Liquid flow in a simplex swirl nozzle

Amini, Ghobad

doi:10.1016/j.ijmultiphaseflow.2015.09.004

Cited by 91 publications

(37 citation statements)

References 21 publications

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“…It was cylindrically shaped and larger in diameter inside the exit orifice. Such behaviour has been described by other authors [10,11,17]. The dimensionless diameter of the air core in the exit orifice was da/do = 0.74 ± 0.02 for all the inlet pressures and both liquids with no evident correlations to Re.…”

Section: Resultssupporting

confidence: 81%

Internal flow and air core dynamics in simplex and spill-return pressure-swirl atomizers

Malý

Janáčková

Jedelský

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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It is well known that the spray characteristics of pressure-swirl atomizers are strongly linked to the internal flow and that an unstable air core may cause instabilities in the spray. In this paper, a 10:1 scale transparent Plexiglas (PMMA) model of a pressure-swirl atomizer as used in a small gas turbine is introduced. The internal flow was examined using high-speed imaging, laser-Doppler anemometry and computational fluid dynamics tools. The experimental and numerical results were analysed and compared in terms of the air core morphology and its temporal stability. Two different liquids were used, Kerosene-type Jet A-1 represented a commonly used fuel while p-Cymene (4-Isopropyltoluene) matched the refractive index of the Plexiglas atomizer body. The internal flow characteristics were set using dimensionless numbers i.e. the Reynolds number and Froude number. The flow test conditions were limited to inlet Reynolds numbers from 750 to 1750. Two atomizers were examined to represent a Simplex and Spill-return (SR) geometries. In a comparative manner, the SR atomizer features a central passage in the rear wall of the swirl chamber. The main advantage of this concept is that the fuel is always supplied to the swirl chamber at a high pressure therefore providing good atomization over a wide range of the injection flow rate. However, the presence of the spill orifice strongly affects the internal flow even if the spill-line is closed. The air core in the Simplex atomizer was found fully developed and stable. The SR atomizer behaved differently, the air core did not form at all, and the spray was therefore unstable. KeywordsInternal flow dynamics, Pressure-swirl, transparent nozzle, CFD Introduction Pressure-swirl (PS) atomizers are used in many applications where a large surface area of droplets is needed or a surface must by coated by a liquid e.g. combustion, fire suspension or air conditioning. PS atomizers are easy to manufacture, reliable and provide good atomization quality. They convert the pressure energy of the pumped liquid into kinetic and surface energy of the resulting droplets. The pumped liquid is injected via tangential ports into a swirl chamber, where it gains a swirl motion, under which it leaves the exit orifice as a conical liquid sheet. The centrifugal motion of the swirling liquid creates a low-pressure zone in the centre of the swirl chamber and generate an air core along the centreline. The flow inside the atomizer is rather complex; it is two-phase with secondary flow effects. There is a strong link between internal flow conditions and the resulting spray characteristics, however, not all aspects of the internal flow are well understood. Before the advent of computational fluid dynamics, a number of authors attempted to describe the internal flow by relatively simple analytical approaches. One of the first was presented by Taylor [1] which focused on an inviscid analysis using Bernoulli's equation and the principle of maximal flow. Taylor derived an equation for the discharge coeffi...

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Section: Resultssupporting

confidence: 81%

Internal flow and air core dynamics in simplex and spill-return pressure-swirl atomizers

Malý

Janáčková

Jedelský

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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“…Experimentally, such helical structure has been observed by several authors, including Kim et al (2009), Donjat et al (2002) and Cooper and Yule (2001), while the phenomenon has also been demonstrated in CFD simulations by Dash et al (2001). The variation of the air core may induce large fluctuations of the film thickness and affect the subsequent atomization process (Amini, 2016).…”

Section: Introductionmentioning

confidence: 76%

“…Subsequently, a hollow cone spray is formed by the radially outward expanding liquid after it is discharged from the nozzle. Pressure-swirl atomizers are popular because of their geometrical simplicity, good atomization characteristics and resistance to clogging (Amini, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…Semiempirical correlations for the film thickness are given for example by Rizk and Lefebvre (1985) and Suyari and Lefebvre (1986). Some recent theoretical works include that by Amini (2016), where an analytical model is developed for the velocity fields inside a simplex atomizer, and the study of a tangential swirl atomizer by Wimmer and Brenn (2013), where the effect of viscosity on the flow rate is investigated.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of viscous fluid flow in a pressure-swirl atomizer using large-eddy simulation

Laurila

Roenby

Maakala

et al. 2019

International Journal of Multiphase Flow

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A computational fluid dynamics study is carried out on the inner nozzle flow and onset of liquid sheet instability in a large-scale pressure-swirl atomizer with asymmetric inflow configuration for high viscosity fluids. Large-eddy simulations (LES) of the two-phase flow indicate the unsteady flow character inside the nozzle and its influence on liquid sheet formation. A novel geometric volume-offluid (VOF) method by Roenby et al., termed isoAdvector, is applied for sharp interface capturing (Roenby J., Bredmose H., Jasak H., 2016, A computational method for sharp interface advection, Royal Society Open Science 3). We carry out a Reynolds number sweep (420 ≤ Re ≤ 5300) in order to investigate the link between the asymmetric inner nozzle flow and liquid sheet characteristics in laminar, transitional and fully turbulent conditions. Inside the nozzle, the numerical simulations reveal counter-rotating Dean vortices, flow impingement locations, and strong asymmetric flow features at all investigated Reynolds numbers. A helical, rotating gaseous core is observed when Re ≥ 1660. For laminar flow (Re = 420), an S-shaped liquid film is observed, while the gas core presence at Re ≥ 1660 results in a hollow cone liquid sheet. For the intermediate value Re = 830, the numerical simulations indicate a liquid sheet of mixed type.

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“…Meanwhile, droplet with small SMD will be taken away by the airflow and cannot be evenly distributed well in the combustion chamber, which results in unstable combustion (Hashimoto et al 2014). Studies (Lee et al 2010;Hashimoto et al 2014, Amini 2016 have shown that, high medium viscosity will make the spray SMD increase (Moon et al 2007;Lee et al 2010;Fan et al 2014). Lee et al (2010) and Moon (2007) found that the high medium viscosity will reduce the diameter of air core, resulting in the increase of the liquid film thickness and the spray SMD.…”

Section: Introductionmentioning

confidence: 99%

Effect of Viscosities on the Spray Characteristics of Pressure Swirl Nozzle

Liu

Lin

Zheng

et al. 2020

JAFM

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The effects of medium viscosity on the spray flow rate, spray Sauter Mean Diameter, droplet velocity and spray cone angle of pressure swirl nozzles are investigated by making use of the particle dynamics analysis system and high-speed photographic system. Based on the axial and radial distribution characteristics of Sauter Mean Diameter and droplet velocity, the water-glycerol mixture is used to simulate medium with a wide range of viscosities. It is found that with the increase of viscosity, the turbulence of the medium flow and the swirling effect is weakened, and the rated pressure becomes larger and the spray flow rate increases. Spray Sauter Mean Diameter and droplet axial velocity becomes larger, while the spray cone angle decreases. The development of the axial velocity distribution of spray cone is characterized by the radial and axial position parameters. The area of the large-droplet region on both sides of spray cone becomes larger, and the area of small-droplet region near the axis becomes smaller.

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Liquid flow in a simplex swirl nozzle

Cited by 91 publications

References 21 publications

Internal flow and air core dynamics in simplex and spill-return pressure-swirl atomizers

Internal flow and air core dynamics in simplex and spill-return pressure-swirl atomizers

Analysis of viscous fluid flow in a pressure-swirl atomizer using large-eddy simulation

Effect of Viscosities on the Spray Characteristics of Pressure Swirl Nozzle

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