US3273621A

US3273621A - Burner assembly

Info

Publication number: US3273621A
Authority: US
Publication date: 1966-09-20
Anticipated expiration: 1983-09-20

Description

Sept. 20, 1966 H. T. CHILDREE BURNER ASSEMBLY Filed July 20, 19 64 {ml/ uid Fuel 0/- G45 a 66 VIIIIIJ HEP/44M 1 [Hap/FEE,

- INVENTOR.

United States Patent 3,273,621 BURNER ASSEMBLY Herman T. Childree, Cason, Tex., assignor to General Dynamics Corporation, Pomona, Calif., a corporation of Delaware Filed July 20, 1964, Ser. No. 383,564 Claims. (Cl. 158-7) This invention relates to burner assemblies, particularly to natural gas burners which operate in conjunction with pilot burner assemblies, and more particularly to natural gas burners whose operation depends on nozzle mixing principles and turbulence for producing a homogeneous mixture that will result in a high temperature, highly eflicient flame.

Heretofore, devices have been developed for the purpose of burning natural gas and air mixtures. Various configurations have been used in attempts to provide efficient burners. These prior known configurations range from those which are complicated to those which are simple. Information available indicates that some of these prior configurations have limited operational ranges. Some of the prior configurations used to provide a high heat release with excess air injection are massive and complicated. Various pilot arrangements have been used for primary ignition of the main gas burner which complicate the burner problems due to the unsatisfactory operation of the prior art pilots.

Several disadvantages are inherent in these prior art devices and deleterious effects result therefrom. Under certain applications, it would be advantageous to have a burner assembly which is capable of high volume, highly eflicient output and at the same time be compact and simple in construction and operation. The overall size of the high volume burner assemblies limits its usage to only certain applications. To satisfy these high volume, high range requirements, numerous smaller burners have been used. The more burners used to gain an end result, the more complicated the overall system becomes, thus adding to the inherent disadvantages.

This invention provides an improved burner assembly capable of high efliciency, high volume output with the feature of excess air injection and at the same time remaining relatively small and simple in construction and ease of operation. The compact feature of the invention enables it to be used for numerous requirements. The burner of the invention was developed for use with a high Mach pilot ignitor-burner which exhibits the necessary requirements to result in a fail safe, simple, effective, high efliciency system. Such a high Mach pilot ignitorburner may be of the type disclosed and claimed in applicants copending US. patent application Serial No. 383,602, filed July 20, 1964 and assigned to the same assignee. The material used in the construction of this burner assembly is dependent upon the type of service for which it is intended. The burner of this invention operates on nozzle mixing principles. These nozzles may or may not be supersonic. Supersonic conditions existing at either the gas orifices or air orifices or both will increase the possibility of a homogeneous mixture that will result in a highly eflicient flame, although further turbulence under subsonic conditions will gain the same result.

Therefore, an object of this invention is to provide an improved burner assembly.

A further object of the invention is to provide a natural gas burner which utilizes a pilot burner and has capabilities that exceed the prior known devices.

Another object of the invention is to provide a natural gas burner assembly whose operation depends on nozzle mixing principles and turbulence which produce a homogeneous mixture that -will result in a high eflicient flame.

Another object of the invention is to provide a burner assembly capable of high efliciency, high volume output which incorporates excess air injection while remaining relatively small and simple in construction and ease of operation.

Another object of the invention is to provide a burner assembly which will operate extremely cool and at the same time be compact, highly efficient, and contain a high operating range.

Another object of the invention is to provide a burner assembly which will continue to operate extremely cool although oxygen is injected into the combustion section to obtain a very high exit temperature.

Other objects of the invention will become readily apparent from the following description and accompanying drawings wherein:

FIG. 1 is a view showing in cross section an embodiment of the invention;

FIG. 2 is a cross-sectional view taken on the line 22 of FIG. 1; and

FIG. 3 is a partial cross-sectional view of another embodiment of the mixing chamber of the invention.

Referring to FIGS. 1 and 2, the burner assembly comprises generally a mixing and combustion section 11, a cooling section 12, a nozzle section 13, a pilot burner assembly 14.

Mixing and combustion section comprises an outer wall 15 having a back plate 16, an intermediate plate 17, and a front plate 18 attached therein in a predetermined spaced relationship; an inner wall 19 attached to plates 16, 17 and 18 defining a housing for the pilot assembly 14; and an internal wall section 20 attached to front plate 18 and defining a combustion chamber 21, wall section 20 having an end portion 20' defining an exhaust nozzle. A gas inlet 22 in outer wall 15 directs gas from a pressure source (not shown) to a gas manifold 23 defined by walls 15 and 19 and plates 16 and 17. An air inlet 24 in outer wall 15 directs air from a pressure source such as a blower (not shown) to an air manifold 25 defined by walls 15 and 19 and plates 17 and 18. A plurality of tubes or nozzles 26 (six being shown in this embodiment) are mounted in a spaced relationship around a circumference of intermediate plate 17 for discharging gas from manifold 23. A corresponding number of mixing tubes or nozzles 27 are mounted in a spaced relationship around a circumference of front plate 18 for discharging air from manifold 25. Nozzles 27 extend toward intermediate plate 17 and are of a larger diameter than gas nozzles 26 so that the gas nozzles extend into the air nozzles.

Nozzles

26 and 27 are constructed so that the gas nozzles 26 terminate at a position which is approximately /3 of the length of air nozzles 27. A semi-swirl or turbulator plate 28 is posi tioned in combustion chamber 21 and attached to wall section 20, plate 28 being located at a predetermined location with respect to pilot assembly 14.

Cooling section 12 comprises a shroud 29 having a flange 30 which is attached to a flange 31 of outer wall 15 by means such as bolts 32 and defining an annular passage or annulus 33 around wall 20 of combustion chamber 21. Front wall 18 is provided with a plurality of apertures 34 which permit the passage of air from manifold 25 into cooling annulus 33 for cooling combustion chamber wall 20.

Nozzle section 13 comprises a swaged member 35 having a flange 36 which is attached to a flange 37 of cooling shroud 29 by means such as bolts 38. Member 35 defines an extension of cooling shroud 29 and directs the cooling air from annulus 33 into the exhaust from nozzle 20'. The exhaust nozzle section 13 as illustrated has an area less than the area of the diameter of combustion chamber wall 20. This reduction of area increases the gas exhaust speed in order to assist, if necessary, in increasing the efficiency and producing a short stubby high velocity flame. However, the exit area may be the same diameter as the tailpipe or combustion wall 20, nozzle portion 20' and swaged member 35 being removed; or a diverging exit having a diameter greater than the diameter of the tailpipe may be utilized if desirable. Furthermore, the cooling shroud 29 may be removed and the cooling air apertures 34 in front wall 18 plugged, thereby providing a hotter exhaust issuing from the combustion chamber 21. However, this approach would require a high temperature insulation liner within the combustion chamber.

Gaskets or spacers 39 are positioned between

flanges

30 and 31 and between flanges 36 and 37 to provide air tight connections of the cooling shroud 29 and swaged member 35.

The pilot burner assembly 14 is of the type described and claimed in Applicants above mentioned copending patent application Serial No. 383,602 and comprises generally a housing 40 mounted in inner wall 19 and extending into combustion chamber 21; a casing 41 incorporating air and gas manifolds and tubes with air and

gas inlets

42 and 43, respectively, connected therewith; an ignitor/flame rod assembly 44 extending through a combustor grid 45 mounted in housing 40; and a bafile member 46 mounted on assembly 44. Air and

gas inlets

42 and 43 may be connected, if desired, to the same sources as those supplying air and gas to inlets 24 and 22. The basic operation of the burner assembly illustrated in FIGS. 1 and 2 is extremely simple. It is desirable to utilize as many points of air and gas mixing as practical, thus there can be any number of mixing tubes or nozzles 27 and corresponding gas nozzles 26 and need not be limited to six as shown. In operation, pilot burner assembly 14 is started thus providing a pilot flame in combustion chamber 21. Air is supplied from a pressure source (not shown) through appropriate valving and controls (not shown) to air manifold 25 through air inlet 24 and discharges through mixing tubes or nozzles 27 into combustion chamber 21. Gas is supplied from a pressure source (not shown) through appropriate controls and valves to gas manifold 23 through gas inlet 22 and is discharged through nozzles 26 into the turbulent air stream within mixing tubes 27 and continues down the tubes 27 and discharges with the air into the combustion chamber 21. At this point the mixture of air and gas comes in direct contact with the high temperature pilot flame generated by the pilot assembly 14. This mixture is easily ignited and combustion takes place primarily around the pilot barrel or housing 40. The semi-swirl or turbulator plate 28 creates further turbulence at high flows and holds the flame in this area by turbulence only. The combustion continues down the combustion section defined by wall 20 until it exhausts from the exit nozzle section 13.

As the heated gases from the combustion chamber 20 reach the exit nozzle section 13 two things occur. The heated gases increase in speed as the area is reduced by nozzle wall portion 20 and swaged member 35 which further and finally completes the combustion. It is at this point that the air from cooling annulus 33 is added to the flame. If proportioned correctly, the cooling air will add to the combustion process, but if not correctly proportioned it will cool the heated gases. If the nozzle section 13 is eliminated, the heated gases will not increase in speed as they issue from combustion chamber 21 but the cooling air will have a similar effect as in the exit nozzle section.

While not shown, the cooling air may be supplied to cooling annulus 33 through a separate inlet which would eliminate the apertures 34 in front wall 18, :but would add the requirement of a balancing valve mechanism in the cooling air supply line to balance the air supplied 4 through annulus 33 with the combustion products issuing from chamber 21.

Other types of cooling arrangements for the combustion wall 20 such as supplying air into the combustion chamber through slots or holes in wall 20 could be effectively utilized.

While not shown, swirl vanes may be attached to the front plate 18 of the FIG. 1 embodiment. These vanes would be positioned so that the air-gas mixture would be caused to rotate or swirl down the combustion section. This modification would eliminate need for the turbulator plate 28. The swirling action of such a modification would create the following conditions within the combustor section: (1) control the difference in pressure between the center of the combustor and its inner wall, (2) the center of the combustor would be at low pressure and low velocity flow, and (3) the combustor inner wall flow would be at high pressure and high velocity. Thus ignition would be easily accomplished in the low pressure area at the center of the combustor section. Additionally, oxygen may be injected at the center of the combustor section and produce an extremely high exit temperature without affecting the cool operation of the assembly.

As shown in FIG. 3, the mixing section of the burner assembly may be modified to provide cooling of the pilot burner assembly, and burning of various types of fuel, wherein the burner assembly is started on natural gas and air until the combustion air is hot and then the gas flow is reduced or shut off and another type of fuel is supplied, the air atomizing and/or vaporizing the fuel, and combustion continues. The valving and controls for the FIG. 3 embodiment do not constitute part of this invention and therefore have not been illustrated or described. The mixing section comprises a housing having an outer Wall 50, an inner wall 51, a back plate 52, a front plate 53 and a separator plate 54 defining air and gas manifolds 55 and 56. An air inlet 57 is connected to manifold 55 while a gas inlet 58 is connected to manifold 56 for supplying air and gas thereto from pressure sources (not shown). A tubular member 59 is mounted within inner wall 51 by a clamp means 60. A seal such as O-ring 61 is positioned around member 59. A housing or barrel 62 of a pilot burner of the type illustrated at 14 in FIG. 1 is positioned within tubular member 59, member 59 having an enlarged internal diameter portion defining a cavity 63 which extends around the down stream end of barrel 62. Inner wall 51 and tubular member 59 are provided with a plurality of

coaxial apertures

64 and 65, respectively which interconnect gas manifold 56 with cavity 63.

A fuel manifold 66 extends around outer wall 50 and is connected to a pressurized fuel source (not shown) through an inlet 67. A plurality of mixing tubes or nozzles 68 are mounted in front plate 53 and extend into air manifold 55 for discharging air therefrom. A corresponding number of tubes or nozzles 69 are mounted in outer wall 50 and extend into mixing tubes 68 for discharging fuel from manifold 66. Tubular member 59 is provided with a baflie plate 70 to increase the turbulence of the flow exhausting from tubes 68.

In operation of the FIG. 3 embodiment, air and gas are supplied from manifolds 55 and 56 for ignition by the pilot burner mounted in barrel 62. As soon as the combustion zone and combustion air is hot, the flow of gas from manifold 56 is reduced or shut off by appropriate valving (not shown) and fuel from manifold 66 is intermixed with the air flow via the mixing tubes 68 and bafile plate 70. Baflle plate 70 may be positioned on the interior end of barrel 62, if desired.

While not shown, combustion air may be directed around the combustor section in order that it may offer cooling to this section. This heat transfer from the combustor wallto the combustor air effects a temperature increase in the combustion air to assist in the vaporizing of the liquid fuel. Also the turbulator plate 70 may be adjustably positioned to enable the burner to be adjusted to supply a specific type of flame, either a short stubby or a luminous type flame.

It is apparent from the foregoing that this invention provides a mixing and combustor assembly that eliminates flash back and provides a high temperature burner by utilizing the multiple point mixing concept, especially when utilized in combination with the ignitor-burner assembly disclosed and claimed in applicants above mentioned copending application.

It has thus been shown that the burner assembly of the invention provides the following advantages over the prior art approaches: (1) it will not flash back; (2) it does not require any external mixing; (3) it is versatile and may be adapted to many applications due to its wide operating range; (4) it is lightweight; (5) it has high efficiency with high temperature flame; (6) it can burn multiple types of fuel; and (7) it has a comparatively cool assembly operating temperature with a high temperature flame output; and (8) it will operate with oxygen injection.

Although particular embodiments of the invention have been illustrated and described, modifications thereof will be readily apparent to those skilled in the art, and it is intended to cover in the appended claims all such modifications as come within the spirit and scope of the invention.

What I claim is:

1. A burner assembly comprising a mixing section, a combustion section, a nozzle section and a pilot :burner; said mixing section including a fuel manifold, an air manifold, a fuel inlet means operatively connected to said fuel manifold, an air inlet means operatively connected to said air manifold, nozzle means operatively attached to said fuel manifold, nozzle means operatively attached to said air manifold, said air nozzle means extending into said air manifold in a direction toward said fuel nozzle means while providing communication between said air manifold and said combustion section, said fuel nozzle means extending partially through said air nozzle means for discharging fuel thereinto; said combustion section including a combustion chamber operatively connected to said mixing section and said nozzle section, a turbulence creating means positioned in said combustion chamber, and cooling means operatively associated with said combustion chamber and said nozzle section; said pilot burner including means for supplying air and fuel thereto and an ignitor/flame rod assembly therefor.

2. The burner assembly defined in claim 1, wherein said pilot burner is operatively positioned in said mixing section having one end thereof in a spaced relationship to said turbulence creating means and the discharge end of said air nozzle means.

3. The burner assembly defined in claim 1, wherein said cooling means comprises an annular chamber extending around said combustion chamber.

4. The burner assembly defined in claim 3, wherein said annular chamber is supplied with cooling media from said air manifold via aperture means.

5. The burner assembly defined in claim 1, wherein said fuel nozzle means and said air nozzle means each comprises a plurality of separate nozzles, each of said fuel nozzles extending partially through the longitudinal length of an associated air nozzle.

6. A natural gas burner assembly comprising a mixing section, a combustion section, a nozzle section, and a pilot burner assembly section; said mixing section including a gas manifold, an air manifold intermediate said gas manifold and said combustion section, said gas and air manifolds extending around said pilot burner assembly section, a gas inlet means operatively connected to said gas manifold, an air inlet means operatively connected to said air manifold, a plurality of nozzle means operatively attached to said gas manifold for discharging gas therefrom, a plurality of nozzle means operatively attached to said air manifold for discharging air therefrom, said gas nozzle means extending internally of and partially through said air nozzle means; said air nozzle means being so configured as to extend into said air manifold in a direction toward said gas nozzle means while providing openings into said combustion section; said combustion section including a combustion chamber operatively connected to said mixing section, a turbulence creating means positioned in said combustion chamber, and a cooling manifold surrounding said combustion chamber, said cooling manifold being supplied with cooling media from said air manifold via aperture means therebetween; said nozzle section being operatively connected to said combustion section; said pilot burner assembly including a housing extending centrally into said combustion chamber adjacent said turbulence creating means and in spaced relationship with said gas nozzle means, a casing incorporating air and gas, delivery means, air and gas manifolds operatively connected to said casing means, a baflle means operatively positioned with respect to a combustor grid means and said casing, and an ignitor/flame rod assembly extending through said combustor grid means.

7. A burner assembly comprising a housing having a central passage, a separator member within said housing defining coaxial air and gas manifolds, said air manifold surrounding said gas manifold, an air inlet operatively connected to said air manifold, a gas inlet operatively connected to said gas manifold, said gas manifold being provided with a plurality of apertures opening into said housing central passage, a plurality of air nozzles operatively connected within said air manifold and opening into a combustion area defined by said housing, a fuel manifold, a plurality of fuel nozzles operatively connected to said fuel manifold and extending at least partially through said air nozzles, said central housing passage being adapted to retain an associated pilot burner and being so configured as to allow gas flowing from said apertures to pass around an associated pilot burner to cool the same.

8. A burner assembly comprising: a mixing section and a combustion section; said mixing section comprising an outer wall, an inner wall, a back plate member, an intermediate plate member, a front plate member, said plate members being attached to said outer and inner walls and in spaced relation to one another so as to define a gas manifold between said back and intermediate plate members and an air manifold between said intermediate and front plate members, said inner wall defining a housing for an associated pilot burner assembly, a gas inlet in said outer wall adapted to direct gas from an associated pressure source to said gas manifold, an air inlet in said outer wall adapted to direct air from an associated pressure source to said air manifold, a plurality of tube-like members mounted in spaced relationship in said intermediate plate member, and extending into said air manifold for discharging gas from said gas manifold, a corresponding number of mixing tubes mounted in spaced relationship in said front plate member and extending into said air manifold for discharging air from said gas manifold, said mixing tubes being of a larger diameter than said tubelike members, said tube-like members extending at least partially into said mixing tubes, said combustion section comprising a hollow member operatively connected to said front plate member and defining a combustion chamber in communication with said mixing tubes, said hollow member being provided with a reduced diameter end portion, an a turbulence creating means operatively connected within said hollow member and positioned adjacent said front plate member.

9. The burner assembly defined in claim 8, additionally including a cooling shroud member positioned in spaced relationship around said hollow member defining an annulus therebetween for cooling media, said cooling shroud member being operatively connected to said outer Wall of said mixing section, said front plate member of said mixing section being provided with at least one aperture providing communication between said air manifold and said cooling annulus.

10. The burner assembly defined in claim 9, additionally including a swaged member operatively connected to said cooling shroud member and defining an exhaust nozzle, said swaged member being so configured to correspond With said reduced diameter end portion of said hollow member thus providing an extension of said cooling annulus.

References Cited by the Examiner UNITED STATES PATENTS Keith 158109 Bergholdt.

Goddard 1584 X Allen 1584 X Williams.

Taricco 15828 Robb 158109 JAMES W. WESTHAVER, Primary Examiner.

Claims

1. A BURNER ASSEMBLY COMPRISING A MIXING SECTION, A COMBUSTION SECTION, A NOZZLE SECTION AND A PILOT BURNER; SAID MIXING SECTION INCLUDING A FUEL MANIFOLD, AN AIR MANIFOLD, FUEL INLET MEANS OPERATIVELY CONNECTED TO SAID FUEL MANIFOLD, AN AIR INLET MEANS OPERATIVELY CONNECTED TO SAID AIR MANIFOLD, NOZZLE MEANS OPERATIVELY ATTACHED TO SAID FUEL MANIFOLD, NOZZLE MEANS OPERATIVELY ATTACHED TO SAID AIR MANIFOLD, SAID AIR NOZZLE MEANS EXTENDING INTO SAID AIR MANIFOLD IN A DIRECTION TOWARD SAID FUEL NOZZLE MEANS WHILE PROVIDING COMMUNICATION BETWEEN SAID AIR MANIFOLD AND SAID COMBUSTION SECTION,SAID FUEL NOZZLE MEANS EXTENDING PARTIALLY THROUGH SAID AIR NOZZLE MEANS FOR DISCHARING FUEL THEREINTO; SAID COMBUSTION SECTION INCLUDING A COMBUSTION CHAMBER OPERA-