Swirling jets

Pulverized fuel combustion swirl jets improve particle residence time in the combustion zone, and consequently improve combustion efficiency. Increasing the swirl number and thereby the jet angle moves 

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A supply jet may have several different forms point jet, swirl jet, line jet, radial jet, etc. The choice depends on available volume and existing demands. A radial jet could be used when it is possible to utilize a wall or a ceiling for distributing the air a point jet could be used when it is advantageous to have a high air velocity in the volume (room). 

The behavior of a rotating sphere or hemisphere in an otherwise undisturbed fluid is like a centrifugal fan. It causes an inflow of the fluid along the axis of rotation toward the spherical surface as shown in Fig. 1(a). Near the surface, the fluid flows in a spirallike motion towards the equator as shown in Fig. 1(b) and (c). On a rotating sphere, two identical flow streams develop on the opposite hemispheres. The two streams interact with each other at the equator, where they form a thin swirling jet toward the bulk fluid. The Reynolds number for the rotating sphere or hemisphere is defined as ... 

Wang et al. [72] investigated the combination of swirling jet-induced hydrodynamic cavitation and hydrogen peroxide for decomposition of rhodamine B in... 

Wang X, Wang J, Guo P, Guo W, Li G (2008) Chemical effect of swirling jet-induced cavitation Degradation of rhodamine B in aqueous solution. Ultrason Sonochem 15 357-363... 

Atomization of melts has, in principle, some similarity to the atomization of normal liquids. The atomization processes originally developed for normal liquids, such as swirl jet atomization, two-fluid atomization, centrifugal atomization, effervescent atomization, ultrasonic piezoelectric vibratory atomization, and Hartmann-whistle acoustic atomization, have been deployed, modified, and/or further developed for the atomization of melts. However, water atomization used for melts is not a viable technique for normal liquids. Nevertheless, useful information and insights derived from the atomization of normal liquids, such as the fundamental knowledge of design and performance of atomizers, can be applied to the atomization of melts. 

In internal mixing atomization (for example centrifugal-pneumatic atomization), 159] the liquid metal and gas enter the swirl jet atomizer tangentially under pressure (Fig. 2.13)J159] The two fluids rotate, form a mixture, and accelerate in the confuser. Due to the strong centrifugal force, the liquid metal forms a film at the nozzle exit even without the presence of the gas. With the applied gas, the liquid film is atomized into a fine dispersion of droplets outside the nozzle. 

The liquid properties of primary importance are density, viscosity and surface tension. Unfortunately, there is no incontrovertible evidence for the effects of liquid viscosity and surface tension on droplet sizes, and in some cases the effects are conflicting. Gas density is generally considered to be the only thermophysical property of importance for the atomization of liquids in a gaseous medium. Gas density shows different influences in different atomization processes. For example, in a fan spray, or a swirl jet atomization process, an increase in the gas density can generally improve... 

P. Billant, J.-M. Chomaz, and P. Huerre. Experimental study of vortex breakdown in swirling jets. J. Fluid Mech., 376 183-219, 1998. 

Gibson M.M. and Younis (1986) Calculation of swirling jets with a Reynolds stress closure, Physics of Fluids, 29, 38-48. 

Also, in collaborative efforts with Mashayek s group at the University of Illinois at Chicago, a generalized finite-volume LES code is under development which will be used for simulations of droplet dispersion, evaporation, and combustion in a dump combustor and swirl jet burner. 

Mathur and Maccallum [18] have reported results of their experimental work done on hubless and annular vane swirlers for pressure drop across swirler, axial static pressure, and axial and tangential velocity components distribution. It was concluded that the swirling jets experienced a sudden expansion downstream of the swirl generators. An internal recirculation zone (IRZ)... 

Confined swirl jet internal (primary) and external (secondary) Recirculation Zones. (From Kutz, M., Mechanical Engineer s Handbook, 3e, Book 4, Energy Power, New York John Wiley, 2006. With permission.)... 

The definition of the swirl number provided by Chigier and Beer [44] did not completely characterize the confined swirl jets, because in the case of furnaces downstream of a swirl generator, the swirl flow depends on other parameters such as burner quad or combustion chamber dimensions. 

Devices that spray liquids are called atomizers. They are classified as direct-jet atomizers, which create a cylindrical jet, and centrifugal atomizers, which create a swirling jet with a gas core inside. A thin liquid cylindrical layer (sheet) is formed at the exit of a centrifugal atomizer and then expands in the radial direction as... 

Another BEM modeling of a jet in the atomization regime was done by Park and Heister [24]. They simulated a swirling jet by using the superposition theory, which implements a complex potential containing a vortex. This potential vortex provides a vortical flow that acts as the circumferential pressure caused by the swirling. Annular ligaments pinched from the parent surface are presumed to break into the... 

As compared to the jet-spouted bed dryer of inert particles used for drying of detergents and dyestuffs, backmixing of inert particles along with swirl-jet spouting allows for the following (Markowski et al., 1978) ... 

Table 4.3 Performance Characteristics of the Swirling-Jet-Spouted Bed Dryer...

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