US3739990A

US3739990A - Atomizing burner nozzle tip

Info

Publication number: US3739990A
Application number: US00189671A
Authority: US
Inventors: L Triggs
Original assignee: Combustion Engineering Inc
Current assignee: Combustion Engineering Inc
Priority date: 1971-10-15
Filing date: 1971-10-15
Publication date: 1973-06-19
Anticipated expiration: 1990-06-19

Abstract

A nozzle tip for a liquid fuel atomizing burner is provided with an annular aperture within which the fuel and atomizing medium are mixed and from which the mixture is discharged as an atomized spray. The nozzle tip of the invention provides a more effective spray distribution which requires reduced fuel pressures. The effects of plugging of one or more of the ports through which the atomizing medium is conducted are minimized.

Description

United States Patent Triggs June 19, 1973 [5 ATOMIZING BURNER NOZZLE TIP 3,638,865 2 1972 McEneny et a1 239 424 3,093,314 6/1963 Meyer 239/425 [75] invent Lmnal'd Edward Tl'lggsi 3,088,681 5/1963 McCutcheon, Jr. 239 425 x Comh 2,868,587 1/1959 Hegmann 239/425 X [73] Assignee: Combustion Engineering, Inc.,

Windsor Conn Primary ExaminerLloyd L. King Attorney-Eldon H. Luther and John F. Carney [22] Filed: Oct. 15, 1971 1 [21] Appl. No.: 189,671 [57] ABSTRACT A nozzle tip for a liquid fuel atomizing burner is pro- 52 US. Cl. 239/425 vided with an annular aperture Whhi" WhiCh the fuel 51 Int. Cl B05b 7/06 and atomizihg medium are mixed and from which the 58 Field of Search 239/424, 424.5, 425 mixture is discharged as an atomized P The nozzle tip of the invention provides a more effective spray dis- [56] References Cited tribution which requires reduced fuel pressures. The UNITED STATES PATENTS effects of plugging of one or more of the portsthrough which the atomizing medium is conducted are mini- 1,799,551 4 1931 Forney 239 424 mizei 2,090,150 8/1937 Pontius... 239/425 2,174,695 10/1939 Frickie 239/424 12 Claims, 7 Drawing Figures Pmmmmm 3.139.990

INVENTOR. LE'ONARP E; TRIGGS ATTORNEY z ATOMIZING BURNER NOZZLE TIP BACKGROUND OF THE INVENTION Fluid fuel burning apparatus are known in which gaseous fluids, such as steam or air or the like, are utilized to atomize the fuel into a thin spray that is readily permeated by combustion air to insure complete combustion of the fuel. In such apparatus the fuel and atomizing medium are normally introduced at pressures above atmospheric. The fuel pressure is varied between maximum and minimum values depending upon the operational requirements of the burner system while that of the atomizing medium is commonly maintained at a substantially constant value which corresponds to that required to effect fuel atomization over the operating range of fuel pressures.

In one form of atomizing burner, the apparatus is provided with a burner tip having separate groups of passages through which the fuel and atomizing fluid are conducted under suitable pressure. The passages are arranged such that each fuel conducting passage converges with an associated atomizing medium conducting passage. Mixing of the two fluids occurs at the intersection of the two passages and the resultant mixture is conducted to discharge from the burner tip through extensions of one of the passages. The pairs of associated passages are disposed in circumferentially spaced relation about the central axis of the burner tip. The passage extensions through which the atomized mixture passes are disposed so as to be divergent in the direction of discharge to provide a spray conforming generally to the shape of a hollow truncated cone. A fuel burner of this type is described in detail in U. S. Pat. No. 2,414,459.

Fuel burning apparatus of the type under consideration suffer from certain manifest disadvantages. First, because the atomizing medium is maintained at a relatively high pressure, the turndown capability of the burner is limited. Or stated another way, during low load operation of the burner, the fuel must be main tained at pressures higher than that needed to meet steam requirements in order to overcome the pressure of the atomizing medium prevailing in the passage extension through which the fuel must be conducted. This results in retarding the movement of fuel into mixing relation with the atomizing medium. Thus, excess fuel expenditures are realized at low loads thereby reducing the operational efficiency of the burner system.

Second, it is not uncommon for passages to become plugged by foreign substances such as grit. Plugging of a passage which conducts the atomizing medium results in the failure of the fuel which flows through the associated fuel passages to be atomized. This fuel is thus discharged into the furnace in an unatomized state thereby rendering its combustion difficult, and in some cases, even impossible.

It is the purpose of the present invention, therefore, to provide fluid fuel atomizing burner apparatus that is capable of overcoming the above-mentioned deficiencies characteristic of prior art equipment.

SUMMARY OF THE INVENTION According to the present invention, the abovementioned deficiencies in prior art apparatus are avoided by providing a fuel atomizing burner nozzle in which the pairs of convergent passages are replaced by an annular aperture into which the fuel and atomizing medium are discharged and within which mixing of the two fluids occurs prior to the mixture being passed from the nozzle in the form of a spray. The annular aperture is provided withoutwardly divergent wall surfaces to provide improved spray characteristics by means of which the mixture enters the furnace cavity in the form of a thin walled spray of hollow truncated conical form.

The provision of an annular aperture, which is common to all of the fuel and atomizing mediumconducting passages and within which mixing of the two fluids occurs, gives rise to several beneficial results. In apparatus constructed according to the invention the fuel flow will be less afiected by the back pressure produced by the atomizing medium. Thus, lower fuel pressures can be utilized during low load operation of the burner system with a concomitant increase in fuel economy. Additionally, since the "two fluids are mixed in a space that is common to all of the fuel and atomizing medium-conducting passages, the plugging of one or a few of the latter will have a reduced adverse effect upon fuel atomization due to the fact that atomizing medium discharged from. the remaining passages can be utilized to atomize the fuel emanating from the passages that would otherwise be effected.

For a better understanding of the invention, its operating advantages and the specific objects attained by its use, reference should be made to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

A BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation section of an atomizing fuel burner constructed according to the present invention;

FIG. 2 is an enlarged view of a portion of the section illustrated in FIG. 1;

FIG. 3 is an end view taken along line 3-3 of FIG.

FIG. 4 is a section taken along line 4--4 of FIG. 1; FIG. 5 is a partial section taken along line 5-5 of FIG. 1;

FIG. 6 is a section taken along line 6-6 of FIG. 1;

FIG. 7 illustrates a modified form of plug utilized in the burner nozzle tip according to the invention;

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION The burner nozzle according to the present invention is adapted for use in furnaces of conventional construction and is arranged to be operatively connected to sources of fluid fuel and an atomizing medium in a manner that is well known in the art. For the sake of the present description it will be assumed that steam at an elevated pressure is utilized as the atomizing medium. It should be understood, however, that air and other fluid media may be equally well utilized.

Referring to FIG. 1, there is shown a burner assembly 10 comprising a pair of concentrically spaced

tubes

12 and 14 that define an axial flow passage 16 and an annular flow passage 18, the latter being in surrounding relation to the former. The

passages

16 and 18 are each connected to separate sources (not shown) of fluid fuel and steam respectively in any of several well-known manners that are not germaine to the present invention.

The forward ends of the

tubes

12 and 14 are attached to an adapter 20 which is of generally cylindrical configuration. It includes a central, threaded opening 22 into which the leading end of the tube 12 is threadedly secured. The outer tube 14 is shrunk fit to the cylindrical external surface 24 of the adapter. The attachments of the two tubes to the adapter are augmented by

seal welds

26 and 28 that serve to prevent mixture by leakage of the two flowing fluids upstream of the burner nozzle and also to prevent steam or a mixture of steam and fuel from leaking to the atmosphere.

A burner nozzle tip 30 is removably secured to the forward end of the adapter 20, being threadedly secured to an externally threaded extension 32 of the adapter body. The extension 32 is of less diameter than the external surface 24 of the adapter but provides in cooperation with the nozzle tip 30 an internal chamber 34 of somewhat enlarged diameter with which the forward end of the axial tube 12 communicates. A cap 36 having a threaded connection 38 with the adapter is formed with an inwardly extending flange portion 40 engaging a conforming seat on the nozzle tip to anchor the tip upon the adapter in concentric relation to the internal chamber 34 of the extension portion 32. The forward end of the external surface of the cap 36 is provided with a pair of diametrically opposed flats 37 by which to attach a tool for assembling the cap to the adapter. As shown in FIG. 1, the internal surface of the cap 36 is configured to cooperate with the extension 32 to form an annular chamber 42 concentrically spaced from the chamber 34. A plurality of circumferentially spaced bores 44 extend through the body of the adapter 20 to establish fluid communication between the annular flow passage 18 and the chamber 42.

The nozzle tip 30 is machined from a generally cylindrical block of metal, the base of the member containing an internally threaded counterbore 46 that engages an adapter extension 32 and which cooperates therewith to form the chamber 34. The forward end of the tip is recessed to provide mutually communicating bores including an axial chamber-forming bore 48, and intermediate threaded bore 50 of slightly greater diameter to receive a cooperating plug 52 as hereinafter described, and an outer frusto-conical wall 54 forming an outwardly divergent surface. At circumferentially spaced points about its exterior surface, the tip 30 is provided with longitudinally extending recesses 55 which are rectangular in section and which communicate with the annular chamber 42. Radial bores 56 of relatively small diameter extend between the respective recesses 55 and the chamber formed by the axial bore 48. A plurality of circumferentially spaced passages 58, also of relatively small diameter, extend longitudinally through the nozzle tip 30, connecting at oneend with the internal chamber 34 and opening at the other end at the surface of the conical wall 54.

The plug 52 that is received within the threaded bore 50 of the nozzle tip 30 is a machined member containing a cylindrical portion 60 having an external thread for securing the plug within the threaded bore. Rearwardly of the threaded portion 60, the plug is provided with a base portion 62 that is sized to be received within the axial bore 48 and to cooperate therewith to form the fluid-receiving chamber. The forward end of the plug is formed with an outwardly divergent frustoconical surface 64 which, in association with the conical formed wall surface 54, forms an annular aperture 66 which terminates at the forward end of the nozzle tip in an annular discharge opening 68.

As shown, the conical surface 54 of the nozzle tip 30 is formed at a slightly greater angle with respect to the central axis of the assembly than that of the surface 64 on the plug 52. The annular aperture formed thereby is thus provided with opposing walls that are outwardly divergent in the direction of the opening 68. In this way the flow area presented by the aperture can be varied by adjusting the axial position of the plug 52 with respect to the nozzle tip 30.

The plug 52 contains an axial bore 70 extending part way through the member and connecting at its rear end with the chamber defined by the bore 48 in the nozzle tip 30. A plurality of substantially'radial passages 72,

here shown as being six in number, extend from the bore 70 and open at the conical surface 64 in communication with the annular aperture 66. As shown, the passages 72 are preferrably offset slightly forwardly in the upwardly direction to facilitate entry of the fluid into the space formed by the aperture. The loci of the openings of the passages 72 into the aperture 66 are preferrably disposed slightly rearwardly of those of the passages 58 for reasons hereinafter explained.

The forward end of the plug 52 is formed with a dishshaped recess 73 containing a tool-engaging slot 74 for assembling the plug within the nozzle tip 30 and for varying its position therewithin in order to adjust the flow area of the aperture as previously explained.

As shown in FIG. 7, the passages, here indicated as 72', may, alternatively, be oriented in substantially tangential relation with respect to the aperture 64 in order that the fluid flowing through the passage will be imparted with a spinning motion.

In operation, oil or other liquid fuel is supplied to the axial passage 16 formed by the inner tube 12 and flows to the chamber 34 formed by the adapter extension 32. At the same time steam is supplied to the annular passage 18 between the

tubes

12 and 14 and flows through the plurality of bores 44 into the chamber 42 at the forward end of the adapter 20. The oil is conducted through the circumferentially spaced passages 58 in the nozzle tip and is discharged into the annular aperture 66. Steam is conducted from the chamber 42 through the nozzle tip 30 by way of the recesses 55 and radial passages 56, entering the chamber 48 at the rear end of the plug 52. From the chamber 48 the steam passes through the axial bore 70 in the plug 52 and from here is conducted to the aperture 66 through the passages 72. Within the aperture 66 intimate mixing of the steam and oil is effected by means of which the oil is atomized and the mixture discharged through the annular opening 68 into the furnace cavity as a finely atomized spray. Due tothe divergent attitude of the walls defining the aperture 66, the spray is provided with a generally frusto-conicalform which is readily permeated by combustion air within the furnace cavity. By reason of the fact that the openings of the passages 72 into the aperture 66 are disposed slightly rearwardly of those of the passages 58 admission of the oil into the aperture is augmented by the aspiration effect that will be produced by the steam flowing past the openings.

If it is desired to vary the oil flow characteristics of the burner, as for example to increase the rate of fuel flow from the nozzle tip 30, the amount of flow area presented by the aperture 66 can be adjusted. This is accomplished by rotating the plug 52 with respect to the nozzle tip member by means of the application of a tool to the slot 74. In this way, the burner can be readily adjusted to provide the desired operating characteristics.

Burner nozzle adjustments can also be made to the extent of varying the positional relationship that exists between the loci ofthe openings of the

passages

58 and 72 into the annular aperture 66. In FIG. 3, these openings are illustrated as being disposed in mutual angular alignment. In this position the streams of atomizing fluid are in direct alignment with those of the oil entering the annular aperture thereby having the greatest aspirating effect upon the oil exiting the oil passages. It will be obvious that as the angular positional relationship between the respective groups of openings is charged up to a maximum point with the openings 58 being located midway between the openings 72, the aspirating effect will be reduced; however, the steams capability for diffusing the oil will be increased.

in the alternative form of the invention illustrated in FIG. 7 wherein the passages 72 within the plug 52 are disposed in substantial tangential relation with respect to the aperture 66, mixing of the two fluids is enhanced by the rotational motion imparted to the steam entering the aperture.

By providing a burner nozzle arrangement having an annular aperture that is common to all of the fuelconducting and steam-conducting passages several beneficial results are realized. The fuel flow will be less impeded by back pressure created by the flowing steam. This results in the provision of greater fuel turndown ratios by reason of which reduced fuel flows can be utilized during low load operation of the burner systern.

Additionally, because the fuel flowing through each fuel-conducting passage is not dependent for its atomization upon a single associated steam-conducting passage as in prior art apparatus plugging of one-or a few of the steam-conducting passages can be tolerated without materially disrupting the operation of the burner, since fuel from all of the passages is capable of being atomized by steam emanating from the remaining steam-conducting passages.

It will be understood that various changes in the details, materials, and arrangements of parts which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

What is claimed is:

1. Liquid fuel atomizing burner apparatus comprisa. a longitudinally extensive tubular barrel including means defining a pair of separate supply passages extending the length thereof;

b. means for supplying liquid fuel to be atomized to one of said passages;

c. means for supplying fluid atomizing medium to the other of said passages; d. a burner nozzle tip assembly connected to one end of said barrel including:

i. means defining an annular aperture formed by a pair of opposed walls disposed in concentric relation to the central axis of said assembly and terminating in a discharge opening at the forward end thereof,

ii. a first group of passages extending from one of said supply passages and communicating at their other end with said annular aperture, and

iii. a second group of passages extending from the other of said supply passages and communicating with said annular aperture.

2. Apparatus according to claim 1 wherein said opposed walls are disposed in outwardly diverging relation to the central axis of said assembly.

3. Apparatus according to claim 2 wherein the aperture defined by said walls is in the general shape of a frustrum of a cone.

4. Apparatus according to claim 1 wherein said opposed walls are disposed in mutually outwardly divergent relation with respect to one another.

5. Apparatus according to claim 4 wherein said walls are relatively axially movable with respect to one another to vary the flow area defined by said aperture.

6. Apparatus according to claim 1 wherein the supply passages within said barrel are disposed in spaced concentric relation to one another and wherein fuel is conducted through the innermost supply passage and at omizing medium is conducted through the outermost supply passage.

7. Apparatus according to claim 1 wherein said burner nozzle tip assembly includes:

a. a generally cylindrical nozzle body having a rear end portion forming a first fluid chamber in fluid communication with one of said supply passages;

b. an axially disposed bore provided on the forward end of said body, said bore defining a second fluid chamber at its rearwardmost portion in fluid communication with the other of said supply passages, the forward end of said bore being provided with an outwardly divergent, annular wall surface generally in the form of a frustrumi of a cone;

. an axially disposed plug receivable in the bore in said body and including a portion forming an outwardly divergent annular wall surface longitudinally spaced from said similar surface on said nozzle body and cooperating therewith to define an outwardly divergent annular aperture;

d. a plurality of circumferentially spaced passages extending longitudinally through said nozzle body, said passages communicating at one end with said first fluid chamber and at the other end opening into said annular aperture; and l a plurality of passages extending through said plug, said passages communicating at one end with said second fluid chamber and at the other end at circumferentially spaced points with said annular aperture.

8. Apparatus according to claim 7 wherein the annular wall surface on said nozzle body is provided with a slightly greater included angle than that of the annular wall surface on said plug to provide said annular aperture with mutually divergent walls.

9. Apparatus according to claim 8 wherein said plug is threadedly received in said bore and includes means for axially adjusting the portion of the plug with respect to the nozzle body to vary the flow area of said annular aperture.

10. Apparatus according to claim 7 wherein the passages extending through said plug communicate with said annular apertures as points located rearwardly of the points of communication of the apertures that extend through said nozzle body.

11. Apparatus according to claim 7 wherein the passages extending through said plug are disposed in substantial tangential relation to said annular aperture.

12. Apparatus according to claim 1 wherein the passages of at least one group communicate substantially tangentially with said aperture.

Claims

1. Liquid fuel atomizing burner apparatus comprising: a. a longitudinally extensive tubular barrel including means defining a pair of separate supply passages extending the length thereof; b. means for supplying liquid fuel to be atomized to one of said passages; c. means for supplying fluid atomizing medium to the other of said passages; d. a burner nozzle tip assembly connected to one end of said barrel including: i. means defining an annular aperture formed by a pair of opposed walls disposed in concentric relation to the central axis of said assembly and terminating in a discharge opening at the forward end thereof, ii. a first group of passages extending from one of said supply passages and communicating at their other end with said annular aperture, and iii. a second group of passages extending from the other of said supply passages and communicating with said annular aperture.

6. Apparatus according to claim 1 wherein the supply passages within said barrel are disposed in spaced concentric relation to one another and wherein fuel is conducted through the innermost supply passage and atomizing medium is conducted through the outermost supply passage.

7. Apparatus according to claim 1 wherein said burner nozzle tip assembly includes: a. a generally cylindrical nozzle body having a rear end portion forming a first fluid chamber in fluid communication with one of said supply passages; b. an axially disposed bore provided on the forward end of said body, said bore defining a second fluid chamber at its rearwardmost portion in fluid communication with the other of said supply passages, the forward end of said bore being provided with an outwardly divergent, annular wall surface generally in the form of a frustrum of a cone; c. an axially disposed plug receivable in the bore in said body and including a portion forming an outwardly divergent annular wall surface longitudinally spaced from said similar surface on said nozzle body and cooperating therewith to define an outwardly divergent annular aperture; d. a plurality of circumferentially spaced passages extending longitudinally through said nozzle body, said passages communicating at one end with said first fluid chamber and at the other end opening iNto said annular aperture; and e. a plurality of passages extending through said plug, said passages communicating at one end with said second fluid chamber and at the other end at circumferentially spaced points with said annular aperture.