U.S. patent number 3,692,140 [Application Number 05/130,989] was granted by the patent office on 1972-09-19 for exhaust noise suppressor for gas turbine.
Invention is credited to Cloyd D. Smith.
United States Patent |
3,692,140 |
Smith |
September 19, 1972 |
EXHAUST NOISE SUPPRESSOR FOR GAS TURBINE
Abstract
An exhaust noise suppressor is provided for a gas turbine. The
turbine has an upwardly opening exhaust discharge port, and the
suppressor is mounted thereabove, with its exhaust intake port
receiving the turbine exhaust. The suppressor comprises an
elongated exterior shell, leading from the intake port to a stack,
and inside thereof is a perforated interior wall structure or
liner, spaced inside the shell walls to provide a space for a
packing of high heat resistant sound insulation material. The
interior perforated liner attains a high temperature, e.g., of the
order of 1,100.degree. F., and is subject to substantial thermal
expansion. The invention features an arrangement by which the
interior liner is free for thermal expansion within the
longitudinal direction of the shell, as well as transversely
thereof. The turbine exhaust gas entering the intake port of the
turbine casing opens inside a perforated conical diffuser, which
reduces back pressure on the turbine to an important degree.
Running down the center of the longitudinal gas passage in the
casing is a sound absorbing structure comprised of perforated side
walls containing high heat resistant sound absorbing material. The
perforated walls are covered with fiber glass cloth.
Inventors: |
Smith; Cloyd D. (Pacific
Palisades, CA) |
Family
ID: |
22447364 |
Appl.
No.: |
05/130,989 |
Filed: |
April 5, 1971 |
Current U.S.
Class: |
181/213 |
Current CPC
Class: |
B64F
1/26 (20130101) |
Current International
Class: |
B64F
1/26 (20060101); B64F 1/00 (20060101); B64d
033/06 (); F01n 001/10 (); F01n 007/18 () |
Field of
Search: |
;181/33F,33R,33A,33D,33G,33H-HE,36B,42,46,48,50,55,56,59,61-63,64A,68,69 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
|
525,721 |
|
May 1956 |
|
CA |
|
1,112,226 |
|
Nov 1955 |
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FR |
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1,391,884 |
|
Feb 1965 |
|
FR |
|
865,661 |
|
Apr 1961 |
|
GB |
|
890,106 |
|
Feb 1962 |
|
GB |
|
Primary Examiner: Ward, Jr.; Robert S.
Claims
I claim:
1. In a noise suppressor, the combination of:
a stationary elongated exterior sheet metal shell;
an elongated perforated interior liner conduit inside said shell
and extending longitudinally thereof;
said liner being spaced inside said shell;
packing of high heat resistant, noise-absorbent material in the
space between said shell and said liner;
flexible resilient support means supporting said liner from said
shell in its spaced position inside the shell, said support being
attached to one of said shell and liner, and being in slidable
engagement with the other of said shell and liner, accommodation to
transverse thermal expansion of the liner, and to permit
longitudinal shifting of the liner relative to the shell with
longitudinal thermal expansion of the liner.
2. The subject matter of claim 1, wherein said supports are
attached to said liner and are in slidable engagement with said
shell.
3. The subject matter of claim 1, including also a gas intake
fitting opening into said liner through said shell in the region of
one end portion of said shell, and
a stack opening from said liner through said shell in the region of
the other end portion of said shell.
4. The subject matter of claim 3, wherein said gas intake embodies
a frusto-conical perforated diffuser.
5. The subject matter of claim 3, including also sound absorber
means inside said liner and extending longitudinally thereof, said
absorber means being between said gas intake and said stack.
6. The subject matter of claim 5, wherein said sound absorber means
embodies a panel dividing said liner into two longitudinal gas
passage ways, said panel comprising a pair of parallel perforated,
sheet metal side plates on opposite sides thereof, and high heat
resistant, noise-absorbent material packed between said plates.
7. The subject matter of claim 6, wherein said side plates converge
smoothly at opposite ends of the absorber to a relatively thin
edge.
8. The subject matter of claim 7, wherein said absorber includes a
solid sheet metal plate between said perforated side plates.
9. The subject matter of claim 3, wherein said gas intake extends
laterally through the sides of said liner and shell and is fixed to
said shell and loosely connected to said liner, and
said stack is fixed to said liner and extends laterally therefrom
through a side of said shell,
there being a thermal expansion gap in said shell for said
stack.
10. In a noise suppressor, the combination of:
a stationary, elongated exterior sheet metal shell, of rectangular
cross-section, of greater horizontal width than vertical
height,
an elongated, perforated interior liner conduit spaced inside said
shell and extending parallel to and longitudinally of said
shell;
packing of high heat resistant noise-absorbent material in the
space between said perforated liner and said shell,
flexural and slidable supports between said liner and said shell
supporting said liner for thermal expansion in transverse
directions and for longitudinal thermal expansion by longitudinal
shifting of the liner relative to the shell,
a gas intake fitting extending upwardly through adjacent bottom
walls of said shell and said liner near one end of said shell for
discharging exhaust gas inside said liner, said intake fitting
being affixed to said shell, and
a stack extending upwardly from the end of said liner and through
the top of said shell near the opposite end of said shell, said
stack being affixed to said shell.
11. The subject matter of claim 10, including an expansion joint in
said top of said shell for said stack.
12. The subject matter of claim 10, wherein said gas intake fitting
embodies a perforated frusto-conical diffuser, with a closure at
its upper end, disposed in said liner.
13. The subject matter of claim 10, wherein the walls of said shell
mounts rails slidably engaged by said flexural supports, and said
supports are fixed to said liner.
14. In a noise suppressor, the combination of:
a stationary, elongated interior sheet metal shell, of rectangular
cross-section, of greater horizontal width than vertical
height;
an elongated, perforated interior liner conduit spaced inside said
shell and extending parallel to and longitudinally of said
shell;
packing of high heat resistant noise-absorbent material in the
space between said perforated liner and said shell;
a gas intake fitting extending upwardly through adjacent bottom
walls of said shell and said liner near one end of said shell for
discharging exhaust gas inside said liner;
a stack extending upwardly from the end of said liner and through
the top of said shell near the opposite end of said shell, and
a horizontal sound absorber panel mounted in said liner between
said gas intake fitting and said stack, and dividing the space
inside said liner into two parallel upper and lower gas
passages.
15. The subject matter of claim 10, including also deflector means
in and below said stack and within said liner for preserving a gas
passage from the liner into the stack in event of snow accumulated
in said liner received therein through said stack.
Description
FIELD OF THE INVENTION
This invention relates generally to suppressors for the exhaust
discharge noise of stationary gas turbine installations for use as
the prime mover for electric generators, for example. A typical
turbine installation may drive a 750 watt electrical generator, for
example, and the exhaust noise from such a turbine may be very
loud, and, at a distance of 50 feet, may exceed levels of tolerance
for workmen or other personnel having business in the vicinity.
Accordingly, efforts are now commonly made to reduce the intensity
of the noise at the gas discharge outlet of a gas turbine. These
efforts have not heretofore been sufficiently successful, and it is
a purpose of the invention to provide a practical gas turbine
exhaust noise suppressor which is capable of reducing the noise
level in the vicinity of the turbine to a degree materially below
the best heretofore available, and which will permit personnel to
remain indefinitely as close as approximately 50 feet to the
turbine, without use of ear protectors, and without liability of
ear damage.
BRIEF DESCRIPTION OF THE INVENTION
The invention provides an exterior shell, and a perforated liner
positioned therein, with an intervening spacing therebetween for a
packing of high heat resistant sound insulation therebetween. The
liner receives combustion gases through an intake port opening
inside the shell, and preferably through a divergent perforated
diffuser, and the heated gases then flow through the liner to a
combustion gas discharge stack, and on its way pass over the
perforated liner surfaces over the mineral wool sound insulation
material. The invention has special provisions for minimized heat
transfer from the liner to the shell, and also for thermal
expansion of the liner inside the shell. It features also a
configuration of sound absorbers inside the liner leading to a
surprising extent of acoustic attenuation.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal sectional view through a present preferred
embodiment of the invention;
FIG. 2 is a transverse section on line 2--2 of FIG. 1;
FIG. 2A is an enlarged fragmentary view of the area encircled by
the arrow 2A of FIG. 1;
FIG. 3 is a plan view of the gas intake end of the suppressor;
FIG. 4 is an exploded view of the suppressor of FIGS. 1, 2, and
3;
FIG. 5 is a cross-sectional view of a modified embodiment of the
invention; and
FIG. 6 is a graph showing sound intensity in decibels vs. sound
frequency.
DESCRIPTION OF A PREFERRED EMBODIMENT
In the drawings, an elongated, horizontally disposed sheet steel
shell or conduit is designated at 10, with a gas intake fitting 11
opening into its bottom near one end, and a stack 12 leading
upwardly from the top near its other end. The stack may, if
desired, be increased in height, as suggested at 12a, but normally
uses just the short stack 12.
The shell 10 comprises side walls 13, and top and bottom walls 14
and 15. The shell has in addition opposite end walls 16 and 17. In
the present illustrative embodiment, the design concept of the
conduit has in view a minimized vertical dimension to permit
hauling on a truck on the streets without exceeding height limits.
Accordingly, the shell is box shaped, relatively flat, short and
wide in cross-section. In other situations, where minimization of
vertical height is not a factor, a more economical shape is round
(see FIG. 5 ), i.e., cylindrical, and such a shape is an optional
alternative. However, the flat shape of the presently described
embodiment maximizes the area of later described sound absorption
walls for a given gas flow, and is an important improvement when
maximized sound suppression is paramount.
Spaced inside the exterior shell 10, for reception of an
intervening layer of heat resistant sound insulation material, is a
perforated sheet steel liner 18, comprised of perforated side walls
20, a perforated bottom wall 21, perforated end walls 22 and 23,
and a perforated top wall 24. The perforations are preferably
one-eighth to three thirty-seconds inch holes, on three-sixteenths
inch staggered centers. The liner walls may be one-eighth inch in
thickness.
Bent inwardly from the upper edge of end wall 16 of shell 10 is a
top flange 25, which forms an end portion of the top of the shell.
The edge of this flange 25 is abutted by the ends of legs 26 of the
top wall 14 of the shell, formed by notching into the end of wall
14 to receive the stack 12. The stack 12 is rectangular in cross
section, and to its lower end are affixed the vertical flanges of
supporting angle irons 29, the horizontal flanges of which extend
horizontally outward, and rest down on top wall 14 and the top
flange 25 for support. The perforated liner has a rectangular
opening 30 at the stack end of the suppressor which is defined by
portions of side and end walls 20 and 22, respectively, extending
upwardly above the level of liner top wall 24, and by an upwardly
slanting extension 31 from wall 24, and a short vertical wall 32 at
the top of the latter. These wall members are snugly received at
the top inside the lower end of the stack. The edge of flange 25 is
normally (when the apparatus is cool) spaced about three-fourths
inch from the perforated end wall 22, as at 33, and the stack
support angle members 29 rest slidably on the top 14, 25 of the
shell. The gap at 33 closes as the apparatus heats up. The stack
thus gradually moves toward the left with the heated perforated
liner, and this is permitted by the initial expansion gap 33. The
opposite end of the liner remains somewhat loosely anchored in
position, by constructions hereinafter described.
The liner 18 is provided on all sides with Z-supports 40 which
slidably engage tracks or runners 41 inside the exterior shell 10,
which is intended to heat only to a moderate temperature, such as
150.degree. F. In order to minimize heat transfer from the hot
running liner to the exterior shell, the tracks 41 at the bottom,
as well as similar tracks on the sides and top, are in the form of
narrow longitudinally extending flanges, having minimized heat
transfer contact with the Z-shaped supports 40. The flanges 42 of
these Z-supports 40 are welded to the perforated side, bottom and
top walls of the liner, and the opposite flanges 43 thereof thus
engage and can slide or shift along longitudinal support tracks 41
in the shell. The webs 44 of the supports 40 are at an angle of
approximately 60.degree. to the liner walls and tracks, and
accordingly can bend to accommodate lateral thermal expansion of
the heated liner. In the particular embodiment shown, the bottom of
the shell is so fabricated as to afford a pair of the longitudinal
tracks 41, engaged by a plurality, here five in number, of the
Z-supports 40.
Each side wall of the shell is equipped with one longitudinally
extending angle iron guide or track 41, one flange of which is
engaged by three of the Z-shaped suppports on the side of the
perforated liner. And finally, the underside of the shell is
equipped with two longitudinal angle irons 50, whose depending
flanges 41 serve as the tracks or guides engages by four of the
Z-shaped supports 40 mounted on the top of the liner.
In the spaces between the shell and the perforated walls of the
liner are placed packings 54 of high heat resistant mineral wool,
capable of withstanding a temperature of 1,500.degree. -
1,600.degree. F., and chosen for its high noise absorption
characteristics. A layer of fiber glass cloth is used between the
perforated wall and mineral wool to guard the latter against
disruption by the high velocity gases flowing through the liner.
The glass cloth is flexible, and therefore acoustically "invisible"
to the sound waves in the gases. These waves accordingly are
transmitted through the perforations and the glass cloth to the
fibrous sound insulation material 54.
The aforementioned gas intake fitting 11 comprises a
frusto-conical, upwardly divergent member 55, with a flange 56 at
its lower end for attachment to the flange 57 of the combustion gas
discharge outlet of the gas turbine. The inlet member 55 projects
downwardly somewhat between the bottom of the suppressor shell 10.
A frusto-conical wall 58, at a greater inclination than that of the
member 55, extends from the lower end of member 55 to the level of
the bottom of the shell, being closely received in an opening in
the bottom wall of the shell, and being welded to the shell at the
junction, as at 59. A vertical cylindrical wall 60 rises from the
junction, where it is welded to the top edge of the wall 58, and
extends upwardly to and just through an opening 64 in the bottom
wall of the perforated liner 18. A ring plate 66 is welded inside
the top end of wall 60, and extends radially inward substantially
to the member 58. The space defined between the members 55, 58, 60
and 66 is packed with high heat resistant sound insulation or
absorbent material, preferably a mineral wool material capable of
withstanding the high heat of the turbine discharge gases. A
packing 67 of fiber glass cloth is placed between the perforated
member 58 and the packing 67.
The top of the frusto-conical member 55 has a cover plate 66,
spaced just below the top wall of the liner.
The hot turbine gases rise through the perforated frusto-conical
member 58, and pass through the perforations therein into the space
inside the perforated liner 18 for travel along the latter and
eventual discharge up the stack. The divergence of the
frusto-conical member expands the intaken gases, and so affords a
diffuser action which importantly reduces the back pressure on the
turbine during running.
Spaced outside the rearward half of the frusto-conical diffuser 55
is a half-cylindric perforated wall 72, which acts as a deflector
for gases escaping through the perforations in the rearward half of
the diffuser 55. Thus, such gases impinge on the deflector wall,
and are deflected thereby in a uniform flow pattern around the
sides of the diffuser wall, to join with the gases emerging through
the perforations in the front half of the diffuser for relatively
uniform non-turbulent flow downstream of the liner.
In accordance with the invention, the gas flow space down the liner
has a large perimeter for its cross-sectional area, because of its
flat cross-section, and there is therefore a relatively large area
of sound absorber treatment provided by the mineral wool packing in
back of the perforated liner walls, in relation to the gas flow
along the liner. It is desirable to further increase this area of
sound absorber treatment, and to this end the liner, in the
illustrative embodiment, is subdivided into two upper and lower
flow channels by longitudinally running additional sound absorbers
78, constructed in this case in the unique form of a medially
positioned longitudinal panel 79, with two absorbers 78 unified in
a back to back position, and together making up a sound absorber
assembly 80 with two opposed sound absorber sides.
In detailed make up, the assembly 80 comprises parallel upper and
lower perforated sheet metal walls 82, whose longitudinal edges are
received in channels 83 secured to the side walls of the liner 18.
At the front and rear ends, these walls converge on a gradual angle
to a solid mid-plate or septum 84, which is parallel to the two
outside plates or walls 82 and is midway therebetween. The septum
84 is fastened to the flanges at the ends of the convergent
portions of the walls 82, and the assembly fastened properly
together. Thus, the end portions of the absorber are of a
streamlined contour, and avoid turbulence where the gas stream
divides and recombines. It is, of course, evident that the gas flow
should be as non-turbulent as possible, not only in reducing back
pressure on the turbine, but in gaining maximized uniformity of gas
impingement throughout the perforated regions of the liner where
the sound absorber fibrous material is accessible.
High heat resistant mineral wool is packed in between each of the
perforated walls 82 and the septum 84, as indicated at 90, and
fiber glass cloth is placed between this sound absorbent material
90 and the perforated walls 82.
A preferred feature of the invention is a curved shield 94 used in
the gas discharge outlet, close to the angle between the stack and
the top of the shell. A deflector 95 mounted in the stack over this
shield 94 shields it from falling snow, leaving open, in all
weather, a throat 96 through which the turbine can exhaust to
atmosphere. In the event that the stack and the liner cavity
therebelow become choked with snow, the back pressure on the
turbine becomes so great that the turbine cannot be started. The
shield 94 and throat 96 thus constitute an important feature of the
invention.
Used with a gas turbine driving a 750 Watt electric generator, and
with a shell of 24' in overall length, with other dimensions in
proportion, the performance of the noise suppressor of the
invention is in accordance with the chart shown in the drawings.
Curve A shows the sound intensity of the turbine discharge, without
a suppressor, in Decibels (dynes per square centimeter), at a
distance of 50 feet, curve B shows the noise level on a typical
quiet city street, and curve C shows the sound intensity level at
50 feet from the stack of the suppressor of the invention. The very
marked attenuation should be noted, as well as the fact that the
noise level at 50' is, with the attenuater, is less than that on a
quiet city street.
In operation, the liner structure attains a running temperature of
the order of 1,100.degree. F., while the exterior shell remains at
about 150.degree. F. The liner expands thermally both transversely
and longitudinally. The angular webs of the Z-supports allow
bending of the supports to accommodate to the transverse expansion.
The liner is somewhat loosely anchored at one end to the shell at
and by the perforated frusto-conical diffuser shell. As the
temperature rises, the longitudinal thermal expansion is
accommodated by shifting of the Z-supports along the longitudinal
tracks 41 in the shell. The low running temperature of the shell is
owing to the minimized heat conduction path from the liner walls to
the shell, which is substantially limited to the U-shaped supports
on the liner and the narrow support flanges 41 on the shell.
The favorable aerodynamic flow characteristics provided by the
invention minimize back pressure on the turbine, and at the same
time minimize noise attenuation. The frusto-conical intake diffuser
for example reduces back pressure by expansion of the intaken
exhaust gases. These gases are at the same time distributed
uniformly through the walls of the diffuser into the gas passage in
the liner. The deflector gathers the gases thus emitted into the
liner from the diffuser around the back or far side of the diffuser
and directs these to the longitudinal liner passage leading to the
stack.
FIG. 5 shows in transverse section a more economical construction
within the scope of the invention wherein the shell 100, perforated
liner 102, and interior sound absorber 104 are circular and
concentric. This modification in geometric configuration will be
understood withour further description.
The invention has been disclosed by way of drawings showing, and a
specification describing, a certain present illustrative
construction. It will, of course, be understood that various
changes in design, structure and arrangement may be made without
departing from the spirit and scope of the invention as defined by
the appended claims.
* * * * *