Abstract:
An ionizer provides charged particles to charge a combustion reaction. A conductive flame holder cooperates with the charged combustion reaction to hold the combustion reaction away from a fuel nozzle. Dilution and/or premixing of the fuel in the region between the fuel nozzle and the conductive flame holder results in a reduced flame temperature. The reduced flame temperature results in a reduced output of oxides of nitrogen (NOx).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority benefit from U.S. Provisional Patent Application No. 61/730,486 entitled “MULTISTAGE IONIZER FOR A COMBUSTION SYSTEM” filed Nov. 27, 2012; which, to the extent not inconsistent with the disclosure herein, is incorporated by reference. 
         [0002]    The following U.S. patent applications, filed concurrently herewith, are directed to subject matter that is related to or has some technical overlap with the subject matter of the present disclosure, and are incorporated herein by reference, in their entireties: U.S. patent application, docket number 2651-064-03; U.S. patent application, docket number 2651-065-03; U.S. patent application, docket number 2651-073-03; U.S. patent application, docket number 2651-100-03; and U.S. patent application, docket number 2651-147-03. 
     
    
     SUMMARY 
       [0003]    According to an embodiment, an electrodynamic burner includes a fuel nozzle configured to provide fuel, an ionizer configured to output charged particles and positioned away from the fuel nozzle and the combustion reaction, and configured to apply corresponding charges to a combustion reaction supported by the fuel. An electrically conductive flame holder is positioned away from the fuel nozzle. The charge applied to the flame by the charged particles interacts with the flame holder to hold the combustion reaction proximate to the flame holder. A lift distance between the fuel nozzle and the conductive flame holder operates as a mixing zone to entrain air and/or flue gas into the fuel. The entrainment and dilution of the fuel in turn reduces combustion reaction temperature to reduce the production of oxides of nitrogen (NOx) by the burner. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a block diagram of a combustion system with an ion flow upstream of a reaction front to control a combustion reaction, according to an embodiment. 
           [0005]      FIG. 2A  is a block diagram of an ionizer, according to an embodiment. 
           [0006]      FIG. 2B  is a block diagram of an ionizer, according to another embodiment. 
           [0007]      FIG. 3  is a block diagram of a combustion system including an ion flow to control a combustion reaction, according to another embodiment. 
           [0008]      FIG. 4A  is a block diagram of a combustion system including a plurality of combustion reactions, according to an embodiment. 
           [0009]      FIG. 4B  is a block diagram of the system of  FIG. 4A  in which ion flows are of opposite polarities, according to an embodiment. 
           [0010]      FIG. 5A  is a block diagram of a combustion system, according to an embodiment. 
           [0011]      FIG. 5B  is a block diagram of the system of  FIG. 5A  in which the ion flows have opposite polarities, according to an embodiment. 
           [0012]      FIG. 6  is a block diagram of a combustion system including a system for employing ion flows to control the interaction of adjacent combustion reactions, according to another embodiment. 
           [0013]      FIG. 7  is a block diagram of a combustion system, according to another embodiment. 
           [0014]      FIG. 8  is a flow diagram of a method for employing an ion flow to control a combustion reaction, according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    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 other changes may be made without departing from the spirit or scope of the disclosure. 
         [0016]    The inventors have recognized that electrodes in contact with, or in close proximity to the combustion reaction may be damaged by heat or reactive species from the combustion reaction, which can reduce the ability to control the combustion reaction. For example, electrodes with limited surface area, small radius of curvature, and/or sharp edges, such as may be employed for charge injection or corona electrodes, are frequently susceptible to such damage. Additionally, electrodes made from certain materials may be susceptible to such damage, in some cases so susceptible that such damage may discourage the use of otherwise desirable electrode materials for cost or practicality reasons. Moreover, electrode replacement is costly in terms of combustion reaction downtime, electrode materials, and/or labor, not to mention reduced control efficiency of such electrodes prior to replacement. 
         [0017]    According to some embodiments, a combustion reaction charging system having “active”, or current-carrying parts in a combustion volume, may require a more extensive procedure to replace broken or worn parts and/or may require shutdown or large fuel turn-down to access the broken or worn parts. Accordingly, service and reliability can be positively affected by placing active parts outside the combustion volume. 
         [0018]    The inventors propose providing an ionizer mechanism configured to create charged particles, which are then introduced to the combustion reaction as a means of applying an electrical charge to the combustion reaction. The charged particles can be drawn from any appropriate material or combination of materials, including, for example, components of the combustion reaction, such as oxidizer gas (e.g., air), fuel, flue gas, reactants, etc. According to an embodiment, the ionizer mechanism may include an ion beam generator, such as an electron beam source. According to another embodiment, the ionizer mechanism may include a corona electrode and counter electrode pair immersed in a flow of dielectric fluid, such as a gas, which is to be introduced into the combustion volume. The corona electrode and counter electrode pair are configured to create ions from (deposit charges on) molecules of the dielectric fluid, or from other donor substances carried by the fluid. 
         [0019]    The ionizer may be provided as a module or modular system configured for field exchange or replacement. 
         [0020]    The term combustion reaction is to be construed as referring to an exothermic oxidation reaction. In some cases a combustion reaction can include a stoichiometric (e.g., visible) surface. In other cases, the combustion reaction may be “flameless” such that no visible boundary exists. 
         [0021]    Combustion components refers to elements that are to be introduced into the combustion volume, and that will be involved in the combustion process, such as fuel, oxidizer, EGR flue gases, modifiers, catalysts, and other substances that may be introduced. This term is not limited to reference to these elements as they are present within the combustion volume, but also prior to their introduction into the combustion volume. 
         [0022]    Combustion volume refers to the space within which a combustion reaction occurs, and is delineated according to the circumstances of the particular application. For example, many systems include a firebox or other enclosure configured to contain the combustion reaction and its products, and/or to protect individuals from the reaction. In such cases, corresponding boundaries and dimensions of the combustion volume are defined by walls or surfaces of the enclosure, to the extent reasonable. Any barrier configured to protect an element positioned on one side of the barrier from thermal energy produced by a combustion reaction positioned on an opposite side of the barrier can define a respective boundary of the combustion volume. Thus, for example, a smaller enclosure positioned partially or wholly within a combustion volume and configured to protect a circuit or other device from heat produced by a combustion reaction effectively removes the volume defined by the smaller enclosure from the combustion volume. 
         [0023]    Where an enclosure is not present, or where portions of an enclosure are far enough from the combustion reaction that they do not effectively constrain aspects of the combustion reaction, the combustion volume can be defined as the volume within which the ambient temperature is at least 400° F. The combustion volume also includes regions that are significantly hotter than 400° F. For example, a temperature of up to near the adiabatic flame temperature can be encountered in some practical combustion systems. 
         [0024]    Generally, the opening, i.e., terminus, of a fuel nozzle or burner that is configured to support the combustion reaction defines a boundary or limit of the combustion volume, such that fuel flowing from the nozzle enters the combustion volume as it is emitted from the nozzle. Likewise, nozzles, openings, vents, etc. by which other components of a combustion reaction are introduced can define respective boundaries of a combustion volume. Another boundary is at the approximate point within an exhaust passage, such as a flue or chimney, at which the exothermic process is no longer self-sustaining. 
         [0025]    Embodiments illustrating the use of charged particles for applying a charge to a combustion reaction are primarily described in the present disclosure with reference to ions and ionizers. However, this is merely illustrative. Other varieties of charged particles are well known, as are mechanisms for their production. The term charged particle, as used in the claims, is not limited to ions, but is to be construed broadly as reading on any type of charged particle, i.e., any particle that is not electrically neutral. In some cases, the charged particles may be present in the form of free- or loosely associated-electrons. In other cases, the charged particles can include at least a nucleus, as in a H+, and/or can include a charged atomic pair or charged molecule. It will be understood that descriptions related to the production of ions herein may also apply to the production of charged particles that are not ions per se (e.g., electrons). 
         [0026]      FIG. 1  is a block diagram of system  100  for employing an ion flow  102  to control a combustion reaction  104 , according to an embodiment. 
         [0027]    According to an embodiment, the system  100  includes an ionizer  106 , which is configured to provide an ion flow  102  to a first location  108  with respect to the opening of a nozzle or terminus  109  of a burner  110  supporting a combustion reaction  104 . The ion flow  102  has a first polarity. The ion flow  102  is configured to impart a net charge to the combustion reaction  104 , or a component thereof. A first electrode  114  can be positioned at a second location  115  that is downstream  111  of the first location  108  and at least intermittently separated from the combustion reaction  104  by an air gap  117 . A voltage source  118  is operatively coupled to the first electrode  114 . A controller  120  is operatively coupled to provide one or more electrical signals to the ionizer  106  and the voltage source  118 . The controller can be configured to control the combustion reaction  104  by selection of the one or more electrical signals. The first location  108  is at least intermittently upstream  113  with respect to a reaction front  112  of the combustion reaction  104 . According to embodiments, the controller  120  is configured to control the voltage supply and the ionizer  106  to maintain the air gap  117  between the combustion reaction  104  and the first electrode  114 . In other embodiments, the first electrode  114  can be electrically insulated, such as by a fused quartz glass. In other embodiments. The first electrode  114  can be in electrical continuity with the combustion reaction. Current flow through the combustion reaction can be controlled by maintaining resistance between the first electrode  114  and a voltage source for the first electrode, for example. 
         [0028]    The terms upstream, indicated in the drawings by the arrow  111 , and downstream, indicated by arrow  113 , are with reference to a composite flow associated with a combustion reaction that includes, for example, a fuel flow, an oxidizer flow, a flow of reactants within the combustion reaction, and a flow of products of the combustion reaction, i.e., flue gas and its various components. Use of these terms without further modification or definition can be construed as referring to relative positions along this composite flow. 
         [0029]    According to various embodiments, the ion flow  102  is selected to impart the charge and the first polarity to the combustion reaction  104 . Additionally or alternatively, the ion flow  102  may be selected to impart the charge and the first polarity to a fuel of the combustion reaction  104 . Additionally or alternatively, the ion flow  102  may be selected to impart the charge and the first polarity to an oxidizer of the combustion reaction  104 . Additionally or alternatively, the ion flow  102  may be selected to impart the charge and the first polarity to a carrier gas of the combustion reaction  104 . Additionally or alternatively, the ion flow  102  may be selected to impart the charge and the first polarity to a product of the combustion reaction  104 . Additionally or alternatively, the ion flow  102  may be selected to impart the charge and the first polarity to any combination thereof of the fuel, oxidizer, carrier gas, and/or product of the combustion reaction. 
         [0030]    According to various embodiments, the controller  120  is configured to control the combustion reaction  104  by providing the one or more electrical signals carried by signal carriers  107 , such as wires. The one or more electrical signals carried by the signal carriers  107  may cause an increase or decrease in one or more of a height of the combustion reaction  104  or a surface area of the combustion reaction  104 . Additionally or alternatively, the one or more electrical signals carried by the signal carriers  107  may cause the combustion reaction  104  to be directed to a selected location or to be directed away from the selected location. For example, this can be use to affect heat transfer and/or affect another combustion reaction ignition location. Additionally or alternatively, the one or more electrical signals carried by the signal carriers  107  may cause an oscillation in the combustion reaction  104 . Additionally or alternatively, the one or more electrical signals carried by the signal carriers  107  may dynamically control a shape of the combustion reaction  104  or a movement of the combustion reaction  104 . Additionally or alternatively, the one or more electrical signals carried by the signal carriers  107  can affect the luminance of the combustion reaction  104 . Additionally or alternatively, the one or more electrical signals carried by the signal carriers  107  can be used to control a flame holding position; wherein a first flame holding position is proximal and a second flame holding position is distal. 
         [0031]    The controller  120  is configured to cause the ionizer to instantaneously extract ions of a single polarity or add ions of a single polarity at the one or more first electrodes  114  from/to the combustion reaction  104 , according to an embodiment. 
         [0032]    The first electrode  114  can be configured to affect various characteristics of the combustion reaction  104  such as, for example, shape, location, luminosity, reaction rate. Depending on resistance through the first electrode to an electrical potential different from the electrical potential imparted onto the combustion reaction  104  by the ionizer  106 , the first electrode can additionally or alternatively affect charge concentration in the combustion reaction  104 . The controller  120 , together with the voltage source  118 , can be configured to hold the combustion reaction  104  at a surface of the burner  110 . In the example of  FIG. 1 , the “burner”  110  may be embodied as a fuel nozzle  109  and flame holder  114  (aka, the first electrode), and the flame holder can operate as a flame holding surface. Not shown, a distal flame holder can hold the combustion reaction  104  when the controller  120  does not cause the voltage source  118  to hold the combustion reaction at the flame holder/first electrode  114 . 
         [0033]    According to an embodiment, the burner  110  is electrically isolated and/or insulated from electrical ground and from voltages other than those defined by the ionizer  106  and/or the first electrode  114 . According to various embodiments, the controller  120  is configured to apply the one or more electrical signals to the one or more first electrodes  114 . The controller  120  can cause a charge carried by the combustion reaction  104  to respond to the one or more electrical signals applied to the ionizer  106  and/or the first electrode  114 . 
         [0034]    The controller  120  can be configured to operate the ionizer  106  to periodically or intermittently change a quantity or a concentration of charge in the ion flow  102  or in the combustion reaction  104 . Additionally or alternatively, the controller  120  can be configured to operate the ionizer  106  to periodically or intermittently change the first charge polarity in the ion flow  102  or in the combustion reaction  104 . The one or more electrical signals can be characterized by one or more voltages. Additionally or alternatively, the one or more electrical signals can be controlled to influence or control an electrical field adjacent to the combustion reaction  104 . The one or more electrical signals can include a time-varying signal configured to control the ionizer  106  to output a time-varying charge and/or control the first electrode  114  to deplete a charge carried by the combustion reaction  104  in a time-varying way. Additionally or alternatively, the one or more electrical signals can include a time-varying voltage. Additionally or alternatively, the one or more electrical signals can be switched to provide a time-varying electrical continuity to the ionizer  106  and/or the first electrode  114 . 
         [0035]    The combustion reaction  104  can be embodied as a visible flame or can consist essentially of a flameless reaction, according to embodiments. 
         [0036]    As previously noted, according to the embodiment of  FIG. 1 , the ionizer  106  is configured to provide an ion flow  102 . As used herein, ion flow refers to a flow of ions (including precursor ions (e.g., ions that will subsequently be converted to charges carried by other particles), to the extent that they may be present) in some medium (theoretically, the medium could be comprised substantially 100% of ions, however typical ionizer technologies do not provide such a high charge carrying efficiency) through space to a combustion reaction  104 , with the ions carried by the ion flow then being substantially transferred to the combustion reaction  104 . An ion flow may be provided by ionizing a gas, and the gas may then flow through space to the combustion reaction  104 . The ionized gas can include a fuel, such as a hydrocarbon gas; or can include an oxidant flow, such as air. Additionally or alternatively, an ion flow may be provided by ionizing a gas in the form of a dielectric vapor. An ion flow may be provided by ionizing particles or droplets in an aerosol. An ion flow may be provided by ionizing molecules of a dielectric liquid. An ion flow may be provided by depositing ions on a particulate solid. Combinations of the above-described ion flows may become evident with further variations that fall within the scope of claims appended hereto. 
         [0037]    In an embodiment, the ionizer  106  is configured to provide the ion flow  102  by contacting the ion flow  102  to at least one of air or a fuel. The ion flow  102  can be contacted to air or may consist essentially of combustion air to form a charged air flow. Additionally or alternatively, the ion flow  102  can be contacted to or consist essentially of fuel to form a charged fuel flow. Additionally or alternatively, the ion flow  102  is contacted to at least one of air or a fuel or can consist essentially of a fuel/air mixture to form a charged fuel/air mixture flow. In the case of charging a fuel/air mixture, care should be taken to prevent any inadvertent spark discharge that could cause detonation. 
         [0038]    According to embodiments, the ionizer  106  can be configured to provide the ion flow  102  at a positive polarity. Additionally or alternatively, the ionizer  106  may configured to provide the ion flow  102  at a negative polarity. 
         [0039]    According to an embodiment, the controller  120  is configured to control the combustion reaction  104  such that the first location  108  is substantially upstream  113  (e.g., averaged over time) with respect to the reaction front  112  of the combustion reaction  104 . For example, the first location can include a flow distance through which the ion flow  102  travels between the ionizer  106  and the combustion reaction  104 . 
         [0040]    According to another embodiment, the ionizer  106  can output the ion flow  102  to the combustion reaction  104  above the lower reaction front  112 . For example, as shown in  FIGS. 5A ,  5 B, the ionizer can output an ion flow to the combustion reaction  104  through a conduit  302  including at least a dielectric portion configured to guide the ion flow while maintaining electrical isolation of the combustion reaction  104  with respect to the ionizer body  106 . 
         [0041]      FIG. 2A  is a diagram of an ionizer  200 A, according to an embodiment. The ionizer  200 A includes a charge source, such as a corona electrode  204  configured to cooperate with a counter electrode  206  to produce an ion discharge. 
         [0042]    According to embodiments, the ionizer  200 A is electrically isolated. According to various embodiments, the ionizer  200 A imparts charged particles, in the form of ions, to the ion flow  102  via a corona discharge. Additionally or alternatively, the ionizer  200 A may impart ions to the ion flow  102  via an electrospray ionization. Additionally or alternatively, the ionizer  200 A may impart ions to the ion flow  102  via a thermospray ionization. Additionally or alternatively, the ionizer  200 A may impart ions to the ion flow  102  via a field desorption ionization. Additionally or alternatively, the ionizer  200 A may impart ions to the ion flow  102  via a photoionization. Additionally or alternatively, the ionizer  200 A may impart ions to the ion flow  102  via a photoelectric ionization. Additionally or alternatively, the ionizer  200 A may impart ions to the ion flow  102  via a radioactive decay ionization. Additionally or alternatively, the ionizer  200 A may impart ions to the ion flow  102  via any combination thereof of the corona discharge, electrospray ionization, thermospray ionization, field desorption ionization, photoionization, photoelectric ionization, and/or radioactive decay ionization. 
         [0043]    According to an embodiment, the ionizer  200 A imparts a charge to the ion flow  102  via ejection of generated ions (e.g. electrons) at corona electrode  204  to produce negatively charged ions. Additionally or alternatively, the ionizer  200 A may impart a charge to the ion flow  102  via extraction of charges (e.g., electrons) from neutral particles proximate the corona electrode  204  to produce positively charged ions. This is also referred to as charge ejection. A counter-electrode  206  applies an electric field to pull the ejected charges away from the corona electrode in a direction toward an entraining dielectric fluid flow and/or toward a location where the ion flow  102  leaves the ionizer body  106 . Other ionization modalities, referenced herein or known in the art, may replace the corona/counter electrode  204 / 206  arrangement shown in  FIG. 2A . The ionizer  200 A may produce a net charge density at the ionizer  200 A of about 1 million charges per cubic centimeter or more, according to embodiments. 
         [0044]    According to an embodiment, the controller  120  is configured to detect a short circuit at the corona electrode  204  in the ionizer  200 A. The controller  120  is configured to reduce or stop the voltage applied to the corona electrode  204  in the ionizer  200 A responsive to the short circuit at the corona electrode  204 . 
         [0045]    According to embodiments, a fluid source  222  can be configured to provide a fluid  224  to the ionizer  200 A in the form of a gas. Additionally or alternatively, the fluid  224  may be provided to the ionizer  200 A in the form of a vapor. Additionally or alternatively, the fluid  224  may be provided to the ionizer  200 A in the form of a liquid aerosol. Additionally or alternatively, the fluid  224  may be provided to the ionizer  200 A in the form of a dielectric liquid stream. Additionally or alternatively, the fluid  224  may be provided to the ionizer  200 A in the form of any combination thereof of the gas, vapor, liquid aerosol, and/or liquid stream. 
         [0046]    In an embodiment, the fluid source  222  is operatively coupled to provide the fluid  224  to the ionizer  200 A using a nebulizer. Additionally or alternatively, the fluid  224  may be provided to the ionizer  200 A using an atomizer. The fluid  224  may be provided to the ionizer  200 A using an injector. The fluid  224  may be provided to the ionizer  200 A using a steam generator. The fluid  224  may be provided to the ionizer  200 A using an ultrasonic humidifier. The fluid  224  may be provided to the ionizer  200 A using a vaporizer. The fluid  224  may be provided to the ionizer  200 A using an evaporator. The fluid  224  may be provided to the ionizer  200 A using a pump. Additionally or alternatively, the fluid  224  may be provided to the ionizer  200 A using any combination thereof of the nebulizer, atomizer, injector, steam generator, ultrasonic humidifier, vaporizer, evaporator, and/or pump. 
         [0047]    According to various embodiments, the ionizer  200 A is configured to provide an ion flow  208  by ionizing a fluid  224 . The fluid  224  may include a buffer or may be functionalized to hold a charge, and can be impelled by any appropriate means, including, e.g., a pump, fan, compressor, etc. In other embodiments, the fluid source  222  is a combustion air  224  source, and may include either natural draft or forced draft aspects. In other embodiments, the fluid source  222  is a fuel source, such as a hydrocarbon gas source. According to an embodiment, the ionizer  200 A is positioned in series with a main fuel line of a combustion system, such that a flow of fuel to a burner of the combustion system passes through the ionizer and incorporates the ion flow  208 . 
         [0048]    According to other embodiments, a valve  226  is operatively coupled to the fluid source  222  and the controller  120 . The controller  120  is configured to operate the valve  226  to control a flow of the fluid  224  from the fluid source  222 . The fluid source  222  is configured to supply the fluid  224  to the ionizer  200 A and maintain electrical isolation between the conductive and/or grounded parts of the fluid source  222  and the ionizer  200 A. The fluid source  222  includes a tank  228  to hold the fluid  224 . The tank  228  can be made of an electrically insulating material to isolate the fluid  224  from ground or another voltage. Additionally or alternatively, the tank  228  may be supported by electrical insulators to isolate the fluid  224  from ground or another voltage. An anti siphon  230  arrangement is configured to maintain electrical isolation between the fluid source  222  and the ionizer  200 A. However, since corona discharge ionization requires a charge separation across a dielectric layer adjacent to a corona electrode  204  (e.g., exhibited as electric field curvature around emission surfaces), most embodiments are contemplated as being based on a dielectric fluid  224  having a relatively high dielectric constant (i.e., being substantially non-conductive). Accordingly, the anti siphon arrangement  230  may be often embodied as simply a length of low conductivity material or an isolation distance between the corona electrode  204  and adjacent conductive components. 
         [0049]      FIG. 2B  is a sectional diagram of an ionizer  200 B, according to another embodiment. According to embodiments, the ionizer  200 B includes a body  250  defining a vaporization well  252 . Third and fourth electrodes  254   a ,  254   b  are operatively coupled to the voltage source  118  and are configured to apply a high voltage to a liquid at least temporarily resident in the vaporization well  252 . The voltage source  118  is configured to apply a voltage to vaporize the liquid to produce a vapor of the liquid. The vapor then carries charged particles from the ionizer. Additionally or alternatively, the voltage source  118  may be configured to apply a voltage to produce an aerosol or a mixed vapor and aerosol of the liquid, which, in either case, carries charged particles from the ionizer. 
         [0050]    According to various embodiments, the liquid includes water. Additionally or alternatively, the liquid may include a buffer solution or may be at least partly functionalized to hold a charge. 
         [0051]    The electrodes  254   a ,  254   b  are energized at a bias voltage to produce the polarity of the charges carried by the vapor or aerosol. For example, to produce positive charges, the electrode  254   a  can be briefly energized with +40 kV while the electrode  254   b  is energized or held at +20 kV. The 20 kV difference between the electrodes produces vaporization. The +30 kV average voltage operates as a bias voltage to produce positive charges in the ejected vapor/aerosol. In some embodiments, kinetic energy from the vaporization is sufficient to propel the ion flow  102  through the flow distance (e.g., see  FIG. 1 ,  108 ) to the combustion reaction (not shown in  FIG. 2B ) or to an entraining fluid stream. Optionally, a counter electrode  206  can be positioned to accelerate the charged particles toward their intended destination as an ion flow  102 . 
         [0052]      FIG. 3  is a diagram of a system  300  for employing an ion flow to control a combustion reaction, according to an embodiment. The ionizer  106  is configured to provide at least a portion of the ion flow  102 , which is introduced upstream  113  of the terminus  109  of a burner or fuel source  110 . For example, the ionizer  106  can be configured to provide at least a portion of the ion flow  102  through the burner or fuel source  110 . In an alternative embodiment (see, e.g.,  FIGS. 4A and 4B ), the ionizer  106  is configured to provide at least a portion of the ion flow  102  downstream  111  from the terminus  109  and upstream  113  from the reaction front  112 . 
         [0053]    According to embodiments, a conduit  302  is configured to convey the ion flow  102  from the ionizer  106  to the first location  108 . The conduit  302  can be electrically isolated. The conduit  302  may include a conduit electrode operatively coupled to the voltage supply, in which case, the controller  120  can be configured to control the voltage supply to apply a voltage at the first polarity to the conduit electrode. The maximum charge density output of the ionizer  106  can be within about 10 centimeters of a downstream  111  terminus of the burner or fuel source  110 . The conduit  302  preferably includes a material that resists reaction with the ion flow  102 . 
         [0054]    The conduit  302  is thermally insulated, according to various embodiments. For example, a portion of the conduit  302  or an opening of the conduit  302  can be shielded from the combustion reaction  104  by a shroud (not shown) located at least in part upstream  113  of the first location  108 . The shroud may be thermally reflective. A cooling apparatus (not shown) may be operatively coupled to the conduit  302  to cool the conduit  302 . 
         [0055]    Referring again to  FIG. 3 , according to various embodiments, a system  300  may include a flow control valve  306  operatively coupled to the controller  120  and the burner or fuel source  110 . The controller  120  is configured to operate the ionizer  106 , the voltage source  118 , and the flow control valve  306  to control the combustion reaction  104 . 
         [0056]    According to various embodiments, a system  300  may include a waveform generator  304  that is operatively coupled to the controller  120  and the voltage supply. The waveform generator  304  is configured to generate one or more waveforms. The waveform generator  304  is configured together with the controller  120  to drive the ionizer  106  or the one or more first electrodes  114  with the one or more waveforms. The one or more electrical signals may include the one or more waveforms. 
         [0057]    According to embodiments, the waveform generator  304  is configured to generate an alternating current (AC) voltage waveform. Additionally or alternatively, the waveform generator  304  may be configured to generate a sinusoidal waveform. The waveform generator  304  may generate a square waveform. The waveform generator  304  may generate a sawtooth waveform. The waveform generator  304  may generate a triangular waveform. The waveform generator  304  may generate a wavelet waveform. The waveform generator  304  may generate a logarithmic waveform. The waveform generator  304  may generate an exponential waveform. The waveform generator  304  may generate a truncated waveform. The waveform generator  304  may generate a combination of one or more waveform thereof. 
         [0058]      FIG. 4A  is a block diagram of a system  400  for employing a plurality of ion flows to control the interaction of adjacent combustion reactions, according to an embodiment. The system  400  includes a pair of burners  110   a ,  110   b , and corresponding second electrodes  116   a ,  116   b  operatively coupled to the voltage source  118 . An ionizer  106  includes first and second conduits  302   a ,  302   b  configured to deliver respective ion flows  102   a ,  102   b  to the corresponding combustion reactions  104   a ,  104   b . As shown in  FIG. 4A , the conduits  302   a ,  302   b  are positioned and configured to introduce the ion flows  102  upstream from the opening or terminus of the burner  110 . 
         [0059]    In the claims, the term sub-flow is used where a plurality of flows of charged particles are introduced to one or more combustion reactions within a same combustion volume. Thus, the ion flows  102   a ,  102   b  of  FIG. 4A  can also be referred to as sub-flows that together form a single ion flow. 
         [0060]    A controller  120  is configured to control the ionizer  106 , first electrodes (not shown) and the second electrodes  116  to control the combustion reaction  104 . The second electrodes  116  electrically isolated. 
         [0061]    The controller  120  is operatively coupled to provide electrical signals to the ionizer  106  and the voltage source  118  to independently control polarity and volume of the ion flows  102   a ,  102   b . The controller  120  is configured to control the combustion reactions  104  by applying charges to the combustion reactions via the ion flows  102 . The controller  120  may also be configured to further control the combustion reactions  104  by applying electrical energy via first electrodes  114 , as described above with reference to  FIG. 1 . 
         [0062]    According to one method of operation, the controller is configured to produce an electrostatic repulsion  402  between the first and second instance combustion reactions  104   a ,  104   b , by controlling the ionizer  106  to produce ion flows  102   a ,  102   b , having a same polarity, as shown in  FIG. 4A . The corresponding net charge applied to the combustion reactions  104   a ,  104   b  causes the combustion reactions to be mutually repulsive. 
         [0063]      FIG. 4B  is a block diagram of the system  400  illustrating a second method of operation, according to an embodiment. 
         [0064]    As shown, the controller  120  is configured to control the first and second ion flows  102   a ,  102   b  to have opposite polarities, which produces an electrostatic attraction  404  between the first and second combustion reactions  104   a ,  104   b . The controller  120  can be configured to control the electrostatic attraction  404  to cause mixing between the first combustion reaction  104   a  and the second combustion reaction  104   b.    
         [0065]      FIG. 5A  is a block diagram of a combustion system  500 , according to an embodiment. In most respects, the system  500  is substantially identical to the system  400  of  FIGS. 4A and 4B . However, where the system  400  is configured to introduce the ion flows  102   a ,  102   b  upstream of the burners  110   a ,  110   b , the system  500  is configured to introduce the ion flows  102  downstream of the burners  110 . 
         [0066]    In  FIG. 5A , the ion flows  102   a ,  102   b  are have a same polarity, similarly to the operation of the system  400  described with reference to  FIG. 4A . As a result of the common polarity of the ion flows  102 , the combustion reactions  104   a ,  104   b  are electrically repulsed. 
         [0067]      FIG. 5B  shows the system  500  of  FIG. 5A , with the ionizer  106  controlled to produce the ion flows  102   a ,  102   b  at opposite polarities. As a result, the combustion reactions  104  are attracted to each other, substantially as described with reference to  FIG. 4B . In an embodiment, the system  500  can include a second ionizer  106  configured to provide the second ion flow  102   b  having a second polarity to the third location  108   b  downstream  113  of a second reaction front  112   b  of the second combustion reaction  104   b . The controller  120  can be configured to independently control the first and second instances of the combustion reaction  104   a ,  104   b . The controller  120  can be further configured to control an electrostatic repulsion  402  between the first instance of the combustion reaction  104   a  and the second instance of the combustion reaction  104   b  by causing the first polarity and the second polarity to be the same. The controller  120  can be further configured to control an electrostatic attraction  404  between the first instance of the combustion reaction  104   a  and the second instance of the combustion reaction  104   b  by causing the first polarity and the second polarity to be different. The controller  120  can be further configured to control the electrostatic attraction  404  to cause mixing between the first instance of the combustion reaction  104   a  and the second instance of the combustion reaction  104   b.    
         [0068]    According to an embodiment, the burner or fuel source  110  can be electrically insulated, electrically isolated, or electrically insulated and isolated. The controller  120  can be configured to operate the ionizer  106  to periodically and/or intermittently change a quantity and/or a concentration of charge in the ion flow  102 . The controller  120  can be configured to operate the ionizer  106  to periodically and/or intermittently change a quantity and/or a concentration of charge in the combustion reaction  104 . And/or the controller  120  can be configured to operate the ionizer  106  to periodically and/or intermittently change the first charge polarity in the ion flow  102  and/or in the combustion reaction  104 . 
         [0069]    According to an embodiment, the controller  120  can be configured to apply the one or more electrical signals to the one or more first electrodes  114  to cause a charge of the combustion reaction  104  to respond to the one or more electrical signals. The one or more electrical signals can include a charge, a voltage, an electrical field, or a combination thereof. Additionally, the one or more electrical signals can include one or more of a time-varying charge, a time-varying voltage, a time varying electric field, or a combination thereof. A waveform generator  304  can be included, according to an embodiment. The waveform generator  304  can be operatively coupled to the controller  120  and the power supply  118 . The waveform generator  304  can be configured to generate one or more waveforms. The waveform generator  304  can be configured together with the controller  120  to drive the ionizer  106  and/or the one or more first electrodes  114  with the one or more waveforms such that the one or more electrical signals can include the one or more waveforms. The waveform generator  304  can be configured to generate one or more of an alternating current (AC) voltage waveform, a sinusoidal waveform, a square waveform, a sawtooth waveform, a triangular waveform, a wavelet waveform, a logarithmic waveform, an exponential waveform, a truncated waveform, or a combination waveform thereof. 
         [0070]      FIG. 6  is a block diagram of a system  600  for employing ion flows to control the interaction of adjacent combustion reactions, according to another embodiment. The system  600  is substantially similar to the system  100  of  FIG. 1 , except that the ionizer  106  is configured to introduce a plurality of ion flows  102  to the combustion reaction  104 . In the embodiment shown, a first ion flow  102  is introduced at a first location  108  that is upstream  113  relative to a reaction front  112  of the combustion reaction  104 . A second ion flow  102 ′ is introduced at a second location  108 ′ that is upstream  113  relative to the first location  108 . The second location  108 ′ may be positioned upstream  113  or downstream  111  relative to the reaction front  112 . According to an embodiment, both locations  108 ,  108 ′ are at least intermittently upstream of the reaction front  112 . According to another embodiment, the first location  108  is positioned upstream with respect to the terminus  109  of the burner  110 . 
         [0071]    The first and second ion flows  102 ,  102 ′ can be provided by a single ionizer  106 , as shown, or by separate ionizers. 
         [0072]    In an embodiment, the ionizer  106  is configured to provide the first and second ion flows  102 ,  102 ′ at first and second polarities effective to cause mixing of the first and second charged ion flows  102 ,  102 ′. For example, the opposing first and second polarities can be configured to cause an electrostatic attraction that facilitates mixing of the first and second ion flows  102   a ,  102   b , and consequently promotes improved mixing of components of the combustion reaction  104 . 
         [0073]    According to an embodiment, the ionizer  106  is configured to provide the first and second charged ion flows  102 ,  102 ′ in unequal respective first and second charge quantities or strengths, resulting in a net charge  103  of the combustion reaction  104 . By selection of the polarities and strengths of the respective ion flows, the combustion reaction  104  can be further controlled as described with reference to previous embodiments. 
         [0074]      FIG. 7  is a block diagram of a system  600  that includes first and second burners  110   a ,  110   b , each configured to support a respective combustion reaction  104   a ,  104   b . Each of the first and second burners  110  is associated with respective first and second ion flows  102   a ,  102   a ′ and  102   b ,  102   b ′. Each of the first and second burners  110   a ,  110   b  and associated elements operates substantially as described with reference to the system  600  of  FIG. 6 . Jointly, the combustion reactions  104   a ,  104   b  can be manipulated, by selection of strengths and polarities of the respective ion flows, to function as described with reference to the combustion reactions  104   a ,  104   b  of  FIGS. 4A ,  4 B,  5 A, and  5 B. 
         [0075]      FIG. 8  is a flow diagram of a method  500  for employing an ion flow downstream of a reaction front to control a combustion reaction, according to an embodiment. In an embodiment, a method is provided for employing an ion flow to control a combustion reaction. The method includes  802  supporting a combustion reaction at a burner. The method also includes  804  generating an ion flow having a first polarity. The method may further include  806  introducing the ion flow to the combustion reaction or a component of the combustion reaction at a first location. The first location is, according to an embodiment, at least intermittently upstream with respect to at least a portion of a reaction front of the combustion reaction. The method additionally includes  808  imparting a charge to the combustion reaction via the ion flow. The method shown includes  810  controlling the combustion reaction by applying one or more electrical signals to respective electrodes positioned at locations that are downstream of the first location, causing the combustion reaction to respond due to the imparted charge. The one or more electrodes thus control aspects of the combustion reaction by application of the one or more electrical signals. 
         [0076]    In an embodiment, imparting the charge can include selecting the ion flow to impart the charge and the first charge polarity to the combustion reaction, a fuel of the combustion reaction, an oxidizer of the combustion reaction, a carrier gas of the combustion reaction, a product of the combustion reaction, another component of the combustion reaction, a combination of components of the combustion reaction, etc. 
         [0077]    In an embodiment of the method, controlling the combustion reaction may include extracting ions of a single polarity at the one or more electrodes from the combustion reaction. Generating the ion flow may also include providing a ion flow, such as by ionizing a gas, a vapor, a liquid aerosol, a dry aerosol, a particulate solid, or a combination of elements. Generating the ion flow may also include contacting an ion flow to air or a fuel to form a charged air flow, a charged fuel flow, or a charged air-fuel mixture flow. 
         [0078]    In an embodiment, the method can include providing the ion flow at a positive polarity, a negative polarity, or, where multiple ion flows (i.e., sub-flows) are used, both. 
         [0079]    In an embodiment, the method may include controlling the combustion reaction such that the first location is substantially upstream over time with respect to the reaction front of the combustion reaction. The method may also include providing at least a portion of the ion flow upstream of the burner or fuel source. The method may further include providing at least a portion of the ion flow through the burner or fuel source. The method may, alternatively, include providing at least a portion of the ion flow downstream from the burner or fuel source and upstream from the reaction front. 
         [0080]    In an embodiment, the method may include providing the ion flow by ionizing a gas, a vapor, an aerosol, a particulate solid, an oxidant or a fuel of the combustion reaction, combinations of elements, etc. 
         [0081]    In an embodiment, the method may include electrically isolating the ionizer. The method may include imparting ions to the ion flow via a corona discharge. The method may include imparting ions to the ion flow via an electrospray ionization, a thermospray ionization, a field desorption ionization, via a photoionization, a photoelectric ionization, a radioactive decay ionization, etc. 
         [0082]    In an embodiment, the method may include imparting a charge to the ion flow via generating and injecting ions, selectively extracting preexisting ions, or a combination thereof. Applying electrical signals to the ionizer to generate the ion flow may include producing a net charge density at the ionizer of at least about 1 million charges per cubic centimeter. 
         [0083]    In an embodiment, applying electrical signals to the ionizer to generate the ion flow may include employing a corona electrode and a counter electrode to generate ions in the ionizer. Applying the one or more electrical signals to the ionizer to generate the ion flow may also include detecting a short at the corona electrode in the ionizer. The method may further include reducing the voltage applied to the corona electrode in the ionizer responsive to the short at the corona electrode. 
         [0084]    In an embodiment, applying the one or more electrical signals to the ionizer to generate the ion flow may include providing a fluid to the ionizer in the form of a gas, a vapor, an aerosol, a dielectric liquid stream, etc. 
         [0085]    In an embodiment, the method may include providing the fluid to the ionizer using a nebulizer, an atomizer, an injector, a steam generator, an ultrasonic humidifier, a vaporizer, an evaporator, a pump, etc. 
         [0086]    In an embodiment, applying electrical signals to the ionizer to generate the ion flow may include preparing an ion flow by ionizing a gas, a vapor, a liquid aerosol, a dry aerosol, a liquid, a particulate solid, etc. Applying electrical signals to the ionizer to generate the ion flow may also include forming the ion flow by contacting the ion flow to water, in the form of a vapor, a steam, a liquid, a liquid aerosol, etc. The fluid may include a buffer or be functionalized to hold a charge. The method may also include controlling a flow of the fluid to an ionizer. Applying electrical signals to the ionizer to generate the ion flow may also include supplying the fluid to the ionizer and maintaining electrical isolation between the fluid source and the ionizer. Applying electrical signals to the ionizer to generate the ion flow may also include electrically isolating the fluid from ground or another voltage. Additionally or alternatively, generating an ion flow in step  204  can include attracting ions away from an ion source and toward a desired flow direction can include attracting the ions with a counter-electrode. In the cases where an ion source other than a corona electrode is used, the counter-electrode may be referred to as a propulsion electrode. 
         [0087]    In an embodiment, applying electrical signals to the ionizer to generate the ion flow may include applying a voltage to a liquid to vaporize the liquid to produce a vapor, aerosol, or vapor and aerosol of the liquid to carry charged particles. The liquid may include a buffer solution or may be at least partly functionalized to hold a charge. 
         [0088]    In an embodiment, introducing the ion flow at the first location may include conveying the ion flow from the ionizer to the first location using a conduit. Introducing the ion flow at the first location may also include electrically isolating the conduit. Generally speaking, the conduit is formed at least partially from a dielectric material selected to maintain electrical insulation between the combustion reaction and the ionizer. The use of a dielectric conduit can prevent the conduit from acting as an immersed electrode in direct contact with the combustion reaction. In an embodiment, the conduit can be formed from fused quartz glass or other ceramic material that maintains relatively high electrical resistivity at temperatures encountered in the combustion volume. The method may include applying a voltage at the first polarity to the conduit electrode. Introducing the ion flow at the first location may further include providing a maximum charge density output of the ionizer within about 10 centimeters of a downstream terminus of the burner or fuel source. Introducing the ion flow at the first location may also include employing a conduit material that resists reaction with the ion flow. Introducing the ion flow at the first location may further include thermally insulating the conduit or cooling the conduit. 
         [0089]    In an embodiment, the method may also include electrically isolating the one or more electrodes from ground or another voltage. Controlling the combustion reaction may include at least intermittently separating the one or more electrodes from the combustion reaction by an air gap. Controlling the combustion reaction may also include controlling the voltage supply and the ionizer to maintain the air gap between the combustion reaction and the one or more first electrodes. Controlling the combustion reaction may further include at least intermittently holding the combustion reaction at the burner or fuel source. 
         [0090]    In an embodiment, controlling the combustion reaction may include controlling two or more combustion reactions. Controlling the combustion reaction may include causing an electrostatic repulsion between the first combustion reaction and the second combustion reaction by charging the first combustion reaction and the second combustion reaction at the first polarity. Controlling the combustion reaction may also include causing an electrostatic attraction between the first combustion reaction and the second combustion reaction by charging the first combustion reaction at the first polarity and charging the second combustion reaction at a second polarity opposite the first polarity. Controlling the combustion reaction may further include controlling the electrostatic attraction to cause mixing between the first combustion reaction and the second combustion reaction. 
         [0091]    In an embodiment, the method may include electrically isolating the burner or fuel source. Controlling the combustion reaction may include operating a flow valve operatively coupled to the burner or fuel source. Controlling the combustion reaction may also include periodically or intermittently changing a quantity or a concentration of ions in the ion flow or in the combustion reaction. Controlling the combustion reaction may further include periodically or intermittently changing the polarity of the ion flow or the combustion reaction. 
         [0092]    In an embodiment, controlling the combustion reaction may include applying the one or more electrical signals including a charge, a voltage, an electrical field, or a combination thereof. Controlling the combustion reaction may also include applying the one or more electrical signals including one or more of: a time-varying charge, a time-varying voltage, a time varying electric field, or a combination thereof. Controlling the combustion reaction may further include generating one or more waveforms. Controlling the combustion reaction may also include driving the ionizer or the one or more electrodes with the one or more waveforms such that the one or more electrical signals include the one or more waveforms. Generating one or more waveforms may include generating one or more of: an alternating current (AC) voltage waveform, a sinusoidal waveform, a square waveform, a sawtooth waveform, a triangular waveform, a wavelet waveform, a logarithmic waveform, an exponential waveform, a truncated waveform, a DC offset voltage, etc. 
         [0093]    The method may also include supporting the combustion reaction to include a flame. 
         [0094]    According to embodiments, the combustion reaction can be supported by either a diffusion, partial premix, or premixed burner. 
         [0095]    According to a premixed burner embodiment, the ion (or charged particle) flow  102  can be introduced to the combustion reaction through a premixing chamber. For example, a charged particle source such as a corona electrode  204  and counter electrode  206  pair can be disposed in the premixing chamber, and the premixing chamber and any flame arrestor can be held or allowed to float to a voltage that allows the charged particle flow  102  to pass through the flame arrestor and into the combustion reaction. In another example, a charged particle delivery conduit  302  can deliver the charged particle flow  102  from a charged particle source into the premixing chamber. 
         [0096]    In another premixed burner embodiment, the charged particle flow  102  can be introduced above a flame arrestor and below a flame holder into a premixed fuel/air flow. The charged particle flow can be generated by a charged particle source such as a corona electrode  204  and counter electrode  206  pair can be disposed in the premixed fuel/air flow between the flame arrestor and below the flame holder, and the flame arrestor or other conductive surface past which the charged particles may flow (e.g., the flame holder) can be held or allowed to float to a voltage that allows the charged particle flow  102  to pass through the flame holder and into the combustion reaction  104 . In another example, a charged particle delivery conduit  302  can deliver the charged particle flow  102  from a charged particle source into the premixed fuel/air flow between the flame arrestor and below the flame holder. Of course, if it is desired to cause the fuel/air flow to support a combustion reaction that is held by the flame holder, then the flame holder can optionally be configured as the first electrode  114  (and be held at a voltage different from a voltage that would allow the charged particle flow  102  to pass by the flame holder. In the case of an aerodynamic flame holder, the flame holder can be formed from an electrically insulating material or can be held or allowed to float to an equilibrium voltage. In this case, the resultant charge concentration in the combustion reaction  104  can be used for purposes other than holding the combustion reaction. 
         [0097]    In another premixed burner embodiment, the ion flow  102  can be introduced above a flame holder into a premixed fuel/air flow and/or into a combustion reaction above a flame holder. The ion flow can be generated by a charged particle source, such as a corona electrode  204  and counter electrode  206  pair, can be disposed outside the combustion volume. A charged particle delivery conduit  302  can deliver the charged particle flow  102  from the charged particle source into the fuel/air flow or into the combustion reaction  104 . 
         [0098]    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.