US3782883A

US3782883A - Flat flame burner having a low air to gas ratio

Info

Publication number: US3782883A
Application number: US00245932A
Authority: US
Inventors: F Vereecke; J Nesbitt; K Hemsath
Original assignee: Midland Ross Corp
Current assignee: Surface Combustion Corp; Grimes Aerospace Co
Priority date: 1972-04-20
Filing date: 1972-04-20
Publication date: 1974-01-01
Anticipated expiration: 1991-01-01
Also published as: AU5359273A; IT981998B; DE2315907B2; RO65178A; JPS5239499B2; DE2315907C3; ES190009U; CA961403A; JPS4917533A; DE2315907A1; GB1414043A; FR2181326A5; BR7302725D0; ES190009Y

Abstract

A flat flame burner capable of sustaining combustion at a low air to gas ratio. The burner has a cup shaped combustion chamber with outwardly extending tapered walls leading from the combustion chamber. At the upstream end of the combustion chamber, generally tangential means is provided for introducing a mixture of gas into the combustion chamber. The geometry of the burner is such that virtually total reaction takes place within the combustion chamber and along the tapered walls.

Description

United States Patent [1 1 Nesbitt et a1.

[ 1 Jan. 1,1974

[ FLAT FLAME BURNER HAVING A LOW AIR T0 GAS RATIO [75] Inventors: John D. Nesbitt, Chicago, 111.; Klaus II. Hemsath, Sylvania, Ohio; Frank J. Vereecke, Palmyra, Mich.

[73] Assignee: Midland-Ross Corporation,

Cleveland, Ohio 22 Filed: Apr. 20, 1972 211 Appl. No.: 245,932

[52] US. Cl 431/185, 431/348, 239/399 [51] Int. Cl. F23m 9/00 [58] Field of Search 431/348, 173, 185,

[56] References Cited UNITED STATES PATENTS 1,656.907 1/1928 Bansen 431/185 3.315.726 4/1967 Williams 431/348 2,890,746 6/1959 Dollinger 431/173 3,286,997 11/1966 Lcdbetter 239/399 2,969,833 1/1961 Bloom et a1. 431/348 3,221,797 12/1965 Wall 431/348 2,941,585 6/1960 Loebel et a1 431/174 Primary ExaminerCarroll B. Dority, Jr. Attorney-Peter Vrahotes [57] ABSTRACT A flat flame burner capable of sustaining combustion at a low air to gas ratio. The burner has a cup shaped combustion chamber with outwardly extending tapered walls leading from the combustion chamber. At the upstream end of the combustion chamber, generally tangential means is provided for introducing a mixture of gas into the combustion chamber. The geometry of the burner is such that virtually total reaction takes place within the combustion chamber and along the tapered walls.

12 Claims, 3 Drawing Figures FLAT FLAME BURNER HAVING A LOW AIR TO GAS RATIO BACKGROUND OF THE INVENTION With the greater demands placed upon the heat treating industry, it is becoming desirable to have a burner which will not only convey heat to work, but do it in such a manner that the work is provided with a protective atmosphere. This may be achieved by a burner which conveys heat generally radiantly, as opposed to immediately exposing the work to the products of combustion, and to subsequently provide a protective atmosphere to the heat treating area. This particular need is generally satisfied by a flat flame burner which is able to operate at low air to fuel ratios. Such burners are available on the market today, however, those presently available have certain shortcomings.

The primary shortcoming of the present day burners is that they are unable to accomplish complete combustion within the burner itself and much of the gas mixture leaves the area of the burner and completes combustion at a location away from it. This has certain disadvantages, as much of the heat is lost to the surface of the burner which would normally transfer the heat radiantly, and combustion in the area of the work tends to promote oxidation since there is a portion of unreacted air. In addition to this, it is difficult to obtain a burner which not only satisfies the requirements of low air to fuel ratio, but also has a large tumdown ratio and the stability that is required for a large turndown ratio.

It is therefore an object of this invention to provide a unique flat flame burner.

It is another object of this invention to provide a flat flame burner with high stability.

It is s till another object of this invention to provide a flat flame burner in which substantially complete combustion takes place within the burner.

It is a further object of this invention to provide a flat flame burner having a high tumdown ratio.

These and further objects will appear from the following portion of the specification and drawing, wherein:

FIG. 1 is a vertical cross-sectional view of a burner incorporating the principles of the invention taken along line 11 of FIG. 2;

FIG. 2 is a horizontal cross-sectional view taken along line 2-2 of FIG. 1; and

FIG. 3 is a plan view of the bumer shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, a burner is shown generally at secured to the top of a furnace l2 and having a portion received within an opening 14 of the furnace. The burner comprises a housing 16 which has a metallic shell 18 that receives refractory block 20. The refractory block 20 has a cup shaped combustion chamber 22 which is confluent with the interior of the furnace. An annular plate 24 is disposed about the housing 16 and secures the housing to the furnace by the use of bolts 26 received within an annular plate 28 welded to the top of the furnace 12. The portion of the burner 10 received within the opening 14 has a tapered, generally conical member 30 with a right cylindrical portion 32 whose diameter is somewhat larger than the diameter of the cup shaped combustion chamber 22, thereby defining a transverse shoulder 34 therebetween. The ratio of the length of the right cylindrical portion 32 to its diameter should be 1/5 to H2, the preferred ratio being approximately U4. The ratio of the cylindrical 32 diameter to the chamber 22 diameter should be between 2/1 and 6/5. The conical member 30 has tapered walls 36 that provide a smooth and regular surface from the upstream end of the conical member to the furnace 12 interior.

The upstream end of the combustion chamber 22 has a pair of dual diameter ports 38 or openings. Each of the ports 38 has a large diameter portion 42 upstream from the chamber 22 and a small diameter portion 44 adjacent to the chamber. Received within each large diameter portion 42 of these ports 38 is one end of a sleeve 40. Each sleeve 40 has a first opening 46 at the outermost end thereof of which receives a coaxially disposed gas line 48 that has a portion which extends a dis tance into the ports 38 and an external portion which may be connected to a source of combustible gas. The interior end of the gas line 48 within the sleeve 40 is supplied with a spud 50 which has a small opening 52 therein. Each sleeve 40 also has an opening 54 located at the upper end thereof, which opening receives an air manifold 56. The air manifold in turn is connected to an air supply line 58. Received within the housing 16 and directed to the combustion chamber 22 is a pilot 60.

The ports 38 are generally tangentially disposed to the combustion chamber 22 as can be seen in FIG. 2. The ports 38 are not exactly tangential, but are offset by 24 so that the gases are directed slightly away from the wall of the combustion chamber 22. It has been found that having this slight angle to the tangential promotes mixing and stability within the combustion chamber 22. In a burner of the type to which this invention is directed, it is advantageous to promote mixing to achieve maximum combustion intensity. It has been found that particular relationships between the small diameter portion 44 of the ports 38 and the large diameter portion 42 aid in the primary mixing of the air and gas. Specifiallly, it has been found that if the diameter of the large portion 42 is approximately twice that of the smaller portion 44, better mixing is achieved, and a back pressure is obtained. Additionally, the relative lengths of the

port portions

42 and 44 are important, and the length of the larger diameter portion 42 should be approximately twice the length of the smaller diameter portin 44. It also has been found that if the length from the spud. opening 52 to the necked down portions of the ports 38, which length is indicated by a, is approximately 5 to 10 times as great as the diameter of the spud opening 52, mixing is promoted. Preferably, this difference is approximately 7.5. Additionally, this also aids in creating a back pressure required for operation of the burning.

After the gases have been supplied to thecombustion chamber 22 and ignited therein, further ixing is achieved by the pressure of the shoulder 34. Once the gases have reached the end of the cone shaped section of member 30, the gas mixture is virtually completely reacted, transferring heat to the tapered walls 36 which act as radiating members.

The burner 10 has a high stability when used with either cold or preheated air. In a test run of the burner 10, no instability was noted in operation with l,000 F. preheated air at air/gas ratios ranging from 10/ l to 5/1. The burner was also found operational at air to gas ratios as low as 6.5/1 using cold air. At ratios below 6.5/1 using cold air the presence of free carbon was found in the flue gas. Again using cold air, slight instability was detected at ratios above 17/1, but the instability did not reach a point of flame blowout at /1.

What is claimed is:

1. A flat flame burner comprising: a housing, an opening within said housing defining a cup shaped combustion chamber, a pair of dual diameter ports extending through the housing to the interior portion of the wall of said chamber in a generally tangential manner, a member secured to the housing and having a generally conically-shaped interior in a confluent relationship with said chamber, said member having its smaller diameter end adjacent to and larger than the diameter of said chamber to define a shoulder, each of said ports having a first portion adjacent said chamber and a second portion adjacent and upstream of said first portion, said second portion having a larger diameter than said first portion, and means for supplying combustion gas and air to said ports in a coaxial direction.

2. The burner of claim 1 wherein each of said ports is positioned at a 24 angle relative to the tangential of said chamber.

3. The burner of claim 1 wherein said second portion of each port has a diameter approximately twice as large as the diameter of said first portion.

4. The burner of claim 3 wherein the length of said second portion is twice the length of said first portion.

5. A flat flame burner comprising: a housing, a cup shaped opening within said housing defining a chamber, a member secured to the housing and having a recessed interior in the form of a right cylindrical portion having tapered walls extending from said cylindrical portion, said cylindrical portion being adjacent said chamber, a plurality of ports extending through the housing into said chamber in a generally tangential manner each of said ports having a first portion adjacent said opening with a first diameter and a second portion adjacent and upstream of said first portion with a second diameter larger than said first diameter, means for providing air and gas to said second portion of each of said ports in a coaxial direction.

6. The burner of claim 5 wherein the length of said second portion is approximately twice as long as the length of said first portion.

7. The burner of claim 5 wherein said gas supply means is a longitudinally extending tube received within the second portion of said port with the terminating end of said gas tube having an opening therein.

8. The burner of claim 5 wherein the diameter of said right cylindrical portion is larger than the diameter of said cup shaped opening thereby defining a transverse shoulder.

9. The burner of claim 7 wherein the distance from where the tube terminates within said second portion to the beginning of said first portion is between 5 and 10 times greater than the diameter of said opening in said tube.

10. The burner of claim 9 wherein said distance is 7.5 times greater than the diameter of said opening.

11. The burner of claim 5 wherein the diameter of said right cylindrical portion is 2/1 to 5/1 times greater than its length.

12. The burner of claim 8 wherein the diameter of said right cylindrical portion is 6/5 to 2/1 times greater than the diameter of said opening.

257533 UNHE'I) STATES PA ENT OFFICE") (TI id H" l" i H'*.?[ (2 AT E 0 F C U R R E (35H @N Patent Ne. 883 Dated January 1, 1974 Inventor) John D. Nesbitt, KleueH. item eath and Frank J. Vereecke:

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

1* W K' Abstr act, line 7, after "gas". insert rand air Column 2, line 16, delete "o".- Line/Ll, change "specifia lll y" to specifically Line48, ehange "portin" to portion Line 57 change "ixing"' to -Yf'imixing Line 58,achange "pressure" to---- presence Q? l Celurnn 4, line 23, ehange; e" to to Signed and sealed this 16th (18.15] of April 19711 I (SEALY Attest EDWARD 1%.1 L3T0HE1J JR. n c; MMKSHALL DANN Attesting Officer. Commissionenof Patents

Claims

2. The burner of claim 1 wherein each of said ports is positioned at a 2*-4* angle relative to the tangential of said chamber.

5. A flat flame burner comprising: a housing, a cup shaped opening within said housing defining a chamber, a member secured to the housing and having a recessed interior in the form of a right cylindrical portion having tapered walls extending from said cylindrical portion, said cylindrical portion being adjacent said chamber, a plurality of ports extending through the housing into said chamber in a generally tangential manner, each of said ports having a first portion adjacent said opening with a first diameter and a second portion adjacent and upstream of said first portion with a second diameter larger than said first diameter, means for providing air and gas to said second portion of each of said ports in a coaxial direction.

9. The burner of claim 7 wherein the distance from where the tube terminates within said second portion to the beginning of said first portion is between 5 to 10 times greater than the diameter of said opening in said tube.