US3315726A

US3315726A - Industrial burner

Info

Publication number: US3315726A
Application number: US441241A
Authority: US
Inventors: Williams John Roger
Original assignee: Selas Corp of America
Current assignee: Selas Corp of America
Priority date: 1965-03-19
Filing date: 1965-03-19
Publication date: 1967-04-25
Anticipated expiration: 1984-04-25

Description

J. R. WILLIAMS INDUSTRIAL BURNER Filed March 19, 1965 .V I flM 0 w INVENTOR.

JOHN ROGER WILLIAMS ATTORNEY.

April 25, 1967 United States Patent 3,315,726 INDUSTRIAL BURNER John Roger Williams, Ambler, Pa., assignor to Selas C01- poration of America, a corporation of Pennsylvania Filed Mar. 19, 1965, Ser. No. 441,241 3 Claims. (Cl. 158-117) The present invention relates to industrial burners, and more particularly to a gas burner that has an exceptionally large turn-down ratio.

In modern industrial heating there is an increasing requirement for burners having a high turn-down ratio or the ratio of the capacity of the burners between their maximum and minimum operating ranges. This has been brought on, in large part, by the versatility of modern furnaces with respect to the temperature range through which they operate and the various types and loads of work they are designed to heat.

It is customary at present, when firing a furnace at less than its maximum capacity, to turn selected burners off and, in some cases, to use pilot flames. This results in uneven furnace temperature and heating. It also creates problems in relighting the burners in a hot furnace when the temperature must be raised again.

, It is an object of the invention to provide an industrial burner having a high turn-down ratio that will operate equally as well at the maximum and minimum limits of its capacity.

It is a further object of the invention to provide a burner having a fuel orifice of variable size, which orifice will automatically assume the proper size for the pressure of the fuel being supplied to it.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a section through the burner, and

FIG. 2 is a section taken on line 22 of FIG. 1.

Referring to the drawing, there is shown a portion of a furnace wall 1 built in accordance with ordinary furnace practice and having a metal backing plate 2. Located in the furnace wall and forming a portion thereof is a ceramic refractory burner block 3 that has provided on 'its front face, a cup-shaped depression 4. The block also has an opening 5 extending from the base of the cup to the other side of the block and a corresponding opening in the refractory of the wall through which the fuel distributing portion of a burner can be inserted.

The burner is shown as including a casting 6 having an extension 7 thereon which is concentric with the opening 5 of the burner block. A cylinder tipholder 8 is threaded to this extension and extends through opening 5 a short distance into the base of depression 4. Casting 6 forms a chamber 9 having a fuel inlet 11 through which fuel is supplied from a suitable source at a pressure that is regulated by a valve 12 and which can be indicated on a pressure gauge 13.

The flow of fuel, which in this case is a combustible mixture of a fuel gas and air, into the depression 4 where it is burned, is controlled by a variable orifice the size of which depends upon the pressure of the fuel. To this end there is provided a distributor tip 14 which is received in the end of tipholder 8. It will be noted that the end of holder 8 is flared outwardly in a conical shape and that the tip is frustro-conical with the surface thereof complementary to the surface of the flared portion of holder 8. The tip is provided on its surface with a plurality of axially 3,315,726 Patented Apr. 25, 1967 extending shoulders forming between them passages 15 through which the fuel mixture can flow when the tip engages holder 8 or at the minimum size of the orifice. These passages toward their outer ends bend in a generally radial direction under a cap 16 on the end of distributor tip 14. The tip is guided in holder 8 by means of a plurality of guide flanges 17 formed on its end away from the cup.

The distributor tip 14 is moved axially in tipholder 8 by means of a rod 18 that is attached thereto. This rod extends rearwardly through the chamber 9 and the back wall of casting 6. The rear end of the rod has attached to it a diaphragm 19 that is sealed at its outer edges to the back wall of casting 6 in order to form a pressure tight connection. The rod is also provided with a second diaphragm 21, the outer edge of which is sealed to the back of casting 6 by means of an end cap 22. The rod extends through this end cap and has around its end a compression spring 23 one end of which bears against the cap and the other end of which bears against a nut 24 that is threaded to the end of the rod. This spring and its adjusting nut are covered by a cap 25 which is threaded to end plate 22 to form a pressure tight connection therewith.

A chamber 27 is formed between the diaphragms H and 21 which chamber communicates with the atmosphere through a passage 28. A second chamber 29 is formed between diaphragm 21 and end plate 22 which chamber is connected with chamber 9 by means of a passage 31. Therefore, pressure of the fuel mixture supplied to chamher 9 can be applied to the left face of diaphragm 21 to move rod 18 and distributor tip 14 in opposition to the bias that is placed upon them by spring 23.

It is noted that the surface of depression 4 is provided with a groove 32 closely adjacent to and below the outlet of passages 15 and that the surface of the depression continues substantially along an even curve 33 to the surface of the burner block with the area of the depression increasing in size toward the surface of the block. The surface of the depression has been shown in the drawing as having a small number of steps on it. These steps serve the purpose of producing a slight turbulence in the combustible mixture being discharged from the tip across the surface in order to speed up combustion and increase the incandescence produced in the cup.

Before operating the burner, nut 24 is adjusted to tension spring 23 sutficiently to hold tip 14 in its left position, with the fuel discharge orifice of minimum size, until some predetermined fuel mixture pressure is reached. Nut 26 is also adjusted to limit the amount of movement of tip 14 to the right, or the maximum size of the fuel discharge orifice. Spring 23 is selected to permit movement of tip 14 through its range as the fuel pressure varies through a given range, depending upon the size and use of the burner.

When the fuel mixture is first turned on by opening of valve 12, the mixture Will flow through passages 15 into the cup in a substantially radial direction. The individual jets of fuel from passages 15 are ignited and sweep along the surface of the cup to heat it. A low pressure area is created in groove 32 which traps some of the fuel where it burns as a pilot. As the pressure of the fuel mixture supply is increased the tongues of flame are elongated to extend out further on the cup surface. This burning produces the characteristic involution of radiant cup burners to cause the flames to bend and follow the cup contour. As valve 12 is opened, and the pressure of the fuel mixture is increased, this pressure will be applied to the left of diaphragm 21 causing tip 14 to move to the right, thus increasing the size of the discharge orifice and the flow of fuel. As tip 14 moves, its surface leaves the inner flared surface of holder 8, thus creating an annular discharge rather than individual jets of fuel. Tip 14 is centered in the holder by vanes 17, however, and passages 15 still have a guiding function, so that burning is even around the cup and the flame still wipes the cup surface. Thus, as the fuel pressure is increased, more fuel is supplied through a larger orifice and a larger area of the cup surface is heated to incandescence.

Since the discharge orifice area increases and decreases as valve 12 is opened or closed, the pressure of the fuel mixture flowing into the cup and its velocity is maintained above that value at which a backfire would occur.

As an example, the passages formed by grooves 15 on the surface of tip 14 were sized to pass about 125 cubic feet per hour (c.f.h.) of fuel mixture at 4 inches water column (in. W.C.) pressure when the tip engages the holder. Spring 23 was compressed so that movement of tip 14 would begin when the mixture pressure reached 12 in. WC. and would move a maximum of about inch when the mixture pressure had increased to 28 in. WC.

Under the above conditions the burner operated successfully from a capacity of 125 c.f.h. at 4 in. W.C. to a capacity of about 1980 c.f.h. at 50 in. WC. The turndown ratio between these two fuel mixture pressures is, therefore, 15.8 to 1. For a standard fixed port burner, the ratio of two flow rates is directly proportional to the square root of the ratio of the pressures. By this rule a fixed port burner which gives 125 c.f.h. at 4 in. WC. would be expected to give 438 c.f.h. at 50 in. W.Cv or a capacity ratio of 3.5 to 1.

Thus it will be seen that the disclosed arrangement in which the fuel mixture pressure varies the size of the fuel orifice of the burner will permit an increase in the turn-down of the burner of unexpectedly large proportions. In addition, the varying size of the fuel orifice insures that the velocity of the fuel through the orifice will at all times be high enough so that flashback cannot occur.

While in accordance with the provisions of the statutes I have illustrated and described the best form of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit and scope of the invention set forth in the appended claims, and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features.

What is claimed is:

1. In an industrial burner, ceramic means forming a cup-shaped depression in which combustion is to take place, a hollow, cylindrical fuel discharge member extending into the base of said depression and in sealed relation thereto, said member having a fuel air mixture passage therein that flares outwardly in a conical shape at the end thereof, a frustroconical distributor tip received in and complementary to the flared portion of said passage, said tip having a cap thereon adapted to engage the end of said member, a rod extending axially through said member and attached to said tip and projecting beyond said member in a direction opposite to said passage, said tip being provided around its surface with channels through which fuel can flow, resilient means axially of and attached to the portion of said rod beyond said member for biasing said rod in a direction to move the head of said tip against said member, a pressure responsive element attached to said rod beyond said member, means to supply a fuel air mixture under pressure directly to the interior of said member, means to apply said fuel air mixture pressure to said element to move said rod axially against the bias of said resilient means, and means to vary the pressure of said fuel air mixture supply.

2. In an industrial burner, the combination of means forming an annular fuel discharge orifice including a hollow cylindrical member with an end, the interior of said end being flared outwardly, a distributor tip received in said flared end and complementary thereto, said tip being provided with a cap engaging said end and passages formed around it and under said cap, a rod attached to said tip and extending through and beyond said member, resilient means attached to the portion of said rod beyond said member and operative to bias said rod in a direction to hold said cap against said end, pressure responsive means attached to the portion of said rod beyond said member and operative upon application of pressure thereto to move said cap away from said end and thereby enlarge said passages, means to supply a fuel air mixture under pressure directly to the interior of said member to flow through said passages, means to apply the pressure of said fuel air mixture to said pressure responsive means, and means forming a ceramic cup-shaped surface surrounding and in sealed relation to said cylindrical member and extending away from said end across which fuel flowing from said passages travels.

3. In an industrial burner, the combination of structure forming a chamber having a fuel outlet extending therefrom, said structure being provided with a chamber wall having an opening therein opposite said fuel outlet and axially aligned therewith, a distributor tip received in said fuel outlet and operable variably to throttle said fuel outlet as said tip is moved axially therein, said tip being provided with axially extending channels on its surface to form fuel-air mixture passages in said outlet, a rod extending from beyond said wall, through said opening and chamber and attached to said tip, means including a flexible diaphragm forming a second chamber surrounding said rod beyond said wall, said diaphragm being attached to said rod, a compression spring surounding said rod beyond said second chamber, means on said rod compressing said spring to move said rod in a direction for said tip to throttle said outlet, means to supply a fuel air mixture under pressure directly to said first chamber to flow through said outlet, means to apply the pressure of said fuel air mixture to said second chamber and said diaphgram thereby to move said rod in opposition to the bias of said spring, means to vary the pressure of the fuel air mixture supply and means forming a ceramic cup-shaped refractory surface surrounding and in sealed relation to said outlet and extending outwardly from the end of said passage, said fuel-air mixture passages directing the fuel-air mixture along said surface.

References Cited by the Examiner UNITED STATES PATENTS 701,026 5/ 1902 Elliott. 2,572,675 10/1951 Swenson et al. 158l 17 2,815,175 12/1957 Swenson l58l17 X 2,904,108 9/1959 Blaha 158-113 JAMES W. WESTHAVER, Primary Examiner.