US3514244A - Aspirator burner - Google Patents

Description

May 26, 1970 D, MEYER ETAL 3,514,244

ASPIRATOR BURNER Filed May 27, 1968 2 Sheets-Sheet l fnUerZZns: Baz/zd Weyer,

Sidney reenbery 59m f77. may

May 26, 1970 D. MEYER ETAL 3,514,244

ASPIRATOR BURNER 2 Sheets-Sheet 2 Filed May 27, 1968 Egg 57 l Dac/zd Weyer',

Sidney Greenberg United States Patent O 3,514,244 ASPIRATOR BURNER David Meyer, Kankakee, and Sidney Greenberg, Monee, Ill., assignors to Radiant International Incorporated, a corporation of Illinois Filed May 27, 1968, Ser. No. 732,268 Int. Cl. F23d 11/44 U.S. Cl. 431-164 13 Claims ABSTRACT F THE DISCLOSURE An aspirator burner having a pressurized primary air supply for increased burner temperature and improved fuel efliciency. The aspirator burner also includes means for equalizing the air flow in the secondary supply and means facilitating retention of the refractory lining within the burner shell.

This invention relates in general to fluid fuel burners, and in particular to aspirator burners having improved fuel efficiency. More particularly, this invention relates to means for improving the combustion efficiency and burner temperature of fluid fuel burners capable of utilizing a variety of fluid fuels and a primary source of pressurized air. This invention also pertains to more effective means for retaining a heat protective refractory lining within a burner shell, and for equalizing the air flow in the burners secondary air supply.

In typical aspirator burners, a source of hydrocarbonous fuel is thoroughly mixed with a primary source of pressurized air in a refractory lined combustion chamber. The mixture is ignited inside the combustion chamber and burns with substantial efficiency, releasing large quantities of thermal energy and producing a high temperature. The burning process is believed to comprise a rapid series of small explosions which result in a rapidly expanding gas. The expanding gas expels the thermal energy which exits the combustion chamber from the front of the burner, thereby heating a furnace or other apparatus into which the iburner may be fired.

Fluid fuels for the aspirator burner described above may comprise such common fuels as low-grade, viscous fuel oil, including #5, #6, Bunker C and refuse oil. These viscous oils are generally heated to about 200 F. for improved flow through the fuel supply pipes and are delivered to the burners at this temperature. Another common fuel is natural or manufactured gas. In addition, less common fuels such as pulverized coal and sawdust, in air vehicles, have also been successfully utilized.

As is well known, the efficiency of aspirator burners may be improved by supplying the combustion chamber with additional quantities of air, over and above that supplied by the primary source, to insure absolute and complete combustion of the fuel. A common arrangement for supplying this additional air, which may be called secondary air, is through a series of ports extending through the combustion chamber walls, substantially adjacent the mixing area of the fuel and primary air. The ports are typically freely exposed to the unheated ambient air, which is drawn therethrough into the combustion chamber due to the subatmospheric pressure therein. This secondary air is then admixed with the fuel and primary air to provide additional combustive support.

Unheated secondary air is undesirable for several reasons, including: (l) when low-grade, heated fuel oil is used, the lower temperature ambient air mixing with the atomized fuel oil tends to coagulate and de-atomize the oil which seriously impedes proper mixing and' proper combustion; (2) the admittance of unheated ambient air into the combustion chamber as wasteful since this unheated air must be heated within the chamber to a sutilcient combustion supporting temperature which reduces the expansion force of the gaseous combustion products, resulting in wasteful and inefficient operation; and (3) the admittance of unheated secondary air into the combustion chamber limits the maximum temperature which can be attained with an aspirator burner and limits the versatility and ultimate value of such burners.

Prior art aspirator burner construction also generally utilizes an undesirable and time-consuming structural arrangement -for securing the protective refractory lining in the front flange. Refractory hangers were typically secured about the inside of the flange and the refractory material was rammed behind the hangers. In addition to the labor required to install the refractory hangers in the flange, it was difficult to ram the refractory material firmly behind the hangers, thereby resulting in refractory voids in the flange member.

In addition, prior art aspirator burners displayedl unequal secondary air flow through the ports to the combustion chamber resulting in an uneven combustion flame and hot spots in the combustion chamber.

This invention obviates the above and other associated problems 1by providing means for heating the secondary air source prior to its introduction into the combustion chamber. The heated secondary air eliminates coagulation of atomized, low-grade fuel oil, and its deleterious effects on combustion efficiency. In addition, heating the secondary air prior to its introduction into the combustion chamber eliminates the heat drain in the combustion chamber proper previously required to elevate the secondary air to proper combustion supporting temperature. The invention also provides means for controlling the temperature of the secondary air introduced into the combustion chamber, which serves as an effective high level temperature control for readily controlling the maximum burner temperature for vvarious fuel flow rates. The actual temperature of the secondary air is controlled by combining regulatable quantities of heated air with unheated ambient air in a secondary air duct, and directing the combined airs into the combustion chamber.

The invention also provides for air equalizing means for substantially equalizing the ambient air entering the secondary air duct and flowing through the ports to the combustion chamber. The invention further includes novel means for securely locking the refractory lining in the protective front flange. The locking means comprise a locking taper at the outer flange shell, which eliminates the typical hanger supports required interiorly of the flanges and the attendant labor required in placing these supports. Eliminating the supports simplifies ramming the refractory material into the flange shell and reduces Void spots therein.

Accordingly, the invention provides for secondary air duct means contiguous with the burner shell, port means communicating between the duct and the combustion chamber, and air passage means for conducting heated air into the secondary air duct for flow through the ports into the combustion chamber. The air passage means extend from the secondary air duct through the protective front flange of the combustion chamber. Air entering the passages is heated by convection from the vast quantities of thermal energy adjacent the flange face located at the combustion chamber outlet. Also, air flowing through the passages is heated by conduction through the refractory flange which is rapidly heated after ignition of the aspirator burner. This hot air flows through the air passage means to the secondary air duct. The air flow through the air passages is controlled by a rotatably movable valve ring, thereby enabling control of the secondary air temperature by regulating the quantity of heated air mixed with unheated, ambient air, also entering the secondary duct. The mixed air is directed into the combustion chamber through the interconnecting ports.

Accordingly, the primary object of this invention is to improve the combustion efficiency of an aspirator burner.

Another object of this invention is to increase the maximum temperature capabilities of an aspirator type burner.

It is also an object of this invention to provide means for increasing and regulating the maximum temperature of an aspirator burner.

A further object of this invention is to prevent cooling and coagulation of normally high viscosity fuel oil in the combustion chamber of an aspirator burner during addition of secondary air adjacent the point of atomization of fuel oil and a primary air source.

It is also an object of this invention to provide means for substantially equalizing the flow of secondary ambient air into the combustion chamber of an aspirator burner.

A further object of this invention is to provide novel means for retaining a refractory lining in a flange shall of an aspirator burner thereby eliminating interior flange hangers and obviating voids in the flange refractory material.

Further objects of this invention will become apparent from a reading of the following description in conjunction with the accompanying drawings, wherein:

FIG. 1 is an elevational cross-sectional view of an aspirator burner incorporating the improvements of the invention, taken along offset section line 1-1 of FIG. 2.

FIG. 2 is a right-end elevational view of the aspirator burner shown in FIG. 1, taken along section line 2*-2 thereof.

FIG. 3 is a cross-sectional elevational view taken along line 3-3 of FIG. 1 showing the heated secondary air valve construction and the secondary air ports.

FIG. 4 is an enlarged fragmentary cross-sectional view taken along line 4-4 of FIG. 3 showing details of the valve retaining bracket and the physical connection between the secondary air tube and the secondary air duct.

FIG. 5 is an enlarged fragmentary cross-sectional view taken along line 5-5 of FIG. 3 showing further details of the valve and bracket.

Referring now to FIGS. 1 and 2, an aspirator burner generally referred to by reference numeral 1()V is illustrated and includes a primary air housing 12 having a primary air inlet 14 which is connectable to a low pressure air source, not shown; a fuel delivery system 15; a combustion tube enclosing a combustion chamber 22; and secondary air supply means 23.

More specifically, the fuel delivery system includes a fuel conduit extending longitudinally through the primary air housing, and terminating in a nozzle assembly 18 which is circumferentially surrounded by the primary air flow through an orifice 19. The nozzle of the illustrated embodiment is designed for fuel oil, and may be constructed in accordance with the teachings of Meyer Pat. No. 3,015,449 which issued Jan. 2, 1962. Differing nozzle constructions well known to those familiar with the art could be used for other fuels mentioned above such as gas, pulverized coal and sawdust, each of the latter two materials being carried in an air vehicle.

The combustion tube 20 comprises a generally uniform diameter outer shell 24 fabricated of metal or the like, having a back wall 26 centrally apertured at 28 for receipt of the front of the primary air housing 12, and having a radially enlarged front flange 29. The burner tube further includes 'a high temperature resistant refractory lining 32l molded interiorly of the shell, said lining defining the combustion chamber 22. The lining forms a gradual taper from the rear wall which has a heavy lining, to the flange where the lining is generally thinner, except for the flange per se. The difference in lining thickness causes the combustion chamber to assume an outward flare, starting with a small diameter adjacent back wall 23 and flaring outwardly to larger diameter adjacent the front ange.

As stated previously, the front of the burner tube com- (prises a radially expanded portion of shell 24 forming a flange 29 including a ange wall 34, filled with refractory material 36. The exposed refractory material defines a front face 38 which is presented to the furnace or other apparatus being heated by the burner. This front face functions to prevent damage to the burner from radiation reflected from the apparatus being heated.

The flange shell includes an inwardly tapering circular wall 40` which decreases the flange diameter from wall 34 to front face 38. This taper locks in and retains the refractory material in the flange shell, resisting the effects of thermal expansion tending to separate the material from the shell. This lock-in taper replaces previously required interior support hangers which were laborious to install and prevented compact and complete ramming of the refractory material into the flange shell.

Outwardly of shell 24 and adjacent back wall 26, a circumferential secondary air duct 48 is provided which includes an outer circular wall 44 and a front wall 46. These walls, together with shell 24 and back wall 26, form a toroid-like, enclosed secondary air duct 48, having a rectangular cross-section. A plurality of secondary air ports S0, best seen in FIGS. 1, 2 and 5, interconnect the combustion chamber 22 with the secondary air duct.

More specifically, each port 50 includes an inlet terminus 51 through shell 24, and an outlet terminus 53 at the surface of the refractory lining defining the combustion chamber. The outlet termini are substantially aligned with the area where the fuel and primary air of the burner are mixed, i.e. slightly forwardly of nozzle 18. Thus, the secondary air increases the combustion support for more eicient burner operation. While four secondary air ports are shown in the preferred embodiment, it is obvious that a greater or lesser number of ports could be used, depending upon the size of the burner. Also, the diameter of the ports may be varied within reasonable limits.

Secondary air duct 48 is supplied with ambient air through ambient air inlets 52 and 54, one inlet being disposed on either side of the duct. The inlets comprise internally threaded collars 60 and 62 threadingly secured to extension nipples 56 and 58, respectively.

As best seen in FIG. 5, to maintain a substantially equalized ambient air ow from the secondary duct inlets to the port inlet termini, 51, air bafes 64 and 68 are provided for dividing the ambient secondary air and directing each of the divided air portions toward a particular port. The baffles reduce the tendency of one port being supplied with a greater quantity of ambient secondary air and contributes to more even combustion.

While the main source of secondary air is unheated ambient air which is drawn through secondary air inlets 52 and 54, in accordance with the invention, an additional quantity of secondary air is heated and conducted to the Secondary air duct for mixing with the unheated ambient air prior to introduction into the combustion chamber via ports 50. The heat for this additional quantity of secondary air is derived from the thermal energy of the aspirator burner.

The heated air is conducted to duct 48 through a plurality of hollow tubes 70 defining air passages extending parallel to the longitudinal axis of the burner. Each of the tubes 70 extend from the front protector face to the front wall 46 of the secondary air duct. At the ange, each tube 70 penetrates the refractory material at 71, and the material is cored at 72 thereby providing a forward tube extension without-exposing the tube per se to the intense heat radiated from the apparatus being fired. As shown in FIG. 2, four secondary air tubes 70 are provided substantially equ'ally distant around the burner shell, and each of the tube extensions exit through the flange face at 74.

Air is drawn through the burner tubes under the influence of a low pressure region due to the high velocity air passing through the combustion chamber, past the port outlets. Air drawn through the tubes, which as noted above comprise the secondary air passages, is heated by two methods. First, the air is drawn from adjacent the front of the protector face, and is heated to an extremely high temperature by convection, due to the exiting gasses and the thermal energy of combustion. Second, the refractory material and the flange display a rapid temperature increase immediately after ignition of the burner, thus air flowing through the passage 70 is heated by conduction and convection through portion 71 of the tube and the cored opening through the flange. This heat flow to the secondary air source is beneficial in reducing the flange temperature.

The left end of tube 70, as seen in FIG. 1, terminates just forward of front wall 46 of the secondary air duct. The front Wall includes a plurality of apertures 73` each permanently aligned with a respective tube 70 to allow free flow of heated secondary air from the tube through the front wall and into the secondary air duct.

The quantity of heated secondary air flowing through the air passages and into the secondary air duct for mixing with the unheated ambient air, is controlled by a valve assembly generally referred to by numeral 75. Control of the heated air entering the secondary air duct provides a means for regulating of the maximum burner temperature. This regulation is important for maximum burner versatility, since many furnaces in which the burner may be used can not tolerate the extremely high temperatures which a burner constructed in accordance with the invention is capable of producing.

The valve assembly comprises a valve ring 77 having an outer circumference 80 and an inner circumference 82. The ring includes a plurality of spaced openings 8-4, each of which are simultaneously alignable with respective secondary air passage tubes 70. The valve ring is secured for rotation against the front of secondary air duct wall 46 and thus may be rotatably shifted to an infinite number of positions for fully or partially aligning apertures 84 with the passages through pipes 70, or for sealing the duct from the flow of heated air. Movement of the valve ring is easily accomplished by an upstanding handle 86 having an extension 87. The handle is secured to the valve ring by suitable fasteners 88. Calibration markings 89 may be provided adjacent the extension, for visual indication of the valve condition.

As best seen in FIGS. 4 and 5, a plurality of dual function brackets 90 are provided adjacent front wall 46, for securing the left end of tubes 70 thereto, and for maintaining the valve ring in place. Each bracket includes an internally threaded opening 92 for receipt of a threaded end 94 of a tube 70. The brackets are secured to the duct front plate by suitable fasteners 96. Each bracket includes a relieved groove 98 in which the valve ring is seated, but suitable clearance is provided so that as the bracket is tightly secured to the duct plate, the valve ring may be rotated by movement of handle 86. In FIG. 5, the secondary air passage is fully closed by the valve ring, since the opening 84 through the ring cornpletely covers the opening 72 through the front wall, and also covers the air passage through tube 70.

What has been described is an aspirator burner having a heated secondary air supply for increasing its combustion efficiency and its maximum temperature capabilities. In addition, the above described aspirator burner includes an improved flange construction for retaining the refractory material therein, and includes secondary air equalization means for more uniform distribution of secondary air into the combustion chamber.

It is obvious that upon study by those skilled in the art the disclosed invention may be altered or modified both in physical appearance and construction without departing from its inventive concept. Therefore, the scope of protection to be given this invention should not be limited by the embodiment described above, but should be determined by the essential descriptions thereof which appear in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a fluid fuel burner including a housing defining a chamber; means for introducing fuel and a low pressure primary source of air into said chamber through a first end of said housing for a-dmixing and combustion therein; means for introducing a secondary source of air into said chamber substantially adjacent the introduction of said fuel and primary source of air for more eflicient combustion of said fuel, the combustion products ineluding thermal energy exiting through an unobstructed outlet at a second end of said chamber; the improvement comprising: secondary air duct means outwardly of said housing including a first air inlet communicating with unheated ambient air at atmospheric pressure comprising a first source of secondary air; port means through said housing connecting said duct means to said chamber; a second air inlet comprising a second source of secondary air; means for heating said second source of secondary air prior to its introduction into said chamber; and passage means conducting said heated secondary air to said duct means for flow through said port means into said chamber, whereby the combustion temperature of the burner is increased and the combustion efficiency of said fuel is further increased; the combustion in said chamber and the resultant gaseous flow therethrough causing a subatmospheric pressure within said duct for drawing the heated secondary air through said passage means and for drawing said unheated ambient air into said duct; said heated and unheated secondary airs mixing in said duct and together comprising said secondary air supply.

2. A fluid fuel burner adapted to heat a furnace or like environment, comprising: a refractory lined shell defining a chamber having a wall at one end thereof and an open, substantially unrestricted second end for exiting of the thermal energy produced by said combustion; means for introducing fuel and low pressure air through said wall for admixing and combustion within said chamber; means for introducing additional, preheated air, into said chamber for increasing the combustion temperature of said burner and the combustion efficiency of said fuel; said shell adjacent the second end of the chamber comprising a radially expanded, refractory filled flange section having a protective face adjacent said furnace affording radiation protection for said burner; said radially expanded shell portion including an inward taper at said protective face for preventing separation of said lining from said shell and obviating refractory voids by eliminating the necessity for interior support hangers in said flange.

3. The fluid fuel burner as set forth in claim 1 wherein said housing includes a refractory lining forming said chamber; said port means connecting said duct means to said chamber comprising a plurality of port openings through said housing and said refractory lining, and including additionally: -air flow equalizing means interior of said duct means for substantially equalizing the flow of ambient air to said port openings.

4. The fluid fuel burner as set forth in claim 1 wherein said housing includes a refractory lining defining a tapered, generally cylindrical combustion chamber; and wherein said passage means for conducting the heated portion of said secondary air to said duct means comprise a plurality of individual air passages extending from a point adjacent said chamber outlet to said duct means, said air entering said passages being heated by convection from the thermal energy exiting said chamber.

5. The fluid fuel burner as set forth in claim 4 further including: valve means for regulating the proportion of heated to unheated secondary air entering said secondary air duct thereby providing control of said burner temperature.

6. The fluid fuel burner as set forth in claim 5 wherein said valve means are interposed in the second-ary air passages for controlling the amount of heated secondary air entering said secondary air duct, and including additionally: air flow rbaflles adjacent said ambient air inlet to substantially equalize the flow of ambient air to said port openings.

7. The fluid fuel burner as set forth in claim 6 wherein said housing further includes a circumferentially enlarged protective refractory flange having la front face adjacent the chamber outlet; and wherein each of said air passages are defined by a tube extending from said duct to said refractory flange; said flange being cored co-axial with said tube, forming an extension for said air passage and preventing direct exposure of said tube to said thermal energy; and wherein said tube is heated by conduction from the normally hot flange, heating said secondary air in said passages and simultaneously reducing the temperature of said flange.

8. The fluid fuel burner as set forth in claim 6 wherein said housing includes a front flange formed with a circumferential inward taper to retain said refractory in place without additional interior flange supports.

9. The fluid fuel burner as set forth in claim 8 wherein said housing further includes a circumferentially enlarged, heated refractory flange having a front face adjacent the chamber outlet, and wherein each of said air passages extend through said refractory flange; said air passages thereby Ibeing heated by conduction from the normally hot flange, heating said secondary -air in said passages and simultaneously reducing the temperature of said flange;

10. The fluid fuel burner as set forth in claim 9 wherein said housing forms a circumferential inwardtaper at said flange to retain said refractory in place without additional interior flange supports.

11. The fluid fuel burner as set forth in claim 2 including additionally: duct means outwardly of said shell and contiguous therewith; a plurality of ports extending through said shell and said refractory lining, connecting said chamber to s-aid duct means; and a pluralityof hollow tubes defining air passages for said additional air; said hollow tubes extending from said protective face, through said refractory filled flange, to said duct means for conveying air to said chamber via said ports; said air flowing through said air passages being heated by convection by said exiting thermal energy and by conduction through said flange refractory.

12. The fluid fuel burner as set forth in claim 11 further including: adjustable valve means in said air passages adjacent said duct means for controlling the quantity of heated air flowing therethrough; said duct means including an ambient air inlet; an equalizer baille adjacent said inlet to equalize the air flow to said ports; said ambient air mixing with said heated air and together comprising said additional air for said combustion chamber.

13. The fluid fuel burner as set forth in claim 12 wherein said valve means include a manually rotatable valve ring defining a plurality of apertures alignable with said air passages.

References Cited UNITED STATES PATENTS 1,027,912 5/1912 Schwartz 431-161X 2,927,632 3/1960 Fraser 431--161X FOREIGN PATENTS 462,195 1/1950 Canada. -447,624 5/ 1936 Great Britain.

EDWARD G. FAVORS, Primary Examiner

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