US3213919A

US3213919A - Nozzle apparatus for burning fuel

Info

Publication number: US3213919A
Application number: US194641A
Authority: US
Inventors: Calzolari Roberto
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-05-14
Filing date: 1962-05-14
Publication date: 1965-10-26
Anticipated expiration: 1982-10-26

Description

R. CALZOLARI NOZZLE APPARATUS FOR BURNING FUEL Oct. 26, 1965 2 Sheets-Sheet 1 Filed May 14, 1962 INVENTOR. Foberfo 'Ca/zo/ari W L Oct. 26, 1965 R. CALZOLARI 3,213,919

NOZZLE APPARATUS FOR BURNING FUEL Filed May 14, 1962 2 Sheets-Sheet 2 INVENTOR. Ro BERTO CALZOLARI WYQM AT TOR NEYS United States Patent F 3,213,919 NOZZLE APPARATUS FOR BURNING FUEL Roberto Calzolari, Via Serpieri 8, Rome, Italy Filed May 14, 1962, Ser. No. 194,641 5 Claims. (Cl. 158-76) This is a continuation-in-part of my prior application Serial No. 796,526, filed March 2, 1959, and now abandoned.

This invention relates to an improved fuel burner for burning fuel which can be employed to particular advantage in kilns.

Improved heat transfer characteristics are particularly diflicult to obtain in existing furnaces without substantially altering the existing structure. This is particularly true for furnaces, such as kilns, operating at comparatively low temperatures, wherein substantial improvement in heat transfer efficiency can only be brought about by improving convection coefficients. However, by altering t-he characteristics of a flame which heats the kiln, it is possible to substantially increase the amount of heat transferred by radiation from the flame and, consequently, improve the efliciency of the kiln. Radiation from a flame is affected by its temperature, emission factor, and radiant surface. An increased flame temperature will increase radiation and can be accomplished by providing rapid and thorough mixing of the fuel and air to obtain faster, more intense combustion. A higher emission factor will increase radiation and can be achieved with a luminous flame produced by relatively slow mixing of the fuel with an insuflicient amount of air. Larger radiant surfaces will increase radiation and can be achieved by providing a hollow conical flame which enables a maximum area to be obtained for a given volume of fuel and air.

The new burner for combustion according to the invention increases flame radiation by all three of the above approaches. Rapid mixing and intense burning is produced in portions of the flame to produce intense heat and high temperatures. Slower mixing of the fuel with an insuflicient amount of air is established in other portions of the flame to produce luminescence. A much longer, conical, hollow flame than those heretofore known is also produced to provide a larger and more effective radiant surface. The expression hollow flame as used herein denotes a flame which is defined between two co-axial conical surfaces which have slightly different angles of generation, with the lateral cross section of the flame constituting an annulus.

The burner according to the invention produces a flame which is shaped between a conventional solid flame and a conventional shallow, conical flame produced by whirling burning products of combustion. In accomplishing this, the new flame also combines high heat intensity and high luminescence, either of which can be obtained singularly with the first flame, with the large surface area of the second flame. The improved flame also corresponds more closely to the shape of the kiln or other chamber into which the flame is emitted and can be directed closer to the object or material intended to be heated than can be the shallow, whirling flame.

The new flame is produced by dividing fuel, preferably oil, into a number of entirely separate streams which are given a slight twist to produce both an axial and a tangential component of movement. The individual streams are then forced through an annular, tapered passage of decreasing dimensions to substantially increase the axial velocity without substantially affecting the tangential velocity. The annular passage causes the fuel passing therethrough to rotate more rapidly near the inner surface of the passage than near the outer surface 3,213,919 Patented 0st. 26, 1965 with the result that the fuel particles in each stream tend to be separated but, nevertheless, the individual streams do not initially tend to mix together. The size and number of the streams are proportioned in such a manner that the particles produce a vapor of small drops which vary in diameter but are uniformly distributed within the streams and within a space defined between two coaxial conical surfaces outside the burner, after the streams are forced through the annular passage. By varying the number of streams and their tangential components within certain limits, it is possible to adapt the shape of the flame to that of the particular enclosed space in which it is utilized.

Both an inner cylindrical stream and an annular outer stream of primary air are directed concentrically around the paths of the fuel oil streams. The inner primary air stream is caused to travel at lower velocity than the outer primary air stream so that mixing of the fuel and inner primary air is relatively slower. Further, the quantity of air in the inner stream is insuflicient to produce complete combustion. Consequently, a long, luminous flame with high emissivity is produced initially. Rapid mixing of the outer, annular primary air stream and unburned portions of the fuel streams subsequently occurs, resulting in rapid and intense burning and high heat intensity. The remaining portions of the fuel streams finally are burned with secondary, heated air in the kiln. The quantity of air in the inner primary air stream can also be varied to control the extent of initial combustion and thereby control the effective length of the flame.

It is, therefore, a principal object of the invention to provide a flame capable of more rapidly transmitting heat, principally by radiation.

Another object of the invention is to provide a flame having high heat intensity, high emissivity, and a large surface area.

Still another object of the invention is to provide a conical flame which is longer and more narrow than those heretofore known.

A further object of the invention is to provide a burner which is capable of producing a flame having the characteristics and advantages discussed above.

Still a further object of the invention is to provide a burner from which fuel is emitted in a plurality of separate streams defining a cone, with primary air supplied therearound in cylindrical and annular paths, and with means for varying the quantity of air in the cylindrical stream to thereby vary flame length.

Other objects and advantages of the invention will be apparent from the following detailed description of a preferred embodiment thereof, reference being made to the accompanying drawing, in which:

FIG. 1 is a view in cross section showing a burner according to the invention, including means for controlling the flow of primary air;

FIG. 2 is a greatly enlarged view in cross section showing the details of the burner nozzle; and

FIG. 3 is a further enlarged, fragmentary view, with parts broken away and with parts in cross section, of a nozzle similar to that of FIG. 2.

Referring more particularly to FIGURE 1, a burner according to the invention is indicated at 10 and includes a duct 12 and a relatively low pressure blower 14 of conventional design. A venturi tube 16 is concentrically located in the duct 12 by means of spiders 18 and a fuel line 20 extends axially through the tube 16 and through the back of the blower housing 14, being supported by a hangar 22 afiixed to an upper portion of the venturi tube 16. The line 20 is connected to any suitable source of fuel oil. A double conical valve member 24 consisting of two

cones

26 and 28 and a sleeve 30 is slidably supported on the fuel line 20 and extends through the back of the blower housing 14 to a flange or handle 32. The surface of the cone 28 has the same angle of generation as the inner surface of the entrance of the venturi tube 16 to completely close off the entrance when the member 24 is slid to its forward position. Axial movement of the member 24 varies the annular entrance of the venturi tube 16 and thus varies the amount of air flowing through the venturi tube 16 and to some extent the amount of air flowing through an annulus 17 between the tube 16 and the duct 12.

A nozzle 34 located at the front end of the fuel line 20 is shown in detail in FIG. 2 and includes a threaded connector 36 which connects a housing 38 to the fuel line 20. The connector is screwed into a recess 40 in the housing 38, against a gasket 42, and has a passage 44 aligned with a passage 46 in a core 48. A flange 50 concentrically locates the rear portion of the core 48 with respect to a cylindrical inner surface 52 of the housing 38. A small shank 54 forming part of the core 48 connects the flange 50 with a segment 56 which has a plurality of helical ridges 58 thereon forming helical channels 60 therebetween. At the downstream end of the segment 56 is a blunt cone 62 which extends into a conical recess 64 of a nozzle member 66. The cone 62 has a slightly steeper angle of taper than the conical recess 64 which thereby form a conical, annular passage decreasing in both diameter and thickness from the segment 56 to an orifice 68 at the extremity of the member 66. A flange 70 supports the member 66 concentrically with respect to the inner surface 52 of the housing 38 and positions the orifice 68 and the recess 64 concentrically with respect to the cone 62. A gasket 72 is nested between the flange 70 of the member 66 and a flange 74 of the housing 38 to maintain a tight connection therebetween. A spacer 76 properly longitudinally spaces the cone 62 of the core 48 from the conical recess 64 of the nozzle member 66 and also defines an annular manifold 78 between its inner surface and the shank 54. A plurality of ports 80 connect the annular manifold 78 With the passage 46.

Fuel from the line is supplied under pressure through the passage 44, into the passage 46, through the ports 80, and into the annular manifold 78. From here, it is divided into separate streams by the separate helical channels 60 formed between the helical ridges 58, the segment 56, and the inner surface of the spacer 76. The streams then flow through the tapered, narrowing passage between the cone 62 and the conical recess 64 where the axial velocity is greatly increased but the tangential velocity is affected to a much lesser extent. Those portions of each stream near the inner surface of the conical passage tend to flow more rapidly than those portions near the outer surface with the result that the particles in each stream tend to be pulled apart but still stay within their respective streams. This differential effect on the various particles produces a predisposition to atomization which takes place rapidly when the high velocity streams impact the relatively stationary air outside the orifice 68. The streams are emitted from the orifice 68 in diverging paths producing an overall conical shape and continue outwardly until they meet the primary air.

In accordance with the present invention, the primary air is supplied in an inner cylindrical stream, indicated by the short arrows in FIG. 1, through the tube 16, and in an outer annular stream indicated by the long arrows, from the annulus 17 between the tube 16 and the duct 12. The air for both of these primary air streams is supplied by the blower 14, and the relationships between the entrance and discharge ends of the primary air passages are so made that the air in the duct 12 is expanded down to a lower pressure and velocity while the air from the annulus 12 is discharged at full pressure and high velocity.

Burning of the fuel streams first occurs at the intersection of the fuel streams and the inner, primary air stream, and this burning is relatively slow because the velocity of the primary air is relatively low and the quantity of air in this stream is insufficient to complete the combustion of even a major portion of the fuel. Therefore, a long luminous flame is produced initially. However, at the area of intersection of the fuel streams and the outer annular primary air stream, more rapid and intense burning occurs because of rapid mixing of the fuel with the high velocity outer annular primary air stream. Completion of the combustion of the fuel streams takes place within the kiln with secondary air which is induced in a heated condition.

The particular form of emission of the fuel from the nozzle 34 enables the flame to have a long, hollow, conical shape, much. longer and more narrow than a conventional whirling flame with a relatively shallow angle and a relatively short length. The new flame enables a substantial radiating surface to be obtained and yet enables the burning gases to be directed closer to the objects or materials to be heated. Thus, in most instances, the source of radiation is closer to the object or materials than is a conventional whirling flame. Furthermore, the length of the new flame can be easily changed by varying the quantity of air contained in the inner primary air stream and admitted through the tube 16 and thereby control the extent and rate of initial combustion.

The quantity of air admitted in the inner primary air stream can be changed by changing the position of the member 24 on its supporting pipe 20. If the member is moved back to increase the volume of air in the inner stream the flame becomes shorter, and if the member is moved forwardly to reduce the volume of air in the inner stream by throttling the intake end of the passage formed by the tube 16 the length of the flame will increase.

A slightly modified nozzle 82 is shown in FIG. 3. This nozzle is substantially similar to that of FIGS. 1 and 2 except that a core 84 has ridges extending in the opposite direction to those of FIG. 2 and a cone 86 has a concave, blunt end which is preferred to a truly truncated one. A nozzle member 88 also differs slightly from the member 66 because the member 88 has a shallow end recess 90.

For both the

nozzles

34 and 82, the angle A of the blunt cone will vary from 15 to 21 while the angle B of the recess 64 will vary from 19 to 25, being more than the angle A of the cone. In addition, the ratio of the product of the diameter D of the large end of the recess and the diameter E of the small end of the cone to the product of the diameter C of the large end of the cone and the diameter F of the small end of the recess will exceed 1.0 and will not exceed 1.36. Expressed as an equation:

The value for K will depend on the metal employed in the nozzle elements, the surface obtained on the cone, and, to some extent, on the viscosity of fuel oil used. Fuel pressures employed vary from 13 to 40 kilograms per square centimeter.

In practice, the required nozzle area is determined by:

is first calculated, based on output desired and pressures available. The diameters C and D can then be found and the length of the cone and recess subsequently determined so that the angles of them will fall within the aforementioned ranges.

The recess in the blunt end of the cone has a radius R equal to 1.5 F.

While the blunt end of the cone 86 is recessed, and the blunt end of the cone 62 is shown as truncated, other configurations of the blunt end may be used. It is important that the surface of the cone deviate inwardly at a point immediately upstream of the orifice 68 so that the stream of fuel oil separates from the surface of the cone near the beginning of the deviation.

While the above discussion and accompanying drawings have discussed and illustrated only one specific form of the invention, it is to be understood that this form has been shown for purposes of illustration and is not employed in a limiting sense. Consequently, it is to be understood that various modifications can be embodied in the invention without departing from the scope of the claims appended hereto.

What I claim is:

1. A nozzle for a liquid fuel burner for producing a high temperature flame with high emissivity and a large radiant surface, said nozzle including a nozzle member having a conical recess at a downstream end thereof, the included angle of said recess being constant throughout the length of said recess and ranging from 19 to 25, a core having a truncated cone forming an angle which is constant throughout the length of said cone and ranges from 15 to 21, said cone extending into said recess to form an annular passage decreasing in diameter at a uniform rate, said member forming a cylindrical passage located immediately beyond a smaller, blunt end of said cone and co-axial therewith, means for maintaining said member and said core in fixed, spaced relationship, a plurality of helical ridges on said core forming a plurality of separated helical passages with a portion of said spacing means, means forming a manifold in said nozzle member upstream of said helical passages, and means for supplying fuel under pressure to said manifold.

2. A nozzle for a fuel oil burner for producing a high temperature flame with high emissivity and a large radiant surface, said nozzle including nozzle means forming a conical recess at the downstream end thereof, said conical recess having a large end and a small end, and forming an included angle which is constant throughout the length of said recess and ranges from 19 to 25, a core having a truncated cone with a large end and a small end, with a steeper angle of taper than the angle of said conical recess, said cone angle being constant throughout the length of said cone and ranging from 15 to 21, with the product of the diameters of the large end of said recess and the small said of said cone exceeding the product of the diameters of the large end of said cone and the small end of said recess, said cone extending into said recess, said nozzle means forming a cylindrical passage beyond the small, blunt end of said cone and located coaxially therewith, a plurality of helical ridges on said core forming a plurality of separated helical passages with a portion of an inner surface of said nozzle means, and means for supplying fuel under pressure to said helical passages.

3. A nozzle according to claim 2 wherein the first product exceeds the second product by a factor of not more than 1.36.

4. A nozzle for a liquid fuel burner for producing a high temperature flame with high emissivity and a large radiant surface, said nozzle including a nozzle member having 'a conical recess at a downstream end thereof, a core having a cone extending into said recess to form an annular passage therewith decreasing in diameter at a uniform rate, said member forming a cylindrical orifice located immediately beyond a small end of said cone and being co-axial therewith, the small end of said cone being blunt with the conical surface of the cone deviating inwardly, and forming a recess immediately upstream of said orifice whereby liquid fuel flowing contiguously to the surface of said cone will separate therefrom at the devitation of the surface, said recess having a radius exceeding the diameter of the small end of said cone and extending completely to the conical surface at the small end of said cone, means for maintaining said member and said core in fixed, spaced relationship, a plurality of helical ridges on said core forming a plurality of separated helical passages with a portion of said spacing means, means forming a manifold in said nozzle member upstream of said helical passages, and means for supplying fuel under pressure to said manifold.

5. A nozzle for a liquid fuel burner for producing a high temperature flame with high emissivity and a large radiant surface, said nozzle including a nozzle member having a conical recess at a downstream end thereof, the included angle of said recess being constant throughout the length of said recess and ranging from 19 to 25 a core having a cone forming an angle which is constant throughout the length of said cone and ranges from 15 to 21, said cone extending into said recess to form an annular passage therewith, said member forming a cylindrical orifice located immediately beyond a small end of said cone and being co-axial therewith, the small end of said cone being blunt with the conical surface of the cone deviating inwardly immediately upstream of said orifice whereby liquid fuel flowing contiguously to .the surface of said cone will separate therefrom at the deviation of the surface, means for maintaining said member and said core in fixed, spaced relationship, a plurality of helical ridges on said core forming a plurality of separated helical passages with a portion of said spacing means, means forming a manifold in said nozzle member upstream of said helical passages, and means for supplying fuel under pressure to said manifold.

References Cited by the Examiner UNITED STATES PATENTS 391,865 10/88 Schutte 158-78 1,089,406 3/41 Fitts 239-488 1,319,527 10/19 Kreuzhage 239488 1,810,689 6/31 Townsend et a1. 239488 FOREIGN PATENTS 829,683 1/52 Germany.

JAMES W. WESTHAVER, Primary Examiner.

PERCY L. PATRICK, MEYER PERLIN, Examiners.

Claims

1. A NOZZLE FOR A LIQUID FUEL BURNER FOR PRODUCING A HIGH TEMPERATURE FLAME WITH HIGH EMISSIVITY AND A LARGE RADIANT SURFACE, SAID NOZZLE INCLUDING A NOZZLE MEMBER HAVING A CONICAL RECESS AT A DOWNSTREAM END THEREOF, THE INCLUDED ANGLE OF SAID RECESS BEING CONSTANT THROUGHOUT THE LENGTH OF SAID RECESS AND RANGING FROM 19* TO 25*, A CORE HAVING A TRUNCATED CONE FORMING AN ANGLE WHICH IS CONSTANT THROUGHOUT THE LENGTH OF SAID CONE AND RANGES FROM 15* TO 21*, SAID CONE EXTENDING INTO SAID RECESS TO FORM AN ANNULAR PASSAGE DECREASING IN DIAMETER AT A UNIFORM RATE, SAID MEMBER FORMING A CYLINDRICAL PASSAGE LOCATED IMMEDIATELY BEYOND A SMALLER, BLUNT END OF SAID CONE AND CO-AXIAL THEREWITH, MEANS FOR MAINTAINING SAID MEMBER AND SAID CORE IN FIXED, SPACED RELATIONSHIP, A PLURALITY OF HELICAL RIDGES ON SAID CORE FORMING A PLURALITY OF SEPARATED HELICAL PASSAGES WITH A PORTION OF SAID SPACING MEANS, MEANS FORMING A MANIFOLD IN SAID NOZZLE MEMBER UPSTREAM OF SAID HELICAL PASSAGES, AND MEANS FOR SUPPLYING FUEL UNDER PRESSURE TO SAID MANIFOLD.