US3342242A

US3342242A - Gas and oil burner

Info

Publication number: US3342242A
Application number: US563455A
Authority: US
Inventors: Verloop Hendrik Nicolaas
Original assignee: INGENIEURSBUREAU RODENHUIS EN VERLOOP NV
Current assignee: INGENIEURSBUREAU RODENHUIS EN VERLOOP NV
Priority date: 1965-07-12
Filing date: 1966-07-07
Publication date: 1967-09-19
Anticipated expiration: 1984-09-19
Also published as: GB1080528A; NL6508929A; NL145654B

Description

Sept. 19-, 1967 H.- N. VERLOOP 3,342,242

GASAND OIL BURNER Filed Ju1y 7, 1966 2 Sheets-Sheet 1 Sept. 19, 71967 H. N. VERLOOP 3,342,242

GAS AND OIL BURNER Filed July 7, 1966 2 Sheets-Sheet United States Patent 3,342,242 GAS AND OIL BURNER Hendrik Nicolaas Verloop, Amsterdam, Netherlands, as-

signor to Ingenieursbureau Rodenhuis en Verloop N.V., Amsterdam, Netherlands Filed July 7, 1966, Ser. No. 563,455 Claims priority, application Netherlands, July 12, 1965, 658,929 15 Claims. (Cl. 158-11) The invention relates to a gas burner and more especially to a gas burner for the furnace of a steam boiler or the like.

The conventional industrial gas burners in most cases comprise a circular row of gas discharge nozzles directed radially inwardly or radially outwardly and opening directly in a flow of combustion air led past these nozzles. This arrangement has the disadvantage that immediately in front of the nozzles the outflowing gas is unsufliciently mixed with the combustion air, whereby, especially in the case of a burning gas of a kind having a relatively low rate of combustion, the flame is apt to be blown off, if for one reason or another the flow of combustion air becomes too strong. As a result, the known gas burners of this type can only be regulated within a relatively small range, since outside this range a stable flame is not ensured.

The invention has for its object to provide an industrial gas burner which obviates the disadvantages of the known burners and has a wide regulating range. More especially, the invention has for its object to provide such a gas burner which is suitable for burning different kinds of gas, i.e. gas types of varying combustion rates, and more particularly is suitable for burning natural gas.

Another object of the invention is to provide a gas gas burner which has a large maximum output and yet relatively small dimensions.

Another object of the invention is to provide a gas burner of the kind described which is adapted to be combined with a conventional oil burner to a compact unit requiring only a relatively small opening in the wall of the boiler, for which the unit is intended, whereby, at choice, the boiler may be fired either by oil or by gas.

The gas burner according to the invention comprises a substantially cylindrical shell having at its forward end a forwardly diverging cone-shaped part. An air guiding sleeve is arranged concentrically about and radially spaced from the shell to the rear of the shell cone part which sleeve at its rear end encloses with the outer wall of the shell an annular air inlet opening and has at its forward end a conical forwardly diverging portion enclosing with the rear side of the shell cone part a mixing chamber with an annular forwardly and radially outwardly directed outlet opening. To the rear of the shell cone part gas discharge means are provided arranged circumferentially in the shell for admitting burning gas into the mixing chamber which gas discharge means are adapted to discharge a substantially annular gas flow diverging forwardly in the direction of the annular outlet opening. By arranging the gas burner in a stream of combustion air flowing axially forwardly of the gas burner circumferentially about the shell and sleeve thereof, part of this air flow enters the air inlet opening and is guided by the sleeve towards the mixing chamber and past the gas discharge means in this 3,342,242 Patented Sept. 19, 1967 chamber, the resulting gas-air mixture flowing outwardly to be burned at the said outlet opening in the main flow of combustion air.

The air guiding sleeve thus takes off a certain percentage of mixing air from the total amount of combustion air flowing past the burner which percentage, depending on the circumstances and the desired shape of the flame, may vary between 5% and 20% and preferably amounts to approximately 10%. In the annular mixing chamber this mixing air is thoroughly mixed with the outflowing gas, whereby the rate of combustion of the gas-air mixture leaving the outlet opening of the mixing chamber is considerably greater than the combustion rate at the mouth of the gas discharge means would be with out the presence of the air guiding sleeve. This gas-air mixture burns at the outlet opening of the mixing chamber with an annular flame which practically cannot be blown ofl" by the main flow of combustion air flowing past this outlet opening. Thereby it is possible to obtain a wide regulating range. Tests have shown that it is, for instance, possible to decrease the gas supply down to a twelfth of the maximum capacity, for which the burner has been laid out, while maintaining a stable flame throughout this range. By a proper choice of the taper of the shell cone part and of the form and width of the air guiding sleeve with respect to the shell, i.e. of the relative amount of mixing air taken off from the main combustion air flow, it is possible for the shape of the flame to be varied within wide limits and to be adapted to the shape and dimensions of the furnace to be fired. It is thus possible to obtain a long narrow flame as well as a short wide flame.

Preferably, the air guiding sleeve is not only detachably mounted on the burner shell, but also axially adjustable with respect to the shell which allows the shape of the flame to be regulated.

According to a preferred embodiment of the invention, the shell has a double wall, the gas being supplied at the rear end of the shell to the annular space enclosed between the two shell walls. In case of a burner for average or high gas pressure, an annular series of gas discharge nozzles may be arranged circumferentially in the outer wall of the double-walled shell directly to the rear of the shell cone part which nozzles communicate with the annular space'between the shell walls and have axes substantially parallel to respective generating lines of the shell cone part.

In the case of a burner for low gas pressure the outer wall of the double-walled shell may terminate at some distance to the rear of the shell cone part forming an extension of the inner shell wall, the outer shell wall likewise terminating in a conically diverging portion enclosing with the shell cone part a continuous annular gas discharge opening.

According to a further preferred embodiment, the cylindrical shell comprises an air supply channel for aux-iliary air which channel runs centrally and axially through the shell terminating at the base of the shell cone part and comprising means for imparting a whirling motion to the air flowing through the channel; at the rear edge of the shell cone part is arranged an annular row of auxiliary gas outlet openings opening into the space enclosed by this cone part and directed forwardly and inwardly at an angle to the axis of the burner which auxiliary gas outlet openings have a smaller cross-section than the first mentioned main gas discharge openings. In this way inside the shell cone part a constant auxiliary flame is formed which burns independently of the burner load and supports the combustion process of the burner, whereby the regulating range thereof is further increased. This embodiment is especially adapted for combining the gas burner of the invention with an oil burner. To that eifect the oil burner may be arranged within the cylindrical shell with its mouth situated inside the shell cone part. When the oil burner is not functioning and the supply thereto is shut off, the conventional means of the oil burner for supplying the primary air to this burner may be used for supplying the auxiliary air for the above-mentioned supporting flame of the gas burner. A gas burner and oil burner combined in this way form a very compact unit which is but little larger than the oil burner alone and which in most cases can be mounted in an exist-ing burner opening in the wall of a conventional oil-fired boiler furnace. The oil burner can be of any suitable known type and construction and preferably comprises a rotating oil atomizing cup and a suitable regulating means for the primary air of the oil burner.

The novel arrangement according to the present invention and the advantages of this arrangement will appear more fully from the following description and claims in conjunction with the drawings which illustrate by the way of example two embodiments of the invention.

FIGURE 1 shows partly a side elevation and partly an axial section of a gas burner according to the invention intended for a gas pressure of average rate; and

FIGURE 2 shows in a similar way a side elevation and an axial section of a second embodiment of the gas burner intended for low gas pressure,

Referring to FIGURE 1, a gas burner is shown having a double-walled cylindrical shell 1 with an outer wall 2 and an inner wall 3 which two cylindrical walls have a common axis and together enclose an annular space 4. The outer wall 2 is provided at its rear end with an opening 5 of circular cross-section facing radially outwardly and forming a gas inlet opening which by means of a pine bend 6 is connected to a rewardly extending gas inlet pipe 7 connected to a source of gas supply (not shown). At their forward ends the two shell walls 2 and 3 converge inwardly, meeting in an annular forward rim portion 8 comprising a circumferential row of narrow gas outlet bores 9.

The shell 1 has at its forward end a forwardly diverging cone-shaped part 10, fittingly arranged with its rear edge in a groove 11 of rectangular cross-section cut out in the rim portion 8 of the shell and fixedly secured to the shell by means of bolts or the like (not shown). The cone part is provided with an annular row of equally spaced holes 12.

Close to the rear of the cone part 10 the outer shell wall 2 has a circumferentially row of equally spaced threaded bores 13, in which a number of exchangeable gas discharge nozzles have been screwed. The axes of these nozzles 14 intersect the main axis of the cylindrical burner shell and are in parallel to the respective generating lines of the shell cone part 10.

An air guiding sleeve 15 is arranged concentrically about the burner shell 1 to the rear of the cone part 10 and radially spaced from the outer shell wall 2. The sleeve 15 is fixedly but exchangeably mounted with its rear end on the shell Wall 2 by means of four bosses 16 formed on this shell wall and corresponding bossed formed on the inside of the sleeve 15, bolts 17 passing through the sleeve and engaging in screw holes in the bosses 16. Apart from this attachment the sleeve 15 lies free of the shell wall 2 and encloses between its rounded or bevelled rear edge 18 and this shell wall 2 an annular air inlet opening 19. In its rear portion the sleeve 15 substantially follows the profile of the shell wall 2, but at its forward portion the sleeve 15 is formed into a conically diverging portion 20, of which the taper corresponds to the taper of the shell cone part 10 and of which the forward edge lies axially to the rear of the edge of the cone part 10. The sleeve 15 and the cone part 10 enclose an annular mixing chamber 21 terminating in an annular outlet opening 22 facing in an inclined forward and radially outward direction. The axes of the gas discharge nozzles 14 extend substantially midway between the cone part 10 and the sleeve portion 20. The bores of the gas discharge nozzles 14 are considerably wider than the bores 9 in the rim portion of te shell, both bores communicating with the annular space 4 between the two shell walls 2 and 3.

The inner wall 3 of the shell has at its rear side a portion 23 of larger inner diameter which fits over the forward end of a rearwardly extending pipe 24. The rear edge of the shell walls 2 and 3 are fixedly connected to one another by means of a flanged ring member 25 welded to the walls 2 and 3 and having threaded holes for set screws 26 for detachably securing the shell 1 onto the pipe 24.

An oil burner 27 of conventional design is mounted inside the shell 1, lying coaxially within the shell inner wall 3 and the forward end of the pipe 24. As appears from FIGURE 1, the form of the inner wall 3 is somewhat adapted to the exterior shape of the oil burner, The oil burner 27 has been pushed into the shell 1 from the rear side thereof until a bevelled shoulder 28 formed on the burner engages a corresponding annular bevelled shoulder on the inside of the shell wall 3. In this position the mouth 29 of the oil burner 27 lies inside the cone part 10 at a small distance forwardly of the rear edge of this cone part. The oil burner 27 is connected at its rear side to an oil supply pipe 30. The oil burner prferably is of the type having a rotating atomizing cup and the usual air regulating means for imparting a whirling motion to the primary air serving for the atomizing of the oil and leaving the burner through the burner mouth 29. This primary air is supplied through the pipe 24 which is connected to an air source of constant pressure (not shown). Oil burners of this rotary type are well-known in the art, wherefor further details of the oil burner 27 are not shown in the drawings.

The combined gasand air burner 1, 27 is mounted centrally in a throat-like opening 31 in the wall 32 of a boiler having a boiler shell 33 as shown more or less schematically in FIGURE 1. The opening 31 opens into the furnace of the boiler which is in itself not shown and may be of any known type and construction. A blast box 34 for the secondary air for the burner unit is arranged in front of and spaced from the opening 31 which blast box supplies the secondary air by natural draught or by means of a suitable blower (not shown). The blast box has an outer shell 35 with an opening 37 for the passage of the burner unit which opening is closed off by a closure plate 36 secured to this unit. The blast box structure is not shown in detail and may be of any known design.

The operation of the gas burner 1 will now be described. In operation, the secondary combustion air supplied by the blast box 34 flows around the shell 1 and axially along this shell and through the opening 31 into the furnace, to which this opening leads. Part of the air flowing along the shell wall 2 passes through the air inlet opening 19 of the air guiding sleeve 15 and is guided towards the mixing chamber 21. In this mixing chamber this air is thoroughly mixed with the gas flowing from the gas discharge nozzles 14. The so formed gas-air mixture flows outward through the outlet opening 22, the mixture burning at this opening with an annular flame. The main stream of the secondary combustion air flows across this outlet opening 22, the air-gas mixture leaving this opening 22 in a forwardly and radially outwardly directed flow, of which the main direction is inclined with respect to the substantially axial direction of the main air flow. As a result a very thorough mixing of the outflowing air-gas mixture and the main flow of secondary combustion air occurs. Because of the premixing of the air flowing through the sleeve 15 with the gas from the nozzles 14 in the mixing chamber 21, the rate of combustion of the gas mixture leaving the outlet opening 22- is increased, whereby the flame at this opening is very stable and cannot be blown off by a small disturbance in the flame front. As a result the outflow velocity of the gas from the nozzles 14 can be substantially greater than would be possible without the presence of the air guiding sleeve 15. This means that the gas burner has a high full load capacity which capacity can, furthermore, be regulated within a wide regulating range by decreasing the gas pressure and a corresponding regulation of the secondary air. The maximum capacity can be varied by exchanging the gas discharge nozzles 14 for nozzles having a smaller or wider bore. The shape of the flame depends on the form of the shell cone part 10 and of the air guiding sleeve 15 and especially on the amount of mixing air flowing through this sleeve. This sleeve 15 can be exchanged by a sleeve of different shape and width, and, if necessary, the likewise exchangeable cone part It) can be adapted to the chosen sleeve form. By a proper choice of the sleeve and cone part it is possible to adapt the shape of the flame to the dimensions of the furnace. The amount of mixing air flowing through the sleeve 15 may vary between approximately and 20% of the total amount of supplied secondary combustion air, the flame obtaining a longer shape, when said percentage is increased. The upper limit of the percentage of mixing air is determined by the explosion limit of the gas mixture in the mixing chamber 21 which limit may, of course, not be passed. In the shown embodiment the percentage of mixing air is approximately of the total amount of secondary combustion air, in which case the flame has a relatively broad shape.

Through the narrow gas outlettopenings 9 in the forward rim portion of the shell 1 gas also flows at an angle with the axis of the burner into the space within the cone part 10 which gas is thoroughly mixed with the primary air leaving the mouth 29 of the oil burner 27 with a strong whirling motion, the oil supply to the oil burner 27, of course, being shut off. The amount of this primary air which is supplied, for instance, by a separate blower (not shown) is constant and comprises, for instance, approximately 7% of the total maximum amount of combustion air. Through the narrow openings 11 flows also approximately 7% of the gas to be burned. As a result a constant stable and fan-shaped flame occurs at the cylindrical mouth or outlet opening 29 of the oil burner 27 which can be easily ignited by an auxiliary flame of an ignition device of any known type (not shown) and which supports the total combustion process and also further increases the regulating range of the main flame.

When the gas burner is shut off in order to fire the furnace by means of the oil-burner 27, this oil burner operates in the conventional way, in which the primary air fed through the pipe 24 serves for atomizing the oil particles flung outwardly from the edge of the rotating cup of the burner and transports these oil particles as a whirling conical flow of mist into the secondary combustion air flowing past the edge of the cone part 10, where the combustion occurs. Through the holes 12 in the cone part 10 further air can enter the space within the cone part. This operation of the oil burner 27 is well-known in the art and need not be described in detail. It is also possible to burn gas and oil simultaneously in the two combined burners 1 and 27 of the unit.

9 FIGURE 2 shows an embodiment of the gas burner of the invention for low gas pressures. As in the embodiment of FIGURE 1, the shell 41 of the burner has a double wall. However, in this case the outer wall 42 and the inner wall 43 of the shell are not secured to each other at their rear ends, but are welded to the forward ends of two

concentric pipes

45 and 46 which enclose an annular channel 47 communicating with the annular space C5 44 between the two shell walls and connected at its rear ends to a gas supply conduit (not shown). Through the inner pipe 46 primary combustion air can be supplied for the oil burner 27 mounted inside the inner shell wall 43 and the pipe 46 in a similar way as in the embodiment of FIGURE 1.

The inner shell wall 43 has at its forward end an integral cone-shaped portion 48 corresponding to the cone part 10 of FIGURE 1, said cone portion 48 having at its base an annular row of equally spaced gas outlet holes 49 provided in the shell wall 43. The outer shell wall 42 in longitudinal section follows substantially the sectional form of the inner shell wall and likewise terminates in a cone-shaped portion 50. The forward edge of this cone portion 50, as seen in the axial direction, lies to the rear of the forward edge of the cone portion 48 and encloses therewith an annular gas discharge opening 51 directed forwardly and radially outwardly. The shell walls 42 and 43 are connected to each other in spaced coaxial relationship by means of a number of ribs 52.

An air guiding sleeve 53 is arranged about the forward end of the double-walled shell 41 and is carried by a number of hook-shaped rods 54 attached thereto which rods have their rearwardly extending ends inserted in clamping sleeves 53 welded to the shell wall 42 and provided with set screws 56 for detachably securing the rods 54 and thereby the sleeve 53 to the shell 41. The sleeve 53 is thus exchangeable and adjustable in the axial direction with respect to the shell. The sleeve 53 has at its rear end a conically diverging portion 57 forming with the shell wall 42 an annular inlet opening 19 for the mixing air, and has at its forward end a conically diverging portion 58, of which the taper corresponds to the taper of the cone portion 4%. The sleeve cone portion 53 and the shell cone portion 48 thus form together the outlet opening 22 in front of the gas discharge opening 51.

In this embodiment the forward edge of the sleeve 53 is situated radially outward and only slightly rearward of the forward edge of the shell cone portion 48.

In a similar way as described for the embodiment of FIGURE 1, the combined gas burner and oil burner unit is mounted in the opening 31 of a furnace wall 32, the secondary combustion air being again supplied by a blast box (not shown) such as the blast box 34 of FIGURE 1.

The burner of FIGURE 2 operates similarly to the burner of FIGURE 1, however, with this difference that the gas of low pressure supplied through the

channel

47, 44 is discharged through a continuous, relatively wide annular discharge opening 51 into the mixing chamber 21 enclosed by the sleeve 53. Approximately 7% of the gas supplied flows at an angle inwardly through the holes 59 into the space within the cone portion 48 to be mixed with the whirling air flow leaving the mouth 29 of the oil burner 27. Part of the secondary combustion air, supplied, for instance, by a blower and flowing axially along the shell 41, enters the air inlet opening 19 of the sleeve 53, flowing through this sleeve to the mixing chamber 21 and, after being mixed with the gas of low pressure flowing from the discharge opening 51, leaves the sleeve through the outlet opening 22.

Also in this embodiment the gas burner has a wide regulating range and has a stable flame, the shape of which may be varied by a proper choice of the form and the relative axial position of the sleeve 53. Withinthe cone portion 48 burns an auxiliary or supporting flame as was thecase in the embodiment of the burner of FIGURE 1.

It is to be noted that in the gas burner according to the invention the mixing air is not drawn into the air guiding sleeve by injection under the action of the gas flowing from the gas discharge opening or nozzles, but forms part of the total flow of secondary combustion air drawn into the furnace by the pressure drop across the opening 31 in the furnace wall 32.

A While the invention has been illustrated and described with reference to specific embodiments thereof, it will be understood that other embodiments may be resorted to within the scope of the following claims.

I claim:

1. A gas burner for discharging burning gas into a flow of combustion air for said gas, comprising a substantially cylindrical shell having at its forward end a forwardly diverging cone-shaped part; an air guiding sleeve member arranged concentrically about and radially spaced from said shell to the rear of said shell cone part, said sleeve at its rear end enclosing with the wall of said shell an annular air inlet opening and said sleeve having at its forward end a conical forwardly diverging portion enclosing with the rear side of said shell cone part a mixing chamber with an annular forwardly and radially outwardly directed outlet opening; gas conduit means; and gas discharge means connected to said conduit means and arranged circumferentially in said shell to the rear of said shell cone part for admitting burning gas into said mixing chamber, said gas discharge means being adapted to discharge a substantially annular gas flow diverging forwardly in the direction of said annular outlet opening; whereby when said combustion air is caused to flow axially forwardly of the burner and circumferentially about said shell and sleeve thereof, part of said air flow enters said air inlet opening to be guided by said sleeve towards said mixing chamber and past said gas discharge means in said chamber, the resulting gasair mixture flowing outwardly to be burned at said outlet opening.

2. The gas burner of claim 1 wherein said air guiding sleeve is axially adjustable with respect to said shell so as to allow the shape of the flame of the burner to be regulated.

3. The gas burner of claim 1 wherein said air guiding sleeve is detachably mounted on said shell.

4. The gas burner of claim 1 wherein said shell is doublewalled, said gas conduit means comprising the annular space enclosed between the two shell walls.

5. The gas burner of claim 4 adapted for gas of at least moderate pressure, wherein said two shell walls meet at their forward ends to close off said annular space at this end and wherein said gas inlet means comprise an annular series of gas discharge nozzles arranged circumferentially in the outer wall of said double-walled shell to the rear of said shell cone part, said nozzles communicating with said annular space between said shell walls and having axes substantially parallel to respective generating lines of said shell cone part.

6. The gas burner of claim 5 wherein said conical forward end of said air guiding sleeve lies substantially axially to the rear of the forward edge of said shell cone part.

7. The gas burner of claim 4 adapted for gas of low pressure, wherein said shell cone part forms an extension of the inner wall of said double-walled shell and wherein the outer wall of said shell terminates at its forward end in a conically diverging end portion situated to the rear of and spaced from said inner shell cone part and enclosing an annular opening with the latter which communicates with said annular space and constitutes said gas discharge means.

8. The gas burner of claim 7, wherein said conical portion of said air guiding sleeve is situated substantially radially outwardly of said shell cone part.

9. The gas burner of claim 1 further comprising air conduit means for auxiliary air arranged coaxially with and inside said shell and opening centrally into said shell cone part, said shell having an annular series of gas outlet openings substantially at the base of said shell cone part communicating with said gas conduit means and opening inside said cone part, said gas outlet openings being directed radially inwardly and forwardly at an angle with the axis of the shell and providing a smaller total passage for the gas than said gas discharge means.

10. The gas burner according to claim 1 further comprising an oil burner arranged inside said shell coaxially with the latter and with its mouth opening in said shell cone part, said oil burner, when not operating, forming said air conduit means for supplying auxiliary air to said shell cone part.

11. A gas burning installation including a gas burner of substantially cylindrical form and having a forward end and means for directing a flow of combustion air axially forwardly of and circumferentially about said burner, said gas burner comprising a substantially cylindrical shell having at its forward end a forwardly diverging cone-shaped part; an air guiding sleeve member arranged concentrically about and radially spaced from said shell to the rear of said shell cone part, said sleeve at its rear end enclosing with the wall of said shell an annular air inlet opening and said sleeve having at its forward end a conical forwardly diverging portion enclosing with the rear side of said shell cone part a mixing chamber with an annular forwardly and radially outwardly directed outlet opening; gas conduit means; and gas discharge means connected to said conduit means and arranged circumferentially in said shell to the rear of said shell cone part for admitting burning gas into said mixing chamber, said gas discharge means-being adapted to discharge a substantially annular gas flow diverging forwardly in the direction of said annular outlet opening; whereby part of said flow of combustion air may enter said air inlet opening to be guided by said sleeve towards said mixing chamber and past said gas discharge means in said chamber, the resulting gas-air mixture flowing outwardly to be burned at said outlet opening.

12. The installation of claim 11, wherein said air guiding sleeve is so dimensioned and arranged that the amount of mixing air flowing through said sleeve is between 5% and 20%, and preferably approximately 10%, of the total amount of combustion air flowing about said burner.

13. The combination of a gas burner and an oil burner in which said gas burner comprises a substantially cylindrical shell having at its forward end a forwardly diverging cone-shaped part; an air guiding sleeve member arranged concentrically about and radially spaced from said shell to the rear of said shell cone part, said sleeve at its rear end enclosing with the wall of said shell an annular air inlet opening and said sleeve having at its forward end a conical forwardly diverging portion enclosing with the rear side of said shell cone part a mixing chamber with an annular forwardly and radially outwardly directed outlet opening; gas conduit means; and gas discharge means connected to said conduit means and arranged circumferentially in said shell to the rear of said shell cone part for admitting burning gas into said mixing chamber, said gas discharge means being adapted to discharge a substantially annular gas flow diverging forwardly in the direction of said annular outlet opening; whereby on causing combustion air to flow axially forwardly of and circumferentially about said shell and sleeve, part of said combustion air flow enters said air inlet opening to be guided by said sleeve towards said mixing chamber and past said gas discharge means in said chamber, the gasair mixture thus formed in said mixing chamber on operation of the gas burner flowing outwardly .to be burned at said outlet opening in the remaining part of said combustion air flow; said oil burner having a mouth at its forward end and being arranged inside said shell co-axially with the latter and with said mouth opening into said shell cone part.

14. The combination of claim 13, wherein said shell comprises two substantially concentric radially spaced walls enclosing an annular space, said gas conduit means comprising said annular space, and said gas burner being mounted inside the inner one of said two shell walls with a close fit.

15. The combination of claim 13 in which said oil 9 burner, when not operating, constitutes an air conduit means for auxiliary air for said gas burner opening centrally into said shell cone part, said shell having an annular series of gas outlet openings substantially at the base of said shell cone part communicating With said gas conduit means and opening inside said cone part, said gas outlet openings being directed radially inwardly and forwardly at an angle with the axis of the shell and providing a smaller total passage for the gas than said gas discharge means, whereby on operation of the gas burner an auxiliary flame burns in said shell cone part supporting the combustion of the gas-air mixture at said sleeve outlet opening.

References Cited UNITED STATES PATENTS 1,561,848 11/1925 Green 158109 X 1,991,894 2/1935 Porney 15811 2,526,748 10/1950 Hill 158l10 X 2,840,152 6/1958 Reed 158-11 X 0 FREDERICK L. M'ATTESON, JR., Primary Examiner.

E. G. FAVORS, Assistant Examiner.

Claims

1. A GAS BURNER FOR DISCHARGING BURNING GAS INTO A FLOW OF COMBUSTION AIR FOR SAID GAS, COMPRISING A SUBSTANTIALLY CYLINDRICAL SHELL HAVING AT ITS FORWARD END A FORWARDLY DIVERGING CONE-SHAPED PART; AN AIR GUIDING SLEEVE MEMBER ARRANGED CONCENTRICALLY ABOUT AND RADIALLY SPACED FROM SAID SHELL TO THE REAR OF SAID SHELL CONE PART, SAID SLEEVE AT ITS REAR END ENCLOSING WITH THE WALL OF SAID SHELL AN ANNULAR AIR INLET OPENING SAND SAID SLEEVE HAVING AT ITS FORWARD END A CONICAL FORWARDLY DIVERGING PORTION ENCLOSING WITH THE REAR SIDE OF SAID SHELL CONE PART A MIXING CHAMBER WITH AN ANNULAR FORWARDLY AND RADIALLY OUTWARDLY DIRECTED OUTLET OPENING; GAS CONDUIT MEANS; AND GAS DISCHARGE MEANS CONNECTED TO SAID CONDUIT MEANS AND ARRANGED CIRCUMFERENTIALLY IN SAID SHELL TO THE REAR OF SAID SHELL CONE PART FOR ADMITTING BURNING GAS INTO SAID MIXING CHAMBER, SAID GAS DISCHARGE MEANS BEING ADAPTED TO DISCHARGE A SUBSTANTIALLY ANNULAR GAS FLOW DIVERGING FORWARDLY IN THE DIRECTION OF SAID ANNULAR OUTLET OPENING; WHEREBY WHEN SAID COMBUSTION AIR IS CAUSED TO FLOW AXIALLY FORWARDLY OF THE BURNER AND CIRCUMFERENTIALLY ABOUT SAID SHELL AND SLEEVE THEREOF, PART OF SAID AIR FLOW ENTERS SAID AIR INLET OPENING TO BE GUIDED BY SAID SLEEVE TOWARDS SAID MIXING CHAMBER AND PAST SAID GAS DISCHARGE MEANS IN SAID CHAMBER, THE RESULTING GASAIR MIXTURE FLOWING OUTWARDLY TO BE BURNED AT SAID OUTLET OPENING.