METHOD FOR ELECTRICALLY CONTROLLED COMBUSTION FLUID FLOW

Abstract

A combustion fluid flow barrier includes an aperture to control combustion fluid flow. The combustion fluid is charged by a charge generator. The combustion fluid flow barrier includes at least one flow control electrode operatively coupled to the aperture and configured to selectively allow, attract, or resist passage of the charged combustion fluid through the aperture, depending on voltage applied to the flow control electrode.

Description

SUMMARY

According to an embodiment, a system for electrically controlling combustion fluid flow includes a charge generator configured to apply a charge or voltage to a combustion fluid flow corresponding to a combustion reaction, a combustion fluid flow barrier defining at least one aperture therethrough, at least one flow control electrode operatively coupled to the at least one aperture, a voltage source operatively coupled to the flow control electrode, and a controller configured to control an application of one or more voltages from the voltage source to the flow control electrode.

According to an embodiment, a method for electrically controlling combustion fluid flow includes outputting electrical charges to a combustion fluid to form a charged combustion fluid, supporting a body defining a plurality of apertures aligned to receive a flow of the charged combustion fluid, applying a control voltage to a control electrode disposed adjacent to the plurality of apertures, and affecting a flow of the charged combustion fluid through the plurality of apertures with an electrical interaction between the charged combustion fluid and the control voltage carried by the control electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram of a system for electrically controlling combustion fluid flow, according to an embodiment.

FIG. 1B is a diagram of a system for electrically controlling combustion fluid flow, according to another embodiment.

FIG. 2 is a diagram of a flow control electrode including a tube defining an aperture, according to an embodiment.

FIG. 3 is a diagram of a flow control electrode including a plate disposed adjacent to an aperture, according to an embodiment.

FIG. 4 is a diagram of a flow control electrode including a mesh disposed adjacent to an aperture, according to an embodiment.

FIG. 5 is a diagram of a flow control electrode including a plate and a tube in electrical communication with the plate, according to an embodiment.

FIG. 6 is a diagram of a flow control electrode embedded in a combustion fluid flow barrier, according to an embodiment.

FIG. 7 is a diagram of a combustion fluid flow barrier formed as a flame barrier, according to an embodiment.

FIG. 8 is a diagram of a combustion fluid flow barrier formed as a perforated flame holder, according to an embodiment.

FIG. 9 is a diagram of a combustion fluid flow barrier formed as an exhaust gas recirculation (EGR) barrier, according to an embodiment.

FIG. 10 is a diagram of a combustion fluid flow barrier formed as a combustion air damper, according to an embodiment.

FIG. 11 is a flow chart showing a method for electrically controlling combustion fluid flow, according to an embodiment.

DETAILED DESCRIPTION

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.

FIGS. 1A and 1B are diagrams of a system 100, 101 for electrically controlling combustion fluid flow. The system 100, 101 includes a charge generator 102 configured to apply a charge or voltage to a combustion fluid flow corresponding to a combustion reaction 104. A combustion fluid flow barrier 106 defines at least one aperture 108 therethrough. According to embodiments, the combustion fluid flow barrier 106 can include a body that defines a plurality of apertures and which forms a perforated flame holder or perforated reaction holder, wherein the plurality of apertures are configured to collectively carry the combustion reaction 104.

Various embodiments of bodies defining apertures configured to collectively carry a combustion reaction are contemplated. Some contemplated embodiments are described in International PCT Patent Application No. PCT/US2014/016626 entitled “SELECTABLE DILUTION LOW NOx BURNER” filed on Feb. 14, 2014, International PCT Patent Application No. PCT/US2014/016628 entitled “PERFORATED FLAME HOLDER AND BURNER INCLUDING A PERFORATED FLAME HOLDER” filed on Feb. 14, 2014, International PCT Patent Application No. PCT/US2014/016632 entitled “FUEL COMBUSTION SYSTEM WITH A PERFORATED REACTION HOLDER” filed on Feb. 14, 2014 and International PCT Patent Application No. PCT/US14/16622 entitled “STARTUP METHOD AND MECHANISM FOR A BURNER HAVING A PERFORATED FLAME HOLDER” filed on Feb. 14, 2014; each of which, to the extent not inconsistent with the disclosure herein, is incorporated by reference.

At least one flow control electrode 110 is operatively coupled to the at least one aperture 108. A voltage source 112 is operatively coupled to the flow control electrode 110. A controller 114 is configured to control an application of one or more voltages from the voltage source 112 to the flow control electrode 110. According to an embodiment, the system 100, 101 includes a burner 116.

The charge generator 102 can be configured to apply a charge or voltage at a first polarity to the combustion fluid flow. The controller 114 can be configured to cause the voltage source 112 to apply a voltage at the first polarity to the flow control electrode 110 to impede flow of the combustion fluid flow through the at least one aperture 108. Additionally or alternatively, the controller 114 can be configured to cause the voltage source 112 to not apply a voltage to the flow control electrode 110 to allow flow of the combustion fluid flow through the at least one aperture 108, can be configured to cause the voltage source 112 to hold the flow control electrode 110 at voltage ground to attract flow of the combustion fluid flow through the at least one aperture 108 and/or can be configured to cause the voltage source 112 to apply a voltage at a second polarity opposite from the first polarity to the flow control electrode 110 to attract flow of the combustion fluid flow through the at least one aperture 108.

Referring to FIG. 1B, according to an embodiment, the controller 114 is configured to control the application of charge or voltage to the combustion fluid flow by the charge generator 102. A second voltage source 118 can be operatively coupled to the charge generator 102. The controller 114 can also be operatively coupled to the second voltage source 118. The controller 114 can be configured to control the application of voltage from the second voltage source 118 to the charge generator 102.

Referring to FIGS. 1A and 1B, the at least one aperture 108 can include a plurality of apertures 108. The at least one flow control electrode 110 can be configured to control combustion fluid flow through the plurality of apertures 108. The plurality of apertures can be configured to collectively hold a combustion reaction, with the flow control electrode(s) being configured to affect the flow rate of fuel and air (examples of combustion fluids) through the plurality of apertures 108. The flow control electrode 110 can include an electrical conductor. According to another embodiment, the flow control electrode 110 can include a semiconductor. The flow control electrode 110 can be configured to control passage of various combustion fluids through the aperture 108. For example, the flow control electrode 110 may control passage of a flame, flue gas, and/or combustion air through the aperture 108.

FIGS. 2-6 are diagrams of flow electrodes 110 according to various embodiments. Referring to the embodiment 200 of FIG. 2, the flow control electrode 110 can include a tube 202 defining the aperture 108. Referring to the embodiment 300 of FIG. 3, the flow control electrode 110 can include a plate 302 disposed adjacent to the aperture 108. Referring to the embodiment 400 of FIG. 4, the flow control electrode 110 can include a mesh 402 disposed adjacent to the aperture 108. Referring to the embodiment 500 of FIG. 5, the flow control electrode 110 can include a plate 302 and a tube 202 in electrical communication with the plate 302. The tube 202 can define the aperture 108. Referring to the embodiment 600 of FIG. 6, the flow control electrode 110 can be embedded in the combustion fluid flow barrier 106.

Optionally, a counter-electrode can be arranged relative to an energized electrode to cause a flow or counter-flow of ionic wind through the aperture(s) 108. For example, the electrode 202 of FIG. 2 can be combined with an electrode 302, 402, shown respectively in FIGS. 3 and 4, to form an electrode/counter-electrode pair. Similarly, the electrode 302 of FIG. 3 can be combined with the electrode 402 of FIG. 4 as an electrode/counter-electrode pair. The relative potentials of an electrode/counter-electrode pair may be interchangeable and may be selected to enhance flow (and thereby entrainment of combustion fluid) through the aperture 108 or to restrict flow (e.g., by “blowing upstream”) of combustion fluid through the aperture 108. Optionally one of the electrodes may be configured as an ion-emitting (corona) electrode to increase ion density above the ion density provided by a charge generator 102.

FIG. 7 is a diagram of a combustion fluid flow barrier 106 formed as a flame barrier 702 configured to separate a primary combustion region 704 from a secondary combustion region 706, according to an embodiment 700. The primary combustion region 704 receives primary fuel from a primary fuel nozzle 708 configured to output a primary fuel jet 710 toward the flame barrier 702. A primary combustion reaction can occur in a region including a groove 712 contiguous with the primary combustion region 704. For example, the primary combustion reaction can act as heat source for igniting a secondary combustion reaction. The secondary combustion region 706 can receive secondary fuel from a secondary fuel nozzle 714 configured to output a secondary fuel jet 716 to at least partially impinge on the flame barrier 702. Fuel flow to the primary and secondary fuel nozzles 708, 714 can be controlled or measured by a fuel valve or flow sensor 718. The fuel valve or flow sensor 718 can be operatively coupled to a controller 114 configured to control fuel flow via an actuated fuel valve 718 or to receive fuel flow data from a fuel flow sensor 718.

A plurality of apertures 108 form passages 720, 722 between the primary combustion region 704 and the secondary combustion region 706. According to an embodiment, passage(s) 720 between the primary combustion region 704 and the secondary combustion region 706 provide selective heat communication between the groove 712 or a surface adjacent to the primary combustion region 704 and a substantially vertical surface 724 of the flame barrier 702. According to another embodiment, a passage 722 between the primary combustion region 704 and the secondary combustion region 706 provides selective communication between the primary combustion region 704 and a substantially horizontal surface 726 of the flame barrier 702. The substantially horizontal surface 726 can act as a secondary flame holding surface. Embodiments can include both horizontal passages 720 and vertical passages 722.

In the embodiment 700, the flow control electrode(s) 110 is configured to control ignition in the secondary combustion region 706.

The combustion fluid flow barrier 106 can include a bluff body configured to selectively support a flame (corresponding to the secondary combustion reaction, not shown). The flow control electrode 110 is configured to cause the flame to be supported by the bluff body when the combustion fluid is attracted or allowed to flow through the at least one aperture 108, 720, 722. The flow control electrode 110 is also configured to cause the flame to not be supported by the bluff body when the combustion fluid is impeded from flowing through the at least one aperture 108, 720, 722. In operation, a charge generator 102 is energized by the voltage source 112 to cause the primary combustion reaction to carry a charge or voltage at a first polarity. During start-up, for example, the flow control electrodes can be raised to a voltage having a second polarity opposite to the first polarity to cause flames from the primary combustion reaction to flow through the aperture(s) 108, 720, 722 to ignite a secondary combustion reaction proximate to the combustion fluid barrier 702 and to be held by the surface 726. After the system is warmed up, it may be desirable to ignite the secondary combustion reaction at a different location. For example, delaying ignition can allow greater secondary fuel dilution, which can result in lower oxides of nitrogen (NOx) output. To delay ignition, the controller 114 can cause the voltage source 112 to electrically energize the flow control electrode(s) 110 to a voltage having the same polarity as the charge applied to the primary combustion reaction by the charge generator(s) 102. Applying a repelling voltage to the flow control electrode(s) 110 can act to effectively increase resistance to combustion fluid (in this case, flame) flow through the aperture(s) 720, 722, thus reducing the probability of the primary combustion reaction delivering sufficient heat to the secondary combustion reaction to ignite the secondary combustion reaction proximate the surfaces 724, 726 of the flame barrier 702.

According to embodiments, the charge polarity placed on the primary combustion reaction by the charge generator(s) 102 can include an alternating charge. The flow control electrode(s) 110 can operate similarly to the description above by placing an in-phase voltage on the flow control electrode(s) 110 to reduce primary flame penetration of the flame barrier 702, or by placing an approximately 180° out-of-phase voltage on the flow control electrode(s) 110 to increase primary flame penetration of the flame barrier 702.

FIG. 8 is a diagram of an embodiment 800 wherein the combustion fluid flow barrier 106 includes a perforated flame holder 802 configured to hold a flame corresponding to the combustion reaction 104, according to an embodiment. For example, the perforated flame holder 802 of the embodiment 800 can be combined with the embodiment 700 shown in FIG. 7 by supporting the perforated flame holder 802 above the flame barrier 702. The perforated flame holder 802 was found to support a lower NOx-output combustion reaction than a combustion reaction held by the top surface 726 of the flame barrier 702.

The at least one aperture 108 can include a plurality of perforations 804 defined by the perforated flame holder 802. The controller 114 can be configured to cause the at least one flow control electrode 110 to selectively impede combustion fluid flow through the plurality of perforations 804 to cause the flame to be held at the edges of the perforated flame holder 802, and can also be configured to cause the at least one flow control electrode 110 to selectively allow or attract combustion fluid flow through the plurality of perforations 804 to cause the flame to flow through the perforations 804. For example, the controller 114 can be configured to cause the at least one flow control electrode 110 to selectively impede combustion fluid flow through a portion of the perforations 804 corresponding to a fuel turn-down. For example, the controller 114 can be configured to cause the at least one flow control electrode 110 to selectively allow and/or attract combustion fluid to flow through all or a portion of the perforations 804 proportional to a fuel flow rate.

According to embodiments, the charge polarity placed on fuel, air, flame, or other combustion fluid flow by the charge generator(s) 102 can include an alternating charge. The flow control electrode(s) 110 can operate similarly to the description above by placing an in-phase voltage on the flow control electrode(s) 110 to reduce flow through the perforations 804 in the flame holder 802, or by placing an approximately 180° out-of-phase voltage on the flow control electrode(s) 110 to increase flow through the perforations 804 in the flame holder 802.

FIG. 9 is a sectional diagram of a combustion fluid flow barrier 106 formed as an exhaust gas recirculation (EGR) barrier 902 configured to selectively recycle flue gases 904 from a combustion reaction 104, according to an embodiment 900. The aperture 108 can include a plurality of apertures 108 defined by the EGR barrier 902. A controller 114 can be configured to cause the flow control electrode 110 to selectively impede combustion fluid flow through the plurality of apertures 108 to cause the EGR barrier 902 to increase a proportion of flue gases recycling to the combustion reaction 104. Similarly, the controller 114 can be configured to cause the flow control electrode 110 to selectively allow and/or attract combustion fluid flow through the plurality of apertures 108 to reduce the portion of flue gases recycled to the combustion reaction 104. The controller 114 can be configured to cause the at least one flow control electrode 110 to selectively impede combustion fluid flow through a portion of the apertures 108 corresponding to a fuel turn-down, to selectively allow combustion fluid flow through a portion of the apertures 108 proportional to a fuel flow rate, and/or selectively attract combustion fluid flow through a portion of the apertures 108 proportional to a fuel flow rate.

According to embodiments, the charge polarity placed on the primary combustion reaction by the charge generator(s) 102 can include an alternating charge. The flow control electrode(s) 110 can operate similarly to the description above by placing an in-phase voltage on the flow control electrode(s) 110 to decrease exhaust gases penetrating the EGR barrier 902 to increase the portion of recycled exhaust gases. Similarly, placing an approximately 180° out-of-phase voltage on the flow control electrode(s) 110 will increase exhaust gas flow through the EGR barrier 902 to decrease the portion of recycled exhaust gases 904.

FIG. 10 is a sectional diagram of a combustion fluid flow barrier 106 including a combustion air damper 1002 configured to select a rate of combustion air flow 1004 to a combustion reaction 104, according to an embodiment 1000. The at least one aperture 108 can include a plurality of apertures 108 defined by the combustion air damper 1002. A controller 114 can be configured to cause the at least one flow control electrode 110 to selectively impede combustion air flow through the plurality of apertures 108 to cause the combustion air damper 1002 to reduce the rate of combustion air flow 1004 to the combustion reaction 104. Similarly, the controller 114 can be configured to cause the at least one flow control electrode 110 to selectively allow or attract combustion fluid (combustion air) flow through the plurality of apertures 108 to cause the combustion air damper 1002 to increase a rate of combustion air flowing to the combustion reaction 104. Additionally or alternatively, the controller 114 can be configured to cause the at least one flow control electrode 110 to selectively impede, allow, or attract combustion air flow through a portion of the apertures 108 corresponding to a fuel turn-down. According to an embodiment of the system 1000 (as illustrated in FIG. 10), the flow control electrode(s) 110 can be configured to control a flow of combustion air (or (not shown) gaseous fuel) into a mixing volume 1006 of a premixer configured to support a premixed combustion reaction 104.

As with the embodiments described above, the charge polarity placed in the combustion air by the charge generator(s) 102 can include an alternating charge. The flow control electrode(s) 110 can operate similarly to the description above by placing an in-phase voltage on the flow control electrode(s) 110 to decrease combustion air flow through the combustion air damper 1002, or by placing an approximately 180° out-of-phase voltage on the flow control electrode(s) 110 to increase combustion air flow through the combustion air damper 1002.

FIG. 11 is a flow chart showing a method 1100 for electrically controlling combustion fluid flow, according to an embodiment. Beginning at step 1102, electrical charges are output to a combustion fluid to form a charged combustion fluid. Proceeding to step 1104 a body is supported defining a plurality of apertures aligned to receive a flow of the charged combustion fluid. Proceeding to step 1110, a control voltage is applied to a control electrode disposed adjacent to the plurality of apertures. Finally, in step 1112, a flow of the charged combustion fluid through the plurality of apertures is affected with an electrical interaction between the charged combustion fluid and the control voltage carried by the control electrode.

Outputting electrical charges into a combustion fluid in step 1102 can include emitting charges with a corona electrode into a non-conductive combustion fluid. For example, the charges can be emitted into fuel, air, or a fuel and air mixture upstream from the apertures and control electrode. According to another embodiment, outputting electrical charges into a combustion fluid includes conducting charges from a charge electrode into a conductive combustion fluid. For example a charge generator can include a charge electrode that is in contact with a flame. Flames are relatively conductive.

The charged combustion fluid can include a fuel mixture, such as a fuel and air mixture. The charged combustion fluid can additionally or alternatively include a flue gas. The charged combustion fluid can additionally or alternatively include combustion air. The charged combustion fluid can additionally or alternatively include a flame.

As described above, various control scenarios are contemplated.

In one embodiment, outputting electrical charges to the combustion fluid includes outputting electrical charges having a first polarity and applying a control voltage to the control electrode includes applying a voltage at a second polarity the same as the first polarity. Affecting a flow of the charged combustion fluid through the plurality of apertures with an electrical interaction between the charged combustion fluid and the control voltage carried by the control electrode can include electrostatically repelling the electrical charges from the control electrode to attenuate the flow of charged combustion fluid through the apertures.

In another embodiment, outputting electrical charges to the combustion fluid includes outputting electrical charges having a first polarity and applying a control voltage to the control electrode comprises applying a voltage at a second polarity opposite to the first polarity. Affecting a flow of the charged combustion fluid through the plurality of apertures with an electrical interaction between the charged combustion fluid and the control voltage carried by the control electrode can include electrostatically attracting the electrical charges to the control electrode to enhance the flow of charged combustion fluid through the apertures.

In another embodiment, outputting electrical charges to the combustion fluid includes outputting electrical charges having a first polarity and applying a control voltage to the control electrode includes applying a voltage ground to the control electrode. Affecting a flow of the charged combustion fluid through the plurality of apertures with an electrical interaction between the charged combustion fluid and the control voltage carried by the control electrode can include electrostatically attracting the electrical charges to the control electrode to enhance the flow of charged combustion fluid through the apertures.

The method 1100 can further include operating a voltage source to output the control voltage.

Optionally, the method 1100 can include step 1106, wherein a combustion parameter is sensed. The method can also include step 1108, wherein the control voltage is selected responsive to the sensed combustion parameter. The control voltage can be set by controller and/or can be manually set by a system operator.

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.

Claims

1. A method for electrically controlling combustion fluid flow, comprising: outputting electrical charges to a combustion fluid to form a charged combustion fluid;supporting a body defining a plurality of apertures aligned to receive a flow of the charged combustion fluid;applying a control voltage to a control electrode disposed adjacent to the plurality of apertures; andaffecting a flow of the charged combustion fluid through the plurality of apertures with an electrical interaction between the charged combustion fluid and the control voltage carried by the control electrode.

2. The method for electrically controlling combustion fluid flow of claim 1, wherein outputting electrical charges into a combustion fluid further comprises: emitting charges with a corona electrode into a non-conductive combustion fluid.

3. The method for electrically controlling combustion fluid flow of claim 1, wherein outputting electrical charges into a combustion fluid further comprises: conducting charges from a charge electrode into a conductive combustion fluid.

4. The method for electrically controlling combustion fluid flow of claim 1, wherein the charged combustion fluid comprises a fuel mixture.

5. The method for electrically controlling combustion fluid flow of claim 4, wherein the charged combustion fluid comprises a fuel and air mixture.

6. The method for electrically controlling combustion fluid flow of claim 1, wherein the charged combustion fluid comprises a flue gas.

7. The method for electrically controlling combustion fluid flow of claim 1, wherein the charged combustion fluid comprises combustion air.

8. The method for electrically controlling combustion fluid flow of claim 1, wherein the charged combustion fluid comprises a flame.

9. The method for electrically controlling combustion fluid flow of claim 1, wherein outputting electrical charges to the combustion fluid comprises outputting electrical charges having a first polarity; wherein applying a control voltage to the control electrode comprises applying a voltage at a second polarity the same as the first polarity; andwherein affecting a flow of the charged combustion fluid through the plurality of apertures with an electrical interaction between the charged combustion fluid and the control voltage carried by the control electrode comprises electrostatically repelling the electrical charges from the control electrode to attenuate the flow of charged combustion fluid through the apertures.

10. The method for electrically controlling combustion fluid flow of claim 1, wherein outputting electrical charges to the combustion fluid comprises outputting electrical charges having a first polarity; wherein applying a control voltage to the control electrode comprises applying a voltage at a second polarity opposite to the first polarity; andwherein affecting a flow of the charged combustion fluid through the plurality of apertures with an electrical interaction between the charged combustion fluid and the control voltage carried by the control electrode comprises electrostatically attracting the electrical charges to the control electrode to enhance the flow of charged combustion fluid through the apertures.

11. The method for electrically controlling combustion fluid flow of claim 1, wherein outputting electrical charges to the combustion fluid comprises outputting electrical charges having a first polarity; wherein applying a control voltage to the control electrode comprises applying a voltage ground to the control electrode; andwherein affecting a flow of the charged combustion fluid through the plurality of apertures with an electrical interaction between the charged combustion fluid and the control voltage carried by the control electrode comprises electrostatically attracting the electrical charges to the control electrode to enhance the flow of charged combustion fluid through the apertures.

12. The method for electrically controlling combustion fluid flow of claim 1, further comprising: operating a voltage source to output the control voltage.

13. The method for electrically controlling combustion fluid flow of claim 1, further comprising: sensing a combustion parameter; andselecting the control voltage responsive to the sensed combustion parameter.