Atomization of acoustically forced liquid sheets

2019 ◽  
Vol 880 ◽  
pp. 653-683 ◽  
Author(s):  
Sandip Dighe ◽  
Hrishikesh Gadgil
Keyword(s):  
Acoustic Field ◽  
Cutoff Frequency ◽  
Liquid Sheet ◽  
Liquid Jets ◽  
Liquid Sheets ◽  
Aerodynamic Interaction ◽  
Transverse Acoustic ◽  
External Acoustic Field ◽  
Acoustic Forcing ◽  
Sheet Breakup

Atomization of a smooth laminar liquid sheet produced by the oblique impingement of two liquid jets and subjected to transverse acoustic forcing in quiescent ambient is investigated. The acoustic forcing perturbs the liquid sheet perpendicular to its plane, thereby setting up a train of sinuous waves propagating radially outwards from the impingement point. These sheet undulations grow as the wave speed decreases towards the edge of the sheet and the sheet characteristics, like intact length and mean drop size, reduce drastically as compared to the natural breakup. Our observations show that the effect of the acoustic field is perceptible over a continuous range of forcing frequencies. Beyond a certain forcing frequency, called the cutoff frequency, the effect of the external acoustic field ceases. The cutoff frequency is found to be an increasing function of the Weber number. Our measurements of the characteristics of spatially amplifying sinuous waves show that the instabilities responsible for the natural sheet breakup augment in the presence of external forcing. Combining the experimental observations and measurements, we conclude that the linear theory of aerodynamic interaction (Squire’s theory) (Squire, Brit. J. Appl. Phys., vol. 4 (6), 1953, pp. 167–169) predicts the important features of this phenomenon reasonably well.

Liquid Sheet Breakup in Gas-Centered Swirl Coaxial Atomizers

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
V. Kulkarni ◽  
D. Sivakumar ◽  
C. Oommen ◽  
T. J. Tharakan
Keyword(s):  
Flow Behavior ◽  
Liquid Sheet ◽  
Liquid Sheets ◽  
Sheet Surface ◽  
Air Jet ◽  
Entrainment Process ◽  
Sheet Breakup ◽  
Experimental Fluids ◽  
Flow Experiments

The study deals with the breakup behavior of swirling liquid sheets discharging from gas-centered swirl coaxial atomizers with attention focused toward the understanding of the role of central gas jet on the liquid sheet breakup. Cold flow experiments on the liquid sheet breakup were carried out by employing custom fabricated gas-centered swirl coaxial atomizers using water and air as experimental fluids. Photographic techniques were employed to capture the flow behavior of liquid sheets at different flow conditions. Quantitative variation on the breakup length of the liquid sheet and spray width were obtained from the measurements deduced from the images of liquid sheets. The sheet breakup process is significantly influenced by the central air jet. It is observed that low inertia liquid sheets are more vulnerable to the presence of the central air jet and develop shorter breakup lengths at smaller values of the air jet Reynolds number Reg. High inertia liquid sheets ignore the presence of the central air jet at smaller values of Reg and eventually develop shorter breakup lengths at higher values of Reg. The experimental evidences suggest that the central air jet causes corrugations on the liquid sheet surface, which may be promoting the production of thick liquid ligaments from the sheet surface. The level of surface corrugations on the liquid sheet increases with increasing Reg. Qualitative analysis of experimental observations reveals that the entrainment process of air established between the inner surface of the liquid sheet and the central air jet is the primary trigger for the sheet breakup.

Flow Development of a Liquid Sheet Issued Into Low-Speed Airstream

2020 ◽  
Author(s):  
Amin Jaberi ◽  
Mehran Tadjfar
Keyword(s):  
High Speed ◽  
Liquid Sheet ◽  
Liquid Jets ◽  
High Speed Photography ◽  
Low Speed ◽  
Liquid Sheets ◽  
Flow Development ◽  
Flow Feature ◽  
Subsonic Crossflow ◽  
Jet Characteristics

Abstract In this study, a liquid sheet with an aspect ratio of 90 and a thickness of 0.35 was experimentally investigated when issued into a low-speed subsonic crossflow. High speed photography and shadowgraphy technique were employed to capture the instantaneous physics of the liquid sheet. Flow visualizations were used to investigate the flow development of the liquid sheet. It was found that this flow exhibited a completely different flow structure than circular or other non-circular liquid sheets. It was found that the liquid sheet developed a concave-like shape in the presence of the transverse airstream. This phenomenon, named as inflated sheet, was absent in regular circular liquid jets injected into gaseous crossflow. It was revealed the inflated sheet was the main feature of the liquid sheet that made the jet characteristics unique. The flow feature of the inflated sheet structure and its alteration with flow condition was fully examined. Moreover, the width and trajectory of the liquid sheet were quantitatively studied at different Weber numbers and for the constant momentum ratio of 40. It was found that the fluid width could be a useful parameter to distinguish different regimes of the flow.

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.

Behavior of cylindrical liquid jets evolving in a transverse acoustic field

2009 ◽  
Vol 21 (2) ◽  
pp. 023601 ◽  
Author(s):  
Jean-Baptiste Carpentier ◽  
Françoise Baillot ◽  
Jean-Bernard Blaisot ◽  
Christophe Dumouchel
Keyword(s):  
Acoustic Field ◽  
Liquid Jets ◽  
Transverse Acoustic

Nonlinear instability of plane liquid sheets

2000 ◽  
Vol 406 ◽  
pp. 281-308 ◽  
Author(s):  
SEYED A. JAZAYERI ◽  
XIANGUO LI
Keyword(s):  
Weber Number ◽  
Density Ratio ◽  
Perturbation Expansion ◽  
Liquid Sheet ◽  
Fundamental Wave ◽  
Liquid Density ◽  
Initial Amplitude ◽  
Nonlinear Stability Analysis ◽  
Liquid Sheets ◽  
Breakup Time

A nonlinear stability analysis has been carried out for plane liquid sheets moving in a gas medium at rest by a perturbation expansion technique with the initial amplitude of the disturbance as the perturbation parameter. The first, second and third order governing equations have been derived along with appropriate initial and boundary conditions which describe the characteristics of the fundamental, and the first and second harmonics. The results indicate that for an initially sinusoidal sinuous surface disturbance, the thinning and subsequent breakup of the liquid sheet is due to nonlinear effects with the generation of higher harmonics as well as feedback into the fundamental. In particular, the first harmonic of the fundamental sinuous mode is varicose, which causes the eventual breakup of the liquid sheet at the half-wavelength interval of the fundamental wave. The breakup time (or length) of the liquid sheet is calculated, and the effect of the various flow parameters is investigated. It is found that the breakup time (or length) is reduced by an increase in the initial amplitude of disturbance, the Weber number and the gas-to-liquid density ratio, and it becomes asymptotically insensitive to the variations of the Weber number and the density ratio when their values become very large. It is also found that the breakup time (or length) is a very weak function of the wavenumber unless it is close to the cut-off wavenumbers.

On the interaction between a charged drop and an external acoustic field

2002 ◽  
Vol 47 (3) ◽  
pp. 299-305
Author(s):  
A. I. Grigor’ev ◽  
A. P. Gaibov ◽  
S. O. Shiryaeva
Keyword(s):  
Acoustic Field ◽  
Charged Drop ◽  
External Acoustic Field

Modeling of Gas Turbine Fuel Nozzle Spray

1997 ◽  
Vol 119 (1) ◽  
pp. 34-44 ◽  
Author(s):  
N. K. Rizk ◽  
J. S. Chin ◽  
M. K. Razdan
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Near Field ◽  
Continuous Phase ◽  
Liquid Sheet ◽  
Vapor Concentration ◽  
Fuel Vapor ◽  
Fuel Injector ◽  
Gas Temperature ◽  
Sheet Breakup

Satisfactory performance of the gas turbine combustor relies on the careful design of various components, particularly the fuel injector. It is, therefore, essential to establish a fundamental basis for fuel injection modeling that involves various atomization processes. A two-dimensional fuel injection model has been formulated to simulate the airflow within and downstream of the atomizer and address the formation and breakup of the liquid sheet formed at the atomizer exit. The sheet breakup under the effects of airblast, fuel pressure, or the combined atomization mode of the airassist type is considered in the calculation. The model accounts for secondary breakup of drops and the stochastic Lagrangian treatment of spray. The calculation of spray evaporation addresses both droplet heat-up and steady-state mechanisms, and fuel vapor concentration is based on the partial pressure concept. An enhanced evaporation model has been developed that accounts for multicomponent, finite mass diffusivity and conductivity effects, and addresses near-critical evaporation. The presents investigation involved predictions of flow and spray characteristics of two distinctively different fuel atomizers under both nonreacting and reacting conditions. The predictions of the continuous phase velocity components and the spray mean drop sizes agree well with the detailed measurements obtained for the two atomizers, which indicates the model accounts for key aspects of atomization. The model also provides insight into ligament formation and breakup at the atomizer exit and the initial drop sizes formed in the atomizer near field region where measurements are difficult to obtain. The calculations of the reacting spray show the fuel-rich region occupied most of the spray volume with two-peak radial gas temperature profiles. The results also provided local concentrations of unburned hydrocarbon (UHC) and carbon monoxide (CO) in atomizer flowfield, information that could support the effort to reduce emission levels of gas turbine combustors.

Dynamics of Liquid Sheet Breakup in Splash Plate Atomization

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
G. Thunivumani ◽  
Hrishikesh Gadgil
Keyword(s):  
Solid Surface ◽  
Weber Number ◽  
Jet Impingement ◽  
Liquid Sheet ◽  
Force Balance ◽  
Impingement Angle ◽  
Wide Range ◽  
Perforated Sheet ◽  
Sheet Breakup ◽  
Regime Map

An experimental study was conducted to investigate the breakup of a liquid sheet produced by oblique impingement of a liquid jet on a plane solid surface. Experiments are carried out over a wide range of jet Weber number (80–6300) and various jet impingement angles (30 deg, 45 deg, and 60 deg) are employed to study the sheet dynamics. The breakup of a liquid sheet takes place in three modes, closed rim, open rim, and perforated sheet, depending upon the Weber number. The transitions across the modes are also influenced by the impingement angle with the transition Weber number reducing with increase in impingement angle. A modified regime map is proposed to illustrate the role of impingement angle in breakup transitions. A theoretical model based on force balance at the sheet edge is developed to predict the sheet parameters by taking the shear interaction between the sheet and the solid surface into account. The sheet shape predicted by the model fairly matches with the experimentally measured sheet shape. The breakup length and width of the sheet are measured and comparisons with the model predictions show good agreement in closed rim mode of breakup.

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