Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Selected Basic Flows and Forces
- Part I Collision of Liquid Jets and Drops with a Dry Solid Wall
- Part II Drop Impacts onto Liquid Surfaces
- Part III Spray Formation and Impact onto Surfaces
- 7 Drop and Spray Diagnostics
- 8 Atomization and Spray Formation
- 9 Spray Impact
- Part IV Collisions of Solid Bodies with Liquid
- Part V Solid–Solid Collisions
- Index
- References
8 - Atomization and Spray Formation
from Part III - Spray Formation and Impact onto Surfaces
Published online by Cambridge University Press: 13 July 2017
Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Selected Basic Flows and Forces
- Part I Collision of Liquid Jets and Drops with a Dry Solid Wall
- Part II Drop Impacts onto Liquid Surfaces
- Part III Spray Formation and Impact onto Surfaces
- 7 Drop and Spray Diagnostics
- 8 Atomization and Spray Formation
- 9 Spray Impact
- Part IV Collisions of Solid Bodies with Liquid
- Part V Solid–Solid Collisions
- Index
- References
Summary
The process of atomization involves the generation of drops from bulk fluid, achieved using a wide variety of atomization concepts, depending on the desired local drop number, size and velocity flux densities, as well as on the bulk fluid and its properties, e.g. pure liquids, dispersions, suspensions, emulsions, etc. In the context of collision phenomena, atomization plays a key role in applications such as spray cooling, touchless cleaning and spray coating, whereby the latter can be understood in a very broad sense, encompassing applications such as spray painting, crop spraying, spray based encapsulation, domestic sprays (e.g. hair sprays, polishes) or even inhalators. Indeed, a majority of liquid collision phenomena involve atomization for the generation of individual drops and this fact motivates the present examination of the atomization process in more detail, with the aim of establishing an understanding between the atomization conditions and the resulting properties of the spray.
This chapter divides the atomization process into primary atomization (Section 8.1), i.e. overcoming the consolidating influence of surface tension by the action of internal and external forces (Lefebvre 1989), secondary atomization, and binary drop collisions in a spray, whereby several special modes of secondary atomization are treated in the final four sections. The causes of secondary atomization are manifold and can significantly alter the size distribution in a spray and are therefore important to consider. Typical causes of secondary atomization include aerodynamic forces whenever a drop is exposed to a relative air flow; covered in Section 8.2. Binary drop collisions can also lead to secondary atomization, as they occur in dense sprays, interacting sprays or when spray drops impinging onto a surface interact with drops ejected from the surface. Binary drop collisions are discussed in Section 8.3. Another cause of secondary atomization is when a drop impinges onto or is forced off a filament, for instance in a filter. This atomization scenario is the topic of Section 8.4. Finally, secondary atomization can also be electrically driven. In this case, evaporation in flight of electrified drops issued from electrostatic atomizers diminishes the drop surface area, while the electric charges they carry remain the same. As a result, the shrinking drop size can reach the so-called Rayleigh limit.
- Type
- Chapter
- Information
- Collision Phenomena in Liquids and Solids , pp. 354 - 411Publisher: Cambridge University PressPrint publication year: 2017
References
(ed.) (2011). Handbook of Atomization and Sprays: Theory and Applications, Springer, Heidelberg.
, and (2011). Instability of liquid sheets, in
(ed.), Handbook of Atomization and Sprays: Theory and Applications, Springer, Heidelberg, chapter 3, pp. 75–95.
and (1990). Coalescence and separation in binary collisions of liquid drops, J. Fluid Mech.
221: 183–204.Google Scholar
, and (2010). Experimental investigation of the correlation between nozzle flow and spray using laser Doppler velocimeter, phase Doppler system, highspeed photography, and X-ray radiography, Atom. Sprays
20: 57–70.Google Scholar
, and (1987). Dynamics of Polymeric Liquids. Vol. 1: Fluid Mechanics, John Wiley & Sons Inc., New York.
, , and (2010). Crater evolution after the impact of a drop onto a semi-infinite liquid target, Phys. Rev. E
82: 036319.Google Scholar
, and (1972). The interaction of falling water drops: coalescence, Proc. R. Soc. London Ser. A-Math.
326: 393–408.Google Scholar
, and (2001). The formation of satellite droplets by unstable binary drop collisions, Phys. Fluids
13: 2463–2477.Google Scholar
and (2007). Electrohydrodynamic systems, in
, and (eds.), Springer Handbook of Experimental Fluid Mechanics, Springer, Heidelberg, chapter C21, pp. 1317–1333.
(1931). The Mechanism of the Atomization of Liquids, US Department of Commerce, Bureau of Standards.
and (2010). Electrokinetically Driven Microfluidics and Nanofluidics, Cambridge University Press.
(2007). Diesel-diesel and diesel-ethanol drop collisions, Appl. Thermal Eng.
27: 604–610.Google Scholar
and (2006). Collision between immiscible drops with large surface tension difference: diesel oil and water, Exp. Fluids
41: 453–461.Google Scholar
and (1992). Morphological classification of disintegration of round liquid jets in a coaxial air stream, Atom. Sprays
2: 137–153.Google Scholar
(2005). Multiphase Flow Handbook, Vol. 59, CRC Press, Boca Raton.
and (2001). Disintegration of liquid jets and drop drag coefficients in pressurized nitrogen and carbon dioxide, Chemical Eng. Technol.
24: 619–624.Google Scholar
and (2001). Temporal properties of secondary drop breakup in the multimode breakup regime, Int. J. Multiph. Flow
27: 217–236.Google Scholar
and (1994). Boundary-layer stripping effects on droplet transcritical convective vaporization, Atom. Sprays
4: 325–367.Google Scholar
and (2010). Detailed numerical investigation of turbulent atomization of liquid jets, Atom. Sprays
20: 311–336.Google Scholar
and (1963). The aerodynamic instability and disintegration of viscous liquid sheets, Chem. Eng. Sci.
18: 203–214.Google Scholar
,
, and (2003). Coulomb fission: Rayleigh jets from levitated microdroplets, Nature
421: 128.Google Scholar
, , and (2010). Drop dynamics after impact on a solid wall: theory and simulations, Phys. Fluids
22: 062101.Google Scholar
, and (1995). Structure and breakup properties of sprays, Int. J. Multiph. Flow
21: 99–127.Google Scholar
and (2012). Direct numerical simulation of binary off-center collisions of shear thinning droplets at high Weber numbers, Phys. Fluids
24: 073105.Google Scholar
and (1953). Research into the performance of atomizers for liquids, Imp. Coll. Chem. Eng. Soc. J
7: 52–68.Google Scholar
, , , , , and (1995). Wetting effects on the spreading of a liquid droplet colliding with a flat surface: experiment and modeling, Phys. Fluids
7: 236–247.Google Scholar
, , and (2005). Collision between an ethanol drop and a water drop, Exp. Fluids
38: 731–738.Google Scholar
(1996). Droplet breakup phenomena in flows with velocity lag, Prog. Energy Combust. Sci.
22: 201–265.Google Scholar
, and (2004). Influence of nozzle flow on the atomization of liquid sheets and round jets, in
and (eds.), Atomization and Spray Processes, Vol. 7 of Schriftenreihe Mechanische Verfahrenstechnik, Shaker Verlag, Aachen.
, , , , ,
(2007). Effect of viscosity on droplet-droplet collision outcome: experimental study and numerical comparison, Phys. Fluids
19: 102106.Google Scholar
and (2010). Evaporation and discharge dynamics of highly charged multicomponent droplets generated by electrospray ionization, J. Phys. Chem. A
114: 1411–1419.Google Scholar
and (2001). An experimental study of drop deformation and breakup in extensional flow at high capillary number, Phys. Fluids
13: 1568–1576.Google Scholar
and (1961). The drop size of fan spray nozzle, measurements by the solidifying wax method compared with those obtained by other sizing techniques, Trans. Inst. Chem. Eng
39: 415–422.Google Scholar
(2002). Untersuchung zum Einfluss der Düseninnenströmung auf die Stabilität von flächigen Flüssigkeitsstrahlen, PhD thesis, Technische Universität Darmstadt.
(1955). Fundamentals of the hydrodynamic mechanism of splitting in dispersion processes, AIChE J.
1: 289–295.Google Scholar
(1996). Effect of internal flow conditions inside injector nozzles on jet breakup processes, in
(ed.), Recent Advances in Spray Combustion: Spray Atomization and Drop Burning Phenomena, Vol. 166 of Progress in Astronautics and Aeronauthics, AIAA Inc, New York, pp. 173–184.
(2000). Spray breakup mechanism from the hole-type nozzle and its applications, Atom. Sprays
10: 511–527.Google Scholar
and (1993). Drop properties after secondary breakup, Int. J. Multiph. Flow
19: 721–735.Google Scholar
and (1995). Drop deformation and breakup due to shock wave and steady disturbances, Int. J. Multiph. Flow
21: 545–560.Google Scholar
, and (1996). Breakup mechanisms and drag coefficients of high-speed vaporizing liquid drops, Atom. Sprays
6: 353–376.Google Scholar
, , and (2004). A lattice Boltzmann method for incompressible two-phase flows with large density differences, J. Comp. Phys.
198: 628.Google Scholar
, and (1992). An experimental investigation on the collision behaviour of hydrocarbon droplets, J. Fluid Mech.
234: 171–190.Google Scholar
, and (2002). Rayleigh–Taylor instability of viscoelastic drops at high Weber numbers, J. Fluid Mech.
453: 109–132.Google Scholar
, and (1999). Breakup of a liquid drop suddenly exposed to a high-speed airstream, Int. J. Multiph. Flow
25: 1263–1303.Google Scholar
(2002). Direkte numerische Simulation des primären Strahlzerfalls in Einstoffzerstäuberdüsen, PhD thesis, Technische Universität Darmstadt.
, , , , , and (2015). Mode of action of silicone drift control agents, in
(ed.), 26th Symposium on Pesticide Formulation and Delivery Systems: Emerging Trends Building on a Solid Foundation, ASTM Committee E35 on Pesticides, Antimicrobials, and Alternative Control Agents, ASTM International.
(1980). Measurement of liquid droplet disintegration mechanisms, Int. J. Multiph. Flow
6: 227–239.Google Scholar
and (1987). Fluid Mechanics, Pergamon Press, Oxford.
and (2001). Direct numerical simulation of the atomization of a liquid jet, Proc. ILASS-Europe, pp. 2–6.
and (2000). An experimental study of the effect of gas density on the distortion and breakup mechanism of drops in high speed gas stream, Int. J. Multiph. Flow
26: 229–244.Google Scholar
(1989). Atomization and Sprays, Hemisphere Publishing Corporation, New York.
(2003). Breakup of Liquid Sheets and Jets, Cambridge University Press.
and (1998). Drop and spray formation from a liquid jet, Annu. Rev. Fluid Mech.
30: 85–105.Google Scholar
(1999). Science and Engineering of Droplets: Fundamentals and Applications, William Andrew, Norwich, New York.
and (1997). An analysis of the distortion and breakup mechanisms of high speed liquid drops, Int. J. Multiph. Flow
23: 631–650.Google Scholar
and (1994). Effect of turbulence on the stability of liquid jets and the resulting droplet size distributions, Atom. Sprays
4: 583–604.Google Scholar
, , and (2011). Drop collisions with simple and complex surfaces, Curr. Opin. Colloid Interface Sci.
16: 292–302.Google Scholar
and (2004). Atomization characteristics on the surface of a round liquid jet, Exp. Fluids
36: 528–539.Google Scholar
and (1939). Disintegration of uranium by neutrons: a new type of nuclear reaction, Nature
143: 239–240.Google Scholar
and (1969). Electrohydrodynamics: a review of the role of interfacial shear stresses, Annu. Rev. Fluid Mech.
1: 111–146.Google Scholar
(1955). Correlation of experimental data on the disintegration of liquid jets, Ind. & Eng. Chem.
47: 1690–1701.Google Scholar
, and (2009). Needleless electrospinning: electrically-driven instability and multiple jetting from the free surface of a spherical liquid layer, J. Appl. Phys.
106: 114910.Google Scholar
, and (2013). Industrial Sprays and Atomization: Design, Analysis and Applications, Springer, Heidelberg.
, and (2008). Bag breakup of nonturbulent liquid jets in crossflow, Int. J. Multiph. Flow
34: 241–259.Google Scholar
(1936). Die Bildung von Tropfen an Düsen und die Auflösung flüssiger Strahlen, Z. Angew. Math. Mech.
16: 355–358.Google Scholar
(2014). Controlling Liquid Atomization using Dilute Emulsions:Mitigation of Pesticide Spray Drift, PhD thesis, Technische Universität Darmstadt.
, , , and (2014). Droplet-air collision dynamics: evolution of the film thickness, Phys. Rev. E
89: 013023.Google Scholar
(1997). Experiments on droplet collisions, bounce, coalescence and disruption, Prog. Energy Combust. Sci.
23: 65–79.Google Scholar
, and (2008). Experimental and mechanistic description of merging and bouncing in head-on binary droplet collision, J. Appl. Phys.
103: 064901.Google Scholar
and (2009). Note on “Dynamics of inertia dominated binary drop collisions,” [Phys. of Fluids 16, 3438 (2004)], Phys. Fluids
21: 022101.Google Scholar
and (2005). Numerical simulation of binary liquid droplet collision, Phys. Fluids
17: 082105.Google Scholar
and (2005). Classical Electricity and Magnetism, Dover Publications, New York.
and (1987). Use of breakup time data and velocity history data to predict the maximum size of stable fragments for acceleration-induced breakup of a liquid drop, Int. J. Multiph. Flow
13: 741–757.Google Scholar
, and (2010). Liquid encapsulation by binary collisions of immiscible liquid drops, Colloid Surf. A-Physicochem. Eng.
365: 89–94.Google Scholar
and (2012). Microphysics of Clouds and Precipitation: Reprinted 1980, Springer, Heidelberg.
and (1997). Regimes of coalescence and separation in droplet collision, J. Fluid Mech.
331: 59–80.Google Scholar
(1882). On the equilibrium of liquid conducting masses charged with electricity, Phil. Mag.
14: 184–186.Google Scholar
(1978). Atomization and other Breakup Regimes of a Liquid Jet, PhD thesis, Princeton University.
and (2011). Crossover between Rayleigh-Taylor instability and turbulent cascading atomization mechanism in the bag-breakup regime, Phys. Rev. E
84: 016318.Google Scholar
, and (2002). Time evolution of liquid drop impact onto solid, dry surfaces, Exp. Fluids
33: 112–124.Google Scholar
and (1980). The influence of liquid film thickness on airblast atomization, J. Eng. Power
102: 706–710.Google Scholar
(2004). Dynamics of inertia dominated binary drop collisions, Phys. Fluids
16: 3438–3449.Google Scholar
(2009). Inertia dominated drop collisions II: an analytical solution of the Navier- Stokes equations for a spreading viscous film, Phys. Fluids
21: 052104.Google Scholar
, and (2009). Inertia dominated drop collisions I: on the universal flow in the lamella, Phys. Fluids
21: 052103.Google Scholar
, and (2006). Spray impact: rim transverse instability initiating fingering and splash, and description of a secondary spray, Phys. Fluids
18: 102104.Google Scholar
, , and (2012). Binary collisions of drops of immiscible liquids, J. Fluid Mech.
690: 512–535.Google Scholar
, and (1992). Colloidal Dispersions, Cambridge University Press.
, and (1999). Drop formation at the surface of plane turbulent liquid jets in still gases, Int. J. Multiph. Flow
25: 1161–1180.Google Scholar
and (2003). Surface properties during primary breakup of turbulent liquid jets in still air, AIAA J.
41: 1514–1524.Google Scholar
(1992). Theoretische und experimentelle Untersuchung der Instabilität turbulenter Kapillarstrahlen, PhD thesis, Technische Universität Darmstadt.
(1926). Die Grössenbestimmung der im Gemischnebel von Verbrennungskraftmaschinen vohrhandenen Brennstoffteilchen:(Mitteilung aus dem Laboratorium für Technische Physik der Technischen Hochschule München), VDI-Verlag.
(1997). Electrohydrodynamics: the Taylor-Melcher leaky dielectric model, Annu. Rev. Fluid Mech.
29: 27–64.Google Scholar
and (2003). Boundary-Layer Theory, Springer, Heidelberg.
(2003).Modeling droplet breakup in complex two-phase flows (Paper 2–19), ICLASS Conference, Sorento, Italy.
and (1973). The splitting of drops and bubbles by turbulent fluid flow, J. Fluids Eng.
95: 53–60.Google Scholar
(2009). Charge Injection Systems – Physical Principles, Experimental and Theoretical Work, Springer, Heidelberg.
and (2000). Review of theory of distortion and disintegration of liquid streams, Progr. Energy Comb. Sci.
26: 609–655.Google Scholar
, and (2009). Mechanism study of deformation and mass transfer for binary droplet collisions with particle method, Phys. Fluids
21: 032106.Google Scholar
, , and (1998). Effects of cavitation and internal flow on atomization of a liquid jet, Atom. Sprays
8: 179–197.Google Scholar
(1959a). The dynamics of thin sheets of fluid II. Waves on fluid sheets, Proc. R. Soc. London Ser. A-Math.
253: 296–312.Google Scholar
(1959b). The dynamics of thin sheets of fluid III. Disintegration of fluid sheets, Proc. R. Soc. London Ser. A-Math.
253: 313–321.Google Scholar
(2011). Aerobreakup of Newtonian and viscoelastic liquids, Annu. Rev. Fluid Mech.
43: 661–690.Google Scholar
and (2009). Single-drop fragmentation determines size distribution of raindrops, Nat. Phys.
5: 697–702.Google Scholar
(1931). Zum Zerfall eines Flüssigkeitsstrahles, ZAMM-J. of Appl.Math. Mech.
11: 136–154.Google Scholar
(1990). Deformation and breakup of liquid drops in a gas stream at nearly critical Weber numbers, Exp. Fluids
9: 59–64.Google Scholar
and (2003). Binary droplet collisions in a vacuum environment: an experimental investigation of the role of viscosity, Exp. Fluids
34: 28–41.Google Scholar
(2013). Zerstäubungstechnik: Prinzipien, Verfahren, Geräte, Springer, Heidelberg.
and (1993). Aerodynamic effects on primary breakup of turbulent liquids, Atom. Sprays
3: 265–289.Google Scholar
, and (1995). Effects of initial flow conditions on primary breakup of nonturbulent and turbulent round liquid jets, Atom. Sprays
5: 175–196.Google Scholar
(1993). Free Liquid Jets and Films: Hydrodynamics and Rheology, Longman and John Wiley & Sons, Harlow and New York.
, and (2014). Fundamentals and Applications of Micro- and Nanofibers, Cambridge University Press.
and (1995). Impact of drops on solid surfaces: self-similar capillary waves, and splashing as a new type of kinematic discontinuity, J. Fluid Mech.
283: 141–173.Google Scholar
, , and (2002). Acoustically levitated drops: drop oscillation and break-up driven by ultrasound modulation, Int. J. Multiph. Flow
28: 887–910.Google Scholar
, and (1953). The mechanism of disintegration of liquid sheets, Trans. ASME
75: 1279–1286.Google Scholar