1070-4272/01/7403-0455$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 3, 2001, pp. 455! 460. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 3,
2001, pp. 445!450.
Original Russian Text Copyright + 2001 by Aniskin, Protod’yakonova.
PROCESSES AND EQUIPMENT
OF CHEMICAL INDUSTRY
Hydrodynamic Model of a Free Jet of Atomized Fluid
S. V. Aniskin and O. I. Protod’yakonova
St. Petersburg State Technological University of Plant Polymers, St. Petersburg, Russia
Received December 20, 2000
Abstract-The formation and development of a gas3fluid jet outflowing from a single-flare atomizer of
a spray absorber are analyzed theoretically, and a hydrodynamic model taking into account the nonuniformity
of spraying density and gas flow velocity across the jet is developed on the basis of this analysis.
Developing methods for calculating mass-exchange
processes in spraying apparatus requires a detailed
theoretical study of jet flows. Such flows occur, in
particular, in direct-flow spray absorbers.
One of important kinds of jet flows is a flow of
drops formed in spraying a fluid with a single-flare
atomizer. It is known that a gas jet is always formed
inside such a drop flow. Thus, the jet of atomized
fluid, considered as a whole, is a gas3fluid jet.
The main distinction of single-jet atomizers is that
fluid drops are present within the entire flare cone.
Let us represent the structure of the jet flow under
consideration as the following scheme (Fig. 1). The
gas3fluid jet is conventionally divided into three
zones. In the first zone, the fluid jet outflowing from
the atomizer 1 is deformed and then disintegrates into
drops and some coarse formations of indeterminate
shape, which, in turn, also disintegrate into large and
fine drops. There are no formations of this kind in
the second and third zones, and inclusions of the
disperse phase are only composed of large and fine
drops. The mechanisms of interaction between phases
are different in these zones.
As the gas3fluid jet moves, its flare expands, with
the volume density of the fluid phase, corresponding-
b = ÄÄÄÄÄÄ, (1)
are, respectively, the fluid and gas
volumes in the gas3fluid jet.
In the initial part of the first zone, the forming
drops are so close to one another that their hydro-
dynamic boundary layers come in contact. This gives
rise to a certain structure of interconnected fluid phase
inclusions, with the motion of gas through this struc-
ture comparable with the filtration process.
In the final part of the first zone, beginning with
the instant when the b value becomes approximately
equal to 0.02 , there is no mutual influence of
drops any more and they move further entirely in-
dependently of one another. In this case, the momen-
tum exchange between the fluid and the gas will
depend on the size, shape, and relative velocities of
drops and of fluid formations whose disintegration
into drops continues in the flow zone in question.
In accordance with the results obtained in experi-
mental studies of the hydrodynamics of the gas3fluid
jet by the photographic method , the mentioned
disintegration is complete at the instant when b
becomes 0.003. It should be noted that the estimated
b values at which moving drops cease to affect one
another may be somewhat different for atomizers of
special types. For example, for atomizers in which
Fig. 1. Structure of gas3fluid jet in fluid spraying with
a single-flare atomizer: (1) atomizer and (I!III) jet zones.