Note: Descriptions are shown in the official language in which they were submitted.
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CA 02552091 2003-O1-27
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OUTLET SILENCER STRUCTURES FOR TURBINE
BACKGROUND OF THE INVENTION
This is a division of Canadian patent application No. 2,417,479 filed
January 27, 2003.
This invention relates to air duct outlet silencers, and in particular to
silencers designed for use with gas turbines and other noise-creating, gas
flow-
producing devices.
Stationary gas turbines for the production of power are well known for use
io by power producing industries. One difficulty that is encountered with the
use of
gas turbines is the noise that they can create during their operation. Because
of
this noise, efforts have been made in the past to provide sound attenuators or
sound reducing devices both at the intake of the gas turbine and at the outlet
end.
However for various reasons problems have been encountered in developing
Is satisfactory inlet silencing units and outlet silencing devices for these
gas turbines.
One reason for these difficulties is that the flow into and out of stationary
gas
turbines is often compromised because of spacial constraints and cost factors.
Many such systems feature a short plenum box with a vertical inflow into the
compressor of the turbine and an axial outflow. In the usual case, inlet
silencers
2o are installed ahead of the plenum while the gas turbine outlet is often
dumped into
a plenum which feeds a vertical exhaust section consisting of some form of
silencer and exhaust stack.
Outside of the field of gas turbines, both air duct inlet silencers and air
duct
outlet silencers have been developed in recent years for use in combination
with
Zs axial fans providing air to large structures such as office buildings and
industrial
buildings. For example U.S. patent No. 5,587,563 issued December 24, 1996 to
Dipti K.R. Datta describes both an air inlet silencer for an axial fan and an
air
outlet silencer, both of which employ sound attenuating material located
behind
perforated sheet metal walls. The duct inlet silencer includes an exterior
housing
3o that has two principal air inlets located on opposite sides of the housing.
The unit
also has a single air outlet located at one end of the housing. The two inlets
and
the outlet are connected by airflow passageways defined by interior walls and
these passageways bend 90 degrees from the inlets to the outlet. Sections of
the
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interior walls are made from the aforementioned pertorated sheet metal. In one
preferred embodiment the passageway from each inlet is divided into four
quadrants with upper and lower quadrants separated by a horizontal divider.
With respect to the fan outlet silencer described in the aforementioned U.S.
patent, it has a top, bottom, and sidewalls and between these walls extend
first
and second series of splitters with the splitters of each series being spaced
apart
to form smaller air passageways. The splitters of each series are mounted side
by
side in a row and the splitters of one series are staggered with respect to
the
splitters of the other series in a direction transverse to the direction of
airflow. The
io sound attenuating material that is used in both the inlet silencer and the
outlet
silencer for an axial fan as described in this U.S. patent is standard sound
attenuating material such as fibreglass bats stuffed between the interior
walls and
the exterior walls and into the interior of the splitters.
Up to the present time, there has been no suggestion that inlet and outlet
is silencers of this general type could be used in combination with relatively
large,
stationary gas turbines. One difficulty with the known outlet silencers
designed for
use with ordinary axial fans is that they are not able to withstand the high
temperatures that exist in the hot air stream emitted by the gas turbine nor
are
they able to withstand the much higher air velocities which can be as much as
Zo 15000 feet/minute and higher.
In the air handling art wherein systems have been developed for providing
fresh air and return air to structures using suitable fans, it is known that
turning
vanes to redirect the direction of the airflow into or out of a fan unit can
provide
excellent turning performance including uniform airflow with minimum pressure
2s loss. The use of such turning vanes in combination with sound attenuating
material has proven to be effective in air supplying and air conditioning
applications involving the use of axial fan units. Most of these systems
employ
conventional acoustic dissipative media such as fibreglass. In many of these
recently developed systems the sound absorbing surface comprises a special
3o sandwich construction consisting of a perforated cover sheet, an erosion
resistant
duct-liner and bulk fibre located behind the duct liner and packed to the
proper
density. However as far as applicant is aware, this sound attenuating
technology
has in general not been used with nor proposed for use with gas turbines such
as
CA 02552091 2003-O1-27
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large, stationary gas turbines used for the production of power.
The present invention provides a novel sound attenuating duct unit suitable
for connection to the outlet of a stationary gas turbine or other noise-
creating, gas
flow-producing device, this unit being capable of manufacture at a reasonable
cost
while having substantial sound attenuating capabilities.
According to one aspect of the invention, a sound attenuating duct unit
suitable for connecting to an outlet of a stationary gas turbine includes a
housing
having a horizontal housing section and a vertical housing section and having
sidewalls surrounding a main airflow passageway that extends along a bend. An
io air inlet is located at one end of the horizontal housing section and is
adapted for
connection to the outlet of the gas turbine. At least one air outlet is
located at least
proximate to an upper end of the vertical housing section. At least two
splitters are
mounted in the housing. The splitters divide sections of the main airflow
passageway into smaller air passageways. At least one of the at least two
splitters
is is positioned downstream in the main airflow passageway relative to at
least
another of the at least two splitters. The at least two splitters contain
sound
attenuating material selected from a group comprising ceramic fibers and
mineral
wool and capable of withstanding airflow temperatures in the main airflow
passageway of at least 500~degrees Celsius. At least a portion of both the
Zo sidewalls surrounding the main airflow passageway and metal sidewalls
forming
the splitters are made of perforated sheet metal having a thickness of at
least 12
gauge.
In one embodiment of this outlet silencer for a turbine, the perforated sheet
metal is made of stainless steel.
is According to another aspect of the invention, there is provided a
combination of a gas turbine intended for installation and use at a selected
stationary site and a sound attenuating duct unit connected to a hot air
exhaust
outlet of the gas turbine. The duct unit includes a housing having a
horizontal
housing section and a vertical housing section and having sidewalls
surrounding a
3o main airflow passageway that extends along a bend. There is an air inlet
located
at one end of the horizontal housing section and connected to the exhaust
outlet
of the gas turbine. At least one air outlet is located at least proximate to
an upper
end of the vertical housing section. The combination also includes at least
two
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splitters mounted in the housing. The splitters divide sections of the main
airflow
passageway into smaller air passageways. At least one of the at least two
splitters
is positioned downstream in the main airflow passageway relative to at least
another of the at least two splitters. The splitters contain sound attenuating
s material selected from a group of materials comprising mineral wool and
ceramic
fibers and capable of withstanding airflow temperatures in the main airflow
passageway of at least 500 degrees Celsius. A layer of stainless steel screen
is
arranged over the sound attenuating material so as to prevent the escape of
the
sound attenuating material into the main airflow passageway. Also at least a
io portion of both the sidewalls surrounding the main airflow passageway and
metal
sidewalls forming the splitters are made of perforated sheet metal. The screen
is
arranged behind the perforated sheet metal of the splitters.
In a preferred embodiment of this combination each splitter includes a
rounded nose portion, and this nose portion is made of imperforate stainless
steel.
is According to yet another embodiment of the invention, a sound attenuating
duct unit suitable for connection to an outlet for hot emission gases produced
by a
power plant includes a metal housing formed with sidewalls containing sound
attenuating material capable of withstanding high airflow temperatures and
forming a main airflow passageway for the hot emission gases. The housing has
a
2o gas inlet at one end of the housing and at least one air outlet at an
opposite end of
the housing. The airflow passageway extends between the gas inlet and the at
least one gas outlet. The side walls of the housing include exterior wall
panels and
pertorated interior wall panels spaced-apart from and supported by the
exterior
wall panels. The sound attenuating material is sandwiched between the exterior
zs wall panels and the interior panels. At least one elongate sound
attenuating splitter
is mounted in the main airflow passageway, extends between and is supported by
two of the sidewaAs located on opposite sides of the housing, and is supported
therein by the side walls of the housing. This splitter divides the main
airflow
passageway into smaller airflow passageways. The or each splitter contains
sound
3o attenuating material and has an exterior constructed with perforated sheet
metal.
Splitter mounting devices connect opposite sides of the at least one splitter
directly
to the exterior wall panels of the two side walls so as to allow thermal
expansion
of the at least one splitter when the duct unit is heated up by the hot
emission
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CA 02552091 2003-O1-27
-5-
gases during operation of the power plant.
In the preferred embodiment, each splatter mounting device comprises a
bracket rigidly attached to its respective exterior wall of the housing and
having an
inwardly projecting tongue. The or each splatter has side edge plates provided
with
elongate openings receiving the tongues of the respective brackets for the
splatter.
Each tongue is movable relative to its respective elongate opening upon
thermal
expansion of the adjacent attached splatter.
According to a further embodiment of the invention, a sound attenuating
duct unit suitable for connecting to an outlet of a noise creating, gas-flow
io producing device includes a housing having a horizontal housing section and
a
vertical housing section and having sound attenuating side walls surrounding a
main airflow passageway that extends along a bend extending between the two
housing sections. A gas inlet is located at one end of the horizontal housing
section and is adapted for connection to the outlet of the gas flow producing
is device. At least one gas outlet is located at least proximate to an upper
end of the
vertical housing section. At least one initial, sound attenuating splatter is
mounted
in the housing and has an upstream end in the region of the gas inlet. This at
least
one splatter extends lengthwise around the bend. A plurality of spaced-apart,
sound attenuating, downstream splatters divide the main air flow passageway
into
2o smaller airflow passageways and are arranged side-by-side one another. The
downstream splatters are located downstream in the direction of gas flow from
the
at least one initial splatter and have major lower portions extending in
substantially
parallel planes that are substantially perpendicular to a central widthwise-
extending plane defined by an upper end portion of the at least one initial
sound
as attenuating splatter.
In one preferred embodiment, there is only one initial sound attenuating
splatter which is arranged substantially centrally in the main airflow
passageway
and there are three of the downstream splatters. Each of these splatters
contain
sound attenuating material capable of withstanding gas flow temperatures of at
30 least 500 degrees Celsius.
Further features and advantages will become apparent from the following
detailed description of preferred embodiments taken in conjunction with the
accompanying drawings.
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CA 02552091 2003-O1-27
-6-
In the drawings,
Figure 1 is a schematic illustration of a gas turbine power installation
equipped with an air duct inlet silencing apparatus and an air duct outlet
silencer
with both the inlet silencer and the outlet silencer shown in cross section
for
purposes of illustration;
Figure 2 is a perspective view in cross section showing an embodiment of
air duct inlet silencer with the cross section of the inlet silencer itself
being taken in
a vertical plane;
Figure 3 is a cross-sectional elevation of the air duct inlet silencer, this
view
io being taken along the vertical central axis of the inlet silencer;
Figure 4 is a plan view of the inlet silencer of Figure 3, this view showing
the six sides of one embodiment;
Figure 5 is a perspective cross-sectional view of a first embodiment of an
air duct outlet silencer construction in accordance with the invention, this
view
is being taken in a vertical plane extending through the horizontal central
axis of the
inlet portion of the silencer;
Figure 6 is a transverse cross-section of an elongate splitter used in the
outlet silencer of Figure 5;
Figure 7 is a cross-sectional elevation taken along the line Vll - VII of
Figure
20 8 illustrating an air duct silencing apparatus having air inlets on two
opposite sides
thereof;
Figure 8 is a horizontal cross-section of the same air duct silencing
apparatus taken along the line VIII - VIII of Figure 7;
Figure 9 is a cross-sectional elevation taken along the line IX - IX of Figure
2s 10 illustrating another embodiment of an air duct silencing apparatus
having air
inlets opening on one side only of the apparatus;
Figure 10 is a horizontal cross-section of the apparatus of Figure 9 taken
along the line of X - X of Figure 9;
Figure 11 is a first elevation view of a second embodiment of an air duct
30 outlet silencer construction in accordance with the invention;
Figure 12 is a second elevational view of the air duct outlet silencer
construction of Figure 11, this view being taken from the inlet side;
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CA 02552091 2003-O1-27
-7-
Figure 13 is a plan view of the elbow silencer section of the air duct outlet
silencer of Figure 11;
Figure 14 is a side elevation of the elbow silencer section shown in Figure
13;
s Figure 15 is a perspective detail view of wall structure used in the outlet
silencer of Figure 11;
Figure 16 is a schematic illustration in elevation showing how the pertorated
interior wall panels are mounted in the elbow silencer section;
Figure 17 is a detail view in cross-section showing a portion of the wall
io structure used in the outlet silencer of Figure 11 and in a transition
region between
sections.
Figure 18 is a perspective view of the metal shell for an elbow splitter used
in the outlet silencer of Figure 11;
Figure 19 is an exploded view of a stack splitter (without its sound
is attenuating material) and its mounting used in the outlet silencer of
Figure 11; and
Figure 20 is a cross-sectional elevation showing a bracket mounting
arrangement used to mount each of the splitters.
Figure 1 is a schematic illustration of a power generating installation 10
wherein power is generated by a stationary gas turbine indicated generally at
12.
2o This gas turbine extends horizontally as illustrated and it has an inlet or
intake
section at 14 and an outlet located at 16 at the opposite end of the turbine.
Connected to the intake of the turbine is a preferred form of air duct inlet
silencing
apparatus 18. It will be understood that substantial quantities of air can be
drawn
into the intake of the turbine via airflow passageways formed in the inlet
silencer
Zs 18. Hot air or gas exiting from the turbine through the outlet 16 passes
through a
sound attenuating structure,or duct unit indicated generally at 20. It will be
understood that a major function of both the inlet silencer 18 and the outlet
duct
unit 20 is to reduce the amount of noise emanating from the gas turbine so
that
the noise level surrounding this installation is reduced to an acceptable
level both
so for personnel working at the installation and others, such as people living
or
working close to the facility. Although the illustrated inlet and outlet duct
silencers
. are shown in combination with a gas turbine, it will be appreciated that
silencers
constructed in accordance with one or more aspects of the invention can also
be
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CA 02552091 2003-O1-27
_8_
used with other noise-creating, gasflow-producing devices, for example, large
air
handling fans, including axial fans.
Some of the other features shown in Figure 1 in whole or in part include a
building 22 which houses and protects the gas turbine and which can, for
s example, shelter equipment and personnel used to maintain and operate the
installation. Also shown is a platform 24 which extends around the inlet
silencer 18
and which provides access for operating personnel to the inlet components such
as filter and heat exchanging coils. Access to the platform 24 can be gained
by
means of a stairways 26. One version of the platform and stairways can be seen
io in Figure 2. For safety reasons, a guide rail or fence 28 can extend around
the
outer edge of the platform.
With respect to the outlet silencer, a suitable supporting framework 30 can
be provided below and around the outlet silencer in order to support same.
Turning now to the construction of the inlet silencer 18, as will be apparent
is from the foregoing, this silencing apparatus is designed for use with the
stationary
gas turbine 12 and the illustrated silencer can either be mounted outdoors
where it
will be exposed to the elements or it can be installed within a suitable
building or
structure. The silencing apparatus 18 includes a vertically extending duct
structure
34 having an upper duct section 36 with a plurality of vertically extending
sides
2o and a top cover or roof 40 which can comprise a horizontally extending
panel such
as a sheet metal panel. As indicated by Figure 4 in one particularly preferred
embodiment of the inlet silencer there are in fact six vertically extending
sides 41
to 46, these sides preferably being of equal width and height and extending
about
a central vertical axis located at A. It is also possible to construct the
inlet silencer
is with sides of unequal width, if required by the particular installation or
job site. It
will be appreciated that the number of sides can be less than six, for example
four
sides or five sides and the actual number of sides in the structure can depend
in
some extent on the installation's requirement, the amount of space available,
and
from which side the incoming air will be entering during use of the apparatus.
It will
3o be understood that there are air inlet openings 48 formed in some or all of
the
vertically extending sides 41 to 46 and these openings can cover substantially
all
of their respective vertical sides. Assuming that there are no obstructions or
adjacent structures that prevent air from entering the inlet silencer on all
sides,
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CA 02552091 2003-O1-27
_g_
there can normally be inlet openings 48 on all of the vertically extending
sides of
the structure. However there may for example be a blocking wall or other
obstruction on one or more sides of the inlet silencer that prevent air from
entering
from these particular sides and, in such cases, there may be air inlet
openings in
s only one, two or more but not all of the vertically extending sides.
Described
hereinafter are versions of the invention wherein there are inlet openings in
only
one side and also wherein there are inlet openings in only two sides.
An air outlet 51 is formed at a bottom end of the duct structure and this air
outlet is adapted for connection to an air intake plenum 52 of the gas
turbine. In
io the illustrated preferred embodiment, the air outlet 50 from the plenum 52
is
located in a vertical plane and it has a shape, for example circular,
conforming to
the shape of the intake 14. The air outlet 50 can be formed on one vertical
side of
the air intake plenum 52 having a pair of substantially vertical sidewalls 54,
an
open top, and an end wall 55 and a bottom which meet at a corner 56 which can
is be spuare as shown or can.be rounded. If the corner at 56 is rounded, this
helps
to smoothly redirect the incoming airflow from vertically downwardly to the
horizontal direction. If desired, suitable turning vanes (not shown) can be
arranged
in the corner section 52 to assist in redirecting the airtlow to the
horizontal
direction.
2o The inlet silencer 18 also includes an elongate, centrally located airflow
defining member 60 which is substantially cylindrical or multi-sided for a
major
portion of its length and which extends downwardly from the top cover 40 and
past
the air inlet openings 48. As used in this specification, in describing the
member
60 and its shape, the term "cylindrical" includes a multi-sided exterior that
is
2s elongate and similar to a cylindrical shape in its transverse cross-
section. This
airflow defining member is formed with a perforated sheet metal exterior
indicated
at 62 and the airflow defining member contains sound attenuating material 64.
The
extent of the perforated sheet metal in a preferred embodiment of the member
60
can be seen from Figure 3. As indicated in this figure, preferably the sheet
metal
3o extends over substantially the entire height of the airflow defining member
including the outwardly curved section 66 but not including the top cover 40
which
is not in contact with the incoming airflow. The perforated sheet metal can
extend
substantially to the pointed bottom end 68 of the member 60. Also shown in
Figure
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CA 02552091 2003-O1-27
-10-
3 is a tapered bottom section 70 that extends downwardly to the bottom end 60
from the central cylindrical section 72. It is also possible to construct the
central
airflow defining member 60 without the tapered bottom section 70. As shown in
the drawings, above the central section 72 is a substantially frusto-conical
upper
s portion 74 wherein, in vertical, transverse cross section as shown in Figure
3, the
exterior sheet metal wall is concavely curved. This frusto-conical upper
portion
extends downwardly from the top cover 40 to the cylindrical section 72. This
frusto-conical upper portion 74 can either be round in horizontal cross-
section or it
can be multi-sided. This upper portion can also be described as sloping
io downwardly and inwardly.
The version of the inlet silencer 18 of Figures 1 to 3 includes iwo or more
annular airflow passageways extending from the air inlet openings 48 towards
the
air outlet of the silencer with each passageway being defined by at least one
interior wall mounted in the duct structure. As shown in Figures 1 to 3, these
is airflow passageways each bend substantially so that a bottom section
thereof
extends substantially vertically. In the illustrated preferred embodiment
there are
three of these annular passageways 76, 78 and 80. With respect to the
passageway 76, it is defined by the sheet metal exterior 62 of the airflow
defining
member 60 on one side and by the interior wall 82 on the opposite or outer
side.
Zo With respect to the airflow passageway 78, this passageway is defined by
the
interior wall 82 on one side, that is the upper or inner side, and by an
interior wall
84 on the opposite or outer side. With respect to the bottommost annular
passageway 80, it is defined by the interior wall 84 and an annular wall
structure
86. It will be noted that Figures 2 and 3 show different versions of the
interior walls
zs 82,84 and of the annular wall structure 86. In the version of Figure 2, the
two
interior walls 82,84 are of substantially uniform thickness and their
thickness
corresponds to the thickness of annular wall structure 86'. This uniform
thickness
is due to the fact that both ipner and outer surtaces of the curved section of
each
of these interior walls and the wall structure 86' have the same center of
curvature.
3o However in the embodiment of Figures 1 and 3, the interior walls 82,84 vary
in their thickness with each-having a relatively thick upper section at 90 and
92
and a relatively thin, cylindrical or multi-sided lower portion indicated at
94 and 96.
Each of the upper sections~90,92 commences at a point and then the two sides
of
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CA 02552091 2003-O1-27
-11-
the wall section diverge to the widest point of the wall section before again
converging to the cylindrical or multi-sided section 94 or 96. It will thus be
seen
that the radius of curvature on one side of the upper section 90 or 92 is
smaller
than on the opposite or bottom side. It will be appreciated that this
arrangement
s provides for the use of a maximum amount of sound attenuating material in
the
upper region of the inlet silencer resulting in excellent sound attenuating
ability.
The annular wall structure 86 shown in Figure 3 has an inwardly sloping
exterior
surface at 100 which is made of impertorate sheet metal white the interior
surtace
of this structure has a curved upper portion 102 which leads smoothly to a
io cylindrical or multi-sided lower portion 104. Both of these portions of the
interior
surface are preferably constructed from perforated sheet metal. The annular
wall
structure 86 can alternatively be constructed in the manner shown in Figure 1
wherein the exterior of the lower portion is cylindrical.
Also it will be seen from Figures 2 and 3 that the bottom end of the interior
is walls 82,84 can terminate at different heights and at a height above the
bottom
end 68 of the airflow defining member 60. In particular the bottom end 106 of
the
innermost interior wall 82 can be above the bottom end 108 of the interior
wall 84.
Both of these bottom ends are substantially above the bottom end 68. Also in
the
version of Figure 3, the conical bottom section 70 of the airflow defining
member
ao 60 extends into a transition duct section 110 which, in the illustrated
version
tapers inwardly in the downwards direction and connects to a rectangular duct
section 112. it is also possible to construct the transition duct section 110
so that it
does not have a tapered exterior. In the duct section 110, the horizontal
cross-
section of the airtlow passageway is changed in a manner known ep r se from
is circular or multi-sided (at the top) to rectangular.
It will be further understood that each of the interior walls 82,84 is filled
with
sound attenuating material indicated at 115. This material can comprise
compressed bats of fibreglass or mineral wool, for example. Also the annular
wall
structure at 86 is filled with sound attenuating material 115. It will also be
3o understood that the central and lower sections of the member 60 and the
interior
walls 82,84 are rigidly supported by suitable supporting frames or struts (not
shown) that are connected.thereto and that do not materially interfere with
the
incoming airflows. These narrow struts can be connected at their outer ends to
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CA 02552091 2003-O1-27
-12-
walls located radially outwardly from the member 60 or the interior wall.
The thick upper sections 90,92 of the two interior walls are connected to
corresponding upper sections on the adjacent sides of the silencer and thus
together they form multi-sided upper sections of the interior walls. This can
be
seen more clearly from Figure 4. The upper sections can also be substantially
conical as illustrated in Figure 2 where the upper sections of the interior
walls have
a substantially uniform thickness.
Also as illustrated in Figures 1 and 2, it will be seen that the air duct
inlet
structure includes the aforementioned air intake plenum 52 which is a form of
duct
io elbow that, in the illustrated embodiment, bends approximately 90 degrees.
Returning to the gas turbine that is connected to the outlet of the air inlet
silencer 18, it will be seen from Figure 1 that this turbine is elongate and
it will be
appreciated that it has a central longitudinal axis indicated by the dash line
A1 in
Figure 1 about which the blades of the gas turbine rotate during use thereof.
Thus
is in the power generating installation illustrated in Figure 1, the central
longitudinal
axis A1 of the gas turbine is substantially horizontal and is substantially
perpendicular to the central longitudinal axis A of the airflow defining
member 60.
If desired, an optional feature of the intake 14 for the turbine is a central,
sound attenuating bullet 120 which can have a cylindrical exterior and which
can
2o be filled with sound attenuating material and covered with perforated sheet
metal.
Suitable, radially extending struts (not shown), that do not interfere with
the
airflow, can be used to mount this central bullet which also helps to reduce
the
amount of sound being emitted from the intake end of the turbine.
If the inlet silencer 18 is to be mounted in the open, which would generally
2s be the case because of its size, the upper section thereof is constructed
so as to
provide some protection from the elements including rain and snow. Shown in
the
drawings are a series of weather hoods 122 which can be arranged over the
inlet
openings 48. Thus if inlet openings are arranged on all sides of the inlet
silencer,
these hoods are mounted on all of the sides. Each hood can have a steeply
3o sloping panel 124 and arranged at each end of this panel are vertically
extending
end walls 126 that connect the ends of the panel 124 to supporting framework
125
(see Figure 2) for the upper section of the inlet silencer. Preferably there
is a
narrow corridor 130 arranged just inside the hoods, this corridor allowing
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CA 02552091 2003-O1-27
-13-
maintenance personnel to gain access to the filters of the inlet silencer.
Covering
the inner wall of this corridor in a preferred embodiment is a prefilter 132
which
can be relatively thin. If desired or if required by the particular
installation, a
plurality of so called final filters 134 can be stacked one on top of the
other
s adjacent the prefiiter 132. It will be understood that these filters, if
used can extend
the entire width and height of the inlet openings 48. Immediately downstream
of
the filters, there can be arranged a heat exchanger such as an evaporative
cooler
135 and there can be several of these cooler units arranged one above the
other
to cover the entire height of the inlet openings. Preferably, just downstream
of the
io cooler are several drift eliminators 136 which can be generally of standard
construction and which help prevent any moisture from entering the airflow
passageways 76, 78, and 80.
An additional preferred feature shown in Figure 4 is the use of one of or a
plurality of access doors 14p. As illustrated, there is one such door for each
comer
is where two sides of the inlet silencer meet. These doors provide access to
the
aforementioned corridor 130.
As shown in Figure 4, the internal walls 82, 84 as seen in horizontal cross
section are not circular but rather are mufti-sided. In the case of the
preferred
embodiment shown in Figure 4, these internal walls are six sided. Because of
this,
Zo these internal walls and alsb the wall structure 86 which is also mufti-
sided are
relatively easy to build as the curved, perforated metal panels used to make
these
walls need only be curved in one direction. It also becomes relatively easy to
weld
adjacent panel sections together to form a complete internal wall 82 or 84 or
the
lower wall structure 86.
as In one preferred embodiment of the inlet silencer 18 as illustrated in
Figure
3, the width of the corridor 130 is about 2 feet and generally the width
should be
as narrow as possible. The thickness of the preferred pre-filter is 2" and can
range
up to 4" while the final filter.can have a thickness of about 12". Although
not
illustrated, the inlet silencer can be fitted with a standard drain pan
located just
3o downstream of the cooler coils 135 to permit condensation from the coils
and from
the drift eliminators to drain out. A detailed description of this drain pan
herein is
deemed unnecessary as such draining pans are well known in the heat
exchanging art.
._.~..~_".,...~,_"..,_...,.,~",...d.,...a._.~..~.
CA 02552091 2003-O1-27
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Reference will now be made to Figures 1 and 5 which illustrate a first
embodiment of a sound attenuating structure 20 suitable for the outlet of the
gas
turbine. As indicated, it is also possible to use an outlet duct silencer
constructed
in accordance with one or more aspects of this invention in combination with a
s power plant unit other than 'a gas turbine or in combination with a noise-
creating,
gas flow-producing device such as a fan, for example, a large axial fan. With
particular reference to Figure 5, the outlet silencer, which is shown along a
vertical
cross section, has a housing 150 that includes a horizontal housing section
152
and a vertical housing section 154. This housing can have flat, exterior
sidewalls
io as shown in Figure 5 including horizontal bottom wall 156, a shorter
horizontal wall
158 and vertical sidewaus including walls 160,162 and 164. It will be
appreciated
that there is another sidewall (not shown) that extends vertically and that is
located
opposite the sidewall 164. These sidewalls surround a main airflow passageway
166 that extends along a substantial bend, such as the illustrated 90 degree
bend
~s at 168. There is an air inlet 170 located at one end of the horizontal
housing
section and adapted for connection to the outlet of the gas turbine 12 or
other
gasflow-producing device. There is also an air outlet 172 located at upper end
of
the vertical housing section.
Located within the main airflow passageway 166 are at least a first or initial
Zo series 176 and a second series 178 of splitters with the splitters of each
series
being spaced apart to form smaller air passageways 180,182 and being mounted
side-by-side in a row. The second series 178 is positioned downstream relative
to
the direction of airflow or gasflow in the main airflow passageway 166
relative to
the first series 176 and is staggered relative to the first series in a
direction
2s generally transverse to the direction of airtlow indicated by the arrow F
in Figures 1
and 5. As illustrated the second series of splitters has three, straight
elongate
splitters 185 while the first series has two curved, relatively large
splitters 186 and
an inside, smaller sputter or turning vane 188. It will be understood that
this duct
silencer can be made with fewer or more splitters in each of these series, if
3o desired or required. For example, there can be a single splitter 186 that
extends
around the 90 degree bend either with or without the turning vane 188 which
need
not contain sound attenuating material. As is known er se in the sound
attenuating art for air handling ducts, each of the larger splitters 185,186
contains
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CA 02552091 2003-O1-27
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sound attenuating material indicated at 190. However in order that the outlet
silencer 20 and the splitters mounted therein can withstand the high
temperatures
of the airflow exiting from the turbine, the sound attenuating material is not
made
from standard fibreglass bats, but is a material capable of withstanding these
high
airflow temperatures of at least 500 degrees Celsius or more. The preferred
sound
attenuating material for this purpose is ceramic fiber or mineral wool because
of
their reasonable cost. The exterior of the splitters is substantially formed
by
perforated sheet metal and is preferably stainless steel. Of course, if the
outlet
duct silencer will not be subject to high temperature gasflows, such as when
used
io downstream of an air handling fan, then standard fiberglass bats can be
used.
Shown in Figure 6 is one of the large splitters 185. Illustrated in this
figure is
the preferred feature of a layer of stainless steel screen 192 which is
arranged
directly behind the pertorated sheet metal, this screen helping to prevent the
escape of the sound attenuating material through the holes in the perforated
sheet
is metal. The preferred screen 192 is a very fine mesh SS screen having 200 to
240
strands per inch. The SS strands or threads have a diameter of only about
1/1000th inch. Instead of using this metal screen, it is also possible to
encapsulate
the sound attenuating material in woven fiber bags. Also shown is the semi-
cylindrical bottom end 194 of the splitter and preferably this bottom end is
covered
2o with imperforate sheet metal, again preferably stainless steel.
As shown both in Figures 1 and 5, the first series of splitters 176 extends
through a substantial bend, this bend normally corresponding to the bend in
the
main airflow passageway which, in the illustrated embodiment is a bend of 90
degrees. This substantial bend is in the direction extending from the leading
edge
2s of these splitters to the trailing edge thereof. It will be also noted that
in the
embodiment of Figure 5, both series of splitters extend transversely across
the
passageway from one side thereof to the opposite side and their opposite side
edges are connected to the walls of the outlet silencer.
Another feature that can be seen from Figure 5 is that the inner sides of the
3o aforementioned sidewalls of the outlet silencer are also made from
perforated
sheet metal panels including the panels indicated at 196, 198 and 200.
Arranged
between the interior panels and the exterior metal panels that form the
sidewalls
of the outlet silencer is further insulating sound attenuating material
indicated at
,.... .._.~,..~-~.""..""." ........,,~-.,..,.,Aw.,~".-.L-....
CA 02552091 2003-O1-27
-16-
202. Again, as was the case with the splitters, this material must be capable
of
withstanding airflow temperatures of at least 500 degrees Celsius and more and
the preferred sound attenuating material is ceramic fiber or mineral wool.
Also,
unlike previously known sound attenuating units used for reducing sound from
axial fans, if the duct unit is for use downstream of a gas turbine, the
perforated
metal itself must generally be made thicker in order to withstand the much
higher
temperatures in the airflow. In particular both the inner surfaces of the
sidewalls
forming the main airflow passageway and the perforated metal sidewalls forming
the splitters are made from perforated sheet metal having a thickness of at
least
io 12 gauge. With the use of this thicker sheet metal, the panels covering the
splitters and the interior surfaces of the sidewalls will have less tendency
to bend
and distort when their temperatures become elevated. Also all of the metal
components that are exposed to the hot air stream are constructed so as to
allow
for quick expansion when exposed to high temperature gradients within a few
is seconds of turbine start-up.
The horizontal housing section 152 includes a duct transition section
formed by interior wall panels including panels 210 and 212. This transition
section
extends approximately between the aforementioned air inlet 170 which is
circular
and approximately a transverse plane along the main airflow passageway
(located
Zo at P) where leading edges of the first series of splitters are positioned.
It will be
understood that the transverse cross section of the main airflow passageway in
this section changes gradually from circular to rectangular.
As shown in Figure 5, there is also a transition section adjacent the top of
the second series of splitters. In this transition section, the sidewalls
160,162 taper
as inwardly in the upwards direction. Each sidewall then becomes vertical
again at
218. It is also possible to taper the sidewall 164 inwardly at this transition
section
along with its opposite wall, if desired. It will be understood that the top
air outlet
172 can be connected to a suitable emission stack extending vertically
upwardly
therefrom.
3o Preferably the stainless steel sheet metal that is used to construct the
exterior of the splitters and the interior sidewalls has an open area of at
least 30%
of the total sheet area. Also, in Figures 1 and 5, the individual width of
most
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CA 02552091 2003-O1-27
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smaller air passageways 180,182 is about equal to the transverse width W (see
Figure 6) of an adjacent splitter.
With respect to the use of stainless steel in the outlet silencer, it will be
appreciated that use of this relatively expensive metal is normally only
required in
those regions of the outlet silencer that experience high temperatures i.e. in
excess of 500 degrees Celsius. In substantially cooler areas such as the
exterior
surtaces of the outlet silencer, imperforate, galvanized sheet metal can be
used.
In a one embodiment of the outlet silencer employing mineral wool, the
insulation is packed to a density of about 6 pounds per cubic foot in order to
obtain
io good sound attenuation characteristics.
It will be appreciated that the 12 gauge sheet metal that is used in an outlet
silencer for a gas turbine, which is close to 1/8" thick, is approximately
double the
thickness that has been used in the past with inlet and outlet silencers
designed
for axial fans. Such previously known outlet silencers commonly use 16
is gauge pertorated sheet metal, having a thickness of approximately 1116".
As indicated, mineral wool is a preferred sound attenuating material
because of its low cost and its ability to withstand high temperatures. Other
sound
attenuating materials which can be used for this purpose but which are more
expensive include ceramic fibers and silica fibers.
2o Figure 7 and 8 illustrate another embodiment of an air duct inlet silencing
apparatus. This silencing apparatus indicated generally at 220 also comprises
a
vertically extending duct structure that can be used to provide an airflow
into the
intake of a stationary turbine. It will be understood that this silencing
apparatus
220 can be mounted on top of an air intake plenum such as the plenum 52
2s illustrated in Figure 1 or Figure 2 of the drawings. It would take the
place of the air
duct silencing apparatus that is located above the plenum 52 in Figures 1 and
2.
The illustrated silencing apparatus 220 has four vertically extending sides
with two
of these sides indicated at 222 and 224 being completely enclosed and two of
the
sides being substantially open to allow airflow into the apparatus. The
apparatus
so 220 has a horizontal top cover 226 which can be formed of imperforate sheet
metal, such as galvanized steel. The illustrated apparatus has a rectangular
bottom 228 which can be suitably constructed for mounting on the
aforementioned
air inlet plenum 52 or for mounting on a transition duct (if required). There
.__._._~~..~._.......~". -...,...~......a..........~.,..
CA 02552091 2003-O1-27
-18-
preferably are a plurality of inlet openings located on two opposing sides
230, 232
of the apparatus. As illustrated, there are four openings 234 to 237 on each
of
these sides. As illustrated there are a number of slit-like air outlets 238
formed in
the bottom of the structure and, as indicated, these outlets are adapted for
s connection to an air intake of a gas turbine such as that illustrated in
Figure 1. It
will be appreciated by one skilled in the art that the vertically extending
sides of
the apparatus 220 can be extended downwardly from the bottom location shown in
Figure 7 and, if this is done, the apparatus 220 can effectively have a single
air
outlet formed in its bottom end as the internal, airflow splitting members,
described
to hereinafter, can be made so as to terminate above the bottom of the
apparatus
and above the single outlet.
The silencing apparatus 220 like the silencing apparatus of Figures 1 and 2
also has an elongate centrally located airflow defining member 240 which
extends downwardly from the top cover and pass the air inlet openings 234 to
237.
is The member 240 has its exterior formed with perforated sheet metal and it
contains sound attenuating material 242. However, unlike the central airflow
defining member of Figures 1 and 2, the member 240 has a lower section with
opposing, planar, vertical walls 244 and 246. These walls extend substantially
from one side of the apparatus to the opposite side as indicated in Figure 8.
These
2o pertorated, sheet metal walls can extend to vertical, interior walls 248
and 250
which can also be pertorated, if desired. Extending upwardly from these planar
wall sections are curved, upper wail sections 252 and 254, which, as
illustrated,
are cylindrical arcs. that extend upwardly through a bend of almost 90
degrees,
terminating at the top cover. If desired, there can also be short, inwardly
tapering
as wall sections 256 and 258 extending downwardly from the planar walls 244,
246.
The apparatus 220 is also formed with interior walls or splitters 260 to 262,
these interior walls being provided in pairs with a wall of each pair located
on a
respective side of the central airflow defining member 240. Although these
interior
walls vary in size as shown-in Figure 7, they are each of similar
construction.
3o Therefore it will suffice herein to describe one of the interior walls 262.
Each of
these interior walls 260 to 262 is filled with sound attenuating material 264.
The
lower section of each wall 262 has opposing, pertorated planar sheet metal
panels
indicated at 266 and 268. These planar wall sections-extend from the
w. __,r.,.,..._i, ,","~","._ ""~.".,",~."",...,,,:»...
CA 02552091 2003-O1-27
-19-
aforementioned interior wall 248 to the opposite interior wall 250. Located
above
these planar sections are curved upper sections 270 and 272 which can also be
made of perforated sheet metal. These curved upper sections terminate
approximately at the adjacent air inlet openings and, in the region of these
s openings, they converge to meet at a horizontally extending, leading edge
274. If
desired, the bottom of each of these interior walls can be formed with a semi-
cylindrical bottom piece 276 which, as illustrated, is located at the level of
the
aforementioned outlets 238. If desired, there can also be short interior
dividing
walls or splitters, two of which are indicated at 278 and these can be formed
with
io opposing planar sides and a rounded front at 280. The opposing planar sides
of
these walls can also be perforated and these short interior walls are also
filled with
sound attenuating material.
The silencing apparatus 220 is formed with two insulated outer wall
sections 285 and 286 which extend between the aforementioned interior walls
is 248, 250. The exterior surtace of these walls is made of impertorate sheet
metal
288 and it will be seen that these planar sheet metal panels can slope
inwardly at
a small acute angle to the vertical plane. The inner surface of these walls is
formed with pertorated sheet metal and each inner surface includes a planar
section 290 that extends upwardly from the bottom of the apparatus to a semi-
Zo cylindrical top section 292. Each inlet opening 234 is located between the
curved
upper section 292 and the lowermost interior wall 260 adjacent thereto.
Turning now to the further embodiment of an air duct silencing apparatus
which is illustrated in Figures 9 and 10, this silencing apparatus is
indicated
generally at 300 and will be understood that this apparatus is also for use at
an
2s inlet of a stationary gas turbine such as the turbine illustrated in Figure
1. It will be
further understood that the apparatus illustrated in Figures 9 and 10 can be
the
upper duct duct section of a vertically extending duct structure that
includes, for
example, an air inlet plenum such as the plenum 52 illustrated in Figures 1
and 2.
The upper duct section 300 as illustrated has four vertically extending sides
3o including three enclosed sides indicated at 302 to 304. The silencing
apparatus
300 further includes a top cdver 306 which can be rectangular and made of
imperforate galvanized sheet metal. In this duct structure are a plurality of
inlet
openings that are located on one of the vertically extending sides of the
structure.
CA 02552091 2003-O1-27
-20-
As illustrated, there are six of these openings identified by references 308
to 313
with the opening 308 being adjacent top cover 306 and the opening 313 being
the
lowermost opening. As shown in Figure 9, the size of these openings can vary
with
the bottommost openings 312, 313 in the illustrated embodiment being
s substantially smaller than the uppermost openings 308 to 311. Thus the side
301
of the silencing apparatus is an open side to a substantial extent. Also, the
apparatus illustrated in Figures 9 and 10 has a plurality of air outlets 314
formed at
the bottom end 316 thereof. However, it will be apparent to those skilled in
the art
that the exterior sidewalls of the apparatus 300 can readily be extended
to downwardly from the location shown and beyond the bottom of the curved
airtlow
splitters (described below) so that there is in effect a single air outlet (or
only two
or three outlets) formed at the bottom of the structure. In any event, the
outlet or
outlets 314 are adapted for connection to an air intake of the gas turbine,
for
example, by means of the aforementioned air inlet plenum 52.
~s Arranged within the silencing apparatus 300 are a plurality of curved
airflow
splitters that separate the inlet openings 308 to 313 and that extend inwardly
and
downwardly from these inlet openings towards the air outlet or air outlets. In
the
illustrated embodiment there are five of these airflow splitters indicated at
320 to
324. As these splitters are each of similar construction in the illustrated
preferred
Zo embodiment, it will be sufficient herein to describe the construction of
the
uppermost splitter 320. Each of these splitters is formed with a perforated
sheet
metal exterior indicated generally at 326 and is filled with sound attenuating
material 328. Each splitter, including the splitter 320 has an elongate,
vertically
extending planar section 330, the bottom of which is located at the bottom 316
of
as the apparatus. This planar section can terminate with a semi-cylindrical
bottom
edge member 332 if desired. Extending upwardly from the planar section is a
substantially curved upper section 334, the curved sides of which converge at
the
inlet openings to meet at a front edge 336 which extends horizontally.
There are a plurality of airflow passageways 340 that are formed by and
3o between the airflow splitters in the silencing apparatus 300. The airflow
passageways extend from the inlet openings 308 to 313 towards the air outlet
or
air outlets. As shown in Figure 9, these airflow passageways bend
substantially
and an elongate section of each passageway extends substantially vertically.
It will
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CA 02552091 2003-O1-27
-21-
be understood that the number of airflow splitters will vary but, generally
speaking,
in a preferred embodiment of this silencing apparatus 300 there are at least
three
of the airflow splitters. Smaller splitters such as the illustrated splitter
342 can be
provided in one or more of the main airflow passageways if desired. The
smaller
splitter 342 is relatively thin and it has only flat sides with no curved
upper section.
The inclusion of a smaller splitter of this type may be desirable in some
installations in order to provide an improved, more uniform airflow from the
air
outlet and to provide improved sound attenuation.
The illustrated silencing apparatus 300 also has two interior walls indicated
io at 344 and 346 which originally mounted in the duct structure on opposite
sides of
the airflow passageways. These two interior walls are also formed with
perforated
sheet metal and sound attenuating material 348 is arranged between each of
these interior walls and adjacent exterior sidewall 350, 352 of the duct
structure.
These two interior walls extend across the width of the silencing apparatus
from
is vertically extending interior wall 354 to vertically extending interior
wall 356 (see
Figure 10). Sound attenuating material can also be provided behind the
interior
walls 354, 356. Each of the,interior walls 344, 346 has a substantially curved
upper wall section 360, 362 and a planar lower wall section 364, 366 which
extends vertically downwardly from its corresponding upper wall section. The
ao curved upper wall section 360 can have a semi-cylindrical shape as shown in
Figure 9.
A preferred feature of the silencing apparatus 300 is the arrangement of the
inlet openings 308 to 311 as illustrated in Figure 9. These inlet openings
which
constitute most of the inlet opening area are arranged substantially in a
first plane
2s indicated at 370 which extends at an acute angle to a vertical plane
defined by the
vertically extending side 301. The first plane 370 slopes upwardly and
inwardly
towards a center of the top cover 306. With this arrangement, the larger,
upper
openings are protected to some extent from the elements by the top cover 306
and the sides 302 and 304. The top cover 306 tends to prevent rain from
falling
3o into the inlet openings 308 to 311 and thus prevents this water from being
drawn
into the airflow passageways and eventually into the turbine intake. Of
course, it is
also possible to provide a weather hood similar to the weather hoods 122
illustrated in Figure 3 on the silencing apparatus 300. For example a weather
hood
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CA 02552091 2003-O1-27
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could be attached to the edge of the top cover 306 at the side 301, thereby
effectively extending the protection of the top cover.
It will be appreciated by those skilled in the air handling art that the inlet
silencer 18 of the present invention is able to provide the advantages of a
low
s pressure drop in the airflow and smooth transitions from low to high speed
flow,
the latter being at the entrance of the gas turbine. The low pressure drop is
achieved with good aerodynamic design with gradual contraction and expansion
in
the duct profiles and with uniform air distribution across the filters and
coils.
Reference will now be made to Figure 11 which illustrates a second and
io preferred embodiment of a sound attenuating structure or sound attenuating
duct
unit 380 most suitable for the outlet of a gas turbine but also usable as an
outlet
silencer for other power plants producing hot emission gases and even for
other
noise-creating, gasflow-producing devices such as large axial fans for air
handling.
The illustrated sound attenuating structure 380 can be divided into three main
is parts or main sections which are elbow silencer 384, lower stack section
388 and
upper stack section 392. The inner walls of the structure 380 surround a main
airflow passageway 396 that extends through a substantial bend. The bend,
which
preferably is approximately 90 degrees, is located in section 400 of the
passageway 396. There is a circular air inlet 404 located at one end of the
elbow
2o silencer 384 and adapted for connection to the outlet of the gas turbine 12
(Figure
1 ). There are also two side discharge outlets 408 located proximate to an
upper
end of the upper stack section 392 (only one being shown in Figure 11 ).
When assembled, one embodiment of the structure 380 has a height of
about 32 feet (from drain cap 412 to the top of the upper stack section 392).
The
2s elbow silencer 384 weighs 8000 pounds in this particular embodiment and has
a
height of about 11 feet from the drain cap 412 to mating or bolting flange
420. The
elbow silencer has an outer or exterior wall 421 shown in solid lines and an
inner
or interior wall 422 defining part of the airflow passageway 396 shown in
dashed
lines. From side 424 to side 428 of the outer wall, the horizontal separation
3o between the two sides is 6 feet 4 inches. The elbow silencer 428 includes a
horizontal housing section 432. The air inlet 404 is located at one end of the
horizontal housing section 432. The length of the section 432 as measured from
the inlet 404 to a point directly below the side 424 is 5 feet 2 inches. The
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CA 02552091 2003-O1-27
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horizontal housing section is rigidly attached to a vertical housing section
of the
sound attenuating structure 380. The vertical housing section surrounds the
remainder of the main airflow passageway 396.
Gas flows into the horizontal housing section from the turbine in a
s horizontal direction X. In the transition section 432, the passage gradually
and
continuously expands. The passage also changes gradually from circular to
rectangular (like the section 152 shown in Figure 5). As the gas enters the
section
432 at a very high pressure and velocity, pressure taps can be provided at 436
for
measuring pressure. A removable man-way or cover 438 can be provided for
io repair and service purposes.
Referring to Figure 12, which is another elevation view of the sound
attenuating structure 380, a circular ceramic gasket 440 is provided at the
inlet
end of the elbow silencer 384. A number of bolt holes are provided in the
gasket
440 (32 in the illustrated embodiment). Similar to the illustration in Figure
5, the
is passage 396 of the structure 380 has a circular perimeter at the inlet 404,
but
gradually the perimeter becomes more rectangular in shape. Thus straight side
444 of the elbow silencer outer wall and opposite straight side 446 are at the
downstream end of the horizontal transition section 432. A supporting
structure
(which is not fully illustrated) can be assembled around and attached to the
2o exterior of the elbow silencer 384 to support it and the rest of the outlet
attenuating
structure either on the ground or a suitable horizontal floor.
Referring again to Figure 11, in this embodiment a single and relatively
large curved splitter 450 is contained substantially within the elbow silencer
384.
The splitter 450 is positioned substantially in the center of the passage 396.
Outer
2s surtace 454 of the splitter 450 curves in a parallel manner with the inner
walls of
the elbow silencer 384 as illustrated. As will be described, bracket devices
for
attaching the splitter 450 to.exterior walls of the sound attenuating
structure 380
are provided at the side edges of the splitter 450. A relatively thin turning
vane 457
is positioned above the bottom and substantially horizontal portion of the
splitter
so 450. The vane 457 is preferably a curved sheet of quarter inch thick
stainless
steel. Bracket devices for attaching the vane 457 to the exterior steel walls
of the
sound attenuating structure 380 can be provided at the sides of the vane 457
as
explained below. As fluid may find its way to the bottom of the sound
attenuating
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CA 02552091 2003-O1-27
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structure, a drain is provided at the bottom end of the structure. This drain
includes two 2 inch drain pipes (not illustrated) which are vertically
oriented, and
the cap 412.
Figures 13 and 14 illustrate the manner in which the perforated interior
walls in the sound attenuating duct unit (in this case, the elbow silencer
portion)
can be attached to the solid metal exterior walls. In particular, this
preferred
attachment system includes metal mounting plates indicated generally by
reference 600. These mounting plates have outer edges which are rigidly
attached
to the exterior walls 604, preferably by welding. The inner edges of these
plates
io are detachably connected to the interior walls 602. The mounting plates can
be
arranged in spaced-apart, vertical rows as illustrated. For example, as
illustrated in
Figure 13, there are four rows 700 to 703 of mounting plates used to mount the
interior wall 602a which is a curved wall extending through an approximate 90
degree bend. Each of these rows is formed with at least three mounting plates,
is including an upper mounting plate 705, a middle mounting plate 706 and a
much
larger lower mounting plate 708. Extending along each of the two opposite side
walls 710 and 712 of the airflow silencer (in the main vertical section
thereof) are
five rows of mounting plates 714 to 718. Again, each of these rows may
comprise
several mounting plates arranged end to end. Mounting plates of this type are
2o used to attach all of the interior walls of the elbow silencer to the
exterior walls so
that the interior walls will be able to move relative to the exterior walls as
they
thermally expand (as explained further hereinafter).
Also shown in Figure 14 are spaced-apart connecting pins 607 which are
used to attach the mounting plates to their respective interior walls 602.
These
zs connecting pins are rigidly attached to the respective plates such as by
welding
and, in the preferred embodiment, they extend from the inner edges of these
plates and extend through oversized holes in the interior plates that are
larger than
the width of the pins. -
Figure 16 illustrates that in the preferred embodiment the interior wall
3o panels 602 are arranged to overlap at their respective edges. Figure 16
illustrates
how these interior plates overlap in the direction of airflow indicated by the
arrow F
but it should be appreciated that the interior panels also overlap in the
horizontal
direction and at the corners of the interior walls. The purpose of the overlap
is, of
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CA 02552091 2003-O1-27
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course, to prevent any gaps in the interior wall either as a result of thermal
expansion or contraction. To explain further, it will be seen that there is an
edge
section at 720 of the interior wall panel 602' that overlaps and extends along
a
bottom edge section 722 of the interior panel 602". Both of these edge
sections
s are formed with the oversized holes (shown in Figure 15) in order to
accommodate
connecting pins 607 located at 724. Similarly, at the opposite, bottom edge of
the
interior panel 602', there is an edge strip at 726 which is overlapped by an
upper
edge section 728 of another interior panel.
The lower stack section 388 includes a gradually widening portion 460 and
io a rectangular shaped portion 462 of uniform width and cross-section.
Spanning in
the vertical direction from mating or bolting flange 466 to mating or bolting
flange
468, the height of the lower stack in one embodiment section is about 11 feet
and
its weight is 9000 pounds. Two emission test ports 470 extend through the
outer
wall of the stack. The top section of the splitter 450 extends into the lower
stack
is section and (with reference to Figure 12) the bottom of three splitters
475, 477 and
479 extend into the lower stack section. At the mating flange 466 of the
aforementioned preferred embodiment, side 484 of the stack outer wall is
separated from sloping side 486 by a horizontal distance of 6 feet 4 inches.
This
horizontal separation gradually widens to 8 feet 4 inches. With respect to the
other
2o two sides of the outer wall (labeled 492 and 494 in Figure 12), the
horizontal
separation between the sides increases from 4 feet 10 inches to 6 feet 4
inches in
this particular embodiment.
The two outlets 408 are located in the upper stack section 392 and above
sides 495 and 497 of the stack outer wall. The outlets 408 are proximate to an
2s upper end of the vertical housing section. A closed, horizontally extending
roof or
top 500 is provided at the top of the stack. The roof 500 is preferably sloped
so
that water will not puddle on its surface. The top 500 keeps rain and other
undesired matter from finding its way into the structure passage 396. It is
therefore
preferred to have the closed roof 500 and the two adjacent side discharge
outlets
30 408 than an alternative arrangement where the outlet is at the top end of
the stack
facing upwardly.
Longitudinal axis P e~ctends through the centre of the stack. The central
splitter or airflow defining member 477 is aligned with and extends along the
P
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CA 02552091 2003-O1-27
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axis. The outer splitters 475 and 479 are spaced apart from the central
splitter and
on opposite sides of both the P axis and the central splitter. Bracket devices
for
attaching the splitters 475, 477 and 479 to the exterior walls of the sound
attenuating structure 380 are provided at the side edges of the splitters as
will be
explained below.
Unlike the embodiment of the sound attenuating structure illustrated in
Figure 5, the initial splitter 450 located below the downstream splitters 475,
477
and 479 is neither parallel to nor staggered relative to these latter three
splitters. In
addition, there is a difference in the orientation of these splitters. The
downstream
io splitters have major lower portions 476 that extend in substantially
parallel planes
(in particular, vertical planes) that are substantially perpendicular to a
central
widthwise plane extending through the axis P and defined by an upper end
portion
478 of the initial splitter 450. There are advantages to be gained by
reorienting the
downstream splitters in this manner. Firstly, it enables any suitable number
of
is downstream splitters to be used because there is no need to stagger the
splitters
in the transverse direction relative to the initial splitter 450 (or
splitters). It thus
permits more flexibility in the design of the sound attenuating outlet
structure. In
addition, where the outlets 408 are in the opposite vertical sides, it is very
desirable to have a central downstream splitter 477 and the orientation of the
2o downstream splitters enables the outlet structure to have this central
splitter. The
splitters 475, 477 and 479 which are positioned downstream in the main airflow
passageway relative to the splitter 450, divide the main passageway 396 into
four
narrower passageways 502, 504, 506 and 508. The individual widths of these
four
passageways is roughly equal to the transverse width of adjacent splitters
(with
is respect to the region of the straight stack region below the curved region
adjacent
the outlets 408). As hot air flows up the stack, it is directed around the
semi
cylindrical bottom ends of the splitters (these ends being covered with
imperforate
stainless steel). The hot air then flows up through the four narrow
passageways to
exit through the outlets 408 (the airflow at the outlets preferably having a
velocity
3o component in both the horizontal and vertical direction). The velocity of
the exiting
air will be sufficiently high to avoid excessive local pollution.
An upper portion 750 of the central splitter 477 extends upwardly from the
lower portion 476 and its perforated metal exterior panels curve upwardly and
....,.,~".~,..x.~l..~~.~a..-.-..w...~.,~r~.Y.~.....1».-..
CA 02552091 2003-O1-27
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outwardly to the top edges of the gas outlet 408. Each of the outer splitters
475,
479 has an upper portion 752 that curves upwardly and outwardly towards a
respective one of the gas outlets 408. As illustrated, a tapered tail end of
each
splitter 475, 479 is located at the respective outlet 408 and is positioned in
the
vertical center of the outlet.
Referring to Figure 12, in one preferred embodiment the horizontal
separation between the sides 495 and 497 of the stack outer wall at mating or
bolting flange 513 is 6 feet 4 inches. The horizontal separation gradually
increases
towards the top of the stack. Between the outlets 408, the horizontal
separation is
io 8 feet 4 inches. The height of the upper stack section from the top 500 to
the
mating flange 513 is roughly 9 feet 10 inches. In this particular embodiment,
the
upper stack section is the heaviest of the three main sections weighting
approximately 10,500 pounds. Each outlet 408 as measured between side edges
521 and top and bottom edges 519, 520 is 7 feet 8 inches by 2 feet 6 inches. A
is trailing edge of the splitter 475 is located at the illustrated outlet 408.
This trailing
edge extends horizontally between the edges 521. It will be appreciated that
the
outlet 408 is sufficiently large for animals like birds to find their way into
the
exhaust stack and therefore a bird screen (not shown) is preferably placed
over
both of the outlets 408.
2o Figure 18 illustrates the main, curved section of the splitter 450 which
extends through the elbow silencer 384 and which has a narrow, horizontal,
leading edge 531. The splitter is illustrated without top and bottom 12 gauge,
perforated stainless steel side walls attached. Metal side edge plates 532 and
534
of the splitter 450 do not have perforations in them. A number of
interconnecting
2s plates 530 extend between the sides 532 and 534 of the splitter 450. The
horizontal separation between the sides 532 and 534 is the width of the
splitter
450, which has outwardly projecting edge flanges 531, 533 on both side edges.
A
number of slots 536 are provided in the sides 532 and 534 for attaching the
splitter
450 to the walls of the sound attenuating structure 380 as explained further
below.
3o A number of smaller interconnecting plates 540 in combination with the
larger plates 530 divide the interior of the splitter into a number of
compartments
542. As shown, two plates 540 extend between and rigidly connect each pair of
adjacent plates 530. . In each of the compartments 541, a suitable sound
....,..".......w...."~"~"...... "..~""......~.,-.
CA 02552091 2003-O1-27
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attenuating insulation is placed. The insulation can comprise simply mineral
wool
or layers of fiberglass surrounded by mineral wool. Alternatively ceramic-type
insulation can also be used. For gas turbine applications, the insulation
should
withstand high temperatures, for example, 500 degrees Celsius or more. The
s interconnecting plates which define the walls of the compartments help to
hold the
insulation in place. A large number of connecting pins 542 are welded to the
sides
532 and 534 as well as to the interconnecting plates 530 and 540. The pins are
used for attaching the perforated top and bottom walls of the splitter 450,
these
walls being formed with oversized round holes to receive the pins. The pins
are
io also threaded to permit the attachment of nuts and suitable connecting
plates (see
the attachment system illustrated in Figure 15 and explained below in detail).
It is
noted that the lengths of these threaded pins will vary, at least with respect
to
similar pins located in different locations within the sound attenuating
structure
380. When the splitter 450 is fully assembled, a semi-cylindrical metal
channel or
is rounded tail portion 543 made of imperforate stainless steel is attached to
its top
end as shown in Figure 11. An end wall 546 can be provided to close off the
curved section at its upper end (located adjacent to the flange 420).
As shown in Figure 11, there is a relatively short section 545 of the splitter
450 located above the curved section and mounted in the stack section 388. The
ao short section 545 is constructed in a manner similar to the illustrated
curved
section except for the noted differences. The two sections can be attached on
site
by means of bolts or other known fasteners.
Figure 19 illustrates a bottom portion 550 of the splitter 477 shown in Figure
12. The horizontal separation between side edge plates 556 and 558 is the
width
Zs of the splitters 475, 477 and 479. Each side edge plate has outwardly
projecting
edge flanges 555, 557 on its opposite long edges. The width of these three
splitters is approximately 7 feet 7 inches in one preferred embodiment.
Referring
back to Figure 11, the view of the splitter 450 in that figure is in a
direction parallel
with the width of that splitter. Referring back to Figure 12, the view of the
splitters
30 475, 477 and 479 in that figure is in a direction parallel to their widths.
Therefore
the width of the splitters 475, 477 and 479 extends in a horizontal direction
at a
substantial angle to the width of the splitter 450 and the vane 457,
preferably an
angle of 90 degrees about the P axis.
CA 02552091 2003-O1-27
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The side edge plates 556 and 558 are parallel and do not have perforations
in them. Interconnecting plates 554 extend horizontally between the side
plates
556 and 558. The connecting plates 554 are approximately 9 inches wide in one
embodiment. Again slots or openings 536 are provided in the side plates 556
and
558 for attaching the splitter to exterior walls of the sound attenuating
structure.
This is accomplished by means of support brackets 562 which are attached at
spaced-apart locations along the splitter side edges. The brackets 562 include
a
quarter inch thick steel plate 563 and a stainless steel tongue member 564.
Each
io tongue member 564 is perpendicular to the plate 563 and extends through
openings or slots 566, 568 and 536 provided in the stack outer wall, the stack
inner wall and the side of the splitter respectively. Small rectangular 11
gauge
stainless steel pieces 570 also having slots to accommodate the tongue members
(to which they are attached) can be placed adjacent the slots 568 when the
is brackets 562 are put into position. The slots 536 provided in the splitter
sides are
formed in solid boxes 569 (see Figure 20) which are made of stainless steel
having a 12 gauge thickness. The solid boxes are rigidly attached to the
splitter
sides by welding. The support bracket and slots assembly just described along
with being used to connect the splitter 477 to inner walls of the sound
attenuating
2o structure 380 is of course also used in association with the splitters 450,
475 and
479 for the same purpose. This form of connection allows the splitters to
expand
lengthwise quickly as they are heated up and avoids a breakage of the splitter
supports.
Figure 20 illustrates how a solid box can be constructed in the sputter to
2s accommodate each of the inner ends of the brackets 562. The solid box 569
can
be constructed of 12 gauge stainless steel and it extends inwardly from its
respective side edge panel 558 or 556. The box includes inner end wall 730,
top
wall 732, bottom wall 734 apd two opposite side walls 736 that extend between
the top and bottom walls. The side of the box connected to the side edge panel
is
30 open in order to receive the inner end of the tongue member 564. It will be
understood that the purpose of this box is to prevent sound attenuating
material
located in the splitter from escaping out through the side edge of the
splitter. The
slot formed by the box is, of course, large enough, particularly in the
lengthwise
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CA 02552091 2003-O1-27
-30-
direction to accommodate thermal expansion of the splitter. In order to
provide
sufficient structural integrity and strength for the bracket member to support
the
splitter, a thick, rectangular stainless steel plate 737 is provided on the
outside of
the side edge panel 558 and can be welded thereto. This plate also defines the
aforementioned slot 536 through which the tongue member 564 extends.
As explained, the illustrated splitter of Figure 19 is broken into a number of
compartments for securing the insulation. The walls of the compartments are
defined by the side edge panel 556, the side edge pane! 558, metal divider
573,
interconnecting horizontal plates 554 and smaller, vertical interconnecting
plates
io 575. Again the pins 542 are welded to all or most of these members to
permit
attachment of 12 gauge perforated metal sheet 580 which forms an outer wall of
the splitter. It will be appreciated that another similar 12 gauge metal sheet
is
attached on the opposite side of the splitter (not illustrated in this
figure).
Imperforate stainless steel channel or rounded nose portion 582 is attached to
is bottom end 584 of the splitter. The rounded nose portion 582 is at the
leading
edge of the splitter.
The metal sheet 580 is made from stainless steel. It will be appreciated that
all of the perforated metal sheets or panels which are exposed to the exhaust
of
the turbine are preferably stainless steel, because ordinary steel will
corrode too
zo much. Also these perforated steel sheets preferably have an open area of at
least
30% of the total sheet area of the respective sheet. While the inner walls of
the
sound attenuating structure 380 are 11 or 12 gauge stainless steel panels, the
outer walls of the structure 380 are preferably mild steel panels having a
quarter
inch thickness for strength and rigidity. Adjacent panels of the inner or
outer walls
Zs can of course be welded together where a permanent attachment is
acceptable. In
any particular region of the structure 380, the horizontal separation between
the
neighboring inner and outer. walls of the structure 380 can be as little as 4
inches,
or as much as 6 inches.
Along with insulation being contained in the splitters of the sound
3o attenuating structure, sound attenuating insulation 585 extends through the
entire
structure 380 between the interior and the exterior walls of the structure.
What is
suitable for insulation in all of these regions has already been discussed.
CA 02552091 2003-O1-27
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Figures 15 and 16 illustrate metal mounting plates or scallop members 600
which are used to securely attach the perforated inner walls 602 of the sound
attenuating structure to outer walls 604 of the structure. Scallop members 600
are
used throughout the sound attenuating structure 380 to attach walls exposed to
the hot airflow to unexposed walls. It is desirable to minimize the heat
transfer
between walls exposed to the hot airflow and the unexposed walls and the
scallop
members 600 are designed to achieve this objective, while still providing a
good
attachment between the inner and outer walls of the structure 380.
The scallop members 600 for the most part extend perpendicular to the
io walls 602 and 604; however they will vary in size and shape as illustrated
in Figure
16. For example, scallop members just above the drain cap 412 will naturally
be
larger than the scallop members located in the upper section of the exhaust
stack
because of a difference in inner/outer wall separation between the two
regions.
The scallop plates are preferably welded to the outer walls 604. Each of the
is scallop plates 600 has an edge 606 formed with a series of spaced-apart
recesses
605 and an opposite edge 609 (not visible in Figure 15) which can be straight,
angled, or bent depending on the particular location of the plate 600. The 609
edge extends along and is flush with the inner wall 602. Pins 607 are welded
to
each scallop plate 600, and extend past the inner edge of the scallop plate to
be
2o used in conjunction with attachment assemblies or devices 610 for securing
the
interior walls 602 to the scallop plates. These pins 607 have threaded inner
end
sections.
Each of the assemblies 610 includes a connecting plate 614 in the form of
a metal square and a nut 616. Each plate 614 has a hole for receiving an inner
Zs end 618 of a respective one of the connecting pins 607. The nut 616
attaches the
plate 614 to its pin 607 by a threaded attachment. The metal squares extend
over
and close large or oversized holes 615 formed in both the inner walls 602 and
connecting channel members 620. Each channel member 620 has a series of
these oversized holes which are aligned with the holes in the adjacent
interior wall.
3o The elongate channel members 620 extend between the squares of the
assemblies 610 and act as~clamping members to hold the inner wall between
them and the scallop plates: In the corner region 622, a stainless steel
elongate
corner piece 624 is employed. The piece 624 is securely attached to the
adjacent
CA 02552091 2003-O1-27
-32-
and overlapping pertorated sheets of the inner walls 602 by the assemblies 610
and two of the channel members 620. In the upper and lower stack section, the
interior walls 602 are spaced apart from the exterior walls 604 by means of
these
scallop plates 600 by roughly 4 to 6 inches.
s It has been found that even though the metal squares of the assembly 610
cover the large holes of the inner walls 602, insulation or sound attenuating
material between the walls may escape their compartments through the small
holes in the pertorated interior walls. As indicated, it is desirable to use a
very fine
metal screen between the walls to keep the insulation from escaping. Stainless
to steel is a suitable metal for this screen which is located directly under
or out from
the inner walls 602. The location of this screen 613 is indicated in Figure
15. The
threads of one suitable metal screen are about one thousandths of an inch
thick,
with the metal screen having 200 to 240 strands per inch. With respect to the
splitters of the structure 380, the same screen will achieve the same result
with
is respect to sound attenuating material contained in the splitters.
Figure 17, which is another cross-sectional illustration of wall structure
used
in the sound attenuating structure 380, illustrates how the large sections of
the
structure 380 are joined to each other. The illustrated large structure
sections are
the upper stack section 392 and the lower stack section 388. The mating or
bolting
2o flange 513 extends completely around the outside perimeter of the section
392.
The stack section 388 also has the mating or bolting flange 468 extending
around
its outside perimeter. Both of the flanges 468 and 513 can be welded to the
outer
walls 604. A number of fastener assemblies 638, which are bolts with nuts and
washers, are used at spaced apart locations to attach the section 392 to the
as section 388. An 1/8th inch thermoglass gasket 640 is sandwiched between the
flanges 513 and 468. This gasket extends along the entire lower edge of the
stack
section 392, to form a good continuous seal that prevents the escape of the
hot
gases through the joint
Elongate angle pieces 642 are securely attached to the inner walls 602 by
so the assemblies 610 and channel member 620 which were described previously.
In
Figure 17, the two illustrated pins 542 are vertically separated by 8~/2
inches. The
pins 542 are also welded to scallop plates 652 which are similar to the plates
600
described above. The scallop plates 652 are made of 11 gauge stainless steel.
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CA 02552091 2003-O1-27
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Sides 650 of the angle pieces 642 extend horizontally and outwardly towards
the
outer walls 604 but are not connected to the outer walls. Adjacent the sides
650
are ends of the scallop plates 652. Sandwiched between the sides 650 is a
major
portion of the thermoglass gasket 640.
s Referring to Figures 11 and 12, a support structure 482 is assembled
around as well as connected to the lower stack section to support and maintain
the position of the exhaust stack. The illustrated support structure includes
four
vertical posts 670, horizontal connecting frame members 672 and cross pieces
674, 676. Not all of the support structure which is assembled around the sound
io attenuating duct unit 380 is illustrated in Figures 11 and 12, as a variety
of support
structures are possible and can be constructed readily by one skilled in the
art of
frameworks for supporting duct structures.
It will be understood by those skilled in the art that various modifications
and changes can be made to both the preferred inlet silencer and the outlet
is silencer as described above without departing from the spirit and scope of
this
invention. Both the inlet silencer and the outlet silencer can be made
relatively
compact so as to take up a smaller area or distance than previously known
silencer constructions. Various measurements of dimension and weight have been
provided, but variations in the weights and dimensions of various parts of the
inlet
Zo and outlet silencer structures are to be expected for different power
generating or
fan installations. As an example, the stack of the outlet silencing structure
could
be made shorter if necessary to deal with building constraints or it can be
made
longer to satisfy environmental and/or noise concerns. The number of splitters
in
the outlet duct silencer can vary substantially depending on the job or site
Zs requirements. For example, there could be a single splitter only in the
duct unit,
particularly if a large degree of sound reduction is not required. Accordingly
all
such modifications and changes as fall within the scope of the appended claims
are intended to be part of this invention.
