Atomizers air-assisted

Air-assisted atomizer Air-atmosphere furnaces Air bag fabric Airbags... 

In air-assist atomization, air is needed usually to augment the atomization process only at low liquid flow rates when the pressure differential is too low to produce satisfactory pressure atomization. In some designs, however, air assistance may be required over the entire range of operating conditions if the atomization quality achieved with a pressure atomizer alone is always poor. In an air-assist atomization process, the impingement of a low-velocity liquid stream by a high-velocity air stream may occur either within or outside the... 

Various correlations for mean droplet sizes generated by air-assist atomizers are given in Table 4.6. In these correlations, mA is the mass flow rate of air, h is the height of air annulus, tf0 is the initial film thickness defined as tj ) = dQw/dan, d0 is the outer diameter of pressure nozzle, dan is the diameter of annular gas nozzle, w is the slot width of pressure nozzle, C is a constant related to nozzle design, UA is the velocity of air, and MMDC is the modified mean droplet diameter for the conditions of droplet coalescence. Distinguishing air-assist and air-blast atomizers is often difficult. Moreover, many... 

Table 4.6. Correlations for Mean Droplet Size Generated by Air-Assist Atomizers...

Internal mixing air-assist atomizer. Derived from wax spray data in Ref. 461 using NOTE atomizer Good agreement with fuel-air or fiiel-steam spray data 11031 Discrepant with water-air spray data 179114621 MMD is to be multiplied by an empirical correction factor for conditions of droplet coalescence. 

Internal-mixing air-assist atomizer. Derived from water-air spray data mT... 

External-mixing air-assist atomizers. Derived from ethanol (glycerin)-air spray data with initial thickness of flat circular sheet up to 0.7 mm and varied air impingement angles Sampled with oil-coated slides... 

Pressure and air-assist atomizers. Derived from calibrating fluid (MIL-F-7041 l)-air spray data using Parker Hannifin spray analyzer... 

Similarly to pressure-swirl atomization and air-assist atomization, the mean droplet size is proportional to liquid viscosity and surface tension, and inversely proportional to air velocity, air pressure, air density, relative velocity between air and liquid, and mass flow rate ratio of air to liquid, with different proportional power... 

Effective atomization plays an important role in efficient combustion as well as in influencing the pattern factor. Atomization of kerosene with steam rather than with air as the atomization fluid is presented by Ashwani Gupta, of the University of Maryland, and his colleagues using a commercially available air-assist atomizer. The results suggest that, because of the higher viscosity of... 

Aftel, R., A. K. Gupta, C. Cook, and C. Presser. 1997. Gas property effects on droplet atomization and combustion in an air-assist atomizer. 26th Symposium (International) on Combustion Proceedings. Pittsburgh, PA The Combustion Institute. 1645-51. 

A visualization study of fuel atomization using a pulsed laser holography/photography technique indicates that basic spray formation processes are the same for both a coal-derived synthetic fuel (SRC-II) and comparable petroleum fuels (No. 2 and No. 6 grade). Measurements were made on both pressure swirl and air assisted atomizers in a cold spray facility having well controlled fuel temperature. Quality of the sprays formed with SRC-II was between that of the No. 2 and No. 6 fuel sprays and was consistent with measured fuel viscosity. Sauter mean droplet diameter (SMD) was found to correlate with fuel viscosity, atomization pressure, and fuel flow rate. For all three fuels, a smaller SMD could be obtained with the air assisted than with the pressure swirl atomizer. 

FIGURE 5 Schematic and image of a twin-fluid, air-assist atomizer. 

Varga CM, Snyder HE. Impact of liquid viscosity on droplet sizes produced from air-assist atomizers. Institute for liquid atomization and spraying systems conference. Monterey, California. 2003. 

F.X. Tanner, K.A. Feigl, T.O. Althaus, and E.J. Windhab. Modeling and simulation of an air-assist atomizer for food sprays. In Proc. 21st ILASS-Americas Aimual Conference, Orlando, May 2008. CD ROM Publication. 

Several types of injectors have been investigated for delivering the fuel. These include pressure-swirl atomizers, air-assisted atomizers, and single-hole and multihole injectors delivering solid-cone sprays. Injection pressures vary depending on the type of injector, but they are generally less than 20 MPa. In the case of solid-cone sprays, drop SMDs vary from about 50 pm at about 2 MPa to 15 pm at about 10 MPa. Air-assisted injectors typically deliver smaller diameters. Pressure-swirl atomizers can generate drops that are about 20 pm at about 5 MPa. 

Principal concern of this study was to understand and limit the dispersing characteristics of an emulsion treated by an air-assisted atomizer, where consequently the interfacial tension plays another important role. Dispersion or breakup of the internal emulsion droplets (primary or secondary) during spraying is mainly a function of interfacial tension (determining the energy required to deform and increase the interface) and the viscous flow stresses (depending on the applied velocity field and the viscosity ratio A of dispersed to continuous phase). Therefore, interfacial tension was measured for SEs (SE interface between continuous and disperse fluid phases) and DEs (DE interface between continuous and dispersed... 

Spray Processing Experiments Using Air-Assisted Atomizer... 

Fig. 23.9 Schematic diagram of twin-fluid (air-assisted) atomizer with intranal mixing (INMIX, / ) and external mixing (EXMIX, right) of gas and liquid phases...

Table 23.5 Specification of air assisted atomizers (liquid and air cap diameters)...

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