US3329131A - Fuel burner and combination thereof with a fire tube boiler - Google Patents

Description

July 4, 1967 Filed Dec. 14, 1964 WRIGHT R. C. FUEL BURNER AND CO WITH A FIRE MBINATION THEREOF TUBE BOILER 4 Sheets-Sheet 1 INVENTOR W a BY ATTORNEY.

y 4, 1967 R. c. WRIGHT 3,32

FUEL BURNER AND COMBINATION THEREOF WITH A FIRE TUBE BOILER Filed Dec. 14, 1964 4 Sheets-Sheet 5 INVENTOR M0102 BY f ATTORNEY July 4, 1967 .c. WRIGHT 3,329,131

FUEL BURNE ND COMBINAT THEREOF WITH A FIRE TUBE B ER 4 Sheets-Sheet 4 Filed Dec. 14, 1964 INVENTOR QM a 40% ATTORNEY.

United States Patent Oflice 3,329,131 Patented July 4, 1967 3,329,131. FUEL BURNER AND COMBINATION THEREOF WITH A FIRE TUBE BOILER Richard C. Wright, Harrisonburg, Va., assignor to Space Conditioning, Inc., Harrisonburg, Va., a corporation of Maryland Filed Dec. 14, 1964, Ser. No. 418,007 Claims. (Cl. 122-149) This invention relates to a new and improved fuel burner, and to the combination thereof with a specialized fire tube boiler whereby the effectiveness of each is enhanced as the result of the combination.

More specifically the invention relates to an improvement in the burner disclosed in my U.S. Patent No. 3,071,181, issued Jan. 1, 1963 which renders the burner particularly effective in the specialized boiler.

Horizontal fire tube boilers of the type generally referred to as Scotch Marine boilers are well known in the art. However, in the prior boilers, the tubes are of relatively large inside cross sectional areas in relation to their circumference. It was believed that this large ratio of cross sectional area to circumference was necessary unless the boilers were equipped with force draft. It was also believed that if the cross sectional areas of the tubes in relation to their circumferences were reduced for increasing the effective heat exchange per unit of tube surface, the frictional losses of the flue gases flowing through the smaller tubes would be too great to be overcome by the available draft from a conventional chimney or stack, and thereby a reduction in overall heating efficiency would result.

Accordingly, a problem is presented of maintaining a smaller ratio of internal cross sectional areas of the tubes in square inches to circumferences in inches for obtaining more eflicient heat exchange while at the same time assuring an adequate flow of burning gases and products of combustion through the tubes to take advantage of the smaller ratio.

The solution requires not only a change in tube design, but also a change in burner design and the manner of circulating the combustible gases. The problem is particularly pronounced in boilers having a minimum mass flow rate of about 1,000 pounds of flue gas per hour per square foot of tube cross sectional area. Below such a rate, the overall coeificient of heat transfer falls off quite rapidly.

It is true that high rates of heat exchange can be obtained in some fire tube boilers employing forced drafts, but such is undesirable in many instances, particularly in the characteristics of the boiler and burner during start up and before the equipment has become properly heated.

In accordance with the present invention, an induced draft system is employed wherein the air for combustion is induced through the burner by a fan having a constant discharge volume. The volume of air induced through the burner, and thereby into the combustion chamber, remains roughly uniform. This is particularly advantageous in connection with the present burner, inasmuch as the eflective mass flow rate of air required during starting period of the burner and boiler, while the burner, the combustion chamber, and the fuel are cold or unheated, is higher than after the Warm up period. However, the nozzle of the burner inherently delivers more fuel during the cold start up period than after the equipment has warmed up. As a result of the constant volume fan induction, a larger mass flow rate is present and provides adequate air for the burning of the larger amount of fuel exactly when required during start up. Also, for like reason, a smaller mass flow rate provides the lesser amount of air required by the warmed up equipment.

The structure is one in which a special induced draft burner, a fire tube boiler having heat exchange tubes with a low ratio of cross sectional area in square inches to circumference in inches, and a fan of constant discharge volume, all cooperate to provide greater overall operation and heating efliciency.

The fuel is supplied by the burner in a conical pattern expanding toward a combustion chamber. The exhaust fan is of the blower type and is arranged with its inlet adjacent to the outlets of the fire tubes of the boiler for withdrawing the flue gases therefrom and discharging them to the atmosphere. The fan has a capacity such that it withdraws gases at a sufiicient rate to cause air to be induced in adequate amounts to the conical sheet of fuel and into the combustion chamber to assure effective combustion of the fuel while maintaining a high flow rate-for example, a minimum of 1,000 pounds of flue gases per hour per square foot of tube area, with the above mentioned low ratio of area of tube cross section in square inches to circumference of the tube in inches.

A more specific object resides in the modification of the burner, particularly the air control shell or cone which, in many cases is necessary for regulating the air velocity for eflective operation.

Various objects and advantages will become apparent from the following description .wherein reference is made to the drawings in which:

FIG. 1 is a top plan view of the boiler and burner combination embodying the principles of the present invention;

FIG. 2 is a vertical longitudinal sectional view through the boiler burner taken on a line 22 in FIG. 1, parts thereof being shown in elevation for clearness in illustration;

FIG. 3 is a right end elevation of the structure illustrated in FIG. 2;

FIG. 4 is a left end elevation of the structure illustrated in FIG. 2;

FIG. 5 is a rear elevation of the structure illustrated in FIGURES 1 through 4.

FIG. 6 is an enlarged fragmentary side elevation of the burner and its mounting, used in the present invention, part thereof being shown in section for clearness in illustration;

FIG. 7 is a fragmentary left end elevation of the structure illustrated in FIG. 6 and viewed as indicated by the the line 7-7 in FIG: 6; and

FIG. 8 is a fragmentary vertical cross sectional View taken on line 88 in FIG. 6.

Referring to the drawings, the invention is shown as incorporated in a fire tube boiler including a water jacket 1, comprising the usual front wall 2, rear wall 3, side walls 4, top wall 5. The boiler is provided at the top with the usual steam outlet pipe 6, and at the bottom with a suitable filling pipe 7. The boiler has a conventional access opening 8 which can receive other equipment, such as hot water heating coils, and which if not so used is closed by cover plate 9.

Mounted in the lower part of the jacket 1 in spaced relation to the front, bottom, and side walls thereof, is a combustion chamber 10 which, in the form illustrated, is cylindrical and is disposed with its axis horizontal. The combustion chamber 10 has a forward wall 11 spaced rearwardly from the forward wall 2 of the jacket in order to permit water to flow therebetween. The forward wall 11 is provided with an inlet opening 12 and a sleeve 13 is connected in sealed relation to the forward wall 11 about the periphery of the opening 12. The sleeve 13 extends from the forward wall 11 through a suitable opening in the front wall 2 and outwardly forwardly from the front wall 2. The periphery of the sleeve 13 is in sealed relation to the wall 2.

The combustion chamber 10 is open at the rear and is in communication with a coextensive opening in the rear wall 3 of the jacket. Mounted on the rear of the wall 3 is a reversing compartment 15. In the form illustrated, the compartment is in the form of a frame having side walls 16, a top wall 17, and a bottom wall 18. These walls are connected in sealed relation to the rear wall 3 at the forward edges. The frame is closed at the rear by a suitable cover plate 19 which is bolted thereto.

The compartment 15 extends from below the lowest level of the combustion chamber upwardly to the location above the upper level of the uppermost fire tubes of the boiler. It receives burning gases from the rear of the combustion chamber and directs them forwardly into the boiler fire tubes.

In the boiler illustrated, fire tubes 20 are provided and are arranged in an upper tier 21 and a lower tier 22. The tiers are spaced apart from each other and the tubes 20 of each tier are arranged in laterally spaced relation to each other in a row in their tier. The tubes open front and rear through the walls 2 and 3, respectively, and are in peripherally sealed relation to the front wall 2 and the rear wall 3. Thus water can circulate freely throughout the jacket, around the combustion chamber and tubes 20, and to a level above the tubes. A suitable bafl le 23 may be provided in the boiler, if desired, to prevent the surging of water during filling.

The tubes 20 have a relatively low ratio of internal cross sectional area in square inches to circumference in inches, preferably a ratio of from 1:3 to 1:8. This may be obtained by using cylindrical tubes as low as one inch in diameter. Preferably, however, the low ratio is obtained by using tubes of elongated internal cross sections which are sharply curvilinear and concave inwardly at the ends of the cross section, and are flattened at the sides thereof. By making the tubes out-of-round, the ratio of the cross sectional areas to its peripheries can be reduced readily to that desired while permitting a better flow of gases therethrough.

Mounted on the wall 2 above the level of the sleeve 13 is a box structure providing a forward discharge compartment 25. The compartment comprises a top wall 26, a bottom wall 27, side walls 28, and a front wall 29. The edges of these walls are in sealed relation to the wall 2 so to prevent the escape of products of combustion therebetween. The forward discharge compartment 25 extends from a level below the level of the bottom of the lowermost tube 20, to a level above the top of the uppermost tube 20. As a result burning gases and products of combustion can flow from the chamber 10, through the compartment 15, wherein they are turned about and caused to pass through the tubes 20, and then into compartment 25.

The front wall 29 of the compartment 25 has a discharge opening 30. A fan or blower housing 31 is connected to the front wall 29 and has an inlet coaxial with, and coextensive with, the opening 30-.

The housing 31 is in the form of a scroll which expands towards its discharge opening 33. A rotary impeller 34 is mounted in the housing 31 and is driven by a motor 36. The impeller 34 functions to withdraw products of combusion from the compartment 25 and discharge them to the atmosphere. The fan has a capacity such that it withdraws gases at a suflicient rate to induce air adequate for combustion while maintaining a high flow rate. The fan has a constant discharge volume so that the volume of air induced remains substantially constant. Consequently the effective mass flow rate required during starting and warm up of the equipment is higher than after the equipment has warmed up. However, the burner delivers more fuel during the warm up period. Hence the larger mass flow rate tends to compensate for the variation in the fuel discharge by the burner to assure more nearly the optimum balance of air and fuel at both periods of operation.

In the case where fuel oil is used as the fluid fuel, as illustrated, a suitable pump 37 is connected to the motor 36 and driven thereby. The pump 37 has an inlet pipe 38 connected to a suitable source of fuel and a discharge or pressure line 39 leading to the burner of the boiler.

It is apparent that upon operation of the blower or fan, negative pressure is created in the combustion chamber by forcible withdrawal of the products of combustion from the compartment 25, tubes 20, compartment 15, and combustion chamber 10. This withdrawal, as will later be described, is sufficient to induce a flow of air into the burner in an amount adequate to sustain combustion of the fuel supplied by the burner.

The burner itself is best illustrated in FIGURES 6 through 8. It comprises outer shell 40 which fits in coaxial relation in the sleeve 13. The shell 40 has a radial flange 41 which is bolted firmly to the outer end of the sleeve 13. The shell 40 has an open discharge end 42 which, in the mounted position of the shell in the sleeve 13, protrudes a short distance into the chamber 10. The outer end 43 of the shell 40 is closed by a suitable cap 44 and is accessible at the exterior of the boiler jacket.

A fuel discharge nozzle 45 is arranged in the shell 40 in coaxial and axially spaced relation thereto. The nozzle is spaced from the discharge end 42 thereof toward the outer end 43. The nozzle 45 is supported on a spider 46 and is connected to the fuel feed line 39. Suitable electrodes 47 are provided for lighting the fuel in the conventional manner.

Between the discharge end of the nozzle and the discharge end 42 of the sleeve 40 is an air directing means comprising a frustoconical air directing shell 50. The shell 50 is disposed with its larger base facing toward the discharge end 42, of the sleeve 40 and its smaller base adjacent to, but spaced in a direction toward the discharge end 42 of the sleeve 40 from the nozzle 45. The peripheral edge of the larger base of the shell 50 fits the peripheral wall of the sleeve 40. The shell 50 is supported in the sleeve 40 in coaxial relation to the sleeve 40 and nozzle 45 by the connection of the edge of its larger base to the sleeve wall.

The smaller base of the shell 50 is provided with a circular opening 51 coaxial with the smaller base and with the nozzle 45. The nozzle 45 is one which, as mentioned,

discharges fuel in a conical pattern extending in the direction toward the discharge end 42 of the sleeve 40. The size of the opening 51 and its position relative to the discharge end of the nozzle 45 are such that the conical sheet or pattern of fuel issuing from the nozzle 45 passes through the opening 51 in radially inwardly spaced relation to, but close proximity to, periphery of the opening 51.

The side wall of the shell 50 is provided with a plurality of cricumferentially spaced air slots 52 which are elongated endwise of the side wall. The slots 52 are spaced apart laterally from each other circumferentially of the shell 50. The side wall of the shell 50 is provided at its inner face with a plurality of directional deflecting vanes 53. The vanes 53 are coextensive lengthwise of the side wall with the slots 52. Preferably the vanes 53 are connected to the side wall, each along the one of its margins at a location adjacent one lateral edge of the associated slot. The vanes 53 may be formed by slitting along some of the boundaries of areas of the metal where the slots are to be formed, leaving the areas connected along one edge of the boundary, and bending the metal of the area inwardly. The vanes 53 are adjacent to the slots 52, respectively, and have deflecting surfaces, respectively which lengthwise extend endwise of the shell and sidewise extend inwardly and circumferentially at an inclination to the side wall.

In order to admit induced air to the burner, the sleeve 40 is provided near its outer end with a plurality of circumferentia-lly spaced air inlet ports 54. Outside air is induced into the shell through the ports 54 due to the action of the burner and of the fan 34.

The burner structure thus far described in essentially that of the above patent. However, it has been found that with the present boiler structure, better results are obtained if air control ports 56 are provided in the shell 50 adjacent the junction of the edge of its larger base with the sidewall of the sleeve 40. As illustrated in FIGS. 5 through 7, a plurality of such ports 56 are provided. These ports are elongated and extend endwise circumferentially of the shell and are in endwise spaced relation to each other. They are arranged so that each port 56 lies between two radial planes through the axis of the shell 50 intersecting two adjacent deflecting vanes 53. Each port 56, is as mentioned, elongated circumferentially of the shell 50 and is relatively shallow relative to the axial length of the shell 50. Each port 56 terminate endwise, circumferentially of the shell 50, between and in spaced relation to the two adjacent planes between which it lies. These air control ports 56 may be provided by small cutouts in the peripheral margin of the shell '50 adjacent to its larger base. Preferably the innermost limits of ports 56 are spaced outwardly from the axis of the shell a distance greater than the outermost ends of the vanes 53.

It has been found that with the structure described, particularly with this specific burner modification, fan, tube configuration, and low ratio of cross sectional area to circumference of the tubes, at very high efficiency can be obtained.

While it is possible to use in the present structure the burner as shown in the above patent, such is not as effective as the burner in its modified form. The exact contribution of each part of the equipment and its affect on the operations of the other parts, such as the modified burner, a blower causing induced air, and the tubes of a specific cross sectional are-a to circumference ratio, is not fully understood, but tests indicate that the combination is superior in operation. The structure is useful for both gaseous and liquid fuels.

Having thus described my invention, I claim:

1. A fuel burner comprising a sleeve open at one end and closed at the other end,

a fuel discharge nozzle in and coaxial with the sleeve in spaced relation to said inner end and adapted to discharge fuel in a conical pattern which expands toward said one end when fuel under pressure is supplied to the nozzle,

a fuel supply line leading from a source of fuel under pressure and connected to the nozzle,

air inlet port means in the sleeve and spaced between the nozzle and said other end,

a generally frusto-conical air control shell, open at its larger base and having a central inlet opening at its smaller base, said control shell being disposed in the sleeve between the nozzle and said one end in coaxial relation to the nozzle and With its larger base spaced from the nozzle toward said one end and its smaller base disposed between the larger base and the nozzle and spaced from the nozzle toward said one end a distance such that the conical fuel pattern passes through said inlet opening in closely and inwardly relation to the circumferential wall of the opening,

said shell having a series of air slots in its side wall elongated endwise thereof and disposed in laterally spaced relation circumferentially thereof,

air directing wings in the interior of the shell adjacent the slots, respectively, and having deflecting faces, respectively, extending endwise of the shell and sloping inwardly and circumferentially relative of the side wall of the shell for causing air entering through the slots to whirl about the nozzle axis,

said shell, at its larger base, being connected to the sleeve for substantially blocking the passage of air between the larger base of the shell and the sleeve,

and said shell having air control ports therein at the juncture of its larger base with the sleeve, said air control ports being spaced from each other circumferentially of the shell, and each air control port being elongated circumferentially of the shell and shallow, relative to its length, endwise of the shell.

2. A burner according to claim 1 wherein said air control ports are defined by the wall of the sleeve and shallow cut-outs in the wall of the shell.

3. A burner according to claim 1 wherein the air control ports are disposed, circumferentially and radially, of the shell, in offset relation to the air slots, one between each two adjacent slots.

4. A burner according to claim 3 wherein each air control port lies between, and terminates in spaced relation to, radial planes through two adjacent slots.

5. A burner according to claim 1 wherein the edges of the shell defining the edge portions, farthest from the larger base are closer to said larger base than the nearest ends of the slot.

6. A fuel burning fire tube boiler and burner combination comprising a hollow boiler body having a combination chamber therein, said chamber having an inlet at one end and an outlet at the other end;

a bank of fire tubes in the body, said tubes having a low ratio of cross sectional area in square inches to circumference in inches, with resultant high resistance to flow;

said body having one compartment connecting the outlet of the combustion chamber with one end of the bank of tubes and having a discharge compartment connected with the other end of the bank of tubes;

burner means for introducing fuel under pressure into the combustion chamber inlet;

said body having air inlet port means for admitting outside air into the chamber by induction;

blower means of substantially constant volumetric discharge and having an outlet discharging to the atmosphere and having an inlet connected to the discharge compartment and arranged to withdraw gaseous products from the discharge compartment at a suflicient rate and in a sufficient volume to induce adequate air at a high flow rate through said inlet port means to the burner means and into the combustion chamber to effect combustion of the fuel discharged by the burner means;

said burner means comprising a sleeve which extends from the exterior of the chamber into the chamber and is open at its inner end for discharging into the chamber;

a fuel discharge nozzle in, and coaxial with, the sleeve and in spaced relation to said inner end of the sleeve and adapted to discharge fuel in a conical pattern which expands from the nozzle toward said inner end when fuel under pressure is supplied to the nozzle;

a generally frusto-conical air control shell, open at its larger base and having a central inlet opening at its smaller base, disposed in the sleeve between the nozzle and said inner end of the sleeve in coaxial relation with the nozzle and with its larger base spaced from the nozzle toward said inner end and its smaller base disposed between the larger base and the nozzle and spaced from the nozzle toward said inner end a distance such that the conical fuel pattern passes through said inlet opening in closely inwardly spaced relation to the circumferential wall of the opening;

said shell having a series of air slots in its side Wall elongated endwise thereof and disposed in laterally spaced relation circumferentially thereof;

air directing wings in the interior of the shell adjacent the slots, respectively, and having deflecting faces, respectively, extending endwise of the shell and sloping inwardly circumferentially relative of the side wall of the shell for causing air entering through the slots to whirl about the nozzle axis;

sleeve for substantially blocking the passage of air between the larger base of the shell and the sleeve;

a fuel supply line leading from a source of fuel under pressure and connected to the nozzle;

said air inlet port means being air inlet ports in a portion of the sleeve at the exterior of the chamber; and

said shell having air control ports therein at the juncture of its larger base with the sleeve, said air control ports being spaced from each other circumferentially of the shell and each air control port being elongated circumferentially of the shell and shallow,

- relative to its length, endwise of the shell.

7. A structure according to claim 6 wherein the air control ports terminate, in a direction endwise of the shell, closer to the larger base of the shell than do those ends of the slots which are nearest to the larger base.

8. A structure according to claim 6 wherein said air 8 control ports are defined by the wall of the sleeve and shallow cut-outs in the wall of the shell.

9. A structure according to claim 6 wherein the air control ports are disposed, circumferentially and radially, of the shell, in otfset relation to the air slots, one between each two adjacent slots.

10. A structure according to claim 9 wherein each air control port lies between, and terminates in spaced relation to, radial planes through two adjacent slots.

References Cited UNITED STATES PATENTS 2,053,003 9/1936 Koeln 1581.5 2,502,071 3/1950 Baumann et al l22--149 2,888,910 6/1959 Loebel 122-449 3,071,181 1/1963 Wright l58-1.5 X

CHARLES J. MYHRE, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,329,131 July 4, 1967 Richard C. Wright It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, lines 58 and S9, for "combusion" read combustion column 4, line 43, for "extending" read expanding column 5, line 58, after "inwardly" insert spaced column 6, lines 19 and 20, for "combination" read combustion Signed and sealed this 1st day of October 1968.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims (1)

1. 6. A FUEL BURNING FIRE TUBE BOILER AND BURNER COMBINATION COMPRISING A HOLLOW BOILER BODY HAVING A COMBINATION CHAMBER THEREIN, SAID CHAMBER HAVING AN INLET AT ONE END AND AN OUTLET AT THE OTHER END; A BANK OF FIRE TUBES IN THE BODY, SAID TUBES HAVING A LOW RATIO OF CROSS SECTIONAL AREA IN SQUARE INCHES TO CIRCUMFERENCE IN INCHES, WITH RESULTANT HIGH RESISTANCE TO FLOW; SAID BODY HAVING ONE COMPARTMENT CONNECTING THE OUTLET OF THE COMBUSTION CHAMBER WITH ONE END OF THE BANK OF TUBES AND HAVING A DICHARGE COMPARTMENT CONNECTED WITH THE OTHER END OF THE BANK OF TUBES; BURNER MEANS FOR INTRODUCING FUEL UNDER PRESSURE INTO THE COMBUSTION CHAMBER INLET; SAID BODY HAVING AIR INLET PORT MEANS FOR ADMITTING OUTSIDE AIR INTO THE CHAMBER BY INDUCTION; BLOWER MEANS OF SUBSTANTIALLY CONTANT VOLUMETRIC DISCHARGE AND HAVING AN OUTLET DISCHARGING TO THE ATMOSPHERE AND HAVING AN INLET CONNECTED TO THE DISCHARGE COMPARTMENT AND ARRANGED TO WITHDRAW GASEOUS PRODUCTS FROM THE DISCHARGE COMPARTMENT AT A SUFFICIENT RATE AND IN A SUFFICIENT VOLUME TO INDUCE ADEQUATE AIR AT A HIGH FLOW RATE THROUGH SAID INLET PORT MEANS TO THE BURNER MEANS AND INTO THE COMBUSTION CHAMBER TO EFFECT COMBUSTION OF THE FUEL DISCHARGE BY THE BURNER MEANS; SAID BURNER MEANS COMPRISING A SLEEVE WHICH EXTENDS FROM THE EXTERIOR OF THE CHAMBER INTO THE CHAMBER AND IS OPEN AT ITS INNER END FOR DISCHARGING INTO THE CHAMBER; A FUEL DISCHARGE NOZZLE IN, AND COAXIAL WITH, THE SLEEVE AND IN SPACED RELATION TO SAID INNER END OF THE SLEEVE AND ADAPTED TO DISCHARGE FUEL IN A CONCIAL PATTERN WHICH EXPANDS FROM THE NOZZLE TOWARD SAID INNER END WHEN FUEL UNDER PRESSURE IS SUPPLIED TO THE NOZZLE; A GENERALLY FRUSTO-CONCIAL AIR CONTROL SHELL, OPEN AT ITS LARGER BASE AND HAVING A CENTRAL INLET OPENING AT ITS SMALLER BASE, DISPOSED IN THE SLEEVE BETWEEN THE NOZZLE AND SAID INNER END OF THE SLEEVE IN COAXIAL RELATION WITH THE NOZZLE AND WITH ITS LARGER BASE SPACED FROM THE NOZZLE TOWARD SAID INNER END AND ITS SMALLER BASE DISPOSED BETWEEN THE LARGER BASE AND THE NOZZLE AND SPACED FROM THE NOZZLE TOWARD SAID INNER END A DISTANCE SUCH THAT THE CONCIAL FUEL PATTERN PASSES THROUGH SAID INLET OPENING IN CLOSELY INWARDLY SPACED RELATION TO THE CIRCUMFERENTIAL WALL OF THE OPENING; SAID SHELL HAVING A SERIES OF AIR SLOTS IN ITS SIDE WALL ELONGATED ENDWISE THEREOF AND DISPOSED IN LATERALLY SPACED RELATION CIRCUMFERENTIALLY THEREOF;

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