U.S. patent application number 14/856728 was filed with the patent office on 2017-03-23 for method and system for thermal expansion compensation in heated flow characterization.
The applicant listed for this patent is Siemens Energy, Inc.. Invention is credited to Heiko Claussen, Upul P. DeSilva.
Application Number | 20170082032 14/856728 |
Document ID | / |
Family ID | 58056753 |
Filed Date | 2017-03-23 |
United States Patent
Application |
20170082032 |
Kind Code |
A1 |
DeSilva; Upul P. ; et
al. |
March 23, 2017 |
METHOD AND SYSTEM FOR THERMAL EXPANSION COMPENSATION IN HEATED FLOW
CHARACTERIZATION
Abstract
Techniques for a chamber, such as gas turbine engine (100),
surrounding a heated fluid include a sensor (150) mounted in a
first wall (228b, 229b) of the chamber to detect phenomenon inside
the chamber and a processor (702). The processor is in electrical
communication with the sensor and is configured to receive first
data, determine a first temperature of the first wall, determine a
current path length, determine properties of the fluid flow, and
operate a device based on the properties. First data indicates a
value of the phenomenon along a path between the first wall and a
different wall of the chamber. The current path length (268b) is
based on a nominal path length (268a) and thermal expansion of the
first wall due to the first temperature. The property of fluid flow
in the chamber is based on the first data and the current path
length.
Inventors: |
DeSilva; Upul P.; (Oviedo,
FL) ; Claussen; Heiko; (North Brunswick, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Siemens Energy, Inc. |
Orlando |
FL |
US |
|
|
Family ID: |
58056753 |
Appl. No.: |
14/856728 |
Filed: |
September 17, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01K 13/02 20130101;
F05D 2260/80 20130101; F02C 9/00 20130101; G01P 5/245 20130101;
G01K 1/20 20130101; G01K 11/24 20130101; G01M 15/14 20130101 |
International
Class: |
F02C 9/00 20060101
F02C009/00; G01M 15/14 20060101 G01M015/14 |
Claims
1. A system comprising: a chamber configured to surround a heated
fluid; a sensor mounted in a first wall of the chamber to detect a
phenomenon in the chamber; a device affected by a property of the
heated fluid; and a processor in electrical communication with the
sensor, the processor configured to perform at least the steps of:
receiving from the sensor first data that indicates a value for the
phenomenon along a path through the chamber between the first wall
and a different wall of the chamber, determining a first
temperature of the first wall; determining a current path length of
the path based at least in part on a nominal path length for a
nominal temperature different from the first temperature and
thermal expansion of the first wall due to the first temperature;
determining a property of fluid flow in the chamber based on the
first data and the current path length of the path; and operating
the device based on the property of fluid flow in the chamber.
2. A system as recited in claim 1, wherein. the chamber is at least
one of a combustor in a gas turbine engine or an exhaust diffuser
in a gas turbine engine; the sensor is an acoustic sensor; the
phenomenon is acoustic travel time; and the property is temperature
or velocity or both.
3. A system as recited in claim 1, wherein: the sensor is at a
first distance from a nearest structural support for the chamber;
and determining the current path length further comprises
determining the current path length of the path based at least in
part on the first distance.
4. A system as recited in claim 1 wherein determining the first
temperature further comprises determining the first temperature
based on the first data and the nominal path length.
5. A system as recited in claim 1 further comprising a first
temperature sensor in thermal contact with the first wall, wherein:
the processor is further configured for receiving from the first
temperature sensor second data that indicates a temperature of the
first wall; and determining the first temperature further comprises
determining the first temperature equal to the temperature of the
first wall based on the second data.
6. A system as recited in claim 5, wherein: the first wall
comprises an inner plate and an outer plate separated by an
thermally insulating material; the sensor is mounted to both the
inner plate and the outer plate; the system further comprises a
second temperature sensor; the first temperature sensor is disposed
in thermal contact with the inner plate; the second temperature
sensor is disposed in thermal contact with the outer plate; the
first temperature is the temperature of the inner plate of the
first wall; the processor is further configured for receiving from
the second temperature sensor third data that indicates a second
temperature of the outer plate of the first wall; and determining
the current path length further comprises determining the current
path length based on a difference between the thermal expansion of
the inner plate of the first wall due to the first temperature and
thermal expansion of the outer plate of the first wall due to the
second temperature.
7. A system as recited in claim 5, wherein: a sensitivity of the
sensor depends on temperature; the system further comprises a
second temperature sensor disposed in thermal contact with the
sensor; the processor is further configured for receiving from the
second temperature sensor third data that indicates a second
temperature of the sensor; and determining the property of the
fluid flow in the chamber further comprises determining the
property of the fluid flow in the chamber based on the second
temperature of the sensor.
8. A system as recited in claim 5, wherein: the sensor is an
acoustic transducer mounted in an acoustic waveguide in the first
wall which opens into an inside of the chamber and for which the
acoustic path depends on temperature; the system further comprises
a second temperature sensor disposed in thermal contact with the
acoustic waveguide; the processor is further configured for
receiving from the second temperature sensor third data that
indicates a second temperature of the acoustic waveguide; and
determining the current path length further comprises determining
the current path length based on the second temperature of the
acoustic waveguide.
9. A method comprising: receiving on a processor, from a sensor
mounted in a first wall of a chamber to detect a phenomenon in the
chamber configured to surround a heated fluid, first data that
indicates a value of the phenomenon along a path through the
chamber between the first wall and a different wall of the chamber,
determining on a processor a first temperature of the first wall;
determining on a processor a current path length of the path based
at least in part on a nominal path length for a nominal temperature
different from the first temperature and thermal expansion of the
first wall due to the first temperature; determining on a processor
a property of fluid flow in the chamber based on the first data and
the current path length of the path; and causing a device to be
operated based on the property of fluid flow in the chamber.
10. A method as recited in claim 9, wherein. the chamber is at
least one of a combustor in a gas turbine engine or an exhaust
diffuser in a gas turbine engine; the sensor is an acoustic sensor;
the phenomenon is acoustic travel time; and the property is
temperature or velocity or both.
11. A method as recited in claim 9, wherein: the sensor is at a
first distance from a nearest structural support for the chamber;
and determining the current path length further comprises
determining the current path length of the path based at least in
part on the first distance.
12. A method as recited in claim 9 wherein determining the first
temperature further comprises determining the first temperature
based on the first data and the nominal path length.
13. A method as recited in claim 9, wherein: the method further
comprises receiving on a processor, from a first temperature sensor
in thermal contact with the first wall, second data that indicates
a temperature of the first wall; and determining the first
temperature further comprises determining the first temperature
equal to the temperature of the first wall based on the second
data.
14. A method as recited in claim 13, wherein: the first wall
comprises an inner plate and an outer plate separated by an
thermally insulating material; the sensor is mounted to both the
inner plate and the outer plate; the first temperature sensor is
disposed in thermal contact with the inner plate; the first
temperature is the temperature of the inner plate of the first
wall; the method further comprises receiving from a second
temperature sensor third data that indicates a second temperature
of the outer plate of the first wall, wherein the second
temperature sensor is disposed in thermal contact with the outer
plate; and determining the current path length further comprises
determining the current path length based on a difference between
the thermal expansion of the inner plate of the first wall due to
the first temperature and thermal expansion of the outer plate of
the first wall due to the second temperature.
15. A method as recited in claim 13, wherein: a sensitivity of the
sensor depends on temperature; the method further comprises
receiving on a processor, from a second temperature sensor disposed
in thermal contact with the sensor, third data that indicates a
second temperature of the sensor; and determining the property of
the fluid flow in the chamber further comprises determining the
property of the fluid flow in the chamber based on the second
temperature of the sensor.
16. A method as recited in claim 13, wherein: the sensor is an
acoustic transducer mounted in an acoustic waveguide in the first
wall which opens into an inside of the chamber and for which the
acoustic path depends on temperature; the method further comprises
receiving on a processor, from a second temperature sensor disposed
in thermal contact with the acoustic waveguide, third data that
indicates a second temperature of the acoustic waveguide; and
determining the current path length further comprises determining
the current path length based on the second temperature of the
acoustic waveguide.
17. A non-transitory computer readable medium carrying one or more
sequences of instructions, wherein execution of the one or more
sequences of instructions by one or more processors causes the one
or more processors to perform the steps of: receiving from a sensor
mounted in a first wall of a chamber to detect phenomenon in the
chamber configured to surround a heated fluid, first data that
indicates a value of the phenomenon along a path through the
chamber between the first wall and a different wall of the chamber,
determining a first temperature of the first wall; determining a
current path length of the path based at least in part on a nominal
path length for a nominal temperature different from the first
temperature and thermal expansion of the first wall due to the
first temperature; determining a property of fluid flow in the
chamber based on the first data and the current path length of the
path; and causing a device to be operated based on the property of
fluid flow in the chamber.
18. A non-transitory computer readable medium as recited in claim
17, wherein: execution of the one or more sequences of instructions
further causes the one or more processors to perform the step of
receiving, from a first temperature sensor in thermal contact with
the first wall, second data that indicates a temperature of the
first wall; and determining the first temperature further comprises
determining the first temperature equal to the temperature of the
first wall based on the second data.
19. A non-transitory computer readable medium as recited in claim
18, wherein: the first wall comprises an inner plate and an outer
plate separated by an thermally insulating material; the sensor is
mounted to both the inner plate and the outer plate; the first
temperature sensor is disposed in thermal contact with the inner
plate; the first temperature is the temperature of the inner plate
of the first wall; execution of the one or more sequences of
instructions further causes the one or more processors to perform
the step of receiving from a second temperature sensor third data
that indicates a second temperature of the outer plate of the first
wall, wherein the second temperature sensor is disposed in thermal
contact with the outer plate; and determining the current path
length further comprises determining the current path length based
on a difference between the thermal expansion of the inner plate of
the first wall due to the first temperature and thermal expansion
of the outer plate of the first wall due to the second
temperature.
20. A non-transitory computer readable medium as recited in claim
18, wherein: the sensor is an acoustic transducer mounted in an
acoustic waveguide in the first wall which opens into an inside of
the chamber and for which the path is an acoustic path that depends
on temperature; execution of the one or more sequences of
instructions further causes the one or more processors to perform
the step of receiving, from a second temperature sensor disposed in
thermal contact with the acoustic waveguide, third data that
indicates a second temperature of the acoustic waveguide; and
determining the current path length further comprises determining
the current path length based on the second temperature of the
acoustic waveguide.
Description
FIELD OF THE INVENTION
[0001] The various embodiments relate to determining the
distribution of fluid properties in a chamber of heated fluid, such
as gas flow properties in a gas turbine engine.
BACKGROUND OF THE INVENTION
[0002] A gas turbine engine is a flow machine in which a
pressurized gas expands. The gas turbine includes a turbine or
expander, a compressor connected upstream of the turbine, and a
combustion chamber between the compressor and turbine. Expanding
gas produced in the combustion chamber drives blades of the turbine
which provides power for the compressor and other engine output.
The compression of air by way of the blading of one or more
compressor stages, subsequently mixes the compressed air in the
combustion chamber with a gaseous or liquid fuel, where the mixture
is ignited by an igniter to initiate combustion. The combustion
results in a hot gas (mixture composed of combustion gas products
and residual components of air) which expands in the following
turbine section, with thermal energy being converted into
mechanical energy in the process to drive an axial shaft. The shaft
is connected to and drives the compressor. The shaft also drives a
generator, a propeller or other rotating loads. In the case of a
jet power plant, the thermal energy also accelerates a hot gas
exhaust stream, which generates the jet thrust.
[0003] The gas turbine engine is designed to operate within certain
ranges of pressure, velocity and temperatures of both the air and
hot gas combustion products that vary with location through the
engine. Optimal performance is achieved within very narrow ranges.
Thus, to validate the design or to ensure that the gas turbine
engine is operating within specified ranges or to make adjustments
to attain the optimal performance, it is desirable to know the
actual distribution of temperature, pressure and velocity during
operation. Determining such distributions is challenging, at least
in part, because the pressures and temperature can become very
great.
[0004] Current approaches to monitoring the distribution of
pressure, temperature and velocity in a gas turbine engine include
some intrusive probes that project into the gas flows, including
probes mounted on vanes (e.g., Kielhead probes) to obtain some
profiles of velocity and temperature. Optical instruments have been
used, but the characteristics of the optical devices can degrade at
the extreme temperatures in at least portions of the turbine
engine. Non-intrusive acoustic approaches have been implemented and
promise to avoid deficiencies in other approaches.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Various embodiments of the invention are explained in the
following description in view of the drawings that show:
[0006] FIG. 1A is a block diagram that illustrates an example
radial cross section of a gas turbine engine and control system,
according to an embodiment;
[0007] FIG. 1B is a block diagram that illustrates an example axial
cross section of a gas turbine engine with components of a control
system, according to an embodiment;
[0008] FIG. 2A through FIG. 2C are block diagrams that illustrate
an upper half of a cross section of a gas turbine engine with
example configuration of acoustic transducers and temperature
sensors; according to various embodiments;
[0009] FIG. 3 is a graph that illustrates an example series of
known acoustic signals that can be used alone or in combination by
an acoustic actuator, according to various embodiments;
[0010] FIG. 4 is a flow diagram that illustrates an example method
for compensating for thermal expansion while determining a property
of fluid flow in a chamber, according to an embodiment;
[0011] FIG. 5 is a diagram that illustrates an example exhaust
diffuser with multiple acoustic transducers and at least one pair
of temperature sensors, according to an embodiment;
[0012] FIG. 6A and FIG. 6B are diagrams that illustrate two views
of an example acoustic transducer and example temperature sensors
relative to a space inside an exhaust diffuser, according to one
embodiment;
[0013] FIG. 7 is a block diagram that illustrates a computer system
upon which an embodiment of the invention may be implemented;
and
[0014] FIG. 8 is a block diagram that illustrates a chip set upon
which an embodiment of the invention may be implemented.
DETAILED DESCRIPTION OF THE INVENTION
[0015] An acoustic temperature and velocity mapping sensor system
characterizes the hot fluid flows in real time under extreme
environments such as boilers, gas turbine exhausts and gas turbine
combustors. This sensor technology is based on continuously finding
the time of flight of acoustic waves accurately across a space of
the fluid flow. Although this method has very high accuracy, the
inventors recognized that some uncertainty is introduced into the
derivation of fluid flow properties due to thermal expansion of the
walls that hold the acoustic transducers and enclose the space of
the fluid flow. Acoustic calibration can reduce this to some
degree. For example auto calibration of distances at a known
temperature (e.g., ambient temperatures for an offline turbine) can
provide precise distance information, e.g., as described in
PCT/US2014/039971, the entire contents of which are hereby
incorporated by reference as if fully set forth herein, except for
terminology inconsistent with that used herein. However, during
transitions from one fluid temperature to another, the distances
the acoustic signals travel between emitting and receiving acoustic
transducers, and within an acoustic waveguide, change with the
changing temperatures. This effect causes increased uncertainty in
the measurement and therefore in the derived fluid flow properties,
such as fluid flow temperatures or velocities.
[0016] A method and system are described for compensating for
thermal expansion when determining a distribution of properties in
a chamber with a heated moving fluid, such as liquid in a boiler or
gas in a gas turbine engine. As used herein a fluid is a material
state that moves in response to a shearing stress, and includes
both gas and liquid states of a material. In a gas turbine engine
the fluid is a gas comprising air, or an air and fuel mixture, or
gases that result from combustion of air and fuel, or some
combination. As used herein a chamber is a structure with one or
more walls that surround, but need not enclose, a fluid, such as a
gas or liquid.
[0017] Although embodiments are described below with reference to
acoustic sensors, in other embodiments thermal expansion is used to
correct properties of the heated fluid based on measurements of a
phenomenon made by other sensors. For example, the phenomenon
refraction in the chamber is measured by optical sensors to
determine an index of refraction of the fluid in the chamber and
thus, for many materials, the property of temperature of fluid
flow; or, the phenomenon of travel time of an optical pulse is
measured to determine the index of refraction which can be used to
determine the fluid property of temperature for many materials; or,
the phenomenon is a number of scatterers in a beam of light is
detected by an optical sensor to and used to derive the property of
the concentration of particulates in the fluid flow. Furthermore,
all sensing systems that rely on a sensor network or array, such as
around the periphery of the turbine exhaust or combustor, and that
evaluate properties of the fluid flow (direction, speed,
temperature, density, mass flow, gas constant, gas composition)
will rely somewhat on the accuracy of the knowledge of the sensor
positions themselves. The reason that these methods have multiple
sensors is that they compare the measurements, such as through
triangulation or beamforming, which are dependent on the sensor
locations. Optical systems that have to be calibrated for the
measurement distance or sensor locations include laser Doppler
velocimetry or particle tracking velocimetry. All these
measurements are affected by the actual dimensions of the chamber
which can change due to thermal expansion. Thus, in general a
sensor is mounted in a first wall of the chamber to detect a
phenomenon in the chamber. A processor in electrical communication
with the sensor is configured to receive from the sensor first data
that indicates a value for the phenomenon along a path through the
chamber between the first wall and a different wall of the chamber.
The same or different processor determines a first temperature of
the first wall, in some embodiments based on the sensor measurement
itself, as described below. The same or different processor
determines a current path length of the path based at least in part
on a nominal path length for a nominal temperature different from
the first temperature and thermal expansion of the first wall due
to the first temperature. The same or different processor then
determines a property of fluid flow in the chamber based on the
first data and the current path length of the path.
[0018] FIG. 1A is a block diagram that illustrates an example
radial cross section of a gas turbine engine and control system
100, according to an embodiment. This cross section includes a
housing 110 symmetrically disposed around an axial shaft 122 that
is perpendicular to the view of FIG. 1A. The shaft is part of a
shaft assembly 120 that encloses the shaft and seals, at least
partially, the gases inside the shaft assembly 120 from a main flow
of air or other gas between the shaft assembly 120 and the housing
110. Fixed to the housing 110 and shaft assembly 120 are one or
more stator stages of stator vanes 140. Each stator stage includes
multiple stator vanes 140 spaced azimuthally around the shaft
assembly 120. The stator vanes direct the main flow onto the rotor
blades 130 in one or more rotor stages. Each rotor stage includes
multiple rotor blades 130 spaced azimuthally around the shaft
assembly 120 and displaced axially from a corresponding stator
stage. Each rotor blade is connected to the axial shaft 122 and
configured to rotate with the shaft 122 around an axis of rotation
of the axial shaft, which runs along a length of the shaft, and
thus is also perpendicular to the view of FIG. 1A.
[0019] Also included in this cross section is an acoustic actuator
160 (also called an acoustic transmitter) configured to introduce
acoustic energy into the main gas flow (called simply gas flow
hereinafter), and an acoustic sensor 150 (also called acoustic
receiver) configured to detect acoustic energy from the gas flow.
In some embodiments, there are multiple acoustic actuators 160 or
acoustic sensors 150 or both, collectively called acoustic
transducers. In some embodiments, either or both of one or more
acoustic actuators 160 and acoustic sensors 150 are acoustic
transceivers that are acoustic transducers that can both emit and
detect acoustic signals. In some embodiments, there are no acoustic
actuators.
[0020] The acoustic actuator is driven by electronic signals sent
by control system 170 and electronic signals output from acoustic
sensor 150 are collected and processed into acoustic data, or
stored, or some combination, at the control system 170. The control
system 170 includes a chip set as depicted in FIG. 8 or a computer
system as depicted in FIG. 7, and as described in more detail below
in reference to those figures. The lines connecting sensor 150 and
actuator 160 to control system 170 indicate channels of electrical
communication and may be wired or wireless.
[0021] Also included in system 100 are zero or more temperature
sensors, such as pair 109 of temperature sensors. The sensors are
configured to determine the temperature changes in one or more
walls that enclose a space where the gas flow is to be
characterized in order to compensate for thermal expansion changing
the length of acoustic paths from acoustic actuator 160 to acoustic
sensor 150. Although the temperatures they provide can be used to
derive a temperature boundary condition for the space in some
embodiments, these temperature sensors are not designed to measure
the temperature of the fluid flow away from the walls. The pair 109
of temperature sensors are also connected to the control system 170
by one or more wired or wireless channels of electrical
communication. In some embodiments, no temperature sensors are
used.
[0022] The control system includes a thermal compensation module
180 configured to deduce the distribution of temperature and
velocity in at least a portion of the main flow based on the data
collected from the acoustic sensor 150 while compensating for
thermal expansion of the walls bordering the space based on the one
or more temperature sensors. In some embodiments, no temperature
sensors are used; and, instead, the derived gas flow temperatures
are used to estimate the wall temperatures and resulting thermal
expansion. In some of these embodiments, temperature in the gas
flow is then recomputed using the thermally expanded distances. The
temperature at the wall can be determined in an iterative or
optimization approach in various embodiments.
[0023] In some embodiments, the acoustic actuator 160 is omitted.
In some embodiments, the acoustic actuator 160 is configured to
place acoustic signals into the gas flow, using signals that are
designed to assist in the determination of the distribution of
temperature or velocity, or both, in the gas flow of the gas
turbine engine 100 in the presence of other acoustic signals or in
the presence of acoustic or electronic noise, or some
combination.
[0024] FIG. 1B is a block diagram that illustrates an example axial
cross section of a gas turbine engine and control system 100,
according to an embodiment. The system includes housing 110, shaft
assembly 120, rotor blades 130, stator vanes 140, acoustic sensor
150, acoustic actuator 160, pair 109 of temperature sensors and
thermal compensation module 180 as defined above with reference to
FIG. 1A. As can be seen in FIG. 1B, along the axis the engine
includes, in succession, an inlet section 112, a compressor section
114, a compressor diffuser section 115, a combustion section 116, a
transition section 117, a turbine section 118, and an exhaust
section 119. In some embodiments, one or more of these sections are
omitted, but all gas turbine engines include a compressor section
114, a combustion section 116 and a turbine section 118.
[0025] Once the air flows out of the compressor diffuser section
115, it enters the combustion section 116, also called the
combustor, where fuel is added and the mixture is ignited.
Combustion liners position and control the fire resulting from
combustion in order to prevent flame contact with any metal parts
that would be softened or melted in contact with the flame. For
example, six combustion liners (cans) are positioned at different
azimuthal positions within an annulus created by inner and outer
combustion cases adjacent the shaft assembly 120 and housing 110,
respectively. In some embodiments, the exhaust section includes an
exhaust diffuser where velocity is reduced by diffusion and
pressure is recovered. At the exit of the exhaust diffuser, turning
vanes direct the gases into an exhaust plenum, a separate space
provided for air circulation. In this configuration, the chamber is
one or more sections of the gas turbine engine, or portions
thereof; and, the walls of the chamber are made up of an inner wall
of the housing 110, and, if present, an outer wall of the shaft
assembly, in one or more sections of the engine, or portions
thereof.
[0026] FIG. 2A and FIG. 2B are block diagrams that illustrate an
upper half of a cross section of a gas turbine engine 201 with
example configuration of acoustic transducers and temperature
sensors; according to various embodiments. The control system (such
as control system 170) and communication lines thereto of a
complete system for engine 201 are omitted for clarity. The portion
of the cross section depicted is above an axial shaft 222, and
includes an upper portion of a shaft assembly 220 and housing 210
separated by gas flow spaces in each of multiple chambers defined
by one or more of multiple stages of rotors and stators in each of
an inlet section 212, compressor section 214, diffusor section 115,
combustion section 216, transition section 217, turbine section 218
and exhaust section 219, analogous to those sections described
above. Also depicted is an igniter 202 in the combustion section
216 and a combustion liner 204 (can) that extends from the
combustion section 216 through the transition section 217 and
discharges into the turbine section 218.
[0027] According to various embodiments, one or more acoustic
transducers 256 (such as actuators, sensors or transceivers) are
mounted to emit and detect acoustic signals in a space of gas flow
through a chamber of the gas turbine engine without extending into
the space. In other embodiments, such as in some embodiments
described in more detail below, the transducers 256 are disposed in
different sections of a gas turbine engine than depicted with
transducers 256 in FIG. 2A. To compensate for thermal expansion,
zero or more temperature sensors, such as pairs 290 of temperature
sensors, are also included in walls of chambers that border one or
more spaces to be probed acoustically by transducers 256 to
characterize temperature or velocity, or both, of the gas flow away
from the walls.
[0028] In one embodiment, the sections outlined by a dotted curve
in FIG. 2A are populated with one or more sensors 250 or actuators
260 or transceivers 258. While acoustic actuators (transmitters)
and sensors (receivers) are distinguished in embodiments depicted
in FIG. 2B among other drawings to follow, it is understood that in
alternative embodiments one or more are each replaced by an
acoustic transceiver that can function as both an acoustic sensor
and an acoustic actuator at the same time or at different times, or
by a sensor of a different type configured to make measurement of
other physical phenomena.
[0029] In the sections indicated by dotted line in FIG. 2A, FIG. 2B
depicts the housing 210 that includes a combustion liner 204 and an
outer wall 229b of an exhaust diffuser 229, and the shaft assembly
220 that includes the axial shaft 222 and an inner wall 229a of the
exhaust diffuser 229. For purposes of illustration, it is assumed
that at increased temperatures, as experienced during normal or
hotter operations, the exhaust diffuser 229 and the combustion
liner 204 undergo some degree of thermal expansion so that their
walls move relative to their cooler disposition. The expanded
location of these walls are illustrated by the dotted lines
adjacent to inner wall 229a and outer wall 229b of exhaust diffuser
229 and wall 228a of combustion liner 204. Note that these are
block diagrams not drawn to scale and the positions of the dotted
lines are drawn in order to highlight the phenomenon without
obscuring the diagram. It is further assumed that one wall is fixed
by support structures at fewer locations so that it is more free to
move in response to the thermal expansion than another wall. For
example, it is assumed that outer wall 229b of exhaust diffuser 229
is freer to respond to the thermal expansion than the inner wall
229a of the exhaust diffuser 229. Similarly, it is assumed that
wall 228a of combustion liner 204 is freer to respond to the
thermal expansion than the opposite wall 228b of the combustion
liner 204.
[0030] One or more acoustic sensors 250 (represented by open
circles) or acoustic actuators 260 (represented by filled circles)
or acoustic transceivers 258a and 258b (collectively referenced
hereinafter as transceivers 258 and represented by half-filled
circles) are mounted in or opposite the walls that are expanding
freely. The acoustic measurements made by these sensors, actuators
and transceivers are affected by the geometrical changes of the
spaces they are monitoring, or by geometrical changes of acoustic
or other waveguides feeding acoustic or optical energy into or out
of the spaces, due to thermal expansion.
[0031] For example, at cooler or design temperatures, the acoustic
path 265a through a space in the exhaust diffuser 229 from actuator
260 to sensor 250 has a nominal path length. But, after thermal
expansion at higher temperatures, the sensor 250 is displaced
further from the actuator 260 as indicated by the dashed open
circle. In this expanded state, the acoustic path 265b is longer.
Similarly, at cooler or design temperatures, the acoustic path 266a
through a space in the exhaust diffuser 229 back and forth at
transceiver 258a has a nominal path length. But, after thermal
expansion at higher temperatures, the transceiver 258a is displaced
further from the reflecting inner wall 229a. In this expanded
state, the acoustic path 266b is longer.
[0032] Even if the acoustic transducer is not in the wall with more
freedom to expand, the acoustic geometry is affected. For example,
at cooler or design temperatures, the acoustic path 267 through a
space in the combustion liner 204 back and forth at transceiver
258b has a nominal path length. But, after thermal expansion at
higher temperatures, the reflecting inner wall 228a is displaced
further from the transceiver 258b. In this expanded state, the
acoustic path (not shown) is longer.
[0033] FIG. 2C depicts the housing 210 that includes a combustion
liner 204 and an outer wall 229b of an exhaust diffuser 229, and
the shaft assembly 220 that does not extend into the exhaust
diffuser 229. For purposes of illustration, it is assumed that at
increased temperatures, as experienced during normal or hotter
operations, the exhaust diffuser 229 and the combustion liner 204
undergo some degree of thermal expansion so that their walls move
relative to their cooler disposition. The expanded locations of
these walls are illustrated by the dotted lines adjacent to the
opposite portions of the outer wall 229b of exhaust diffuser 229
depicted in FIG. 2C. Note that these are block diagrams not drawn
to scale and the positions of the dotted lines are drawn in order
to highlight the phenomenon without obscuring the diagram. In this
embodiment, the detected acoustic beams 268a, 268b, 269a, 269b are
reflected off, or detected by acoustic transducers on, opposite
sides of the same outer wall 229b. With the nearest support
structures at an upstream end of this outer wall 229b, this outer
wall 229b is free to expand more than any other wall depicted in
FIG. 2C.
[0034] In various embodiments, the effect of thermal expansion is
computed and used to compensate for path length changes of the
acoustic beams based on wall temperatures determined by zero or
more temperature sensors, or a temperature difference at a pair of
temperature sensors, such as thermocouples that operate readily at
the high temperatures inside combustion cans and exhaust diffusers.
This is demonstrated schematically in both FIG. 2B and FIG. 2C by
the pair 291 of temperature sensors in an outer wall 229b of
exhaust diffuser 229, and by temperatures sensors 292a and 292b,
collectively referred to hereinafter as pair 292 of temperature
sensors, in inner wall 228a and outer wall 228b, respectively, of
combustion liner 204.
[0035] According to various embodiments of the acoustic systems to
determine gas flow temperature or velocity, the acoustic signals
used are distinctive from ordinary sounds made during operation of
the gas turbine engines and from each other. FIG. 3 is a graph 600
that illustrates an example series of known acoustic signals that
can be used alone or in combination by one or more acoustic
actuators or transceivers, according to various embodiments. As can
be seen, the distinctive signals are depicted as distinct frequency
marks, generally designated 610, that are spaced apart in
frequency, i.e., are non-broadband, and are discontinuous in time.
That is, a sub-group of distinct frequencies, e.g., four or five
frequencies, are transmitted as a signal sub-group at a particular
time for a short duration (about 100 milliseconds). Different
signal sub-groups are transmitted sequentially in time. The
distinctive signal from one acoustic actuator (transmitter or
transceiver) is made up of one or more sub-groups. Different
acoustic actuators use different sets of one or more sub-groups. In
some embodiments different frequency chirps are used by different
actuators.
[0036] As illustrated in FIG. 3, each signal sub-group is
designated as 621 through 630, and the frequency marks for signal
sub-group 621, marking distinct frequencies, are designated as
621a, 621b, 621c, 621d. The corresponding received signal can be
correlated with this signal to determine the time of maximum
correlation. That time indicates the time that this signal reached
that sensor and can be detected in the presence of noise and other
sounds originating in the gas turbine engine.
[0037] Each successive signal sub-group 622 through 630 includes
different distinct frequencies from the frequencies in the other
signal sub-groups. Hence, in addition to the signal sub-groups
621-630 each forming a distinct identifiable pattern, or individual
signature, along the frequency axis, the series of successive
signal sub-groups 621-630 also form a distinct identifiable
pattern, or overall signature, of frequencies along the time axis.
Forming a signature of a plurality of the sub-groups increases the
distinctness of the signature, improves detectability, and provides
a more precise autocorrelation peak in time, thus ensuring an
accurate travel time measurement.
[0038] FIG. 4 is a flow diagram that illustrates an example method
for compensating for thermal expansion while determining
temperature property of fluid flow in a chamber, according to an
embodiment. Although steps are depicted in FIG. 4 as integral steps
in a particular order for purposes of illustration, in other
embodiments, one or more steps, or portions thereof, are performed
in a different order, or overlapping in time, in series or in
parallel, or are omitted, or one or more additional steps are
added, or the method is changed in some combination of ways.
[0039] In step 401 one or more sensors (e.g., acoustic transducers)
in a wall of a chamber are used as a corresponding number of
sources or receivers to introduce or detect, or both, distinctive
signals of some phenomenon, e.g., as depicted in FIG. 3 for
acoustic signals, into a space inside the chamber to be monitored.
In various embodiments, the chamber is a boiler or portion thereof
configured for heating one or more liquids, such as water, or is
one or more sections, or portions thereof, of a gas turbine engine,
or is a heat exhaust system, e.g., from a power plant or other
facility. In an illustrated embodiment, the space is acoustically
monitored for deducing sound travel time along one or more acoustic
paths; and, hence for inferring temperature or velocity of fluid
flow, or both, in the space inside the chamber. If not already
mounted on a wall of the chamber, the one or more sensors for the
phenomenon are mounted on one or more walls of the chamber during
step 401. One or more sensors are selected during step 401 based on
the susceptibility of the sensors to have their measurements
affected by thermal expansion as the walls of the chamber are
heated. Such walls are often supported by few or far support
structures, such as brackets or legs. Thus method 401 applies to a
system that includes a chamber configured to surround a heated
fluid, and a sensor mounted in a first wall of the chamber to
detect a phenomenon in the chamber. For convenience the phenomenon
data collected from the sensor is called "first" data.
[0040] For example, in one embodiment, during step 401, transceiver
258b is selected as making measurements along acoustic path 267
subject to error due to the expansion of wall 228 during heated
operations outside calibrated conditions. In another embodiment,
during step 401, the transducer pair made up of actuator 260 and
sensor 220 is selected as making the measurements along acoustic
paths 265a subject to error due to the expansion of diffuser outer
wall 229b during heated operations outside calibrated conditions.
This causes the actual acoustic path 265b to be longer than the
nominal path 265a in a manner that depends on the temperature of
the outer wall 229b. In yet another embodiment, during step 401,
the transceiver 258a is selected as making the measurements along
acoustic path 266a subject to error due to the expansion of
diffuser outer wall 229b during heated operations outside
calibrated conditions. This causes the actual acoustic path 266b to
be longer than the nominal path 266a in a manner that depends on
the temperature of the outer wall 229b. In some embodiments
multiple acoustic transducers are selected for a corresponding
number of spaces, e.g., for both the combustion liner 204 and the
exhaust diffuser 229. In some embodiments, the diffuser is aft of
any shaft assembly and the reflective surface or second acoustic
transducer is on an opposite outer wall, as depicted in FIG.
2C.
[0041] In step 403, one wall is selected for measuring temperature.
For example, in some embodiments the selected wall is the wall that
has greater freedom to expand with temperature increases than any
other wall adjacent to the space being acoustically monitored. For
example, in one illustrated embodiment, combustion liner wall 228a
is assumed to be less rigidly supported and therefore is assumed to
have more freedom to move during thermal expansion and is therefore
selected during step 403 as the "first" wall. Similarly, in another
illustrated embodiment, exhaust diffuser outer wall 229b is assumed
to be less rigidly supported and therefore is assumed to have more
freedom to move during thermal expansion and is therefore selected
as the "first" wall during step 403.
[0042] In step 405 a "first" temperature sensor is mounted in
thermal contact with an inner surface of the first wall to monitor
temperature of the first wall, for each of one or more chambers, or
spaces in a single chamber, to be monitored. In some embodiments,
mounting the first temperature sensor is done to determine the
temperature controlling thermal expansion of the wall most free to
respond. In some embodiments, the hottest wall temperature is of
interest and the temperature sensor is mounted to respond to the
temperature on the surface of the wall closest to the hottest
expected fluid flow, which is expected to be the hottest surface of
the wall. This may or may not be the wall or surface on which the
sensor (e.g., the acoustic transducer) or sensors are mounted, or
the wall most free to expand. In embodiments with a large wall, the
measurements of the phenomenon are made in many places and the
thermal expansion is distributed differently depending on
temperature changes along the large wall. In some such embodiments,
the step of inserting a temperature sensor on the first wall is
repeated along many locations on one or more walls. A thermocouple
is a suitable temperature sensor for the hot temperatures in a gas
turbine engine.
[0043] In some embodiments, the first wall is made up of two or
more thermally conducting plates, such as metal or composite
plates, separated by an insulating material, such as air. In some
such embodiments, the temperature sensor is mounted in thermal
contact with the inner plate closest to the heated fluid inside the
chamber. In some embodiments, the temperature sensor is mounted in
thermal contact with a different plate and calibration information
is used to infer the temperature of the inner plate of the first
wall based on the temperature measured at a different plate in the
first wall. Thus, a first temperature sensor is configured to
detect a temperature of the first wall.
[0044] In step 406 a "second" temperature sensor is mounted in
thermal contact with an outer surface of the first wall to monitor
ambient temperature away from the gas flow, for each chamber or
space to be monitored. This step is done to take account of thermal
gradients in the first wall that can affect transducers mounted
away from the inner surface of the first wall. For example, in some
embodiments, as described in more detail below with reference to
FIG. 6B, the acoustic transducer is included in an acoustic
waveguide, such as a horn, that is mounted to the first wall at
both an inner plate and an outer plate of a first wall, with
multiple plates separated by an thermal insulator. In such
embodiments it is advantageous to know the difference in the
thermal expansion between the inner surface and outer surface of
the first wall. Both temperatures have an effect on the length of
the acoustic path and potentially the angle of the acoustic
waveguide horn if the two surfaces of the first wall expand
differently. Even though the outer surface temperature may not be
as important as the inner surface temperature, the outer surface
temperature could still have an effect on the acoustic path that is
advantageously compensated. Thus, in some embodiments, the system
further comprises a second temperature sensor disposed in thermal
contact with the outer plate.
[0045] In some embodiments, the first wall is a good thermal
conductor, or the acoustic transducers are mounted to the inner
surface or inner plate of the first wall, or otherwise the geometry
of the acoustic transducers are affected only by thermal expansion
of the inner surface of the first wall; and, in some such
embodiments step 406 is omitted.
[0046] In step 407 one or more extra temperature sensors, called a
"third" temperature sensor, is mounted in thermal contact with a
sensor or waveguide. This step is done to take account of
temperature sensitivity of the sensor or thermal expansion of a
waveguide, or both. For example, in some embodiments, the acoustic
transducer sensitivity depends on the temperature or must be cooled
if the acoustic transducer becomes too hot. Thus, in some
embodiments, the system further comprises an extra temperature
sensor disposed in thermal contact with the acoustic transducer. In
some of these embodiments the acoustic transducer is cooled if the
extra temperature sensor records a temperature over a threshold at
which cooling is desirable. In other embodiments, as described in
more detail below with reference to FIG. 6B, the acoustic
transducer is included in an acoustic waveguide, such as a horn.
The acoustic waveguide is subject to thermal expansion itself, due
to its own cooler temperature at a location removed from the
hottest surfaces of the first wall of the chamber. Thus, in some
embodiments, the system further comprises an extra temperature
sensor disposed in thermal contact with the acoustic waveguide.
[0047] Recall that the data about the phenomenon collected from the
sensor is called first data. In step 409, "second" data is
collected from the one or more first temperature sensors, if
present, in thermal contact with an inner surface of the first
wall. The second data indicates temperature differences between the
current temperature of the first wall and a nominal temperature at
which the path lengths of various acoustic paths are known, e.g.,
from acoustic calibration at a known nominal temperature. It is
often convenient for the nominal temperature to be an ambient
temperature, such as room temperature (20 degrees Centigrade), when
it is safe to enter the chamber to make measurements. Furthermore,
in some embodiments, the calibration is done when the chamber is
away from harsh environments, e.g., inside an air-conditioned
facility, and all its metal parts are at the same ambient
temperature not only because it is safe to probe the chamber, but
also because the temperature distribution is known relatively
accurately without tedious and costly 2D mapping with thermocouples
or other devices.
[0048] In some embodiments, step 409 includes collecting "third"
data from the one or more second temperature sensors, if present,
in thermal contact with an outer surface of the first wall. In some
embodiments, step 409 includes collecting "fourth" data from the
one or more extra temperature sensors, if present, in thermal
contact with the sensor or a waveguide in the first wall.
[0049] In step 411, the "first" data is collected at a processor,
such as in control system 170, from the one or more sensors. For
example, the first data indicates acoustic travel time between the
actuator and sensor transducers on one or more paths through each
space of one or more chambers. For example, a processor in
electrical communication with the acoustic sensor is configured to
receive from the acoustic sensor first data that indicates travel
time along an acoustic path through the chamber between the first
wall and a different wall of the chamber, such as an inner wall
229a or an opposite portion of the outer wall 229b.
[0050] In some embodiments an initial estimate of wall temperature
is inferred from an acoustic travel time measurement, e.g., based
on first arrival on an acoustic path along the first wall from two
transducers on the first wall with a known nominal path length.
Short path lengths are advantageous for this temperature
determination because such paths are less affected by thermal
expansion. In some such embodiments, steps 405, 406 and 407 are
omitted. For example, in some such embodiments, the processor
determines a first temperature of the first wall based on the first
data and a nominal path length of one or more paths.
[0051] In step 413, for a current space through the chamber, a path
length in the space is determined based on the nominal path length
and thermal expansion due to the temperature difference. In various
embodiments, the path length is known for a nominal temperature,
such as ambient temperature before the fluid in the chamber is
subjected to heating. The degree of thermal expansion from the
nominal geometry is due to the temperature change from the nominal
temperature when the geometry was calibrated. In various
embodiments, a path length at a nominal temperature is known or
calibrated with acoustic travel times at the known nominal
temperature for which the sound speed can be derived.
[0052] In some embodiments, the thermal expansion is also dependent
on the distance from the sensor to the one or more adjacent or
nearest supports for the chamber that constrain expansion.
[0053] The path length is also affected by the angle of a
waveguide, such as a horn, which is affected, in some embodiments,
by the differential expansion of the inner and outer points where
the waveguide is fixed to the first wall, such as at an inner plate
and an outer plate of a first wall.
[0054] For example, for a circular wall, such as a radial plane
slice of the outer wall 229b of the exhaust diffuser 229 of FIG.
2C, the circumference, c, of the wall is related to the radius, r,
at the nominal temperature by equation 1.
c.sub.0=2.pi.r.sub.0 (1)
where c.sub.0 is the circumference at a nominal initial
temperature, e.g., when the geometry is calibrated and known, and
r.sub.0 is the radius at the nominal temperature. The change in
circumference, dc, due to a temperature change, dt, can be
expressed by Equation 2.
dc=2.pi.r.sub.0dt.alpha. (2)
where .alpha. is the linear thermal expansion coefficient and has
units of millimeters (mm, 1 mm=10.sup.-3 meters) of expansion per
meter (m) of initial length (or in some embodiment fractional
length change) per degree Celsius (.degree. C.). For the stainless
steel material making up the example exhaust diffuser,
.alpha.=19.times.10.sup.-5 per .degree. C. The final circumference,
c.sub.1, and radius r.sub.1 after changing temperature by dt are
related to initial values by Equation 3a.
dc=c.sub.1-c.sub.0=2.pi.r.sub.1-2.pi.r.sub.0 (3a)
which, when combined with Equation 2, gives Equation 3b
2.pi.r.sub.1-2.pi.r.sub.0=2.pi.r.sub.0dt.alpha. (3b)
Which can be divided by 2.pi. and rearranged to give the final
radius using Equation 4.
r.sub.1=r.sub.0dt.alpha.+r.sub.0=r.sub.0(dt.alpha.+1) (4).
In general, the distance D between two acoustic transducers on an
unconstrained wall undergoing temperature change dt given by
{Tnew-Told} is given by Equation 5.
Dnew=Dold({Tnew-Told}.alpha.+1) (5)
In some embodiments the nominal temperature, Told, is the ambient
temperature when the distance between acoustic transducers was
calibrated.
[0055] The thermal expansion compensated path length for the
current space is then determined in step 413 based on the new
positions of the acoustic transducers and the new radius of the
reflecting wall on the opposite side of the space, both of which
depend on the temperature difference {Tnew-Told}. Thus, the system
includes a processor configured to determine a current path length
of the path based at least in part on a nominal path length for a
nominal temperature different from the first temperature and
thermal expansion of the first wall due to the first
temperature.
[0056] In some embodiments, the sensor is at a first distance from
a nearest structural support for the chamber; and, determining the
current path length includes determining the current path length of
the acoustic path based at least in part on the first distance.
[0057] In some embodiments, the first wall includes an inner plate
and an outer plate separated by a thermally insulating material and
the sensor is mounted to both the inner plate and the outer plate.
In some such embodiments; the system further includes a second
temperature sensor. The first temperature sensor is disposed in
thermal contact with the inner plate; and, the second temperature
sensor is disposed in thermal contact with the outer plate. The
first temperature is the temperature of the inner plate of the
first wall. The processor is further configured for receiving from
the second temperature sensor third data that indicates a second
temperature of the outer plate of the first wall. In these
embodiments; determining the current path length includes
determining the current path length based on a difference between
the thermal expansion of the inner plate of the first wall due to
the first temperature and thermal expansion of the outer plate of
the first wall due to the second temperature.
[0058] In some of these embodiments, the sensor is mounted in a
waveguide in the first wall which opens into an inside of the
chamber and for which the path through the chamber depends on
temperature, e.g., by changing the angle of the waveguide relative
to a wall of the chamber or changing the length of the waveguide,
or some combination. In some of these embodiments, the system
includes an extra temperature sensor disposed in thermal contact
with the waveguide. The processor is further configured for
receiving from the extra temperature sensor extra data that
indicates a temperature of the waveguide. In some of these
embodiments, determining the current path length includes
determining the current path length based on the temperature of the
waveguide.
[0059] In step 415, a property (such as either the temperature or
the velocity, or both) of the gas flow is determined in the current
space based on the first data (e.g., indicating the travel time)
and on the thermal expansion compensated path length for the
current space (called the current path length, for convenience)
determined in step 413. In some of these embodiments, a sensitivity
of the sensor depends on temperature and the system includes an
extra temperature sensor disposed in thermal contact with the
sensor. The processor is further configured for receiving from the
extra temperature sensor fourth data that indicates a temperature
of the sensor. In these embodiments, determining the property of
the fluid flow in the chamber includes determining the property of
the fluid flow in the chamber based on the temperature of the
sensor. In some embodiments, a device, such as a coolant pump, is
operated to cool the acoustic transducer in response to the
temperature from the extra temperature sensor.
[0060] In some embodiments, in step 415, a spatial distribution of
the fluid property within the current space is determined based on
tomography (e.g., the inverse Radon transform, well known in the
art) and multiple paths through the same space, e.g., for each of
multiple different paths through the chamber. In some embodiments,
there is an insufficient number of paths through each space; and, a
spatial distribution is not determined in step 415.
[0061] Thus, the system includes a processor configured to
determine a property of fluid flow in the chamber based on the
first data and the current path length of the path.
[0062] In step 421, it is determined by module 180 whether there is
another space to probe with different sensors. If so, control
passes back to step 411. If not, then control passes to step 423.
In some embodiments, step 423 is performed before step 421. In some
embodiments, steps 413 and 415 are performed simultaneously by
controller 170 for all paths or all spaces or some combination.
[0063] In step 423 a result is presented on a display device, or
operation or design of the device including the chamber is
modified, based on the fluid flow property in one or more spaces
inside the chamber. Thus, the system includes a processor
configured to operate a device (e.g., present a result on a
computer display 714 or change operation of a boiler or gas turbine
engine 100) based on the property (e.g., temperature or velocity)
of fluid flow in the chamber.
[0064] In an example embodiment, temperature sensors are mounted on
the inner and outer plates of an outer wall 229b of an exhaust
diffuser in a gas turbine engine. FIG. 5 is a block diagram that
illustrates an example exhaust diffuser 500 with multiple acoustic
transducers 556 and at least one pair 590 of temperature sensors,
according to an embodiment. This diffuser 500 is similar to the
configuration shown in FIG. 2C, with no intervening shaft assembly.
The outer plate 521a of the outer wall 520 of the exhaust diffuser
500 with circular cross section is shown in perspective view. An
acoustic path between transducers 556a and 556b reflected off the
opposite wall is affected by thermal expansion of outer wall 520
due to heat from the gas flow contained within. Data is collected
from pair 590 of temperature sensors and acoustic transducer 556a
over wired or wireless lines of electrical communication 572 by
control system 570 with thermal compensation module 580, which are
embodiments of control system 170 and thermal compensation module
189, respectively, described above with reference to FIG. 1A. These
embodiments are specific for including compensation of thermal
expansion of outer wall 520 of exhaust diffuser 500. A close-up
view of acoustic transducer 556a and pair 590 of temperature
sensors is shown in FIG. 6A.
[0065] FIG. 6A and FIG. 6B are block diagrams that illustrate two
views of an example acoustic transducer and temperature sensors
relative to a space inside an exhaust diffuser, according to one
embodiment. In this embodiment, outer wall 520 includes an inner
plate 521b and an outer plate 521a separated by a thermal
insulating material, e.g., air. FIG. 6A is a close up of a
perspective view of an outer plate 521a of an outer wall 520 of the
exhaust diffuser 500. Outer wall 520, outer plate 521a, acoustic
transducer 556a, and lines of electrical communication 572 are as
described above. The pair 590 of temperatures sensors is seen in
this view to include a "second" temperature sensor 594 on the outer
plate 521a and access port 591 to "first` temperature sensor 592 in
thermal contact with a plate adjacent to the gas flow. Also shown
is an access port 597 to an extra temperature sensor 598.
[0066] FIG. 6B is a block diagram that illustrates an example cross
section through the outer wall 520. The outer plate 521a, acoustic
transducer 556a, wired or wireless lines of electrical
communication 572, and "second" temperature sensor 594 are as
described above. The "first" temperatures sensor 592 is shown in
thermal contact with an inner plate 521b of the outer wall 520.
This measures the hottest surface of the outer wall 520 and its
temperature reading is assumed to control the thermal expansion of
the inner plate 521b.
[0067] The acoustic transducer 556a is in an acoustic waveguide
horn. The acoustic waves, represented schematically by dotted
wavefronts, are generated currently on the open end of the horn
that shows an open hole in FIG. 6B. The acoustic waves are
omnidirectional, fill the horn and are than nearly omnidirectional
emitted into the space inside the diffuser 500. The so called
acoustic beam 562 represents the single path from another source
that arrives at the membrane of the microphone of the transducer
556a. Each path from different sources will arrive from a slightly
different angle as all sources emit in all directions and based on
the temperature, flow and position of the source vs receiver, the
successful path that connects the source to the receiver is
slightly different. The acoustic beam 562 used to probe the space
of the gas flow is shown relative to the acoustic transducer 556a,
and represents one acoustic path to one other acoustic transducer
(or a reflected path back to transducer 556a).
[0068] Also shown is an extra temperature sensor 598 used in some
embodiments for the determination the temperature of the waveguide,
to allow the thermal expansion of the waveguide to be determined or
to indicate whether the acoustic transducer may need cooling to
stay within an operational temperature range, or both.
[0069] In some embodiments, both inner wall and outer wall
movements of diffuser 500 are compensated for thermal expansion.
Inner wall motion changes the hot gas volume and radial component
of the path length whereas outer wall movement changes the distance
between the acoustic transducer, and thus the axial component of
the path length, in this embodiment. In some embodiments, a
separate temperature sensor is used to determine the temperature of
the inner wall (e.g., inner wall 229a) of an exhaust diffuser
(e.g., diffuser 229).
[0070] FIG. 7 is a block diagram that illustrates a computer system
700 upon which an embodiment of the invention may be implemented.
Computer system 700 includes a communication mechanism such as a
bus 710 for passing information between other internal and external
components of the computer system 700. Information is represented
as physical signals of a measurable phenomenon, typically electric
voltages, but including, in other embodiments, such phenomena as
magnetic, electromagnetic, pressure, chemical, molecular atomic and
quantum interactions. For example, north and south magnetic fields,
or a zero and non-zero electric voltage, represent two states (0,
1) of a binary digit (bit). Other phenomena can represent digits of
a higher base. A superposition of multiple simultaneous quantum
states before measurement represents a quantum bit (qubit). A
sequence of one or more digits constitutes digital data that is
used to represent a number or code for a character. In some
embodiments, information called analog data is represented by a
near continuum of measurable values within a particular range.
Computer system 700, or a portion thereof, constitutes a means for
performing one or more steps of one or more methods described
herein.
[0071] A sequence of binary digits constitutes digital data that is
used to represent a number or code for a character. A bus 710
includes many parallel conductors of information so that
information is transferred quickly among devices coupled to the bus
710. One or more processors 702 for processing information are
coupled with the bus 710. A processor 702 performs a set of
operations on information. The set of operations include bringing
information in from the bus 710 and placing information on the bus
710. The set of operations also typically include comparing two or
more units of information, shifting positions of units of
information, and combining two or more units of information, such
as by addition or multiplication. A sequence of operations to be
executed by the processor 702 constitutes computer
instructions.
[0072] Computer system 700 also includes a memory 704 coupled to
bus 710. The memory 704, such as a random access memory (RAM) or
other dynamic storage device, stores information including computer
instructions. Dynamic memory allows information stored therein to
be changed by the computer system 700. RAM allows a unit of
information stored at a location called a memory address to be
stored and retrieved independently of information at neighboring
addresses. The memory 704 is also used by the processor 702 to
store temporary values during execution of computer instructions.
The computer system 700 also includes a read only memory (ROM) 706
or other static storage device coupled to the bus 710 for storing
static information, including instructions, that is not changed by
the computer system 700. Also coupled to bus 710 is a non-volatile
(persistent) storage device 708, such as a magnetic disk or optical
disk, for storing information, including instructions, that
persists even when the computer system 700 is turned off or
otherwise loses power.
[0073] Information, including instructions, is provided to the bus
710 for use by the processor from an external input device 712,
such as a keyboard containing alphanumeric keys operated by a human
user, or a sensor. A sensor detects conditions in its vicinity and
transforms those detections into signals compatible with the
signals used to represent information in computer system 700. Other
external devices coupled to bus 710, used primarily for interacting
with humans, include a display device 714, such as a cathode ray
tube (CRT) or a liquid crystal display (LCD), for presenting
images, and a pointing device 716, such as a mouse or a trackball
or cursor direction keys, for controlling a position of a small
cursor image presented on the display 714 and issuing commands
associated with graphical elements presented on the display
714.
[0074] In the illustrated embodiment, special purpose hardware,
such as an application specific integrated circuit (IC) 720, is
coupled to bus 710. The special purpose hardware is configured to
perform operations not performed by processor 702 quickly enough
for special purposes. Examples of application specific ICs include
graphics accelerator cards for generating images for display 714,
cryptographic boards for encrypting and decrypting messages sent
over a network, speech recognition, and interfaces to special
external devices, such as robotic arms and medical scanning
equipment that repeatedly perform some complex sequence of
operations that are more efficiently implemented in hardware.
[0075] Computer system 700 also includes one or more instances of a
communications interface 770 coupled to bus 710. Communication
interface 770 provides a two-way communication coupling to a
variety of external devices that operate with their own processors,
such as printers, scanners and external disks. In general the
coupling is with a network link 778 that is connected to a local
network 780 to which a variety of external devices with their own
processors are connected. For example, communication interface 770
may be a parallel port or a serial port or a universal serial bus
(USB) port on a personal computer. In some embodiments,
communications interface 770 is an integrated services digital
network (ISDN) card or a digital subscriber line (DSL) card or a
telephone modem that provides an information communication
connection to a corresponding type of telephone line. In some
embodiments, a communication interface 770 is a cable modem that
converts signals on bus 710 into signals for a communication
connection over a coaxial cable or into optical signals for a
communication connection over a fiber optic cable. As another
example, communications interface 770 may be a local area network
(LAN) card to provide a data communication connection to a
compatible LAN, such as Ethernet. Wireless links may also be
implemented. Carrier waves, such as acoustic waves and
electromagnetic waves, including radio, optical and infrared waves
travel through space without wires or cables. Signals include
man-made variations in amplitude, frequency, phase, polarization or
other physical properties of carrier waves. For wireless links, the
communications interface 770 sends and receives electrical,
acoustic or electromagnetic signals, including infrared and optical
signals, which carry information streams, such as digital data.
[0076] The term computer-readable medium is used herein to refer to
any medium that participates in providing information to processor
702, including instructions for execution. Such a medium may take
many forms, including, but not limited to, non-volatile media,
volatile media and transmission media. Non-volatile media include,
for example, optical or magnetic disks, such as storage device 708.
Volatile media include, for example, dynamic memory 704.
Transmission media include, for example, coaxial cables, copper
wire, fiber optic cables, and waves that travel through space
without wires or cables, such as acoustic waves and electromagnetic
waves, including radio, optical and infrared waves. The term
computer-readable storage medium is used herein to refer to any
medium that participates in providing information to processor 702,
except for transmission media.
[0077] Common forms of computer-readable media include, for
example, a floppy disk, a flexible disk, a hard disk, a magnetic
tape, or any other magnetic medium, a compact disk ROM (CD-ROM), a
digital video disk (DVD) or any other optical medium, punch cards,
paper tape, or any other physical medium with patterns of holes, a
RAM, a programmable ROM (PROM), an erasable PROM (EPROM), a
FLASH-EPROM, or any other memory chip or cartridge, a carrier wave,
or any other medium from which a computer can read. The term
non-transitory computer-readable storage medium is used herein to
refer to any medium that participates in providing information to
processor 702, except for carrier waves and other signals.
[0078] Logic encoded in one or more tangible media includes one or
both of processor instructions on a computer-readable storage media
and special purpose hardware, such as ASIC 720.
[0079] Network link 778 typically provides information
communication through one or more networks to other devices that
use or process the information. For example, network link 778 may
provide a connection through local network 780 to a host computer
782 or to equipment 784 operated by an Internet Service Provider
(ISP). ISP equipment 784 in turn provides data communication
services through the public, world-wide packet-switching
communication network of networks now commonly referred to as the
Internet 790. A computer called a server 792 connected to the
Internet provides a service in response to information received
over the Internet. For example, server 792 provides information
representing video data for presentation at display 714.
[0080] The invention is related to the use of computer system 700
for implementing the techniques described herein. According to one
embodiment of the invention, those techniques are performed by
computer system 700 in response to processor 702 executing one or
more sequences of one or more instructions contained in memory 704.
Such instructions, also called software and program code, may be
read into memory 704 from another computer-readable medium such as
storage device 708. Execution of the sequences of instructions
contained in memory 704 causes processor 702 to perform the method
steps described herein. In alternative embodiments, hardware, such
as application specific integrated circuit 720, may be used in
place of or in combination with software to implement the
invention. Thus, embodiments of the invention are not limited to
any specific combination of hardware and software.
[0081] The signals transmitted over network link 778 and other
networks through communications interface 770, carry information to
and from computer system 700. Computer system 700 can send and
receive information, including program code, through the networks
780, 790 among others, through network link 778 and communications
interface 770. In an example using the Internet 790, a server 792
transmits program code for a particular application, requested by a
message sent from computer 700, through Internet 790, ISP equipment
784, local network 780 and communications interface 770. The
received code may be executed by processor 702 as it is received,
or may be stored in storage device 708 or other non-volatile
storage for later execution, or both. In this manner, computer
system 700 may obtain application program code in the form of a
signal on a carrier wave.
[0082] Various forms of computer readable media may be involved in
carrying one or more sequence of instructions or data or both to
processor 702 for execution. For example, instructions and data may
initially be carried on a magnetic disk of a remote computer such
as host 782. The remote computer loads the instructions and data
into its dynamic memory and sends the instructions and data over a
telephone line using a modem. A modem local to the computer system
700 receives the instructions and data on a telephone line and uses
an infra-red transmitter to convert the instructions and data to a
signal on an infra-red a carrier wave serving as the network link
778. An infrared detector serving as communications interface 770
receives the instructions and data carried in the infrared signal
and places information representing the instructions and data onto
bus 710. Bus 710 carries the information to memory 704 from which
processor 702 retrieves and executes the instructions using some of
the data sent with the instructions. The instructions and data
received in memory 704 may optionally be stored on storage device
708, either before or after execution by the processor 702.
[0083] FIG. 8 illustrates a chip set 800 upon which an embodiment
of the invention may be implemented. Chip set 800 is programmed to
perform one or more steps of a method described herein and
includes, for instance, the processor and memory components
described with respect to FIG. 7 incorporated in one or more
physical packages (e.g., chips). By way of example, a physical
package includes an arrangement of one or more materials,
components, and/or wires on a structural assembly (e.g., a
baseboard) to provide one or more characteristics such as physical
strength, conservation of size, and/or limitation of electrical
interaction. It is contemplated that in certain embodiments the
chip set can be implemented in a single chip. Chip set 800, or a
portion thereof, constitutes a means for performing one or more
steps of a method described herein.
[0084] In one embodiment, the chip set 800 includes a communication
mechanism such as a bus 801 for passing information among the
components of the chip set 800. A processor 803 has connectivity to
the bus 801 to execute instructions and process information stored
in, for example, a memory 805. The processor 803 may include one or
more processing cores with each core configured to perform
independently. A multi-core processor enables multiprocessing
within a single physical package. Examples of a multi-core
processor include two, four, eight, or greater numbers of
processing cores. Alternatively or in addition, the processor 803
may include one or more microprocessors configured in tandem via
the bus 801 to enable independent execution of instructions,
pipelining, and multithreading. The processor 803 may also be
accompanied with one or more specialized components to perform
certain processing functions and tasks such as one or more digital
signal processors (DSP) 807, or one or more application-specific
integrated circuits (ASIC) 809. A DSP 807 typically is configured
to process real-world signals (e.g., sound) in real time
independently of the processor 803. Similarly, an ASIC 809 can be
configured to performed specialized functions not easily performed
by a general purposed processor. Other specialized components to
aid in performing the inventive functions described herein include
one or more field programmable gate arrays (FPGA) (not shown), one
or more controllers (not shown), or one or more other
special-purpose computer chips.
[0085] The processor 803 and accompanying components have
connectivity to the memory 805 via the bus 801. The memory 805
includes both dynamic memory (e.g., RAM, magnetic disk, writable
optical disk, etc.) and static memory (e.g., ROM, CD-ROM, etc.) for
storing executable instructions that when executed perform one or
more steps of a method described herein. The memory 805 also stores
the data associated with or generated by the execution of one or
more steps of the methods described herein.
[0086] While various embodiments of the present invention have been
shown and described herein, it will be obvious that such
embodiments are provided by way of example only. Numerous
variations, changes and substitutions may be made without departing
from the invention herein. Accordingly, it is intended that the
invention be limited only by the spirit and scope of the appended
claims.
[0087] Well-known structures and devices are shown in block diagram
form in order to avoid unnecessarily obscuring the present
invention. Throughout this specification and the claims, unless the
context requires otherwise, the word "comprise" and its variations,
such as "comprises" and "comprising," will be understood to imply
the inclusion of a stated item, element or step or group of items,
elements or steps but not the exclusion of any other item, element
or step or group of items, elements or steps. Furthermore, the
indefinite article "a" or "an" is meant to indicate one or more of
the item, element or step modified by the article.
[0088] Notwithstanding that the numerical ranges and parameters
setting forth the broad scope are approximations, the numerical
values set forth in specific non-limiting examples are reported as
precisely as possible. Any numerical value, however, inherently
contains certain errors necessarily resulting from the standard
deviation found in their respective testing measurements. Unless
otherwise clear from the context, a numerical value presented
herein has an implied precision given by the least significant
digit. Thus a value 1.1 implies a value from 1.05 to 1.15. The term
"about" is used to indicate a broader range centered on the given
value, and unless otherwise clear from the context implies a
broader range around the least significant digit, such as "about
1.1" implies a range from 1.0 to 1.2. If the least significant
digit is unclear, then the term "about" implies a factor of two,
e.g., "about X" implies a value in the range from 0.5.times. to
2.times., for example, about 100 implies a value in a range from 50
to 200. Moreover, all ranges disclosed herein are to be understood
to encompass any and all sub-ranges subsumed therein. For example,
a range of "less than 10" can include any and all sub-ranges
between (and including) the minimum value of zero and the maximum
value of 10, that is, any and all sub-ranges having a minimum value
of equal to or greater than zero and a maximum value of equal to or
less than 10, e.g., 1 to 4.
* * * * *