Abstract:
According to an embodiment, combustion in a combustion volume is affected by at least two sequentially applied non-parallel electric fields. According to an embodiment, a combustion volume is equipped with at least three individually modulatable electrodes. According to an embodiment, an electric field application apparatus for a combustion volume includes a safety apparatus to reduce or eliminate danger.

Description:
BACKGROUND 
       [0001]    A time-varying 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. 
       OVERVIEW 
       [0002]    According to an embodiment, a system may provide a plurality of electric field axes configured to pass near or through a flame. 
         [0003]    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 not parallel or antiparallel with at least one other of the selectable electric field axes. 
         [0004]    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. 
         [0005]    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. 
         [0006]    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. 
         [0007]    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. 
         [0008]    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. 
         [0009]    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 
         [0010]      FIG. 1  is a diagram of a combustion volume configured for application of a time-varying electric field vector, according to an embodiment. 
           [0011]      FIG. 2A  is a depiction of an electric field vector in the combustion volume corresponding to  FIG. 1  at a first time, according to an embodiment. 
           [0012]      FIG. 2B  is a depiction of an electric field vector in the combustion volume corresponding to  FIG. 1  at a second time, according to an embodiment. 
           [0013]      FIG. 2C  is a depiction of an electric field vector in the combustion volume corresponding to  FIG. 1  at a third time, according to an embodiment. 
           [0014]      FIG. 3  is block diagram of a system configured to provide a time-varying electric field across a combustion volume, according to an embodiment. 
           [0015]      FIG. 4  is block diagram of a system configured to provide a time-varying electric field across a combustion volume, according to an embodiment. 
           [0016]      FIG. 5  is a timing diagram for controlling electrode modulation, according to an embodiment. 
           [0017]      FIG. 6  is a diagram illustrating waveforms for controlling electrode modulation according to an embodiment. 
           [0018]      FIG. 7  is a diagram illustrating waveforms for controlling electrode modulation according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    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. Other embodiments may be used and/or and other changes may be made without departing from the spirit or scope of the disclosure. 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 utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. 
         [0020]      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, a water tube boiler, a fire tube boiler, a hot water tank, a furnace, an oven, a flue, an exhaust pipe, a cook top, or the like. 
         [0021]    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). 
         [0022]    While the burner nozzle  102  is shown as a simplified hollow cylinder, several alternative embodiments may be contemplated. While the burner  102  and 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 may support a plurality of flames in the combustion volume  103 . 
         [0023]    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 . 
         [0024]    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. 
         [0025]    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 algorithm for the three illustrative electrodes  106 ,  108 ,  110  is shown in  FIGS. 2A-2C . 
         [0026]      FIG. 2A  is a depiction  202  of a nominal electric field  204  formed at least momentarily at a first time from electrode  106  to electrode  108 , according to an embodiment. If 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, then electrons and other negatively charges species in the 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 . 
         [0027]    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 . 
         [0028]    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. 
         [0029]      FIG. 2B  is a depiction  206  of a nominal electric field  208  formed at least momentarily at a second time from electrode  108  to electrode  110 , according to an embodiment. If 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, then 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 . 
         [0030]    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 . 
         [0031]    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 of 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. 
         [0032]      FIG. 2C  is a depiction  210  of an electric field  212  formed at least momentarily at a third time from electrode  110  to electrode  106 , according to an embodiment. If 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, then 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 . 
         [0033]    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  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 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. 
         [0034]    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-limitations to reaction kinetics. Decreased diffusion limitation 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 (CO 2 ) 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. 
         [0035]    According to another embodiment, the 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. 
         [0036]    While the electrode configuration and electric field sequence shown in FIGS.  1  and  2 A- 2 C is shown as an embodiment using a relatively simple configuration of three electrodes and three field axes, other configurations may be preferable for some embodiments and 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. 
         [0037]      FIG. 3  is block diagram of a system  301  configured to provide a time-varying electric field across a combustion volume  103 , 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 the output node  306 . The waveforms are transmitted to an amplifier  304  via one or more signal lines  306 . The amplifier amplifies the waveforms to respective voltages for energizing the electrodes  106 ,  108 , and  110  via the respective electrode leads  112 ,  114 , and  116 . 
         [0038]    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. 
         [0039]    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. 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 to let its voltage “float”. 
         [0040]    According to some embodiments, it may be desirable to set or vary the electric field frequency and/or the voltage of the electrodes, and/or to provide sense 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 across a combustion volume  103  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. 
         [0041]    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). 
         [0042]    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 . 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 . 
         [0043]    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 input module  402 , sensor input module  404 , and/or via feedback through the amplifier  304 . 
         [0044]    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 input. 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. 
         [0045]    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 mechanism to determine waveform parameters. The determined waveform parameters may include, for example, selection of electrodes, sequencing of electrodes, waveform frequency or period, electrode voltage, etc. 
         [0046]    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 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. 
         [0047]    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 . 
         [0048]    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 . 
         [0049]    An illustrative set of waveforms is shown in  FIG. 5 , which may form a timing diagram  501  showing waveforms  502 ,  504 ,  506  for controlling electrode 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, V H , a ground state,  0 , and a low voltage V L . According to an embodiment, the waveforms  502 ,  504 ,  506  correspond respectively to energization patterns delivered to the electrodes  106 ,  108  and  110 . 
         [0050]    The voltages V H ,  0 , and V L  may represent relatively low voltages delivered to the amplifier  304  from the controller  302  via the amplifier drive line(s)  306 . Similarly, the voltages V H ,  0 , and V L  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 corresponding intermediate states in the other waveforms  502 ,  504 ) may represent opening the electrode drive such that the electrode floats. 
         [0051]    Waveform portion  508  corresponds to the electric field state  202  shown in  FIG. 2A . That is V H  is applied to electrode  106  while V L  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. 
         [0052]    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,  0  while waveform  504  drives electrode  108  high to V H  and waveform  506  drives electrode  110  to a low voltage V L . Waveform portion  510  corresponds to the electric field state  206  shown in  FIG. 2B . That is, V H  is applied to electrode  108  while V L  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. 
         [0053]    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,  0  while waveform  506  drives electrode  110  high to V H  and waveform  502  drives electrode  106  to a low voltage V L . Waveform portion  512  corresponds to the electric field state  210  shown in  FIG. 2B . That is, V H  is applied to electrode  110  while V L  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. 
         [0054]    While the waveforms  502 ,  504 , and  506  of timing diagram  501  indicates 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 volume  103  geometry, etc. Additionally or alternatively, the periods P may be varied in duration. Similarly, while the voltage levels V H ,  0 , and V L  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. 
         [0055]    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 . 
         [0056]    While the waveforms  502 ,  504 , and  506  are shown as idealizes square waves, their shape 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. 
         [0057]      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. Alternatively, the waveforms  602 ,  604 , and  606 , may be digitally synthesized, driven by a harmonic sine-function generator, etc. 
         [0058]    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 a position corresponding to the position shown in  FIG. 5 . 
         [0059]    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 V H  while waveform  604  ramps down from an intermediate voltage,  0  to a low voltage V L  and waveform  606  ramps down from a high voltage V H  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 , as are small reversed sign field  212  appears, owing to the potential between electrodes  106  and  110 . 
         [0060]    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 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 . 
         [0061]      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 V H , corresponding to a relatively high voltage at electrode  106 . Also during the portion  708 , waveform  704  begins the period P at a relatively low voltage V L , 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. 
         [0062]    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 . 
         [0063]    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. 
         [0064]    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 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. 
         [0065]    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. 
         [0066]    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 . 
         [0067]    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. 
         [0068]    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  702 ′,  704 ′,  706 ′ optimized to transport another positively charged species or a negatively charged species clockwise or counterclockwise to produce a third set of waveforms  702 ″,  704 ″,  706 ″ that achieve transport of differing species in desired respective paths. 
         [0069]    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. 
         [0070]    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. 
         [0071]    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. 
         [0072]    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. 
         [0073]    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.