MXPA00001653A - Burner - Google Patents

Abstract

A burner for combusting gaseous mixture of gaseous fuel with a combustion supporting gas, such as oxygen or air, comprising a burner tube (11) open at one end (11') and closed at its other end (11") with a flame holder (30) at which fuel is burnt adjacent the open end (11'), the flame holder (30) being traversed by passageways (52, 54, 56, 58) for the gaseous mixture, the burner (10) having inlets (14, 16) adjacent the closed end (11") connected to combustion supporting gas and gaseous fuel supply lines, one of said lines having a control valve operable for controlling the size of the flame, the said one line having a pressure or flow transducer and the other line having a variable booster or restricter responsive to the transducer, for balancing air and fuel supplied to the burner (10) to ensure the gaseous mixture remains stoichiometric irrespective of the size of the flame and such that the lowest gaseous fuel mixture flow rate is at least as low as 1/60th the highest flow rate of the gaseous fuel mixture each passageway (52, 54, 56, 58) having a flared exit (60) at the end nearer the open end (11') of the burner (11) each passageway being dimensioned such that at the highest obtainable flow rate of gaseous fuel mixture the flames do not lift off from the flamer holder, at the lowest flow rate the velocity of the gaseous fuel mixture at some point within the passageway (52, 54, 56, 58) is sufficient to prevent flame back through the flame holder.

Description

BURNER FIELD OF THE INVENTION The invention relates to a gas burner suitable for use in incinerators, boilers, space heating apparatuses and furnaces, foundries or high temperature reactors used in the industry, for example. A burner incorporating the flame retainer is also highly suitable for use in a vertical evacuated outlet tube. BACKGROUND OF THE INVENTION The gas used as fuel can be any gas commonly used in gas burners, for example the gas can be butane, propane, natural gas and gases produced from hydrocarbons by the gasification of organic materials, such as waste or normal commercial or domestic waste. The burner presented below has been designed to ensure complete mixing of fuel and air or oxygen, and to admit them into a mixing chamber in the burner only in the stoichiometric proportion required by the fuel for its complete combustion, giving a stable flame with a rate of decrease of up to 60: 1, at least. A preferred burner for a gaseous fuel comprises a burner tube open at one end and closed at its other end and with a flame retainer in which the fuel burns adjacent to the open end, the flame retainer is traversed by passages for air and fuel to be consumed, the burner has entrances adjacent to the closed end for air or oxygen, and fuel, the inlets are provided with nozzles to separately supply air and fuel radially into the tube where a mixing zone is formed between the inlets and the flame retainer, the measuring nozzles have holes with cross-sectional areas related to the stoichiometric proportion of air-fuel for which the fuel burns completely. A burner of the present invention well tolerates large air / fuel changing ratios, that is, it has a high proportion of decreasing turn. Conventional burners have decreasing turn ratios of 4 or 5 to 1. Thus, the air and fuel supply rates can be reduced to a quarter or a fifth of the maximum capacity of such burners. In addition, the reduction results in instability of the flame, finally the flame fails and extinguishes. SUMMARY OF THE INVENTION The invention seeks to provide a burner with a much larger decreasing turn. It therefore provides a burner for burning gas mixtures of gaseous fuel with a combustion support gas, such as oxygen or air, comprising a burner tube open at one end and closed at its other end with a flame retainer where the fuel is burned adjacent to the open end, the flame retainer is traversed by passages for the gaseous mixture, the burner has entrances adjacent to the closed end connected to the supply lines of the combustion support gas and the gaseous fuel, one of the lines have a control valve operable to control the size of the flame, that line has a flow or pressure transducer and the other line has a restrictor that responds to the transducer, to balance the air and fuel supplied to the burner and ensure that the Gas mixture remains stoichiometric irrespective of the size of the flame and such that the flow rate of the gas fuel mixture more than at least 1/60 of the highest flow rate of the gas fuel mixture at the end near the open end of the burner, each passage being dimensioned so that with the highest obtainable flow rate of the fuel gas mixture , the flames do not rise from the flame retainer, with the lowest flow rate the speed of the fuel gas mixture at some point in the passage is sufficient to prevent the flame from retracting through the flame retainer. The burner of the present invention represents an important difference to the burners of the prior art because the burner can provide a stable flame in the flame retainer at low flow rates, but can provide a 60-fold increase in the flow rate of the gas mixture by providing sources of gaseous fuel and combustion support gas that can provide sufficiently high pressures, at high flow rate, a sufficient pressure drop in the flame retainer passages to obtain the required flow rate. The burner of the present canister retainer provides a decreasing turn rate of the order of 60: 1 and thus the stable flame is retained even when the air and fuel supply is reduced to sixty of the maximum capacity. Such a high ratio of decreasing rotation is very advantageous, since the production of heat can be controlled over a wide range. In addition, such a burner is ideal for use in situations where the gas supply is variable, as may occur in the case of vertical tanks that are set. The inlets can be provided with metering nozzles to separately supply air and fuel non-axially, for example substantially radially to the inside of the tube which forms a mixing zone between the inlets and the flame retainer, the measuring nozzles have holes with cross-sectional areas of flow related to the stoichiometric air-fuel ratio for which the fuel is completely burned. Preferably the inlets are arranged in the tube to supply air and fuel in colliding directions, to create turbulence and mixing inside the tube, for example locating the diametrically opposite entries among themselves, inside the tube. Conveniently the flame retainer provides a mounting for a lighter and an electrode associated with ground, and optionally also provides an assembly for an ionization test. Preferably the burner includes a monitor and control system coupled to the test, to interrupt the supply of fuel in case the unburned coal exceeds a predetermined level. In such mode, there may be a valve in the air supply line and a restrictor in the fuel line or there may be a valve in the fuel line and a variable speed fan in the air line. The flame retainer can comprise two or more nested tubes, each pair of adjacent tubes defining between them one of the passages of the flame retainer for the gaseous fuel, but other ways of defining the passages can be used, for example, a plurality of holes on a disc. The tubes (30a, 30b, 30c) can be stopped in a relative position relative to one another by one or more transverse forks and include a central bore with a countersunk outlet. Each countersunk outlet may have its terminal portion defined by internal and external cylindrical walls that are parallel to the longitudinal axis of the flame retainer. BRIEF DESCRIPTION OF THE FIGURES A burner of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which; Figure 1 is an end view of the burner incorporating a flame retainer embodiment according to the present invention; Figure 2 is a sectional longitudinal section through the burner of Figure 1, in line II-II of Figure 1; Figure 3 is a section in longitudinal section of the burner flame retainer of Figure 1 in the line III-III of Figure 1. DETAILED DESCRIPTION OF THE INVENTION The burner 10 illustrated in the drawings comprises a tubular box 11 of resistant material such as stainless steel, and is provided with a mounting flange 13 for attachment to a combustion apparatus, not shown. The combustion apparatus may be a boiler, a space heater with gas fire, a boiler, or a vertical evacuated outlet pipe, for example. A front end 11 'of the burner is open, so that it emerges from the flame and the opposite end 11"rear is closed and sealed to an acrylic observation window 12. Adjacent to the rear end, there are inlets 14, 16 for air (u oxygen) and for fuel, this is combustible gas, the inlets 14, 16 are internally threaded to receive connections for coupling to suitable air / fuel supply lines.The fuel inlet 16 is less than 1 air inlet 14. Both inlets 14 , 16 are threaded internally and inside each there is a measuring nozzle 18, 20. The measuring nozzle or nozzle 18 has a bore 22 which is basically of larger diameter than the bore 24 of the measuring nozzle 20. The areas of flow cut of the perforations 22, 24 are in a proportion corresponding to the stoichiometric proportion of fuel-air, in which fuel is completely oxidized, that is, burned. For complete combustion, different fuels require different amounts of air (or oxygen) and therefore the stoichiometric proportions will vary from one fuel to the other. It is contemplated, therefore, that the nozzles 18 and 20 will conform to the stoichiometric requirements of the particular fuel that is burned. Thus, one or both nozzles 18, 20, will be changed to adapt to the fuel, provided that the fuel is changed, to bring the combustion efficiency to a maximum, the gases supplied to the nozzles 18 and 20 at the same pressure so that the air flow is proportional to the perforations 22, 24 of the nozzles 18, 20 and that equal pressure condition will be assumed for the rest of the description. the required ratio of the flow cut areas of the perforations 22, 24 can be determined empirically. Alternatively, it can be established theoretically if the fuel composition is known. By way of example, the proportion of the areas 22, 24 is of the order of 10: 1 for fuels comprising mixtures of hydrocarbon gases, with air and gas pressures of the order of 76 mbar. For comparison, existing high pressure burners can operate at 5.1-7.6 mbar. Standard commercial burners usually operate at 1.3 mbar of air pressure and 5.1 mbar of gas pressure. Inside the burner box 11 there is a flame retainer fixed 30 according to the present invention manufactured from coaxially nested steel rings. The flame retainer 30 basically defines annular jets from which mixed streams of air and fuel, the jets are ignited to establish the required flame, to ignite the jets, a spark igniter is used. The igniter comprises a spark electrode 32 and a ground electrode 34. The electrode 32 is electrically insulated from the flame retainer 30. The electrodes 32 and 34 extend rearwardly and through the window 12 to the respective terminals 36, 38 for connect to an electrical supply. The flame retainer 30 is made of three coaxial tubes 30a, 30b, 30c stopped in a fixed spatial relationship by transversely spaced brass forks 33 (see Figure 3), which have been biased into holes aligned diametrically to each other. through the tubes 30a, 30b, 30c.The flame retainer 30 as a unit is supported and located inside the burner box 11 by forks 31. The tubes 30a, 30b, 30c are dimensioned and configured to provide relatively narrow annular passages 52, 54, 56 and 58 between the tube 30a and the burner box 11 between the tubes 30a and 30b, between the tubes 30b and 30c and between the tube 3Qc and the electrode 30. All these passages have countersunk outlets 60 at the end of the flame retainer 30 near the open end 11 'of the burner tube 11. Three tubes are present in the illustrated embodiment but the selected number from one up, is determined by the maximum amount of energy required by the burner 10. Each of the tubes 30b and 30c has a pair of longitudinal semi-cylindrical grooves which cooperate to provide two cylindrical passages for inserting and retaining the electrode 32 and the test 40, as shown in figure 1, the rest of the annular passage between the tubes 30b and 30c is as provided between the tubes 30a and 30b as can be seen in figure 3. The passages and the countersunk outlets are tell me Passed in such a way that in the maximum flat flow rate of fuel mixture. the flame is retained in the flame retainer and such as in the lower flow rate of fuel mixture the speed of the fuel mixture within the narrow portions of the passages 52 to 58 is sufficient to prevent flashback of the flame , this is the backward propagation of the flame to the mixing chamber. An ionisation test 40 is also mounted insulatively in the flame retainer 30 which again extends backward through the plate 12 to a terminal 42. The use of the ionisation test 40 and the ground electrode 38 allow the carbon content of the flame is controlled. If the carbon content is found to be less than a predetermined level, indicating inadequate combustion, the monitor can be arranged in a known manner to trigger a control system that disrupts the fuel supply. Thus the flame can be extinguished. In conventional gas burners, the gaseous fuel is expelled from a nozzle at the end of the burner tube, and the flame ignites at that point. The gas is transported to the nozzle by a conduit axially disposed within the tube. The air required for combustion is provided, by an electric air fan through ports in the tube, close upstream of the nozzle. The air mixes with the gas leaving the nozzle at the point of ignition.

For combustion to take place completely and stoichiometrically, air and gas must be mixed in the correct volume proportions. Where one gas is injected into the other, as in a conventional blower, combustion is not always, or more efficient, since mixing is occurring at the time of combustion. as a result the mixing of air and fuel is incomplete. It is virtually impossible to achieve the air / fuel stoichiometric ratio through the front of the flame. Thus, the flame is observed to have a different flame, with zones of different color, indicating poor mixing, varying the air / fuel stoichiometry and being an imperfect combustion of the fuel. In contrast to a burner according to this invention, the flame emanating from the flame retainer 30 is observed to be substantially uniform across its entire flame brake, with a uniform bright blue and with very small yellow flame regions. A flame of this appearance is a practical realization of an ideal flame where the fuel undergoes virtually complete combustion. The complete combustion achievable by the burner 10 is believed to be the result of two burner characteristics. Firstly, the fuel and air are introduced in the correct stoichiometric ratio governed first by the sizes of the perforations 22, 24 of the nozzles 8, 20. Second, it can be seen from the drawings that the perforations of the nozzles 18, 20 introduce air and fuel to the burner box as opposite flow jets, that is, the two jets provide diametrically opposed jets. Such shocking jets ensure a very effective initial mixing in the burner housing. Basically, high turbulent flows are created at the rear end of the box 11, which provides a mixing chamber of an important length between the nozzles 18, 20 and the outlet end of the flame retainer 30. While introducing the fuel / air introduced by the nozzles 18, 20 reaches the flame retainer 3Q, will be in a complete mixing condition, ideal for a complete and correct combustion. The operation and exit of the burner 10 can be controlled in different ways. It is desirable that the air supply includes a control valve and the air supply line incorporates a pressure or flow transducer. This, in turn, will control a fuel balancer, this is a gas restrictor. Such equipment is known and therefore will not be described in detail. Suffice it to note, however, that the objective of the control system is to balance the pressures of the gas and air and the flows to the burner 10, to maintain the desired stoichiometry by decreasing to the burner using the air control valve. With such an arrangement, the only valve that must be operated is the air control valve. Alternatively the burner can be controlled by a single valve operating now in the gas supply line. In this case, the gas or flow pressure is determined by a transducer that is used to control the air pressure or flow. By way of example, the air pressure or flow can be varied using a fan of a suitable variable speed. In installations that use more than one burner, for example in a house heater, it is contemplated that the air and fuel gas are supplied at high pressure, then only balance devices would be required to ensure that all burners receive air and fuel in the right proportion volumetrically. The burner 10 as described can be used only in a small appliance, for example a small household or commercial heating system, or in an oven or grill, in larger systems for industry, a given furnace, a boiler box, reactor or Similar may require many of those burners 10, which more conveniently couple to common manifolds of air and fuel manifolds. The burner 10 shown in the drawings burns noticeably in silence, due to the highly stable flame. As an example, such a burner has a total length of 275 mm and a diameter of 76 mm. The generated noise is less than that produced by a fan that supplies the air required for combustion.

Claims (14)

1. NOVELTY OF THE INVENTION Having described the invention as above, property is claimed as contained in the following: CLAIMS 1. - A burner for the combustion of a gas mixture of gaseous fuel with a combustion support gas, such as oxygen or air comprising a burner tube open at one end, and closed at its other end with a flame retainer where the fuel burns adjacent to the open end, the flame retainer is traversed by passages for the gas mixture, the burner has adjacent inlets At the closed end connected to the gaseous fuel supply lines and the combustion support gas, one of the lines has a control valve operable to control the size of the flame, a line has a flow or pressure transducer, and the other line has a restrictor that responds to the transducer, to balance the air and fuel supplied to the burner, ensuring that the the gas remains stoichiometric, regardless of the size of the flame, and such that the lowest gaseous mixture flow rate is at least as low as 1/60 of the highest fixed rate of the gas fuel mixture in each passage, having a flared outlet at the end near the open end of the burner, each passage being dimensioned so that with the highest flow rate obtainable from the gaseous fuel mixture, the flames do not rise from the flame retainer, with the lowest flow rate, the speed within the passage is sufficient to prevent the flame from retracting through the flame retainer.
2. 2. - A burner according to the preceding claim characterized in that the inlets are provided with measuring nozzles to separately supply air and fuel non-axially, basically radially to the interior of the tube which forms a mixing zone between the inlets and the retainer flame, the nozzles or measuring nozzles have holes with transverse flow area related to the stoichiometric proportion of air / fuel for which the fuel is completely burned.
3. 3. - A burner according to claim 2, characterized in that the inlets are arranged in the sol tube to supply air and fuel in colliding directions, to create turbulence and mixing inside the tube.
4. 4. - A burner according to claim 3, characterized in that the inlets are located diametrically opposite each other in the tube.
5. 5. - A burner according to one of claims 1 to 4, characterized in that the proportion of the cross-flow areas of the holes from 10 to 1.
6. 6. - A burner according to one of claims 1 to 5 , characterized in that the flame retainer provides a mounting for a lighter and an associated ground electrode.
7. 7. - A burner according to the claim 6, characterized in that the flame retainer also provides an assembly for an ionization test to detect the unburned carbon in the flame.
8. 8. - A burner according to the claim 7, characterized in that it is in combination with a monitor and control system coupled to the ionization test, in use to interrupt the supply of fuel in case the unburned coal reaches a predetermined level.
9. 9. A burner according to claim 8, characterized in that the valve is in the air supply line and a restrictor is in the fuel line.
10. 10. - A burner according to the claim 8, characterized in that the valve is in the fuel line and a variable speed fan is provided in the air line.
11. ll. - A burner according to one of the preceding claims, characterized in that it comprises two or more radially nested tubes, each pair of tubes defining adjacent one of the passages of the flame retainer for the gaseous fuel.
12. 12. - A burner according to claim 11, characterized in that the tubes are stopped relative to each other by one or more transverse forks.
13. 13. - A burner according to claim 12, characterized in that it includes a central bore with an offset outlet.
14. 14. - A burner according to one of claims 10 to 13, characterized in that each commutated outlet has its terminal portion defined by internal and external cylindrical walls that are parallel longitudinal away from the flame retainer.