Note: Descriptions are shown in the official language in which they were submitted.
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DEVICE AND METHOD FOR AERATION OF FLUIDS
FIELD OF THE INVENTION
The invention relates generally to the field of small particle formation and
more
_'~ specifically to fields where it is important to create gas bubbles which
are very small and
uniform in size.
BACKGROUND OF THE INVENTION
Monodispersed sprays of droplets of micrometric size have attracted the
interest of
10~ scientist, and engineers be~.cause of their potential applications in many
fields of science and
technology. Classifying a polydispersed aerosol (for example, by using a
differential
mobility analyzer, B.Y. Liu et al. (1974), "A Submicron Standard and the
Primary
Absolute Calibration of the Condensation Nuclei Counter," J. Coloid Interface
Sci.
42:155-171 or breakup process of Rayleigh's type of a capillary microjet Lord
Rayleigh
15 (1879), "On the instability of Jets," Proc. London Math. Soc. 1Q:4-13, are
the cwrent
methods to produce the mionodispersed aerosols of micrometric droplets needed
for such
applications. The substantial loss of the aerosol sample during the
classification process
can severely limit the use of this technique for some applications. On the
other hand,
although in the capillary break up the size distribution of the droplets can
be very narrow,
20 the diameter of the droplets is determined by the jet diameter
(approximately twice the jet
diameter). Therefore, the generation and control of capillary microjets are
essential to the
production of sprays of micrometric droplets with very narrow size
distribution.
Capillary microjets with diameters ranging from tens of manometers to hundred
of
micrometers are successfully generated by employing high electrical fields
(several kV) to
25 form the well-known cone jet electrospray. Theoretical and experimental
results and
numerical calculations on electrosprays can be obtained from M. Cloupean et
al. (1989),
"Electrostatic Spraying of Liquids in Cone Jet Mode," J. Electrostat ?~: I35-
159,
Fernandez de la Mora et ta. (1994), "The Current Transmitted through an
Electrified
Conical Meniscus," J. Fltcid Mech.2~:155-184 and Loscertales (1994), A.M.
Gai~n-
30 Calvo et al. (1997), "Current and Droplet Size in the Electrospraying of
Liquids: Scaling
Laws," J. Aerosol Sci. ?".$:249-275, Hartman et al. (1997),
"Electrohydrodynamic
Atomization in the Cone-Jet Mode," Paper presented at the ESF Workshop on
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Electrospray, Sevilla, 2t3 Feb.-1 Mar. 1997 among others [see also the papers
contained in
the Special Issue for Electrosprays (1994)J. In the electrospray technique the
fluid to be
atomized is slowly injected through a capillary electrified needle. For a
certain range of
values of the applied voltage and flow rate an almost conical meniscus is
formed at the
needle's exit from whose vertex a very thin, charged jet is issued. The jet
breaks up into a
fine aerosol of high charged droplets characterized by a very narrow droplet
size
distribution. Alternatively, the use of purely mechanical means to produce
capillary
microjets is limited in most of applications for several reasons: the high-
pressure values
required to inject a fluid through a very narrow tube (typical diameters of
the order of few
1~~ micrometers) and the ea,4y clogging of such narrow tubes due to impurities
in the liquid.
The present invention provides a new technique for producing uniform sized
monodispersion of gas bubbles based on a mechanical means which does not
present the
above inconveniences and can compete advantageously with electrospray
atomizers. The
jet diameters produced with this technique can be easily controlled and range
from below
l.'i one micrometer to several tens of micrometers.
SUMMARY OF THE INVENTION
The present invention provides aeration methods using spherical gas bubbles
having
a size on the order of 0.1 to 100 microns in size. A device of the invention
for producing
2C~ a monodispersion of bubbles includes a source of a stream of gas which is
forced through
a liquid held under pressure in a pressure chamber with an exit opening
therein. The
stream of gas surrounded by the liquid in the pressure chamber flows out of an
exit orifice
of the chamber into a liquid thereby creating a monodispersion of bubbles with
substantially uniform diameter. The bubbles are small in size and produced
with a
25 relatively small amount of energy relative to comparable systems.
Applications of the
aeration technology range from oxygenating sewage with monodispersions of
bubbles to
oxygenation of water for fish maintenance.
BRIEF DESCRIPTION OF THE DRAWINGS
30 Figure 1 is a schematic view showing the basic components of one embodiment
of
the invention with a cylindrical feeding needle as a source of formulation.
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Figure 2 is a schematic view of another embodiment of the invention with two
concentric tubes as a source of formulation.
Figure 3 is a schematic view of yet another embodiment showing a wedge-shaped
planar source of formulation. Figure 3a illustrates a cross-sectional side
view of the planar
feeding source and the interaction of the fluids. Figure 3b show a frontal
view of the
openings in the pressure chamber, with the multiple openings through which the
atomizate
exits the device. Figure 3c illustrates the channels that are optionally
formed within the
planar feeding member. The channels are aligned with the openings in the
pressure
chaunber.
Figure 4 is a schematic view of a stable capillary microjet being formed and
flowing
through an exit opening t:o thereafter form a monodisperse aerosol.
Figure 5 is a graph of data where 3 SO measured values of d ldo versus QIOo
are
plotted.
Figure 6 is a micrograph showing the even dispersement and uniform size of air
1.'i bubbles created using the; method of the invention after expulsion into
air.
Figure 7 is a schematic view of the critical area of a device of the type
shown in
Figure 1 showing gas surrounded by liquid expelled into a liquid to form
bubbles.
Figure 8 is a schematic view as in Figure 7 but with the bubbles flowing into
a gas.
Figure 9 is a schematic view as in Figure 7 but with two immiscible liquids
flowing
into a gas.
DETAILED DESCRIPTION OF PREFERRED EMBODIIVVIENTS
Before the present; aeration device and method are described, it is to be
understood
that this invention is not limited to the particular components and steps
described, as such
may, of course, vary. It is also to be understood that the terminology used
herein is for the
purpose of describing particular embodiments only, and is not intended to be
limiting, since
the scope of the present invention will be limited only by the appended
claims.
It must be noted that as used herein and in the appended claims, the singular
forms
"a", "and," and "the" include plural referents unless the context clearly
dictates otherwise.
Thus, for example, reference to."a bubble" includes a plurality of bubbles and
reference to
"a gas " includes reference to a mixture of gases, and equivalents thereof
known to those
skilled in the art, and so forth.
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Unless defined otherwise, all technical and scientific terms used herein have
the
same meaning as commonly understood by one of ordinary skill in the art to
which this
invention belongs. Although any methods and materials similar or equivalent to
those
described herein can be used in the practice or testing of the present
invention, the preferred
methods and materials we now described. All publications mentioned herein are
incorporated herein by reference to disclose and describe the methods and/or
materials in
connection with which the publications are cited.
The publications discussed herein are provided solely for their disclosure
prior to the
filing date of the present application. Nothing herein is to be construed as
an admission that
1 n the present invention is not entitled to antedate such publication by
virtue of prior invention.
Further, the dates of publication provided may be different from the actual
publication dates
which may need to be independently confirmed.
DEF1IVITIONS
The terms "bubble", "dispersion of bubbles" and "monodispersion of bubbles"
are
used interchangeably herein and shall mean small uniformly sized particles of
a gas or
gaseous formulation that has been dispersed using the device and method of the
invention.
The particles are generally spherical, and may be comprised of one or more
gases or layers
of gases.
The terms "air", "particle free air" and the like, are used interchangeably
herein to
describe a volume of air which is substantially free of other material and, in
particular,
free of particles intentionally added such as particles of formulation. Air is
a mixture of
various gas components That may, of course vary, but usually the air will
contain
approximately 21 °& oxygen by volume. Air may also contain gases or
other air-borne
25~ particles. For use in the invention, air may be filtered or treated to
remove all unwanted
particulate or gaseous matter, or the air may be used in an unfiltered state.
Air is the
preferred gas for use of the invention in oxygenation of aqueous fluids, e.g.
water.
The terms "gas" and "gas formulation" as used herein refer to any gas or
gaseous
mixture which is desired to be dispersed using the method of the invention.
For example,
30~ the formulation may be comprised of air, either filtered or unfiltered.
Gases such as air
may be spiked with a particular gas, such as the spiking of air with
additional 02 gas for
use in oxygenation. A g~~seous formulation may also contain suspended
particlulate matter
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dispersed within the gas. The gas can be CO2 to carry out the carbonation of
beverages
(e.g. water, colas) or a gas containing an unwanted contaminant, e.g.
radioactivity or an
environmental toxin.
The term "aeration" as used herein refers to the dispersion of a gaseous
material
into a flowable fluid, for. example to provide a diffusion surface to
introduce a molecule or
compound from the gas into the flowable surface. The term is not limited to
the
dispersion of air per se, although the use of air is preferred, but rather
refers to the
introduction of any gas to a flowable fluid, e.g. 02, C02, hydrogen, nitrogen,
and the like
and mixtures thereof. 7;'he aeration of a fluid is preferably to allow
molecules and/or
1 n compounds to diffuse to the fluid through the fluid-bubble interface
following expulsion of
the bubbles from the device of the invention into the surrounding fluid. A
fluid may,
however, also be aerated. for aesthetic purposes, such as the addition of C02
to a beverage
to provide carbonation.
1'.~ DEVICE IN GENERAL
Different embodiments are shown and described herein (see Figures 1, 2 and 3)
which could be used in producing the stable capillary microjet and/or a
dispersion of
particles which are substantially uniform in size. Although various
embodiments are part
of the invention, they are: merely provided as exemplary devices which can be
used to
2(> convey the essence of the; invention, which is the formation of a stable
capillary microjet
and/or uniform dispersion of particles.
A basic device comprises {1) a means for supplying a first fluid, preferably a
gas,
and (2) a pressure chamber supplied with a second fluid which flows out of an
exit
opening in the pressure chamber, preferably a liquid. The exit opening of the
pressure
25~ chamber is aligned with the flow path of the means for supplying the first
fluid. The
embodiments of Figures 1, 2 and 3 clearly show that there can be a variety of
different
means for supplying the i:irst fluid. Other means for supplying a first fluid
flow stream
will occur to those skilled in the art upon reading this disclosure.
Further, other configurations for forming the pressure chamber around the
means
30~ for supplying the first fluid will occur to those skilled in the art upon
reading this
disclosure. Such other embodiments are intended to be encompassed by the
present
invention provided the basic conceptual results disclosed here are obtained,
i.e. a stable
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capillary microjet is formed and/or a dispersion of particle highly uniform in
size is
formed. To simplify the description of the invention, the means for supplying
a first fluid
is often referred to as a cylindrical tube (see Figure 1) and the first fluid
is generally
referred to as a gas. The gas can be any gas depending on the desired use of
the device,
although it is preferably air. For example, the gas could be air used to
create small
bubbles for aeration of a liquid to provide a gaseous medium through which
components
may diffuse into a liqui<i. Further, for purposes of simplicity, the second
fluid is generally
described herein as being a liquid, e.g. water. The invention is also
generally described
with a gas formulation teeing expelled from the supply means and forming a
stable
microjet due to interaction with surrounding water flow, which focuses the gas
microjet to
flow out of an exit of the pressure chamber.
Formation of the microjet and its acceleration and ultimate particle formation
are
based on the abrupt pressure drop associated with the steep acceleration
experienced by the
gas on passing through an exit orifice of the pressure chamber which holds the
second fluid
(i.e. the liquid). On leaving the chamber the flow undergoes a certain
pressure difference
between the liquid and the gas, which in turn produces a highly curved zone on
the liquid
surface near the exit port: of the pressure chamber and in the formation of a
cuspidal point
from which a steady microjet flows, provided the amount of the gas drawn
through the exit
port of the pressure chamber is replenished. Thus, in the same way that a
glass lens or a lens
of the eye focuses light to a given point, the flow of the liquid surrounds
and focuses the gas
into a stable microjet. The focusing effect of the surrounding flow of liquid
creates a stream
of gas which is substantially smaller in diameter than the diameter of the
exit orifice of the
pressure chamber. This allows the gas to flow out of the pressure chamber
orifice without
touching the orifice, providing advantages including the feature that the
diameter of the
2.'i stream and the resulting particles are smaller than the diameter of the
exit orifice of the
chamber. This is particularly desirable because it is difficult to precisely
engineer holes
which are very small in diameter.. Further, in the absence of the focusing
effect {and
formation of a stable interface cusp) flow of gas out of an opening will
result in particles
which have a diameter greater than the diameter of the exit opening.
The description provided here generally indicates that the gas leaves the
pressure
chamber through an exit orifice surrounded by the liquid and thereafter enters
into a liquid
surrounding environment which may be either a hydrophobic or hydrophilic
liquid. This
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configuration is particularly useful when it is necessary to create very small
highly uniform
bubbles which are moved into a liquid surrounding exit opening of the pressure
chamber.
The need for the formation of very small highly uniform bubbles into a gas
occurs in a
variety of different industrial applications. For example, water needs to be
oxygenated in
:> a variety of situations including small fish tanks for home use and large
volume fisheries
for industrial use. The additional oxygen can aid the rate of growth of the
fish and
thereby improve production for the fishery. In another embodiment, oxygen or
air
bubbles can be forced into liquid sewage in order to aid in treatment. In yet
another
application of the invention, contaminated gases such as a gas contaminated
with a
radioactive material can be formed into small uniformed bubbles and blown into
a liquid,
where the contamination in the gas will diffuse into the liquid, thereby
cleaning the gas.
The liquid will, of course, occupy substantially less volume and therefore be
substantially
easier to dispose of than contaminated toxic gas.
Those skilled in the art will recognize that variations on the different
embodiments
15~ disclosed below will be uaeful in obtaining particularly preferred
results. Specific
embodiments of devices are now described.
EMBODIIVVIENT OF FIGURE 1
A first embodiment of the invention where the supply means is a cylindrical
feeding needle supplying gas into a pressurized chamber of liquid is described
below with
reference to Figure 1.
The components of the embodiment of Figure 1 are as follows:
Feeding needle - also referred to generally as a fluid source and a tube.
2. End of thE; feeding needle used to insert the gas to be dispersed.
3. Pressure Chamber.
4. Orifice used as liquid inlet.
End of the; feeding needle used to evacuate the liquid to be atomized.
6. Orifice through which withdrawal takes place.
7. Atomizate (spray) - also referred to as aerosol.
D, = diameter of the feeding needle; Do = diameter of the orifice
through which the microjet is passed; a = axial length of the
orifice through which withdrawal takes place; H = distance
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from the feeding needle to the microjet outlet; Po = pressure
inside the chamber; Pa = atmospheric pressure.
Although the device can be configured in a variety of designs, the different
designs will all include the essential components shown in Figure 1 or
components which
perform an equivalent function and obtain the desired results. Specifically, a
device of the
invention will be comprised of at least one source of a first fluid (e.g., a
feeding needle
with an opening 2) into which a first fluid such as a gas formulation can be
fed and an exit
opening 5 from which flue gas can be expelled. The feeding needle l, or at
least its exit
opening 5, is encompassed by a pressure chamber 3. The chamber 3 has inlet
opening 4
In which is used to feed a second fluid (e.g. a liquid) into the chamber 3 and
an exit opening
6 through which liquid from the pressure chamber and gas from the feeding
needle 3 are
expelled. When the first fluid is a gas it is preferably expelled into a
liquid to create
bubbles.
In Figure 1, the feeding needle and pressure chamber are configured to obtain
a
1.'i desired result of producing bubbles wherein the particles are small and
uniform in size.
The bubbles have a size which is in a range of 0.1 to 100 microns. The
particles of any
given bubbles will all have about the same diameter with a relative standard
deviation of
10.01 ~ to t 30 ~ or more preferably t 0.01 % to t 10 °b . Stating that
bubbles will have
a diameter in a range of 1 to 5 microns does not mean that different bubbles
will have
20 different diameters and that some will have a diameter of 1 micron while
others of 5
microns. The bubbles in a given dispersion will all (preferably about
90°.b or more) have
the same diameter t 0.01'. ~ to t 30 ~ . For example, the bubbles of a given
dispersion
will have a diameter of 2 microns 10.01 ~ to t 10 % .
Such a uniform bubble monodispersion is created using the components and
25~ configuration as described above. However, other components and
configurations will
occur to those skilled in the art. The object of each design will be to supply
fluid so that it
creates a stable capillary microjet which is accelerated and stabilized by
pressure stress
exerted by the second fluid on the first fluid surface. The stable microjet
created by the
second fluid leaves the pressurized area (e.g., leaves the pressure chamber
and exits the
30~ pressure chamber orifice) and splits into particles or bubbles which have
the desired size
and uniformity.
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The parameter window used (i. e. the set of special values for the properties
of
the liquid used, flow-rate used, feeding needle diameter, orifice diameter,
pressure ratio,
etc.) should be large enough to be compatible with virtually any liquid
(dynamic
viscosities in the range fiom 10'5 to 1 kg m'ls'1); in this way, the capillary
microjet that
emerges from the end of the feeding needle is absolutely stable and
perturbations produced
by breakage of the jet cannot travel upstream. Downstream, the microjet splits
into evenly
shaped bubbles simply by effect of capillary instability (see, for example,
Rayleigh, "On
the instability of jets", Proc. London Math. Soc., 4-13, 1878), similar in a
manner to a
laminar capillary jet falling from a half-open tap.
When the stationary, steady interface is created, the capillary jet that
emerges
from the end of the bubble attached at the outlet of the feeding point is
concentrically
withdrawn into the nozzle. After the gas jet emerges from the attached bubble,
the gas is
accelerated by pressure forces exerted by the liquid stream, which gradually
decreases the
jet cross-section. Stated differently the liquid flow acts as a lens and
focuses and stabilizes
1.'i the gas microjet as it moves toward and into the exit orifice of the
pressure chamber.
When the first fluid of the invention is a gas, and the second fluid is a
liquid, the inertia of
the first fluid is low, and. the gas abruptly decelerates very soon after it
issues from the
cusp of the attached bubble. In such an instance, the microjet is so short
that it is almost
indistinguishable from the stable cusp of the gas-liquid interface.
2(1 When the first fluid of the invention is a gas and the second fluid is a
liquid, and
the two fluid stream is expelled into a gaseous atmosphere, a liquid jet with
a regularly
spaced gaseous formation of bubbles is formed. The regularity of the bubbles
is such that
the liquid jet is deformed in a very regular manner, resulting in a highly
monodisperse
stream of hollow droplet.4. The gas inside these hollow droplets may be
manipulated by
25 appropriate chemical, thermal or mechanical means to expand further upon
expulsion from
the device, causing the hollow bubbles to break into even finer droplets.
Alternatively, if
the liquid used is curable, the hollow droplets may be cured to a hollow,
solid form.
The forces exerted by the second fluid flow on the first fluid surface should
be
steady enough to prevent irregular surface oscillations. Therefore, any
turbulence in the
30 gas and liquid motion should be avoided; even if the gas velocity is high,
the characteristic
size of the orifice should ensure that the fluid motion is laminar (similar to
the boundary
layers formed on the jet and on the inner surface of the nozzle or hole).
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STABLE CAPILLARY MICROJET
Figure 4 illustrates the interaction of a gas and a liquid to form bubbles
using the
method of the invention. The feeding needle 60 has a circular exit opening 61
with an
internal radius R, which feeds a gas 62 out of the end, forming a drop with a
radius in the
range of R, to R, plus the thickness of the wall of the needle. Thereafter the
drop narrows in
circumference to a much smaller circumference as is shown in the expanded view
of the
tube (i.e. feeding needle) 5 as shown in Figures 1 and 4. The exiting gas flow
comprises an
infinite amount of streamlines 63 that after interaction of the gas with the
surrounding liquid
narrows to form a stable cusp at the interface 64 of the two fluids. The
surrounding liquid
also forms an infinite number of liquid streamlines 65, which interact with
the solid surfaces
and the exiting gas to create the effect of a virtual focusing funnel 66. The
exiting gas is
focused by the focusing funnel 66 resulting in a stable capillary microjet 67,
which remains
stable until it exits the opening 68 of the pressure chamber 69. After exiting
the pressure
chamber, the microjet begins to break-up, forming monodispersed particles 70.
1:5 The liquid flow, which affects the gas withdrawal and its subsequent
deceleration
after the jet is formed, should be very rapid but also uniform in order to
avoid perturbing the
fragile capillary interface (the surface of the drop that emerges from the
jet).
As illustrated in Figure 4, the exit opening 61 of the capillary tube 60 is
positioned
close to an exit opening Ei8 in a planar surface of a pressure chamber 69. The
exit opening
68 has a minimum diameter Do and is in a planar member with a thickness e. The
diameter
Do is referred to as a minimum diameter because the opening may have a conical
configuration with the narrower end of the cone positioned closer to the
source of liquid
flow. Thus, the exit opening may be a funnel-shaped nozzle although other
opening
configurations are also possible, e.g. an how glass configuration. Liquid in
the pressure
chamber continuously flows out of the exit opening. The flow of the liquid
causes the gas
drop expelled from the tube to decrease in circumference as the gas moves away
from the
end of the tube in a direction toward the exit opening of the pressure
chamber.
In actual use, it can be understood that the opening shape which provokes
maximum liquid acceleration (and consequently the most stable cusp and
microjet with a
30~ given set of parameters) is a sonically shaped opening in the pressure
chamber. The conical
opening is positioned with its narrower end toward the source of gas flow.
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The distance between the end 61 of the tube 60 and the beginning of the exit
opening 68 is H. At this point it is noted that R,, D~, H and a are all
preferably on the order
of hundreds of microns. For example, R, = 400,um, Da = 150,um, H = lmm, a =
300~m.
However, each could be 1/100 to lOx these sizes.
The end of the gas stream develops a cusp-like shape at a critical distance
from the
exit opening 68 in the pressure chamber 69 when the applied pressure drop DP,
across the
exit opening 68 overcomes the liquid-gas surface tension stresses y/R'
appearing at the point
of maximum curvature -- e.g. 1/R' from the exit opening.
A steady state is then established if the gas flow rate Q ejected from the
drop cusp
is steadily supplied from the capillary tube. This is the stable capillary
cusp which is an
essential characteristic of the invention needed to form the stable microjet.
More
particularly, a steady, thin gas jet with a typical diameter d~ is smoothly
emitted from the
stable cusp-like drop shape and this thin gaseous jet extends over a distance
in the range of
microns to millimeters. 'Che length of the stable microjet will vary from very
short (e.g. 1
1 _'i micron) to very long (e.g. 50 mm) with the length depending on the ( 1 )
flow-rate of the gas
(2) the Reynolds number of the gas and liquid streams flowing out of the exit
opening of the
pressure chamber and (3) the Weber number of the gas jet. The gas jet is the
stable capillary
microjet obtained when supercritical flow is reached. As mentioned, in the
case of a gas jet
the microjet may be so small as to be almost indistinguishable from the stable
cusp. This jet
demonstrates a robust behavior provided that the pressure drop DP, applied to
the liquid is
sufficiently large compared to the maximum surface tension stress (on the
order of y/d~) that
act at the liquid-gas interface. The stable microjet is formed without the
need for other
forces, i.e. without adding force such as electrical forces on a charged
fluid. However, for
some applications it is preferable to add charge to particles, e.g. to cause
the particles to
adhere to a given surface. The shaping of gas exiting the capillary tube by
the liquid flow
forming a focusing funnel creates a cusp-like meniscus resulting in the stable
microjet. This
is a fundamental characteristic of the invention.
The microjet eventually destabilizes due to the effect of surface tension
forces.
Destabilization results from small natural perturbations moving downstream,
with the fastest
growing perturbations being those which govern the break up of the microjet,
eventually
creating a uniform sized monodispersion of bubbles 70 as shown in Figure 4.
The microjet,
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even as it initially destabilizes, passes out of the exit orifice of the
pressure chamber without
touching the peripheral surface of the exit opening.
lUATHEMATICS OF A STABLE MICROJET
Cylindrical coordinates (r,z) are chosen for analyzing the shape of a stable
microjet, i.e. a liquid jet undergoing "supercritical flow." The cusp-like
meniscus formed by
the fluid coming out of the tube is pulled toward the exit of the pressure
chamber by a
pressure gradient created by the flow of a second, immiscible fluid.
The cusp-like :meniscus formed at the tube's mouth is pulled towards the hole
by
the pressure gradient created by the liquid stream. From the cusp of this
meniscus, a steady
gas thread with the shape of radius r = ~ is withdrawn through the hole by the
action of both
the suction effect due to .~P,, and the tangential viscous stresses i, exerted
by the liquid on
the jet's surface in the axial direction. The averaged momentum equation for
this
configuration may be written (assuming Dp1«P~T, where RB is the gas constant
and T its
1:5 temperature):
d P~' 2i
(1)
d s 2IIx~~
where Q is the gas flow rate upon exiting the feeding tube, P8 is the gas
pressure, and pg is
the gas density, assuming that the viscous extensional term .is negligible
compared to the
kinetic energy term, as will be subsequently justified. The gas pressure Pg is
given by the
capillary equation.
1'g - 1't + Y~~.
where y is the liquid-gas surface tension. As shown in the Examples, the
pressure drop AP,
is sufficiently large as compared to the surface tension stress y/~ to justify
neglecting the
latter in the analysis. This scenario holds for the whole range of flow rates
in which the
microjet is absolutely stable. In fact, it will be shown that, for a given
pressure drop OP,,
the minimum gas flow rate that can be sprayed in steady jet conditions is
achieved when the
surface tension stress y/~ is of the order of the kinetic energy of the liquid
(of the order of
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App, since the surface tension acts like a "resistance" to the motion (it
appears as a negative
term in the right-hand side term of Eq. (1)). Thus,
d3 is
min ~ J
Pg
For sufficiently large flow rates Q compared to Q~;", the simplified averaged
momentum
equation in the axial direction can be expressed as
~i
_d P~Q 2 dPl 2,~5
+ (4)
dz 21I2~4 dz
where one can identify the two driving forces for the gas flow on the right-
hand side. In
general, the pressure gradient in the liquid is on the average much larger
than the viscous
shear term 2i,/~ owning to the surface stress. On the other hand, the axial
viscous forces in
the gas are many orders of magnitude smaller than the pressure forces. The
neglect of all
l Omiscous terms in Eq. (4) is. then justified. Notice that in this limit on
the gas flow is quasi-
isentropic in the average (the liquid almost follows Euler-Bernoulli
equations) as opposed to
most micrometric extensional flows. Thus, integrating (4) from the stagnation
regions of
both fluids up to the exit, one obtains a simple and universal expression for
the jet diameter at
the hole exit:
v,
d. ~ gPg Q ~' ($)
J ~2QPl s
15 which for a given pressure drop ~,P, is independent of geometrical
parameters (hole and tube
diameters, tube-hole distance, etc.), liquid and gas viscosities, and liquid-
gas surface tension.
The proposed system obviously requires delivery of the gas to be atomized and
the
liquid to be used in the resulting drop production. Both should be fed at a
rate ensuring that
the system lies within the ::table parameter window. Multiplexing is effective
when the flow-
20 rates needed exceed those on an individual cell. More specifically, a
plurality of
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feeding sources or feeding needles may be used to increase the rate at which
aerosols are
created. The flow-rates used should also ensure the mass ratio between the
flows is
compatible with the specifications of each application.
The gas and liquid can be dispensed by any type of continuous delivery system
(e.g. a compressor or a pressurized tank the former and a volumetric pump or a
pressurized
bottle the latter). If multiplexing is needed, the liquid flow-rate should be
as uniform as
possible among cells; this may entail propulsion through several capillary
needles, porous
media or any other medium capable of distributing a uniform flow among
different feeding
points.
Each individual. device should consist of a feeding point (a capillary needle,
a
point with an open micro<;hannel, a microprotuberance on a continuous edge,
etc.) 0.002-2
mm (but, preferentially 0.01-0.4 mm) in diameter, where the drop emerging from
the
microjet can be anchored, and a small orifice 0.002-2 mm (preferentially 0.01-
0.25 mm) in
diameter facing the drop and separated 0.01-2 mm (preferentially 0.2-0.5 mm)
from the
feeding point. The orifice communicates the withdrawal liquid around the drop,
at an
increased pressure, with the zone where the atomizate is produced, at a
decreased pressure.
The device can be made from a variety of materials (metal, polymers, ceramics,
glass).
Figure 1 depicts. a tested prototype where the gas to be atomized is inserted
through one end of the system 2 and the liquid in introduced via the special
inlet 4 in the
pressure chamber 3. The prototype was tested at gas feeding rates from 10 to
2000 mBar
above the atmospheric pressure Pa at which the atomized gas was discharged.
The whole
enclosure around the feeding needle I was at a pressure Po > Pa. The gas
feeding pressure,
P,, should always be slightly higher than the liquid propelling pressure, Po.
Depending on
the pressure drop in the needle and the gas feeding system, the pressure
difference (P, - Po >
0) and the flow-rate of the gas to be atomized, Q, are linearly related
provided the flow is
laminar - which is indeed the case with this prototype. The critical
dimensions are the
distance from the needle to the plate (H), the needle diameter (Do), the
diameter of the
orifice through which the microjet 6 is discharged (do) and the axial length,
e, of the orifice
(i. e. the thickness of the plate where the orifice is made). In this
prototype, H was varied
from 0.3 to 0.7 mm on constancy of the distances (Do = 0.45 mm, do - 0.2 mm)
and a - 0.5
mm. The quality of the resulting spray 7 did not vary appreciably with changes
in H
provided the operating regime (i.e. stationary drop and microjet) was
maintained. However,
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the system stability suffered at the longer H distances (about 0.7 mm). The
other atomizer
dimensions had no effect on the spray or the prototype functioning provided
the zone around
the needle (its diameter) was large enough relative to the feeding needle.
WEBER NUMBER
Adjusting parameters to obtain a stable capillary microjet and control its
breakup
into monodisperse particle is governed by the Weber number and the liquid-to-
gas velocity
ratio or a which equal Y,~Vg. The Weber number or "We" is defined by the
following
equation:
We = PI Y2d
wherein p, is the density of the gas, d is the diameter of the stable
microjet, y is the liquid-gas
surface tension, and YZ is the velocity of the liquid squared.
When carrying out the invention the parameters should be adjusted so that the
Weber number is greater than 1 in order to produce a stable capillary
microjet. However, to
obtain a particle dispersion which is monodisperse (i.e. each particle has the
same size X0.01
1!i to f30%) the parameters should be adjusted so that the Weber number is
less than about 40.
The monodisperse aerosol is obtained with a Weber number in a range of about 1
to about 40
( 1 s We s 40).
OHNESORGE NUMBER
A measure of the relative importance of viscosity on the jet breakup can be
estimated from the Ohnesorge number defined as the ratio between two
characteristic times:
the viscous time ~, and the breaking time tb. The breaking time tb is given by
[see Rayleigh
( 1878)]
~,2 is
b Y . (2)
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Pe-rturbations on the jet surface are propagated inside by viscous diffusion
in times t" of the
order of
(3 )
where,u, is the viscosity of the liquid. Then, the Ohnesorge number, Oh,
results
Nl
Oh = ------ (4)
~Pl Y d~/
If this ratio is much smaller than unity viscosity plays no essential role in
the phenomenon
under consideration. Since the maximum value of the Ohnesorge number in actual
experiments conducted is as tow as 3.7X 10"2, viscosity plays no essential
role during the
process of jet breakup.
EMBODllvIENT OF FIGURE 2
A variety of configurations of components and types of fluids will become
apparent to those skilled in the art upon reading this disclosure. These
configurations and
fluids are encompassed by the present invention provided they can produce a
stable capillary
microjet of a first fluid from a source to an exit port of a pressure chamber
containing a
second fluid. The stable microjet is formed by the first fluid flowing from
the feeding
1 S source to the exit port of the pressure chamber being accelerated and
stabilized by pressure
stress exerted by the second fluid is the pressure chamber on the surface of
the first fluid
forming the microjet. The second fluid forms a focusing funnel when a variety
of
parameters are correctly tuned or adjusted. For example, the speed, pressure,
viscosity and
miscibility of the first and second fluids are chosen to obtain the desired
results of a stable
micxojet of the first fluid focused into the center of a funnel formed with
the second fluid.
These results are also obtained by adjusting or tuning physical parameters of
the device,
including the size of the opening from which the first fluid flows, the size
of the opening
from which both fluids exit; and the distance between these two openings.
The embodiment of Figure 1 can, itself, be arranged in a variety of
configurations. .
Further, as indicated above" the embodiment may include a plurality of feeding
needles. A
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plurality of feeding needles may be configured concentrically in a single
construct, as shown
in Figure 2.
The components of the embodiment of Figure 2 are as follows:
21. Feeding needle - tube or source of fluid.
22. End of the feeding needle used to insert the liquids to be atomized.
23. Pressure c;hamber.
24. Orifice used as liquid inlet.
25. End of the feeding needle used to evacuate the gas to be atomized.
26. Orifice through which withdrawal takes place.
27. Atomizate (spray) or aerosol.
28. First gas t.o be atomized (inner core of particle).
29. Second fluid to be atomized (outer coating of particle).
30. Liquid for creation of microjet.
31. Internal t«be of feeding needle.
I S 32. External tube of feeding needle.
D = diameter of the feeding needle; d = diameter of the orifice
through which the microjet is passed; a = axial length of the
orifice through which withdrawal takes place; H = distance
from the feeding needle to the microjet autlet; y=surface
tension; P'a = pressure inside the chamber; Pa = atmospheric
pressure.
The embodiment of Figure 2 is preferably used when attempting to form a
spherical particle of one substance surrounded by another substance. The
device of Figure 2
is comprised of the same basic component as per the device of Figure 1 and
further includes
a second feeding source 32 which is positioned concentrically around the first
cylindrical
feeding source 31. The second feeding source may be surrounded by one or more
additional
feeding sources with each concentrically positioned around the preceding
source.
The process is based on the microsuction which the liquid-gas or liquid-liquid
interphase undergoes (if both are immiscible), when said interphase approaches
a point
beginning from which one of the fluids is suctioned off while the combined
suction of the
two fluids is produced. The interaction causes the fluid physically surrounded
by the other
to form a capillary microjet which finally breaks into spherical drops. If
instead of two
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fluids (gas-liquid), three or more are used that flow in a concentric manner
by injection
using concentric tubes, a. capillary jet composed of two or more layers of
different fluids is
formed which, when it breaks, gives rise to the formation of spheres composed
of several
approximately concentric spherical layers of different fluids. The size of the
outer sphere
(its thickness) and the siae of the inner sphere (its volume) can be precisely
adjusted. This
can allow the manufacture of layered bubbles for a variety of end uses.
The method is based on the breaking of a capillary microjet composed of a
nucleus of a gas and suwounded by other liquids and gases which are in a
concentric manner
injected by a special injection head, in such a way that they form a stable
capillary microjet
and that they do not mix by diffusion during the time between when the
microjet is formed
and when it is broken. When the capillary microjet is broken into spherical
drops under the
proper operating conditions, which will be described in detail below, these
drops exhibit a
spherical nucleus, the size and eccentricity of which can be controlled.
In the case of spheres containing two materials, the injection head 25
consists of
two concentric tubes with an external diameter on the order of one millimeter.
Through the
internal tube 31 is injected the material that will constitute the nucleus of
the microsphere,
while between the internal tube 31 and the external tube 32 the coating is
injected. The fluid
of the external tube 32 joins with the fluid of tube 31 as the fluids exit the
feeding needle,
and the fluids thus injected are accelerated by a stream of gas for liquid hat
passes through a
2~0 small orifice 24 facing the end of the injection tubes. When the drop in
pressure across the
orifice 24 is sufficient, the fluids form a completely stationary capillary
microjet, if the
quantities of liquids that are injected are stationary. This microjet does not
touch the walls
of the orifice, but passes through it wrapped in the stream of gas or funnel
formed by gas
from the tube 32. Because the funnel of fluid focuses the exiting fluid, the
size of the exit
2:5 orifice 26 does not dictate the size of the particles formed.
When the parameters are correctly adjusted, the movement of the fluid is
uniform
at the exit of the orifice 2;6 and the viscosity forces are sufficiently small
so as not to alter
either the flow or the properties of the liquids; for example, if there are
biochemical
molecular specimens having a certain complexity and fragility, the viscous
forces that would
3~) appear in association with the flow through a micro-orifice might degrade
these substances.
Figure 2 shows a simplified diagram of the feeding needle 21, which is
comprised
of the concentric tubes 3c), 31 through the internal and external flows of the
fluids 28, 29
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that are going to compose the microspheres comprised of two immiscible fluids.
The
difference in pressures ~'o - Pa (Po > P~ through the orifice 26 establishes a
flow of liquid
present in the chamber :!3 and which is going to surround the microjet at its
exit. The same
pressure gradient that moves the liquid is the one that moves the microjet in
an axial direction
through the hole 26, provided that the difference in pressures Po - Pa is
sufficiently great in
comparison with the forces of surface tension, which create an adverse
gradient in the
direction of the movement.
There are two limitations for the minimum sizes of the inside and outside jets
that
are dependent (a) on the surface tensions y 1 of the outside fluid 29 with the
liquid 3 0 and 'y2
of the outside fluid 29 wrath the inside fluid (e.g. gas) 2g, and (b) on the
difference in pressures
AP = Po - Pa through the orifice 26. In the first place, the jump in pressures
AP must be
sufficiently great so that the adverse effects of the surface tension are
minimized. This,
however, is attained for very modest pressure increases: for example, for a 10
micron jet of a
gas having a surface tension of 0.05 N/m (tap water), the necessary minimum
jump in
1', 5 pressure is in the order of 0.05 (N/m) / 0.00001 m = AP= 50 mBar. But,
in addition, the
breakage of the microjet must be regular and axilsymmetric, so that the drops
will have a
uniform size, while the extra pressure AP cannot be greater than a certain
value that is
dependent on the surface tension of the outside gas with the gas ~yl and on
the outside
diameter of the microjet. It has been experimentally shown that this
difference in pressures
~:0 cannot be greater than 2~0 times the surface tension Yl divided by the
outside radius of the
microjet.
Therefore, given some inside and outside diameters of the microjet, there is a
range
of operating pressures between a minimum and a maximum; nonetheless,
experimentally the
best results are obtained for pressures in the order of two to three times the
minimum..
~;5 The viscosity values of the gases must be such that the gases with the
greater
viscosity ~ verifies, far a diameter ~[ of the jet predicted for this gas and
a difference
through the orifice AP , the inequality:
~ s ae Pazn
3~0 Q
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With this, the pressure gradients can overcome the extensional forces of
viscous
resistance exerted by the gas when it is suctioned toward the orifice.
Moreover, the gases must have very similar densities in order to achieve the
concentricity of the nucleus of the microsphere, since the relation of
velocities between the
gases moves according to the square root of the densities vl/v2 = (p2/pl)"~
and both jets,
the inside jet and the oul;side jet, must assume the most symmetrical
configuration possible,
which does not occur if the fluids have different velocities (Figure 2).
Nonetheless, it has
been experimentally demonstrated that, on account of the surface tension y2
between the two
fluids, the nucleus tends to migrate toward the center of the microsphere,
within prescribed
parameters.
The distance between the plane of the internal tube 31 (the one that will
normally
project more) and the plane of the orifice may vary between zero and three
outside
diameters of the external tube 32, depending on the surface tensions between
the fluids and
with the liquid, and on their viscosity values. Typically, the optimal
distance is found
experimentally for each ;particular configuration and each set of liquids
used.
The proposed dispersion system obviously requires fluids that are going to be
used
in the resulting bubbles to have certain flow parameters. Accordingly, flows
for this use
must be:
- Flows that are suitable so that the system fails within the parametric
window of
stability. Multiplexing (i.e. several sets of concentric tubes) may be used,
if the flows
required are greater than those of an individual cell.
- Flows that are suitable so that the mass relation of the fluids falls within
the
specifications of each application. Of course, a greater flow of liquid may be
supplied
externally by any means in specific applications, since this does not
interfere with the
functioning of the atomizer.
Therefore, any means for continuous supply of gas (compressors, pressure
deposits, etc.) and of liquid (volumetric pumps, pressure bottles, etc.) may
be used. If
multiplexing is desired, the flow of gas must be as homogeneous as possible
between the
various cells, which may require impulse through multiple capillary needles,
porous media,
3~0 or any other medium capable of distributing a homogeneous flow among
different feeding
points.
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Each dispersion device will consist of concentric tubes 31, 32 with a diameter
ranging between 0.05 and 2 mm, preferably between 0..1 and 0.4 mm, on which
the drop
from which the microjet emanates can be anchored, and a small orifice (between
0.001 and
2 mm in diameter, preferably between 0.1 and 0.25 mm), facing the drop and
separated from
the point of feeding by a distance between 0.001 and 2 mm, preferably between
0.2 and 0.5
mm. The orifice puts the liquid that surrounds the drop, at higher pressure,
in touch with the
area in which the dispersion is to be attained, at lower presswe.
EMBODIMENT OF FIGURE 3
The embodiments of Figures 1 and 2 are similar in a number of ways. Both have
a feeding piece which is preferably in the form of a feeding needle with a
circular exit
opening. Further, both have an exit port in the pressure chamber which is
positioned
directly in front of the flow path of fluid out of the feeding source.
Precisely maintaining
the alignment of the flovc~ path of the feeding source with the exit port of
the pressure
1.5 chamber can present an engineering challenge particularly when the device
includes a
number of feeding needles. The embodiment of Figure 3 is designed to simplify
the manner
in which components are aligned. The embodiment of Figure 3 uses a planar
feeding piece,
which by virtue of the withdrawal effect produced by the pressure difference
across a small
opening through which fluid is passed permits multiple microjets to be
expelled through
multiple exit ports of a pressure chamber thereby obtaining multiple aerosol
streams.
Although a single planar feeding member is shown in Figure 3 it, of course, is
possible to
produce a device with a plurality of planar feeding members where each planar
feeding
member feeds fluid to a linear array of outlet orifices in the surrounding
pressure chamber.
In addition, the feeding member need not be strictly planar, and may be a
curved feeding
2:> device comprised of two surfaces that maintain approximately the same
spatial distance
between the two pieces of the feeding source. Such curved devices may have any
level of
curvature, e.g. circular, semicircular, elliptical, hemi-elliptical, etc.
The components of the embodiment of Figure 3 are as follows:
41. Feeding piece.
42. End of the feeding piece used to insert the gas to be dispersed.
43. Pressure chamber.
44. Orifice used as liquid inlet.
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45. End of t:he feeding needle used to evacuate the gas to be dispersed.
46. Orifices through which withdrawal takes place.
47. Dispersion bubbles.
48. First fluid containing material to be dispersed.
49. Second fluid for creation of microjet.
50. Wall of the propulsion chamber facing the edge of the feeding piece.
51. Channels for guidance of fluid through feeding piece.
d = diameter .of the microjet formed; pA density of first fluid (48); pB
density of
second fluid (49), vA velocity of the first fluid (48); vB=velocity of the
second fluid (49); a =
l.0 axial length of the orifice through which withdrawal takes place; H =
distance from the
feeding needle to the microjet outlet; Po = pressure inside the chamber; dp8=
change in
pressure of the gas; Pa = atmospheric pressure; Q=volumetric flow rate
The proposed dispersion device consists of a feeding piece 41 which creates a
planar feeding channel through which a where a first fluid 48 flows. The flow
is
1.5 preferably directed through one or more channels of uniform bores that are
constructed on
the planar surface of the feeding piece 41. A pressure chamber 43 that holds
the
propelling flow of a second liquid 49, houses the feeding piece 41 and is
under a pressure
above maintained outside the chamber wall 50. One or more orifices, openings
or slots
(outlets) 46 made in the wall 52 of the propulsion chamber face the edge of
the feeding
~:0 piece. Preferably, each bore or channel of the feeding piece 41 has its
flow path
substantially aligned with an outlet 46.
When the second fluid 49 is a liquid and the first fluid 48 is a gas, the
facts that
the liquid is much more viscous and that the gas is much less dense virtually
equalize the
fluid and gas velocities. The gas microthread formed is much shorter; however,
because
~;5 its rupture zone is almost invariably located in a laminar flowing stream,
dispersion in the
size of the microbubble~s formed is almost always small. At a volumetric gas
flow-rate Qg
and a liquid overpressura DP,, the diameter of the gas microjet is given by
y,
gPg Q ~iz
?L2~Pl 8
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The low liquid velocity and the absence of relative velocities between the
liquid and gas
lead to the Rayleigh relation between the diameters of the microthread and
those of the
bubbles (i. e. d = 1.89d;).
OXYGENATION OF WATER
More fish die from a lack of oxygen than any other cause. Fish exposed to low
oxygen conditions become much more wlnerable to disease, parasites and
infection, since
low oxygen levels will (1) lower the oxidation/reduction potential (ORP) (2)
favor growth
of disease causing pathogens and (3) disrupt the function of many commercially
available
1 ~0 biofilters. Moreover, stress will reduce the fish activity level, growth
rate, and may
interfere with proper development. A continuous healthy minimum of oxygen is
approximately a 6 parts per million (ppm) oxygen:water ratio, which is
approximately 24
grams of dissolved oxygen per 1000 gallons of water. Fish consume on average
18 grams
of oxygen per hour for every ten pounds of fish. Low level stress and poor
feeding
1:5 response can be seen at oxygen levels of 4-5 ppm. Acute stress, no feeding
and inactivity
can be seen at oxygen levels of 2-4 ppm, and oxygen levels of approximately 1-
2 ppm
generally result in death.. These numbers are merely a guideline since a
number of
variable (e.g., water temperature, water quality, condition of fish, level of
other gasses,
etc.) all may impact on actual oxygen needs.
2n Proper aeration depends primarily on two factors: the gentleness and
direction of
water flow and the size and amount of the air bubbles. With respect to the
latter, smaller
air bubbles are preferable because they (1) increase the surface are between
the air and the
water, providing a larger area for oxygen diffusion and (2) smaller bubbles
stay suspended
in water longer, providing a greater time period over which the oxygen may
diffuse into
2:5 the water.
The technology of the invention provides a method for aerating water for the
proper growth and maintenance of fish. A device of the invention for such a
use would
provide an oxygenated gas, preferably air, as the first fluid, and a liquid,
preferably water,
as the second fluid. The. air provided in a feeding source will be focused by
the flow of
3n the surrounding water, creating a stable cusp at the interface of the two
fluids. The
particles containing the gas nucleus, and preferably air nucleus, are expelled
into the liquid
medium where aeration is desired.
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BUBBLES INTO LIQUID OR GAS
Figures 7 and 8 are useful in showing how bubbles may be formed in either a
liquid (Figure 7) or a gas (Figure 8). In Figure 7 a tubular feeding source 71
is continually
supplied with a flow of gas which forms a stable cusp 7:2 which is surrounded
by the flow
'_. of liquid 73 in the pressure chamber 74 which is continually supplied with
a flow of liquid
73. The liquid 73 flows out of the chamber 74 into a liquid 75 which may be
the same as or
different from the liquid '73.
The cusp 72 of gas narrows to a capillary supercritical flow 76 and then enter
the
exit opening 77 of the ch~unber 74. At a point 78 in the exit opening 77 the
supercritical
flow 76 begins to destabilize but remains as a critical capillary flow until
leaving the exit
opening 77. Upon leaving the exit opening 77 the gas stream breaks apart and
forms
bubbles 79 each of which. are substantially identical to the others in shape
and size. The
uniformity of bubbles is such that one bubble differs from another (in terms
of measwed
physical diameter) in an amount in a range of standard deviation of 10.01% to
t30% with a
1'i preferred deviation being less than 1 %. Thus, the uniformity in size of
the bubbles is greater
than the uniformity of the particles formed as described above in connection
with Figure 1
when liquid particles are formed.
Gas in the bubbles 79 will diffuse into the liquid 75. Smaller bubbles provide
for
greater surface area contact with the liquid 75. Smaller bubbles provide for
greater surface
area contact with the liquid 75 thereby allowing for a faster rate of
diffusion then would
occur if the same volume of gas were present in a smaller number of bubbles.
For example,
ten bubbles each containing 1 cubic mm of gas would diffuse gas into the
liquid much
more rapidly than one bubble containing 10 cubic mm of gas. Further, smaller
bubbles rise
to the liquid surface more slowly than larger bubbles. A slower rate of ascent
in the liquid
2'.i means that the gas bubbles are in contact with the liquid for a longer
period of time thereby
increasing the amount of diffusion of gas into the liquid. Thus, smaller
bubbles could allow
a greater amount of oxygen to diffuse into water (e.g., to sewage or where
fish are raised) or
allow a greater amount of a toxic gas (e.g., a radioactive gas) to diffuse
into a liquid thereby
concentrating the toxin for disposal. Because the bubbles are so uniform in
size the amount
of gas diffusing into the liquid can be uniformly calculated which is
important in certain
applications such as when diffusing C02 into carbonated drinks.
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wo 99r~osm pcTns9siozos~
Figure 8 shows the same components as shown in Figure 7 except that the liquid
75 is replaced with a gas .80. When the stream of bubbles 79 disassociate the
liquid 73
fortes an outer spherical cover thereby providing hollow droplets 81 which
will float in the
gas 80. The hollow droplets 81 have a large physical or actual diameter
relative to their
aerodynamic diameter. Hollow droplets fall in air at a much slower rate
compared to liquid
droplets of the same diameter. Because the hollow droplets 81 do not settle or
fall quickly
in air they can evaporate and diffuse the evaporated liquid into surrounding
air. Eventually
the hollow droplets 81 will burst and form many smaller particles which
diffuse these
particles into the surrounding air. Thus, it is understood that the
aerodynamic diameter of
the hollow droplets is very small compared to their actual physical diameter.
The creation
of hollow droplets 81 which burst and form very small particles is applicable
in a wide range
of different applications including the creation of mists of water for cooling
systems.
EMULSIONS
15~ Figure 9 is similar to Figures 7 and 8. However, rather than a gas 72 as
in Figure
7 the feeding source 71 provides a stream of liquid 82 which may be miscible
but is
preferably immiscible in the liquid 73. Further the liquid 73 may be the same
as or different
from the liquid 75 but is preferably immiscible in the liquid 75. The creation
of emulsions
using such a configuration of liquids has applicability in a variety of fields
particularly
ZO because the liquid particles formed can have a size in the range of from
about 1 to about 200
microns with a standard deviation in size of one particle to another being as
little as 0.01%.
The size deviation of one particle to another can vary up to about 30% and is
preferably less
than ~5% and more preferably less than tl%.
The system operates to expel the liquid 82 out of the exit orifice 77 to form
25 spheres 83 of liquid 82. Each sphere 83 has an actual physical diameter
which deviates from
other spheres 83 by a standard deviation of X0.01% to X30%, preferably 10% or
less and
more preferably 1% or less. The size of the spheres 83 and flow rate of liquid
82 is
controlled so that each sphere 83 contain a single particle (e.g. a single
cell) to be examined.
The stream of spheres 83 is caused to flow past a sensor and/or energy source
of any desired
30 type thereby allowing for sphere-by-sphere analysis of the sample of liquid
82.
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EMUL SIONS
In Figure 9 the liquid 75 can be a gas (e.g., air). The liquid 82 could be
water
which is surrounded by a second liquid 73 which is a compound for creating a
desired odor
e.g., a perfume. The system then forms particles 83 which have a water center
and an outer
coating of fuel. Such water/perfume particles will rapidly disperse the
perfume at a low
cost.
While the present invention has been described with reference to the specific
embodiments thereof, it should be understood by those skilled in the art that
various changes
lt? may be made and equivalents may be substituted without departing from the
true spirit and
scope of the invention. In addition, many modifications may be made to adapt a
particular
situation, material, composition of matter, process, process step or steps, to
the objective,
spirit and scope of the prE;sent invention. All such modifications are
intended to be within
the scope of the claims appended hereto.
1 '.i
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