U.S. patent number 3,885,931 [Application Number 05/474,364] was granted by the patent office on 1975-05-27 for vortex forming apparatus and method.
This patent grant is currently assigned to Donaldson Company, Inc.. Invention is credited to Robin E. Schaller.
United States Patent |
3,885,931 |
Schaller |
May 27, 1975 |
Vortex forming apparatus and method
Abstract
Apparatus for separating, or classifying according to size,
particles being carried by a primary flow of gas is disclosed. A
vortex is imposed on the primary flow by a vortex forming device in
the form of a central annular hub member having an outer periphery,
angularly spaced nozzles leading to the periphery and an interior
conduit for supplying high pressure gas to the nozzles. The nozzles
are dimensioned and positioned to discharge a ring of high velocity
jets of gas perpendicular to the primary flow and generally tangent
to the periphery to create a vortex to submit the particles to
centrifugal force, facilitating the separation or classification
thereof.
Inventors: |
Schaller; Robin E. (Burnsville,
MN) |
Assignee: |
Donaldson Company, Inc.
(Minneapolis, MN)
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Family
ID: |
26948711 |
Appl.
No.: |
05/474,364 |
Filed: |
May 30, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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261602 |
Jun 12, 1972 |
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Current U.S.
Class: |
95/269; 55/432;
55/447; 137/812; 239/DIG.7; 96/372; 209/722 |
Current CPC
Class: |
B04C
5/02 (20130101); B04C 7/00 (20130101); B04C
3/06 (20130101); B07B 7/086 (20130101); Y10S
239/07 (20130101); Y10T 137/2109 (20150401) |
Current International
Class: |
B04C
5/00 (20060101); B04C 3/00 (20060101); B04C
5/02 (20060101); B04C 7/00 (20060101); B04C
3/06 (20060101); B07B 7/086 (20060101); B07B
7/00 (20060101); B04c 003/00 () |
Field of
Search: |
;137/808-812,604
;239/298,399,403,405,463,DIG.7 ;209/133,144,211
;55/261,447,468,471,476,460 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lutter; Frank W.
Assistant Examiner: Hill; Ralph J.
Attorney, Agent or Firm: Merchant, Gould, Smith &
Edell
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This is a continuation in part of my copending patent application
Ser. No. 261,602, filed June 12, 1972, now abandoned.
Claims
What is claimed is:
1. Apparatus for inertially separating particles from a fluid
medium, comprising:
a. a chamber having an inlet for a flow of particle carrying fluid,
and an outlet;
b. a ring-like vortex forming member mounted in said chamber
between said inlet and outlet, having a central opening and an
outer periphery, passage means including a plurality of spaced
nozzles leading from said central opening to said outer periphery,
and conduit means connected to said central opening for supplying
high pressure fluid to said nozzles;
c. said nozzles being positioned in said vortex forming member to
discharge a ring of high velocity jets of fluid outwardly into said
chamber generally perpendicular to the flow of the particle
carrying fluid and generally tangentially with respect to said
periphery to impose a vortex flow on the flow of particle carrying
fluid and submit the particles to centrifugal force, permitting
separation thereof;
d. each of said nozzles comprising a straight, orifice of length no
greater than its diameter configured to restrict the flow of fluid
and generate a jet of substantially sonic velocity when supplied
with fluid at a suitable pressure; and
e. said periphery of said vortex forming member having curved ramp
surface means formed adjacent each nozzle to enhance the Coanda
effect on each said jet to enhance attachment of the jet to said
periphery of the vortex forming member.
2. The apparatus of claim 1 wherein said outer peripheral surface
of said hub member includes a plurality of generally radially
extending walls each having one of said tangentially directed
nozzles therein, and a like plurality of said ramp surfaces
therebetween, each of said ramp surfaces being curved in a radially
increasing manner downstream from said nozzle to enhance said
Coanda effect.
3. The apparatus of claim 1 wherein a plurality of slots extend
from said central opening into said vortex forming member, wherein
a like plurality of walls are formed in said outer periphery which
extend inwardly a sufficient distance to overlap corresponding
slots, and wherein a nozzle is formed between each said slot and
corresponding wall.
4. Vortex forming apparatus, comprising:
a. a generally cylindrical housing having gas inlet means and gas
outlet means defining a low pressure, high volume gas flow path
therebetween;
b. vortex forming means mounted in said gas flow path, said vortex
forming means including an annular hub member with a central
opening, and with an outer peripheral surface mounted coaxially
with said cylindrical housing, said hub member having passage
means, including a plurality of tangentially directed nozzles,
extending between said central opening and said outer peripheral
surface, each of said nozzles being a straight orifice of length no
greater than its diameter, so as to be capable of generating a jet
having its greatest velocity component downstream from the
orifice;
c. means for supplying a relatively low volume flow of high
pressure gas through said nozzles to discharge jets of gas into
said chamber at substantially sonic velocity to impose a vortex
flow on the low pressure gas flow; and
d. said outer peripheral surface being formed to have a plurality
of curved ramp surfaces formed adjacent said plurality of nozzles
to provide a Coanda effect on the jets to enhance attachment of the
jets to the peripheral surface of the hub member.
5. A method of imposing a vortex flow on a low pressure, relatively
high volume primary flow of a gas, said gas carrying particles to
be separated therefrom, comprising the steps of discharging through
a ring of flow restricting orifices, having lengths no greater than
their diameters, a relatively low volume secondary flow of gas,
positioning the orifices to provide generally tangentially
directed, spaced jets, directing the jets generally perpendicular
to said primary flow, and maintaining said jets at a velocity
generally equal to or greater than sonic velocity to submit the
particles to centrifugal force in the vortex formed thereby.
6. The method of claim 5 including the step of discharging each of
said jets against a Coanda surface to tighten the ring of jets to
improve the vortex forming action thereof.
7. The method of claim 6 including the step of maintaining the
secondary flow volume at approximately 8-10 percent of the primary
flow volume.
8. A particle separator employing vortex forming apparatus,
comprising:
a. a generally cylindrical housing mounted with a longitudinal axis
extending generally vertically and having gas inlet means and gas
outlet means defining a low pressure, high volume primary gas flow
path therebetween, said gas inlet means being an inlet for particle
carrying gas located at a top end of said housing;
b. vortex forming means mounted in said primary gas flow path, said
vortex forming means including a single ring of generally
tangentially directed nozzles positioned to discharge a secondary
flow of gas generally perpendicular to said primary flow, and said
gas outlet means being an axial outlet conduit for clean gas
extending from said top end of said housing and through said ring
of nozzles into said housing;
c. means for supplying a relatively low volume secondary flow of
high pressure gas through said nozzles to discharge jets of gas
into said chamber at substantially sonic velocity to impose a
vortex flow on the low pressure primary gas flow; and
d. a particle collecting chamber mounted at a lower end of said
housing, said vortex subjecting particles carried by said gas
through said inlet to centrifugal forces to permit gravitational
separation thereof from the clean gas being carried out of said
housing through said axial outlet conduit.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to devices for forming a vortex in
a moving flow of fluid, and more particularly relates to apparatus
for imposing a vortex on a primary flow of particle carrying gas to
centrifugally separate the particles from the gas.
DESCRIPTION OF THE PRIOR ART:
It is generally recognized that particles can be separated from a
gas stream by subjecting the particles to the centrifugal force
field present in a vortex flow. In the prior art, the necessary
vortex flow was usually established by inlet vanes, powered rotors
or gas inlet ducts tangent to the outer periphery of a separation
chamber. In such devices, the outwardly directed centrifugal force
is opposed by a particle drag force acting radially inwardly. This
drag force adversely affects particle collection efficiency because
it tends to prevent some particles from reaching the outer
periphery of the separation chamber where scavenging normally
occurs. It occurred to me, after studying the prior art systems and
the forces being developed on the particles to be separated, that
collection efficiency could be enhanced if a vortex flow pattern
were to be established having a radially outwardly directed
velocity component in at least a portion of the primary flow. I
further conceived that such a vortex flow pattern could be imposed
by means of a ring of tangentially directed jets positioned
generally perpendicular to the primary flow. I found that excellent
separation efficiencies could be obtained by utilizing high
velocity, low flow jets. To further enhance the vortex forming
ability of the jets, I provide a suitably curved surface adjacent
to each of the jets to enhance a Coanda effect (that is, attachment
of the jets to the peripheral surface of the vortex forming
member).
A search of the prior art revealed that attempts had been made in
the past to create a vortex by means of a ring of tangentially
directed nozzles. The Ryding U.S. Pat. No. 1,464,113, issued Aug.
7, 1923, discloses a gas cleaner having a tangential dirty gas
inlet to establish an initial whirling motion of the incoming gas,
followed by four rings of tangentially directed nozzles to
accelerate the rotation of the dirty gas. It is evident from
reviewing the Ryding disclosure that Ryding needed the tangential
inlet to fully establish the vortex. Ryding's nozzle design is of
the type normally used with a low pressure supply of air, and the
small ventilation blower of Ryding is not capable of producing jets
traveling at sonic velocity. If Ryding did not have the tangential
inlet, so that the rings of nozzles had to provide all of the
swirl, at least thirty to fifty percent of the outlet flow would
have to be provided by the nozzles in order to obtain a proper
vortex. It is not feasible with vehicle air cleaners, for example,
to provide such a large volume of clean air to the nozzles. Despite
his use of rings of nozzles, Ryding's device is still basically a
low pressure, high flow vortex former.
An air classifier in which a ring of nozzles is used is disclosed
in the Jaeger U.S. Pat. No. 3,483,973, issued Dec. 16, 1969. The
Jaeger classifier is also a low pressure, high flow device, because
100 percent of the flow passes through the nozzles. Jaeger does not
have a primary axial flow of gas that carries the particles to be
separated. In Jaeger, all of the gas flow is through the nozzles,
and the material to be separated is dropped from above into the air
stream created by the nozzles. The Jaeger device is basically a
plurality of tangantial inlets in the form of tangentially directed
low velocity nozzles. It does not differ in kind from other prior
art vortex formers. In general, none of the prior art of which I am
aware is capable of establishing a significant radially outwardly
directed velocity component to aid in overcoming the particle drag
force.
SUMMARY OF THE INVENTION
In the present invention, the vortex is generated by a ring of
tangentially directed, sonic or near sonic-velocity jets
discharging in a direction generally perpendicular to the primary
gas flow. Jet velocities of approximately 1,000 feet per second can
easily be obtained by supplying compressed air at 10-15 psi to a
suitable nozzle or orifice from a compressor. If desired, a
suitable nozzle configuration can be used so as to obtain
supersonic jet velocity.
To enhance the swirl created by the jets, a curved ramp surface is
provided adjacent the outlet of each jet to enhance attachment of
the jet to the surface. This is referred to as the Coanda effect in
fluid mechanics. This Coanda effect tightens the ring of jets to
improve the vortex forming action of the jets. One advantage of the
present invention over prior art structures such as those shown in
Jaeger or Ryding is that this vortex forming device will create a
suitable vortex by itself, without need for tangential inlets or
the like. Another significant advantage is that the present
invention introduces only about 8-10 percent of the total outlet
air in forming the jets. This small amount of air can easily be
supplied by a standard compressor. Tests have shown that with only
8 percent nozzle flow, an air cleaner incorporating the present
invention will separate out virtually 100 percent of all particles
above 10 microns in size, and 50 percent of particles 5 microns in
size. The radially outwardly directed velocity component
established by the ring of high velocity jets tends to throw the
dirt particles outwardly against the walls of the separation
chamber, at which point they can be easily separated from the
remaining axial flow of clean gas. In its broadest sense, the
present invention is a vortex former for an axial gas flow. It can
be used in devices such as air cleaners, including reverse flow air
cleaners, particle classifiers, as a diverter in a pneumatic powder
conveying tube and as a scrubber to clean fine particles from the
air. In the last case, a liquid such as water would be sprayed in
combination with the air nozzles to both scrub and centrifugally
separate dirt particles from the air passing through the vortex.
Other applications for the present invention may occur to those
skilled in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view in side elevation of an air cleaner incorporating
the present invention, portions thereof being shown in section and
portions being broken away;
FIG. 2 is a sectional view taken along line 2--2 of FIG. 1;
FIG. 3 is an enlarged fragmentary sectional view of the vortex
forming device taken along line 3--3 of FIG. 1;
FIG. 4 is a view in perspective of the vortex forming device shown
in FIG. 3;
FIG. 5 is a graph showing the effect of an increasing jet pressure
ratio on air cleaning efficiency given a constant flow
relationship;
FIG. 6 is a graph comparing efficiency of the present invention
with that of a typical low pressure, high flow rate prior art
device;
FIG. 7 shows schematically a typical relationship among inlet flow,
jet inlet flow, scavenge flow and outlet flow in an air cleaner
constructed according to FIG. 1;
FIG. 8 is a schematic elevational view, partly in section, of a
particle classifying device constructed in accordance with my
invention;
FIG. 9 is an enlarged sectional view taken along line 9--9 of FIG.
8; and
FIG. 10 is a vertical sectional view of a reverse flow air cleaner
utilizing the vortex former of my invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The air cleaner of FIG. 1 has a cylindrical housing 10 having an
open dirty air inlet end 11 and an axially located clean air
discharge tube 12. Tube 12 is a cylindrical tube extending through
an end wall 13 of the air cleaner. The inlet end of the tube 12
extends well into the interior of the separating chamber 14 defined
by the housing 10. When the air cleaner is used with an internal
combustion engine, the outer end (not shown) of the tube 12 is
connected to the carburetor intake to provide clean air for
combustion. Tube 12 is of smaller diameter than housing 10 to
provide an annular scavenging chamber 14a between it and the
cylindrical side wall. A scavenging opening 16 is formed in the
cylindrical side wall of housing 10 adjacent end wall 13. A
tangentially extending discharge tube 17 is connected to opening
16. Mounted on the bottom end of tube 17 is an automatic dust
evacuator valve 18. Valve 18 is normally constructed from a
flexible material such as rubber and is provided with a slot or
discharge opening at its bottom end. Fluctuations in pressure
within the system cause the valve to periodically open to discharge
dirt being removed from the air stream by the air cleaner.
A vortex forming member 20 is mounted in chamber 14 between inlet
11 and outlet 12. Vortex forming member 20 includes a closed
cylindrical casing 21 and an annular hub member 22. The outside
diameter of annular hub member 22 is generally equal to the outside
diameter of casing 21. Casing 21 comprises an end cap 21a connected
by means of screws or the like to one face of hub member 22, a
tubular center portion 21b connected at one end to the other face
of hub member 22, and a dome-shaped inlet end cap 21c connected to
the free end of center portion 21b. The cylindrical vortex forming
member 20 is fixedly mounted coaxially with respect to cylindrical
housing 10 by means of a pair of conduit members 24 and 25 each
connected at opposite ends to casing 21 and the side wall of
housing 10. Conduit member 25 extends through the side wall of
housing 10 and is in communication with the interior of casing 21.
The free end of conduit member 25 is adapted to be connected to a
compressor 27 which then supplies air or other gas under pressure
to the interior of closed cylindrical casing 21.
The construction of annular hub member 22 is shown in more detail
in FIGS. 3 and 4. Hub member 22 is an annular, ring-like metal
member having an outer, generally circular peripheral surface 28,
and an inner, generally circular peripheral surface 29 formed
coaxially with surface 28. The inner and outer peripheral surfaces
28 and 29 are connected by parallel, spaced faces 30, 30a. The
downstream face 30 is generally plain while the upstream face 30a
is shown in FIG. 4. Thus, the hub member 22 has a central opening
which is in communication with the interior of casing 21.
The inner peripheral surface 29 and the face 30a define a circular
edge 31. Formed in this edge 31 are a plurality of evenly spaced
pockets or slots 32 which extend radially outwardly through a
predetermined portion of the hub member from inner peripheral
surface 29. As viewed from FIG. 3, the pockets 32 are somewhat
L-shaped, the short leg of the L being remote from surface 29 and
extending generally in the direction of the desired jet formation.
The outer peripheral surface 28 is formed to include a like
plurality of generally radially disposed walls 33 which are located
and extend inwardly a sufficient distance to overlap the
corresponding outwardly extending pockets 32. In the preferred
embodiment, the walls 33 are spaced a short distance from the
closed ends of the previously described L-shaped pockets in the
direction of the jet formation. A hole or orifice 34 is drilled or
otherwise formed through each wall 33 into the outermost end of the
corresponding generally L-shaped pocket 32. The orifices 34 extend
generally tangentially with respect to the outer periphery 28 and
perferably, all of the orifices 34 lie in the same plane so that
when air pressure is provided to the interior of hub member 22, a
ring of generally tangentially directed jets of air is provided
generally perpendicular to the flow of air through the air cleaner.
Each orifice 34 is preferably of much smaller diameter than the
cross sectional dimension of the pocket 32, and the thickness of
the wall is preferably less than the diameter of the orifice. Under
these circumstances the maximum velocity of the jet at the vena
contracta, occurs at or outside the orifice, when it maximizes the
energy interchange between the jet and the axial air flow.
Extending in a downstream direction from the innermost edge of each
wall 33 is a ramp surface 35 that is curved in a radially
increasing manner to enhance the attachment of the adjacent jet to
the surface of the hub member. The orifices 34 are preferably
tangent to the surfaces 35, or substantially so. As shown
schematically in FIG. 3, the resultant jet of air 36 tends to
follow the curved ramp surface 35 to thereby tighten the vortex
being created by the ring of jets.
During operation of the air cleaner of FIGS. 1-4, the engine draws
air through the inlet 11 to comprise a primary flow over the
axially located vortex forming member 20. Because no inlets fins or
tangential inlet is provided, the air initially flows axially
through the housing 10. Compressor 27 is operated to provide
approximately 10-15 psi of air pressure to the interior of casing
21 to supply air under pressure to the pockets 32 and the nozzle
openings 34. The air escaping through the nozzles 34 forms a ring
of high velocity, tangentially directed jets that impose a vortex
on the axial primary flow of air. The jets are directed generally
perpendicular to the primary flow of low pressure air so that the
previously described radially outwardly directed velocity component
is obtained. In FIG. 3, this radially outwardly directed velocity
component is schematically designated Vr while the main jet
velocity vector is designated Vj and the tangential velocity
component is designated Vt. The ring of high velocity jets
immediately imposes a vortex on the axial flow causing the dirt
particles to be thrown outwardly against the cylindrical side wall
from where they are finally discharged through the scavenging
outlet opening 16. The clean air from which the dirt particles have
been removed exits through the clean air discharge tube 12. FIG. 7
schematically compares the various flows through the system. With a
dirty air inlet flow of 100 percent and a clean air outlet flow
(Qo) of 100 percent, a jet inlet flow (Qj) of 8 percent is
sufficient to achieve high air cleaning efficiency. In this case,
the scavenging flow of 8 percent is equal to the jet inlet flow.
Tests were conducted with a jet flow rate (Qj) of 8-10 percent of
the clean air flow (Qo). It was found that for optimum efficiency,
a jet pressure ratio P1/P2 (see FIG. 3) of approximately two should
be maintained across the orifices 34, where the gas geing cleaned
is air, thereby providing sonic gas velocity at the jet throat. As
shown in FIG. 5, an increase of the jet pressure ratio P1/P2 beyond
this value at a constant value of the jet flow ratio Qj/Qo does not
significantly increase collection efficiency. AC fine standard test
dust collection efficiencies of 80 percent with Qj/Qo at 8 percent;
and 85 percent with Qj/Qo at 10 percent, have been obtained. For
particles 10 microns and larger, collection efficiency approached
100 percent. In FIG. 6, the efficiency of the present invention is
compared with typical prior art systems. Assuming a constant jet
pressure ratio P1/P2, FIG. 6 shows that maximum efficiency is
obtained with these jets at a relatively low jet flow ratio Qj/Qo.
The dashed line of FIG. 6 is an estimate of air cleaning efficiency
of a typical low pressure, high flow prior art device such as that
shown in the Ryding patent or in the Oehlrich et al. U.S. Pat. No.
3,199,268, issued Aug. 10, 1965, again assuming a constant jet
pressure ratio. In these prior art devices, it can be seen that a
drastic increase in secondary or jet flow might be provided in
order to obtain high efficiency. In most applications, it is simply
not practical to provide such a large secondary flow.
The air cleaner of FIG. 1 could be changed in a number of ways
without departing from the invention. If desired, the dirty air
inlet 11 could be made tangent to the cylindrical housing to
provide an initial swirl. Although this is not normally necessary,
it may be desirable in some unusual design situations. In like
manner, inlet vanes could also be used to impart an initial swirl
to the air. Particle removal is not restricted to the scavenge
outlet shown in FIG. 1. Any suitable known means of removing
separated particles from the air stream could be used. Other means
for supporting the vortex forming member 20 could also be used. An
aerodynamically-shaped radial support would be one alternative to
the conduit member shown. Some of the advantages of this air
cleaner over prior art air cleaners include increased efficiency,
particularly for particles 5 microns and larger, self-scavenging
(no separate scavenge blower is required), automatic bypassing by
shutting off jet flow Qj when air cleaning is unnecessary (no
separate bypass ducting is required) and ease of preventing icing
in the system.
It should be noted that for any given air cleaner of the type shown
in FIG. 1, there exists an optimum value for the axial distance L
between the vortex forming member 20 and the inlet to tube 12. This
optimum is dependent upon the particular hub-nozzle configuration
that is used, and will have to be determined empirically for any
given air cleaner design. The optimum value corresponds to a
maximum collection efficiency.
FIG. 8 shows a particle classifier having a construction similar to
the air cleaner of FIG. 1. This classifier has a cylindrical
housing 40 with a vaned inlet 41 formed in the cylindrical side
wall adjacent one end thereof to impart an initial swirl to the air
entering the housing. The vortex forming member 42 is constructed
like the vortex forming member of FIG. 1, except that it is bolted
at one end to an end plate 43 of the housing. Again, the vortex
forming member 42 and the cylindrical chamber are coaxially
aligned. The air which carries the particles to be classified thus
enters the vaned inlet 41, which imparts an initial swirl to the
air. The particle carrying air then passes through the vortex
formed by the ring of jets on the vortex forming member 42, as
previously described. A blower 45 is provided to create a suction
through the axially located fine fraction outlet 46. The fine
fraction is collected by a suitable filter means 47 and deposited
in a container 48. The coarse fraction is drawn off through a
tangential outlet 49 by means of a suction created by a blower 50.
The coarse fraction is also separated by a suitable filter 51 and
deposited in a container 52. The cut size can be adjusted by
changing the various air flows and pressures in a manner well known
to those skilled in the art.
FIG. 10 discloses a reverse air cleaner in which the air carrying
the particles to be removed enters the open top end of a
cylindrical housing 55 and passes downwardly through an annular
chamber formed between the housing and the axially positioned
vortex forming member 56. Vortex forming member 56 is mounted on a
high pressure air supply conduit 57 as described for the system of
FIG. 1. In this case, however, the clean gas outlet means is an
axial outlet conduit 58 which extends coaxially through the center
of vortex forming member 56. The bottom end of outlet conduit 58
extends into the separation chamber below the fing of nozzles, and
the upper end of conduit 58 extends upwardly from the top end of
the housing. Attached to the bottom end of cylindrical housing 55
is a truncated cone-shaped portion 55a having attached to the open
bottom end thereof a particle collection chamber housing 59. In
this case, the air passes downwardly through the vortex forming
ring of jets and then reverses flow to pass upwardly through the
axial outlet conduit 58. During passage through the vortex, the
heavier particles are thrown outwardly by centrifugal force against
the walls of the housing where gravity exerts a force causing the
particles to fall downwardly into collection chamber 59. Once
again, the cut size or efficiency is determined by the various air
flows and forces within the system.
* * * * *