Droplet size estimation of two-phase flashing jets

Razzaghi, Minoo

doi:10.1016/0029-5493(89)90130-1

Cited by 33 publications

(13 citation statements)

References 10 publications

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“…The calculations ultimately rely on fuel properties, pressures and temperatures, which can result in the default model constants being unsuitable, especially at extreme conditions corresponding to superheated liquids in the case of high-pressure fuel injection. Razzaghi [38] studied the effect of superheating on the break-up of a flashing spray, determining a critical superheat degree whereby break-up due to thermal mechanisms dominate. It is this conclusion which suggests that the break-up model can be a significant and useful tool in building a numerical framework capable of predicting suitable droplet sizes and spray characteristics of a flash-boiling spray.…”

Section: Break-up Modelmentioning

confidence: 99%

Aspects of Numerical Modelling of Flash-Boiling Fuel Sprays

Price¹,

Hamzehloo²,

Aleiferis³

et al. 2015

SAE Technical Paper Series

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Flash-boiling of sprays may occur when a superheated liquid is discharged into an ambient environment with lower pressure than its saturation pressure. Such conditions normally exist in direct-injection spark-ignition engines operating at low incylinder pressures and/or high fuel temperatures. The addition of novel high volatile additives/fuels may also promote flashboiling. Fuel flashing plays a significant role in mixture formation by promoting faster breakup and higher fuel evaporation rates compared to non-flashing conditions. Therefore, fundamental understanding of the characteristics of flashing sprays is necessary for the development of more efficient mixture formation. The present computational work focuses on modelling flash-boiling of n-Pentane and isoOctane sprays using a Lagrangian particle tracking technique. First an evaporation model for superheated droplets is implemented within the computational framework of STAR-CD, along with a full set of temperature dependent fuel properties. Then the computational tool is used to model the injection of flashing sprays through a six-hole asymmetric injector. The computational results are validated against optical experimental data obtained previously with the same injector by high-speed imaging techniques. The effects of ambient pressure (0.5 and 1.0 bar) and fuel temperature (20-180° C) on the non-flashing and flashing characteristics are examined. Effects of initial droplet size and break-up submodels are also investigated. The computational methodology is able to reproduce important physical characteristics of flashboiling sprays like the onset and extent of spray collapse. Based on the current observations, further improvements to the mathematical methodology used for the flash-boiling model are proposed.

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Section: Break-up Modelmentioning

confidence: 99%

Aspects of Numerical Modelling of Flash-Boiling Fuel Sprays

Price¹,

Hamzehloo²,

Aleiferis³

et al. 2015

SAE Technical Paper Series

View full text Add to dashboard Cite

show abstract

“…Razzaghi [45] proposed a mechanism for the break-up of the superheated liquid. The model presumes that the droplets are sheared from the jet before the vapor generation takes place within spherical bubbles.…”

Section: Factors Influencing Bubble Growthmentioning

confidence: 99%

Flash-boiling atomization

Sher

Bar-Kohany

Rashkovan

2008

Progress in Energy and Combustion Science

306

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“…This is a common approximation made in phenomenological modeling of atomizers in cases where only one flow velocity scale is available (Lefebvre 1989;Razzaghi 1989;Schmidt et al 1999;Senecal et al 1999). …”

Section: Mathematical Formulationmentioning

confidence: 99%

Transient aerodynamic atomization model to predict aerosol droplet size of pressurized metered dose inhalers (pMDI)

Gavtash

Versteeg

Hargrave

et al. 2017

Aerosol Science and Technology

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Pressurized metered dose inhalers (pMDI) produce large numbers of droplets with smaller sizes than 5 mm to treat asthma and other pulmonary diseases. The mechanism responsible for droplet generation from bulk propellant liquid is poorly understood, mainly because the small length scales and short time scales make it difficult to characterize transient spray formation events. This article describes the development and findings of a numerical atomization model to predict droplet size of pharmaceutical propellants from first principles. In this model, the velocity difference between propellant vapor and liquid phase inside spray orifice leads to formation of wave-like instabilities on the liquid surface. Two variants of the aerodynamic atomization model are presented based on assumed liquid precursor geometry: (1) cylindrical jet-shaped liquid ligaments surrounded by vapor annulus; (2) annular liquid film with vapor flow in the core. The growth of instabilities on the liquid precursor surfaces and the size of the subsequently formed droplets are predicted by numerical solutions of dispersion equations. The droplet size predictions were compared with phase doppler anemometry (PDA) data and the predictions were in good agreement with the number mean diameter D 10 , which is representative of the respirable droplets. The temporal behavior of droplet size production was captured consistently well during the period of the first 95% of the propellant mass emission. The outcome of our modeling activities also suggests that, in addition to saturated vapor pressure of the propellant, its viscosity and surface tension are also key properties that govern pMDI droplet size. EDITORWarren Finlay

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Droplet size estimation of two-phase flashing jets

Cited by 33 publications

References 10 publications

Aspects of Numerical Modelling of Flash-Boiling Fuel Sprays

Aspects of Numerical Modelling of Flash-Boiling Fuel Sprays

Flash-boiling atomization

Transient aerodynamic atomization model to predict aerosol droplet size of pressurized metered dose inhalers (pMDI)

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