Integrated Computational Study for Total Atomization Process of Primary Breakup to Spray Droplet Formation in Injector Nozzle

2016 ◽  
Author(s):  
Naoya Ochiai ◽  
Jun Ishimoto ◽  
Akira Arioka ◽  
Nobuhiko Yamaguchi ◽  
Yuzuru Sasaki ◽  
...  
Keyword(s):  
Computational Study ◽  
Droplet Formation ◽  
Atomization Process ◽  
Spray Droplet ◽  
Injector Nozzle ◽  
Primary Breakup

Computational Prediction of the Effect of Microcavitation on an Atomization Mechanism in a Gasoline Injector Nozzle

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
Jun Ishimoto ◽  
Fuminori Sato ◽  
Gaku Sato
Keyword(s):  
High Speed ◽  
Liquid Core ◽  
Liquid Interface ◽  
Nozzle Flow ◽  
Force Model ◽  
Shear Stresses ◽  
Atomization Process ◽  
Injector Nozzle ◽  
Liquid Atomization ◽  
Primary Breakup

The effect of microcavitation on the 3D structure of the liquid atomization process in a gasoline injector nozzle was numerically investigated and visualized by a new integrated computational fluid dynamics (CFD) technique for application in the automobile industry. The present CFD analysis focused on the primary breakup phenomenon of liquid atomization which is closely related to microcavitation, the consecutive formation of liquid film, and the generation of droplets by a lateral flow in the outlet section of the nozzle. Governing equations for a high-speed lateral atomizing injector nozzle flow taking into account the microcavitation generation based on the barotropic large eddy simulation-volume of fluid model in conjunction with the continuum surface force model were developed, and then an integrated parallel computation was performed to clarify the detailed atomization process coincident with the microcavitation of a high-speed nozzle flow. Furthermore, data on such factors as the volume fraction of microcavities, atomization length, liquid core shapes, droplet-size distribution, spray angle, and droplet velocity profiles, which are difficult to confirm by experiment, were acquired. According to the present analysis, the atomization rate and the droplets-gas atomizing flow characteristics were found to be controlled by the generation of microcavitation coincident with the primary breakup caused by the turbulence perturbation upstream of the injector nozzle, hydrodynamic instabilities at the gas-liquid interface, and shear stresses between the liquid core and periphery of the jet. Furthermore, it was found that the energy of vorticity close to the gas-liquid interface was converted to energy for microcavity generation or droplet atomization.

Computational study of core-shell droplet formation in coaxial electrohydrodynamic atomization process

AIChE Journal ◽  
2016 ◽  
Vol 62 (12) ◽  
pp. 4259-4276 ◽  
Author(s):  
Wei-Cheng Yan ◽  
Pooya Davoodi ◽  
Yen Wah Tong ◽  
Chi-Hwa Wang
Keyword(s):  
Computational Study ◽  
Droplet Formation ◽  
Core Shell ◽  
Atomization Process ◽  
Electrohydrodynamic Atomization

A Numerical Investigation of Non-Evaporating and Evaporating Diesel Sprays

2008 ◽  
Author(s):  
Sibendu Som ◽  
Suresh K. Aggarwal
Keyword(s):  
Diesel Engines ◽  
Fuel Injection ◽  
Spray Penetration ◽  
Nozzle Orifice ◽  
Fuel Droplets ◽  
Injector Nozzle ◽  
Primary Breakup ◽  
Penetration Data ◽  
Modeling Code ◽  
Breakup Model

Fuel injection characteristics, in particular the atomization and penetration of the fuel droplets, are known to affect emission and particulate formation in diesel engines. It is also well established that the primary atomization process is induced by aerodynamics in the near nozzle region, as well as cavitation and turbulence from the injector nozzle. However, most breakup models used to simulate the primary breakup process in diesel engines only consider the aerodynamically induced breakup. In this paper, the standard breakup models in Diesel Engine modeling code called “CONVERGE” are examined in constant volume spray chamber geometry using the available spray data. Since non-evaporating sprays provide a more stringent test for spray models, the x-ray data from Advanced Photon Source is used for detailed validation of the primary breakup model, especially in the region very close to the nozzle. Extensive validation of the spray models is performed under evaporating conditions using liquid length and spray penetration data. Good agreement is observed for global spray characteristics. However, the breakup model could not reproduce some of the experimental trends reported in literature thus identifying the need for a more comprehensive primary breakup model. An attempt is made to statically couple the internal nozzle flow with spray simulations, and examine the effect of nozzle orifice geometry on spray penetration.

Computational Study of the Air/Fuel Mixture in a Small Spark Ignition Engine

2007 ◽  
Author(s):  
Suzanne Caulfield ◽  
Ryo S. Amano
Keyword(s):  
Fluid Dynamics ◽  
Formation Process ◽  
High Speed ◽  
Computational Study ◽  
Spark Ignition ◽  
Droplet Formation ◽  
Spark Ignition Engine ◽  
Droplet Breakup ◽  
High Speed Photography ◽  
Fuel Delivery

In an effort to understand the fluid dynamics in the droplet formation process, during the fuel delivery portion of operation of a small spark ignition engine, a computational study of the process was undertaken. A combination of high-speed photography and Computational Fluid Dynamics was used to investigate the droplet formation process. Droplets of liquid are stripped from a column of liquid and entrained in a high velocity, cross-flow air stream. This process is known as aerodynamic stripping. This aerodynamic stripping is the process by which fuel is metered and delivered to a spark ignition engine. The condition of the fuel and air mixtures has an impact on the combustion event in the engine. Therefore, a thorough understanding of the fuel delivery process is desirable. This paper details a comprehensive CFD model that was created to explore the possibility of modeling the droplet breakup process. The mesh density required for this analysis was investigated. The accuracy of the predictions was verified by comparing the CFD results with high-speed film taken of the process. The results show that the process can be modeled accurately, provided the correct size mesh is used, and that the predicted droplets compare well with those seen in the film.

scholarly journals Effect of Frequency on Droplet Characteristics in Ultrasonic Atomization Process

2019 ◽  
Vol 130 ◽  
pp. 01002 ◽  
Author(s):  
Amelia Sugondo ◽  
Sutrisno ◽  
Willyanto Anggono ◽  
Olga Anne
Keyword(s):  
Droplet Size ◽  
Vibration Frequency ◽  
Droplet Formation ◽  
Frequency Effect ◽  
Atomization Process ◽  
Bending Vibration ◽  
Ultrasonic Atomization ◽  
Spray Process ◽  
Vof Model ◽  
Engine Combustion

The study of ultrasonic atomization is one of the important factors for fuel spray process in the diesel engine combustion chamber. The droplet characteristics are influenced by liquid properties and vibration frequency. In this study, the phenomenon of droplet formation and droplet size were studied at different frequencies of the ultrasonic atomization processes for water liquid. The ultrasonic atomizer was used for the atomization process to generate droplets. CFD- 2D with the Volume of Fluid (VOF) model was used to study the process of droplet size and droplet formation at different frequencies. Water with constant film thickness and bending vibration at constant vibration amplitude were used in this model. The variation of vibration frequencies is applied from 50 kHz to 200 kHz with 50 kHz increment. The results showed that the number of droplets and the area of droplet formation increases with the increases in the vibration frequency. Effect of vibration frequency to the size of the droplet, time for droplet formation, velocity, and several droplets is more significant at vibration frequency 50 kHz to 100 kHz than vibration frequency from 100 kHz to 200 kHz.

scholarly journals Degradation of lactoferrin caused by droplet atomization process via two-fluid nozzle: The detrimental effect of air–water interfaces

2021 ◽  
Author(s):  
Huy M. Dao ◽  
Sawittree Sahakijpijarn ◽  
Robert R. Chrostowski ◽  
Chaeho Moon ◽  
Filippo Mangolini ◽  
...  
Keyword(s):  
Conformational Change ◽  
Freeze Drying ◽  
Tertiary Structure ◽  
Polyacrylamide Gel Electrophoresis ◽  
Droplet Formation ◽  
Size Exclusion ◽  
Atomization Process ◽  
Dry Powders ◽  
Two Fluid ◽  
Low Shear

ABSTRACTBiological macromolecules, especially therapeutic proteins, are delicate and highly sensitive to degradation from stresses encountered during the manufacture of dosage forms. Thin-film freeze-drying (TFFD) and spray freeze-drying (SFD) are two processes used to convert liquid forms of protein into dry powders. In the production of inhalable dry powders that contain proteins, these potential stressors fall into three categories based on their occurrence during the primary steps of the process: (1) droplet formation (e.g., the mechanism of droplet formation, including spray atomization), (2) freezing, and (3) frozen water removal (e.g., sublimation). This study compares the droplet formation mechanism used in TFFD and SFD by investigating the effects of spraying on the stability of proteins, using lactoferrin as a model. This study considers various perspectives on the degradation (e.g., conformation) of lactoferrin after subjecting the protein solution to the atomization process using a pneumatic two-fluid nozzle (employed in SFD) or a low-shear drop application through the nozzle. The surface activity of lactoferrin was examined to explore the interfacial adsorption tendency, diffusion, and denaturation process. Subsequently, this study also investigates the secondary and tertiary structure of lactoferrin, the quantification of monomers, oligomers, and ultimately, aggregates. The spraying process affected the tertiary structure more negatively than the tightly woven secondary structure, resulting in a 1.5 nm red shift in peak position corresponding to the Tryptophan (Trp) residues. This conformational change can either (a) be reversed at low concentrations via relaxation or (b) proceed to form irreversible aggregates at higher concentrations. Interestingly, when the sample was allowed to progress into micron-sized aggregates, such a dramatic change was not detected using methods such as size-exclusion chromatography, polyacrylamide gel electrophoresis, and dynamic light scattering at 173°. A more complete understanding of the heterogeneous protein sample was achieved only through a combination of 173° and 13° backward and forward scattering, a combination of derived count rate measurements, and micro-flow imaging (MFI). Finally, compared to the low-shear dripping used in the TFFD process, lactoferrin underwent a relatively fast conformational change upon exposure to the high air-water interface of the two-fluid atomization nozzle used in the SFD process as compared to the low shear dripping used in the TFFD process. The interfacial induced denaturation that occurred during spraying was governed primarily by the size of the atomized droplets, regardless of the duration of exposure to air.

A Design-Variable-Based Computational Study on the Unsteady Internal-Flow Characteristics of the Urea-SCR Injector for Commercial Vehicles

2017 ◽  
Vol 379 ◽  
pp. 64-72
Author(s):  
Chang Su Kim ◽  
Sung Young Park
Keyword(s):  
Computational Study ◽  
Internal Flow ◽  
Flow Coefficient ◽  
Basic Material ◽  
Mean Flow ◽  
Initial Flow ◽  
Injector Nozzle ◽  
Injection Quantity ◽  
Study Results ◽  
The Mean

This study conducted a computational analysis on the characteristics of the unsteady internal flow of the Urea-SCR injector using reverse engineering. The flow coefficient that changed according to time was calculated, and the flow-coefficient data from the injector-needle movement were secured. To objectively compare the responsiveness of the injector, the time taken by the flow-coefficient number to change in the injector-needle rise interval and to reach 80 % of the mean flow coefficient was indexed. The design variables of the injector, nozzle angles, and the number of nozzles were selected to analyze the effect on the mean flow coefficient and the total injection quantity. The study results indicate that the effect of the nozzle angles on the total injection quantity per time is insignificant, but when the number of nozzles was excessively increased, the total injection quantity per time was decreased. The characteristic changes of the initial flow coefficient of the increased needle regarding the injector-nozzle angle and the nozzle number were analyzed as the characteristics of the injector responsiveness. This analytic result is used as the basic material for the design of the injector.

Influence of Nozzle Sac Volume on Diesel Spray Droplet Sizes

1992 ◽  
Vol 206 (4) ◽  
pp. 239-248 ◽  
Author(s):  
J R Farrar-Khan ◽  
G E Andrews ◽  
P T Williams
Keyword(s):  
Diesel Spray ◽  
Opening Pressure ◽  
Spray Droplet ◽  
Injector Nozzle ◽  
Fuel Flow ◽  
Droplet Sizes ◽  
Flow Quantity ◽  
Upstream Flow ◽  
Nozzle Opening Pressure ◽  
Nozzle Opening

The influence of nozzle sac volume and associated changes in the fuel hole upstream flow on the spray atomization, velocity and penetration were studied. Four injectors, designed for applications in 1 litre per cylinder diesel engines, were investigated with the same 215 bar injector nozzle opening pressure and fuel flow quantity. A Malvern 2600c Series diesel spray laser diffraction spray analyser was used. Significant differences in the spray characteristics were found which helped to explain some of the emission differences between the four injectors.

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