CA2215673A1 - Burner head for liquid fuels - Google Patents
Burner head for liquid fuels Download PDFInfo
- Publication number
- CA2215673A1 CA2215673A1 CA 2215673 CA2215673A CA2215673A1 CA 2215673 A1 CA2215673 A1 CA 2215673A1 CA 2215673 CA2215673 CA 2215673 CA 2215673 A CA2215673 A CA 2215673A CA 2215673 A1 CA2215673 A1 CA 2215673A1
- Authority
- CA
- Canada
- Prior art keywords
- blades
- air
- burner
- tube
- swirler
- 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.)
- Abandoned
Links
- 239000000446 fuel Substances 0.000 title claims abstract description 18
- 239000007788 liquid Substances 0.000 title claims abstract description 8
- 238000002485 combustion reaction Methods 0.000 claims abstract description 32
- 239000000203 mixture Substances 0.000 claims abstract description 9
- 238000011144 upstream manufacturing Methods 0.000 claims description 13
- 238000000889 atomisation Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- 239000000295 fuel oil Substances 0.000 description 4
- 230000006641 stabilisation Effects 0.000 description 3
- 238000011105 stabilization Methods 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 239000000567 combustion gas Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C7/00—Combustion apparatus characterised by arrangements for air supply
- F23C7/002—Combustion apparatus characterised by arrangements for air supply the air being submitted to a rotary or spinning motion
- F23C7/004—Combustion apparatus characterised by arrangements for air supply the air being submitted to a rotary or spinning motion using vanes
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
- F23D11/10—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space the spraying being induced by a gaseous medium, e.g. water vapour
- F23D11/101—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space the spraying being induced by a gaseous medium, e.g. water vapour medium and fuel meeting before the burner outlet
- F23D11/102—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space the spraying being induced by a gaseous medium, e.g. water vapour medium and fuel meeting before the burner outlet in an internal mixing chamber
- F23D11/103—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space the spraying being induced by a gaseous medium, e.g. water vapour medium and fuel meeting before the burner outlet in an internal mixing chamber with means creating a swirl inside the mixing chamber
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Pressure-Spray And Ultrasonic-Wave- Spray Burners (AREA)
Abstract
A fuel burner is provided for introducing liquid fuel and air into a combustion furnace. An air tube (40) is disposed about a jet tube (36) adapted to supply a fuel-air mixture to the combustion chamber. The annular passage (10) formed between the air tube (40) and the jet tube (36) merges into an annular outlet port (22) defined by a constricting conical wall (24) to converge the flow of primary air into the combustion chamber. Swirler means comprising a plurality of swirler blades (20) are arranged in the annular passage to impart a vortex motion to the converging primary air flow.
Description
CA 0221~673 1997-09-12 Canadian Patent Application Kurt Skoog - KLS-016-CA PO/MC/hl BURNER HEAD FOR LIOUID FUELS
The invention relates to a burner for introducing liquid fuels to be mixed with air into a combustion chamber, preferably for the combustion of fuel oils of various grades.
The US patent 4,726,760 discloses a burner head of the present type, in which a tubular jet body terminates in a nozzle piece for supplying fuel oil to be mixed with air and introduced into a combustion chamber. Another conventional apparatus is shown in Fig. 1 where the jet body 36 is disposed along the axial or flow direction 26, the jet body ending with a nozzle piece 50 provided with fuel outlet ports. The jet body 36 is surrounded by two gas and/or air passages 14, 18. The inner passage 14 opens into the combustion chamber 16 via the annular inlet port 24.
The primary combustion air exiting the inlet port 24 diverges conically from the nozzle 50 when entering the combustion chamber 16.
The outer annular passage 18 is defined by the outer jacket 39 and an inner jacket 38 disposed between the jet tube 36 and the outer jacket 39. The second annular outlet port 28 is defined by conical side walls so as to form a converging conical flow of combustion air, which intersects the expanding flow from the first outlet port 24. Swirl baffles 36, 37 are provided in the inner and outer passages 14, 18, which give a vortex motion to the respective flows.
In the conventional device of Fig. 1, liquid fuel exits from the nozzle 50 and atomization is caused by the turbulence caused from the intersection of primary and secondary air flows from the coaxially arranged inner and CA 0221~673 1997-09-12 outer passages 14, 18. The fuel-air mixing takes place relatively distant from the nozzle 50 as the gases are already in the combustion chamber. At greater distances from the outlet ports 24, 28, the mixing air has lost some of its kinetic energy. The degree of atomization of the liquid fuel is therefore reduced. In addition, the provision of two air inlet passages 14, 18 requires the additional fabrication of the inner jacket 38, associated baffles. In operation, the air supply pressures in the air supply passages 14, 18 as well as the fuel supply pressure in the passage 54 of the jet body have to be carefully adjusted with respect to one another to obtain optimal combustion characteristics.
It is therefore an object of the present invention to provide a burner apparatus for liquid fuels by which atomization of the fuel can be improved and by which the manufacturing costs and adjustment time in operating the burner can be reduced.
Another object of the present invention is to provide improved swirler means by which the internal circulation and stabilization of the flame can be improved.
SUMMARY OF THE INVENTION
In accordance with the present invention, a burner for liquid fuels is provided, preferably for heating oils or oils of various grades. The burner comprises a nozzle arranged on the downstream end of a jet tube, the nozzle being adapted to supply a fuel air mixture to the combustion chamber. An air tube is disposed about the jet tube to form a single annular passage therebetween. The annular passage terminates in an annular outlet port defined by a constricting conical wall of the air tube. The CA 0221~673 1997-09-12 primary combustion air is thereby introduced into the combustion chamber in a converging flow. Swirler means are disposed in the same annular passage and comprise a plurality of blades arranged concentrically about the jet tube. The swirler blades are arranged prior to the annular outlet port to impart a vortex motion to the converging combustion air flow.
The outer wall of the jet tube preferably comprises an expanding conical wall portion located upstream of the constricting conical wall defining the outlet port. The expanding conical wall reduces the flow cross section in the annular combustion air passage thereby creating a Venturi effect. The exit flow velocity of the combustion air is thereby increased to promote increased atomization.
The nozzle 50 of the jet tube 36 is preferably constructed to supply a primary fuel-air mixture, whereas the combustion air from the annular passage forms and stabilizes the flame.
In addition to the reduction of the flow cross-section caused by the walls of the annular passage, the blades of the swirler means are preferably arranged to provide a further Venturi effect. The outlet area between two 2s adjacent blades at their downstream end is 40 to 95~, preferably 60 to 80~ of the area between the adjacent blades at their upstream end. The swirler blades have a pitch relative to the flow direction or to the axial direction of the jet body which is preferably in the range of 40~ to 70~. The length of the blades is selected such that the amount of turn of each blade about the axial direction, from the upstream end to the downstream end, is in the range of 50~ to 70~. Furthermore, the downstream ends of the individual blades are disposed at a position prior to the outlet opening of the nozzle of the jet body.
CA 0221~673 1997-09-12 An under pressure produced by the swirler means at the tip of the swirler blades enhances stabilization of the flame.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail with reference to embodiments of the burner as illustrated in the drawings.
Fig. 1 shows a cross-sectional view along the longitudinal axis of a conventional burner.
Fig. 2 shows a cross-sectional view along the longitudinal axis of a burner according to an embodiment of the present invention.
Fig. 3 shows a side view of an embodiment of the swirler means shown in Fig. 2.
Fig. 4 shows a cross-sectional view along the line I-I of Fig. 3.
Fig. 5 shows a plan view looking down the longitudinal axis of the swirler means of Fig. 3.
Fig. 6 shows a schematic illustration of the design of the swirler blades.
Fig. 7 shows a schematic illustration of air flow between the swirler blades.
A first embodiment of the present invention is illustrated in Fig. 2. The jet body 36 comprises an outer tubular wall 41, the downstream end of which joins to an expanding conical wall portion 26. A nozzle 50 is secured to the downstream end of the expanding wall 26. A second tube 53 is coaxially mounted within the jet tube forming a passage 54 for supply of fuel oil to the nozzle 50. The outer passage 55 within the jet tube 36 supplies gas and/or air to side inlets 44 of the nozzle 50. Fuel and air are then mixed within a mixing space 40, after which the mixture CA 022l~673 l997-09-l2 leaves the nozzle 50 through the nozzle opening 10. Various arrangements of the fuel oil inlets and the side air inlets 44 are possible. Important is the premixture of fuel and air performed by the nozzle. The creation of the fuel-air mixture is such that it leaves the opening 10 with a vortex motion as it moves towards the combustion chamber 16.
An air tube 40 is disposed about the outer wall 41 of the jet tube 36, whereby a single annular passage 10 is formed therebetween. At its downstream end, the air tube 40 is formed with a constricting conical wall 24, which defines one side wall of the annular outlet port 22. The conical surface 24 causes the primary combustion air supplied by the passage 10 to converge and intersect with the fuel air mixture emanating from the nozzle opening 10.
The expanding conical wall 26 of the outer wall 41 iS
disposed upstream of the constricting conical wall 24 in axial direction. In the embodiment of Fig. 2, the axial extension of the expanding wall 26 partially overlaps the axial extension of the constricting wall 24. In any case, the expanding conical wall 26 should begin before the onset of the constricting wall 24. The end wall 28 joining the expanding wall 26 defines the other side wall of the annular outlet port 22. As can be seen from the spacing between the constricting wall 24 and the end wall 28 of the outlet 22, the flow cross-section of the annular passage 10 is reduced compared to its value further upstream. The Venturi effect produced increases the exit velocity of the primary air to be provided for combustion and for flame formation and other flame characteristics.
Swirler means are provided in the single annular passage 10 which comprise blades 20 fixed to a sleeve 30. The blades 20 have an axial extension which includes the expanding CA 0221~673 1997-09-12 wall 26 as well as the constricting conical wall 24. The blades 20 are concentrically arranged about the jet tube 36 and have a pitch to impart a vortex motion of the converging flow exiting from the outlet 22. Thus the combustion air is imparted with increased speed due to the Venturi effect as well as a rotational component due to the swirler means as it exits the air tube 40. With the nozzle 50 being adapted to supply a fuel-air mixture, the converged vortex flow from the outlet port 22 is sufficient for further atomization of the fuel-air mixture and is particularly suited for flame formation.
A side view of the swirler means is shown schematically in Fig. 3. Only the blades on the front side of the device are shown. Fig. 4 shows a cross-section of the swirler means at the line I-I. As can be seen, the blades 20 are welded to the outer surface of the sleeve 30 at a predetermined angular disposition. In this embodiment, eight blades are arranged concentrically about the sleeve 30 at an equal angular spacing of 45~. The number of blades will normally depend upon the diameter of the jet tube 36. Preferably six to twenty blades will be provided at equal spacing.
Fig. 5 shows a plan view looking down the axis of the jet tube. As can be seen, the upstream end a of the blades has a radial extension which corresponds approximately to the radial dimension of the angular passage 10 shown in Fig. 2.
The radial extension of each blade then decreases toward the downstream end d to match the reduced radial dimension of the annular outlet port 22. Generally, the fit of the individual blades to the dimensions of the annular passage 10 is close but not tight with the internal dimensions of the annular passage 10.
CA 0221~673 1997-09-12 Fig. 6 shows an illustration of the geometry of the blades individually and with respect to one another. The illustration represents a composite of side views of several blades taken to look down the edge of each blade as one moves around the swirler means. As can be seen in Fig. 6, each blade 20 is formed to have a pitch ~, which is preferably in the range of 40~ to 70~. The solid lines of Fig. 6 represent a 50~ pitch while the dashed lines represent a 70~ pitch. The selection of the pitch will influence the additional Venturi effect caused by the blades. As seen in Fig. 4, the area A1 between two adjacent blades at the upstream end a of the blades will be approximately rectangular. Depending on the pitch of the blades, the area A2 illustrated in Fig. 6 between the adjacent blades at their downstream end will be smaller than A1. The higher the pitch, the closer the two adjacent blades are to one another as can be seen by comparing the spacing A2 between two blades having a pitch of 50~ with the spacing A'2 between adjacent blades having a pitch of 70~ (dashed lines of Fig. 6). The pitch of the blades is selected such that the ratio between the outlet area A2 between two adjacent blades is 40~ to 95~ of the area A
between the adjacent blades at their upstream end.
Preferably, the ratio of the outlet area to inlet area is 60~ to 80~.
The length of the pitched or spiral portion b shown in Fig. 6 determines the amount of turn c of each blade about the axis of the swirler means. An amount of turn is best illustrated in Fig. 5 where c shows the turn to be the angular reach of a given blade 20 from its upstream end a to the downstream end d. In the embodiment, with a spacing of the blades being 45~, the turn of the blades is about 65~. This is also illustrated with the numeral c in Fig. 3.
As can be seen from the figures, one blade extends over and CA 0221~673 1997-09-12 above at least a portion of its adjacent blade. According to the invention, it has been found that the turn of each blade should be in the range of 50~ to 70~. Expressed in terms of the spacing between adjacent blades, the turn should be between 1.5 and 2 times the spacing between the blades.
As indicated above, the pitch ~ of the individual blades should be in the range of 40~ to 70~. A higher pitch creates a higher swirl number or vorticity which results in a strong internal recirculation of the hot gases of the flame. This makes the flame shorter and wider and provides good fuel atomization. On the other hand, when the pitch is higher than 70~, combustion noise increases caused by the strong turbulent character of the flame.
When a longer and narrower flame is desired for a particular combustion furnace, the pitch is made to be lower. When the pitch is lower than 40~, the recirculation of combustion gases in the flame is reduced leading to less efficient combustion. According to the invention, it has been found that when the swirler blades are dimensioned as defined above, the flame has an optimal internal recirculation which allows a high combustion efficiency.
Fig. 7 illustrates schematically the flow of combustion air between adjacent swirler blades 20 and 20'. The air streams entering at the inlet end a are urged by centrifugal force toward the internal surface of the first blade 20. At the same time, the air streams move away from the external surface of the second blade 20'. This creates an over pressure indicated with a + in Fig. 7. An under pressure is created at the exit of the second blade 20'. This under pressure holds the flame at the exit opening 10 of the nozzle 50 as shown in Fig. 2. For this reason also, the CA 0221~673 1997-09-12 downstream ends d of the swirler blades should be disposed at a position upstream of the outlet opening 10 of the nozzle 50 as shown in Fig. 2. The creation of the under pressure with the swirler construction according to the present invention thus provides flame stabilization in addition to the improved internal gas recirculation of the flame mentioned above.
The invention relates to a burner for introducing liquid fuels to be mixed with air into a combustion chamber, preferably for the combustion of fuel oils of various grades.
The US patent 4,726,760 discloses a burner head of the present type, in which a tubular jet body terminates in a nozzle piece for supplying fuel oil to be mixed with air and introduced into a combustion chamber. Another conventional apparatus is shown in Fig. 1 where the jet body 36 is disposed along the axial or flow direction 26, the jet body ending with a nozzle piece 50 provided with fuel outlet ports. The jet body 36 is surrounded by two gas and/or air passages 14, 18. The inner passage 14 opens into the combustion chamber 16 via the annular inlet port 24.
The primary combustion air exiting the inlet port 24 diverges conically from the nozzle 50 when entering the combustion chamber 16.
The outer annular passage 18 is defined by the outer jacket 39 and an inner jacket 38 disposed between the jet tube 36 and the outer jacket 39. The second annular outlet port 28 is defined by conical side walls so as to form a converging conical flow of combustion air, which intersects the expanding flow from the first outlet port 24. Swirl baffles 36, 37 are provided in the inner and outer passages 14, 18, which give a vortex motion to the respective flows.
In the conventional device of Fig. 1, liquid fuel exits from the nozzle 50 and atomization is caused by the turbulence caused from the intersection of primary and secondary air flows from the coaxially arranged inner and CA 0221~673 1997-09-12 outer passages 14, 18. The fuel-air mixing takes place relatively distant from the nozzle 50 as the gases are already in the combustion chamber. At greater distances from the outlet ports 24, 28, the mixing air has lost some of its kinetic energy. The degree of atomization of the liquid fuel is therefore reduced. In addition, the provision of two air inlet passages 14, 18 requires the additional fabrication of the inner jacket 38, associated baffles. In operation, the air supply pressures in the air supply passages 14, 18 as well as the fuel supply pressure in the passage 54 of the jet body have to be carefully adjusted with respect to one another to obtain optimal combustion characteristics.
It is therefore an object of the present invention to provide a burner apparatus for liquid fuels by which atomization of the fuel can be improved and by which the manufacturing costs and adjustment time in operating the burner can be reduced.
Another object of the present invention is to provide improved swirler means by which the internal circulation and stabilization of the flame can be improved.
SUMMARY OF THE INVENTION
In accordance with the present invention, a burner for liquid fuels is provided, preferably for heating oils or oils of various grades. The burner comprises a nozzle arranged on the downstream end of a jet tube, the nozzle being adapted to supply a fuel air mixture to the combustion chamber. An air tube is disposed about the jet tube to form a single annular passage therebetween. The annular passage terminates in an annular outlet port defined by a constricting conical wall of the air tube. The CA 0221~673 1997-09-12 primary combustion air is thereby introduced into the combustion chamber in a converging flow. Swirler means are disposed in the same annular passage and comprise a plurality of blades arranged concentrically about the jet tube. The swirler blades are arranged prior to the annular outlet port to impart a vortex motion to the converging combustion air flow.
The outer wall of the jet tube preferably comprises an expanding conical wall portion located upstream of the constricting conical wall defining the outlet port. The expanding conical wall reduces the flow cross section in the annular combustion air passage thereby creating a Venturi effect. The exit flow velocity of the combustion air is thereby increased to promote increased atomization.
The nozzle 50 of the jet tube 36 is preferably constructed to supply a primary fuel-air mixture, whereas the combustion air from the annular passage forms and stabilizes the flame.
In addition to the reduction of the flow cross-section caused by the walls of the annular passage, the blades of the swirler means are preferably arranged to provide a further Venturi effect. The outlet area between two 2s adjacent blades at their downstream end is 40 to 95~, preferably 60 to 80~ of the area between the adjacent blades at their upstream end. The swirler blades have a pitch relative to the flow direction or to the axial direction of the jet body which is preferably in the range of 40~ to 70~. The length of the blades is selected such that the amount of turn of each blade about the axial direction, from the upstream end to the downstream end, is in the range of 50~ to 70~. Furthermore, the downstream ends of the individual blades are disposed at a position prior to the outlet opening of the nozzle of the jet body.
CA 0221~673 1997-09-12 An under pressure produced by the swirler means at the tip of the swirler blades enhances stabilization of the flame.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail with reference to embodiments of the burner as illustrated in the drawings.
Fig. 1 shows a cross-sectional view along the longitudinal axis of a conventional burner.
Fig. 2 shows a cross-sectional view along the longitudinal axis of a burner according to an embodiment of the present invention.
Fig. 3 shows a side view of an embodiment of the swirler means shown in Fig. 2.
Fig. 4 shows a cross-sectional view along the line I-I of Fig. 3.
Fig. 5 shows a plan view looking down the longitudinal axis of the swirler means of Fig. 3.
Fig. 6 shows a schematic illustration of the design of the swirler blades.
Fig. 7 shows a schematic illustration of air flow between the swirler blades.
A first embodiment of the present invention is illustrated in Fig. 2. The jet body 36 comprises an outer tubular wall 41, the downstream end of which joins to an expanding conical wall portion 26. A nozzle 50 is secured to the downstream end of the expanding wall 26. A second tube 53 is coaxially mounted within the jet tube forming a passage 54 for supply of fuel oil to the nozzle 50. The outer passage 55 within the jet tube 36 supplies gas and/or air to side inlets 44 of the nozzle 50. Fuel and air are then mixed within a mixing space 40, after which the mixture CA 022l~673 l997-09-l2 leaves the nozzle 50 through the nozzle opening 10. Various arrangements of the fuel oil inlets and the side air inlets 44 are possible. Important is the premixture of fuel and air performed by the nozzle. The creation of the fuel-air mixture is such that it leaves the opening 10 with a vortex motion as it moves towards the combustion chamber 16.
An air tube 40 is disposed about the outer wall 41 of the jet tube 36, whereby a single annular passage 10 is formed therebetween. At its downstream end, the air tube 40 is formed with a constricting conical wall 24, which defines one side wall of the annular outlet port 22. The conical surface 24 causes the primary combustion air supplied by the passage 10 to converge and intersect with the fuel air mixture emanating from the nozzle opening 10.
The expanding conical wall 26 of the outer wall 41 iS
disposed upstream of the constricting conical wall 24 in axial direction. In the embodiment of Fig. 2, the axial extension of the expanding wall 26 partially overlaps the axial extension of the constricting wall 24. In any case, the expanding conical wall 26 should begin before the onset of the constricting wall 24. The end wall 28 joining the expanding wall 26 defines the other side wall of the annular outlet port 22. As can be seen from the spacing between the constricting wall 24 and the end wall 28 of the outlet 22, the flow cross-section of the annular passage 10 is reduced compared to its value further upstream. The Venturi effect produced increases the exit velocity of the primary air to be provided for combustion and for flame formation and other flame characteristics.
Swirler means are provided in the single annular passage 10 which comprise blades 20 fixed to a sleeve 30. The blades 20 have an axial extension which includes the expanding CA 0221~673 1997-09-12 wall 26 as well as the constricting conical wall 24. The blades 20 are concentrically arranged about the jet tube 36 and have a pitch to impart a vortex motion of the converging flow exiting from the outlet 22. Thus the combustion air is imparted with increased speed due to the Venturi effect as well as a rotational component due to the swirler means as it exits the air tube 40. With the nozzle 50 being adapted to supply a fuel-air mixture, the converged vortex flow from the outlet port 22 is sufficient for further atomization of the fuel-air mixture and is particularly suited for flame formation.
A side view of the swirler means is shown schematically in Fig. 3. Only the blades on the front side of the device are shown. Fig. 4 shows a cross-section of the swirler means at the line I-I. As can be seen, the blades 20 are welded to the outer surface of the sleeve 30 at a predetermined angular disposition. In this embodiment, eight blades are arranged concentrically about the sleeve 30 at an equal angular spacing of 45~. The number of blades will normally depend upon the diameter of the jet tube 36. Preferably six to twenty blades will be provided at equal spacing.
Fig. 5 shows a plan view looking down the axis of the jet tube. As can be seen, the upstream end a of the blades has a radial extension which corresponds approximately to the radial dimension of the angular passage 10 shown in Fig. 2.
The radial extension of each blade then decreases toward the downstream end d to match the reduced radial dimension of the annular outlet port 22. Generally, the fit of the individual blades to the dimensions of the annular passage 10 is close but not tight with the internal dimensions of the annular passage 10.
CA 0221~673 1997-09-12 Fig. 6 shows an illustration of the geometry of the blades individually and with respect to one another. The illustration represents a composite of side views of several blades taken to look down the edge of each blade as one moves around the swirler means. As can be seen in Fig. 6, each blade 20 is formed to have a pitch ~, which is preferably in the range of 40~ to 70~. The solid lines of Fig. 6 represent a 50~ pitch while the dashed lines represent a 70~ pitch. The selection of the pitch will influence the additional Venturi effect caused by the blades. As seen in Fig. 4, the area A1 between two adjacent blades at the upstream end a of the blades will be approximately rectangular. Depending on the pitch of the blades, the area A2 illustrated in Fig. 6 between the adjacent blades at their downstream end will be smaller than A1. The higher the pitch, the closer the two adjacent blades are to one another as can be seen by comparing the spacing A2 between two blades having a pitch of 50~ with the spacing A'2 between adjacent blades having a pitch of 70~ (dashed lines of Fig. 6). The pitch of the blades is selected such that the ratio between the outlet area A2 between two adjacent blades is 40~ to 95~ of the area A
between the adjacent blades at their upstream end.
Preferably, the ratio of the outlet area to inlet area is 60~ to 80~.
The length of the pitched or spiral portion b shown in Fig. 6 determines the amount of turn c of each blade about the axis of the swirler means. An amount of turn is best illustrated in Fig. 5 where c shows the turn to be the angular reach of a given blade 20 from its upstream end a to the downstream end d. In the embodiment, with a spacing of the blades being 45~, the turn of the blades is about 65~. This is also illustrated with the numeral c in Fig. 3.
As can be seen from the figures, one blade extends over and CA 0221~673 1997-09-12 above at least a portion of its adjacent blade. According to the invention, it has been found that the turn of each blade should be in the range of 50~ to 70~. Expressed in terms of the spacing between adjacent blades, the turn should be between 1.5 and 2 times the spacing between the blades.
As indicated above, the pitch ~ of the individual blades should be in the range of 40~ to 70~. A higher pitch creates a higher swirl number or vorticity which results in a strong internal recirculation of the hot gases of the flame. This makes the flame shorter and wider and provides good fuel atomization. On the other hand, when the pitch is higher than 70~, combustion noise increases caused by the strong turbulent character of the flame.
When a longer and narrower flame is desired for a particular combustion furnace, the pitch is made to be lower. When the pitch is lower than 40~, the recirculation of combustion gases in the flame is reduced leading to less efficient combustion. According to the invention, it has been found that when the swirler blades are dimensioned as defined above, the flame has an optimal internal recirculation which allows a high combustion efficiency.
Fig. 7 illustrates schematically the flow of combustion air between adjacent swirler blades 20 and 20'. The air streams entering at the inlet end a are urged by centrifugal force toward the internal surface of the first blade 20. At the same time, the air streams move away from the external surface of the second blade 20'. This creates an over pressure indicated with a + in Fig. 7. An under pressure is created at the exit of the second blade 20'. This under pressure holds the flame at the exit opening 10 of the nozzle 50 as shown in Fig. 2. For this reason also, the CA 0221~673 1997-09-12 downstream ends d of the swirler blades should be disposed at a position upstream of the outlet opening 10 of the nozzle 50 as shown in Fig. 2. The creation of the under pressure with the swirler construction according to the present invention thus provides flame stabilization in addition to the improved internal gas recirculation of the flame mentioned above.
Claims (8)
1. A burner for introducing liquid fuel and air into a combustion chamber comprising,:
a nozzle (50) arranged in flow direction on the downstream end of a jet tube (36) and adapted to supply a fuel-air mixture to the combustion chamber (16), an air tube (40) disposed about an outer wall (41) of the jet tube (36) to form a single annular passage (10) between the air tube (40) and the jet tube (36), the annular passage (10) merging into an annular outlet port (22) defined by a constricting conical wall (24) of the air tube (40) to generate a converging flow of combustion air into the combustion chamber (16), swirler means comprising a plurality of blades (20) arranged concentrically about the jet tube (36) and disposed in the annular passage (10) prior to the annular port (22) to impart a vortex motion to the converging flow.
a nozzle (50) arranged in flow direction on the downstream end of a jet tube (36) and adapted to supply a fuel-air mixture to the combustion chamber (16), an air tube (40) disposed about an outer wall (41) of the jet tube (36) to form a single annular passage (10) between the air tube (40) and the jet tube (36), the annular passage (10) merging into an annular outlet port (22) defined by a constricting conical wall (24) of the air tube (40) to generate a converging flow of combustion air into the combustion chamber (16), swirler means comprising a plurality of blades (20) arranged concentrically about the jet tube (36) and disposed in the annular passage (10) prior to the annular port (22) to impart a vortex motion to the converging flow.
2. The burner of Claim 1, wherein the outer wall (41) of the jet tube (36) comprises an expanding conical wall (26) located upstream of the constricting conical wall (24) of the air tube (40), the expanding conical wall (26) reducing the flow cross section in the annular passage (10) prior to reaching the constricting conical wall (24).
3. The burner of Claim 2, wherein the swirler blades (20) have an axial extension in flow direction to include both the expanding and constricting conical walls (26, 24) defining the single annular passage (10).
4. The burner of Claim 1, 2 or 3, wherein the swirler blades (20) have a pitch (.alpha.) relative to the flow direction in the range of 40° to 70°.
5. The burner of any one of the Claims 1 to 4, wherein the amount of turn (c) of each blade (20) about the axial direction from the upstream end to the downstream end, is in the range of 50° to 70°.
6. The burner of any one of the Claims 1 to 5, wherein the outlet area (A2) between two adjacent blades (20) at their downstream end is 40 - 95% of the inlet area (A1) between the adjacent blades (20) at their upstream end, preferably 60 to 80%.
7. The burner of any one of the Claims 1 to 6, wherein the downstream ends of the blades (20) are disposed at a position in flow direction prior to the outlet opening (10) of the nozzle (50).
8. The burner of any one of the Claims 1 to 7, wherein the swirler means comprises 6 to 20 blades (20) arranged concentrically about the jet body (36).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2215673 CA2215673A1 (en) | 1997-09-12 | 1997-09-12 | Burner head for liquid fuels |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2215673 CA2215673A1 (en) | 1997-09-12 | 1997-09-12 | Burner head for liquid fuels |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2215673A1 true CA2215673A1 (en) | 1999-03-12 |
Family
ID=4161478
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2215673 Abandoned CA2215673A1 (en) | 1997-09-12 | 1997-09-12 | Burner head for liquid fuels |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2215673A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009134530A2 (en) * | 2008-04-30 | 2009-11-05 | General Electric Company | Methods and systems for mixing reactor feed |
| CN114688529A (en) * | 2020-12-31 | 2022-07-01 | 大连理工大学 | Pre-film type gas-assisted atomizing nozzle with raised ridge structure |
-
1997
- 1997-09-12 CA CA 2215673 patent/CA2215673A1/en not_active Abandoned
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009134530A2 (en) * | 2008-04-30 | 2009-11-05 | General Electric Company | Methods and systems for mixing reactor feed |
| WO2009134530A3 (en) * | 2008-04-30 | 2010-01-28 | General Electric Company | Methods and systems for mixing reactor feed |
| US8434700B2 (en) | 2008-04-30 | 2013-05-07 | General Electric Company | Methods and systems for mixing reactor feed |
| RU2520440C2 (en) * | 2008-04-30 | 2014-06-27 | Дженерал Электрик Компани | Methods and device for raw material mixing in reactor |
| CN114688529A (en) * | 2020-12-31 | 2022-07-01 | 大连理工大学 | Pre-film type gas-assisted atomizing nozzle with raised ridge structure |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |