Spray cone

Spray cleaning, of metal surfaces, 16 213 Spray coating processes, 7 23, 68-76 economic aspects, 7 75-76 Spray column absorbers, 1 27 Spray cone angle, 23 187 Spray correlations, 23 189-192 Spray deposition, of metal-matrix composites, 16 173 Spray-dried products, 11 542-543 Spray-dried resins, production of,... 

Pressure Atomization Plain- Orifice 25-250 Diesel engines, Jet engine afterburners, Ramjets Simple, Rugged, Cheap Narrow spray angle, Solid spray cone... 

One of the limitations of plain-orifice atomizers is the narrow spray cone generated. For most practical applications, large spray cone angles are desired. To achieve a wide spray cone, a simplex, i.e.,... 

Solid-cone spray atomizers usually generate relatively coarse droplets. In addition, the droplets in the center of the spray cone are larger than those in the periphery. In contrast, hollow-cone spray atomizers produce finer droplets, and the radial liquid distribution is also preferred for many industrial applications, particularly for combustion applications. However, in a simplex atomizer, the liquid flow rate varies as the square root of the injection pressure. To double the flow rate, a fourfold increase in the injection pressure is... 

Various correlations for mean droplet size generated using pressure-swirl and fan spray atomizers are summarized in Tables 4.4 and 4.5, respectively. In the correlations for pressure-swirl data, FN is the Flow number defined as FN = ml/APlpl) )5, l0 and d0 are the length and diameter of final orifice, respectively, ls and ds are the length and diameter of swirl chamber, respectively, Ap is the total inlet ports area, /yds the film thickness in final orifice, 6 is the half of spray cone angle, and Weyis the Weber number estimated with film... 

As ambient air pressure is increased, the mean droplet size increases 455 " 458] up to a maximum and then turns to decline with further increase in ambient air pressure. ] The initial rise in the mean droplet size with ambient pressure is attributed to the reduction of sheet breakup length and spray cone angle. The former leads to droplet formation from a thicker liquid sheet, and the latter results in an increase in the opportunity for droplet coalescence and a decrease in the relative velocity between droplets and ambient air due to rapid acceleration. At low pressures, these effects prevail. Since the mean droplet size is proportional to the square root of liquid sheet thickness and inversely proportional to the relative velocity, the initial rise in the mean droplet size can be readily explained. With increasing ambient pressure, its effect on spray cone angle diminishes, allowing disintegration forces become dominant. Consequently, the mean droplet size turns to decline. Since ambient air pressure is directly related to air density, most correlations include air density as a variable to facilitate applications. Some experiments 452] revealed that ambient air temperature has essentially no effect on the mean droplet size. 

Liu et aU622] used a laser Doppler velocity and size (LDVS) measurement technique to determine the local size, velocity, and number flow density of droplets in the spray cone during spray deposition of a liquid steel. The experimental setup is schematically depicted in Fig. 6.7.1615] The measured results showed that smaller... 

Several empirical relations have been proposed to express drop size in terms of the operating variables. One suitable for small atomisers with 85° spray cone angles, at atmospheric pressure is(34) ... 

The droplet number density presented in Fig. 16.4 indicates the solid-cone nature of the spray except in the immediate vicinity downstream of the nozzle exit. On the spray centerline at 2 = 10 mm, steam provides a lower number density as compared to the two air cases. This is due to the expansion of the spray jet at a relatively lower Reynolds number with steam and rapid vaporization of smaller sized droplets. At increased radial positions and 2 = 10 mm, a peak in the number density corresponds to the spray cone boundary. This peak shifts radially outwards with an increase in axial distance due to the expansion of the spray cone. Similar phenomena are observed for the normal and preheated air cases except that droplet number density for the preheated air case is much higher on the spray central axis (at r = 0). This is attributed to the effect of preheated air on atomization (i.e., larger mean droplet size and smaller number density with normal air as compared to that for heated atomization... 

Inlet air dew point Nozzle spray cone angle... 

D = nozzle diameter (m) g = gravitational acceleration (m/sec2) a = angle between the spray cone and the vertical... 

I he experimental investigation of the combustion of sprays is complicated by the many variables involved. Common sprays are composed of a wide range of droplet sizes distributed unevenly in the spray cone. Turbulence of the air and the relative motion of the droplets through the air are poorly defined. The burning of an isolated droplet itself presents a difficult problem, although much progress has been made in this field in the past few years. To study the effect of any single variable on the combustion characteristics of a spray, other variables must be held constant. This paper reviews those fields of effort in which work has been done to simplify the complex physical aspects of this problem. 

The rate of depth of penetration of a spray tip into a chamber is found by Gelalles (4C) to be a function of the ratio of length to diameter. Using pressures ranging from 2000 to 8000 pounds per square inch and a plain stem ahead of the orifice, maximum penetration rates have been obtained for L/D ratios between 4 and 6. The spray cone angle increases with the ratio of the orifice area to the groove area. Others who have conducted detailed investigations on spray formation include Doble (3C), Lee (9C, IOC), and Rothrock and Waldron (20C). 

Reasonable correlations of combustion efficiency with fuel spray momentum and spray energy in two different combustors have been shown to hold over a range of altitude-engine idling conditions 133). As different curves were obtained with different injector nozzles, spray-cone angle was thought to be a factor. Further work showed that efficiency did correlate closely with expressions representing the spray momentum or... 

Figure 1. Drop size vs. viscosity using Spray cone WG 4008...

The twin-fluid atomizer used here and described elsewhere (8) is based on the above principle in which liquid fuel and air are forced through a nozzle and emerge from the oriflce in the form of a spray cone. A schematic of the atomizer is shown in Figure 1. 

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