GB2303696A - Fuel burner with rotating flame - Google Patents

Abstract

A fuel burner (10) having a plurality of arcuately spaced oxidant and fuel outlets (18, 20) and valve means for causing supply of oxidant and fuel from successive sequential outlets (18, 20) so as to produce a rotating flame of combustible fuel/oxidant mixture which extends in a spiral manner away from said outlets.

Description

A FUEL BURNER The present invention relates to fuel burners and relates particularly to a fuel burner of the type that creates a rotating flame in the combustion zone thereof.

Presently known burners often employ fuel and oxidant outlets that, in operation, act to create a somewhat tight, small diameter flame that is difficult to use in applications where an even spread of heat is required over a large surface area. An additional problem associated with such burners resides in the fact that, because the flame is so tight, it is difficult to ensure that sufficient oxidant penetrates the fuel stream to ensure complete combustion takes place.

It is an object of the present invention to provide a fuel burner which reduces and possibly eliminates the problems associated with the above-mentioned design.

Accordingly, the present invention provides a fuel burner comprising: one or more fuel outlets; a plurality of arcuately spaced oxidant outlets; fuel ignition means; and first valve means for causing a flow of fuel to issue from said one or more fuel outlets; second valve means for causing discrete slugs of oxidant to be dispensed from sequential oxidant outlets for mixing with said fuel thereby to create a rotating flame of combustible fuel/oxidant mixture which extends in a spiral manner away from said outlets.

It will be appreciated that such a burner is capable of producing a rapidly rotating flame which facilitates efficient mixing of the fuel/oxidant mixture.

Preferably, said oxidant outlets are circumferentially spaced around a circumference radially-outward of said fuel outlet or outlets.

Conveniently, said fuel outlet or outlets comprise the fuel outlet or outlets of an oxy-fuel burner.

Advantageously, said oxidant outlets are positioned along one or more curves or involutes extending from a central longitudinally extending axis of said burner.

Preferably, the burner includes a fuel outlet for each oxidant outlet and associated fuel and oxidant outlets are positioned immediately adjacent each other.

In one arrangement, said valve means comprises a plurality of solenoid actuated valves, each valve being associated with an individual outlet of allowing or inhibiting flow therefrom.

In an alternative arrangement, said valve means comprises a rotating seal plate valve.

In a particularly advantageous arrangement, the burner includes flow control means for controlling the quantity of oxidant and/or fuel through said outlets during supply therefrom.

In some arrangements the flow control means comprises means for varying the speed of rotation of said plate valve.

Advantageously, the burner includes rate control means for controlling the rate at which discrete slugs of oxidant are dispensed from said outlets.

Preferably, one or more of said oxidant and/or fuel outlets are angled so as to impart a tangential component to the direction of flow as said oxidant and/or fuel issues from said outlet.

The present invention will now be more particularly described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a general view of a burner according to some aspects of the present invention; Figure 2 is a cross-sectional view of the burner shown in Figure 1; Figures 3 to 6 are views in the direction of arrow V of Figure 1 and illustrate various alternative fuel/oxidant outlet arrangements; Figure 7 is a cross-sectional view of a burner incorporating a rotating seal plate valve; Figure 8 is a cross-sectional view of a burner incorporating an alternative form of seal plate valve; Figure 9 is a view in the direction of arrows AA of Figure 8; Figure 10 is a view in the direction of arrows BB of Figure 8; and Figure 11 is a cross-sectional view of a burner according to the present invention and incorporating optional plenum chamber fuel/oxidant supply and a water cooling jacket.

Turning now to Figures 1 and 2, a burner 10 in accordance with the present invention includes an endplate 12 and optional sidewalls 14, each of which may be provided with a protective fire resistant refractory surface shown generally at 16. The endplate 12 is provided with a plurality of arcuately spaced oxidant (air, oxygen or oxygen enriched air - hereinafter referred to as oxidant) and fuel outlets shown generally at 18 and 20 but best seen with reference to Figures 3 to 6. Each outlet 18, 20 is provided with a valve arrangement (detailed in Figures 2, 7 and 8) for inhibiting or allowing the flow of fluid therethrough. For the avoidance of doubt, arcuately spaced is considered to cover arrangements where the outlets are either spaced around a common circumference (Figures 3 and 4) or angularly spaced from each other and positioned on different circumferences (Figures 5 and 6).In the Figure 2 embodiment, the valves comprise simple solenoid actuated valves 22, 24 connected by actuation lines 26 to 32 to controller 34 for facilitating the opening and closing of said valves in a manner to be discussed in detail later herein. Figures 7 and 8 illustrates an alternative form of valve arrangement in which use is made of a rotating plate valve of one or two part construction. In the Figure 7 arrangement, a single part rotating plate valve 40a is provided with oxidant and fuel passageways 42, 44 for allowing or inhibiting the flow of oxidant and fuel between supply pipes 46, 48 and outlets 18, 20. In operation, rotation of plate valve 40 in the direction of arrow R causes successive inlets to be placed in flow communication with supply pipes 46, 48 thereby allowing oxidant and fuel to issue from the outlets as shown by arrows 0 and F.At any one moment in time, only one pair of oxidant/fuel outlets is supplied, the remaining outlets being blocked by the main body of the valve. Clearly, in this arrangement, the valve acts to supply fuel and oxidant simultaneously, however, it will be appreciated that alternative arrangements may be provided without departing from the spirit of the present invention. For example, the positioning of the oxidant and fuel passageways 42, 44 may be such as to cause one or other of the fuel or oxidant components to be supplied in advance of the other.

Alternatively, or in addition, one or other of the passageways 42, 44 may be of the slotted type (as shown in Figure 9), thereby to facilitate the supply of oxidant and/or fuel over a prolonged period of time. One possible arrangement might be to provide an elongate.slot arrangement for the oxidant supply which allows oxidant to be supplied before, during and after any slug of fuel thereby to provide an oxygen 'envelope' which surrounds the fuel as it enters the burner body and facilitates more complete combustion thereof. Alternatively, one might provide two oxidant outlets for each fuel outlet, thereby facilitating the late combining of at least part of the oxidant and the fuel in a manner which helps promote 'staged combustion' within the burner thereby facilitating more complete combustion of the fuel. An actuator, in the form of, for example, motor and gear arrangement 48, 50 is provided for rotating plate valve 40 in the direction of arrow R.

Figure 8 illustrates a two part valve arrangement, one valve part being provided for the oxidant-and the fuel supply respectively. Outer valve part 50 comprises a ring which rotates around an inner disk valve part 52 as illustrated in Figure 9. Each valve part 50, 52 is provided with a passageway 42, 44 as described above. Actuators in the form of, for example, motor and gear arrangements 54, 56 and 58, 60 respectively are provided for driving each valve part 50, 52 independently of the other in a manner to be described in detail later herein. Motors 54, 58 are linked for control to controller 34 via lines 62, 64.

Operation of the Figure 8 arrangement is somewhat similar to that described above in respect of the Figure 7 arrangement save for the fact that independent motors 54, 58 may be operated at different speeds or operated to cause oxidant and fuel to be supplied out of phase with each other. For example, operation may be such as to cause oxidant to be supplied from an outlet in advance of or behind the outlet from which, at any one moment in time, fuel is being supplied. Such an arrangement would cause a slight delay in the combustion process taking place downstream of the outlets.

Alternatively, one might provide two oxidant passageways 42 for each fuel passageway 44. Such as, for example, as shown in Figure 10 in which a pair of diametrically opposed oxidant passageways 42 are provided. The oxidant supplied to the outlet remote from that to which the slug of fuel is supplied will combine with the fuel somewhat later in the combustion process than the oxidant supplied immediately adjacent the fuel outlet, thereby to achieve a form of 'staged combustion' within the burner and facilitating more complete combustion of the fuel in a manner well known to those skilled in the art and therefore not described further herein.

Returning now briefly to Figures 3 to 6, it will be appreciated that the present invention may be used in conjunction with a number of different oxidant/fuel supply arrangements. For example, in Figure 3, outer oxidant outlets 18 may be used in conjunction with a conventional oxy-fuel burner 70 situated radially inward thereof. The oxy-fuel burner 70 being provided with its own oxidant supply outlets 72 and a fuel supply outlet 74 which also forms fuel outlet 20 of the present invention. In such an arrangement the sequential firing of outer oxidant supply outlets 18 effectively acts to provide a rotating spiral of oxidant for subsequent combustion in a normal or 'staged' manner. Figure 3 also illustrates a further possible feature, namely that of angled outlets 18 (shown dotted).Such angling of the outlets 18 as they pass through endwall 12 acts to provide a positive swirl action which provides the oxidant with a tangential component T as soon as it enters the main body of the combustion zone 17. Figure 4 illustrates a simpler arrangement in which fuel and oxidant outlets are provided in pairs circumferentially spaced around an outer circumference of the burner body 10. In this and other arrangements, it might be desirable to angle the fuel outlets 20 in the same manner as that described above in relation to the oxidant outlets. Again, the result would be to cause the fuel to have a tangential component t as soon as it issues from the outlet. Figure 5 provides a multiple swirl arrangement in which a central fuel outlet 20 is flanked by two (or more) rows of oxidant outlets 18.Each row extends in a generally curved or involute manner away from fuel outlet 18, thereby to provide for the production of multiple rotating oxidant streams extending in the direction of arrows S and S1. An alternative form of double spiral arrangement is shown in Figure 6 which is generally the same as that shown in Figure 7 save for the fact that the central fuel outlet 20 is replaced by a fuel outlet 20 associated with each oxidant outlet 18.

Operation of the present invention is fairly simple and comprises the step of operating the valving of Figures 2 and 7 to 10 in a manner which results in the generation of a rotating spiral of oxidant and fuel issuing from outlets 18, 20. This maelstrom of oxidant/fuel progresses along the combustion zone and results in the creation of a flame which allows for more effective combustion than in many presently known arrangements. More specifically, the valve arrangements are operated as described above, so as to cause fuel and oxidant to be combined at one or a number of points within the combustion zone, thereby to facilitate a mixing process which effectively eliminates the central core of a conventional flame and allows oxidant to react with that portion of the fuel which might otherwise be shielded therefrom.

Creation of the above effect is achieved in the Figure 2 embodiment by initiating operation of controller 34 such that it opens and closes various valves 22,24 so as to cause discrete slugs 90 of fuel/oxidant to issue from outlets 20, 18 as shown in Figure 1. The effect of sequential operation of the valves is to create a rotating spiral of fuel/oxidant that extends in the direction of arrow RS. Such a spiral is, in effect, a tubular flame in which the fuel is exposed to a much greater volume of oxidant than might be achieved with a tight flame of the prior art. Obviously, controller 34 may be used to open more than one oxidant supply at any one time and hence cause the issuance of oxidant/fuel slugs in the same manner as that described in relation to 'staged combustion' as mentioned during the operation of the rotating plate valve arrangements of the present invention.

One aspect of the present invention not mentioned earlier herein relates to the ability to speed-up or slowdown the rate at which the oxidant and/or fuel is supplied to outlets 12,20. In the Figure 2 embodiment, this is simply achieved by initiating a more rapid or slower firing sequence of valves 22, 24 through controller 34 which may be programmable to provide "fuel richS and "fuel lean* profiles and also altering the rate at which the individual valves are operated thereby to provide a smoother flame profile. In the Figure 7 embodiment, one simply initiates control over motor 48 such that it rotates plate valve 40a either more rapidly or more slowly than a predetermined normal speed.

More rapid operation will produce a smoother flame whilst slower operation will result in a large quantity of fuel and/or oxidant being supplied during any one valve operation and hence a hotter but possibly less stable flame could be produced. A much greater degree of control is available in the Figure 8 embodiment in which valve positions 50,52 may be operated somewhat independently of each other thereby facilitating numerous fuel/oxidant profiles. For example, controller 34 may be programmed such that the speed of portions 50 or 52 is varied throughout one complete revolution, or part thereof. In particular, it would be possible to slow down the oxidant valve portion 50 during any one supply phase such that it provides a somewhat greater quantity of oxidant than would be supplied in normal operation. Subsequently, it would be possible to speed up the valve portion 50 as it travels to its next supply phase by which time it will be back in phase with the fuel supply valve portion 52. Alternatively, the fuel supply valve portion 52 may be operated in this manner and hence excess fuel would be supplied. Indeed, one might operate the valve portions 50, 52 in combination with each other to produce "fuel rich" and "fuel lean" portions of flame. For example, it might be desirable to produce a flame having an oxidant rich bottom half or side, thereby causing or creating a hotter combination region adjacent an object to be heated or adjacent a region within a heating zone. Such arrangements being particularly useful in the melting of metals or glass, in which it is known to provide excess oxygen adjacent the melt, thereby to increase the heating effect.In a still further alternative arrangement, it would be possible to operate the oxidant and fuel supply in a contr-rotational manner, thereby to delay the point at which some of the oxidant and fuel combine and provide a further form of 'staged combustion'.

Other features of the present invention are illustrated in Figures 11 and 12. In the Figure 11 arrangement, single oxidant and fuel supply pipes 46, 48 are coupled to a distribution manifold 70 in a manner which facilitates supply to each and every oxidant/fuel outlet 18, 20. The manifold itself 70 comprises oxidant and fuel inlets 72, 74 each of which communicate with its own internal distribution ring 76, 78. Each distribution ring 76, 78 is provided with a plurality of outlets 80, 82 one outlet being provided in flow communication with each of outlets 18, 20. Outlets 80, 82 effectively act to replace the plurality of supply pipes 46, 48 associated with the Figures 7 and 8 embodiments. Operatiorr of this arrangement is the same as described above, save for the fact that the rotating portions of valve 40b communicate for fluid flow between outlets 80, 82 and 18, 20 rather than supply pipes 46, 48 and outlets 18, 20. Also disclosed in Figure 11 is a cooling jacket arrangement 90 in the form of outer sleeve 92 which surrounds extended fuel and oxidant supply outlets 18, 20. In operation, cooling fluid C is pumped from inlet 94 and out of outlet 96 as heated fluid H. Such a cooling arrangement would be particularly advantageous when the burner is installed in, for example, the wall 100 of a furnace 110 and is therefore subjected to the high temperatures created within the furnace 110. Figure 12 illustrates a similar installation modification for the arrangement shown in Figure 2 save for the fact that no cooling jacket 90 is provided.

Claims (11)

1. A fuel burner comprising: one or more fuel outlets; a plurality of arcuately spaced oxidant outlets; fuel ignition means; and first valve means for causing a flow of fuel to issue from said one or more fuel outlets; second valve means for causing discrete slugs of oxidant to be dispensed from sequential oxidant outlets for mixing with said fuel thereby to create a rotating flame of combustible fuel/oxidant mixture which extends in a spiral manner away from said outlets.

2. A fuel burner as claimed in Claim 1 in which said oxidant outlets are circumferentially spaced around a circumference radially outward of said fuel outlet or outlets.

3. A fuel burner as claimed in Claim 2 in which said fuel outlet or outlets comprise the fuel outlet or outlets of an oxy-fuel burner.

4. A fuel burner as claimed in Claim 1 in which said oxidant outlets are positioned along one or more curves or involutes extending from a central longitudinally extending axis of said burner.

5. A fuel burner as claimed in any one of Claims 1, 2 or 4 including a fuel outlet for each oxidant outlet and in which associated fuel and oxidant outlets are positioned immediately adjacent each other.

6. A fuel burner as claimed in any one of Claims 1 to 5 in which said valve means comprises a plurality of solenoid actuated valves, each valve being associated with an individual outlet of allowing or inhibiting flow therefrom.

7. A fuel burner as claimed in any one of Claims 1 to 5 in which said valve means comprises a rotating seal plate valve.

8. A fuel burner as claimed in any one of Claims 1 to 7 including flow control means for controlling the quantity of oxidant and/or fuel through said outlets during supply therefrom.

9. A fuel burner as claimed in Claim 8 when dependant upon any one of Claims 1 to 5 and 7 in which said flow control means comprises means for varying the speed of rotation of said plate valve.

10. A fuel burner as claimed in any one of Claims 1 to 9 including rate control means for controlling the rate at which discrete slugs of oxidant are dispensed from said outlets.

11. A fuel burner substantially as herein described with reference to and as illustrated in Figures 1 to 12 of the accompanying drawings.