U.S. patent application number 11/999103 was filed with the patent office on 2009-06-04 for metering combustion control.
This patent application is currently assigned to PREFERRED UTILITIES MANUFACTURING CORPORATION. Invention is credited to Peter Lavelle.
Application Number | 20090142717 11/999103 |
Document ID | / |
Family ID | 40676095 |
Filed Date | 2009-06-04 |
United States Patent
Application |
20090142717 |
Kind Code |
A1 |
Lavelle; Peter |
June 4, 2009 |
Metering combustion control
Abstract
Metering combustion control in a fired equipment is disclosed in
which both the fuel flow rate and the combustion air flow rate are
metered in a desired ratio corresponding to a master firing rate
demand, and the master firing rate demand combustion air flow
directed to the combustion air regulating element is trimmed in
response to an error based correction adjustment determined from
the respective values of the fuel flow meter and combustion air
flow meter input signals to drive the ratio between the fuel flow
rate and the combustion air flow rate toward the desired ratio for
controlling the combustion in accordance with the master firing
rate demand.
Inventors: |
Lavelle; Peter; (Danbury,
CT) |
Correspondence
Address: |
WARE FRESSOLA VAN DER SLUYS & ADOLPHSON, LLP
BRADFORD GREEN, BUILDING 5, 755 MAIN STREET, P O BOX 224
MONROE
CT
06468
US
|
Assignee: |
PREFERRED UTILITIES MANUFACTURING
CORPORATION
|
Family ID: |
40676095 |
Appl. No.: |
11/999103 |
Filed: |
December 4, 2007 |
Current U.S.
Class: |
431/12 ; 431/89;
700/274 |
Current CPC
Class: |
F23N 2241/10 20200101;
F23N 1/022 20130101; F23N 2241/04 20200101; F23N 2223/36 20200101;
F23N 5/006 20130101 |
Class at
Publication: |
431/12 ; 431/89;
700/274 |
International
Class: |
F23N 1/02 20060101
F23N001/02 |
Claims
1. Method, comprising: controlling combustion in a fired equipment
according to a master firing rate demand; metering the fuel flow
rate and the combustion air flow rate in a desired ratio to
correspond to the master firing rate demand; providing an error
based correction adjustment based on the value of the fuel flow
meter input signal and the value of the combustion air flow meter
input signal, and trimming the master firing rate demand signal
value directed to the combustion air flow regulating element in
response to the error based correction adjustment to drive the
ratio between the fuel flow rate and the combustion air flow rate
toward the desired ratio for controlling the combustion in
accordance with the master firing rate demand.
2. The method according to claim 1 further comprising the fuel flow
input signal and the combustion air flow input signal being input
to a proportional integral derivative controller for determining
the value of the error based correction adjustment.
3. The method according to claim 1 further comprising limiting in
response to the failure of a fuel flow meter and/or an air
combustion flow meter, the value of the error correction based
adjustment to a predetermined allowable level to insure continued
combustion.
4. The method according to claim 1 further comprising providing a
turndown capability without dependence on flow meter flow
signals.
5. The method according to claim 4 wherein the turndown capability
is equivalent to a parallel positioning combustion control
operation.
6. The method according to claim 1 further comprising providing a
reduced response time capability without dependence on low
selectors, high selectors or differences in independent fuel and
air flow PID tunings.
7. The method according to claim 1 further comprising controlling
the fuel British Thermal Unit (BTU) flow rate and controlling the
combustion air oxygen mass flow rate.
8. The method according to claim 1 further comprising analyzing the
oxygen level in the flue gas for adjusting the combustion air flow
meter input signal.
9. The method according to claim 1 further comprising
characterizing the opening of the fuel flow regulating element to
produce a near linear fuel flow as a function of the trimmed master
firing rate demand signal directed to the fuel flow regulating
element.
10. The method according to claim 1 further comprising
characterizing the opening/speed of the air flow regulating element
to produce the desired fuel flow rate/combustion air flow rate
ratio as a function of the trimmed master firing rate demand signal
directed to the combustion air flow regulating element.
11. A controller, comprising: one or more modules configured for
controlling combustion in a fired equipment according to a master
firing rate demand; one or more modules configured for metering the
fuel flow rate and the combustion air flow rate in a desired ratio
to correspond to the master firing rate demand; one or more modules
configured for providing an error based correction adjustment based
on the value of the fuel flow meter input signal and the value of
the combustion air flow meter input signal, and one or more modules
configured for trimming the master firing rate demand signal value
directed to the combustion air flow regulating element in response
to the error based correction adjustment to drive the ratio between
the fuel flow rate and the combustion air flow rate toward the
desired ratio for controlling the combustion in accordance with the
master firing rate demand.
12. The controller according to claim 11 further comprising one or
more modules configured as a proportional integral derivative
controller for determining the value of the error based correction
adjustment based on the respective values of the fuel flow input
signal and the combustion air flow input signal.
13. The controller according to claim 11 wherein said fired
equipment is a boiler configured and arranged for generating
steam.
14. The controller according to claim 11 wherein said fired
equipment is a hot water heater.
15. The controller according to claim 11 wherein said fired
equipment is at least one of a steam generator, a boiler, a
chemical process heater, a heated manufacturing process, a boiler
combustion fired equipment.
16. A computer program product comprising a computer readable
structure embodying computer program code therein for execution by
a computer processor, said computer program further comprising
instructions for performing a method comprising controlling
combustion in a fired equipment according to a master firing rate
demand; metering the fuel flow rate and the combustion air flow
rate in a desired ratio to correspond to the master firing rate
demand; providing an error based correction adjustment based on the
value of the fuel flow meter input signal and the value of the
combustion air flow meter input signal, and trimming the master
firing rate demand signal value directed to the combustion air flow
regulating element in response to the error based correction
adjustment to drive the ratio between the fuel flow rate and the
combustion air flow rate toward the desired ratio for controlling
the combustion in accordance with the master firing rate
demand.
17. A method according to claim 1 wherein the method further
comprises implementing the steps of the method via a computer
program running in a processor, controller or other suitable module
located in or interfaced with the fired equipment.
18. A chipset, comprising: a first chipset module configured for
controlling combustion in a fired equipment by metering both the
fuel flow rate and the combustion air flow rate in a desired ratio
corresponding to a master firing rate demand, and a second chipset
module configured for trimming the master firing rate demand
directed to the combustion air regulating element in response to an
error based correction adjustment determined from the respective
values of the fuel flow meter and combustion air flow meter input
signals to drive the ratio between the fuel flow rate and the
combustion air flow rate toward the desired ratio for controlling
the combustion in accordance with the master firing rate
demand.
19. The chipset according to claim 18 further comprising a
proportional integral derivative controller configured for
determining the value of the error based correction adjustment
based on the respective values of the fuel flow input signal and
the combustion air flow input signal.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to combustion
control for use in fired equipment and deals more particularly with
a metering combustion control for fired equipment.
BACKGROUND OF THE INVENTION
[0002] Combustion control strategies applied to fired equipment,
both commercial and industrial, generally are one of three general
category types or some subtle variation to one or the other of
them. The control strategies as known to a person skilled in the
art are: 1) single point positioning control also known as
jackshaft positioning; 2) parallel positioning control; and 3)
metered cross-limited control.
[0003] Each of these are fuel/air ratio combustion control
strategies wherein a firing rate demand signal generated as a
result of an attempt to maintain a selected "process variable" (PV)
equal to a desired "set-point" (SP) is simultaneously directed to a
fuel flow regulating element and a combustion air flow regulating
element.
[0004] The currently known and implemented combustion control
strategies are not entirely satisfactory. To applicant's knowledge,
none of the known combustion control strategies meet Underwood
Laboratories (UL) approval as a parameter based combustion control
instrument capable of carrying out a metering fuel/air ratio
combustion control strategy.
[0005] The currently known and implemented metered cross-limited
combustion control strategies are not entirely satisfactory.
Current implementations utilize two, or more, PID
(Proportional-Integral-Derivative) control logic blocks, one for
fuel and one for air. Cross-limiting logic must be applied to
coordinate the two independent proportional integral derivative
logics. This combination requires considerable skill to tune and
calibrate, and results in a slow firing rate demand response
time.
[0006] Accordingly what is needed is a parameter based combustion
control instrument capable of choosing via parameter selection a
selected one of a single point positioning control strategy, a
parallel positioning control strategy and a metering fuel/air ratio
combustion control strategy.
SUMMARY OF THE INVENTION
[0007] In accordance with a broad aspect of some embodiments of the
invention, combustion is controlled in a fired equipment by
metering both the fuel flow rate and the combustion air flow rate
in a desired ratio corresponding to a master firing rate demand,
and by trimming the master firing rate demand directed to the
combustion air regulating element in response to an error based
correction adjustment determined from the respective values of the
fuel flow meter and combustion air flow meter input signals to
drive the ratio between the fuel flow rate and the combustion air
flow rate toward the desired ratio for controlling the combustion
in accordance with the master firing rate demand
BRIEF DESCRIPTION OF DRAWINGS
[0008] FIG. 1 is a function schematic representation of an example
of a parallel positioning combustion control system.
[0009] FIG. 2 is a functional schematic representation of an
example of a parallel positioning combustion control system with
oxygen trim.
[0010] FIG. 3 is a functional schematic representation of an
example of a full metering combustion control system with fuel flow
and combustion air flow cross limiting.
[0011] FIG. 4 is a functional schematic representation of an
example of a metering combustion control system with oxygen trim
according to some embodiments of the present invention.
[0012] FIG. 5 shows a flowchart of the basic steps of the method
according to some embodiments of the invention.
[0013] FIG. 6 shows a combustion controller enabled device
according to some embodiments of the invention for providing
combustion control in a fired equipment.
[0014] FIG. 7 is a functional block diagram of an example of a
signal processor for carrying out the invention.
[0015] FIG. 8 is a functional block diagram of an example of a
combustion controller for carrying out the steps of the method
according to some embodiments of the invention.
[0016] FIG. 9 shows a combustion controller chipset according to
some embodiments of the invention for providing combustion control
in a fired equipment.
WRITTEN DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION
[0017] The basic purpose and intent of a combustion control
strategy in a fired equipment is to maintain as stated above a
process variable equal to a desired set-point by directing a firing
rate demand signal to a fuel flow regulating element and a
combustion air flow regulating element in the fired equipment. Such
fired equipment may be for example, a steam generator, a hot water
heater, a boiler, a chemical process heater, a heated manufacturing
process, or other boiler combustion fired equipment although the
invention is not limited to such fired equipment. For purposes of
explanation and by way of example only, consider a steam generator.
In this case the process variable is the steam pressure. Under the
combustion control strategy, a reduction in the steam pressure
relative to the set-point of the desired pressure results in an
increase in the master firing rate demand signal with a
coincidental call for an increase in the fuel input and combustion
air input to the burner to increase the firing rate to produce more
steam to drive the pressure upward toward the desired pressure.
Likewise, an increase in the steam pressure relative to the
set-point results in a decrease in the master firing rate demand
signal with a coincidental call for a decrease in the fuel input
and combustion air input to decrease the firing rate to produce
less steam to drive the pressure downward toward the desired
pressure.
[0018] For further purposes of explanation and by way of a further
example, consider a hot water heater. In this case the process
variable is hot water temperature. Under the combustion control
strategy, a reduction in water temperature relative to the
set-point of the desired water temperature results in an increase
in the master firing rate demand signal with a coincidental call
for an increase in the fuel input and combustion air input to the
burner to increase the firing rate to produce hotter water to drive
the water temperature upward toward the desired water temperature.
Likewise, an increase in the water temperature relative to the
set-point results in a decrease in the master firing rate demand
signal with a coincidental call for a decrease in the fuel input
and combustion air input to decrease the firing rate to lessen the
heat input allowing the water temperature to decrease thus driving
the water temperature toward the desired water temperature.
[0019] In both examples, a reduction in the process variable
relative to the set-point results in an increase in the master
firing rate demand signal (MFDS) with a coincidental call for an
increase in fuel and combustion air inputs to the burner of the
fired equipment while an increase in the process variable relative
to the set-point results in a decrease in the MFDS and the fuel and
combustion air inputs.
[0020] FIG. 1 shows a schematic representation of a combustion
controller generally designated 10 in which a parallel positioning
control strategy is utilized. Two firing rate demand signals are
used in parallel positioning control, with one signal going to the
fuel flow regulating element and the other going to the combustion
air regulating element, hence the term parallel positioning. For
example, a reduction in the process variable relative to the
set-point results in an increase in the master firing rate demand
signal with a coincidental call for an increase in the fuel input
and combustion air input to the fired equipment, whereas an
increase in the process variable relative to the set-point results
in a decrease in the master firing rate demand signal and as a
result a decrease in the fuel input and the combustion air input.
As shown in FIG. 1, the master firing rate demand signals are
generated or retrieved from a suitably configured module 10a. The
generated output (0 to 100%) is the result of a comparison of the
design operating set-point versus the actual process state. The
fuel firing rate demand signal is conditioned by a fuel function
generator module 10b and directed to the fuel flow regulating
element 10c. The fuel function generator 10b characterizes the
opening of the fuel flow regulating element to produce a near
linear fuel flow as a function of the master firing rate demand
signal. The fuel flow regulating element 10c may be for example, a
flow control valve or a metering pump, and is responsive to the
fuel firing rate demand signal from the fuel function generator
module 10b to increase or decrease fuel flow. The combustion air
firing rate demand signal is conditioned by a combustion air
function generator 10d and directed to the air flow regulating
element 10e. The combustion air function generator 10d
characterizes the opening and/or speed of the air flow regulating
element 10e to produce the desired fuel/air ratio as a function of
the master firing rate demand signal. The fuel/air ratio is not a
constant and varies due to the need to maintain ideal fuel/air
mixing velocity ratios throughout the burner firing rate range. The
air flow regulating element 10e may be for example, a burner or
forced draft fan damper and/or a forced draft fan variable
frequency drive or a turbine.
[0021] Another combustion control strategy known as "single point
positioning" or "jackshaft positioning" control is a variation of
the parallel positioning control strategy in which the flow
regulating elements are of a design that is arranged to regulate
their respective flows via the action of one or more linkage rods,
each of which are connected to a common "jackshaft". That jackshaft
is in turn mechanically linked to a single positioning actuator or
servo-motor, which receives the master firing rate demand signal
input. In this way only one master firing rate demand signal is
directed to the fired equipment and the relative flow regulating
characteristics of each flow regulating element, i.e., the fuel
flow regulating element and the combustion air flow regulating
element, is accomplished by mechanical means, for example, linkage
adjustments, or adjustable cam/roller assemblies or both or in
other ways well known and understood by those skilled in the
art.
[0022] FIG. 2 shows a schematic representation of a combustion
controller generally designated 12 in which a parallel positioning
control strategy with oxygen trim is utilized. As explained in
connection with the discussion of FIG. 1, two firing rate demand
signals are used with the fuel firing rate demand signal going to
the fuel flow regulating element and the combustion air firing rate
demand signal being trimmed prior to going to the combustion air
regulating element. As shown in FIG. 2, the master firing rate
demand signals are generated or retrieved from a suitably
configured module 12a. The generated output (0 to 100%) is a result
of a comparison of the design operating set-point versus the actual
process state. The fuel firing rate demand signal is conditioned by
a fuel function generator module 12b and directed to the fuel flow
regulating element 12c. The fuel function generator 12b
characterizes the opening of the fuel flow regulating element to
produce a near linear fuel flow as a function of the master firing
rate demand signal. The fuel flow regulating element 12c may be for
example, a flow control valve or a metering pump, and is responsive
to the fuel firing rate demand signal from the fuel function
generator module 12b to increase or decrease fuel flow. A flue gas
oxygen analyzer module 12d determines the actual oxygen in the flue
gas. An air demand trim computer module 12e compares the actual
oxygen content in the flue gas to a master firing rate demand-based
flue gas excess oxygen set-point and adjusts either the master
firing rate demand combustion air flow signal input to the
controller or the master firing rate demand signal combustion air
flow signal directed to the air flow regulating element. Generally,
the oxygen trim computation will include limits on the amount of
variation that can be enacted to change the master firing rate
demand combustion air flow signal because of the concern for
possible failure of the flue gas oxygen analyzer. The master firing
rate demand combustion air flow signal is conditioned by a
combustion air function generator 12f and directed to the air flow
regulating element 12g. The combustion air function generator 12f
characterizes the opening and/or speed of the air flow regulating
element 12g to produce the desired fuel/air ratio as a function of
the master firing rate demand signal. The air flow regulating
element 12g may be for example, a burner or forced draft fan damper
and/or a forced draft fan variable frequency drive or a turbine.
The fuel/air ratio is not a constant and varies due to the need to
maintain ideal fuel/air mixing velocity ratios throughout the
burner firing rate range.
[0023] FIG. 3 shows a schematic representation of a combustion
controller generally designated 14 in which a full metering control
strategy with fuel flow and combustion air flow cross limiting is
utilized. In a traditional full metering combustion control system,
the values of the respective input of the actual fuel flow and the
combustion air flow are compared to their respective flow set-point
in a proportional integral derivative controller. The actual firing
rate demand signal for the fuel flow input and the combustion air
flow input is then the error correction based output signal from
the respective controller. The set-point of each of the fuel flow
controller and the combustion air flow controller was originally
the master firing rate demand signal. The traditional full metering
control strategy differs from the `basic` jackshaft and parallel
positioning control strategies (without oxygen trim) in that
neither of those strategies has any form of "feedback" pertaining
to the actual affect on flow rates resulting from a change in the
master firing rate demand signal. The addition of "cross limiting"
adds low and high signal selectors and logic to assure that on
increases in the firing rate, the air demand would increase before
the fuel demand and on decreases in firing rate, the reverse action
would be assured.
[0024] Still referring to FIG. 3, the master firing rate demand
signals are generated or retrieved from a suitably configured
module 14a. The generated output (0 to 100%) is a result of a
comparison of the design operating set-point versus the actual
process state. The fuel flow master firing rate demand signal is
input to a low value selector module 14d along with an actual
combustion air flow signal from a combustion air flow transmitter
module 14e to provide a fuel set-point signal that is input to the
fuel flow proportional integral derivative controller 14c along
with an actual value of the fuel flow signal from a fuel flow
transmitter module 14b to provide a fuel firing rate demand signal.
The fuel firing rate demand signal is conditioned by a fuel
function generator module 14f and is directed to the fuel flow
regulating element 14g. The fuel function generator 14f
characterizes the opening of the fuel flow regulating element to
produce a near linear fuel flow as a function of the master firing
rate demand signal. The fuel flow regulating element 14g may be for
example, a flow control valve or a metering pump, and is responsive
to the fuel firing rate demand signal from the fuel function
generator module 14f to increase or decrease fuel flow. The
combustion air flow master firing rate demand signal is input to a
high value selector module 14h along with an actual fuel flow
signal from the fuel flow transmitter module 14b to provide an air
flow set-point that is input to the air flow proportional integral
derivative controller 14i along with an actual combustion air flow
signal from the combustion air flow transmitter module 14e to
provide a combustion air firing rate demand signal. The combustion
air firing rate demand signal is conditioned by a combustion air
function generator 14j and directed to the air flow regulating
element 14k. The combustion air function generator 14j
characterizes the opening and/or speed of the air flow regulating
element 14k to produce the desired fuel/air ratio as a function of
the master firing rate demand signal. The air flow regulating
element 14k may be for example, a burner or forced draft fan damper
and/or a forced draft fan variable frequency drive or a turbine.
The fuel/air ratio is not a constant and varies due to the need to
maintain ideal fuel/air mixing velocity ratios throughout the
burner firing rate range.
[0025] Turning now to FIG. 4, a functional schematic representation
of an example of a metering combustion control system with oxygen
trim according to some embodiments of the present invention is
shown therein and generally designated 16. Now in contrast to the
combustion control system strategies discussed above, the metering
combustion control system strategy with oxygen trim embodying the
present invention blends the benefits of all of the above described
approaches by using the respective flow meter input signals in
combination with the master firing rate demand signals in a
proportional integral controller to "trim" the basic parallel
positioning master firing rate demand signal being directed to the
air flow regulating element. Further, limits are applied to the
allowable level of error correction based adjustment so that even
if there is a flow meter failure, continued operation in the basic
parallel positioning format (with or without oxygen trim) is
possible. Ideally the fuel input varies linearly with the master
firing rate demand whereas for reasons associated with maintaining
optimum mixing influenced velocities, the combustion air level is
relatively higher at lower firing rates (i.e. fuel/air ratio is not
a constant throughout the range).
[0026] As shown in FIG. 4, the master firing rate demand signals
are generated or retrieved from a suitably configured module 16a.
The generated output (0 to 100%) is a result of a comparison of the
design operating set-point versus the actual process state. The
firing rate demand signal is applied simultaneously to a fuel
function generator 16b and an air flow demand summing module 16k.
The fuel function generator 16b characterizes the opening of the
fuel flow regulating element 16c to produce a near linear fuel flow
as a function of the master firing rate demand signal. The air flow
demand summing module 16k adds the firing rate demand signal to the
air flow proportional integral derivative controller 16g trim
signal and applies the resultant signal to the combustion air
function generator 16i. The combustion air function generator 16i
characterizes the opening and/or speed of the air flow regulating
element 16j to produce the desired fuel/air ratio as a function of
the master firing rate demand signal. The fuel/air ratio is not a
constant and varies due to the need to maintain ideal fuel/air
mixing velocity ratios throughout the burner firing rate range.
[0027] The fuel flow regulating element 16c may be for example, a
flow control valve or a metering pump, and is responsive to the
fuel firing rate demand signal from the fuel function generator
module 16b to increase or decrease fuel flow. The air flow
regulating element 16j may be for example, a burner or forced draft
fan damper and/or a forced draft fan variable frequency drive or a
turbine.
[0028] A flue gas oxygen analyzer module 16d determines the actual
oxygen in the flue gas. An air flow trim computer module 16e
receives a signal representative of the value of the actual oxygen
in the flue gas along with a signal representative of the
combustion air flow from a combustion air flow transmitter module
16f to provide an adjusted combustion air flow signal in accordance
with the required oxygen content in the flue gas. The output signal
from the air flow trim computer module 16e is input to an air flow
proportional integral derivative controller module 16g along with
the value of the actual fuel flow from a fuel flow transmitter
module 16h for determining the combustion air flow trim signal to
be directed to the air flow demand summing module 16k.
[0029] It should be recognized that the turndown capability (i.e.
ability to operate at reduced rates) of a burner governed by a
traditional metering control strategy is tied to the flow meter's
limited turndown capabilities that is, flow measurement accuracy at
reduced rates. In contrast according to some embodiments of the
present invention, the turndown capabilities are equivalent to that
of parallel positioning due to the lack of the absolute dependence
on the fuel flow and combustion air flow signals.
[0030] It should be recognized that according to some embodiments
of the present invention, the fuel and air regulating elements (16c
and 16j) respond instantly to changes in the firing rate demand
16a. In contrast, traditional metered control strategy low selector
14d, high selector 14h and the differing response rates of fuel
proportional integral derivative controller 14c and air flow
proportional integral derivative controller 14i all combine to
delay the response of the respective fuel and air regulating
elements (16c and 16j) to a change in the firing rate demand
16a.
[0031] FIG. 5 shows a flowchart of the basic steps of the method
for metering combustion control in fired equipment according to
some embodiments of the present invention. The basic method is
shown in the flowchart generally designated 20 and includes the
steps of controlling combustion in a fired equipment, for example a
steam boiler or hot water heater by metering both the fuel flow
rate and the combustion air flow rate in a desired ratio
corresponding to a master firing rate demand (step 20a), and
trimming the master firing rate demand signal directed to the
combustion air regulating element in response to an error based
correction adjustment determined from the respective values of the
fuel flow meter and combustion air flow meter input signals to
drive the ratio between the fuel flow rate and the combustion air
flow rate toward the desired ratio for controlling the combustion
in accordance with the master firing rate demand (step 20b).
[0032] FIG. 6 shows by way of example a metering combustion control
enabled device 22 according to some embodiments of the invention
for use in a fired equipment 24 such as described above. The
metering combustion control enabled device 22 includes one or more
modules 22a configured for controlling combustion in a fired
equipment, for example a boiler or hot water heater, according to a
master firing rate demand, one or more modules 22b configured for
metering the fuel flow rate and the combustion air flow rate in a
desired ratio to correspond to the master firing rate demand, one
or more modules 22c configured for providing an error based
correction adjustment based on the value of the fuel flow meter
input signal and the value of the combustion air flow meter input
signal, and one or more modules 22d configured for trimming the
master firing rate demand signal value directed to the combustion
air flow regulating element in response to the error based
correction adjustment to drive the ratio between the fuel flow rate
and the combustion air flow rate toward the desired ratio for
controlling the combustion in accordance with the master firing
rate demand. Consistent with that described above, the metering
combustion control enabled device may include other modules 22e
that do not necessarily form part of the underlying invention and
are not described in detail herein.
[0033] By way of example, and consistent with that described above,
the functionality of the modules 22, 22a, 22b 22c, 22d and/or 22e
may be implemented using hardware, software, firmware, or a
combination thereof, although the scope of the invention is not
intended to be limited to any particular embodiment thereof. In a
typical software implementation, the modules 22a, 22b, 22c and 22d
would be one or more microprocessors-based architectures having a
microprocessor, a random access memory (RAM), a read only memory
(ROM), input/output devices, memory, flow meter control, and
control, data and address buses connecting the same such as shown
in FIG. 7. A person skilled in the art would be able to program
such a microprocessor-based implementation to perform the
functionality described herein without undue experimentation. The
scope of the invention is not intended to be limited to any
particular implementation using technology now known or later
developed in the future. Moreover, the scope of the invention is
intended to include the modules 22a, 22b, 22c and 22d being a
standalone module, as shown, or in the combination with other
circuitry for implementing another module. Moreover, the real-time
part may be implemented in hardware, while the non-real-time part
may be done in software.
[0034] According to some embodiments the present invention may be
implemented as a computer program product comprising a computer
readable structure embodying computer program code therein for
execution by a computer processor instructions for performing a
method comprising controlling combustion in a fired equipment
according to a master firing rate demand; metering the fuel flow
rate and the combustion air flow rate in a desired ratio to
correspond to the master firing rate demand; providing an error
based correction adjustment based on the value of the fuel flow
meter input signal and the value of the combustion air flow meter
input signal, and trimming the master firing rate demand signal
value directed to the combustion air flow regulating element in
response to the error based correction adjustment to drive the
ratio between the fuel flow rate and the combustion air flow rate
toward the desired ratio for controlling the combustion in
accordance with the master firing rate demand.
[0035] Turning now to FIG. 8, a schematic functional block diagram
of an example of a metering combustion control is illustrated
therein showing the major operational functional components which
may be required to carry out the intended functions of the
combustion controller and implement the steps of the method
according to some embodiments of the invention and is generally
designated 24. A processor such as the signal processor of FIG. 7
carries out the computational and operational control of the
metering combustion control in accordance with one or more sets of
instructions stored in a memory. A user interface may be used to
provide alphanumeric input and control signals or other program
steps and set-points by a user and is configured in accordance with
the intended function to be carried out. A display sends and
receives signals from the controller that controls the graphic and
text representations shown on a screen of the display in accordance
with the function being carried out. The controller controls a fuel
flow meter and an air combustion flow meter that operate in a
manner well known to those skilled in the art. The functional
logical elements for carrying out the metering combustion control
operational functions are suitably interconnected with the
controller to carry out the metering combustion control as
contemplated in accordance with some embodiments of the invention.
An electrical power source such as a battery is suitably
interconnected within the combustion controller to carry out the
functions described above. It will be recognized by those skilled
in the art that the metering combustion control according to some
embodiments of the invention may be implemented in other ways other
than that shown and described, including using pneumatic control
elements and other mechanical and electrical devices. It will also
be recognized by those skilled in the art that the metering
combustion control strategy for fired equipment according to some
embodiments of the invention can be implemented using other
suitably configured and arranged devices including but not limited
to pneumatic, electronic, microprocessor, computer, signal
processor, logic devices, wired logic, firmware, computational and
memory components, software instruction sets, and other devices and
components now known or future developed.
[0036] Consistent with that discussed above, the metering
combustion control according to some embodiments of the invention
may be implemented as a chipset for use in a combustion control
enabled fired equipment generally designated 26 for example as
illustrated in FIG. 9. The metering combustion control chipset
generally designated 26a is suitably configured for controlling
combustion in a fired equipment by metering both the fuel flow rate
and the combustion air flow rate in a desired ratio corresponding
to a master firing rate demand, and for trimming the master firing
rate demand directed to the combustion air regulating element in
response to an error based correction adjustment determined from
the respective values of the fuel flow meter and combustion air
flow meter input signals to drive the ratio between the fuel flow
rate and the combustion air flow rate toward the desired ratio for
controlling the combustion in accordance with the master firing
rate demand. Consistent with that described above, the metering
combustion control chipset may include other metering combustion
chipsets 26b that do not necessarily form part of the underlying
invention and are not described in detail herein.
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