U.S. patent application number 11/153127 was filed with the patent office on 2006-12-21 for acoustic termination for a pressure monitoring system.
This patent application is currently assigned to Siemens Westinghouse Power Corporation. Invention is credited to Weidong Cai.
Application Number | 20060283660 11/153127 |
Document ID | / |
Family ID | 37572251 |
Filed Date | 2006-12-21 |
United States Patent
Application |
20060283660 |
Kind Code |
A1 |
Cai; Weidong |
December 21, 2006 |
Acoustic termination for a pressure monitoring system
Abstract
Aspects of the invention relate to an improved acoustic
termination for a pressure monitoring system. The termination can
include an inner tube having a passage extending therethrough. One
end of the inner tube can extend into an open end of an outer tube,
which is closed at its opposite end. The portion of the inner tube
that extends into the outer tube can include a plurality of
apertures. Sound absorption material can fill the space between the
outer tube and the portion of the inner tube extending therein. A
pressure signal entering the acoustic termination can be
substantially dissipated and can minimize signal reflection from
the termination. As a result a more accurate pressure measurement
can be obtained by a pressure measurement device that operatively
connects to the passage upstream of the termination.
Inventors: |
Cai; Weidong; (Oviedo,
FL) |
Correspondence
Address: |
Siemens Corporation;Intellectual Property Department
170 Wood Avenue South
Iselin
NJ
08830
US
|
Assignee: |
Siemens Westinghouse Power
Corporation
|
Family ID: |
37572251 |
Appl. No.: |
11/153127 |
Filed: |
June 15, 2005 |
Current U.S.
Class: |
181/252 ;
181/256 |
Current CPC
Class: |
F01N 1/04 20130101; F01N
1/006 20130101; G01L 19/0609 20130101; G01L 19/0046 20130101 |
Class at
Publication: |
181/252 ;
181/256 |
International
Class: |
F01N 1/10 20060101
F01N001/10; F01N 1/24 20060101 F01N001/24 |
Claims
1. An acoustic termination for a pressure monitoring system
comprising: an outer tube having an at least partially open first
end and a closed second end, the outer tube having an interior,
wherein at least a portion of the interior is filled with sound
absorption material; and an inner tube having an open inlet end and
an open termination end, the inner tube further having an outer
peripheral surface and an inner peripheral surface, the inner
peripheral surface defining a passage extending through the inner
tube, the inner tube operatively engaging the first end of the
outer tube such that the passage is in fluid communication with the
interior of the outer tube; whereby a pressure signal transmitted
through the inner tube is received within the interior of the outer
tube and dampened by engagement with the sound absorption
material.
2. The acoustic termination of claim 1 wherein the sound absorption
material is fiberglass.
3. The acoustic termination of claim 1 wherein the first end of the
outer tube provides an opening sized to allow passage of the inner
tube such that the opening substantially engages the outer
peripheral surface of the inner tube.
4. The acoustic termination of claim 1 wherein the inlet end of the
inner tube is connected to a pressurized chamber.
5. The acoustic termination of claim 4 wherein the pressurized
chamber is the combustor of a gas turbine engine.
6. The acoustic termination of claim 1 further including: a
pressure measurement device operatively connected in branched
relation to the passage, whereby the pressure measurement device
determines pressure when it is engaged by a pressure signal in the
passage.
7. The acoustic termination of claim 6 wherein the pressure
measurement device is a pressure transducer.
8. The system of claim 1 wherein the termination end of the inner
tube is positioned substantially proximate the first end of the
outer tube, wherein a chamber is defined within the sound
absorption material such that the passage of the inner tube is in
fluid communication with the chamber, whereby a pressure signal
exiting the inner tube is received within the chamber.
9. The system of claim 1 wherein a portion of the inner tube
including the termination end extends into the first end of the
outer tube, wherein the inner tube includes a plurality of
apertures only in the portion of the inner tube that extends into
the outer tube, and wherein the sound absorption material is
provided in the space between the outer peripheral surface of the
inner tube and the inner peripheral surface of the outer tube and
the termination end of the inner tube and the second end of the
outer tube.
10. A pressure monitoring system comprising: a pressurized chamber
containing at least one pressure signal; an outer tube having an at
least partially open first end and a closed second end, the outer
tube having an interior, wherein at least a portion of the interior
is filled with sound absorption material; and an inner tube having
an open inlet end and an open termination end, the inner tube
further having an outer peripheral surface and an inner peripheral
surface, the inner peripheral surface defining a passage extending
through the inner tube, the inner tube operatively engaging the
first end of the outer tube so as to be in fluid communication with
the interior of the outer tube; whereby a pressure signal
transmitted through the inner tube is received within the interior
of the outer tube and dampened by engagement with the sound
absorption material.
11. The system of claim 10 wherein the pressurized chamber is the
combustor of a gas turbine engine.
12. The system of claim 10 wherein the sound absorption material is
fiberglass.
13. The system of claim 10 wherein the termination end of the inner
tube is positioned substantially proximate the second end of the
outer tube, wherein a chamber is defined within the sound
absorption material such that the passage of the inner tube is in
fluid communication with the chamber, whereby a pressure signal
exiting the inner tube is received within the chamber.
14. The system of claim 10 wherein a portion of the inner tube
including the termination end extends into the first end of the
outer tube, wherein the inner tube includes a plurality of
apertures only in the portion of the inner tube that extends into
the outer tube, and wherein the sound absorption material
is-provided in the space between the outer peripheral surface of
the inner tube and the inner peripheral surface of the outer tube
and the termination end of the inner tube and the second end of the
outer tube.
15. The acoustic termination of claim 10 further including: a
pressure measurement device operatively connected in branched
relation to the passage, whereby the pressure measurement device
determines pressure when it is engaged by a pressure signal in the
passage.
16. The acoustic termination of claim 15 wherein the pressure
measurement device is a pressure transducer.
17. A pressure monitoring system comprising: an outer tube having
an at least partially open first end and a closed second end, the
outer tube having an inner peripheral surface; an inner tube having
an open inlet end and an open termination end, the inner tube
further having an outer peripheral surface and an inner peripheral
surface, the inner peripheral surface defining a passage extending
through the inner tube, wherein a portion of the inner tube
including the termination end extends into the first end of the
outer tube, wherein the inner tube includes a plurality of
apertures only in the portion of the inner tube that extends into
the outer tube; a pressure measurement device operatively connected
in branched relation to the passage; and sound absorption material
provided in the space between the outer peripheral surface of the
inner tube and the inner peripheral surface of the outer tube and
the termination end of the inner tube and the second end of the
outer tube, whereby a pressure signal transmitted through the inner
tube engages the pressure measurement device so that the device
determines pressure, and whereby the pressure signal is
substantially dampened by engagement with the sound absorption
material after exiting the inner tube through the apertures and the
termination end.
18. The system of claim 17 wherein the inlet end of the inner tube
is connected to the combustor of a gas turbine engine.
19. The system of claim 17 wherein the sound absorption material is
fiberglass.
20. The system of claim 17 wherein the pressure measurement device
is a pressure transducer.
Description
FIELD OF THE INVENTION
[0001] The invention relates in general to pressure monitoring
systems and, more particularly, to pressure monitoring systems for
turbine engines.
BACKGROUND OF THE INVENTION
[0002] Referring to FIG. 1, a turbine engine 10 includes a
compressor section 12, a combustor section 14 and a turbine section
16. During the operation of the turbine engine 10, fuel and air can
be mixed, ignited and burned in the combustor section 14, producing
superheated gases at high pressures. Dynamic pressure waves,
sometimes referred to as combustion dynamics, can develop during
the combustion process. If sufficiently high in amplitude, these
dynamic pressure waves can cause mechanical damage and reduce
engine life. Accordingly, pressures in the combustor section 14 are
monitored during engine operation.
[0003] Normally, a pressure transducer cannot be directly attached
to the combustor section 14 because the pressure transducer cannot
withstand the temperatures in the combustion chamber. However, FIG.
1 shows one known pressure monitoring system 18 that is configured
to minimize such concerns. A sampling tube 20 is connected to and
extends away from the combustor section 14 to an acoustic
termination 22. As shown in FIG. 2, the termination 22 is formed by
a plurality of smaller tubes 24 enclosed within the larger sampling
tube 20. A pressure transducer can be connected to the sampling
tube 20 upstream of the termination 22.
[0004] Thus, a pressure signal-or wave from the combustor section
14 enters the sampling tube 20 and travels along the sampling tube
20 such that the hot gas from the combustor section 14 cools to a
temperature suitable for interaction with the pressure transducer
28. The pressure signal engages the pressure transducer 28, which
uses the signal to measure the pressure in the combustor section
14. The pressure signal can continue through the sampling tube 20
and encounter the termination 22, which can dampen the signal
primarily through viscous dissipation. The termination 22 can
minimize reflection of the pressure wave to prevent contamination
of the true pressure signal that engages the pressure transducer
28.
[0005] While such a system 18 has proven adequate for measuring
pressure, the termination 22 is expensive. Moreover, there are
concerns of a decrease in system performance due to signal
distortion and contamination. For instance, it has been shown that
the resonant frequency of the pressure sampling tube 20 is
contained in and repeated in the final pressure measurement. This
repetition of the resonant frequency occurs because the pressure
signal is not totally dissipated by the termination 22.
Acoustically, the termination 22 is not completely anechoic, so a
portion of the pressure signal that encounters the termination 22
is reflected back into the pressure sampling tube 20. Consequently,
the pressure measured by the transducer 28 is the summation of at
least the real pressure signal and the reflected pressure signal,
thereby increasing the possibility of signal contamination.
[0006] Thus, there is a need for a pressure monitoring system that
can improve performance by minimizing signal contamination and
distortion. Ideally, such a system can be provided at a reduced
cost.
SUMMARY OF THE INVENTION
[0007] Aspects of the invention are directed to an acoustic
termination for a pressure monitoring system. The system includes
an outer tube that has an at least partially open first end and a
closed second end. The outer tube has an interior. At least a
portion of the interior is filled with sound absorption material,
which can be, for example, fiberglass.
[0008] The system includes an inner tube with an open inlet end and
an open termination end. The inner tube also has an outer
peripheral surface and an inner peripheral surface. The inner
peripheral surface of the inner tube defines a passage extending
through the inner tube. The inner tube operatively engages the
first end of the outer tube such that the passage is in fluid
communication with the interior of the outer tube. In one
embodiment, the first end of the outer tube can provide an opening
sized to allow passage of the inner tube such that the opening
substantially engages the outer peripheral surface of the inner
tube. The inlet end of the inner tube can be connected to a
pressurized chamber, such as the combustor of a gas turbine engine.
A pressure signal transmitted through the inner tube can be
received within the interior of the outer tube and can be dampened
by engagement with the sound absorption material.
[0009] In one embodiment, the termination end of the inner tube can
be positioned substantially proximate the first end of the outer
tube. A chamber can be defined within the sound absorption material
such that the passage of the inner tube is in fluid communication
with the chamber. As a result, a pressure signal exiting the inner
tube can be received within the chamber. In another embodiment, a
portion of the inner tube including the termination end can extend
into the first end of the outer tube. The inner tube can include a
plurality of apertures only in the portion of the inner tube that
extends into the outer tube. In such case, the sound absorption
material can be provided in the space between the outer peripheral
surface of the inner tube and the inner peripheral surface of the
outer tube as well as in the space between the termination end of
the inner tube and the second end of the outer tube.
[0010] The system can further include a pressure measurement device
that is operatively connected in branched relation to the passage.
The pressure measurement device can be a pressure transducer. Thus,
the pressure measurement device can determine pressure when it is
engaged by a pressure signal in the passage.
[0011] In another respect, aspects of the invention are directed to
a pressure monitoring system. The system includes a pressurized
chamber containing at least one pressure signal. The pressurized
chamber can be the combustor of a gas turbine engine.
[0012] The system includes an outer tube and an inner tube. The
outer tube has an at least partially open first end and a closed
second end. The outer tube also has an interior. At least a portion
of the interior is filled with sound absorption material, which can
be, for instance, fiberglass. The inner tube has an open inlet end
and an open termination end. The inner tube also has an outer
peripheral surface and an inner peripheral surface. The inner
peripheral surface defines a passage extending through the inner
tube. The inner tube operatively engages the first end of the outer
tube so as to be in fluid communication with the interior of the
outer tube. Thus, a pressure signal transmitted through the inner
tube can be received within the interior of the outer tube and
dampened by engagement with the sound absorption material.
[0013] In one embodiment, the termination end of the inner tube can
be positioned substantially proximate the second end of the outer
tube. A chamber can be defined within the sound absorption material
such that the passage of the inner tube is in fluid communication
with the chamber. As a result, a pressure signal exiting the inner
tube can be received within the chamber. In another embodiment, a
portion of the inner tube including the termination end can extend
into the first end of the outer tube. The inner tube can include a
plurality of apertures only in the portion of the inner tube that
extends into the outer tube. The sound absorption material can be
provided in the space between the outer peripheral surface of the
inner tube and the inner peripheral surface of the outer tube and
the termination end of the inner tube and the second end of the
outer tube.
[0014] The system can further include a pressure measurement device
operatively connected in branched relation to the passage. The
pressure measurement device can be a pressure transducer. The
pressure measurement device can determine pressure when it is
engaged by a pressure signal in the passage.
[0015] Another pressure monitoring system according to aspects of
the invention includes an outer tube with a first end that is at
least partially open and a second end that is closed. The outer
tube has an inner peripheral surface.
[0016] The system further includes an inner tube with an open inlet
end and an open termination end. The inlet end of the inner tube
can be connected to the combustor of a gas turbine engine. The
inner tube further has an outer peripheral surface and an inner
peripheral surface. The inner peripheral surface defines a passage
extending through the inner tube. A portion of the inner tube,
which includes the termination end, extends into the first end of
the outer tube. The inner tube includes a plurality of apertures
only in the portion of the inner tube that extends into the outer
tube.
[0017] Sound absorption material provided in the space between the
outer peripheral surface of the inner tube and the inner peripheral
surface of the outer tube as well as in the space between the
termination end of the inner tube and the second end of the outer
tube. The sound absorption material can be fiberglass.
[0018] The system includes a pressure measurement device
operatively connected in branched relation to the passage. The
pressure measurement device can be a pressure transducer. Thus, a
pressure signal transmitted through the inner tube can engage the
pressure measurement device so that the device determines pressure.
Further, the pressure signal can be substantially dampened by
engagement with the sound absorption material after exiting the
inner tube through the apertures and the termination end.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a partly diagrammatic view of a prior system for
monitoring pressure in the combustor section of a turbine
engine.
[0020] FIG. 2 is a cross-sectional view of the prior pressure
monitoring system, viewed along line 2-2 in FIG. 1, and showing the
acoustic termination of the system.
[0021] FIG. 3 is a partly diagrammatic view of a system for
monitoring the pressure in the combustor section of a turbine
engine according to aspects of the invention.
[0022] FIG. 4A is a cross-sectional view of the pressure monitoring
system of FIG. 3, viewed along line 4-4, and showing an acoustic
termination according to aspects of the invention.
[0023] FIG. 4B is a cross-sectional view of the pressure monitoring
system of FIG. 3, viewed along line 4-4, and showing an acoustic
termination according to aspects of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0024] Embodiments of the present invention provide a pressure
monitoring system that can minimize signal contamination and
distortion. Embodiments of the invention will be explained in the
context of one possible pressure measurement system, but the
detailed description is intended only as exemplary. Embodiments of
the invention are shown in FIGS. 3-4, but the present invention is
not limited to the illustrated structure or application.
[0025] A pressure monitoring system 30 according to aspects of the
invention can include a number of components. The system 30 can
include an elongated inner tube 32. The inner tube 32 can include
an outer peripheral surface 34 and an inner peripheral surface 36.
The inner peripheral surface 36 can define a passage 38 extending
through the inner tube 32. The inner tube 32 can be formed by a
single tube or a plurality of tube segments. The inner tube 32 can
also include various fittings and/or connectors.
[0026] The inner tube 32 and/or the passage 38 extending
therethrough can be substantially straight, or the inner tube 32
and/or the passage 38 can include one or more bends, turns, tapers
or curves. While the term tube may connote a cylindrical component,
the inner tube 32 and/or the passage 38 can have almost any
cross-sectional shape. Preferably, the inner tube 32 and/or the
passage 38 are substantially circular in cross-section. The inner
tube 32 and/or the passage 38 can also be, for example,
substantially oval, rectangular, triangular or polygonal in
cross-section. Whatever the geometry, the cross-sectional area of
the inner tube 32 and/or the passage 38 is preferably substantially
constant. The inner tube 32 and/or the passage 38 can be sized for
the particular application at hand. The inner tube 32 can be made
of any suitable material.
[0027] The inner tube 32 can have an inlet end 40 and a termination
end 42. Each of the inlet end 40 and the termination end 42 can be
substantially open. The inlet end 40 can be adapted for attachment
to a pressurized chamber, such as the combustor section 14 of a
turbine engine 10. Once attached, the passage 38 and the
pressurized chamber can be in fluid communication. The attachment
between the inlet end 40 of the inner tube 32 and the pressurized
chamber can be achieved in numerous ways including, for example, by
fasteners, adhesives, welding, and mechanical engagement. In any
event, a pressure signal 44 from the pressurized chamber can be
received within the passage 38.
[0028] A pressure measuring device, such as a pressure transducer
50, can be operatively connected in branched relation to the
passage 38. The pressure measuring device can be located along the
passage 38 between the inlet end 40 and the termination end 42,
preferably closer to the termination end 42. In one embodiment,
pressure measuring device can be oriented at about 90 degrees
relative to the passage 38, but other relative orientations are
possible. An opening (not shown) can be provided in the inner tube
32 to receive a portion of the pressure measuring device. The
pressure measuring device can be connected to the inner tube 32 in
various ways including by fasteners, welding, adhesives, and
mechanical engagement.
[0029] The system can include an outer tube 54. The outer tube 54
have an outer peripheral surface 56 and an inner peripheral surface
58. The outer tube 54 can have a substantially hollow interior 59.
The outer tube 54 can have an at least partially open first end 60
and a closed second end 62. As noted earlier, the term "tube" may
connote a cylindrical shape, but the outer tube 54 can have almost
any cross-sectional shape including, for example, circular, oval,
rectangular, polygonal, and triangular. In one embodiment, the
shape of the outer peripheral surface 34 of the inner tube 32 can
substantially correspond to the shape of the inner peripheral
surface 58 of the outer tube 54. The outer tube 54 can be made of
any suitable material and is preferably made of the same material
as the inner tube 32.
[0030] The inner tube 32 can operatively engage the first end 60 of
the outer tube 54 such that the passage 38 is in fluid
communication with the interior 59 of the outer tube 54. Thus, the
interior 59 can receive pressure signal 44 exiting the passage 38.
There are various ways in which the inner tube 32 and the outer
tube case be operatively engaged. For example, a portion of the
inner tube 32 including the termination end 42 can extend into the
interior 59 of the outer tube 54, as shown in FIG. 4A. However, the
entire inner tube 32 does not extend into the outer tube 54. The
inner tube 32 can be positioned substantially coaxially within the
outer tube 54. A space 64 can be defined between the outer
peripheral surface 34 of the inner tube 32 and the inner peripheral
surface 58 of the outer tube 54, and between the termination end 42
of the inner tube 32 and the closed second end 62 of the outer tube
54.
[0031] A substantial portion of the inner tube 32 is free of
apertures; however, a portion of the inner tube 32 can include a
plurality of apertures 52. The location of these apertures 52 on
the inner tube 32 will be described in detail below. The apertures
52 can be any size or shape and can extend at any orientation
through the inner tube 32 from the inner peripheral surface 36 to
the outer peripheral surface 34. In one embodiment, the apertures
52 can be substantially identical in size and shape. However, one
or more of the apertures 52 can be a different size and/or shape
from the other apertures 52. The apertures 52 can be substantially
circular, but other shapes are possible including oval,
rectangular, triangular, polygonal or, just to name a few
possibilities. The apertures 52 can be arranged according to a
pattern or to no pattern at all. In one embodiment, the apertures
52 can be equally spaced from each other.
[0032] It will be noted that the portion of the inner tube 32 that
includes apertures 52 is disposed entirely within the outer tube
54. In other words, the portion of the inner tube 32 containing
apertures 52 does not extend substantially beyond a plane defined
by the first end 60 of the outer tube 54.
[0033] As noted above, the first end 60 of the outer tube 54 can be
at least partially open. It is preferred if the first end 60 of the
outer tube 54 is open just enough to allow passage of the inner
tube 32 so a close fit is achieved. In one embodiment, shown in
FIG. 4, a separate end piece 66 can be attached to the outer tube
54 to form the first end 60. The end piece 66 can be attached to
the outer tube 54 in any of a number of ways, such as by threaded
engagement 68 or/and fasteners (not shown). Thus, the end piece 66
can be selectively attached to and removed from the outer tube 54
as needed. The end piece 66 should remain attached during engine
operation. The end piece 66 can include an opening 70 to allow the
inner tube 32 to pass therethrough. Any space between the first end
60 of the outer tube 54 and the outer peripheral surface 34 of the
inner tube 32 can be closed by, for example, a seal.
[0034] In another embodiment, as shown in FIG. 4B, the termination
end 42 of the inner tube 32 can engage the first end 60 of the
outer tube 54. For instance, the termination end 42 of the inner
tube 32 can be positioned substantially proximate the first end 60
of the outer tube 54. The inner tube 32 may or may not be attached
to the first end 60 of the outer tube 54.
[0035] A substantial portion of the interior 59 of the outer tube
54 can be filled with sound absorption material or dampening
material 72. In the case of the embodiment shown in FIG. 4A, at
least a portion of the space 64 between the inner tube 32 and the
outer tube 54 can be filled with a sound absorption or dampening
material 72, thereby forming an acoustic termination 74.
Preferably, substantially the entire space 64 is filled with the
sound absorption material 72. Thus, the sound absorption material
72 can surround the outer peripheral surface 34 of the inner tube
32 as well as the termination end 42 of the inner tube 32. The
sound absorption material 72 is only needed in the space 64; it is
not needed around the portion of the inner tube 32 that extends
outside of the outer tube 54, which can provide appreciable cost
savings.
[0036] In the case of the embodiment shown in FIG. 4B, it is
preferred if the sound absorption material 72 is provided in the
outer tube 54 so as to define a chamber 75. The chamber 75 can be
in fluid communication with the passage 38 to receive pressure
signals 44 therefrom. The chamber 75 can be almost any shape or
size. Preferably, the chamber 75 is sized and/or shaped to
substantially maintain acoustic continuity so as to minimize
reflection.
[0037] The sound absorption material 72 can be any material that
can dissipate acoustic energy in the pressure signal 44 in the
passage. In one embodiment, the sound absorption material 72 can be
fiber glass or polymer foam. According to one study, a typical
fiber glass with a thickness of about 4 inches (that is, the
distance between the outer peripheral surface 34 of the inner tube
32 and the inner peripheral surface 58 of the outer tube 54 and/or
the distance between the termination end 42 of the inner tube 32
and the second end 62 of the outer tube 54) can dissipate about 60%
of the acoustic energy in the pressure signal 44 for low
frequencies, up to 100 Hertz. As the thickness of the fiber glass
is increased, the amount of dissipation can increase, approaching
from about 95% to about 100%. Therefore, by adjusting the thickness
of the sound absorption material 72, the amount of dissipation can
be adjusted to achieved the desired performance of the acoustic
termination 74.
[0038] In one embodiment, the sound absorption material 72 can be
provided as a pre-treated or pre-formed component that is simply
placed inside the outer tube 54. The pre-formed sound absorption
material 72 can provide an opening sized for receiving the
extending portion of the inner tube 32. Alternatively, the
termination end 42 of the inner tube 32 can be inserted in the
outer tube 54 and the sound absorption material 72 can be packed in
the space 64 therebetween.
[0039] Aside from the thickness of the sound absorption material 72
discussed above, it will be appreciated that other features of the
system 30 can be optimized to achieve the desired performance of
the acoustic termination 74. Examples of such features include but
are not limited to the following: the length of the outer tube 54;
the length of the inner tube 32; the cross-sectional area of the
inner peripheral surface 58 of the outer tube 54; the
cross-sectional area of the inner and outer peripheral surfaces 34,
36 of the inner tube 32; the length which the inner tube 32 extends
into the outer tube 54; and the size, shape and position of the
apertures 52 in the inner tube 32.
[0040] The operation of the pressure monitoring system 30 according
to aspects of the invention will now be described. A pressure
signal 44 from the combustor section 14 can enter the passage 38 at
the inlet end 40. The pressure signal 44 can be in the form of a
wave. The pressure signal 44 can travel along the passage 38 toward
the termination end 42. Because the inner tube 32 does not have
apertures 52 between the inlet end 40 and the acoustic termination
74, there is minimal, if any, loss of the pressure signal 44 as it
travels along the passage 38. If apertures 52 were provided along
the inner tube 32 upstream of the acoustic termination 74, losses
in the pressure signal 44 would occur as the pressure signal 44
traveled through the passage 38, which can potentially result in a
inaccurate pressure measurement.
[0041] The pressure signal 44 can engage the pressure measuring
device, which can use the signal to measure or otherwise determine
the pressure of the pressurized chamber. The pressure signal 44
then travels to the acoustic termination 74.
[0042] As noted earlier in connection with the embodiment shown in
FIG. 4A, the portion of the inner tube 32 extending into the outer
tube 54 includes a plurality of apertures 52. Thus, some of the
pressure signal 44 can exit the inner tube 32 through the apertures
52. The energy of these exiting signals can be dissipated by the
surrounding sound absorption material 72. The remainder of the
pressure signal 44 entering the acoustic termination 74 can exit
the inner tube 32 through the open termination end 42. The acoustic
energy of these exiting signals can likewise be dissipated by the
sound absorption material 72.
[0043] As for the embodiment of the acoustic termination 74 shown
in FIG. 4B, the pressure signal 44 can exit the inner tube 32
through the termination end 42. Such exiting signals can be
received in the chamber 75 and dissipated by the surrounding sound
absorption material 72.
[0044] Thus, it will be appreciated that the acoustic termination
74 according to aspects of the invention can substantially
dissipate the pressure signal 44 and minimize reflection of the
pressure signal 44 into the passage 38. As a result, distortion or
contamination of the pressure signal 44 in the passage 38 can be
minimized.
[0045] The acoustic termination 74 according to aspects of the
invention can result in an appreciable improvement in performance
of the pressure monitoring system 30. Based on one model, the
signal distortion associated with the prior pressure monitoring
system 18 described above is about 10 to 20 percent; that is, about
10 to about 20 percent of the pressure signal 44 is reflected off
of the termination 22. According to the same model, the signal
distortion associated with the system 30 according to aspects of
the invention can be about 5 to about 10 percent. In other words,
about 5 to about 10 percent of the pressure signal 44 is reflected
off of the acoustic termination 74 according to aspects of the
invention. Thus, the acoustic termination 74 according to aspects
of the invention can reduce signal distortion overall by up to
about 50 percent to about 75 percent. In addition to improving
system performance, the acoustic termination 74 of the pressure
monitoring system 30 according to aspects of the invention can be
made relatively easier and at a lower cost compared to the prior
acoustic termination 22.
[0046] The foregoing description is provided in the context of one
possible pressure monitoring system 30. While described in the
context of turbine engines, it will be appreciated that aspects of
the invention are not limited to turbine engines and can be used in
connection with a variety of applications. Thus, it will of course
be understood that the invention is not limited to the specific
details described herein, which are given by way of example only,
and that various modifications and alterations are possible within
the scope of the invention as defined in the following claims.
* * * * *