CA1130719A - Liquid fuel burners - Google Patents
Liquid fuel burnersInfo
- Publication number
- CA1130719A CA1130719A CA327,819A CA327819A CA1130719A CA 1130719 A CA1130719 A CA 1130719A CA 327819 A CA327819 A CA 327819A CA 1130719 A CA1130719 A CA 1130719A
- Authority
- CA
- Canada
- Prior art keywords
- flame tube
- air
- burner
- fuel
- tube
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Pressure-Spray And Ultrasonic-Wave- Spray Burners (AREA)
Abstract
IMPROVEMENTS IN LIQUID FUEL BURNERS
Abstract An improved fuel burner particularly adapted for domestic use and capable of burning fuels such as fuel oil and the like with extremely high efficiency and low pollutant output is com-prised of a pair of plenum type atomizers, each having a convex surface onto which the fuel is flowed for atomization, the atom-izers being disposed at the end of a flame tube which in turn is located within a blast tube, said atomizers further being disposed symmetrically with respect to the axis of both the flame tube and the blast tube whereby the spray output from the atomizers is dis-charged into the flame tube to create a stable flame front that can be readily ignited by a spark type of ignitor. The atomizers are provided with one or more apertures through which atomizing gas is passed to generate the spray, and air access ports are located along the flame tube to provide the necessary air to complete the combustion process.
Abstract An improved fuel burner particularly adapted for domestic use and capable of burning fuels such as fuel oil and the like with extremely high efficiency and low pollutant output is com-prised of a pair of plenum type atomizers, each having a convex surface onto which the fuel is flowed for atomization, the atom-izers being disposed at the end of a flame tube which in turn is located within a blast tube, said atomizers further being disposed symmetrically with respect to the axis of both the flame tube and the blast tube whereby the spray output from the atomizers is dis-charged into the flame tube to create a stable flame front that can be readily ignited by a spark type of ignitor. The atomizers are provided with one or more apertures through which atomizing gas is passed to generate the spray, and air access ports are located along the flame tube to provide the necessary air to complete the combustion process.
Description
IMPROVEMENTS IN
LIpUID FUEL BURNERS
Description Technical Field As is well recognized in the industry, there has been a need to develop and to pxovide a fuel burning system which is capable of burning a liquid fuel in a very efficient manner with little or no smoke, and with minimal pollution to the atmos-phere.
In the case of existing residential oil burners, the burner must operate with low smoke e~ls-sions to prevent sooting of the heat exchanger and the objectionable pollution of residential neighbor-hoods. The result is that large amounts of excessair must be introduced in the present residential combustion process to assure that the burner operates at acceptable smoke levels.
It is well known that the pexformance of the high pressure oil burner that is used almost ex-clusively in residential heating applications today will vary dramatically from one furnace or boiler design to the next. This is hecause ~he high pres-sure nozzle does a poor job of atomizing the fuel.
These nozzles produce a substantial number of large droplets which impinge upon the wal.l.s of the combus-tion chamber and burn slowly. The speed at which these particles finally vaporize and hurn depends upon the size, shape, and residual heat within the furnace or boi.ler's combustion chamber. It can be said then that the combustion chamber within the.
furnace or boiler serves as a receptacle to capture large droplets of fuel and as an after-burning de~ice to burn these large droplets of fuel. Indeed, if the existing high pressure oil burner were capable o~
atomizing fuel oil to a hi~h degree, the heat exchanger could be coupled dixectly to the burner and there would be no need for a hot combustion cha~beF or fixe-box to complete the combustion process.
In many instances, the conventional oil burner may be 2-3 times larger than is necessary t:o provide adequate space heating. This is the case when the same burner is required to provide heat for hot water in addition to heat for home comfort. When out-side temperatures are low, and hot water demands are high, a high pressure burner in this type of system must be able to satisfy both requirements. This maximum heat load is what normally determines the firing rate of the burner. ~owever, when the demand for heat i5 low, as in the spring and fall months, and hot water demands are at a minimum, as would be the case at night, the burner will still operate at the same firing rate as it does when heating and hot water demands are high. The onl~ difference is th~t when the. heating requirements are low, the burner will stay on for ~ very short period of time. As is well known, this mode of operation is very inefficient.
During the short "on" cycle, the burner cannot achieve smokeless operation and reasonable efficiency before the thermostat cuts it off. During the "off" cycle, the residual heat in the furnace is dissipated to the atmosphere and this contributes to increased heat loss.
During the off cycle, there is also a loss_of heat within the house as the warm air escapes through the furnace stack. From this description it can be ap-preciated that the most economical domestic oil burner ~7~g syste~ would be one in which the burner operatescontinuously with the a~ility to vary its output to satisfy the fluctuating heat requirements within the household. In this way, there can be no inefficiencies associated with repeated startup and shutdown. A
quick calculation will show that the added electrical cost for continuous burner operation is very minimal compared with the fuel savings that can be realized.
Background Art An innovative approach to fuel burners is illustrated in U.S. Patent No. 3,425,058, issued January 28, 1969, to Robert S. Babingtoll. The burner therein disclosed represents an adaptation of the liquid atomization principles disclosed in U.S.
Patents 3,421,699 and 3,421,692, issued Jan~ary 14, 1969, to the same named inventor and his co-inventors in developing the apparatus and method shown in these patents.
In brief, the principle involved in the a-forementione~ patents is that of preparing a liquidfor spraying by causing it to spread out in a thin film over the exterior surface of a hollow plenum chamber which contains at least one orifice. When gas is introduced into the in~erior of the plenum, 25 it escapes through the aperture and thereby creates a very uniform spray of small liquid particles.
By varying the number of apertures, the configuration of the apertures, the shape and charac-teristics of the surface, the velocity and amount of 30 liquid supplied to the surface, and by controlling the gas pressure within the plenum, the quantity and quality of the resultant spray can be optimized to suit the particular burner application.
~13~7~9 It is this basic principle, described above~
that was utilized in the develop~ent of the ~urner disclosed in said Patent 3,425,058.
In the above mentioned patent, the burner is S so simple that it might even be called a fuel atomizing subsystem for a burner rather than a complete burner Indeed, from this very simple burner or subassembly evolved the more sophisticated and complete burner described in the present invention. In the earlier said Patent 3,425,058, the burner is comprised of a simple atomizing chamber having a cover thereover, the cover being provided with a spray discharge port to discharge the atomiæed fuel in a generally vertical direction. Disposed withln the atomizing chamber is a hollow plenum type atomizer t:hat is in communication with~an outside source of pressurized air. Liquid is introduced into the atomizing chamber so as to $10w over the exterior surface o~ the atomizing plenum.
Excess fuel that is not sprayed off flows downwardly into a drain where it is recirculated via a pump means to the liquid supply line. The atomizing plenum is provided with a small aperture centrally located beneath the opening in the cover, and the alr exiting there~rom creates a fine mist ~hich is dis-charged upwardly and out of the atomizing chamber Porcombustion external to the system. Means compri~ing a series of regulatable apertures are also provided in the atomizing chamber such that aspirated air can be drawn into said chamber or burner and mingled with the spray as it discharges from the opening in the top cover.
From this very simple version of a fuel burner was derived more sophisticated equipment, such as that shown and discussed in an art:icle in the 113~719 January 1976 issue of Popular Science entitled "Clog-Proof Super Spray Oil Burner". As noted in the article, one development that evolved was the use of two atomiz-ing plenums arranged to di.scharge the atomized liquids towards each other to create a more stable flame and a good place to initiate ignition.
Other arrangments of opposed spray heads are also suggested in U.S. patents by Babington, namely Patent 3,751,210 dated August 1973, and .
Patent 3,864,326 dated February 1975.
All of the above noted developmental work based on the utilization o~ the "Babington' principle proved conclusively that the system was perfectly capable of use in a fuel burning system and that, if properly designed, such a system has the potential of evolving into a commercial, practical, highly effi.cient fuel burner which can be used for domestic heating furnaces.
Descri~tion of the Invention The present invention deals with a novel fuel burner, particularly adapted for use in practi-cally every type of domestic heating furnace and, in particular, as a retrofit burner for exis~i.ng heating systems. Fuel oil can be burned close to the maxi-mum theoretical efficiency and with smoke readings which are zero at the instant the burner is ignited and which remain at zero throughout the burner opera~
tion.
In the present invention, the inefficiencies associated with many on-off burner cycles ~re elimi-nated. By simply controlling the liquid film thick-nesses over the atomizing surfaces as will be des-cribed, the firing rate of the burner can be modulated g over a typical range of 5-1 This means that the same burner, without changing atomizers, can be modu-lated either manually or automatically to match the heating and/or hot water loads in the house. For example, during modestly cool spring and summer evenings, the burner can be set to operate at a firing rate of 0.2 gal./hr. and during cold winter days when hot water is required, the same burner can be adjusted to consume fuel at a rate of 1.0 gal./hr~
These ~djustments can be made manually by simply ad-justing the fuel flow rate over the atomizing plenums by means of a simple valve in the liquid combustion air delivered to the flame tube. In the most sophis-ticated version of the novel burner disclosed herein, these adjustments can be made automatically with suitable control techniques. Accordingly, an object of the present invention is to produce an oil burner whose firing rate can be simply modulated either manually or automatically to suit the heating demand.
Another object of the invention is to pro-duce a burner that performs with high efficiency regardless of the combustion chamber that it is placed into and therefore is ideally suited as a retrofit or replacement burner for existing Eurnaces.
Another object of this invention is to pro-duce an oil burner that will permit substantial re-ductions in energy costs when retrofitted into exist-ing furnaces.
Still another object of this invention is to produce an oil burner with an exceptionally stable flame front.
Still another object of the invention is to produce a burner that is capable of operating at low firing rates, as for example less than 0.5 gal./hr.
without clogging problems.
~33719 A further object of this invention is to pro-duce an oil burner wherein combustion is essential~y completed within the fla~e tube of the burner, Still another object ~f this invention is to produce an oil burner where combustion air is suppliea in stages so as t~ control the burning rate and temper-ature and hence objectionably high nitrous oxide emis-sions.
The burner of this invention comprises a flame tube haying an inlet end and outlet end; means f~r ad-mittin~ air into the flame tube to cause said admitted air to flow in a direction along and parallel to the central axis of said tube; and a plurality of second ~eans for producing a corresponding plurality of streams of atomized fuel which are angled toward said outlet end and also toward the flame tube central axis so as to intersect substantially at said central axis.
Brief Description of the Drawin~~
Reference is now made to the appended drawin~s and the de.tailed description which follows, showing two preferred modes of practicing the invention:
Figs. lA and lB are schematic views of a typical heating furnace or irebox and showing the utility o the present invention as compared to the usual prior art apparatus;
Fig. 2 is a front end view of a fuel burner as-sembly as utilized in the firebox referred to in Fi~. 1.
Fig. 3 is a vertical section view taken along the line 3-3 of Fig. 2 and showing details of one of the fuel atomizing systems;
Fig. 4 is a sectional plan view taken along the line 4-4 of ~ig. 2 and showing details of one flame tube assembly;
Fig. 5 is a sectional plan view showing details of another flame tube assembly in accordance with the present invention;
Fig. 6 is still another sectional view of a fuel atomizing system in which an improved spray discharge horn is utilized.
Best Mode for Carrying Out the Invention Deferring descriptions of Figs. lA and lB momentarily, consideration will first be given to Figs. 2 and 4 which show one mode of carrying out the improved fuel burning assembly of the present invention. As shown in Fig. 4, an air tube 1, typically with an outside diameter of about 4", which is essentially an elon~ated open ended pipe, supports concentrically therein a flame tube 3 which typically is about 3 to 3-3/4 inches in diameter on a plurality of annular rings 5 and 7. The concentric relationship between the air tube ancl the Elame tube deEines an annular air passage 4 therebetween. Annular ring 7 is solid so as to close off said annular air passaqe at the discharge end o~ the burner assembly for the purpose oE dirccting second.lry combustion air as will be discussed later. ~nnular rinc3 5 helps to conce~ntrically support flame tube 3 and also contains a series of circumferential holes 6. These holes create a ~13~7i9 slight pressure dxop in the airflow passin~ throu~h said air passage 4, which i.n turn equalizes the flow of ai.r through said passage. Hot or downstream end 9 of the flame tube is nor~ally placed in the firebox of the fur-5 nace or the like. The other end 11 of fl~me tube 3 isrelatively cool and connects to a foraminous fire wall 14, which is shown as being generally cone shaped, said wall being provided with a relatively large central aperture 16 passin~ through fire wall 14. Also affixed to said fire wall are two fuel atomizing systems 30 and 30' which are defined by cuplike atomizin~ chambers 15, 15', Typically, the apertures in said fora3ninous fire wall a~e ~bout 1/8" in diameter or less, and the large central aperture 16 would be on the order of about~ 1/2"
to about 1-1/2" diameter.
Further upstream of the fuel atomizing systems and not shown are provisivns for housing the burner motor, air compressor, air blower, fuel recirculating ~ystem, and electronic burner combustion controls.
The hot end 9 of the flame tube 3 is provided with a pair of cutouts 13,13', the function of which will become apparent subsequently. Similarly, the flame tube is proviaed with a further pair o~ apertures 12,12' loca-ted approxi3~ately ~idway of its length. ~hese apertures tl2,12') are disposed at 90 relative to the cutouts 13, 13'~ As shown in Fig. 2, cutouts 13' and 13 are loca-ted at the twelve o'clock and six o'clock position, while aperture 12' and 12 are located at the three o'clock and nine o'clock position. However, tube 3 may be rotated 90 so as to reverse the relative positionin~ of cutouts 13' and 13 with respect to those of apertures 12' and 12.
Such reversal will serve only to cause the~flame leaving the burner to bush out in the twelve o'clock and six o'clock posit~on, rather than in the thre~- orclock and nine o'clock position as will be the case with the con-figuration shown in Figs. 2 and 4. The function of these 1~3~719 cutouts and ~pertures will ~e discussed in ~ore detail later~
Projecting into the flame tube through the central opening 16 of wall 14 and disposed midway between the sprays emanating from atomizing systems 30,30' is a conventional spark ignitor 18 which in-cludes a pair of discharge electrodes 19 and 21. The ignitor may be supported by a suitable bracket (not shown) and, of course, is energized from a source of high voltage electricity. In addition, if desired, the gap between electrodes 19 and 21 need not be located midway between the fuel atomizing systems 30,30' but instead can be located adjacent the spray plume from either atomizing system 30 and 30' ~s shown in Figs. 3 and 4, the atomizing chambers 15 and 15', respectively, m~y be provided with spray discharge ho~ns 17 and 17', the purpose of which will be discussed later.
Fig. 3 shows that each atomizing chamber 15 is provided with a pair of conduits 23' and 25' which are, in essence, elbows having one end projectin~
into the chamber along a generally vertical plane passing immediately through the walls thereof. The uppermost conduit 23' defines a fuel supply conduit whose lower end 36' e~tends .into atomizing chamber 15' where it is disposed generally over the high point of atomizing plenum 26'. The upper end 37' of conduit 25' is ~lush with the lower interior surface of atomizing chamber 15.
Disposed directly below each fuel supply conduit 23' and supported on the rear wall 31' of atomizing chamber 15' is atomizing plenum 26' which is shown in Fig. 3 in the form of a hollow sphere but ~hich may be in the form of any hollow plenum with a smooth convex outer surface Gas under pressure is supplied to atomizing plenum 26' ~hrough conduit 27', 113~7~9 which extends through the rear wall 31' of the atomizing chamber 15'. The ato~izing plenum 26' is provided with at least one small aperture 29', only one being shown in Fig. 3, which is located so as to discharge fuel 5 spray particles directly toward and through discharge horn 17'.
As clearly shown in Fig. 3, the rear wall 31' of the atomizing chamber 15' is provided with a pair of apertures 33~ whose function will be described in 10 detail hereinafter.
Though not shown, it is to be llnderstood that each inlet conduit 23' is connected to a so-lrce of liquid fuel by means of a pump whereby the fuel may be pumped through these conduits and deposited on the convex 15 surface of plenum chamber 26'. Similarly, the drain or discharge conduit 25' is connected to the fuel sup-ply system so that the excess or run-off liquid which is not atomized by ~ir escaping from orifice 29' in atomizer 26' can be returned to the fuel system not 20 shown and recirculated therein. The description given above with specific reference to fuel atomizing system 30'of Fig. 3 applies in identical fashion to fuel atomizi.ng system 30 shown in Fig. 4, Fig. 3 also shows one means whereby spray 25 discharge horn 17' may be affixed to atomizing chamber 15', Said horn 17' is shown in its pref~rred form as a txuncated cone with its small opening facing the flame tube, However~ in certain burner variations discharge horn 17' may be a simple cylindrical section 30 or even a truncated cone diverging outwardly towards the flame tube. The size and shape of spray discharge horn 17 will depend upon the aerodynamic cQnditions surrounding atomizing chamber 15', as dictated by the u~stream blower` pre~sure and the (lownst)^eam static and 113~ 9 ~12-dynamic pressure within the flame tube, In any eyentt the spray discharge hoxns are desi~ned to control the size of the liquid fuel spray particles and/or to prevent the flame ~ithin the flame tube ~rom propa~atin~
upstream into the atomizing chamber. These features will be explained further in a subsequent discussion of Fig. 6 which shows an improved discharge horn con-figuration. In certain app:Lications of the present invention where there is sufficient ai~flow and pres-sure available from the auxiliary compressor and com-bustion air blower, the upstream flame propagation may be pxevented, and the liquid particle size opti-miæed, without the need for spray discharge horn 17'.
This is done by controlling the conditions within atomizing chamber 15' and involves the interrelation-ship of variables such as the size and shape of atomizer 26'; the size and shape of discharge orifice 29';
the pressure supplied to the interior of atomizer
LIpUID FUEL BURNERS
Description Technical Field As is well recognized in the industry, there has been a need to develop and to pxovide a fuel burning system which is capable of burning a liquid fuel in a very efficient manner with little or no smoke, and with minimal pollution to the atmos-phere.
In the case of existing residential oil burners, the burner must operate with low smoke e~ls-sions to prevent sooting of the heat exchanger and the objectionable pollution of residential neighbor-hoods. The result is that large amounts of excessair must be introduced in the present residential combustion process to assure that the burner operates at acceptable smoke levels.
It is well known that the pexformance of the high pressure oil burner that is used almost ex-clusively in residential heating applications today will vary dramatically from one furnace or boiler design to the next. This is hecause ~he high pres-sure nozzle does a poor job of atomizing the fuel.
These nozzles produce a substantial number of large droplets which impinge upon the wal.l.s of the combus-tion chamber and burn slowly. The speed at which these particles finally vaporize and hurn depends upon the size, shape, and residual heat within the furnace or boi.ler's combustion chamber. It can be said then that the combustion chamber within the.
furnace or boiler serves as a receptacle to capture large droplets of fuel and as an after-burning de~ice to burn these large droplets of fuel. Indeed, if the existing high pressure oil burner were capable o~
atomizing fuel oil to a hi~h degree, the heat exchanger could be coupled dixectly to the burner and there would be no need for a hot combustion cha~beF or fixe-box to complete the combustion process.
In many instances, the conventional oil burner may be 2-3 times larger than is necessary t:o provide adequate space heating. This is the case when the same burner is required to provide heat for hot water in addition to heat for home comfort. When out-side temperatures are low, and hot water demands are high, a high pressure burner in this type of system must be able to satisfy both requirements. This maximum heat load is what normally determines the firing rate of the burner. ~owever, when the demand for heat i5 low, as in the spring and fall months, and hot water demands are at a minimum, as would be the case at night, the burner will still operate at the same firing rate as it does when heating and hot water demands are high. The onl~ difference is th~t when the. heating requirements are low, the burner will stay on for ~ very short period of time. As is well known, this mode of operation is very inefficient.
During the short "on" cycle, the burner cannot achieve smokeless operation and reasonable efficiency before the thermostat cuts it off. During the "off" cycle, the residual heat in the furnace is dissipated to the atmosphere and this contributes to increased heat loss.
During the off cycle, there is also a loss_of heat within the house as the warm air escapes through the furnace stack. From this description it can be ap-preciated that the most economical domestic oil burner ~7~g syste~ would be one in which the burner operatescontinuously with the a~ility to vary its output to satisfy the fluctuating heat requirements within the household. In this way, there can be no inefficiencies associated with repeated startup and shutdown. A
quick calculation will show that the added electrical cost for continuous burner operation is very minimal compared with the fuel savings that can be realized.
Background Art An innovative approach to fuel burners is illustrated in U.S. Patent No. 3,425,058, issued January 28, 1969, to Robert S. Babingtoll. The burner therein disclosed represents an adaptation of the liquid atomization principles disclosed in U.S.
Patents 3,421,699 and 3,421,692, issued Jan~ary 14, 1969, to the same named inventor and his co-inventors in developing the apparatus and method shown in these patents.
In brief, the principle involved in the a-forementione~ patents is that of preparing a liquidfor spraying by causing it to spread out in a thin film over the exterior surface of a hollow plenum chamber which contains at least one orifice. When gas is introduced into the in~erior of the plenum, 25 it escapes through the aperture and thereby creates a very uniform spray of small liquid particles.
By varying the number of apertures, the configuration of the apertures, the shape and charac-teristics of the surface, the velocity and amount of 30 liquid supplied to the surface, and by controlling the gas pressure within the plenum, the quantity and quality of the resultant spray can be optimized to suit the particular burner application.
~13~7~9 It is this basic principle, described above~
that was utilized in the develop~ent of the ~urner disclosed in said Patent 3,425,058.
In the above mentioned patent, the burner is S so simple that it might even be called a fuel atomizing subsystem for a burner rather than a complete burner Indeed, from this very simple burner or subassembly evolved the more sophisticated and complete burner described in the present invention. In the earlier said Patent 3,425,058, the burner is comprised of a simple atomizing chamber having a cover thereover, the cover being provided with a spray discharge port to discharge the atomiæed fuel in a generally vertical direction. Disposed withln the atomizing chamber is a hollow plenum type atomizer t:hat is in communication with~an outside source of pressurized air. Liquid is introduced into the atomizing chamber so as to $10w over the exterior surface o~ the atomizing plenum.
Excess fuel that is not sprayed off flows downwardly into a drain where it is recirculated via a pump means to the liquid supply line. The atomizing plenum is provided with a small aperture centrally located beneath the opening in the cover, and the alr exiting there~rom creates a fine mist ~hich is dis-charged upwardly and out of the atomizing chamber Porcombustion external to the system. Means compri~ing a series of regulatable apertures are also provided in the atomizing chamber such that aspirated air can be drawn into said chamber or burner and mingled with the spray as it discharges from the opening in the top cover.
From this very simple version of a fuel burner was derived more sophisticated equipment, such as that shown and discussed in an art:icle in the 113~719 January 1976 issue of Popular Science entitled "Clog-Proof Super Spray Oil Burner". As noted in the article, one development that evolved was the use of two atomiz-ing plenums arranged to di.scharge the atomized liquids towards each other to create a more stable flame and a good place to initiate ignition.
Other arrangments of opposed spray heads are also suggested in U.S. patents by Babington, namely Patent 3,751,210 dated August 1973, and .
Patent 3,864,326 dated February 1975.
All of the above noted developmental work based on the utilization o~ the "Babington' principle proved conclusively that the system was perfectly capable of use in a fuel burning system and that, if properly designed, such a system has the potential of evolving into a commercial, practical, highly effi.cient fuel burner which can be used for domestic heating furnaces.
Descri~tion of the Invention The present invention deals with a novel fuel burner, particularly adapted for use in practi-cally every type of domestic heating furnace and, in particular, as a retrofit burner for exis~i.ng heating systems. Fuel oil can be burned close to the maxi-mum theoretical efficiency and with smoke readings which are zero at the instant the burner is ignited and which remain at zero throughout the burner opera~
tion.
In the present invention, the inefficiencies associated with many on-off burner cycles ~re elimi-nated. By simply controlling the liquid film thick-nesses over the atomizing surfaces as will be des-cribed, the firing rate of the burner can be modulated g over a typical range of 5-1 This means that the same burner, without changing atomizers, can be modu-lated either manually or automatically to match the heating and/or hot water loads in the house. For example, during modestly cool spring and summer evenings, the burner can be set to operate at a firing rate of 0.2 gal./hr. and during cold winter days when hot water is required, the same burner can be adjusted to consume fuel at a rate of 1.0 gal./hr~
These ~djustments can be made manually by simply ad-justing the fuel flow rate over the atomizing plenums by means of a simple valve in the liquid combustion air delivered to the flame tube. In the most sophis-ticated version of the novel burner disclosed herein, these adjustments can be made automatically with suitable control techniques. Accordingly, an object of the present invention is to produce an oil burner whose firing rate can be simply modulated either manually or automatically to suit the heating demand.
Another object of the invention is to pro-duce a burner that performs with high efficiency regardless of the combustion chamber that it is placed into and therefore is ideally suited as a retrofit or replacement burner for existing Eurnaces.
Another object of this invention is to pro-duce an oil burner that will permit substantial re-ductions in energy costs when retrofitted into exist-ing furnaces.
Still another object of this invention is to produce an oil burner with an exceptionally stable flame front.
Still another object of the invention is to produce a burner that is capable of operating at low firing rates, as for example less than 0.5 gal./hr.
without clogging problems.
~33719 A further object of this invention is to pro-duce an oil burner wherein combustion is essential~y completed within the fla~e tube of the burner, Still another object ~f this invention is to produce an oil burner where combustion air is suppliea in stages so as t~ control the burning rate and temper-ature and hence objectionably high nitrous oxide emis-sions.
The burner of this invention comprises a flame tube haying an inlet end and outlet end; means f~r ad-mittin~ air into the flame tube to cause said admitted air to flow in a direction along and parallel to the central axis of said tube; and a plurality of second ~eans for producing a corresponding plurality of streams of atomized fuel which are angled toward said outlet end and also toward the flame tube central axis so as to intersect substantially at said central axis.
Brief Description of the Drawin~~
Reference is now made to the appended drawin~s and the de.tailed description which follows, showing two preferred modes of practicing the invention:
Figs. lA and lB are schematic views of a typical heating furnace or irebox and showing the utility o the present invention as compared to the usual prior art apparatus;
Fig. 2 is a front end view of a fuel burner as-sembly as utilized in the firebox referred to in Fi~. 1.
Fig. 3 is a vertical section view taken along the line 3-3 of Fig. 2 and showing details of one of the fuel atomizing systems;
Fig. 4 is a sectional plan view taken along the line 4-4 of ~ig. 2 and showing details of one flame tube assembly;
Fig. 5 is a sectional plan view showing details of another flame tube assembly in accordance with the present invention;
Fig. 6 is still another sectional view of a fuel atomizing system in which an improved spray discharge horn is utilized.
Best Mode for Carrying Out the Invention Deferring descriptions of Figs. lA and lB momentarily, consideration will first be given to Figs. 2 and 4 which show one mode of carrying out the improved fuel burning assembly of the present invention. As shown in Fig. 4, an air tube 1, typically with an outside diameter of about 4", which is essentially an elon~ated open ended pipe, supports concentrically therein a flame tube 3 which typically is about 3 to 3-3/4 inches in diameter on a plurality of annular rings 5 and 7. The concentric relationship between the air tube ancl the Elame tube deEines an annular air passage 4 therebetween. Annular ring 7 is solid so as to close off said annular air passaqe at the discharge end o~ the burner assembly for the purpose oE dirccting second.lry combustion air as will be discussed later. ~nnular rinc3 5 helps to conce~ntrically support flame tube 3 and also contains a series of circumferential holes 6. These holes create a ~13~7i9 slight pressure dxop in the airflow passin~ throu~h said air passage 4, which i.n turn equalizes the flow of ai.r through said passage. Hot or downstream end 9 of the flame tube is nor~ally placed in the firebox of the fur-5 nace or the like. The other end 11 of fl~me tube 3 isrelatively cool and connects to a foraminous fire wall 14, which is shown as being generally cone shaped, said wall being provided with a relatively large central aperture 16 passin~ through fire wall 14. Also affixed to said fire wall are two fuel atomizing systems 30 and 30' which are defined by cuplike atomizin~ chambers 15, 15', Typically, the apertures in said fora3ninous fire wall a~e ~bout 1/8" in diameter or less, and the large central aperture 16 would be on the order of about~ 1/2"
to about 1-1/2" diameter.
Further upstream of the fuel atomizing systems and not shown are provisivns for housing the burner motor, air compressor, air blower, fuel recirculating ~ystem, and electronic burner combustion controls.
The hot end 9 of the flame tube 3 is provided with a pair of cutouts 13,13', the function of which will become apparent subsequently. Similarly, the flame tube is proviaed with a further pair o~ apertures 12,12' loca-ted approxi3~ately ~idway of its length. ~hese apertures tl2,12') are disposed at 90 relative to the cutouts 13, 13'~ As shown in Fig. 2, cutouts 13' and 13 are loca-ted at the twelve o'clock and six o'clock position, while aperture 12' and 12 are located at the three o'clock and nine o'clock position. However, tube 3 may be rotated 90 so as to reverse the relative positionin~ of cutouts 13' and 13 with respect to those of apertures 12' and 12.
Such reversal will serve only to cause the~flame leaving the burner to bush out in the twelve o'clock and six o'clock posit~on, rather than in the thre~- orclock and nine o'clock position as will be the case with the con-figuration shown in Figs. 2 and 4. The function of these 1~3~719 cutouts and ~pertures will ~e discussed in ~ore detail later~
Projecting into the flame tube through the central opening 16 of wall 14 and disposed midway between the sprays emanating from atomizing systems 30,30' is a conventional spark ignitor 18 which in-cludes a pair of discharge electrodes 19 and 21. The ignitor may be supported by a suitable bracket (not shown) and, of course, is energized from a source of high voltage electricity. In addition, if desired, the gap between electrodes 19 and 21 need not be located midway between the fuel atomizing systems 30,30' but instead can be located adjacent the spray plume from either atomizing system 30 and 30' ~s shown in Figs. 3 and 4, the atomizing chambers 15 and 15', respectively, m~y be provided with spray discharge ho~ns 17 and 17', the purpose of which will be discussed later.
Fig. 3 shows that each atomizing chamber 15 is provided with a pair of conduits 23' and 25' which are, in essence, elbows having one end projectin~
into the chamber along a generally vertical plane passing immediately through the walls thereof. The uppermost conduit 23' defines a fuel supply conduit whose lower end 36' e~tends .into atomizing chamber 15' where it is disposed generally over the high point of atomizing plenum 26'. The upper end 37' of conduit 25' is ~lush with the lower interior surface of atomizing chamber 15.
Disposed directly below each fuel supply conduit 23' and supported on the rear wall 31' of atomizing chamber 15' is atomizing plenum 26' which is shown in Fig. 3 in the form of a hollow sphere but ~hich may be in the form of any hollow plenum with a smooth convex outer surface Gas under pressure is supplied to atomizing plenum 26' ~hrough conduit 27', 113~7~9 which extends through the rear wall 31' of the atomizing chamber 15'. The ato~izing plenum 26' is provided with at least one small aperture 29', only one being shown in Fig. 3, which is located so as to discharge fuel 5 spray particles directly toward and through discharge horn 17'.
As clearly shown in Fig. 3, the rear wall 31' of the atomizing chamber 15' is provided with a pair of apertures 33~ whose function will be described in 10 detail hereinafter.
Though not shown, it is to be llnderstood that each inlet conduit 23' is connected to a so-lrce of liquid fuel by means of a pump whereby the fuel may be pumped through these conduits and deposited on the convex 15 surface of plenum chamber 26'. Similarly, the drain or discharge conduit 25' is connected to the fuel sup-ply system so that the excess or run-off liquid which is not atomized by ~ir escaping from orifice 29' in atomizer 26' can be returned to the fuel system not 20 shown and recirculated therein. The description given above with specific reference to fuel atomizing system 30'of Fig. 3 applies in identical fashion to fuel atomizi.ng system 30 shown in Fig. 4, Fig. 3 also shows one means whereby spray 25 discharge horn 17' may be affixed to atomizing chamber 15', Said horn 17' is shown in its pref~rred form as a txuncated cone with its small opening facing the flame tube, However~ in certain burner variations discharge horn 17' may be a simple cylindrical section 30 or even a truncated cone diverging outwardly towards the flame tube. The size and shape of spray discharge horn 17 will depend upon the aerodynamic cQnditions surrounding atomizing chamber 15', as dictated by the u~stream blower` pre~sure and the (lownst)^eam static and 113~ 9 ~12-dynamic pressure within the flame tube, In any eyentt the spray discharge hoxns are desi~ned to control the size of the liquid fuel spray particles and/or to prevent the flame ~ithin the flame tube ~rom propa~atin~
upstream into the atomizing chamber. These features will be explained further in a subsequent discussion of Fig. 6 which shows an improved discharge horn con-figuration. In certain app:Lications of the present invention where there is sufficient ai~flow and pres-sure available from the auxiliary compressor and com-bustion air blower, the upstream flame propagation may be pxevented, and the liquid particle size opti-miæed, without the need for spray discharge horn 17'.
This is done by controlling the conditions within atomizing chamber 15' and involves the interrelation-ship of variables such as the size and shape of atomizer 26'; the size and shape of discharge orifice 29';
the pressure supplied to the interior of atomizer
2~' via tube 27~; the interna]. diameter of feed tube 23'; the spacing and relative fore and aft positioning of atomizer 26' with respect to lower end 36 of feed tube 23'; the spacing between discharge orifice 29' and the forward face 38' of atomizing chamber 15'; the quantity of fuel suppli.ed through feed tuhe 23'; t.he size of blower inlet ports 33', and the velocity and ~uantity o air enteri.ng atomiziny chamber 15' through blower inlet ports ~3'. In cases where the spray dis-charge horns 17 and 17' are not required, they are simply removed with the result that the spray particles.
emanating from atomizers 26 and 26' are discharged directly into flame tube 3 through openings 34 and 34' in their respective atomizing chambers lS and 15'.
The following parameters represent some typi-cal ~alues for a burner with a variab.le irin~ rat.e . . , ~13697~9 from about 0.2 to about 0.6 gal./hr. A typical atomizer is a sphere or bullet shape between about 1/4" to about 1" outside diameter. The cross-sectional area of the discharge orifice 29' typically is about 0.0001 square inch to about 0.0003 square inch. The pressure supplied to the interior of atomizer 26' via tube 27' is typically about 2 psi to about 20 psi. The spacing 35' between discharge orifice 29' and the forward face 38' of atomizing chamber 15' can be from 0 to about 1". The spacing between lower end 36' of liquid feed tube 23' and the uppermost surface of atomizer 26' is typically about 1/8" to about 3/8".
The typical dimensions for blower inlet ports 33' are about 1/8"-
emanating from atomizers 26 and 26' are discharged directly into flame tube 3 through openings 34 and 34' in their respective atomizing chambers lS and 15'.
The following parameters represent some typi-cal ~alues for a burner with a variab.le irin~ rat.e . . , ~13697~9 from about 0.2 to about 0.6 gal./hr. A typical atomizer is a sphere or bullet shape between about 1/4" to about 1" outside diameter. The cross-sectional area of the discharge orifice 29' typically is about 0.0001 square inch to about 0.0003 square inch. The pressure supplied to the interior of atomizer 26' via tube 27' is typically about 2 psi to about 20 psi. The spacing 35' between discharge orifice 29' and the forward face 38' of atomizing chamber 15' can be from 0 to about 1". The spacing between lower end 36' of liquid feed tube 23' and the uppermost surface of atomizer 26' is typically about 1/8" to about 3/8".
The typical dimensions for blower inlet ports 33' are about 1/8"-
3/8" diameter. Typical internal diameters of feed tube 23' are about 1/16" to about 1/4". The length of spray dischargehorn 17' when present can be up to about 1-1/2" and have an exit diameter between about 3/8" and 1".
Figure 5 is a sectional plan view showing details of a fuel burning assembly which includes a number of features which are employed to minimize the problem of soot formation which can occur along fire wall 14 and on the inside walls of the flame tube especially at the hic3her firing rates.
As shown in Fic3. 5, the improvecl fuel burning assembly consists of an air tube 1 which is essentially an elonc3ated open ended pipe. nisposed within air tube 1 is flame tube 3 whieh is maintained concentric with respect to the air tube so as to de-fine an annular air passage therebetween. Flame tube 3 is main-tained concentric to air tube 1 by positioning against a circum-ferential shoulder 67 which can include set pins or screws ( not shown). Other means can be used to maintain the flame tube con-centrically within the air tube 1. The flame tube 3 is open atboth ~7~
ends; one end 9 thereof, which may be ~ermed the hot end, faces toward the interior of the firebox of the fur-nace or the like. The other end which may be called the cool end, is attached to atomizing chamber 52 by means of a slip fit over the aforementioned shoulder 67.
Further upstream of atomizing chamber 52 and not shown, provisions may also be made to house the auxiliary burner equipment such as the drive motor, air atomizing compressor, combustion air blower, fuel recircuiation system and the electronic burner controls, if desired.
The open end 9 of the flame tube 3 is provided with a pair of cutouts 13,13', the function of which will become apparent subsequently. Similarly the flame tube is provided with a further pair of à~ertures 12, 12' located approximately midway of its length. These apertures (12,12') are disposed at 90 relative to the cutouts 13,13' but as mentioned previously, flame tube 3 may be rotated 90 to alter the flame pattern leaving the burner.
In ad~ition, the flame tube of ~ig. 5 is pro-vided with a plurality of centrifugal swirl shutters or louvers 50. One convenient confic3uration employs
Figure 5 is a sectional plan view showing details of a fuel burning assembly which includes a number of features which are employed to minimize the problem of soot formation which can occur along fire wall 14 and on the inside walls of the flame tube especially at the hic3her firing rates.
As shown in Fic3. 5, the improvecl fuel burning assembly consists of an air tube 1 which is essentially an elonc3ated open ended pipe. nisposed within air tube 1 is flame tube 3 whieh is maintained concentric with respect to the air tube so as to de-fine an annular air passage therebetween. Flame tube 3 is main-tained concentric to air tube 1 by positioning against a circum-ferential shoulder 67 which can include set pins or screws ( not shown). Other means can be used to maintain the flame tube con-centrically within the air tube 1. The flame tube 3 is open atboth ~7~
ends; one end 9 thereof, which may be ~ermed the hot end, faces toward the interior of the firebox of the fur-nace or the like. The other end which may be called the cool end, is attached to atomizing chamber 52 by means of a slip fit over the aforementioned shoulder 67.
Further upstream of atomizing chamber 52 and not shown, provisions may also be made to house the auxiliary burner equipment such as the drive motor, air atomizing compressor, combustion air blower, fuel recircuiation system and the electronic burner controls, if desired.
The open end 9 of the flame tube 3 is provided with a pair of cutouts 13,13', the function of which will become apparent subsequently. Similarly the flame tube is provided with a further pair of à~ertures 12, 12' located approximately midway of its length. These apertures (12,12') are disposed at 90 relative to the cutouts 13,13' but as mentioned previously, flame tube 3 may be rotated 90 to alter the flame pattern leaving the burner.
In ad~ition, the flame tube of ~ig. 5 is pro-vided with a plurality of centrifugal swirl shutters or louvers 50. One convenient confic3uration employs
4 louvers, each bein~ spaced abou~ one-quarter of the circumference of the flame tube ~rom the ~djacent louvers.
Other con~igurations and amounts of louvers can be em-ployed if desir~d. The louvers arc placed upstream from the apertures 12,12' and preferably axially about mid-way b~tween apertures 12,12 t and fire wall 57. The lou-vers provide for a curtain of swirlin~ air along the flame tube wall. The swirling is confined as will be discussed hereinbelow in view of the interrelationship of the lou-vers with the apertures 12,12' and the cu~outs 13,13'.
Typic~lly the apertures 50, 12, 12', 13 and 13' are about 0 2-0 4 square inch in cross-sectional area ~r ~ typical burner with a variable firing rate o from about 0 2 to about 0.6 gal./hr.
113a~
~15-The cylindric~l ~lame tube 3 is provided at its opposite end 11 with a pair of spray discharge horns 17 and 17', opening into a common atomizing chamber 5~.
As was previously discussed, certain burner operating conditions would not require the use of spray discharge horns 17 and 17' and in such cases, a simple opening in said atomizing chamber 52 would he provided instead.
Spray discharge horns 17 and 17' are supported upon a solid wall 51 which is shown as being generally straight and transverse to the flame tube. Also support~
ed upon the solid wall 51 is an air blast tube 53 located within and concentrically around the central axis of the atomizing chamber 52. The air blast tube 53passes throu~lfand isalso supported by the backwall`54 of ator~lizing chamber 52. Tlle air blast tube 53 can include a pai~ of apertures 56,56' (e.g. - typically having a diameter between 1/8" to 1/2") 1eading to the atomizing chamber 52. These apertures provide for a portion of the blower air entering the central air blast tube to be entrained into the atomizing chamber 52 where it commingles with the fuel spray and is dis-charged into the flame tube through spray discharge horns 17 and 17'. Should ap~rtures 56 and 56' be insuffic~ent to provide chamber S2 with t.he needed air to supply the aspiration needs of plenums 26 and 26~, or if it is desired to further raise the static pres sure within common chamber 52, then blower air inlet ports 66and 66' o~similar or sma~ler cross-sectional area to 56,56' may be provided in wal] 54. Consequently, by sizing blower air inlet ports 66 and 66' in conjunction with apertures 56 and 56', chamber 52 may be operated at any desired pressure. The forward wall 51 of atomiz-ing chamber 52 is provided with a relatively large central aperture 55 passing through the wall 51. This 7~9 -.l6 aperture 55 is the same size as tne'inside diameter of air blast tube 53 which is about 1/~:" to about 1-1/2" so that blower air can pass directly throug~
air ~last tube 53, and enter the flame tube via aper-ture 55 in wall 51, Spaced slightly downstream such asabout 1/8" to about 1/2" from the forward wall 51 of the atomizing chamber and parallel theretor'isa fora-minous or perforated fire wall 57 which is shown as being generally pl~nar and' containing apertures there-in~ The perforated fire wall 57 is provided with arelatively large central aperture 59 passing through the wall 57. The large central opening 59 in the perforat~
ed fire wall 57 ispxefer~bl~y sm~ller than the inside'.di.a-meter of the central blast tube and hence the opening 55 in wall 51. As a result, a small amount of air is forced out radially between the forward wall 51 of the 'atomizing chamber 52 and the perforated fire wall. This air bleeds throuyh the perforated ~ire wall and into the flame tube to keep the fire within the flame tube:f~om impinying on the fire wall.
Projecting through rear wall 54 and front wall 51 of the atomizing chamber and ful-ther extending into the flame tube through a pai~ of openings .n fire wall 57 lS a pair of electrodes 19 and 21. S~id elec--trodes are encased in porcelain jackets 68 and 69to shie].d said eleatrodes from fuel spray as they pass through atomizing chamber 52. The spark yap 70 be-tween electrodes 19 and 21 is located within the flame tube and on the outer periphery of the spray plume issuing from atomizer 26.
~ s shown.in Fig. 5, the chamber 52 may be provided with discharge cones 17 and 17' which discharge atomized fuel inwardly into the flame tube 3.
Both of the atomizing plenum chambers 26,26' are disposed within the same atomizing chamber 52~
.
113~719 ~17-Plenum 26' is supported on the rear wall 54 of chamber 52 and plenum 26 is interconnected via conduit 27' from plenum 26'. Use of a common cham~er assures that the static pressure surrounding atomizing plenum 26 is essen-tially the same as that surrounding plenum 26', Plenums 26 and 26' are supplied with air under pressure through conduits 27 and 27' respectively. As shown in Fig, 5, the air is supplied to 27 and 27' from the same source via conduits 60 and 61 respectively, Of course, separate sources of air can be employed if desired.
The liquid fuel supply system for the atomizing plenums is essentially the same as the fuel supply sys-tem referred to with respect to Fig. 3 except that both supply lines o~ conduits are in a common chamber. Also, in the embodiment of Fig. 5, there need only be one common drain located at the low point in atomizing cham-ber 52. Each atomizing plenum 26 and 26' is provided with at least one small aperture 29 and 29' as illustrated in Fig. 3 which is located so as to discharge air and fuel spray directly toward its associated discharge horn 17 and 17'.
As shown in Fig. 5, the rear wall 54 of the atomizing chan~er 52 is provided with an aperture 61' to admit air into the air blast tube 53.
A pair of fuel supply conduits 23 and 23' are pre-ferably connected to a source of liquid fuel by rneans of a pump, whereby the fuel may be pumped through these conduits and deposited on the convex surfaces of atom-izing plenums 26 and 26' respectively. Similarly, the singular drain conduit 25' is connected to the fuel sup-ply system so that liquid which is not atomized within common atomizing chamber 52 can be returne~ to the fuel system not shown and recirculated back to fuel supply conduits 23 and 23', Accordingly, the main differences between the configuration of Fig. 5 as compared to Fig. 4 are a 1~30'7~9 single atomizinq ch~m~er instead of two such cham-bers; a generall~ planar fo~w~xd wallor face instead of a generally cone shaped fire wall; a perforated fire wall spacea from the forward wall of the atomizing chamber;
and the presence of centrifugal swirl shutters or lou-vers. If desired, the burner of Fig. 4 can ~e modified by employing less than all of the modifications dis-cussed hereina~ove for the embodiment of Fig. 5 by em-ploying any one ox any combination of two or more of the new features of the burnex illustrated by Fig. 5.
Directing attention now particularly to Figs. 3 and 4, the operation of the fuel atomizing and combus-tion system is as follows.
Liquid fuel is introduced into the system by the conduits 23,23'. The liquid uel flows over atomizing plenums 26,26' and a portion thereof is atomized by air under pressure which is introduced in~o each plenum through conduits 27 and 27'. Liquid which is not atom-ized flows to the bottom of the atomizing chambers 15, 15' and is withdrawn therefrom by drain con~u.its 25,25' for recirculation in the fuel supply system.
As described above, tlle atomization process uti-lizes the b~sic "Babington" p.rinc.iple disclosed in prior mentioned Patents 3,421,699 and 3,421,692.
Due to the dischar~e of air from the atomizing plenums through apertures 29 and 29' there is created a low pressure region in the immediate vicinity of said apextures~ This causes additional air to flow into atomizing chambexs 15,15' through ports 33,33' to com-~.ingle with the atomized fuel being discharged into flame tube 3. Additional combustion ai~ is supplied throu~h the aperture 16 in the foraminous fire wall_l4, 60 as to ~low axially alon~ flame tube 3 to intersect with the fuel sprays emanating from atomizers 26 and 26' so as to readily i~nite when the igniter 18 is energized to cause a sp~rk between electrodes 19 and 21.
113~'719 In the preferred embodiments disclosed herein the combustion air enters through the aperture 16. It is, how-ever~ within the scope of the invention to supply such com-bustion air by increasing the supply of air which enters the atomizing chambers through the ports 33 and 33' in Fig.
4, or the ports 66,66' in Fig 5. This in turn will supply more air to fla~e tube 3 through discharge horns 17 and 17' The two streams of additional air thus provided intersect substantially along the flame tube axis, a~d the resultant of these two intersecting airstreams tends to flow general-ly along the axis of the flame tube. Such an arrangement may ~e satisfactory in certain instances, particularly where the burner geomet~y ~ay make it difficult to provide for the combustion air to be directed into the flame tube from one end thereof, or in instances where the burner is deslgned for a low firing rate in which event sufficient co~bustion air is obtained by such an alter~ative arrangement.
Additional combustion air passes along the annular passage 4 between flame tube 3 and blast tube 1 and is staged into the interior of the flame tube 3 through the staging ports 12,12' and the cutouts 13,13'. Fig. 4 also shows one means whereby additional combustion air may be provided at the juncture betweell tl~e flam~ tube and the conical fire wall as, for ins~ance, a multiplicity ofports 8.
Tlle unique confi~urat.ion of the flame tube within a blast tube provides a unique heat exchanger in which com-bustion air for staging purposes passes through the anular area between the flame tube and t.he bla~st tuhe. In traver-sing this route, the combustion air picks up heat from the inner hot walls of the flame tube. This hot air t as it is delivered to the interior of the flame tube at the two a-forementioned staging locations and throu~h ports 8, i~
desired helps to promote rapid vaporization of the atom-ized fuel to complete the combustion process downstream in the flame tube. The staging of combustion air in this manner allows the temperature within the flame tube ~o be maintained at the desired level to keep nitrous oxide emissions to a mi.nimum.
1~3~ 9 .-~o--Still another advantage of the manner in which combustion air is staged is to produce a flame in which, when emitted from the burner, is short and bushy. This is achieved by introducing staged air in a nonsymmetrical manner which is contrary to the fuel~air mixing technique used in conventional residential type oil burners. For example, at the first combustion air staging location, downstream from the spray impingement site, two air blasts 12,12' may be introduced per~endicular to the long axis of the blast tube, at three o'clock and nine o'clock locations. By subjecting the flame within the flame tube to a nonsymmetrical air blast of this type~
the flame is c~used to s~uirt out and fill the flame tube at the six o'clock and twelve o'clock positions, Fur-thermore~ the low static pxessure within the air blastsat the three and nine o'clock positions causes the flame to ~rap around the air blasts and thus produce a shorter and more compact flame which fills the entire flame tube.
In the second combustion air stagin~ location, two air blasts are introduced at the lip of the blast tube hùt this time the air blasts are introduced at the twelve o'clock and six o'clock positions. This causes the flame to spread out in the three o'clock and nine o'clock posi-tion as it leaves the burner blast tube and enters the combustio:l chamber~
A short bushy flame of this type is ideal for a retrofit or replacemellt burner, because i~ is suited for use in any type of combustion chamber. This is in contrast to a long thin flame which would impinge upon the back side of many combustion chambers and cause ero-sion of the combustion liner, At the same time, the combustion air passing between the flame tube and the blast tube serves to keep the outer blast tube cool, thereby preventing heat erosion of the blast tube, In the case of the present invention, the atomization sys-tem is so efficient, and the subsequent fuel/air mixing 1~3(~7~
and vaporization is likewise carried out in such a highly efficient manner, that the burner does not re-quire a hot combustion chamber to achieve high combus-tion perform~nce.
The present burner desiyn of Fig 4 has been utilized in a wide variety of different combustio~-chambers and has always been able to achieve smokeless operation, and flue-gas CO2 levels between 14-141/2%, when operating at a firing rate which is close to that of the furnace rating. Even when the present burner is set to operate at firing rates well helow the furnace rating (e.g. burner operating at 0~ gal./hr, in ~ 1,0 gal./hr. furnace) CO2 levels with smokeless operation will normally never fall below 13~.
The burner configuration illustrated in Fig
Other con~igurations and amounts of louvers can be em-ployed if desir~d. The louvers arc placed upstream from the apertures 12,12' and preferably axially about mid-way b~tween apertures 12,12 t and fire wall 57. The lou-vers provide for a curtain of swirlin~ air along the flame tube wall. The swirling is confined as will be discussed hereinbelow in view of the interrelationship of the lou-vers with the apertures 12,12' and the cu~outs 13,13'.
Typic~lly the apertures 50, 12, 12', 13 and 13' are about 0 2-0 4 square inch in cross-sectional area ~r ~ typical burner with a variable firing rate o from about 0 2 to about 0.6 gal./hr.
113a~
~15-The cylindric~l ~lame tube 3 is provided at its opposite end 11 with a pair of spray discharge horns 17 and 17', opening into a common atomizing chamber 5~.
As was previously discussed, certain burner operating conditions would not require the use of spray discharge horns 17 and 17' and in such cases, a simple opening in said atomizing chamber 52 would he provided instead.
Spray discharge horns 17 and 17' are supported upon a solid wall 51 which is shown as being generally straight and transverse to the flame tube. Also support~
ed upon the solid wall 51 is an air blast tube 53 located within and concentrically around the central axis of the atomizing chamber 52. The air blast tube 53passes throu~lfand isalso supported by the backwall`54 of ator~lizing chamber 52. Tlle air blast tube 53 can include a pai~ of apertures 56,56' (e.g. - typically having a diameter between 1/8" to 1/2") 1eading to the atomizing chamber 52. These apertures provide for a portion of the blower air entering the central air blast tube to be entrained into the atomizing chamber 52 where it commingles with the fuel spray and is dis-charged into the flame tube through spray discharge horns 17 and 17'. Should ap~rtures 56 and 56' be insuffic~ent to provide chamber S2 with t.he needed air to supply the aspiration needs of plenums 26 and 26~, or if it is desired to further raise the static pres sure within common chamber 52, then blower air inlet ports 66and 66' o~similar or sma~ler cross-sectional area to 56,56' may be provided in wal] 54. Consequently, by sizing blower air inlet ports 66 and 66' in conjunction with apertures 56 and 56', chamber 52 may be operated at any desired pressure. The forward wall 51 of atomiz-ing chamber 52 is provided with a relatively large central aperture 55 passing through the wall 51. This 7~9 -.l6 aperture 55 is the same size as tne'inside diameter of air blast tube 53 which is about 1/~:" to about 1-1/2" so that blower air can pass directly throug~
air ~last tube 53, and enter the flame tube via aper-ture 55 in wall 51, Spaced slightly downstream such asabout 1/8" to about 1/2" from the forward wall 51 of the atomizing chamber and parallel theretor'isa fora-minous or perforated fire wall 57 which is shown as being generally pl~nar and' containing apertures there-in~ The perforated fire wall 57 is provided with arelatively large central aperture 59 passing through the wall 57. The large central opening 59 in the perforat~
ed fire wall 57 ispxefer~bl~y sm~ller than the inside'.di.a-meter of the central blast tube and hence the opening 55 in wall 51. As a result, a small amount of air is forced out radially between the forward wall 51 of the 'atomizing chamber 52 and the perforated fire wall. This air bleeds throuyh the perforated ~ire wall and into the flame tube to keep the fire within the flame tube:f~om impinying on the fire wall.
Projecting through rear wall 54 and front wall 51 of the atomizing chamber and ful-ther extending into the flame tube through a pai~ of openings .n fire wall 57 lS a pair of electrodes 19 and 21. S~id elec--trodes are encased in porcelain jackets 68 and 69to shie].d said eleatrodes from fuel spray as they pass through atomizing chamber 52. The spark yap 70 be-tween electrodes 19 and 21 is located within the flame tube and on the outer periphery of the spray plume issuing from atomizer 26.
~ s shown.in Fig. 5, the chamber 52 may be provided with discharge cones 17 and 17' which discharge atomized fuel inwardly into the flame tube 3.
Both of the atomizing plenum chambers 26,26' are disposed within the same atomizing chamber 52~
.
113~719 ~17-Plenum 26' is supported on the rear wall 54 of chamber 52 and plenum 26 is interconnected via conduit 27' from plenum 26'. Use of a common cham~er assures that the static pressure surrounding atomizing plenum 26 is essen-tially the same as that surrounding plenum 26', Plenums 26 and 26' are supplied with air under pressure through conduits 27 and 27' respectively. As shown in Fig, 5, the air is supplied to 27 and 27' from the same source via conduits 60 and 61 respectively, Of course, separate sources of air can be employed if desired.
The liquid fuel supply system for the atomizing plenums is essentially the same as the fuel supply sys-tem referred to with respect to Fig. 3 except that both supply lines o~ conduits are in a common chamber. Also, in the embodiment of Fig. 5, there need only be one common drain located at the low point in atomizing cham-ber 52. Each atomizing plenum 26 and 26' is provided with at least one small aperture 29 and 29' as illustrated in Fig. 3 which is located so as to discharge air and fuel spray directly toward its associated discharge horn 17 and 17'.
As shown in Fig. 5, the rear wall 54 of the atomizing chan~er 52 is provided with an aperture 61' to admit air into the air blast tube 53.
A pair of fuel supply conduits 23 and 23' are pre-ferably connected to a source of liquid fuel by rneans of a pump, whereby the fuel may be pumped through these conduits and deposited on the convex surfaces of atom-izing plenums 26 and 26' respectively. Similarly, the singular drain conduit 25' is connected to the fuel sup-ply system so that liquid which is not atomized within common atomizing chamber 52 can be returne~ to the fuel system not shown and recirculated back to fuel supply conduits 23 and 23', Accordingly, the main differences between the configuration of Fig. 5 as compared to Fig. 4 are a 1~30'7~9 single atomizinq ch~m~er instead of two such cham-bers; a generall~ planar fo~w~xd wallor face instead of a generally cone shaped fire wall; a perforated fire wall spacea from the forward wall of the atomizing chamber;
and the presence of centrifugal swirl shutters or lou-vers. If desired, the burner of Fig. 4 can ~e modified by employing less than all of the modifications dis-cussed hereina~ove for the embodiment of Fig. 5 by em-ploying any one ox any combination of two or more of the new features of the burnex illustrated by Fig. 5.
Directing attention now particularly to Figs. 3 and 4, the operation of the fuel atomizing and combus-tion system is as follows.
Liquid fuel is introduced into the system by the conduits 23,23'. The liquid uel flows over atomizing plenums 26,26' and a portion thereof is atomized by air under pressure which is introduced in~o each plenum through conduits 27 and 27'. Liquid which is not atom-ized flows to the bottom of the atomizing chambers 15, 15' and is withdrawn therefrom by drain con~u.its 25,25' for recirculation in the fuel supply system.
As described above, tlle atomization process uti-lizes the b~sic "Babington" p.rinc.iple disclosed in prior mentioned Patents 3,421,699 and 3,421,692.
Due to the dischar~e of air from the atomizing plenums through apertures 29 and 29' there is created a low pressure region in the immediate vicinity of said apextures~ This causes additional air to flow into atomizing chambexs 15,15' through ports 33,33' to com-~.ingle with the atomized fuel being discharged into flame tube 3. Additional combustion ai~ is supplied throu~h the aperture 16 in the foraminous fire wall_l4, 60 as to ~low axially alon~ flame tube 3 to intersect with the fuel sprays emanating from atomizers 26 and 26' so as to readily i~nite when the igniter 18 is energized to cause a sp~rk between electrodes 19 and 21.
113~'719 In the preferred embodiments disclosed herein the combustion air enters through the aperture 16. It is, how-ever~ within the scope of the invention to supply such com-bustion air by increasing the supply of air which enters the atomizing chambers through the ports 33 and 33' in Fig.
4, or the ports 66,66' in Fig 5. This in turn will supply more air to fla~e tube 3 through discharge horns 17 and 17' The two streams of additional air thus provided intersect substantially along the flame tube axis, a~d the resultant of these two intersecting airstreams tends to flow general-ly along the axis of the flame tube. Such an arrangement may ~e satisfactory in certain instances, particularly where the burner geomet~y ~ay make it difficult to provide for the combustion air to be directed into the flame tube from one end thereof, or in instances where the burner is deslgned for a low firing rate in which event sufficient co~bustion air is obtained by such an alter~ative arrangement.
Additional combustion air passes along the annular passage 4 between flame tube 3 and blast tube 1 and is staged into the interior of the flame tube 3 through the staging ports 12,12' and the cutouts 13,13'. Fig. 4 also shows one means whereby additional combustion air may be provided at the juncture betweell tl~e flam~ tube and the conical fire wall as, for ins~ance, a multiplicity ofports 8.
Tlle unique confi~urat.ion of the flame tube within a blast tube provides a unique heat exchanger in which com-bustion air for staging purposes passes through the anular area between the flame tube and t.he bla~st tuhe. In traver-sing this route, the combustion air picks up heat from the inner hot walls of the flame tube. This hot air t as it is delivered to the interior of the flame tube at the two a-forementioned staging locations and throu~h ports 8, i~
desired helps to promote rapid vaporization of the atom-ized fuel to complete the combustion process downstream in the flame tube. The staging of combustion air in this manner allows the temperature within the flame tube ~o be maintained at the desired level to keep nitrous oxide emissions to a mi.nimum.
1~3~ 9 .-~o--Still another advantage of the manner in which combustion air is staged is to produce a flame in which, when emitted from the burner, is short and bushy. This is achieved by introducing staged air in a nonsymmetrical manner which is contrary to the fuel~air mixing technique used in conventional residential type oil burners. For example, at the first combustion air staging location, downstream from the spray impingement site, two air blasts 12,12' may be introduced per~endicular to the long axis of the blast tube, at three o'clock and nine o'clock locations. By subjecting the flame within the flame tube to a nonsymmetrical air blast of this type~
the flame is c~used to s~uirt out and fill the flame tube at the six o'clock and twelve o'clock positions, Fur-thermore~ the low static pxessure within the air blastsat the three and nine o'clock positions causes the flame to ~rap around the air blasts and thus produce a shorter and more compact flame which fills the entire flame tube.
In the second combustion air stagin~ location, two air blasts are introduced at the lip of the blast tube hùt this time the air blasts are introduced at the twelve o'clock and six o'clock positions. This causes the flame to spread out in the three o'clock and nine o'clock posi-tion as it leaves the burner blast tube and enters the combustio:l chamber~
A short bushy flame of this type is ideal for a retrofit or replacemellt burner, because i~ is suited for use in any type of combustion chamber. This is in contrast to a long thin flame which would impinge upon the back side of many combustion chambers and cause ero-sion of the combustion liner, At the same time, the combustion air passing between the flame tube and the blast tube serves to keep the outer blast tube cool, thereby preventing heat erosion of the blast tube, In the case of the present invention, the atomization sys-tem is so efficient, and the subsequent fuel/air mixing 1~3(~7~
and vaporization is likewise carried out in such a highly efficient manner, that the burner does not re-quire a hot combustion chamber to achieve high combus-tion perform~nce.
The present burner desiyn of Fig 4 has been utilized in a wide variety of different combustio~-chambers and has always been able to achieve smokeless operation, and flue-gas CO2 levels between 14-141/2%, when operating at a firing rate which is close to that of the furnace rating. Even when the present burner is set to operate at firing rates well helow the furnace rating (e.g. burner operating at 0~ gal./hr, in ~ 1,0 gal./hr. furnace) CO2 levels with smokeless operation will normally never fall below 13~.
The burner configuration illustrated in Fig
5 is somewhat bette- in performance than that illus-trated in Fig. 4. For instance, flue-gas CO2 levels of 15%, which areapproxim~tely the maximum level, have been achieved at zero smoke. This value is just below the theoretica].ly obtainable when ~he precise amount of air is mixed with the hydrocarbon fuel. This is in contrast to the average conventional home oil burner that operates at CO2 levels of 8~ evcn when the burner firing rate is matchcd to the furnace capacitY
These characteristics o~ total independence of furnace design and furnace temperature makes ~he present invention ideal as a replacement or retrofit burner. This non-dependence of furnace temperature also means that the present burner will achieve smoke-less operation the instant ignition occurs and before the combustion chamber becomes hot. The typical con-ventional high pressure burner takes several minutes for the smoke level to drop to acceptable levels after ignition has occurred.
1~30719 ~22-Another fact to be noted is that conventional high pressure nozzles have difficulty oper~ting at firing rates below approximately 0.7 gal.~hr. without encountering a high incidence of clogging. In the present burner, there is essentially no minimum firing rate that can beatt~ined; a prototype burner has been operated ata firing rate ofless thanO~l gal /hr, This means that each individual atomizer is operating at less th~n 0 05 gal./hr. Further, it is not neces-sary, in the present burner, that both atomizers begenerating the same amount of fuel spray fox the bur-n~r to operate efficiently. For example, one atomizer may have a firing rate of 0 06 gal./hr~ while the other has a firing rate of 0.04 gal /hr. A burner of this type will operate just as efficiently as one in which each atomizer is delivering a spray rate of 0 05 gal./hr. This low firing xate capability of the present invention is very important in ]ight of the present energy crisis because homes in the future will 20 be built with better insulation and the trend is towards low Eiring burners that can provide high]y efficiant operation.
It should be not~d that the perforations in the fire wall 14 are so numbered and sized that a ver~
25 30~t flow of air passes through this wall. This soft air flow tends to keep products of combustion from fil-tering or rolling bac~ toward the fuel atomizing sys-tems and the ignitor, thus inhibiting sooting of these elements.
The included ang]e between the fuel atomizing systems 30,30~ is sh~n in Fig. 4 as being approximately 90, This angle can be varied, however, a~d ~ay be between 15 and 150, and pre~exably between 45 ~nd 150~, Turning now to Figs. 1 and lA, it will he noted that in the prior art the atomizing nozzles are 1~307~9 ~23-located at the end of the blast tube. Consequently~
the nozzle'is subjected to high temperaturesrand as such is subject to varnish 'depositions ana clogging.
In contrast, utilizing applicant's improved fuel burning system, the atomizing plenums are located well upstream from the end of the blast tube and as such are sheltered from the radiant~nd convective heat of the firebox and the associated problems of fuel cracking and varnishing.
Even though burners made in accordance with ~igs, 3 and 4 are very efficient and qui,te satisfac-tory as discussed hereinabove, the operation of such at the higher fuel rates can lead to some limited amount of sooting on conical fire wall 14 and on portions of the 1ame tube. The impxoved con~iguration illu~trated by Flg. 5 eliminates all soot formation.
Only the basic differences between the operation of the buxner illustrated by Fig. 5 and that of the burner il-lustrated by Fig. 4 will be discussed hereinbelow, it being understood that those aspects of the operation o~
the burner illustrated by Fig. 5 not discussed in any detail are simil~r to those of the burncr of the type shown by Fi~. 4.
The air blast ~ube 53 directs air along the cen-tral axis of the single atomizing chamber 52 and alongthe central axis oE the flame tube 3. ~ portion of the blower air entering the air blast tube 53 is pre-ferably entrained or forced into the atomizing chamber 52 via openings 56 and 56' where it conmingles with the fuel spray and is discharged into the ~lame tube 3 via spray discharge horns 17 and 17'. The atomizers may draw the air into the ch~mber 52 via apertures 56 and 56' by the low pressure area created at the orifices of said atomizing plenums, or under certain operation con-ditions pressurized air may also be forced into atomiæingchamber 52 through apertures 56 and 56'.
11307~9 ~2~-As st~ted earlier, common chamber 52 m~y also be fitted with blower air pressurization ports 66 and 66' so that common ch'amber 52 r.lay be operated at still a more elevated stattc pressure if so desired. Such pressurization would more likely be employed at high firing rates'and where it is desirous to mix as much air with the atomized spray as possible before dis--chargin~ the mixture into the fl~me tube.
The use of one common atomizing chamber to contain the atomizing plenums instead of a plurality of atomizing chambers assures that the ambient pres-sure surrounding each ato~izing p~enum will be essen-~ially the'same, 'With a common at:omizing chamber the local air velocity around each atomizer is also reduce~
because of the larger volume inside common chamber 52.
Thus in chamber 52 it is further assured that high air velocities will not disturb the film of liquid flowin~
over atomizers 26 and 26', The configuration of Fig. 5 is therefore less sensitive than thatshown in Fig. 4.
Since the large aentral opening in the per-forated wall is smaller than the inside diameter of the central air blast tube 53, a small amount of air is directed or forced radially outwarflly between the for~lard face of lhe a'omizin~ chamber and the perforated fire wall. The perforations in the fire w~ re so num~ered and sized that a very soft flow of air p~sses throu~h this wall. This air bleeds througll the perforated' fire wall and into the flame tube, thereby keeping or holding the flame off the fire wall, and insulatin~
the relatively aool surface of the front face of the atomizing chamber ~rom the hot environment: on the down-stream side of the fire wall. Without the perfoxated 113~19 ~25~-fire wall the condition of relatively cool fuel on the inside of the` atomizing chamber, and a hot fire on the downstream side of the atomizing chamber would predispose the forward wall of the atomizing chamber to soot buildup on the flame tube side. In addition, the use of generally straight walls instead of the generally cone shaped fire wall of Fig. 4 ~inimizes the tendency for soot buildup since in the configura-tion of FigO 4, the number of corners involved makes it difficult to provide sufficient air mixing to all of the corners The use of a substant.ially planar faced fire wall removes the restriction on the minimum spray angle as stated for the sprays in Fig. 4. The use of the planar face fire wall permits the minimum included angle where sprays meet to be reduced substantially.
The preferred minimum included angle is about 5.
Excellent results have been achieved with an angle of about 27.
The centrifugal swirl shutters or louvers 50 promote rapid mixing of combustion air and fuel spray to prevent soot buildup on the flame tube 3~ The air which passes into the flame tube through the centri-fugal swirl shutters provides a curtain of swirling air along the flame tube wall. rrhis i.nsulates t:he flame tube wall from direct ~lame impin~ementand prevents hot spots and 113~719 ~26-flame erosion problems. The curtain of swirling air is heaviest in the upstream vicinity of the flame tube where it enters through the louvers. When the swirling air encounters the transverse air blasts about midway along the flame tube from apertures 12,12', and again at the discharge lip ~f the flame tube from cutouts 13,13', the swirling motion is sub-stantially destroyed. This is important to assure that the swirling air is mixed with the vaporized and burning fuel before it exits flame tube 3.
It was discussed hereinabove with respect to Fig. 3 that the spray discharge horn 17' served two purposes. Horn 17' was designed to control the mass median diameter of the spray entering flame tube 3 and also to prevent the flame within flame tube 3 from pxopagati.ng upstream and into atomizing chamber 15. The spray particle size can be optimized by ad-justing the geometry of horn 17' with respect to its length, exit diameter and conical angle. Said horn can be sized such that the spray issuing forth from ori~ice 29' i9 disch~r~ed into flame tube 3 unrestricted by horn 17', or said horn may be designed to restxict a portion of the spray emanatin~ from 29', In this latter c~se, the inner walls of said horn serve to skim off the lar~er spray particles on the outer periphery of the spray plume, These captured fuel particles simply flow back into atomizing chamber 15 along the inclined inner walls of said spray discharge horn 17'.
This technique works ~ell when the skimming required is minimal, and when the ~elocity of the commingled air and fuel particles passing through said horn is low.
However, when it is desired to restrict a ~ubstantial amount o~ the spray to further reduce particle size, or when velocities within discharge ho~n 17' axe hi~h~
11307~9 the discharge horn assembly shown in Fig. 6 is more useful. This high velocity discharqe horn assembly 20 is comprised of an inner shroud 17' and an outer shroud 22. As shown in Fig. 6 the down-stream ends of these shrouds are preferably in the same plane.
However, in some cases, depending upon the static pressure, com-bustion air velocity, and local eddies within flame tube 3, outer shroud 22 may be somewhat longer or shorter than inner shroud 17' to promote better drainback and/or to eliminate soot buildup between said shrouds or around the entire configuration 20'.
In operation the high velocity discharge horn assembly 20 shown in Fig. 6 skims off a portion of the fuel spray originating from orifice 29'.
The relatively high velocity of the spray passing through inner shroud 17' causes impinging fuel to run along the inner walls of shroud 17' towards the flame tube. This raw fuel is prevented from spilling over into the flame tube by means of the outer shroud 22. Said raw fuel upon reaching the discharge lip of the inner shroud 17' runs back between said inner shroud and said outer shroud 22, mostly along the outer surEace of thc inner shroud 17, and back towards the forward wall 28 o~ the atomi~inc3 chamber 15.
This excess or run-off fue~1 then drains back into chamber 15 via small drain tub~ 72. Durinc~ burner operation, drain tube 72 which has an I.D. of appro~imately 1/16-1/8" becomes filled with fuel and acts as a trap to prevent the back flow of combustion products into the atomizing chamber.
The other purpose of high velocity discharge horn assembly 20 is to prevent burn back in the atomizing chamber. Essentially the assembly acts as an ejector which is sized such that the fuel/air velocity exiting from said inner shroud 17' is at least as 27 ~
~3~7~9 great as the flame speed of the fuel burning within - 27a --2~-flame tube 3, This means that the ~lame within the flame tube cannot propagate upstream and into atomiziny chamber 15'.
In cases where the velocity of commingled liquid spray and air exiting from discharge horn assembly 20' is very high so as to cause flame in-stability or a fluctuating flame front within the flame tube 3, then flame holder 71 may be provide~. Said flame holder is in the form of a simple ring or washer having a large central opening 63, said opening being sized slightly larger than that of the spr~y plume diameter at that point. 'rhis allows the fuel spray to pass unimpeded through saia opening 63 without wetting the walls of said flame holder 71.
The turbulence and subsequent low static pressure that is created around flame holder 71 when the spray passes through it, causes the flame to seat or attach itself to the downstream face of flame holder 71. In Fig. 6 said flame holder 71 is supported from outer shroud 22 ~ two small rod like appendages 62. ~t i5 desir-able that these rods 62 be small in cross-section so that flame holder 71 takes on the appearance Qf be.ing suspended in space approximately 1/8 - 1.-1/2" down-stream of the exit oE inner shroud 17'. The exact loca-tion of flame holder 71 will depend upon the relativevelocity between the flame speed and the fuel/air mi.x-ture leaving shroud 17'.
Having described a pre~erred mode of practicing the invention, it will be apparent to those ~killed in the art that Various modifications and changes can be made therein; which modification and changes fall within the purview of the inventive concept defi~ed by the ap-pended claims wherein what is claimed is:
These characteristics o~ total independence of furnace design and furnace temperature makes ~he present invention ideal as a replacement or retrofit burner. This non-dependence of furnace temperature also means that the present burner will achieve smoke-less operation the instant ignition occurs and before the combustion chamber becomes hot. The typical con-ventional high pressure burner takes several minutes for the smoke level to drop to acceptable levels after ignition has occurred.
1~30719 ~22-Another fact to be noted is that conventional high pressure nozzles have difficulty oper~ting at firing rates below approximately 0.7 gal.~hr. without encountering a high incidence of clogging. In the present burner, there is essentially no minimum firing rate that can beatt~ined; a prototype burner has been operated ata firing rate ofless thanO~l gal /hr, This means that each individual atomizer is operating at less th~n 0 05 gal./hr. Further, it is not neces-sary, in the present burner, that both atomizers begenerating the same amount of fuel spray fox the bur-n~r to operate efficiently. For example, one atomizer may have a firing rate of 0 06 gal./hr~ while the other has a firing rate of 0.04 gal /hr. A burner of this type will operate just as efficiently as one in which each atomizer is delivering a spray rate of 0 05 gal./hr. This low firing xate capability of the present invention is very important in ]ight of the present energy crisis because homes in the future will 20 be built with better insulation and the trend is towards low Eiring burners that can provide high]y efficiant operation.
It should be not~d that the perforations in the fire wall 14 are so numbered and sized that a ver~
25 30~t flow of air passes through this wall. This soft air flow tends to keep products of combustion from fil-tering or rolling bac~ toward the fuel atomizing sys-tems and the ignitor, thus inhibiting sooting of these elements.
The included ang]e between the fuel atomizing systems 30,30~ is sh~n in Fig. 4 as being approximately 90, This angle can be varied, however, a~d ~ay be between 15 and 150, and pre~exably between 45 ~nd 150~, Turning now to Figs. 1 and lA, it will he noted that in the prior art the atomizing nozzles are 1~307~9 ~23-located at the end of the blast tube. Consequently~
the nozzle'is subjected to high temperaturesrand as such is subject to varnish 'depositions ana clogging.
In contrast, utilizing applicant's improved fuel burning system, the atomizing plenums are located well upstream from the end of the blast tube and as such are sheltered from the radiant~nd convective heat of the firebox and the associated problems of fuel cracking and varnishing.
Even though burners made in accordance with ~igs, 3 and 4 are very efficient and qui,te satisfac-tory as discussed hereinabove, the operation of such at the higher fuel rates can lead to some limited amount of sooting on conical fire wall 14 and on portions of the 1ame tube. The impxoved con~iguration illu~trated by Flg. 5 eliminates all soot formation.
Only the basic differences between the operation of the buxner illustrated by Fig. 5 and that of the burner il-lustrated by Fig. 4 will be discussed hereinbelow, it being understood that those aspects of the operation o~
the burner illustrated by Fig. 5 not discussed in any detail are simil~r to those of the burncr of the type shown by Fi~. 4.
The air blast ~ube 53 directs air along the cen-tral axis of the single atomizing chamber 52 and alongthe central axis oE the flame tube 3. ~ portion of the blower air entering the air blast tube 53 is pre-ferably entrained or forced into the atomizing chamber 52 via openings 56 and 56' where it conmingles with the fuel spray and is discharged into the ~lame tube 3 via spray discharge horns 17 and 17'. The atomizers may draw the air into the ch~mber 52 via apertures 56 and 56' by the low pressure area created at the orifices of said atomizing plenums, or under certain operation con-ditions pressurized air may also be forced into atomiæingchamber 52 through apertures 56 and 56'.
11307~9 ~2~-As st~ted earlier, common chamber 52 m~y also be fitted with blower air pressurization ports 66 and 66' so that common ch'amber 52 r.lay be operated at still a more elevated stattc pressure if so desired. Such pressurization would more likely be employed at high firing rates'and where it is desirous to mix as much air with the atomized spray as possible before dis--chargin~ the mixture into the fl~me tube.
The use of one common atomizing chamber to contain the atomizing plenums instead of a plurality of atomizing chambers assures that the ambient pres-sure surrounding each ato~izing p~enum will be essen-~ially the'same, 'With a common at:omizing chamber the local air velocity around each atomizer is also reduce~
because of the larger volume inside common chamber 52.
Thus in chamber 52 it is further assured that high air velocities will not disturb the film of liquid flowin~
over atomizers 26 and 26', The configuration of Fig. 5 is therefore less sensitive than thatshown in Fig. 4.
Since the large aentral opening in the per-forated wall is smaller than the inside diameter of the central air blast tube 53, a small amount of air is directed or forced radially outwarflly between the for~lard face of lhe a'omizin~ chamber and the perforated fire wall. The perforations in the fire w~ re so num~ered and sized that a very soft flow of air p~sses throu~h this wall. This air bleeds througll the perforated' fire wall and into the flame tube, thereby keeping or holding the flame off the fire wall, and insulatin~
the relatively aool surface of the front face of the atomizing chamber ~rom the hot environment: on the down-stream side of the fire wall. Without the perfoxated 113~19 ~25~-fire wall the condition of relatively cool fuel on the inside of the` atomizing chamber, and a hot fire on the downstream side of the atomizing chamber would predispose the forward wall of the atomizing chamber to soot buildup on the flame tube side. In addition, the use of generally straight walls instead of the generally cone shaped fire wall of Fig. 4 ~inimizes the tendency for soot buildup since in the configura-tion of FigO 4, the number of corners involved makes it difficult to provide sufficient air mixing to all of the corners The use of a substant.ially planar faced fire wall removes the restriction on the minimum spray angle as stated for the sprays in Fig. 4. The use of the planar face fire wall permits the minimum included angle where sprays meet to be reduced substantially.
The preferred minimum included angle is about 5.
Excellent results have been achieved with an angle of about 27.
The centrifugal swirl shutters or louvers 50 promote rapid mixing of combustion air and fuel spray to prevent soot buildup on the flame tube 3~ The air which passes into the flame tube through the centri-fugal swirl shutters provides a curtain of swirling air along the flame tube wall. rrhis i.nsulates t:he flame tube wall from direct ~lame impin~ementand prevents hot spots and 113~719 ~26-flame erosion problems. The curtain of swirling air is heaviest in the upstream vicinity of the flame tube where it enters through the louvers. When the swirling air encounters the transverse air blasts about midway along the flame tube from apertures 12,12', and again at the discharge lip ~f the flame tube from cutouts 13,13', the swirling motion is sub-stantially destroyed. This is important to assure that the swirling air is mixed with the vaporized and burning fuel before it exits flame tube 3.
It was discussed hereinabove with respect to Fig. 3 that the spray discharge horn 17' served two purposes. Horn 17' was designed to control the mass median diameter of the spray entering flame tube 3 and also to prevent the flame within flame tube 3 from pxopagati.ng upstream and into atomizing chamber 15. The spray particle size can be optimized by ad-justing the geometry of horn 17' with respect to its length, exit diameter and conical angle. Said horn can be sized such that the spray issuing forth from ori~ice 29' i9 disch~r~ed into flame tube 3 unrestricted by horn 17', or said horn may be designed to restxict a portion of the spray emanatin~ from 29', In this latter c~se, the inner walls of said horn serve to skim off the lar~er spray particles on the outer periphery of the spray plume, These captured fuel particles simply flow back into atomizing chamber 15 along the inclined inner walls of said spray discharge horn 17'.
This technique works ~ell when the skimming required is minimal, and when the ~elocity of the commingled air and fuel particles passing through said horn is low.
However, when it is desired to restrict a ~ubstantial amount o~ the spray to further reduce particle size, or when velocities within discharge ho~n 17' axe hi~h~
11307~9 the discharge horn assembly shown in Fig. 6 is more useful. This high velocity discharqe horn assembly 20 is comprised of an inner shroud 17' and an outer shroud 22. As shown in Fig. 6 the down-stream ends of these shrouds are preferably in the same plane.
However, in some cases, depending upon the static pressure, com-bustion air velocity, and local eddies within flame tube 3, outer shroud 22 may be somewhat longer or shorter than inner shroud 17' to promote better drainback and/or to eliminate soot buildup between said shrouds or around the entire configuration 20'.
In operation the high velocity discharge horn assembly 20 shown in Fig. 6 skims off a portion of the fuel spray originating from orifice 29'.
The relatively high velocity of the spray passing through inner shroud 17' causes impinging fuel to run along the inner walls of shroud 17' towards the flame tube. This raw fuel is prevented from spilling over into the flame tube by means of the outer shroud 22. Said raw fuel upon reaching the discharge lip of the inner shroud 17' runs back between said inner shroud and said outer shroud 22, mostly along the outer surEace of thc inner shroud 17, and back towards the forward wall 28 o~ the atomi~inc3 chamber 15.
This excess or run-off fue~1 then drains back into chamber 15 via small drain tub~ 72. Durinc~ burner operation, drain tube 72 which has an I.D. of appro~imately 1/16-1/8" becomes filled with fuel and acts as a trap to prevent the back flow of combustion products into the atomizing chamber.
The other purpose of high velocity discharge horn assembly 20 is to prevent burn back in the atomizing chamber. Essentially the assembly acts as an ejector which is sized such that the fuel/air velocity exiting from said inner shroud 17' is at least as 27 ~
~3~7~9 great as the flame speed of the fuel burning within - 27a --2~-flame tube 3, This means that the ~lame within the flame tube cannot propagate upstream and into atomiziny chamber 15'.
In cases where the velocity of commingled liquid spray and air exiting from discharge horn assembly 20' is very high so as to cause flame in-stability or a fluctuating flame front within the flame tube 3, then flame holder 71 may be provide~. Said flame holder is in the form of a simple ring or washer having a large central opening 63, said opening being sized slightly larger than that of the spr~y plume diameter at that point. 'rhis allows the fuel spray to pass unimpeded through saia opening 63 without wetting the walls of said flame holder 71.
The turbulence and subsequent low static pressure that is created around flame holder 71 when the spray passes through it, causes the flame to seat or attach itself to the downstream face of flame holder 71. In Fig. 6 said flame holder 71 is supported from outer shroud 22 ~ two small rod like appendages 62. ~t i5 desir-able that these rods 62 be small in cross-section so that flame holder 71 takes on the appearance Qf be.ing suspended in space approximately 1/8 - 1.-1/2" down-stream of the exit oE inner shroud 17'. The exact loca-tion of flame holder 71 will depend upon the relativevelocity between the flame speed and the fuel/air mi.x-ture leaving shroud 17'.
Having described a pre~erred mode of practicing the invention, it will be apparent to those ~killed in the art that Various modifications and changes can be made therein; which modification and changes fall within the purview of the inventive concept defi~ed by the ap-pended claims wherein what is claimed is:
Claims (13)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A liquid fuel burner comprising:
a flame tube having an inlet end and an outlet end, an atomizing chamber communicating with said inlet end of said flame tube and enclosing fuel atomizing means for discharging atomized fuel into said flame tube through openings in a dividing wall separating said flame tube from said atomizing chamber, said atomizing means comprising a plurality of hollow plenum chambers each having a smooth outer surface and each de-fining therein a small through aperture, a means for producing a flow of fuel in a thin film over each said through aperture and a means for introducing air under pressure into each said plenum chamber to rupture said film at said aperture.
' means for supporting said plenum chambers in said atomizing chamber in a manner to cause the plurality of direction-al streams of atomized fuel issuing therefrom to be directed through respective ones of said openings in said dividing wall into said flame tube in directions extending along the central axis of said flame tube for combustion of substantially all said atomized fuel within said flame tube, means for introducing air into said atomizing cham-ber to thereby cause low velocity air to issue through said open-ings in said dividing wall along with said streams of atomized fuel and said air issuing from each said plenum chamber, means for igniting the atomized fuel in said flame tube downstream of its said inlet end, first means for introducing air into said flame tube adjacent its inlet end with a tangential component to produce in said flame tube a single tangential vortex to promote the admix-ing of air with the atomized fuel and to maintain the flame spaced from the flame tube's inner surface adjacent its inlet end, and second means for introducing air into said flame tube at at least one location downstream of the location of air introduction by said first means and downstream of the point of ig-nition of the fuel-air mixture by said ignition means with a veloc-ity and direction to impede the tangential vortex generated by said first means so as to permit the flame to expand to the flame tube wall and to permit substantially complete combustion within the confines of the flame tube.
a flame tube having an inlet end and an outlet end, an atomizing chamber communicating with said inlet end of said flame tube and enclosing fuel atomizing means for discharging atomized fuel into said flame tube through openings in a dividing wall separating said flame tube from said atomizing chamber, said atomizing means comprising a plurality of hollow plenum chambers each having a smooth outer surface and each de-fining therein a small through aperture, a means for producing a flow of fuel in a thin film over each said through aperture and a means for introducing air under pressure into each said plenum chamber to rupture said film at said aperture.
' means for supporting said plenum chambers in said atomizing chamber in a manner to cause the plurality of direction-al streams of atomized fuel issuing therefrom to be directed through respective ones of said openings in said dividing wall into said flame tube in directions extending along the central axis of said flame tube for combustion of substantially all said atomized fuel within said flame tube, means for introducing air into said atomizing cham-ber to thereby cause low velocity air to issue through said open-ings in said dividing wall along with said streams of atomized fuel and said air issuing from each said plenum chamber, means for igniting the atomized fuel in said flame tube downstream of its said inlet end, first means for introducing air into said flame tube adjacent its inlet end with a tangential component to produce in said flame tube a single tangential vortex to promote the admix-ing of air with the atomized fuel and to maintain the flame spaced from the flame tube's inner surface adjacent its inlet end, and second means for introducing air into said flame tube at at least one location downstream of the location of air introduction by said first means and downstream of the point of ig-nition of the fuel-air mixture by said ignition means with a veloc-ity and direction to impede the tangential vortex generated by said first means so as to permit the flame to expand to the flame tube wall and to permit substantially complete combustion within the confines of the flame tube.
2. The burner of claim 1 in which a foraminous radiation shield is supported adjacent to but spaced from the side of said dividing wall facing said flame tube.
3. The burner of claim 2 which further includes a spray discharge cone for each said plenum chamber, each said spray dis-charge cone being truncated with its larger end adjacent the through aperture of the respective plenum chamber and extending through said respective opening in said dividing wall and said radiation shield.
4. The burner of claim 2 in which both said shield and said dividing wall define a central aperture for producing a flow of air from a source of pressurized air along the central axis of said flame tube.
5. The burner of claim 4 which further includes a cent-ral tube extending from said air source through said apertures in said dividing wall and shield and into said inlet end of said flame tube.
6. The burner of claim 1 in which said first means com-prises a plurality of louvers formed in said flame tube wall.
7. The burner of claims 1 or 6 in which said second means comprises a plurality of apertures in said flame tube dis-posed substantially at the mid-length thereof.
8. The burner of claims 1 or 6 in which said second means comprises a plurality of apertures in said flame tube sub-stantially at its outlet end.
9. The burner of claims 1 or 2 in which said second means comprises a first plurality of apertures in said flame tube substantially at the mid-length thereof and a second plurality of apertures in said flame tube substantially at its said outlet end.
10. The burner of claim 1 which further includes means for pressurizing said atomizing chamber with a pressure above atmospheric.
11. The burner of claim 10 which further includes air channel means for conveying air via said first and second means to the interior of said flame tube.
12. The burner of claim 11 in which said air channel means includes a tube of larger diameter than, and surrounding, said flame tube to define an annular channel.
13. A liquid fuel burner comprising:
a flame tube having an inlet end and an outlet end, an atomizing chamber communicating with said inlet end of said flame tube and enclosing fuel atomizing means for dis-charging atomized fuel into said flame tube through openings in a dividing wall separating said flame tube from said atomizing chamber, said atomizing means comprising a plurality of hollow plenum chambers each having a smooth outer surface and each de-fining therein a small through aperture, means for producing a flow of fuel in a thin film over each said through aperture and a means for introducing air under pressure into each said plenum chamber to rupture said film at said aperture, means for supporting said plenum chambers in said atomizing chamber in a manner to cause the plurality of directional streams of atomized fuel issuing therefrom to be directed through respective ones of said openings in said dividing wall into said flame tube in directions extending along the central axis of said flame tube, means for pressurizing said atomizing chamber with above atmospheric pressure to thereby cause low velocity air to issue through said openings in said dividing wall along with said streams of atomized fuel, means for igniting the atomized fuel in said flame tube downstream of its said inlet end, and means for introducing air into said flame tube at at least one location along its length for admixing with the atomized fuel.
a flame tube having an inlet end and an outlet end, an atomizing chamber communicating with said inlet end of said flame tube and enclosing fuel atomizing means for dis-charging atomized fuel into said flame tube through openings in a dividing wall separating said flame tube from said atomizing chamber, said atomizing means comprising a plurality of hollow plenum chambers each having a smooth outer surface and each de-fining therein a small through aperture, means for producing a flow of fuel in a thin film over each said through aperture and a means for introducing air under pressure into each said plenum chamber to rupture said film at said aperture, means for supporting said plenum chambers in said atomizing chamber in a manner to cause the plurality of directional streams of atomized fuel issuing therefrom to be directed through respective ones of said openings in said dividing wall into said flame tube in directions extending along the central axis of said flame tube, means for pressurizing said atomizing chamber with above atmospheric pressure to thereby cause low velocity air to issue through said openings in said dividing wall along with said streams of atomized fuel, means for igniting the atomized fuel in said flame tube downstream of its said inlet end, and means for introducing air into said flame tube at at least one location along its length for admixing with the atomized fuel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA327,819A CA1130719A (en) | 1979-05-17 | 1979-05-17 | Liquid fuel burners |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA327,819A CA1130719A (en) | 1979-05-17 | 1979-05-17 | Liquid fuel burners |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1130719A true CA1130719A (en) | 1982-08-31 |
Family
ID=4114223
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA327,819A Expired CA1130719A (en) | 1979-05-17 | 1979-05-17 | Liquid fuel burners |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1130719A (en) |
-
1979
- 1979-05-17 CA CA327,819A patent/CA1130719A/en not_active Expired
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4298338A (en) | Liquid fuel burners | |
| CA1098022A (en) | Geyseric burner assembly and method for combusting fuels | |
| CA1119506A (en) | Low nox burner | |
| US4013396A (en) | Fuel aerosolization apparatus and method | |
| US4748919A (en) | Low nox multi-fuel burner | |
| US3605405A (en) | Carbon elimination and cooling improvement to scroll type combustors | |
| US4245980A (en) | Burner for reduced NOx emission and control of flame spread and length | |
| US4640674A (en) | Pulse combustion apparatus | |
| PL181074B1 (en) | Process and apparatus for drying and heating | |
| US4298337A (en) | Fuel burner having flame stabilization by internal recirculation | |
| US2560074A (en) | Method and apparatus for burning fuel | |
| US2665748A (en) | Fuel burner | |
| US4155700A (en) | Liquid fuel burners | |
| US4286945A (en) | Wall fired duct heater | |
| US4462795A (en) | Method of operating a wall fired duct heater | |
| US2923348A (en) | Fuel combustion apparatus | |
| USRE28679E (en) | Burners | |
| CA1130719A (en) | Liquid fuel burners | |
| US3751210A (en) | Two-stage vaporizing fuel oil burner | |
| EP0019022B1 (en) | Liquid fuel burners | |
| CA1203435A (en) | Solid fuel pulverizing and burning system and method and pulverizer and burner therefor | |
| US4369027A (en) | Liquid fuel combustion apparatus | |
| RU2083921C1 (en) | Rotary burner for liquid fuel | |
| US4280806A (en) | Prevaporizing oil burner and method | |
| GB2049910A (en) | Improvements in liquid fuel burners |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |