Begell House Inc.
Atomization and Sprays
AAS
1044-5110
22
5
2012
ONE-DIMENSIONAL MODEL FOR THE PREDICTION OF IMPACT DYNAMICS OF A SHEAR-THINNING LIQUID DROP ON DRY SOLID SURFACES
371-389
10.1615/AtomizSpr.2012005599
Sang Mo
An
Severe Accident & PHWR Safety Research Division, Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon, 305-353, Republic of Korea
Sang Yong
Lee
Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology,
291, Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
drop impact
shear-thinning liquid
viscosity
dry surface
maximum spreading
This study proposes a 1D model that describes the time variations of the spreading ratio for a non-Newtonian (shear-thinning) liquid drop impinging on dry solid surfaces. This model is based on the previous model developed for Newtonian liquids, where an energy balance approach with a cylindrical disk approximation was adopted and the dissipation mechanism near the contact line was taken into account. The present model showed good predictions for the spreading behavior, and accordingly the maximum spreading ratios were predicted with 97% of the data within ±10% accuracy. Also, the model predictions of the receding behavior for a low-viscosity drop impinging on a hydrophobic surface were in good agreement with the experiments. However, the discrepancy in the receding behavior became larger for the higher-viscosity drop impacting on a hydrophilic surface because the contact angle hysteresis appears more prominent. Based on this model, the time variations of the liquid viscosity for an impinging shear-thinning drop were simulated, and the effects of non-Newtonian liquid rheological parameters in the Cross model on the postimpingement behavior were also examined in detail. Consequently, it was found that the liquid viscosity in a high shear rate range dominates the spreading and receding behavior of a shear-thinning drop.
OPTICAL ANALYSIS OF THE MIXING EFFECT IN FULLY DEVELOPED LIKE-DOUBLET IMPINGING JET SPRAYS
391-408
10.1615/AtomizSpr.2012005547
Tony
Yuan
Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan, Taiwan, ROC
Berlin
Huang
Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan, Taiwan, ROC
PLIF
equal momentum
doublet
fully developed
penetration percentage
mixing
momentum flux
axisymmetric wave
helical wave
This research utilized the planar laser-induced fluorescence technique and high-speed photography to determine the mixing characteristics of equal-momentum doublet impinging water jet sprays in fully developed conditions. The injector is composed of two 0.3 mm diameter orifices at +30 deg/−30 deg impinging angle. The penetration percentage (P.P.) of droplets passing the center plane of the sprays from either jet is identified to characterize the mixing phenomena. In this experimental setup, the best mixing occurs at the P.P. of 50%, however, the experimental observed P.P. were all >50%, and that indicates the effects of convection and diffusion on liquid mixing were fully relaxed. The analyses showed that the state of the jets at the impinging point has crucial effects on the P.P. From high-speed photography, the growth and the propagation of the waves on liquid jets are the controlling factors. The P.P. variation with momentum flux in fully developed conditions are induced by jet momentum flux fluctuation at impingement caused by the onset of axisymmetric waves on free jets, and by the skew impingement resulted from the growth of helical waves on jets at impinging point.
DROP IMPACT ON SUPERHYDROPHOBIC SURFACES−VARYING GRAVITATIONAL EFFECTS
409-429
10.1615/AtomizSpr.2012005704
D.
Duvivier
Universite de Mons−UMONS, Laboratoire de Physique des Surfaces et des Interfaces, Avenue Maistriau, 19, 7000 Mons, Belgium, Universite de Mons− UMONS, Centre de Recherches en Physique des Materiaux, Avenue Maistriau, 19, 7000 Mons, Belgium
Romain
Rioboo
University of Mons, Faculty of Sciences, Place du Parc, Mons, 7000 Hainaut; Universite de Mons−UMONS, Laboratoire de Physique des Surfaces et des Interfaces, Avenue Maistriau, 19, 7000 Mons, Belgium; Centre de Recherches en Physique des Materiaux
M.
Voue
Universite de Mons−UMONS, Centre de Recherches en Physique des Materiaux, Avenue Maistriau, 19, 7000 Mons, Belgium; Universite de Mons−UMONS, Laboratoire de Physique des Materiaux et Optique, Avenue Maistriau, 19, 7000 Mons, Belgium
J.
De Coninck
Universite de Mons−UMONS, Laboratoire de Physique des Surfaces et des Interfaces, Avenue Maistriau, 19, 7000 Mons, Belgium; Universite de Mons−UMONS, Centre de Recherches en Physique des Materiaux, Avenue Maistriau, 19, 7000 Mons, Belgium
drop impact
superhydrophobic
gravity
rebound
outcome
splash
hysteresis
We performed in this experimental study impacts of aqueous ferrofluid drops on a superhydrophobic surface. The ferrofluids were used to simulate changes of the gravitational acceleration g* by applying different magnetic fields. It has been shown that a rebound/no rebound boundary can be obtained when plotting the impact results as a function of Weber, Reynolds, and Bond numbers, which quantify, respectively, effects of inertia over capillary ones, inertia over viscous dissipation, and gravity over capillary effects. On a We versus Re/Bon graph an optimum value of n close to 4 has been obtained by support vector machine analysis. Conditions to get rebound or no rebound have been established as functions of the impact parameters and of the liquid characteristics, but also of the body forces intensities.
SPRAY CHARACTERISTICS OF AN OPEN-END SWIRL INJECTOR
431-445
10.1615/AtomizSpr.2012005646
Qing-Fei
Fu
School of Astronautics, Beihang University, Beijing 100191, China; Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, School of Medicine and Engineering, Beihang University, Beijing 100083,
China; School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL, United Kingdom
Li-Jun
Yang
School of Astronautics, Beihang University, Beijing 100191, China; Beijing Advanced Innovation Center for Big Data-Based Precision Medicine,
School of Medicine and Engineering, Beihang University, Beijing 100083,
China
Wei
Zhang
School of Astronautics, Beijing University of Aeronautics and Astronautics, Beijing, China, 100191
Kun-Da
Cui
School of Astronautics, Beijing University of Aeronautics and Astronautics, Beijing, China, 100191
spray characteristics
open-end swirl injector
discharge coefficient
spray cone angle
breakup length
The open-end swirl injector is unique because it has no convergent nozzle; i.e., the diameter of the swirl chamber and the nozzle is the same. Open-end swirl injectors are widely used in Russian oxidizer-rich staged combustion cycle engines, such as the preburner and main chamber injectors used in liquid-oxygen (LOX)/kerosene engines RD-120, RD-170, and RD-180. However, the guidelines for the design of open-end swirl injectors are unclear and cannot refer to the existing model for closed swirl injectors. In the present study, spray formation from open-end swirl injectors is described by experimentation in a spray test facility. The experiments were performed with injectors of different configurations to test the effect of injector geometry and flow conditions on the spray characteristics. It was found that as the geometric characteristic constant of the open-end swirl injectors increases both the mass flow rate and the discharge coefficient decrease. There are discrepancies when predicting the discharge coefficient of open-end swirl injectors with the existing models for closed swirl injectors; hence, an empirical equation for predicting the discharge coefficient of open-end swirl injectors is proposed. The spray cone angle increases as the pressure drop and geometric characteristic constant increase. The breakup length of the liquid sheet formed by the open-end swirl injector is inversely proportional to the pressure drop and geometric characteristic constant. The empirical equations for the spray cone angle and sheet breakup length of the open-end swirl injectors were fitted from the experimental results, respectively, which included both the effect of the injector geometry and flow conditions in the injector.
SIMULATION OF TWIN OVERLAPPING SPRAYS UNDERNEATH HYDRAULIC ATOMIZERS: INFLUENCE OF SPRAY HYDRODYNAMIC PARAMETERS
447-460
10.1615/AtomizSpr.2012006076
Hocine
Mzad
Department of Mechanical Engineering, Badji Mokhtar University of Annaba, P.O. Box 12, 23000, Annaba, Algeria
Mohamed
Elguerri
Department of Mechanical Engineering, Mohamed Boudiaf University of Oran, P.O. Box 1505, 31000, Oran, Algeria
sprayer
dispersion
overlap
simulation
hydrodynamic parameters
The demand for improved product quality and increased productivity has focused attention on the need for more efficient systems of spray cooling during continuous casting. Optimizing the hydrodynamic parameters of the jet during nozzle design helps to obtain better dispersion and economy in water consumption. If multiple nozzles are used in a conveyorized application, the overlapping liquid distribution pattern of the nozzles needs to be considered because the process may depend strongly on the relative local volume flux of the spray. The disposition of nozzles that create overlapping jet zones results in dispersion profiles that depend on the experimental conditions. In order to understand the fluid behavior in the overlap region, the present paper suggests a hydrodynamic investigation using a program of simulation based on the experimental correlations of pulverized water jets. The influence of the hydrodynamic parameters by varying the water pressure ΔP between 0.2 and 0.9 MPa is highlighted, which gives a very wide operating range. In addition, other parameters such as the nozzle's orifice-to-surface distance, H, and the nozzle opening angle, θ, are highlighted.