U.S. patent application number 10/325201 was filed with the patent office on 2004-06-24 for high strength and ultra-efficient oil coalescer.
This patent application is currently assigned to Honeywell International Inc.. Invention is credited to Iles, Tom L., Scott, Christopher L., Tran, Trung N..
Application Number | 20040118092 10/325201 |
Document ID | / |
Family ID | 32593693 |
Filed Date | 2004-06-24 |
United States Patent
Application |
20040118092 |
Kind Code |
A1 |
Tran, Trung N. ; et
al. |
June 24, 2004 |
High strength and ultra-efficient oil coalescer
Abstract
A coalescing assembly for coalescing entrained oil from a high
temperature, high velocity gas stream comprises a coalescing
element of compacted high temperature polyamide fibers, such as
those available under the trademark Nomex.RTM., rigidly held by
concentric cylindrical support structures of a dense fibrous
material such as stainless steel. The coalescing assembly forms a
component of an oil coalescer having a unique hole configuration in
its outer shell to prevent coalesced oil from being re-entrained
into the gas stream. The oil coalescer is a component of an oil
separator for use in aircraft operational environments and features
high durability and longevity of 10 years or more.
Inventors: |
Tran, Trung N.; (Torrance,
CA) ; Iles, Tom L.; (Rancho Palos Verdes, CA)
; Scott, Christopher L.; (Los Alamitos, CA) |
Correspondence
Address: |
Honeywell International, Inc.
Law Dept. AB2
P.O. Box 2245
Morristown
NJ
07962-9806
US
|
Assignee: |
Honeywell International
Inc.
Law Dept. AB2 P.O. Box 2245
Morristown
NJ
07962-9806
|
Family ID: |
32593693 |
Appl. No.: |
10/325201 |
Filed: |
December 20, 2002 |
Current U.S.
Class: |
55/423 ; 55/486;
55/498 |
Current CPC
Class: |
Y10S 55/05 20130101;
B01D 46/2414 20130101; B01D 46/0031 20130101; Y10S 55/25 20130101;
B01D 2273/20 20130101; Y10T 428/31725 20150401; Y10T 428/31721
20150401; Y10S 55/17 20130101; F05D 2220/323 20130101; B01D 46/0049
20130101; Y10T 428/31681 20150401 |
Class at
Publication: |
055/423 ;
055/498; 055/486 |
International
Class: |
B01D 046/00 |
Goverment Interests
[0001] This invention was made in the performance of work under a
government funded research and development program, F-22 ARS, under
contract number F33657-91-C-0006 to Boeing Military Aircraft and is
subject to the provisions of that contract. The United States
Government may have certain rights to this invention.
Claims
We claim:
1. A coalescing assembly for removing entrained material from a gas
stream, the coalescer assembly comprising a coalescing element
comprised of one or more layers of compacted high temperature
polyamide fibers.
2. The coalescing assembly described in claim 1, further comprising
a support structure for the coalescing element, whereby the
coalescing element is maintained in its compacted state and
oriented so that the gas stream flows through the coalescing
element.
3. The coalescing assembly described in claim 2, wherein the
coalescing element is cylindrical, and the support structure
comprises a cylindrical inner sleeve and a cylindrical outer
sleeve, the coalescing element being contained between the inner
and outer sleeves.
4. The coalescing assembly described in claim 2, wherein the
support structure is comprised of metal fibers felted into sheets
and vacuum sintered to form diffusion bonds between the fibers,
whereby the fibers join in a semi-rigid matrix.
5. The coalescing assembly described in claim 4, wherein the metal
fibers are comprised of stainless steel.
6. The coalescing assembly described in claim 1, wherein each layer
of the coalescing element is comprised of a polyamide having amide
groups separated by meta-phenylene groups, whereby the amide groups
are attached to the phenyl ring at the 1 and 3 positions.
7. The coalescing assembly described in claim 6, wherein each layer
of polyamide fibers has an uncompacted thickness of 0.25".
8. The coalescing assembly described in claim 1, wherein the
coalescing element is comprised of at least three layers of
felt.
9. The coalescing assembly described in claim 1, wherein the
polyamide fibers are comprised of a polyamide having amide groups
separated by meta-phenylene groups, whereby the amide groups are
attached to the phenyl ring at the 1 and 3 positions.
10. The coalescer assembly described in claim 9, wherein the
overall thickness of the compacted polyamide fibers is at least
0.25".
11. An oil coalescer for removing entrained oils from a gas stream,
the coalescer assembly comprising a cylindrical coalescing element
comprised of compacted polyamide fibers; a support structure
comprised of a cylindrical inner sleeve and a concentric
cylindrical outer sleeve enclosing the coalescing element
therebetween, the inner sleeve defining an inner area and having
openings allowing fluid communication between the coalescing
element and the inner area; a cylindrical shell enclosing the inner
and outer sleeves and the coalescing element; a top cap enclosing
an upper portion of the cylindrical shell; a bottom cap with drain
holes, the bottom cap enclosing a lower portion of the cylindrical
shell; and, a diverging channel in fluid communication with the
inner area, the diverging channel directing the gas stream through
an orifice in the top cap into the inner area.
12. The oil coalescer described in claim 11, wherein the polyamide
fibers are comprised of a polyamide having amide groups separated
by meta-phenylene groups, whereby the amide groups are attached to
the phenyl ring at the 1 and 3 positions.
13. The oil coalescer described in claim 11, wherein the outer
shell has lower holes only along the lower portion of the
shell.
14. The oil coalescer described in claim 13, wherein the lower
holes wrap around the bottom cap to also function as drain
holes.
15. An oil separator for removing entrained oils from a gas stream
and returning the oils to a sump of a compressor, the oil separator
comprising an oil coalescer; an input orifice directing the gas
stream to an inner area of the oil coalescer, wherein the velocity
of the entering gas steam is reduced through the use of adiabatic
expansion; a collection area for collecting oil removed from the
gas stream by the oil coalescer; and a passage from the collection
area, wherein collected oil is removed from the oil separator to
prevent overflow.
16. The oil separator described in claim 15, wherein the oil
coalescer is comprised of a coalescing element having one or more
layers of compacted polyamide or polyimide fibers, and a support
structure having a cylindrical inner sleeve and a cylindrical outer
sleeve, the coalescing element being contained between the inner
and outer sleeves, whereby the coalescing element is maintained in
its compacted state by the sleeves and oriented so that the gas
stream flows through the coalescing element.
17. The oil separator described in claim 16, wherein the layers of
the coalescing element are made of a polyamide having amide groups
separated by meta-phenylene groups, whereby the amide groups are
attached to the phenyl ring at the 1 and 3 positions.
18. The oil separator described in claim 16, wherein each layer has
an uncompacted thickness of 0.25".
19. The oil separator described in claim 16, wherein the overall
thickness of the compacted polyamide layers is at least 0.25".
20. A method of compacting a polyamide felt comprising the steps of
preparing a rectangular strip of felt by tapering the ends thereof;
compacting the rectangular strip; heating the compacted rectangular
strip; allowing the compacted rectangular strip to cool; assembling
the compacted rectangular strip into a cylindrical assembly;
compacting the cylindrical assembly; and heating the compacted
cylindrical assembly.
21. The method described in claim 20, wherein the polyamide felt
has a thickness of 0.25".
22. The method described in claim 20, wherein the step of heating
the rectangular strip comprises heating the rectangular strip for 4
hours at a temperature of about 250.degree. F.
23. The method described in claim 20, wherein the step of heating
the compacted cylindrical assembly comprises heating the compacted
cylindrical assembly for 4 hours at a temperature of about
250.degree. F.
24. The method described in claim 20, wherein the step of
assembling the compacted rectangular strip into a cylindrical
assembly comprises the steps of wrapping the compacted rectangular
strip around a cylindrical shape and rigidly maintaining the
cylindrical shape.
25. A method for coalescing oil from a gas stream having an aerosol
of oil droplets entrained therein, the gas stream flowing through a
channel, the method comprising the steps of reducing a velocity of
the gas stream by adiabatic expansion by means of a diverging
channel, directing the gas stream to an oil coalescer comprising a
coalescing element supported by a rigid support structure,
directing the gas stream through the coalescing element to remove
the entrained oil droplets; collecting the removed oil droplets
within the oil coalescer for removal from the channel; and allowing
the purified gas flow to continue through the channel.
26. The method described in claim 25, wherein the coalescing
element is comprised of a felt of compacted polyamide fibers.
27. The method described in claim 26, wherein the polyamide fibers
are comprised of amide groups separated by meta-phenylene groups,
whereby the amide groups are attached to the phenyl ring at the 1
and 3 positions.
Description
BACKGROUND OF THE INVENTION
[0002] The present invention relates to the field of filtration
and, in particular, to ultra-efficient filters, separators, and
coalescers for separating entrained aerosols from a gas flow.
[0003] Certain gas streams, such as blow-by gases from piston
compressors found in air recharge systems typically found in
aircraft, carry substantial amounts of oils entrained therein, in
the form of an aerosol. These oils are required to lubricate the
piston compressor to ensure its long life operation. The majority
of the oil droplets within the aerosol range in size from 0.1
microns to 5.0 microns. Coalescence methods using fibrous filters
are generally used to remove this oil-based aerosol. Such methods
rely on the following physical mechanism: (1) interposing a fibrous
filtration means-into a gas stream containing the aerosol so that
the aerosol droplets are allowed to approach the fibers, (2)
attachment of the droplets to the fibers, (3) coalescence of
attached droplets on the fiber so as to create enlarged droplets,
and (4) release of enlarged droplets to a collection area under the
influence of gravity or centrifugal force when their weight exceeds
a certain threshold.
[0004] Coalescent filters contain fibers, structured with various
pore sizes, that are adherent to the aerosol. These filters are
sometimes combined with a particle filter and a separator, such as
an oil separator, to remove contaminant particles from the stream
or to remove oils present in the gaseous stream for return to the
sump of the piston compressor for reuse as lubrication. Additional
filters that can be used include composite fiber-mesh filters and
the like. Mesh filters contain fibers of, for example, polyester,
polypropylene, nylon, Teflon, Nomex.RTM., Viscose, or combinations
of these materials. These fibers have a variety of pore sizes and
are commercially available. Nomex.RTM. is a registered trademark of
E.I. du Pont de Nemours and Company, Wilmington, Del. It is a
polyamide in which all the amide groups are separated by
meta-phenylene groups; that is, the amide groups are attached to
the phenyl ring at the 1 and 3 positions.
[0005] Aircraft environments present a special set of problems for
such oil coalescers. Cabin air is generally obtained from the
blow-by air stream from the turbine engines propelling the
aircraft. This air stream is extremely hot, has a high velocity,
and contains an aerosol of oil and other contaminants produced by
the turbine engine or by auxiliary compressor components. Removal
of contaminants from such an air stream imposes unique requirements
upon filtration and conditioning systems therefor, and in
particular, upon oil coalescer devices.
[0006] U.S. Pat. No. 6,355,076, issued to Gieseke et al., discloses
an oil separation and coalescing apparatus for removing entrained
oils from an aerosol. It comprises a first coalescer filter with a
non-woven media of fibers having a panel construction and a second
coalescer filter with a pleated construction. It is designed for
applications with diesel engines such as those typically found in
trucks. Its temperature and gas velocity limitations are those
typically found in trucks and not in aircraft environments, and
more specifically, in aircraft piston compressors.
[0007] Oil coalescers, such as those made, for example, by
Micro-Filtration, Inc., a subsidiary of Numatics, headquartered in
Lapeer, Mich., are typically used to remove contaminants from gas
streams. Such oil coalescers have been shown in testing to be
unable to withstand the pressures resulting from high velocity gas
streams, resulting in the disintegration of the coalescing element,
i.e., filter; the particles of the disintegrated oil coalescer
element are swept downstream of the oil coalescer to clog other
system components and ultimately cause them to fail. They do not
exhibit the structural integrity necessary to withstand the
decompression rates and high temperatures present in the aircraft
operational environment. Furthermore, the oil removal efficiency of
these fiber-porous coalescers is only about 90% to 95%. It is
desirable to attain an ultra-efficiency of 97% or higher for oil
coalescers in an aircraft environment.
[0008] Oil coalescers currently used in aircraft air conditioning
systems are typically bulky and have a moderate oil removal
efficiency of 75%-85%. Such efficiency becomes more difficult to
attain, as the coalescer becomes more compact. Because of the
premium placed on space in an aircraft, it is desirable that the
oil coalescer be light and compact, in order to augment operational
efficiency of the aircraft and allow it to carry more equipment.
Finally, a long service life of 10 years or more is desirable since
it reduces the maintenance requirements for the aircraft piston
compressor, making it cheaper to operate.
[0009] As can be seen, there is a need for an oil coalescer for use
in an aircraft piston compressor for the removal of entrained
aerosols from a high velocity gas, where the coalescing element is
ultra-efficient (i.e. oil removal efficiency in excess of 97%) and
vibration resistant. It is also desirable to provide an oil
coalescer that is compact, has a long service life, and rugged
enough to endure a continuous pressure presented by a high velocity
gas stream and the decompression rates found in the aircraft's
operational environment.
SUMMARY OF THE INVENTION
[0010] In one aspect of the present invention, a coalescing
assembly for removing entrained oil from a gas stream is provided.
The coalescing assembly comprises a coalescing element made of one
or more layers of compacted, high temperature polyamide fibers.
[0011] In another aspect of the present invention, an oil coalescer
is provided for removing entrained oils from a high velocity, high
temperature gas stream. The inventive oil coalescer comprises a
cylindrical coalescing element of compacted high temperature
polyamide fibers held in a compacted state by a support structure
comprised of a cylindrical, concentric inner and outer fiber-metal
sleeves enclosing the coalescing element therebetween. The
coalescing element with its support structure is encased by a
cylindrical shell, a top cap, and a bottom cap. The cylindrical
shell has holes along its lower periphery to allow the gas stream
to escape the coalescer without entraining oils that have already
been removed, and the bottom cap has holes permitting coalesced oil
to drain from the oil coalescer. The oil coalescer also features a
diverging channel directing the gas stream through an orifice in
the top cap into the inner area, and thereby reducing its velocity
by means of adiabatic expansion.
[0012] In still another aspect of the present invention, a method
for compacting a polyamide felt is given, the method comprising the
steps of preparing a rectangular strip of felt by tapering the ends
thereof; compacting the rectangular strip; heating the compacted
rectangular strip; allowing the compacted rectangular strip to
cool; assembling the compacted rectangular strip into a cylindrical
assembly; compacting the cylindrical assembly; and heating the
compacted cylindrical assembly.
[0013] In yet another aspect of the invention, an ultra-efficient
coalescing element is provided which is comprised of compacted high
temperature polyamide fibers such as those available under the
trademark NOMEX (aramid fiber) and KEVLAR from DuPont. The
coalescing element is preferably comprised of three layers of
Nomex.RTM. felt, each layer having an uncompacted thickness of
0.25", the three layers being compacted to a total thickness of
0.25".
[0014] In still another aspect of the invention, a method is
provided for coalescing oil from a high velocity, high temperature
gas stream, the gas with an entrained aerosol, flowing through a
channel, which comprises the steps of reducing the velocity of the
gas stream by adiabatic expansion through a diverging channel,
directing the gas stream to an oil coalescer comprising a
coalescing element supported by a rigid support structure,
directing the gas stream through the coalescing element, collecting
the removed aerosol material within the oil coalescer for removal
from the channel, and allowing the purified gas flow to continue
through the channel.
[0015] These and other features, aspects and advantages of the
present invention will become better understood with reference to
the following drawings, description, and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows a cross sectional view of an oil coalescer,
according to an embodiment of the invention;
[0017] FIG. 2 shows the external side view of an oil coalescer,
according to an embodiment of the invention;
[0018] FIG. 3 shows a bottom view of an oil coalescer, according to
an embodiment of the invention;
[0019] FIG. 4 shows a cross sectional view of an oil separator
having oil coalescer installed therein, according to an embodiment
of the invention; and
[0020] FIG. 5 illustrates the manner in which the Nomex.RTM. felt
is compacted to the desired thickness.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The following detailed description shows the best currently
contemplated modes of carrying out the invention. The description
is not to be taken in a limiting sense, but is made merely for the
purpose of illustrating the general principles of the invention,
since the scope of the invention is best defined by the appended
claims.
[0022] The invention provides a high-strength ultra-efficient oil
coalescer that separates an entrained oil in the form of an aerosol
from a high-velocity gas stream. The inventive oil coalescer
combines the strength of stainless-steel fibers and the coalescing
efficiency of Nomex.RTM. felt into an oil coalescer comprising a
coalescing element and a support element having support structures.
The coalescing element may be comprised of highly porous, compacted
Nomex.RTM. felt sandwiched between support structures preferably
comprised of two concentric, coaxial cylinders. The cylinders are
constructed of a durable material of dense, woven fibers such as
stainless steel. As an example, three layers of 0.25" thick
Nomex.RTM. felt (for a total thickness of 0.75") are compacted into
a 0.25" space between the two cylindrical support structures to
provide a Nomex.RTM. density that may be higher than normal and to
increase the oil retention efficiency of the coalescing element.
Oil separation may be achieved by reducing the velocity of the
aerosol-laden air stream and directing it from the inside of the
integral stainless-steel/Nomex.RTM. coalescer assembly to the
outside of the coalescer assembly, thereby allowing the aerosol of
entrained oil droplets to come in contact with the Nomex.RTM.
fibers. The oil removed from the gas stream by coalescence collects
at the bottom of the oil coalescer and purified air exits through
openings in the housing surrounding the oil coalescer. The
collected oil may be drained through unique optimum slot openings
between the support core and the bottom cap surrounding the oil
coalescer. This compact and integral oil coalescer provided by the
invention has been shown to have an oil removal efficiency of
97.5%, with the support structure providing sufficient strength to
sustain the high vibration and depressurization levels found in an
aircraft operational environment.
[0023] The oil coalescer of the present invention exhibits a number
of inventive improvements over the prior art. First, previous oil
coalescer devices allowed a certain amount of coalesced oil to be
re-entrained into the gas stream, which reduced the efficiency of
the device. The oil coalescer of the present invention has a unique
design built into the bottom cap and cylindrical shell to maximize
the oil flow to the drain and to prevent the oil from returning to
the purified airflow by means of entrainment. Second, existing
coalescing filters were tested under the conditions found in the
aircraft environment and were found to lack both the durability to
withstand high velocity gas streams having pressures of 5,380 psig
and the ability to withstand temperatures in the general range of
400.degree. F. to 450.degree. F. without disintegrating and
introducing debris into the system. The inventive use of Nomex.RTM.
as the coalescing element in the present invention coupled with the
durable support structure that orients the coalescing element to
the gas stream has been shown to have the required durability.
Third, the efficiency for prior art oil coalescers for the removal
of aerosols of entrained oils was only about 90% to 95%. The novel
use of compacted Nomex.RTM. has been shown to exhibit oil removal
efficiencies in excess of 97.5% and has not been described or
suggested by the prior art.
[0024] Directing attention now to FIG. 1, a side cross-sectional
view of an embodiment of the oil coalescer 100 is shown. Oil
coalescer 100 may comprise a shell 110 with top cap 120 and bottom
cap 130. A central shaft 123 may be integral to and extend
downwardly from top cap 120. A chamber 102 for receiving an
incoming gas stream may be axially positioned in the upper end of
central shaft 123, with the chamber 102 in fluid communication with
the internal cavity 135 by one or more nozzles 103 radially located
about the lower end of chamber 102. The distal end 126 of central
shaft 123 may be threaded to receive a lock nut 127, so that the
shell 110 may be captured between top cap 120 and bottom cap 130
when lock nut 127 is tightened against bottom cap 130. Lock nut 127
may be easily loosened to remove the bottom cap 130 and allow the
coalescing assembly 140 to be inserted into the internal cavity 135
within shell 110. To prevent leak paths, high temperature sealant,
such as Loctite.RTM. 272, may be applied to seal both ends of the
coalescing assembly 140 to the two end caps 120, 130 and in between
bottom cap 120 and central shaft 123. Loctite.RTM. is a registered
trademark of Loctite Corporation.
[0025] A coalescing assembly 140 may be a cylindrical assembly
having a diameter less than that of shell 110, to allow it to be
inserted within shell 110 with central shaft extending through
coalescing assembly 140. The coalescing assembly 140 may be
comprised of an inner support structure 141 surrounded by an outer
support structure 142, the support structures 141, 142 sandwiching
a coalescing element 143 therebetween. A top flange 122 can extend
downwardly from the lower surface 121 of top cap 120. Top flange
122 may be circular and centered around centerline 190. A bottom
flange 132 can extend upwardly from the upper surface 131 of bottom
cap 130. Bottom flange 132 may also be circular and centered around
centerline 190. The flanges 122, 132 oppose each other and can be
configured to snugly receive the outer support structure 142 and
the shell 110, keeping both axially aligned and centered about
centerline 190.
[0026] Coalescing element 143 may be comprised of polyimide or
polyamide fibers compacted according to the invention and described
herein, and preferably of Nomex.RTM. fibers comprised of a
polyamide having amide groups separated by meta-phenylene groups,
i.e. the amide groups are attached to the phenyl ring at the 1 and
3 positions. It has been found that compacted Nomex.RTM. fibers, as
opposed to uncompacted Nomex.TM. fibers normally supplied as
Nomex.RTM. felt, can increase the efficiency of the oil coalescing
assembly to remove aerosol of entrained oil from the gas stream.
One or more layers of Nomex.RTM. felt can be compacted by heat
compression methods, as further described below, and maintained in
a compacted state by the sandwiching action of the support
structures 141, 142. As an example, three layers of 0.25" thick
Nomex.RTM. felt (for a total thickness of 0.75") are compacted into
a 0.25" space between support structures 141, 142, to provide a
Nomex.RTM. density that may be higher than normal and to increase
the oil retention efficiency of the coalescing element 143.
[0027] Support structures 141, 142, can provide the functions of
prefiltering large particles from the gas stream and of rigidly
supporting coalescing element 143 so that coalescing element 143
may withstand the pressures exerted by the high velocity gas stream
exerting pressures in excess of 5000 psig as the stream is directed
across the coalescing element 143, as well as the vibration levels
experienced in an aircraft environment. Each support structure 141,
142 may be constructed of a durable material, such as stainless
steel, in the form of a dense, permeable, and fibrous material, for
containing the coalescing element 143 between the support
structures in the presence of the previously described high
internal pressures tending to force the gas stream outwardly from
the internal cavity 135.
[0028] The dense fibrous material from which the support structures
141, 142 are formed may be advantageously comprised of raw metal
fibers, such as stainless steel, having a typical length to
diameter ratio of approximately 90:1. The raw metal fibers may be
felted into sheets and vacuum sintered to form diffusion bonds
between the fibers, so that the fibers are in a semi-rigid matrix
so that they may easily be cut to size. Such material obtained from
Technetics Corporation, DeLand, Fla., can be used in this
application and exhibits screen properties of 18 mesh (a "mesh" is
a measurement typically used in filtration applications and
indicates that an equivalent screen having 18 strands per inch in
two orthogonal directions will have the same filtering properties
as the material being measured.) The sintered metal fibers
comprising support structures 141, 142 have sufficient strength to
support the coalescing element 143 against a high velocity gas
stream so that the coalescing element 143 maintains its integrity
and does not disintegrate under high pressure rapid
decompression.
[0029] An exemplary method for compacting the Nomex.RTM. felt to
the desired thickness is illustrated in FIG. 5. A generally
rectangular-shaped strip 500 having a width C generally the same as
that of the coalescing assembly may be cut from a piece of
Nomex.RTM. felt having a thickness of approximately 0.25" (A) and
both ends 510, 520 of the strip 500 are sanded to gradually taper
the ends so that it may conform more easily to a cylindrical shape
when rolled. Next, the rectangular strip 500 may be compacted
between two metal plates 530 to a thickness of approximately
0.083", as an example, and held to that thickness by C-clamps 540
or any other appropriate means. The assembly 535 comprised of the
compacted strip 500 as held by the metal plates 530 may be placed
in an oven for a minimum of 4 hours at a temperature of 250.degree.
F..+-.10.degree. F. The assembly 535 may be allowed to cool in the
oven in the presence of dry air until the temperature of the
assembly 535 reaches a temperature of 120.degree. F. or lower, at
which time the C-clamps 540 and metal plates 530 are removed from
the now compacted strip 500. Before the compacted strip 500 is
allowed to cool further, and preferably within 10 minutes or less,
the compacted strip 500 may be tightly wrapped around a tube 550
having a 0.5" OD, as an example, or similar cylindrical support
structure, until three layers are achieved. The wrapped strip 500
may then be covered with a copper sheet 560 held around the wrapped
strip 500 by hose clamps 570 or similar devices. The hose clamps
570 are then tightened gradually and equally until the diameter of
the wrapped strip 500 and copper sheet 560 assembly 575 achieves a
diameter of between 1.00" and 1.05". The assembly 575 may be
returned to the oven where it may again be heated to 250.degree.
F..+-.10.degree. F. and held at that temperature for another 4
hours minimum. At the end of this time, the assembly 575 may be
allowed to cool in the oven in the presence of dry air until the
temperature of the assembly reaches 120.degree. F. or lower. At
this point, the now cylindrical strip 500 should be removed from
the copper sheet fixture and immediately assembled between the two
inner and outer cylindrical support structures within approximately
four hours removal of the copper sheet fixture from the oven;
otherwise, it may begin to expand to its original uncompacted
shape.
[0030] The shell 110, as illustrated in FIG. 2, can have two rows
of holes, one row of holes 150 entirely along the circumference of
shell 110 and another row of holes 151 partially on the
circumference and partially on the bottom cap (FIG. 3), both rows
situated along the lower portion 111 of shell 110. Ordinary filter
and coalescer assemblies have holes along the entire surface area
of the outer shell. It has been found that having holes only along
the lower portion 111 of the shell 110 advantageously prevents
coalesced oil from being re-entrained entrained into the gas
stream, while at the same time allowing the coalesced oil to be
removed through the lower row of holes 151.
[0031] FIG. 4 shows an oil separator 400 of which the oil coalescer
100 may be a component. The oil coalescer 100 may be enclosed in an
outer shell 430 that has been lined with a heat resistant lining
440. A high velocity, high temperature gas stream, exerting
pressures in excess of 5000 psig and having temperatures of
400.degree. F. to 450.degree. F., as indicated by arrow 451, enters
the input orifice 410 of the oil separator 400 where it enters
chamber 102 and expands, thus losing a portion of its velocity
through adiabatic expansion. The gas stream flows through nozzle
103 into the internal cavity 135 of the coalescer assembly, as
indicated by arrows 452, where it may be forced by the pressure of
the gas stream flow through the coalescing element 143. A plurality
of nozzles 103, with three equidistantly positioned nozzles being
preferred, are located along the lower portion of chamber 102. They
serve to further reduce the velocity of the incoming gas stream by
providing multiple entry points to internal cavity 135.
[0032] Oil entrained in the gas stream coalesces on the fibers of
the coalescing element 143 while the gas stream emerges from the
lower holes in the shell 110. From that point, the oil-free gas
stream flows upwardly, as indicated by arrows 454, and enters a
two-hole diverter before exiting the oil separator via the exit
orifice 420. The coalesced oil flows as by gravity out through the
bottom cap 130, as indicated by arrows 456 to collect in the lower
portion of the outer shell 430, to be returned to the oil sump for
the aircraft compressor by the automatic opening of an oil return
shuttle valve whenever the oil separator internal pressure drops to
approximately 100 psig or less (not shown.)
[0033] The inventive oil coalescer has been shown to provide
superior performance for the removal of entrained oil from aircraft
piston compressor applications. The inventive oil coalescer
features support assembly providing the strength and heat
resistance of stainless-steel fibers felted into sheets and vacuum
sintered to form diffusion bonds between the fibers, resulting in a
semi-rigid matrix. The support assembly functions as a pre-filter
for removing larger particles from the gas stream and as a support
to allow the coalescing element to withstand the pressures and
temperatures of the gas stream. The inventive oil coalescer also
has a coalescing element providing the high oil removal efficiency
of compacted Nomex.RTM. felt. This oil coalescer may be used in a
unique oil separator with an inventive mechanical design that
reduces the inlet flow velocity while providing the optimum oil
drain path for more efficient separation of entrained oil from a
high velocity, high temperature gas stream. This inventive oil
coalescer exhibits the oil removal ultra-efficiency of 97.5% and
may be used in applications other than aircraft, where the removal
of entrained oils from gas streams is required.
[0034] It should be understood, of course, that the foregoing
relates to preferred embodiments of the invention and that
modifications may be made without departing from the spirit and
scope of the invention as set forth in the following claims.
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