...

Keyword(s):

Level Set ◽

Volume Fraction ◽

Computing Time ◽

Mass Conservation ◽

Liquid Volume ◽

Liquid Density ◽

Wide Range ◽

The Mean ◽

Break Up ◽

Primary Break

The main objective of our work is to develop direct numerical simulation tools for the primary break up of a jet. Results can help to determine closure relation in the ELSA model [1] which is based on a single-phase Eulerian model and on the transport equation for the mean liquid/gas interface density in turbulent flows. DNS simulations are carried out to obtain statistical information in the dense zone of the spray where nearly no experimental data are available. The numerical method should describe the interface motion precisely, handle jump conditions at the interface without artificial smoothing, and respect mass conservation. We develop a 3D code [2], where interface tracking is ensured by Level Set method, Ghost Fluid Method [3] is used to capture accurately sharp discontinuities, and coupling between Level Set and VOF methods is used for mass conservation [4]. Turbulent inflow boundary conditions are generated through correlated random velocities with a prescribed length scale. Specific care has been devoted to improve computing time with MPI parallelization. The numerical methods have been applied to investigate physical processes that are involved in the primary break up of an atomizing jet. The chosen configuration is close as possible of Diesel injection (Diameter D = 0.1 mm, Velocity = 100m/s, Liquid density = 696kg/m3, Gas density = 25kg/m3). Typical results will be presented. From the injector nozzle, the turbulence initiates some perturbations on the liquid surface, that are enhanced by the mean shear between the liquid jet and the surrounding air. The interface becomes very wrinkled and some break-up is initiated. The induced liquid parcels show a wide range of shapes. Statistics are carried out and results will be provided for liquid volume fraction, liquid/gas interface density, and turbulent correlations.

Download Full-text