U.S. patent application number 10/903115 was filed with the patent office on 2005-03-24 for multi-stage eductor apparatus.
Invention is credited to Foret, Todd L..
Application Number | 20050061378 10/903115 |
Document ID | / |
Family ID | 34135136 |
Filed Date | 2005-03-24 |
United States Patent
Application |
20050061378 |
Kind Code |
A1 |
Foret, Todd L. |
March 24, 2005 |
Multi-stage eductor apparatus
Abstract
A multi-stage eductor apparatus includes a first stage eductor
with an inlet, an outlet, and a venturi throat between the inlet
and outlet into which a driving fluid is injected to flow from the
outlet and create a suction at the inlet for drawing material into
the inlet and through the first stage eductor with the driving
fluid, and at least a second stage eductor of the same or similar
configuration, with the inlet of the second stage eductor connected
directly to the outlet from the first stage eductor, thereby
increasing the suction at the inlet to the first stage eductor and
maintaining the suction at the inlet to the first stage eductor
through a wide range of driving fluid flow rates.
Inventors: |
Foret, Todd L.; (Tyler,
TX) |
Correspondence
Address: |
Ronald B. Sefrna
Sefrna & Associates
P.O. Box 567
Tyler
TX
75710-0567
US
|
Family ID: |
34135136 |
Appl. No.: |
10/903115 |
Filed: |
July 30, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60492084 |
Aug 1, 2003 |
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Current U.S.
Class: |
137/888 |
Current CPC
Class: |
Y10T 137/87587 20150401;
F04F 5/04 20130101; F04F 5/467 20130101 |
Class at
Publication: |
137/888 |
International
Class: |
F04F 005/02 |
Claims
1. A multi-stage eductor apparatus, comprising a first venturi-type
eductor stage having a longitudinal axis, a first stage material
inlet centered on said longitudinal axis, and a first stage
material outlet in coaxial alignment with said first stage material
inlet; and a second venturi-type eductor stage having a
longitudinal axis, a second stage material inlet centered on said
longitudinal axis, and a second stage material outlet in coaxial
alignment with said second stage material inlet, said second stage
material inlet connected directly to said first stage material
outlet with said longitudinal axes of said first stage eductor and
said second stage eductor in coaxial alignment, forming a
passageway for the flow of material from said first stage eductor
directly into and through said second stage eductor.
2. The multi-stage eductor apparatus, of claim 1, wherein said
first stage eductor comprises a hollow first stage body with open
first and second ends and a longutidinal axis extending through
said first and second open ends, said open first end of said first
stage body being a first stage suction inlet for the introduction
of flowable material into said first stage body, having an elongate
first stage venturi tube with a hollow interior, open first and
second ends and a longitudinal axis, connected at said first end to
said first stage body in coaxial alignment therewith, said interior
of said first stage venturi tube narrowing in cross-sectional
dimension from said first end to a venturi throat and increasing in
cross-section dimension from said venturi throat toward said second
end, having a first stage driving fluid inlet in fluid flow
communication with at least one first stage driving fluid nozzle
for directing a driving fluid into said interior of said first
stage venturi tube adjacent to said first end thereof in the
direction of said second end of said first stage venturi tube.
3. The multi-stage eductor apparatus of claim 1, wherein said
second stage eductor comprises a hollow second stage body with open
first and second ends and a longutidinal axis extending through
said first and second open ends, said open first end of said second
stage body being a second stage suction inlet for the introduction
of flowable material into said second stage body, having an
elongate second stage venturi tube with a hollow interior, open
first and second ends and a longitudinal axis, connected at said
first end to said second stage body in coaxial alignment therewith,
said interior of said second stage venturi tube narrowing in
cross-sectional dimension from said first end to a venturi throat
and increasing in cross-section dimension from said venturi throat
toward said second end, having a second stage driving fluid inlet
in fluid flow communication with at least one second stage driving
fluid nozzle for directing a driving fluid into said interior of
said second stage venturi tube adjacent to said first end thereof
in the direction of said second end of said second stage venturi
tube.
4. The multi-stage eductor of claim 1, further comprising a third
venturi-type eductor stage having a longitudinal axis, a third
stage material inlet centered on said longitudinal axis, and a
third stage material outlet in coaxial alignment with said third
stage material inlet, said third stage material inlet connected
directly to said second stage material outlet with said
longitudinal axes of said first stage eductor, said second stage
eductor, and said third stage eductor in coaxial alignment, forming
a passageway for the flow of material from said first stage eductor
directly into and through said second stage eductor and from said
second stage eductor directly into and through said third stage
eductor.
Description
RELATED APPLICATION DATA
[0001] This application claims the benefits of U.S. Provisional
Patent Application Serial No. 60/492,084, filed Aug. 1, 2003, and
titled Multi-Stage Eductor Apparatus.
FIELD OF THE INVENTION
[0002] The present invention generally relates to venturi-type
suction devices and apparatus, and in its preferred embodiments
more specifically relates to suction and mixing eductor devices and
apparatus utilizing a plurality of longitudinally aligned
stages.
BACKGROUND OF THE INVENTION
[0003] The venturi tube, which invented by Giovanni Venturi,
basically comprises two tapered sections of pipe joined by a narrow
throat. This convergent-divergent shape is commonly referred to as
a diffuser when used in venturi tubes. As a fluid flows through the
venturi tube structure the fluid velocity in the throat is
increased and the pressure is reduced, in keeping with the
principles of conservation of energy and with Bernoulli's Theory,
which states, "At any point in a pipe through which a fluid is
flowing the sum of the pressure energy, the kinetic energy, and the
potential energy of a given mass of the fluid is constant."
[0004] Over time it was realized that the reduced pressure section
of the venturi structure provided suction capabilities that could
be put to use. Thus, a solid, liquid or gas could be moved,
aerated, pumped, mixed, entrained, reacted, transferred, conveyed,
agitated, sheared, or blended with a venturi tube incorporating an
opening at the point of greatest suction or vacuum. The absence of
any moving parts in the venturi-based suction device provides
significant advantages in reliability and operation as compared to,
e.g., mechanical pumps.
[0005] There are many names for venturi tubes that incorporate a
suction port. For example, if the motive or driving fluid is a
liquid, it is normally referred to as an eductor. If the motive or
driving fluid is a gas such as steam, the venturi tube is commonly
referred to as an ejector. Two other common names are aspirator and
siphon pump or siphon. However, the venturi tube with a suction
port is almost universally referred to as a jet pump or venturi
jet. For the sake of brevity and consistency, the remainder of the
disclosure of the present invention will utilize the term eductor,
and it is to be understood that the term "eductor" as used herein
shall refer to any venturi structure regardless of the motive fluid
used or the purpose for which the suction is utilized.
[0006] When an eductor is used to produce a suction for material
transport, mixing, etc., the motive fluid is typically injected at
or just before the narrowed throat of the venturi structure, so
that the motive fluid will increase in velocity as it flows through
the venturi throat, reducing pressure and creating a suction. Since
the motive fluid is injected tangentially, the longitudinal path
into the throat is available for the free flow of other material in
response to the suction created by the device. That material then
becomes mixed with and entrained by the driving fluid in the throat
of the venturi structure.
[0007] Various designs for the injection of the motive fluid have
been developed. In one design, manufactured by the Derbyshire
Machine and Tool Company of Philadelphia, Pa., nozzles are located
on the periphery of the inlet to the diffuser. Derbyshire refers to
its design as the Peri-Jet.RTM. Eductor. As another example, an
eductor with a lobed shape jet nozzle is manufactured by Vortex
Ventures, Inc. of Houston, Tex. Vortex Ventures refers to its
eductor as the LobeStar.RTM. Mixing Eductor. This nozzle is
disclosed in U.S. Pat. No. 5,664,733, to Gerald Lott.
[0008] There are several drawbacks associated with eductors known
in the prior art. First, an eductor has a specific geometry with
respect to the jet nozzle diameter, the throat, the diffuser, the
suction inlet and the discharge outlet. The geometry or diameter of
the jet nozzle determines the mass flow rate of the driving fluid.
The throat diameter of the diffuser section determines the velocity
of the combined streams which are the driving fluid and the
entrained material. The geometry of the divergent section of the
diffuser determines the pressure recovery capabilities of the
eductor.
[0009] Specific geometries can be referred to as fixed geometries.
Quite simply, eductors operate with pump curves based upon flow
rate through the jet nozzle at a specified pressure. Some eductors,
such as waterwell eductors, are designed to operate at low
pressures, ranging from10 to 50 psig. Eductors used for
firefighting purposes normally operate at a medium pressure range,
between 140 psig to 185 psig. Chemical ejection eductors used with
high pressure sprayers must operate at high pressures, ranging from
1000 to greater than 4000 psig. As pressure increases, flow through
a jet or orifice increases. For example, a one inch diameter nozzle
will flow 200 gallons per minute (gpm) at a pressure of 45 psig. At
a pressure of 180 psig, the flow will double to 400 gpm through the
same nozzle.
[0010] Eductors are designed to operate effectively within a
relatively narrow range of driving fluid pressures and flow rates,
and deviation from the design range typically results in
substantially reduced performance. For example, a prior art eductor
designed to operate with a driving fluid pressure of 150 psig at a
flowrate of 277 gpm will lift a column of water 20 feet when
operated at those parameters. However, when that eductor is
operated with a reduced pressure of 50 psig, with a corresponding
flow rate of 162 gpm, the eductor is capable of lifting a column of
water about 2 feet.
SUMMARY OF THE INVENTION
[0011] The present invention provides an eductor apparatus that
overcomes the drawbacks inherent in fixed ratio eductors,and which
can be effectively used over a wide range of pressures and flow
rates. The multi-stage eductor apparatus of the invention includes
a first eductor
[0012] The structure and features of the eductor apparatus of the
invention will be described in more detail with reference to the
accompanying drawing figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a side elevation schematic illustration of a first
embodiment of the multi-stage eductor of the invention.
[0014] FIG. 2 is a side elevation schematic illustration of a
second embodiment of the multi-stage eductor of the invention.
[0015] FIG. 3 is a graph showing a comparison between the
performance of an eductor of the invention and a prior art eductor
through a wide range of driving fluid pressures.
[0016] FIG. 4 is a side elevation schematic illustration of a third
embodiment of the multi-stage eductor of the invention.
DESCRIPTION OF THE INVENTION
[0017] The multi-stage eductor of the invention, generally
identified by reference number 10, comprises a first stage
venturi-type eductor 11, with a venturi throat section 12 and a
diffuser section 13, and a second stage venturi-type eductor 14
with a venturi throat section 15 and a diffuser section 16,
connected in series with the first stage. The first stage eductor
has an inlet 17 and an outlet 18, and the second stage eductor has
an inlet 19 and an outlet 20. The inlet of the second stage
structure connected to the outlet of the first stage so that the
longitudinal axes of the first and second stages are in coaxial
alignment. The flow of material into the multi-stage eductor
apparatus is indicated as "A", and the flow of material from the
multi-stage eductor apparatus is indicated as "B". The dashed line
through the structure represents the longitudinal axis of the
multi-stage eductor, as well as the center line of the flow path of
material drawn into and through the eductor.
[0018] The first stage eductor 11 has a driving fluid inlet 21 for
the introduction of a flow of driving fluid indicated as "C", and
the second stage eductor 14 has a driving fluid inlet 22 for the
introduction of a driving fluid "D" to the second stage. The
driving fluid(s), or motive fluid(s), is introduced, under
pressure, to the respective first and second stage eductors through
the respective inlet and is emitted into the interior of that stage
through first stage inlet nozzle or nozzles 23 and second stage
inlet nozzle or nozzles 24, upstream of the venturi throat of the
respective stage. The inlet nozzles are disposed to direct the
driving fluid toward the venturi throat at an angle relative to the
longitudinal axis of the stage, thereby creating a zone of reduced
pressure behind, or upstream from, the inlet nozzles in the region
of the suction inlet and inducing material flow into the suction
inlet.
[0019] The multi-stage eductor of the invention has been
demonstrated to provide a dramatic enhancement in eductor
effectiveness, measured in terms of the suction, or partial vacuum
developed by an eductor apparatus at a selected driving fluid
pressure and flow rate. In a controlled comparison test, one of the
stages of a multi-stage eductor as illustrated in FIG. 1 was
operated at various driving fluid pressures, and the suction
created by the single stage during operation at the various
pressures was measured. The second stage was then connected to form
the two-stage eductor illustrated in FIG. 1, and the suction
created by that multi-stage eductor at various driving fluid
pressures was measured and recorded. The comparative results are
shown in the following table and graphically illustrated in FIG. 3:
1
[0020] The vacuum produced was measured, and is shown in the table,
in inches of mercury. Fields in the table for which no data was
collected are left blank.
[0021] As can be readily seem from the table and the graphical
representation, the performance provided by the multi-stage eductor
is a dramatic improvement over the performance of a single eductor
stage, and is unprecedented in the prior art.
[0022] A test of the apparatus of FIG. 1 for the mixing of drilling
"mud" was performed to evaluate the performance of the apparatus in
a practical application. The apparatus was used to educt
AquaGel.RTM. dry drilling mud (essentially a bentonite) and mix the
dry material with water, which was also used as a driving fluid for
the eductor apparatus. Not only did the apparatus of the invention
perform more effectively than a conventional eductor in vacuuming
the dry material, the shear and mixing of the dry material with
water to produce a homogenous drilling mud fluid was highly
effective as well. The mud fluid was thoroughly mixed with no
clumps of dry material ("fisheyes"), and after a two week period of
observation there was no visually detectable precipitation of
bentonite particles from the fluid. To determine whether
discharging from the multi-stage eductor apparatus of the invention
against a static head would effect performance, the apparatus of
FIG. 1 was then set up to discharge mixed drilling mud against a 10
foot head, and the results were compared to results obtained
without the head. The head pressure or back pressure on the
multi-stage eductor had no detrimental effect.
[0023] Without limitation to any particular theory or to any
particular mechanism of action, it is contemplated that the
unprecedented improvement can be attributed to a "drafting effect",
similar to that experienced by a vehicle closely following another
in the slipstream created by the leading vehicle. It is known that
as a single vehicle, e.g., a race car, travels through the air it
creates a zone, or bubble, of high-density air in front of it and a
zone of low-density air behind. The difference in the pressure
between these two zones of air creates drag, the force that impedes
motion. This drag force limits the top speed the car can attain.
However, when a second car pulls up behind the first, the
slipstreams created by the two merge, so that the first car losses
its aft bubble and the second car loses its front bubble. This
effect reduces the drag force each car experiences and both are
able to travel slightly faster.
[0024] The same principle can apply to moving fluids. Again,
without limitation as to any particular theory or mechanism, it is
contemplated that the fluid discharging from the first stage
driving fluid nozzles does not readily give up energy to form a
boundary layer on the inner surface of the venturi throat and
diffuser. It is contemplated that the driving fluid discharging
from the second stage, or downstream, inlet nozzles forms a
boundary layer on the inner surface of the second stage venturi and
diffuser. The friction, and consequent drag associated with the
creation of a boundary layer in the first stage is reduced, if not
eliminated entirely.
[0025] Returning to the vehicle analogy, if the trailing vehicle
drops back out of the low pressure zone behind the leading vehicle,
the drafting effect is lost. Likewise, in the case of the
multi-stage eductor of the invention, it is contemplated that if
the stages are placed too far apart, the first stage cannot draft
on the second stage. Although in that instance the second,
downstream, stage will reduce head pressure for the first,
upstream, stage, the advantage of the drafting affect would be
lost. Hence, the stages should be disposed in sufficiently close
proximity to take advantage of drafting on each subsequent stage.
The close proximity and the drafting effect achieved by the present
invention distinguishes it from simply placing separated eductors
in series in the flow stream, as has been on occasion done in the
prior art. Separated eductors, even though piped in series, do not
achieve the drafting effect or the dramatic improvement in
effectiveness of the multi-stage eductor of the present invention,
and the practice of simply placing eductors in series is not
comparable or material prior art to the present invention.
[0026] FIG. 2 illustrates a modified version, or second embodiment,
of the apparatus shown in FIG. 1. In the apparatus of FIG. 2 the
diffuser section 13 of the first stage 11 is removed to enhance
velocity and take full advantage of the drafting affect of the
fluid entering into the second stage 14. In addition, this
configuration places the driving fluid inlet nozzles 23 of the
first stage closer to the inlet nozzles 24 of the second stage. The
diffuser section 16 of the second stage is retained in order to
reduce the velocity of the fluid, thus recovering pressure. The
more compact structure of the embodiment of FIG. 2 also provides
the advantages of reduced size and weight.
[0027] Although the multi-stage eductor of the invention is shown
in the drawing figures with two stages, it is to be understood that
the invention is not limited with regard to the number of stages. A
third stage and/or further additional stages may be added to the
apparatus, and the scope of the invention is to be considered to
include any number of stages.
[0028] The multi-stage eductor apparatus of the invention provide
the capability of utilizing different driving, or motive fluids in
the different stages. For example, referring to either FIG. 1 or
FIG. 2, a first motive supply fluid C, is used to provide a suction
for entraining a material A in the first stage 10a. A second motive
fluid D supplied to the second stage 10b provides drafting affects
for entraining and mixing fluids C and D, and material A. The
product is discharged through the diffuser 16 of the second stage
as a final product B. This capability substantially expands the
range of possible uses for an eductor apparatus beyond anything
contemplated or possible using prior art apparatus. For example,
the multi-stage eductor of the invention is ideally suited for
emulsifying a hydrophobic liquid and water with a surfactant.
[0029] A further variation, or alternative embodiment of the
multi-stage eductor of the invention is illustrated in FIG. 4, in
which the motive fluid C for the first stage is introduced through
a jet nozzle disposed with its axis in alignment with the
longitudinal axes of the first and second eductor stages, to create
a drafting envelope as generally indicated in the figure. As
material A is introduced into the first stage it is entrained in
the motive fluid through the first stage of the apparatus and into
the second stage. The embodiment of FIG. 4 provides the same
capabilities and advantages as the previously described
embodiments, and is susceptible to the same wide range of uses.
[0030] Another ideal application for the present invention is for
emulsifying super absorbent polymers (SAP) into water. Super
absorbent polymers, which readily absorb liquids, are used in baby
diapers, as well as many other uses. The typical SAP is the
chemical polyacrylamide, which is normally supplied in a
prehydrated form. Thus, prehydrated or prehydrolyzed polyacrylamide
is given the acrynom PHPA. Polymers are coiled when in the
prehydrated state. Thus, the polymer must be uncoiled and aged to
be highly effective. The multi-stage eductor allows for pneumatic
conveying PHPA into the first stage for uncoiling purposes,
followed by thorough mixing and blending in the second stage. The
PHPA emulsion can then be used for water treatment purposes, as a
drilling fluid additive or as a firefighting agent.
[0031] The multi-stage eductor can also be utilized as an effective
firefighting tool. Aqueous film forming foam (AFFF) is utilized to
suppress Class B fires. AFFF is educted into the firefighting water
and sprayed on top of the pool of burning fuel. Also, it may be
sprayed on a pool of spilled fuel to prevent a fire or to prevent
reflash of a fire. The benefit of the multi-stage eductor is that
is can supply high pressure water similar to a firefighting
monitor, while simultaneously educting in the AFFF.
[0032] Another application for the multi-stage eductor can be found
in the wastewater treatment industry. Aerators are used to supply
dissolved oxygen to aeration lagoons, ponds or tanks. Aerators
range from propeller type systems to low pressure roots blowers to
ineffective conventional eductor systems. The multi-stage eductor
is very well suited for a wastewater treatment plant for several
reasons. First, it can be used to entrain air and discharge the
mixture to the bottom of the lagoon. This agitates the lagoon and
prevents settling of solids. Second, since the multi-stage eductor
will pull a high vacuum, a suction hose can be attached to the
multi-stage eductor. This allows for operating the eductor of the
invention as a mini-dredge. Thus, solids can be removed from the
bottom of the lagoon for cleaning purposes with a multi-stage
eductor that can also be used as an aerator.
[0033] Another potential use for the multi-stage eductor of the
present invention involves the capture and recovery of volatile
organic compounds (VOCs); a use to which conventional eductors have
never been put. With the multi-stage eductor of the invention a
deep vacuum can be drawn on, for example, a glycol recovery boiler
condenser in order to recover VOCs. The vacuum and the flow rate of
VOCs can be controlled by operating each stage independently of one
another. For example, if the motive fluid is natural gas and line
pressure drops due to unforeseen equipment failures, another stage
can be brought online to maintain a constant vacuum and
flowrate.
[0034] Yet another application for the multi-stage eductor is using
it as a venturi scrubber. The variable vacuum and flow rate
capabilities of the multi-stage eductor, coupled with its ability
to thoroughly shear and mix fluids with micron sized particles,
makes it a highly effective gas scrubber. Themulti-stage eductor
would be ideally suited for scrubbing particulate matter smaller
than 2.5 microns (PM 2.5) from diesel emissions and power plant
flue gas.
[0035] Another application can be found in the medical industry.
Vacuum pumps are used throughout the medical industry for providing
a vacuum for many different uses. One application in particular
requires the use of an expensive desk size vacuum pump to provide a
vacuum for a small size tube of 1 to 3 millimeters in diameter.
When an ear is impacted, for example, a physician will utilize a
suction tube to withdraw the material away from the eardrum. A
small multi-stage eductor can easily be fabricated to operate with
water supplied from a lavatory or common kitchen faucet. Typically,
most cities control the water pressure between 30 and 60 psig. This
allows for a cost effective vacuum pump that is intrinsically safe
in that operation does not require electricity.
[0036] It is contemplated that many more uses and benefits of the
multi-stage eductor will be identified by those of skill in the
various arts in which the new apparatus may offer improvement over
conventional devices and methods.
[0037] The foregoing description of the structure and features, and
potential methods of use, of the multi-stage eductor is intended to
be illustrative and not for purposes of limitation. The apparatus
is susceptible to variations and further alternative embodiments in
addition to those discussed above, all within the scope of the
invention as described above and set forth in the following
claims.
* * * * *