Disintegration Of Liquid Jet Research Articles

Spray of water-in-oil emulsified heavy oil with high water content

The spray of water-in-oil emulsified heavy oils with water content up to 30 % was studied at temperatures of 125 to 200 °C and pressures of 4 to 10 MPa. The spray based on four series of model emulsified heavy oil shows that the effects of spray temperature and pressure on the Sauter mean diameter (SMD) of oil droplets and spray cone angle (θs) follow the traditional breakup model. The emulsification increases the viscosity and surface tension of heavy oils, hindering disintegration of liquid jet into fine droplets during spray. The combination of appropriate water content and superheated degree allows flash boiling of water to overcome the above adverse effects, resulting in a decrease in SMD and an increase in θs. In the spray of the upgraded emulsified heavy oil obtained by visbreaking in high-pressure steam environments, the SMD of oil droplets could be lowered to 39 μm, which is only half of the corresponding value of the raw heavy oil.

Primary spray breakup from a nasal spray atomizer using volume of fluid to discrete phase model

Spray atomization process involves complex multi-phase phenomena. Abundant literature and validation of spray modeling for industrial applications like fuel injection in internal combustion and turbine jet engines are available. However, only a handful of studies, primarily limited to discrete phase modeling, of low-pressure applications, such as nasal spray exists. This study aims to provide insight into the external and near-nozzle spray characterization of a continuous spray and establishes good validation against the experiment. A three-dimensional (3D) x-ray scanner was used to extract the internal nasal spray nozzle geometry which was reconstructed to build a 3D computational model. A novel volume-of-fluid to discrete phase transition model was used to track the liquid phase and its transition to droplets, which was based on the shape and size of the liquid lumps. In this study, an early pre-stable and stable phase of spray plume development was investigated. Qualitative and quantitative analyses were carried out to validate the computational model. A liquid column exited a nozzle which distorted at its base with advancement in time and eventually formed a hollow-cone liquid sheet. It then disintegrated due to instability that produced fluctuations to form ligaments resulting in secondary breakup. This study provides in-depth understanding of liquid jet disintegration and droplet formation, which adds value to future nasal spray device designs and techniques to facilitate more effective targeted nasal drug delivery.

Electrohydrodynamic instability and disintegration of low viscous liquid jet

The simple-jet mode can be developed from dripping, dripping faucet (transition), and jetting when subjected to a sufficient strong electric field caused by a needle-plated electrode. In the present work, the instability and disintegration of an electrified jet of anhydrous ethanol in the electrohydrodynamic simple-jet mode are visualized by a high-speed camera. A systematic analysis and description on the evolution of the breakup morphology of the charged jet in the simple-jet mode was carried out. In the dripping mode at low Weber number, the unstable simple-jet occurs, while the stable simple-jet mode happens as Weber number higher than critical value. In a dripping faucet and jetting regime, the simple-jet mode can easily take place, and jet undergoes typical breakup modes including varicose, whipping, whipping assisted bifurcation, and ramified instabilities as electric potential increases. The growth rate of the maximum perturbation of the zero-, first-, and second-order surface waves determines the type of the instabilities. The operating window of the simple-jet mode is presented to indicate that the simple-jet mode only operates in the suitable range of Weber number and electric Bond number. The spray characteristics, including envelope angle, droplet size, and the stable length of the electrified jet, have been explored to demonstrate that the uniform drops could be generated in the simple-jet regime. The evolution from the cone-jet to the simple-jet mode is also observed when a special hemispherical nozzle is used. For an almost stable electric potential, the cone-jet can gradually transform into the simple-jet with an increase in the liquid flow rate.

Disintegration of Free-falling Liquid Droplets, Jets, and Arrays in Air

Disintegration of Free-falling Liquid Droplets, Jets, and Arrays in Air

High-speed imaging database of water jet disintegration Part II: Temporal analysis of the primary breakup

This paper is Part II of a series of articles focusing on the disintegration of a cylindrical (Ø=0.60 mm diameter) water jet in a quiescent atmosphere, from Rayleigh to early atomization breakup regimes. Liquid fluorescence high-speed imaging is used here, instead of shadowgraphy, providing a more faithful representation of liquid jet breakup dynamics as described in Part I (Roth et al., 2021). Using these data, the aim of this article is to perform a temporal analysis of the primary breakup process and to investigate the variation of breakup length in the time-domain, under each breakup regime. The results indicate that the liquid jet velocity at the onset of primary breakup oscillates within 6% of the liquid injection velocity for all considered operating conditions. The analysis of the dynamic instability is also performed, showing the growth rate of the first three high-energy-containing modes. The results confirm that there is no single disturbance at a specific frequency whose growth rate leads to liquid jet disintegration in the second wind-induced breakup regime and the early atomization regime. However, it is found that the dimensionless mean breakup length monotonically varies with the product of the dimensionless amplitude by the dimensionless temporal growth rate. The values provided for the dominant frequencies and growth rate of disturbances can be useful for modelers simulating the breakup of liquid jets in a quiescent atmosphere. Finally, the temporally resolved image series analyzed in this article can be further investigated and compared with simulation results, by downloading the processed image data on the website:https://spray-imaging.com/water-jet.htmlor alternatively on Open Science Framework at: https://doi.org/10.17605/OSF.IO/CG3DF

High-speed imaging database of water jet disintegration Part I: Quantitative imaging using liquid laser-induced fluorescence

This paper is Part I in a series of articles focused on a fundamental study on liquid jet disintegration. The main goal of this work is to provide an extensive open access database of high-speed images and videos for modelers and researchers in the field of fluid mechanics studying the dynamics of a liquid jet transiting from the Rayleigh to the atomization regimes. The injector under examination has a single orifice 0.60 mm in diameter and was used to inject water into quiescent air at atmospheric temperature and pressure. In this study, only the liquid injection pressure was varied, reaching a maximum Reynolds number of approximately 60 000. Historically, high-speed videos of liquid jet disintegration have been captured via shadowgraphy imaging techniques. The alternate approach proposed here employs photographing a fluorescing liquid, using Laser Induced Fluorescence (LIF) allowing us to deduce the volume of the imaged liquid structures. The experiment is divided into two parts. In the first portion, the interrogation area measures a distance of 160 mm along the jet, and includes sets of ~800 images, recorded at 40 000 frames per second, corresponding to a temporal resolution of 25 µs. In the second part, the viewable area was reduced to 28 mm, and ~400 images were recorded at 50 000 frames per second resulting in a temporal resolution of 20 µs. This configuration enabled the finer structures of the jet to be resolved. In this case, two high-speed cameras orientated at 90˚ are used to simultaneously image the liquid jet. This two-angle detection configuration allows for the identification and more accurate account of the irregular liquid bodies formed in the jet. Descriptions of the optical arrangements, operating conditions, and the image post-processing methodologies used to obtain quantitative measurements of liquid depths from the LIF signal have been outlined. The resulting temporally resolved high-speed image series are openly downloadable on the website: https://spray-imaging.com/water-jet.htmlor alternatively on Open Science Framework at: https://doi.org/10.17605/OSF.IO/CG3DF

Effect of Cross-Flow Swirl on the Trajectory of Spray in an Annular Passage

Abstract This paper presents the experimental analysis of the impact of swirl number of cross-flowing air stream on liquid jet spray trajectory at a fixed air flow velocity of 42 m/s with the corresponding Mach number of 0.12. The experiments were conducted for 4 different swirl numbers (0, 0.2, 0.42, and 0.73) using swirl vanes at air inlet having angles of 0 deg, 15 deg, 30 deg, and 45 deg, respectively. Liquid to air momentum flux ratio (q) was varied from 5 to 25. High-speed (at 500 fps) images of the spray were captured, and those images were processed using matlab to obtain the path of the spray at various momentum flux ratios. The results show interesting trends for the spray trajectory in swirling air flow. High swirling flows not only lead to spray with lower radial penetration due to sharp bending and disintegration of liquid jet but also result in spray with large spread and spray area. Based on the results, correlations for the spray path have been proposed, which incorporates the effects of the swirl number of the air flow.

Liquid jet disintegration memory effect on downstream spray fluctuations in a coaxial twin-fluid injector

This paper intends to investigate the influence of unsteadiness in the liquid jet disintegration process on downstream fluctuations of spray characteristics in a coaxial twin-fluid injector. Time-resolved high-speed shadowgraphic imaging of the spray was obtained for different axial locations downstream of the injector exit at z = 0, 8Dl, and 30Dl, where Dl is the central liquid tube diameter. The primary jet breakup unsteadiness close to the injector exit was characterized by measuring both shear-driven Kelvin–Helmholtz (KH) instability and flapping instability in addition to jet breakup length fluctuations. Downstream of the liquid jet core region, the liquid shedding rate (fshed) was measured at z = 8Dl. The power spectrum of time series data of instantaneous volume mean diameter (VMD) measured at z = 30Dl indicated periodic variation of the droplet size. The corresponding frequency (fVMD) was obtained. It was found that for lower range of gas-to-liquid momentum flux ratio (M < 4), both fshed and fVMD are larger than the frequency of KH instability. Also, for such conditions, larger temporal variation of the droplet size is realized, and this leads to higher fluctuations of the local liquid mass flux. Proper orthogonal decomposition analysis of the shadowgraph images for different axial locations identified similar topology of the dominant mode that corresponds to flapping instability. The results suggest that even far downstream of the injector exit, some memory of the upstream unsteady jet breakup process is retained, which strongly influences spatio-temporal evolution of droplet characteristics, thereby contributing to local spray fluctuations.

Disintegration of diminutive liquid helium jets in vacuum

The phenomenon of liquid jets disintegrating into droplets has attracted the attention of researchers for more than 200 years. An overwhelming fraction of these studies considered classical viscous liquid jets issuing into ambient atmospheric gases, such as air. Here, we present an optical shadowgraphy study of the disintegration of a cryogenic liquid helium jet produced with a 5 µm diameter nozzle into vacuum. The physical properties of liquid helium, such as its density, surface tension, and viscosity, change dramatically as the jet flows through the nozzle and evaporatively cools in vacuum, eventually reaching the superfluid state. In this study, we demonstrate that, at different stagnation pressures and temperatures, droplet formation may involve spraying, capillary breakup, jet branching, and/or flashing and cavitation. The average droplet sizes produced in this work range from 3.4 × 1012 to 6.5 × 1012 helium atoms or 6.7-8.3 µm in diameter. This paper also reports on the distributions of sizes and shapes of the resulting droplets.

Simulation of Elliptical Liquid Jet Primary Breakup In Supersonic Crossflow

The study of elliptical liquid jets in supersonic flow in a Mach 2.0 is performed numerically. The primary breakup process of the elliptical liquid jet is simulated for a Weber number 223, liquid/gas flux momentum 4.0. The aspect ratios of elliptical geometries are set to be 0.25, 0.5, 1, 2, and 5. The results show a remarkable difference in liquid jet disintegration morphology at different aspect ratios. Under supersonic crossflow conditions, the elliptical liquid jet shows more breakup characteristics than the round liquid jet. As the aspect ratio grows, the penetration depth decreases. The elliptical liquid jet with AR=0.25 has the largest penetration depth in all cases. Moreover, the round jet has a maximum spreading angle of 50.2°. The changing trends of the column breakup length both x direction and y direction are similar. The elliptical jet at a lower aspect ratio has a shorter breakup length due to the narrower windward area. The liquid jet has a pair of larger horseshoe vortex structure and a wider wake region at a higher aspect ratio. Two pairs of reversal vortex pairs with obvious characteristics can be observed in all the simulations.

Determination of parameters of the compelled capillary disintegration of liquid jets

The technique of the automated precision parameters diagnostics of the compelled capillary disintegration of liquid jet is developed for the solution of heat-physical problems of receiving the stable monodisperse drop streams. The analysis of the images received from two digital cameras, located at the angle ninety degrees to each other is the basic of this procedure. One of cameras fixes the image of a drop flow in plane X, another - in plane Y. The minimum time of storing images is ∼0.1 microsecond. By means of specially developed software in the “on line” mode it is possible to process images and to determine the following parameters: jets speed, drops speed, jets length, jets diameter and drops diameter. Testing on objects with the known geometrical sizes confirmed working capacity and efficiency of the technique and the software. The relative error of parameters determination does not exceed 0.5% for jets with length of several millimeters. The developed technique and the software allow to increase the accuracy and reliability of parameters determination of compelled capillary disintegration of liquid jets and drop streams and expand possibilities of parameters control of setups for receiving monodisperse streams.

Cooling of streams of hydrogen and deuterium in relation to units for receiving cryogenic monodisperse targets

The purpose of work is development of the model and carrying out numerical calculations of cooling of thin jets from hydrogen and deuterium as applicable to installations for receiving cryogenic monodisperse targets. For this purpose the model of the expiration of a cryogenic jet to the low pressure area is created, the change of surface temperature and an internal jet part at different external parameters with respect to time is investigated through numerical solutions in PHOENICS software. Dependences of temperature change of liquid jets from hydrogen and deuterium along jet surface and on radius depending on jet diameter, speed, initial jet temperature and pressure in the working chamber of installations for receiving cryogenic monodisperse targets are carried out. The basic possibility of creation of high-speed cryogenic monodisperse targets is shown. According to calculations, at input of thin liquid jets of hydrogen or deuterium with a speed up to 100 m/s in the working chamber with low pressure, jets at distance up to 1 mm do not manage to freeze and can be broken into monodisperse drops. Drops are cooled and become granules due to evaporation. The developed model, the program for determination of parameters of steady monodisperse disintegration of liquid cryogenic jets and results of numerical calculations can be used during creation of installations for receiving high-speed cryogenic monodisperse targets.

3-D numerical consideration of nozzle structure on combustion and emission characteristics of DI diesel injector

A three-dimensional approach was used to capture the main parametric influences of injector geometries on combustion characteristics by utilization of a constant volume vessel. The investigation was performed by means of two case studies. In the first case study, the nozzle inclination angle was varied for group-hole nozzle layout, while the second case study analyses the single dense spray of an injector while its inlet-rounding radius to nozzle diameter ratio was being changed. Results demonstrate that closer included angle (up to 10˚) leads to higher penetration of spray and thus greater LOL (lift-off length) and ID (ignition delay). A decreasing trend as a result for overall emissions of NOx and soot mass fraction was observed. With regard to the second case study, decrement of r/d brings about enhancement of mixing quality of spray that leads to higher evaporation rate and accumulated heat release. Increasing heat release will augment chamber temperature that in turn contributes to higher NOx formation. Higher cavitation caused better liquid jet disintegration and smaller spray droplet that reduces soot mass fraction of late combustion process. The present study is intended to investigate primarily the effect of injector geometry on critical combustion components. The combination of changes in vessel pressure and group-hole nozzle angle is considered to study the combustion behavior of sprays and subsequent emissions content.

동축형 다공성재 분사기의 분열 메커니즘

동축형 다공성재 분사기에서는 기체가 분사기 중심을 지나는 액체 제트 주위를 둘러싼 다공성재를 통해 액체 제트를 향해 분사된다. 분사 방법의 차이로 인한 전단동축 분사기와 동축형 다공성재 분사기의 분열 메커니즘 차이를 살펴보기 위해, 전단동축 분사기와 동축형 다공성재 분사기를 사용하여 수류시험과 2-D 축대칭 수치해석을 진행하였다. 같은 유량조건에서의 가시화 이미지와 분무 평균입경을 비교하였으며, 수치해석을 통해 분사기 내부에서의 속도 분포가 액체 제트에 어떤 영향을 끼치는지 고찰하였다. 결과적으로, 기체의 유량이 늘어날수록 분사기 내부 속도가 낮음에도 동축형 다공성재 분사기의 미립화 및 혼합 성능이 전단동축 분사기에 비해 유리함을 확인할 수 있었다. In a coaxial porous injector, a gas propellant is injected through the porous cylinder surface to the liquid jet which is encircled by a porous cylinder. In this study, to observe the differences in disintegration mechanisms between a shear coaxial injector and a coaxial porous injector, cold-flow tests and 2-D axisymmetric numerical analysis have been carried out. The shadowgraph images and Sauter mean diameters were compared in similar experimental conditions, and the effects of velocity distributions at the inner injector region on the disintegration of liquid jet were investigated through the numerical calculations. As a result, in high air mass flow rate condition, the disintegration performance of coaxial porous injector is better than shear coaxial injector, in spite of a lower velocity at the inner injector region.

Analytical study of ultrasound influence on the molten metals atomization

This paper focuses on the study of influence of ultrasound on liquid atomization using ejection nozzles. Two principles of influence of ultrasound on the atomization process such as a change of conditions on gas-liquid boundary during the generation of ultrasound oscillation in the gas and liquid jet (film) disintegration under the action of capillary forces in cases of generation of ultrasound oscillation in the liquid are considered. The optimal values of the ultrasound oscillation frequencies are calculated. Two constructions of the nozzles patented are proposed.

A RANS simulation toward the effect of turbulence and cavitation on spray propagation and combustion characteristics

A multidimensional computational fluid dynamic code was developed and integrated with probability density function combustion model to give the detailed account of multiphase fluid flow. The vapor phase within injector domain is treated with Reynolds-averaged Navier–Stokes technique. A new parameter is proposed which is an index of plane-cut spray propagation and takes into account two parameters of spray penetration length and cone angle at the same time. It was found that spray propagation factor (SPI) tends to increase at lower r/d ratios, although the spray penetration tends to decrease. The results of SPI obtained by empirical correlation of Hay and Jones were compared with the simulation computation as a function of respective r/d ratio. Based on the results of this study, the spray distribution on plane area has proportional correlation with heat release amount, NO x emission mass fraction, and soot concentration reduction. Higher cavitation is attributed to the sharp edge of nozzle entrance, yielding better liquid jet disintegration and smaller spray droplet that reduces soot mass fraction of late combustion process. In order to have better insight of cavitation phenomenon, turbulence magnitude in nozzle and combustion chamber was acquired and depicted along with spray velocity.

Disintegration of flows of superheated liquid films and jets

This paper represents results on investigating the dynamics of boiling and disintegration of superheated liquid films and jets. The first part deals with experimental study of boiling liquid outflow through short cylindrical and slit channels. Evolution of disintegration of a hot water jet flow is observed both at low and moderate superheating and at high and limit superheating, and also for vaporization mechanisms corresponding to these superheatings. Peculiarities of disintegration of jets through slit and cylindrical channels are noticed. Results on measuring the reactive thrust of the jet through a slit channel under different geometrical conditions behind the channel outlet are represented. The 1/f fluctuations in transient regimes of superheated liquid boiling and in transient regimes of behavior of the jet shape are found. The second part of this article represents results on experimental investigation of nonsteady heat transfer and dynamics of the development of crisis phenomena at boiling of a falling subcooled liquid film in the conditions of stepwise heat release. The experimental data were obtained using synchronized high-speed infrared thermography and video. It is shown that with growth and condensation of vapor bubbles, on the liquid film interface appear large-amplitude waves that lead to considerably increasing local intensity of heat transfer. New data on the boiling incipience temperature in a subcooled liquid film, depending on the heat flux density, are obtained. It is found that the development of boiling crisis is a result of appearance of local dry patches and their subsequent growth by the mechanism of longitudinal thermal conductivity in the heat transfer wall as the equilibrium heat flux density is exceeded.

Jet and Vortex Ring-Like Structures in Internal Combustion Engines: Stability Analysis and Analytical Solutions

Recently developed models, describing the disintegration of liquid jets and the dynamics of vortex ring-like structures at Die- sel and gasoline engine-like conditions, are reviewed. The results of comparative analysis of modal and non-modal hydrody- namic instabilities of round viscous fluid jets are presented. Analytical formulae for vortex ring translational velocities, pre- dicted by vortex ring models, are compared with the results of numerical solutions to the underlying equations and experimen- tal data. A new approach to numerical simulation of two-phase two-dimensional flows, based on a combination of the full La- grangian method for the dispersed phase and the vortex blob method for the carrier phase, is discussed.

The effect of extensional viscosity on the effervescent atomization of polyacrylamide solutions

The paper contains the results of experimental investigation of the rheological characteristics and atomization process of solutions of polymer. The solutions had the polyacrylamide (PAA) mass fraction in the range from 0.0025 to 0.001. The solutions of polymer have non-Newtonian characteristics. It has been shown that shear viscosity increases with polymer concentration in the solutions. Extensional viscosity increases with increasing extensional rates. The Trouton ratio for glycerol solution is about 5.4. The Trouton ratios observed for the polymer solutions increase with increasing shear (extensional) rate and polymer concentration in solution.This paper draws a link between the extensional viscosity and the effervescent atomization. The polymer addition to cause the solution viscosity to increase, thereby different disintegration of liquid could be obtained. During two-phase atomization process of polymer solutions the characteristic stages in spray development have been observed. The phenomenon of the formation of “beads on a string” for solutions with low concentrations of polymer has been observed. The thin filament between droplets and/or bubbles was observed for all polymer solutions studied. Analysis of photos on forming the droplets showed that droplets diameter increases with increasing of polymer concentration. In all two-phase systems studied the Sauter mean diameter decreases with increase of gas to liquid flow rates ratio value. Sauter mean diameter is dependent on gas and liquid flow rates and the liquid properties. It is particularly important in processes in which the value of the average droplet diameter plays a key role.High molecular polymers added to a solvent involve the changes in the rheological properties of liquid and the disintegration of liquid jets and/or sheets. The effect of extensional viscosity on the droplets formation has been shown. The data obtained in the present study have shown that the decreasing of the extensional viscosity of the solution will reduce the spray's Sauter mean diameter. The results may be used, for example, to verify numerical models or in comparison with similar atomization processes.

The Experimental Analysis of the Polyacrylamide Solutions Effervescent Atomization

Abstract The paper contains the results of experimental investigation of the rheological characteristics and atomization process of polymer solutions. The solutions had the polyacrylamide mass fraction in the range from 0.0025 to 0.001. The solutions of polymer have non-Newtonian characteristics. It has been shown that viscosity increases with increasing of polymer concentration in the solutions. Extensional viscosity increases with increasing of extensional rates. The Trouton ratios observed for the polymer solutions increase with increasing shear (extensional) rate and polymer concentration in solution. High molecular polymers added to a solvent involve the changes in the rheological properties of liquid and the disintegration of liquid jets and/or sheets. The effect of extensional viscosity on the droplets formation has been shown. The data obtained in the present study have shown that the decreasing of the extensional viscosity of the solution will reduce the spray's droplets sizes. The results may be used for example to verify numerical models or comparisons with respect to similar atomization processes.