Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM AND APPARATUS FOR APPLYING AN
ELECTRIC FIELD TO A COMBUSTION VOLUME
BACKGROUND
[001] An electric field may be applied to a flame. The flame may respond
by modifying its behavior, such as by increasing its rate of heat evolution.
SUMMARY
[002] According to an embodiment, a system may provide a plurality of
electric field axes configured to pass near or through a flame.
[003] According to an embodiment, a plurality greater than two electrodes
may selectively produce a plurality greater than two electric field axes
through or
near a flame. According to an embodiment, at least one of the selectable
electric
field axes may be at an angle and not parallel or antiparallel to at least one
other
of the selectable electric field axes.
[004] According to an embodiment, a controller may sequentially select an
electric field configuration in a combustion volume. A plurality greater than
two
electrode drivers may drive the sequential electric field configurations in
the
combustion volume. According to an embodiment, the controller may drive the
sequential electric field configurations at a periodic rate.
[005] According to an embodiment, a plurality of electric field modulation
states may be produced sequentially at a periodic frequency equal to or
greater
than about 120 Hz. According to an embodiment, a plurality of electric field
modulation states may be produced sequentially at a frequency of change equal
to or greater than about 1 KHz.
[006] According to an embodiment, a modulation frequency of electric field
states in a combustion volume may be varied as a function of a fuel delivery
rate,
an airflow rate, a desired energy output rate, or other desired operational
parameter.
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[007] According to an embodiment, an algorithm may be used to
determine one or more characteristics of one or more sequences of electric
field
modulation states. The algorithm may be a function of input variables and/or
detected variables. The input variables may include a fuel delivery rate, an
airflow
rate, a desired energy output rate, and/or another operational parameter.
[008] According to an embodiment, an electric field controller may include
a fuzzy logic circuit configured to determine a sequence of electric field
modulation states in a combustion volume as a function of input variables
and/or
detected variables. The input variables may include a fuel delivery rate, an
airflow
rate, a desired energy output rate, and/or another operational parameter.
[009] According to embodiments, related systems include but are not
limited to circuitry and/or programming for providing method embodiments.
Combinations of hardware, software, and/or firmware may be configured
according to the preferences of the system designer.
BRIEF DESCRIPTION OF THE DRAWINGS
[010] FIG. 1 is a diagram of a combustion volume configured for
application of a time-varying electric field, according to an embodiment.
[011] FIG. 2A is a depiction of an electric field in the combustion volume
corresponding to FIG. 1 at a first time, according to an embodiment.
[012] FIG. 2B is a depiction of an electric field in the combustion volume
corresponding to FIG. 1 at a second time, according to an embodiment.
[013] FIG. 2C is a depiction of an electric field in the combustion volume
corresponding to FIG. 1 at a third time, according to an embodiment.
[014] FIG. 3 is block diagram of a system configured to provide a time-
varying electric field across a combustion volume, according to an embodiment.
[015] FIG. 4 is block diagram of a system configured to provide a time-
varying electric field across a combustion volume, according to an embodiment.
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[016] FIG. 5 is a timing diagram for controlling electrode modulation,
according to an embodiment.
[017] FIG. 6 is a diagram illustrating waveforms for controlling electrode
modulation according to an embodiment.
[018] FIG. 7 is a diagram illustrating waveforms for controlling electrode
modulation according to an embodiment.
DETAILED DESCRIPTION
[019] In the following detailed description, reference is made to the
accompanying drawings, which form a part hereof. In the drawings, similar
symbols typically identify similar components, unless context dictates
otherwise.
The illustrative embodiments described in the detailed description, drawings,
and
claims are not meant to be limiting. Other embodiments may be used and/or and
other changes may be made without departing from the spirit or scope of the
disclosure.
[020] FIG. 1 is a diagram of a combustion volume 103 with a system 101
configured for application of a time-varying electric field to the combustion
volume
103, according to an embodiment. A burner nozzle 102 is configured to support
a
flame 104 in a combustion volume 103. For example, the combustion volume 103
may form a portion of a boiler, such as a water tube boiler or a fire tube
boiler, a
hot water tank, a furnace, an oven, a flue, an exhaust pipe, a cook top, or
the like.
[021] At least three electrodes 106, 108, and 110 are arranged near or in
the combustion volume 103 such that application of a voltage signals to the
electrodes may form an electric field across the combustion volume 103 in the
vicinity of or through the flame 104 supported therein by the burner nozzle
102.
The electrodes 106, 108, and 110 may be respectively energized by
corresponding leads 112, 114, and 116, which may receive voltage signals from
a
controller and/or amplifier (not shown).
[022] While the burner nozzle 102 is shown as a simplified hollow cylinder,
several alternative embodiments may be contemplated. While the burner 102 and
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the electrodes 106, 108, and 110 are shown in respective forms and geometric
relationships, other geometric relationships and forms may be contemplated.
For
example, the electrodes 106, 108, 110 may have shapes other than cylindrical.
According to some embodiments, the burner nozzle 102 may be energized to form
one of the electrodes. According to some embodiments, a plurality of nozzles
102
may support a plurality of flames104 in the combustion volume 103.
[023] According to an embodiment, a first plurality of electrodes 106, 108,
110 may support a second plurality of electric field axes across the
combustion
volume 103 in the vicinity of or through at least one flame. According to the
example 101, one electric field axis may be formed between electrodes 106 and
108. Another electric field axis may be formed between electrodes 108 and 110.
Another electric field axis may be formed between electrodes 106 and 110.
[024] The illustrative embodiment of FIG. 1 may vary considerably in
scale, according to the applications. For example, in a relatively small
system the
inner diameter of the burner 102 may be about a centimeter, and the distance
between electrodes 106, 108, 110 may be about 1.5 centimeters. In a somewhat
larger system, for example, the inner diameter of the burner 102 may be about
1.75 inches and the distance between the electrodes may be about 3.25 inches.
Other dimensions and ratios between burner size and electrode spacing are
contemplated.
[025] According to embodiments, an algorithm may provide a sequence of
voltages to the electrodes 106, 108, 110. The algorithm may provide a
substantially constant sequence of electric field states or may provide a
variable
sequence of electric field states, use a variable set of available electrodes,
etc.
While a range of algorithms are contemplated for providing a range of
sequences
of electric field states, a simple sequence of electric fields for the three
illustrative
electrodes 106, 108, 110 is shown in FIGS. 2A-2C.
[026] FIG. 2A is a depiction 202 of a nominal electric field 204 formed at
least momentarily at a first time between an electrode 106 and an electrode
108,
according to an embodiment. The electric field 204 is depicted such that
electrode 106 is held at a positive potential and electrode 108 is held at a
negative
potential, such that electrons and other negatively charges species in the
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combustion volume 103 tend to stream away from electrode 108 and toward
electrode 106. Similarly, positive ions and other positively charged species
in the
combustion volume 103 tend to stream away from electrode 106 and toward
electrode 108.
[027] A flame 104 in the combustion volume 103 may include a variety of
charged and uncharged species. For example, charged species that may
respond to an electric field may include electrons, protons, negatively
charged
ions, positively charged ions, negatively charged particulates, positively
charged
particulates, negatively charged fuel vapor, positively charged fuel vapor,
negatively charged combustion products, and positively charged combustion
products, etc. Such charged species may be present at various points and at
various times in a combustion process. Additionally, a combustion volume 103
and/or flame may include uncharged combustion products, unburned fuel, and
air.
The charged species typically present in flames generally make flames highly
conductive. Areas of the combustion volume 103 outside the flame 104 may be
relatively non-conductive. Hence, in the presence of a flame 104, the nominal
electric field 204 may be expressed as drawing negatively charged species
within
the flame 104 toward the volume of the flame proximate electrode 106, and as
drawing positive species within the flame 104 toward the volume of the flame
104
proximate electrode 108.
[028] Ignoring other effects, drawing positive species toward the
portion of
the flame 104 proximate electrode 108 may tend to increase the mass density of
the flame 104 near electrode 108. It is also known that applying an electric
field to
a flame may increase the rate and completeness of combustion.
[029] FIG. 2B is a depiction 206 of a nominal electric field 208 formed at
least momentarily at a second time between electrode 108 and electrode 110,
according to an embodiment. The electric field 208 is depicted such that
electrode 108 is held at a positive potential and electrode 110 is held at a
negative
potential, such that negatively charged species in the combustion volume 103
tend to stream away from electrode 110 and toward electrode 108; and positive
species in the combustion volume 103 tend to stream away from electrode 108
and toward electrode 110.
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[030] Similarly to the description of FIG. 2A, positive species in the
flame
104 in the combustion volume 103 may be drawn toward the volume of the flame
proximate electrode 110 and negatively charged species within the flame 204
may
be drawn toward the volume of the flame proximate electrode 108. This may tend
to increase the mass density of the flame 104 near electrodes 108 and/or 110.
[031] If the electric field configuration 206 of FIG. 2B is applied shortly
after application of the electric field configuration 202 of FIG. 2A, a
movement of
higher mass density positively charged species from the region of the flame
104
proximate electrode 108 to the region of the flame proximate electrode 110,
may
tend to cause a clockwise rotation of at least the positively charged species
within
the flame 104, along with an acceleration of combustion. If the relative
abundance, relative mass, and/or relative drift velocity of positive species
are
greater than that of negative species, then application of the electric field
configurations 202 and 206 in relatively quick succession may tend to cause a
net
rotation or swirl of the flame 104 in a clockwise direction. Alternatively, if
the
relative abundance, relative mass, and/or relative drift velocity of negative
species
are greater than that of positive species, then application of the electric
field
configurations 202 and 206 in relatively quick succession may tend to cause a
net
rotation or swirl of the flam 104 in a counter-clockwise direction.
[032] FIG. 2C is a depiction 210 of an electric field 212 formed at least
momentarily at a third time between electrode 110 and electrode 106, according
to an embodiment. The electric field 212 is depicted such that electrode 110
is
held at a positive potential and electrode 106 is held at a negative
potential. In
response, negatively charged species in the combustion volume 103 tend to
stream away from electrode 110 and toward electrode 108; and positive species
in the combustion volume 103 tend to stream away from electrode 108 and toward
electrode 110.
[033] Similarly to the description of FIGS. 2A and 2B, positive
species in
the flame 104 in the combustion volume 103 may be drawn toward the volume of
the flame proximate electrode 106 and negatively charged species within the
flame 204 may be drawn toward the volume of the flame proximate electrode 110.
This may tend to increase the mass density of the flame 104 near electrode 106
and/or electrode 110, depending on the relative abundance, mass, and drift
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velocity of positively and negatively charged species. If the electric field
configuration 210 of FIG. 2C is applied shortly after application of the
electric field
configuration 206 of FIG. 2B, a movement of higher mass density from the
region
of the flame 104 proximate electrode 110 to the region of the flame proximate
electrode 106 may tend to cause a clockwise rotation of positive species and
counter-clockwise rotation of negative species in the flame 104, along with an
acceleration of combustion. Depending on the relative mass, relative
abundance,
and relative drift velocities of the positive and negative species, this may
tend to
cause a clockwise or counter-clockwise swirl.
[034] According to an embodiment, for example when a field-reactive
movement of species is dominated by positively charged species, a sequential,
repeating application of nominal electric fields 204, 208, 212 may tend to
accelerate the flame 104 to produce a clockwise swirl or vortex effect in the
flame.
Such a sequential electric field application may further tend to expose
reactants to
a streaming flow of complementary reactants and increase the probability of
collisions between reactants to reduce diffusion related limitations to
reaction
kinetics. Decreased diffusion limitations may tend to increase the rate of
reaction,
further increasing exothermic output, thus further increasing the rate of
reaction.
The higher temperature and higher reaction rate may tend to drive the flame
reaction farther to completion to increase the relative proportion of carbon
dioxide
(CO2) to other partial reaction products such as carbon monoxide (CO),
unburned
fuel, etc. exiting the combustion volume 103. The greater final extent of
reaction
may thus provide higher thermal output and/or reduce fuel consumption for a
given thermal output.
[035] According to another embodiment, a sequential repeating
application of nominal electric fields 204, 208, 212 may tend to accelerate
the
flame 104 to produce a counter-clockwise swirl or vortex effect in the flame,
for
example when a field-reactive movement of species is dominated by negatively
charged species.
[036] While the electrode configuration and electric field sequence shown
in FIGS 1 and 2A-2C is shown as an embodiment using a relatively simple
configuration of three electrodes 106, 108, 110 and three electric field axes
204,
208, 212, other configurations may be preferable for some embodiments and
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some applications. For example an electric field may exist simultaneously
between more than two electrodes. The number of electrodes may be increased
significantly. The timing of electric field switching may be changed, may be
made
at a non-constant interval, may be made to variable potentials, may be
informed
by feedback control, etc. The electrode configuration may be altered
significantly,
such as by integration into the combustion chamber wall, placement behind the
combustion chamber wall, etc. Furthermore, electrodes may be placed such that
the electric field angle varies in more than one plane, such as by placing
some
electrodes proximal and other electrodes distal relative to the burner nozzle.
In
other embodiments, a given electrode may be limited to one state (such as
either
positive or negative) plus neutral. In other embodiments, all electrodes may
be
limited to one state (such as either positive or negative) plus neutral.
[037] FIG. 3 is block diagram of a system 301 configured to provide a
time-varying electric field across a combustion volume, according to an
embodiment. An electronic controller 302 is configured to produce a plurality
of
time-varying waveforms for driving a plurality of electrodes 106, 108 and 110.
The
waveforms may be formed at least partly by a sequencer (not shown) forming a
portion of the controller 302. The sequencer may be formed from a software
algorithm, a state machine, etc., operatively coupled to an output node 306.
The
waveforms are transmitted to an amplifier 304 via one or more signal lines
306.
The amplifier 304 amplifies the waveforms to respective voltages for
energizing
the electrodes 106, 108, and 110 via the respective electrode leads 112, 114,
and
116.
[038] According to an embodiment, the waveforms may be produced by
the controller 302 at a constant frequency. According to embodiments, the
constant frequency may be fixed or selectable. According to another
embodiment, the waveforms by be produced at a non-constant frequency. For
example, a non-constant period or segment of a period may help to provide a
spread-spectrum field sequence and may help to avoid resonance conditions or
other interference problems.
[039] According to an illustrative embodiment, electrode drive waveforms
may be produced at about 1 KHz. According to another embodiment, electrode
drive waveforms may be produced with a period corresponding to about 10 KHz.
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According to another embodiment, electrode drive waveforms may be produced at
about 20 KHz. According to an illustrative embodiment, the amplifier 304 may
drive the electrodes 106, 108, and 110 to about 900 volts. According to
another
embodiment, the amplifier 304 may drive the electrodes 106, 108, 110 to about
+450 and -450 volts. As mentioned elsewhere, portions of a period may include
opening a circuit to one or more electrodes 106, 108, 110 to let its voltage
"float".
[040] According to some embodiments, it may be desirable to set or vary
the electric field frequency and/or the voltage of the electrodes 106, 108,
110,
and/or to provide sensor feedback such as a safety interlock or measurements
of
flame-related, electric field-related, or other parameters. FIG. 4 is block
diagram
of a system 401 configured to receive or transmit at least one combustion or
electric field parameter and/or at least one sensor input. The system 401 may
responsively provide a time-varying electric field between electrodes 106,
108,
110 across a combustion volume as a function of the at least one combustion
parameter and/or at least one sensor input, according to another embodiment.
For example, the modulation frequency of the electric field states and/or the
electrode voltage may be varied as a function of a fuel delivery rate, a
desired
energy output rate, or other desired operational parameter.
[041] The controller 302 may be operatively coupled to one or more of a
parameter communication module 402 and a sensor input module 404, such as
via a data communication bus 406. The parameter communication module 402
may provide a facility to update software, firmware, etc used by the
controller 302.
Such updates may include look-up table and/or algorithm updates such as may be
determined by modeling, learned via previous system measurements, etc. The
parameter communication module 402 may further be used to communicate
substantially real time operating parameters to the controller 302. The
parameter
communication module 402 may further be used to communicate operating status,
fault conditions, firmware or software version, sensor values, etc. from the
controller 302 to external systems (not shown).
[042] A sensor input module 404 may provide sensed values to the
controller 302 via the data communication bus 406. Sensed values received from
the sensor input module 404 may include parameters not sensed by external
systems and therefore unavailable via the parameter communication module 402.
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Alternatively, sensed values received from the sensor input module 404 may
include parameters that are also reported from external systems via the
parameter
communication module 402.
[043] Parameters such as a fuel flow rate, stack gas temperature, stack
gas optical density, combustion volume temperature, combustion volume
luminosity, combustion volume ionization, ionization near one or more
electrodes,
combustion volume open, combustion volume maintenance lockout, electrical
fault, etc. may be communicated to the controller 302 from the parameter
communication module 402, sensor input module 404, and/or via feedback
through the amplifier 304.
[044] Voltage drive to the electrodes 106, 108, 110 may be shut off in the
event of a safety condition state and/or a manual shut-down command received
through the parameter communication module 402. Similarly, a fault state in
the
system 401 may be communicated to an external system to force a shutdown of
fuel or otherwise enter a safe state.
[045] The controller may determine waveforms for driving the electrodes
106, 108, 110 responsive to the received parameters, feedback, and sensed
values (referred to collectively as "parameters"). For example the parameters
may be optionally combined, compared, differentiated, integrated, etc.
Parameters or combinations of parameters may be input to a control algorithm
such as an algorithmic calculation, a table look-up, a proportional-integral-
differential (PID) control algorithm, fuzzy logic, or other mechanisms to
determine
waveform parameters. The determined waveform parameters may include, for
example, selection of electrodes 106, 108, 110, sequencing of electrodes 106,
108, 110, waveform frequency or period, electrode 106, 108, 110 voltage, etc.
[046] The parameters may be determined, for example, according to
optimization of a response variable such for maximizing thermal output from
the
combustion volume, maximizing an extent of reaction in the combustion volume,
maximizing stack clarity from the combustion volume, minimizing pollutant
output
from the combustion volume, maximizing the temperature of the combustion
volume, meeting a target temperature in the combustion volume, minimizing
luminous output from a flame in the combustion volume, achieving a desired
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flicker in a flame in the combustion volume, maximizing luminous output from a
flame in the combustion volume, maximizing fuel efficiency, maximizing power
output, compensating for maintenance issues, maximizing system life,
compensating for fuel variations, compensating for a fuel source, etc.
[047] According to an embodiment, waveforms generated by the controller
302 may be transmitted to the amplifier 304 via one or more dedicated waveform
transmission nodes 306. Alternatively, waveforms may be transmitted via the
data bus 406. The amplifier 304 may provide status, synchronization, fault or
other feedback via dedicated nodes 306 or may alternatively communicate status
to the controller 302 and/or the parameter communication module 402 via the
data
bus 406.
[048] While the controller 302 and amplifier 304 of FIGS. 3 and 4 are
illustrated as discrete modules, they may be integrated. Similarly, the
parameter
communications module 402 and/or sensor input module 404 may be integrated
with the controller 302 and/or amplifier 304.
[049] An illustrative set of waveforms is shown in FIG. 5, in the form of a
timing diagram 501 showing waveforms 502, 504, 506 for respectively
controlling
electrode 106, 108, 110 modulation, according to an embodiment. Each of the
waveforms 502, 504, and 506 are shown registered with one another along a
horizontal axis indicative of time, each shown as varying between a high
voltage,
VH, a ground state, 0, and a low voltage VL. According to an embodiment, the
waveforms 502, 504, 506 correspond respectively to energization patterns
delivered to the electrodes 106, 108 and 110.
[050] The voltages VH, 0, and VL may represent relatively low voltages
delivered to the amplifier 304 from the controller 302 via the amplifier drive
line(s)
306. Similarly, the voltages VH, 0, and VL may represent relatively large
voltages
delivered by the amplifier 304 to the respective electrodes 106, 108, 110 via
the
respective electrode drive lines 112, 114, 116. The waveforms 502, 504, 506
may
be provided to repeat in a periodic pattern with a period P. During a first
portion
508 of the period P, waveform 502 drives electrode 106 high while waveform 504
drives electrode 108 low, and waveform 506 drives electrode 110 to an
intermediate voltage. Alternatively, portion 508 of waveform 506 (and
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corresponding intermediate states in the other waveforms 502, 504) may
represent opening the electrode drive such that the electrode electrical
potential
floats.
[051] Waveform portion 508 corresponds to the electric field state
202
shown in FIG. 2A. That is VH is applied to electrode 106 while VL is applied
to
electrode 108 to form an idealized electric field 204 between electrodes 106
and
108. Electrode 110 is either allowed to float or held at an intermediate
potential
such that reduced or substantially no electric fields are generated between it
and
the other electrodes.
[052] During a second portion 510 of the period P, waveform 502 indicates
that electrode 106 is held open to "float" or alternatively is driven to an
intermediate voltage, while waveform 504 drives electrode 108 high to VH and
waveform 506 drives electrode 110 to a low voltage VL. Waveform portion 510
corresponds to the electric field state 206 shown in FIG. 2B. That is, VH is
applied
to electrode 108 while VL is applied to electrode 110 to form an idealized
electric
field 208 between electrodes 108 and 110. Electrode 106 is either allowed to
float
or held at an intermediate potential such that reduced or substantially no
electric
fields are generated between it and the other electrodes.
[053] During a third portion 512 of the period P, waveform 504 indicates
that electrode 108 is held open to "float" or alternatively is driven to an
intermediate voltage, while waveform 506 drives electrode 110 high to VH and
waveform 502 drives electrode 106 to a low voltage VL. Waveform portion 512
corresponds to the electric field state 210 shown in FIG. 2B. That is, VH is
applied
to electrode 110 while VL is applied to electrode 106 to form an idealized
electric
field 212 between electrodes 110 and 106. Electrode 108 is either allowed to
float
or held at an intermediate potential such that reduced or substantially no
electric
fields are generated between it and the other electrodes. Proceeding to the
next
portion 508, the periodic pattern is repeated.
[054] While the waveforms 502, 504, and 506 of timing diagram 501
indicate that each of the portions 508, 510, and 512 of the period P are
substantially equal in duration, the periods may be varied somewhat or
modulated
such as to reduce resonance behavior, accommodate variations in combustion
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volume 103 geometry, etc. Additionally or alternatively, the periods P may be
varied in duration. Similarly, while the voltage levels VH, 0, and VL are
shown as
substantially equal to one another, they may also be varied from electrode-to-
electrode, from period portion to period portion, and/or from period-to-
period.
[055] Returning to the waveforms 501 of FIG. 5, it may be seen that at a
first point in time during the period portion 508, there is a potential
difference and
a corresponding electric field between an electrode corresponding to the
waveform 502 and an electrode corresponding to the waveform 504. This is
because the waveform 502 has driven a corresponding electrode to a relatively
high potential and the waveform 504 has driven a corresponding electrode to a
relatively low potential. Simultaneously, there is a reduced or substantially
no
electric field formed between an electrode corresponding to waveform 502 and
an
electrode corresponding to waveform 506, because waveform 506 has driven the
potential of the corresponding electrode to an intermediate potential or has
opened the circuit to let the electrode float. Similarly, at a second time
corresponding to period portion 512, there is a potential difference and
corresponding electric field between an electrode corresponding to the
waveform
502 and an electrode corresponding to the waveform 506, but a reduced or
substantially no potential difference or electric field between an electrode
corresponding to the waveform 502 and an electrode corresponding to the
waveform 504.
[056] While the waveforms 502, 504, and 506 are shown as idealized
square waves, the shape of the waveforms 502, 504, 506 may be varied. For
example, leading and trailing edges may exhibit voltage overshoot or
undershoot;
leading and trailing edges may be transitioned less abruptly, such as by
applying
a substantially constant dl/dt circuit, optionally with acceleration; or the
waveforms
may be modified in other ways, such as by applying sine functions, etc.
[057] FIG. 6 is a diagram 601 illustrating waveforms 602, 604, 606 for
controlling electrode modulation according to another embodiment. The
waveforms 602, 604, and 606 may, for example, be created from the
corresponding waveforms 502, 504, 506 of FIG. 5 by driving the square
waveforms through an R/C filter, such as driving through natural impedance.
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Alternatively, the waveforms 602, 604, and 606, may be digitally synthesized,
driven by a harmonic sine-function generator, etc.
[058] While the period portions 508, 510, and 512 may or may not
correspond exactly to the corresponding portions of FIG. 5, they may be
generally
regarded as driving the electrodes 106, 108, and 110 to corresponding states
as
shown in FIGS 2A-2C. The period P may be conveniently determined from a zero
crossing as shown, or may be calculated to correspond to the position shown in
FIG. 5.
[059] As may be appreciated, when waveforms such as 602, 604, 606
drive corresponding electrodes 106, 108, 110; the idealized electric fields
204,
208, 212 of FIGS. 2A-2C may not represent the actual fields as closely as when
waveforms such as 502, 504, 506 of FIG. 5 are used. For example, at the
beginning of period portion 508 waveform 602 ramps up from an intermediate
voltage, 0 to a high voltage VH while waveform 604 ramps down from an
intermediate voltage, 0 to a low voltage VL and waveform 606 ramps down from a
high voltage VH toward an intermediate voltage 0. Thus, the electric field 212
of
FIG. 2C "fades" to the electric field 204 of FIG. 2A during the beginning of
period
portion 508. During the end of period portion 508, waveform 604 ramps up
toward
high voltage while waveform 606 continues to decrease and waveform 602 begins
its descent from its maximum value. This may tend to fade electric field 204
toward the configuration 206, while a small reversed sign field 212 appears,
owing
to the potential between electrodes 106 and 110.
[060] Returning to the waveforms 601 of FIG. 6, it may be seen that at a
first point in time 608, there is a potential difference and a corresponding
electric
field between an electrode corresponding to the waveform 602 and an electrode
corresponding to the waveform 604. This is because the waveform 602 has
driven a corresponding electrode to a relatively high potential and the
waveform
604 has driven a corresponding electrode to a relatively low potential.
Simultaneously, there is substantially no electric field formed between an
electrode corresponding to waveform 602 and an electrode corresponding to
waveform 606 because waveforms 602 and 606 are momentarily at the same
potential. Similarly, at a second point in time 610, there is a potential
difference
and corresponding electric field between an electrode corresponding to the
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waveform 602 and an electrode corresponding to the waveform 606, but no
potential difference or electric field between an electrode corresponding to
the
waveform 602 and an electrode corresponding to the waveform 604.
[061] FIG. 7 is a diagram 701 illustrating waveforms 702, 704, 706 for
controlling modulation of the respective electrodes 106, 108, 110 according to
another embodiment. Waveform 702 begins a period P during a portion 708 at a
relatively high voltage VH, corresponding to a relatively high voltage at
electrode
106. Also during the portion 708, waveform 704 begins the period Pat a
relatively
low voltage VL, corresponding to a relatively low voltage at electrode 108;
and
waveform 706 corresponds to an open condition at electrode 110. Waveform
portion 708 may be referred to as a first pulse period.
[062] During the first pulse period 708, the electric field configuration
in a
driven combustion volume 103 may correspond to configuration 202, shown in
FIG. 2A. As was described earlier, the nominal electric field 204 of
configuration
202 may tend to attract positively charged species toward electrode 108 and
attract negatively charged species toward electrode 106.
[063] After the first pulse period 708, waveforms 702 and 704 drive
respective electrodes 106 and 108 open while waveform 706 maintains the open
circuit condition at electrode 110. During a portion 710 of the period P, the
electrodes 106, 108, and 110 are held open and thus substantially no electric
field
is applied to the flame or the combustion volume. However, inertia imparted
onto
charged species during the preceding first pulse period 708 may remain during
the non-pulse period 710, and the charged species may thus remain in motion.
Such motion may be nominally along trajectories present at the end of the
first
pulse period 708, as modified by subsequent collisions and interactions with
other
particles.
[064] At the conclusion of the first non-pulse portion 710 of the period P,
a
second pulse period 712 begins. During the second pulse period 712, waveform
702 provides an open electrical condition at electrode 106 while waveform 704
goes to a relatively high voltage to drive electrode 108 to a corresponding
relatively high voltage and waveform 706 goes to a relatively low voltage to
drive
electrode 110 to a corresponding relatively low voltage. Thus during the
second
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pulse period 712, an electric field configuration 206 of FIG. 2B occurs. This
is
again followed by a non-pulse portion of the waveforms 710, during which
inertia
effects may tend to maintain the speed and trajectory of charged species
present
at the end of the second pulse period 712, as modified by subsequent
collisions
and interactions with other particles.
[065] At the conclusion of the second non-pulse portion 710, a third pulse
period 714 begins, which may for example create an electric field
configuration
similar to electric field configuration 210, shown in FIG. 2C. After the third
pulse
period 714 ends, the system may again enter a non-pulse portion 710. This may
continue over a plurality of periods, such as to provide a pseudo-steady state
repetition of the period P portions 708, 710, 712, 710, 714, 710, etc.
[066] According to one embodiment, the pulse periods and non-pulse
portions may provide about a 25% duty cycle pulse train, as illustrated,
wherein
there is a field generated between two electrodes about 25% of the time and no
applied electric fields the other 75% of the time. The duty cycle may be
varied
according to conditions within the combustion volume 103, such as may be
determined by a feedback circuit and/or parameter input circuit as shown in
FIGS.
3 and 4.
[067] According to another embodiment, the pulse periods 708, 712, and
714 may each be about 10 microseconds duration and the period P may be about
1 KHz frequency, equivalent to 1 millisecond period. Thus, the non-pulse
portions
may each be about 323.333 microseconds.
[068] The relative charge-to-mass ratio of a particular charged species
may affect its response to the intermittent pulse periods 708, 712, 714 and
intervening non-pulse portions 710. The duty cycle may be varied to achieve a
desired movement of one or more charged species in the combustion volume 103.
According to an embodiment, waveforms 702, 704, 706 optimized to transport a
positively charged species clockwise may be superimposed over other waveforms
(not shown) optimized to transport another positively charged species or a
negatively charged species clockwise or counterclockwise to produce a third
set
of waveforms (not shown) that achieve transport of differing species in
desired
respective paths.
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[069] For example, a heavy, positive species may require a relatively high,
50% duty cycle with a relatively long period to move along a chosen path. A
light,
negative species may require a relatively low duty cycle with a relatively
short
period to move along a chosen path. The two waveforms may be superimposed
to drive the positive and negative species in parallel (clockwise or counter-
clockwise) or anti-parallel (clockwise and counter-clockwise) to each other.
[070] While the electrodes 106, 108, 110 are shown arranged in figures
above such that a straight line connecting any two electrodes passes through
the
volume of an intervening flame, other arrangements may be within the scope.
While the number of electrodes 106, 108, 110 shown in the embodiments above is
three, other numbers greater than three may similarly fall within the scope.
While
the electrodes 106, 108, 110 are indicated as cylindrical conductors arranged
parallel to the major axis of the burner nozzle, other arrangements may fall
within
the scope.
[071] For example, in another embodiment, a plurality of electrodes are
arranged substantially at the corners of a cube, and include plates of finite
size
having normal axes that intersect at the center of the cube, which corresponds
to
the supported flame 104. In other embodiments (not shown) the electrodes may
include surfaces or figurative points arranged at the centers of the faces of
a cube,
at the corners or at the centers of the faces of a geodesic sphere, etc.
[072] Those skilled in the art will appreciate that the foregoing specific
exemplary processes and/or devices and/or technologies are representative of
more general processes and/or devices and/or technologies taught elsewhere
herein, such as in the claims filed herewith and/or elsewhere in the present
application.
[073] While various aspects and embodiments have been disclosed
herein, other aspects and embodiments are contemplated. The various aspects
and embodiments disclosed herein are for purposes of illustration and are not
intended to be limiting, with the true scope and spirit being indicated by the
following claims.
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