Droplet Breakup in High-pressure Homogenizers

2015 ◽  
pp. 151-174
Keyword(s):  
High Pressure ◽  
Droplet Breakup

scholarly journals Comparison of Experimental and Numerical Transient Drop Deformation during Transition through Orifices in High-Pressure Homogenizers

2021 ◽  
Vol 5 (3) ◽  
pp. 32
Author(s):  
Benedikt Mutsch ◽  
Peter Walzel ◽  
Christian J. Kähler
Keyword(s):  
High Pressure ◽  
Visual Analysis ◽  
Imaging Technique ◽  
Extensional Flow ◽  
Droplet Breakup ◽  
Experimental Results ◽  
Drop Deformation ◽  
Droplet Deformation ◽  
Shadow Imaging ◽  
Good Agreement

The droplet deformation in dispersing units of high-pressure homogenizers (HPH) is examined experimentally and numerically. Due to the small size of common homogenizer nozzles, the visual analysis of the transient droplet generation is usually not possible. Therefore, a scaled setup was used. The droplet deformation was determined quantitatively by using a shadow imaging technique. It is shown that the influence of transient stresses on the droplets caused by laminar extensional flow upstream the orifice is highly relevant for the droplet breakup behind the nozzle. Classical approaches based on an equilibrium assumption on the other side are not adequate to explain the observed droplet distributions. Based on the experimental results, a relationship from the literature with numerical simulations adopting different models are used to determine the transient droplet deformation during transition through orifices. It is shown that numerical and experimental results are in fairly good agreement at limited settings. It can be concluded that a scaled apparatus is well suited to estimate the transient droplet formation up to the outlet of the orifice.

Droplet breakup regimes under high pressure conditions

1998 ◽  
Author(s):  
Bruno Vieille ◽  
Christian Chauveau ◽  
Iskender Gokalp
Keyword(s):  
High Pressure ◽  
Droplet Breakup

Coupled population balance–CFD simulation of droplet breakup in a high pressure homogenizer

2014 ◽  
Vol 68 ◽  
pp. 140-150 ◽  
Author(s):  
Per Julian Becker ◽  
François Puel ◽  
Arend Dubbelboer ◽  
Jo Janssen ◽  
Nida Sheibat-Othman
Keyword(s):  
High Pressure ◽  
Cfd Simulation ◽  
Population Balance ◽  
Droplet Breakup ◽  
High Pressure Homogenizer

scholarly journals Scaling of Droplet Breakup in High-Pressure Homogenizer Orifices. Part I: Comparison of Velocity Profiles in Scaled Coaxial Orifices

2021 ◽  
Vol 5 (1) ◽  
pp. 7
Author(s):  
Felix Johannes Preiss ◽  
Benedikt Mutsch ◽  
Christian J. Kähler ◽  
Heike Petra Karbstein
Keyword(s):  
High Pressure ◽  
Spatial Scales ◽  
Droplet Diameter ◽  
Density Ratio ◽  
Experimental Studies ◽  
Velocity Profiles ◽  
Droplet Breakup ◽  
Measurement Technology ◽  
Dimensionless Numbers ◽  
Image Velocimetry

Properties of emulsions such as stability, viscosity or color can be influenced by the droplet size distribution. High-pressure homogenization (HPH) is the method of choice for emulsions with a low to medium viscosity with a target mean droplet diameter of less than 1 µm. During HPH, the droplets of the emulsion are exposed to shear and extensional stresses, which cause them to break up. Ongoing work is focused on better understanding the mechanisms of droplet breakup and relevant parameters. Since the gap dimensions of the disruption unit (e.g., flat valve or orifice) are small (usually below 500 µm) and the droplet breakup also takes place on small spatial and time scales, the resolution limit of current measuring systems is reached. In addition, the high velocities impede time resolved measurements. Therefore, a five-fold and fifty-fold magnified optically accessible coaxial orifice were used in this study while maintaining the dimensionless numbers characteristic for the droplet breakup (Reynolds and Weber number, viscosity and density ratio). Three matching material systems are presented. In order to verify their similarity, the local velocity profiles of the emerging free jet were measured using both a microparticle image velocimetry (µ-PIV) and a particle image velocimetry (PIV) system. Furthermore, the influence of the outlet geometry on the velocity profiles is investigated. Similar relationships were found on all investigated scales. The areas with the highest velocity fluctuations were identified where droplets are exposed to the highest turbulent forces. The Reynolds number had no influence on the normalized velocity fluctuation field. The confinement of the jet started to influence the velocity field if the outlet channel diameter is smaller than 10 times the diameter of the orifice. In conclusion, the scaling approach offers advantages to study very fast processes on very small spatial scales in detail. The presented scaling approach also offers chances in the optimization of the geometry of the disruption unit. However, the results also show challenges of each size scale, which can come from the respective production, measurement technology or experimental design. Depending on the problem to be investigated, we recommend conducting experimental studies at different scales.

IMPROVING DROPLET BREAKUP AND VAPORIZATION MODELS BY INCLUDING HIGH PRESSURE AND TURBULENCE EFFECTS

2000 ◽  
Vol 10 (3-5) ◽  
pp. 475-510 ◽  
Author(s):  
Iskendar Gokalp ◽  
C. Chauveau ◽  
C. Morin ◽  
B. Vieille ◽  
M. Birouk
Keyword(s):  
High Pressure ◽  
Droplet Breakup ◽  
Turbulence Effects

Modeling Atomization of High-Pressure Diesel Sprays

2000 ◽  
Vol 123 (2) ◽  
pp. 419-427 ◽  
Author(s):  
G. M. Bianchi ◽  
P. Pelloni ◽  
F. E. Corcione ◽  
L. Allocca ◽  
F. Luppino
Keyword(s):  
High Pressure ◽  
Common Rail ◽  
Droplet Breakup ◽  
Injection System ◽  
Spray Cone ◽  
Common Rail Injection System ◽  
Spray Structure ◽  
Numerical Predictions ◽  
Common Rail Injection ◽  
Evaporating Spray

This paper deals with a numerical and experimental characterization of a high-pressure diesel spray injected by a common-rail injection system. The experiments considered a free non-evaporating spray and they were performed in a vessel reproducing the practical density that characterizes a D.I. diesel engine at injection time. The fuel was supplied at high pressure by a common-rail injection system with a single hole tip. The computations have been carried out by using both the TAB model and a hybrid model that allows one to describe both liquid jet atomization and droplet breakup. In order to validate the breakup model, an extensive comparison between data and numerical predictions has been carried out in terms of spray penetration, Sauter mean diameter, near and far spray cone angles, and spray structure.

Sign in / Sign up

Export Citation Format

Share Document