FLAME CONTROL IN THE BUOYANCY-DOMINATED FLUID DYNAMICS REGION
A burner system includes a nozzle configured to emit a fuel stream for the support of a flame, and first and second electrodes, each configured to apply electrical energy to a flame supported by the nozzle. The first electrode is positioned in a momentum-dominated fluid dynamics region of the flame, while the second electrode is positioned in a buoyancy-dominated fluid dynamics region. Application of charges to the flame via the electrodes can be employed to control flame characteristics in the buoyancy-dominated fluid dynamics region, such as shape and position.
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The present application claims priority benefit from U.S. Provisional Patent Application No. 61/773,740, entitled “FLAME CONTROL IN THE BUOYANCY-DOMINATED FLUID DYNAMICS REGION”, filed Mar. 6, 2013; which, to the extent not inconsistent with the disclosure herein, is incorporated by reference.
TECHNICAL FIELDThe present disclosure relates generally to combustion systems, and more particularly, to electrode arrangements that affect flame shape and position.
BACKGROUNDCombustion systems are employed in a vast number of applications, in industry and commerce, and in private homes.
SUMMARYAccording to an embodiment, a method for controlling a characteristic of a flame in a burner system includes supporting a flame in a fuel stream and modifying a characteristic of the flame by application of electrical energy. The application of electrical energy includes applying a first electric charge to the flame at a first location that is upstream from a buoyancy-dominated flow region of the flame and applying a second electric charge to the flame at a second location that is downstream from a momentum-dominated flow region of the flame, such that the first and second electric charges interact.
According to another embodiment, a method for controlling a characteristic of a flame in a burner system includes supporting a flame in a fuel stream, identifying a flame holding region of the flame, a momentum-dominated flow region of the flame, and a buoyancy-dominated flow region of the flame, and modifying a characteristic of the flame by an application of electrical energy. The application of electrical energy includes applying a first electric charge to the flame at a first location that is upstream from the buoyancy-dominated flow region of the flame and applying a second electric charge to the flame at a second location that is downstream from the momentum-dominated flow region of the flame, such that the first and second electric charges interact.
According to another embodiment, a method for controlling a characteristic of a flame in a burner system includes, in a fuel stream, supporting a flame that is characterized by a momentum-dominated flow region and buoyancy-dominated flow region, each having dimensions sufficient for the application of electrical energy. A characteristic of the flame is modified by applying a first electric charge to the flame at a first location that is upstream from the buoyancy-dominated flow region of the flame and applying a second electric charge to the flame at a second location that is downstream from the momentum-dominated flow region of the flame, such that the first and second electric charges interact.
Non-limiting embodiments of the present disclosure are described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale.
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, which are not to scale or to proportion, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings and claims, are not meant to be limiting. Other embodiments may be used and/or other changes may be made without departing from the spirit or scope of present disclosure.
In many of the embodiments disclosed below, various electrodes are described as being configured to apply a charge, an electrical potential, or electrical energy to a flame. While these terms are not synonymous, they are often used interchangeably, as there is significant overlap in their respective meanings, and it is often difficult to distinguish between them, or to do one without doing the others. For the purposes of the present disclosure and claims, they can be construed as being synonymous, except where a term is more explicitly defined.
Various burner systems are disclosed as embodiments. In practice, these and other embodiments are elements of more extensive combustion systems used in industry and commerce as parts of, for example, boilers, refineries, smelters, foundries, commercial and residential HVAC systems, etc.
The term flame particle refers primarily to gaseous atoms and/or molecules that comprise the fluid within a flame, as well as the small solid particles that may be entrained within the flame.
A flame front 108 of the flame is located in the flame holding region R1. As fuel flows from the nozzle 102 in a downstream direction in the fuel stream 104 the flame front 108 is continually moving upstream. The velocity of the fuel stream 104 is a function of a number of factors, including the geometry of the nozzle 102 and the pressure of the fuel within the nozzle. Meanwhile, the flame propagation rate, i.e., the speed at which the flame front 108 moves upstream, depends upon the type of fuel, the amount of oxygen available, and the ambient temperature. When the flame propagation rate and the fuel stream velocity are equal, the flame 106 remains substantially stationary relative to the nozzle 102, and the flame is said to be stable. There are a number of structures and methods known in the art by which a stable flame can be obtained under many conditions and across a wide range of fuel stream velocities. According to the embodiments disclosed hereafter, the flame can be stabilized in accordance with any structure or method.
Within the momentum-dominated fluid dynamics region R2 of the flame 106, the velocity and vector of flame particles within the flame 106 are substantially determined by the velocity and vector associated with the fuel stream 104. In this region, the velocity of the flame particles is sufficiently high that other factors have little influence on their vector. However, as the flame particles move downstream, they lose velocity, and the buoyancy of the flame 106, relative to the denser surrounding gases, tends to push the flame upward.
As the flame particles move further downstream and continue to lose velocity, the direction of movement is increasingly dominated by flame buoyancy. As shown in
The shape of the flame 106, and the relative sizes of the three regions R1-R3, vary significantly, according to many factors. In some cases, the buoyancy-dominated fluid dynamics region R3 is nonexistent, or very nearly so, as in, for example, some welding torch flames. In these types of flames, the fuel is substantially consumed before the velocity has dropped to a level where buoyancy can exert a significant influence. In other cases, the momentum-dominated fluid dynamics region R2 is substantially nonexistent, as in the case of a candle flame or other flame in which little or no velocity is imposed on the fuel, so the flame velocity and vector are entirely controlled by other factors, including buoyancy.
As illustrated in the embodiments disclosed below, the inventors have recognized that application of electrical energy to the buoyancy-dominated fluid dynamics region R3 of a flame can be most effective in controlling flame characteristics such as shape, position, height, breadth, etc. Turning now to
The first electrode 202 is positioned adjacent to the flame 106 within the second region R2 and configured to apply a first electric charge C1 to the flame 106. For example, the first electrode 202 can be configured as an ion-emitting electrode, configured to introduce ions into the flame 106. Alternatively, the first electrode can be configured to apply an electrostatic charge to the flame 106, or to directly contact the flame and to apply a voltage potential to the flame, etc. Some different types of electrodes are shown and described with reference to various embodiments, but these are provided as examples, only. They do not represent all of the possible variations, nor are the embodiments limited to the specific electrode configurations shown or described. According to another embodiment, the voltage supply is electrically coupled to the nozzle 102, a portion of which functions as the first electrode. Where the term electrode is used in a claim, it is to be read on any structure that is capable of applying electrical energy to a flame, and is to be limited only by the express language of the claim.
The applied charge is shown in
In the embodiment of
It can also be seen in
According to a preferred embodiment, at least one of the first and second electrodes 202, 204 is separated from the flame 106 by a dielectric gap. This serves to reduce or prevent short circuits between the electrodes, which can consume a significant amount of energy. It is further preferred that if one of the electrodes in to be placed in contact with the flame, it is the first electrode 202 that is in contact, while the second electrode 204 is maintained with a dielectric gap. This enables variability in control of aspects such as flame shape and/or position. Because the strength of an electric field is controlled in part by the magnitude of a voltage difference across a dielectric gap, the position of the flame can be controlled by regulation of the voltage across the gap (or the sum of the gaps). On the other hand, if both electrodes make contact with the flame, the flame will remain in contact, even if the voltage difference is adjusted. Eliminating the ability to modify the flame position.
A fourth electrode 404 is also shown in the embodiment of
It may be advantageous, in some embodiments, to place both the first and the second electrodes within the third region R3. Accordingly, in various embodiments the first electrode is positioned above the transition point between the second and third regions R2 and R3 while according to others, it is positioned below.
Where the claims us the terms upstream, downstream, these and related terms are to be construed as referring to a position or location of the corresponding element with respect to another element, in relation to a flow that includes a fuel stream, a flame supported by the fuel stream, and combustion products from the flame. Where, for example, a first element is described as being upstream from a second element, the first element is closer, in relation to the flow, to a source of the fuel stream, such as, e.g., a fuel nozzle. In such an arrangement, the second element can also be described s being downstream from the first element.
While various aspects and embodiments have been disclosed, other aspects and embodiments may be contemplated. The various aspects and embodiments disclosed here 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 controlling a characteristic of a flame in a burner system, comprising:
- supporting a flame in a fuel stream; and
- modifying a characteristic of the flame by: applying a first electric charge to the flame at a first location that is upstream from a buoyancy-dominated flow region of the flame, and applying a second electric charge to the flame at a second location that is downstream from a momentum-dominated flow region of the flame, such that the first and second electric charges interact.
2. The method of claim 1, comprising identifying a transition point between the momentum-dominated flow region of the flame and the buoyancy-dominated flow region of the flame.
3. The method of claim 1, comprising identifying the buoyancy-dominated flow region of the flame, and selecting the second location to be within the buoyancy-dominated flow region.
4. The method of claim 1, comprising identifying the momentum-dominated flow region of the flame, and selecting the first location to be within the momentum-dominated flow region.
5. The method of claim 1, wherein the applying a first electric charge comprises charging the flame at a first polarity.
6. The method of claim 5 wherein the applying a second electric charge comprises generating an electric field between an electrode and the flame.
7. The method of claim 6, wherein the generating an electric field comprises:
- providing a dielectric gap between the electrode and the flame; and
- applying a voltage having a second polarity, opposite the first polarity, to the electrode.
8. The method of claim 5 wherein the charging the flame at a first polarity comprises: applying a voltage potential to an electrode in electrical contact with the flame.
9. The method of claim 8 wherein:
- the supporting a flame in a fuel stream comprises ejecting fuel from a nozzle; and
- the applying a voltage potential to an electrode in electrical contact with the flame comprises applying a voltage potential to the nozzle.
10. The method of claim 5 wherein the charging the flame at a first polarity comprises introducing ions into the flame.
11. The method of claim 10 wherein the introducing ions into the flame comprises:
- generating ions having the first polarity; and
- entraining the ions into the flame.
12. The method of claim 10 wherein the introducing ions into the flame comprises:
- ejecting ions from a corona electrode by applying a first voltage potential having the first polarity to a corona electrode positioned adjacent to the flame while simultaneously applying a second voltage potential having a second polarity, opposite the first polarity, to a counter electrode positioned adjacent to the flame on a side opposite the corona electrode; and
- entraining the ions into the flame.
13. The method of claim 1, wherein:
- the applying a first electric charge comprises applying a first electric charge having a first polarity; and
- the applying a second electric charge comprises applying a second electric charge having a second polarity, opposite the first polarity.
14. The method of claim 1 wherein:
- the applying a first electric charge comprises applying a first electric charge having a first polarity; and
- the applying a second electric charge comprises applying a first voltage having the first polarity to a first electrode positioned adjacent to the flame while applying a second voltage having a second polarity, opposite the first polarity, to a second electrode positioned adjacent to the flame on a side of the flame substantially opposite the first electrode.
15. The method of claim 1 wherein:
- the applying a first electric charge comprises applying a first electric charge having a first polarity; and
- the applying a second electric charge comprises forming an electric field across the flame at the second location, by applying a first voltage having the first polarity to a first electrode positioned adjacent to the flame while applying a second voltage having a second polarity, opposite the first polarity, to a second electrode positioned adjacent to the flame on a side of the flame substantially opposite the first electrode.
16. The method of claim 1, wherein the applying a second electric charge comprises: applying a second electric charge having a same polarity as the first electric charge.
17. The method of claim 1 wherein:
- the applying a first electric charge comprises applying a first voltage potential to a first electrode positioned adjacent to the flame at the first location; and
- the applying a second electric charge comprises applying a second voltage potential to a second electrode positioned adjacent to the flame at the second location.
18. The method of claim 17 wherein:
- the applying a first voltage potential comprises applying the first voltage potential having a first polarity to the first electrode; and
- the applying a second voltage potential comprises applying the second voltage potential having a second polarity, opposite the first polarity, to the second electrode.
19. The method of claim 1 wherein:
- the applying a first electric charge comprises applying a first voltage potential to a first electrode positioned adjacent to the flame at the first location and having annular shape; and
- the applying a second electric charge comprises applying a second voltage potential to a second electrode positioned adjacent to the flame at the second location.
20. The method of claim 1 wherein:
- the applying a first electric charge comprises applying a first voltage potential to a first electrode positioned adjacent to the flame at the first location; and
- the applying a second electric charge comprises applying a second voltage potential to a second electrode positioned adjacent to the flame at the second location and having an annular shape.
21. A method for controlling a characteristic of a flame in a burner system, comprising:
- supporting a flame in a fuel stream;
- identifying a flame holding region of the flame, a momentum-dominated flow region of the flame, and a buoyancy-dominated flow region of the flame;
- modifying a characteristic of the flame by: applying a first electric charge to the flame at a first location that is upstream from the buoyancy-dominated flow region of the flame, and applying a second electric charge to the flame at a second location that is downstream from the momentum-dominated flow region of the flame, such that the first and second electric charges interact.
22. A method for controlling a characteristic of a flame in a burner system, comprising:
- in a fuel stream, supporting a flame that is characterized by a momentum-dominated flow region and buoyancy-dominated flow region, each having dimensions sufficient for the application of electrical energy;
- modifying a characteristic of the flame by: applying a first electric charge to the flame at a first location that is upstream from the buoyancy-dominated flow region of the flame, and applying a second electric charge to the flame at a second location that is downstream from the momentum-dominated flow region of the flame, such that the first and second electric charges interact.
Type: Application
Filed: Mar 6, 2014
Publication Date: Sep 11, 2014
Applicant: ClearSign Combustion Corporation (SEATTLE, WA)
Inventors: JOSEPH COLANNINO (BELLEVUE, WA), IGOR A. KRICHTAFOVITCH (KIRKLAND, WA), DAVID B. GOODSON (BELLEVUE, WA), TRACY A. PREVO (SEATTLE, WA), CHRISTOPHER A. WIKLOF (EVERETT, WA)
Application Number: 14/200,011
International Classification: F23N 5/00 (20060101);