Annular jet

In some practical applications of air supply (e.g., multiple-jet ceiling diffusers, an annular jet collapsing into a compact jet, jets from rectangular outlets becoming round or elliptical, or multiple streams merging when air is supplied through perforated panels), measurements and accurate jet description in Zone 1 and Zone 2 may be difficult. 

The mechanism is based on strong cooling of the products adjacent to the walls and injection of the cooled products in the form of an annular jet behind the flame, reducing its width as soon as the speed of the annular jet, proportional to the circumferential speed of the gas at the flame location becomes larger than the propagation speed of the edge flame. 

Relative Angle between Water Nozzle and Metal Delivery Nozzle (°) 40-60 (Annular Jet) 15-35 (V Jets)... 

In the empirical correlation proposed by Kato et al.,[503] the mean droplet size is inversely proportional to the water pressure, with a power index of 0.5 for conical shaped annular-jet atomizers, and 0.7-1.0 for V-shaped flat-jet atomizers. This suggests a lower efficiency of the annular-jet atomizers in terms of spray fineness at high water pressures. The data of Kato et al.15031 were obtained for water pressures lower than 10 MPa. Seki et al.15021 observed the similar trend in the water atomization of nickel and various steels at higher water pressures (>10 MPa). Since k is dependent on both... 

For a stationary spray without scanning, a Gaussian shaped mass distribution typically develops with an annular-jet or discrete-jet atomizer. The radial mass distribution in the spray can be formulated in terms of mass flux)632]... 

Annular jet. This technology was developed by the Southwest Research Institute and has not been extensively used in the food industry (10). It relies upon two concentric jets. The inner jet contains the liquid core material. The outer jet contains the liquid wall material, generally molten, that solidifies upon exiting the jet. This dual fluid stream breaks into droplets much as water does upon exiting a spray nozzle ... 

The contour plots of Fig. 10.3 were averaged circumferentially to produce radial profiles of the axial and tangential velocity components as shown in Fig. 10.4 for Swirler 504545 at c// = 0.1. The locations of the peak velocity of the mean and tangential components are at r/R = 0.9 and r/R = 0.95. The peaks of the rms velocity of the two components are at nearly the same locations dXr/R — 0.6, where the shear layer of the annular jet is located. The CTRZ has a radius of r/R = 0.5, which is primarily contributed by the inner swirler and partially by the intermediate swirler. 

The latter cases were selected because they exhibited the more approximately axisymmetric TARS outlet features. The simulations are capable of capturing the main features of the flow, including the initial shape of the recirculation zone, its lateral extent, and the development of the annular jet. More detailed comparisons between LES and LDV for Case I are shown in Fig. 11.96, in terms of radial profiles of the mean value and rms axial velocity at selected cross-stream locations. Disagreements between LDV and LES velocity data are more noticeable in terms of the rms axial velocity distributions, largely reflecting on the neglected inlet turbulent intensities in the simulations, as well as on the needed improved emulation of the laboratory inlet conditions with regards to azimuthal mean velocity variations, turbulence statistics, and spectral content. 

The second rig was the premixed combustor shown in Figure 15.2. A quartz tube (L = 250 mm, i.d. = 120 mm) configures the combustion chamber and allows for unrestricted optical access to the flame. The fuel-air mixture is injected as a swirling annular jet (o.d. = 40 mm, i.d. = 25 mm, 60° axial vanes). The fuel issues through 12 radial orifices, located 320 mm upstream of the chamber. All tests reported had a thermal input of 32 kW. In this case, the ER was varied in the range from... 

Annular Jet Process Centrifugal suspension separation Coacervation and phase separation Cocrystallization Controlled precipitation Dispersion/suspension polymerization Dripping and jet break up Electrospraying... 

There are a number of process technologies used for annular jet processes. While there are some dominant ones, some smaller or niche processes should not be completely unmentioned. However, as the market is moving and evolving, it is not possible to give a complete overview about technologies, but the interested reader may inform himself by regularly visiting conferences and access the well-established Journals to find out about newer developments. 

At the current time, the annular jet processes most commonly used in food, pharma, cosmetic, and chemistry that produce particles of one or another kind are certainly laminar flow breakup processes. It has to be kept in mind, that the absolute majority of annular jet processes are used in other fields—as fuel engines—or to produce matrix particles, as two material nozzles used in atomization. Those, however, will not be subject to this chapter. 

A special niche annular Jet-based process is the flow focusing technology. Here, instead of using a liquid shell material, a matrix sphere is produced, but the outer nozzle is operated with an inert... 

For the production of core-shell encapsulated products, annular jet processes offer a large number of advantages. Already a vast amount of products is produced using these processes, ranging from chewing gums, tobacco, medical products, supplements to electronic, and chemical applications. 

Annular Jet processes are used widely in industries. A special interest and growing application are processes to produce Micrcapsules with annular gap nozzles. A selection of those processes is presented in this chapter. 

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