Research of the Primary Breakup of a Planar Liquid Sheet Produced by an Air-Blast Atomizer

2014 ◽  
Author(s):  
Hua Zhou ◽  
Chia-Fon Lee ◽  
Shi-jin Shuai
Keyword(s):  
Liquid Sheet ◽  
Air Blast ◽  
Primary Breakup

Numerical Investigation of the Unstable Wave on a Planar Liquid Sheet Produced by an Air-Blast Atomizer

2014 ◽  
Author(s):  
Hua Zhou ◽  
Chia-fon F. Lee ◽  
Timothy H. Lee
Keyword(s):  
Relative Motion ◽  
Internal Flow ◽  
Particle Method ◽  
Liquid Sheet ◽  
Shear Instability ◽  
Unstable Wave ◽  
Air Blast ◽  
Primary Breakup ◽  
Specific Frequency ◽  
Fluid Particles

The unstable surface wave on a liquid sheet produced by an air-blast atomizer during primary breakup process was investigated by numerical simulation. The results of simulation were verified by comparison of primary breakup time and breakup length with accessible experimental data reported in technical papers. The frequency characteristics of stream-wise unstable wave at different axial locations were investigated by applying Discrete Fourier Transform (DFT). It was found that when there is no disturbance induced by internal flow, there is no specific frequency which is favored by shear instability near the nozzle exit, and the characteristic frequency of the dominant wave decreases along stream-wise direction due to the decrease of relative velocity. By applying Discrete Particle Method (DPM), the motion of fluid particles inside the liquid sheet was able to be tracked, and the Lagrangian characteristics of fluid particles can be partially revealed. The growth of stream-wise unstable wave was found to possess strong spatial characteristics by investigating the pathlines and streaklines of fluid particles. A rough evaluation for the stream-wise speed of fluid particles and the propagation velocity of unstable wave showed that fluid particles move faster than unstable wave in stream-wise direction, thus, relative motion exists between fluid particles and stream-wise wave. This relative motion could lead to huge acceleration of fluid particles, which could trigger Rayleigh-Taylor (RT) instability to induce transverse disintegration. Some complex behaviors of fluid particles inside the liquid sheet were observed, e.g. eddy-like structures formed by fluid particles.

scholarly journals Progress in the Smoothed Particle Hydrodynamics Method to Simulate and Post-process Numerical Simulations of Annular Airblast Atomizers

2020 ◽  
Vol 105 (4) ◽  
pp. 1119-1147
Author(s):  
G. Chaussonnet ◽  
T. Dauch ◽  
M. Keller ◽  
M. Okraschevski ◽  
C. Ates ◽  
...  
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Flux Ratio ◽  
Liquid Sheet ◽  
Sph Method ◽  
Post Process ◽  
Finite Time Lyapunov Exponent ◽  
Fragmentation Spectrum ◽  
Particle Hydrodynamics ◽  
Primary Breakup ◽  
Smoothed Particle

AbstractThis paper illustrates recent progresses in the development of the smoothed particle hydrodynamics (SPH) method to simulate and post-process liquid spray generation. The simulation of a generic annular airblast atomizer is presented, in which a liquid sheet is fragmented by two concentric counter swirling air streams. The accent is put on how the SPH method can bridge the gap between the CAD geometry of a nozzle and its characterization, in terms of spray characteristics and dynamics. In addition, the Lagrangian nature of the SPH method allows to extract additional data to give further insight in the spraying process. First, the sequential breakup events can be tracked from one large liquid blob to very fine stable droplets. This is herein called the tree of fragmentation. From this tree of fragmentation, abstract quantities can be drawn such as the breakup activity and the fragmentation spectrum. Second, the Lagrangian coherent structures in the turbulent flow can be determined easily with the finite-time Lyapunov exponent (FTLE). The extraction of the FTLE is particularly feasible in the SPH framework. Finally, it is pointed out that there is no universal and ultimate non-dimensional number that can characterize airblast primary breakup. Depending on the field of interest, a non-dimensional number (e.g. Weber number) might be more appropriate than another one (e.g. momentum flux ratio) to characterize the regime, and vice versa.

The Effect of Crosswind Velocity on the Spray Drift of Flat Fan Nozzle

2019 ◽  
Author(s):  
S. Raza ◽  
K. A. Sallam ◽  
S. L. Post
Keyword(s):  
Liquid Sheet ◽  
Nozzle Geometry ◽  
Target Area ◽  
Spray Drift ◽  
Agricultural Industry ◽  
Injection Angle ◽  
Drift Flux ◽  
Breakup Mechanism ◽  
Primary Breakup ◽  
Sheet Breakup

Abstract The objective of this research project is to eliminate the spray drift caused by crosswind. Spray drift is an important problem for the agricultural industry. Some herbicides (e.g. Dicamba) can cause serious damage if it drifts to nearby crops that are not genetically modified to withstand those herbicides. Our hypothesis is that the nozzle geometry and the injection angle can be actively/passively controlled to compensate for the crosswind velocity and effectively deliver the herbicides to the target area. The measurements include the breakup regime transitions, the droplet sizes, and the droplets trajectory as function of the wind speed and the injection angle. The current results show that the crosswind modifies the primary breakup mechanism from sheet breakup regime (i.e. thinning and fragmentation of the liquid sheet into ligaments) to bag breakup regime (i.e. the formation bags along the downstream side of liquid sheet) resulting in smaller drop sizes and an increased drift flux. Techniques to eliminate the bag breakup regime are presented.

Numerical study of the primary breakup of a plane liquid sheet with co-flowing air streams

PAMM ◽  
2012 ◽  
Vol 12 (1) ◽  
pp. 513-514
Author(s):  
Suresh kumar Kannan ◽  
Bernhard Peters
Keyword(s):  
Numerical Study ◽  
Liquid Sheet ◽  
Primary Breakup ◽  
Air Streams

A Functional Correlation for the Primary Breakup Processes of Liquid Sheets Emerging From Air-Assist Atomizers

2006 ◽  
Vol 129 (2) ◽  
pp. 188-193 ◽  
Author(s):  
V. Sivadas ◽  
M. V. Heitor ◽  
Rui Fernandes
Keyword(s):  
High Speed ◽  
Imaging Techniques ◽  
Flux Ratio ◽  
Liquid Sheet ◽  
Spray Angle ◽  
High Speed Imaging ◽  
Liquid Sheets ◽  
Primary Breakup ◽  
Sheet Breakup ◽  
The Stability

The study aims to highlight a general relationship between the characteristic variables of liquid sheet breakup and the principal forces of the flow domain. To accomplish this objective, an experimental investigation on air-assisted liquid sheets was carried out for a range of liquid-to-air velocities. The associated spray angle, breakup frequency, and breakup length were measured by exploiting high-speed imaging techniques. The results demonstrate that, when the stability variables are related to the liquid–air momentum flux ratio, a high correlation was attained for a range of flow conditions where capillary instability is insignificant.

Experimental and numerical investigation of the primary breakup of an airblasted liquid sheet

2017 ◽  
Vol 91 ◽  
pp. 208-224 ◽  
Author(s):  
K. Warncke ◽  
S. Gepperth ◽  
B. Sauer ◽  
A. Sadiki ◽  
J. Janicka ◽  
...  
Keyword(s):  
Numerical Investigation ◽  
Liquid Sheet ◽  
Primary Breakup

Characterization of Liquid Sheet Breakup Using Numerical Experiments

2012 ◽  
Author(s):  
Jarrod Sinclair ◽  
Sylvester Abanteriba
Keyword(s):  
Reynolds Number ◽  
Velocity Component ◽  
Numerical Experiments ◽  
Liquid Sheet ◽  
Phase Method ◽  
Normal Velocity ◽  
Fuel Injector ◽  
Number Range ◽  
Primary Breakup ◽  
Nozzle Configuration

For the plain orifice nozzle configuration, breakup mode analysis of the issuing liquid jet has been extensively, over the years, undertaken. The works of Rayleigh, Haenlein, Ohnesorge, Reitz and others have used an Ohnesorge-Reynolds chart to clearly characterize breakup into four distinct modes. These include: (1) Rayleigh, (2) first wind induced, (3) second wind induced, and (4) prompt atomization. Planar liquid sheet flows have not undergone such intensive characterization analysis. In this work a non-expanding (nor thinning) liquid sheet is injected into a quiescent volume of gas from a planar nozzle of constant opening height. The flow has no co-flowing gas stream nor air-assistance to drive the disintegration. The nozzle configuration and subsequent liquid primary breakup is somewhat similar to an outward opening fuel injector having an annular outlet with a large radius to needle lift height ratio. The numerical experiments in this work use a high fidelity Computational Fluid Dynamics (CFD) modeling approach. This includes the Volume-Of-Fluid (VOF) two-phase method to represent the liquid and gas fluids both considered to be incompressible, coupled with the Large Eddy Simulation (LES) treatment of turbulence modeling. The initial primary breakup of the liquid sheet into large droplets, ligaments and other structures is the main focus of the modeling. As such, secondary breakup and possible evaporation of the liquid is not considered. Due to the configuration of the planar nozzle, upstream cavitation of the liquid within the nozzle is also not considered. Breakup studies were conducted within the Reynolds number range of 3,000 to 23,400, and Ohnesorge number range of 0.004 to 0.1. Results are extensively validated with the works of Heukelbach and Scholz. In-nozzle velocity profiles are characterized with Reynolds number showing laminar, semi- and fully-turbulent states in the flow boundary layer and core. Velocity profile relaxation is studied as the liquid sheet transitions from a wall-bounded flow within the nozzle to a free shear flow surrounded by gas. Particularly, the axial velocity component is seen to weaken, whilst the sheet normal velocity component strengthens and aids in disintegration of the liquid sheet.

scholarly journals Experimental investigation on cellular breakup of a planar liquid sheet from an air-blast nozzle

2004 ◽  
Vol 16 (3) ◽  
pp. 625-632 ◽  
Author(s):  
Jaewan Park ◽  
Kang Y. Huh ◽  
Xianguo Li ◽  
Metin Renksizbulut
Keyword(s):  
Experimental Investigation ◽  
Liquid Sheet ◽  
Air Blast
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