US3460519A - Boiler for firing liquid or gaseous fuel - Google Patents

Description

Aug. l2, 1969 Q QspEL-r' ET AL 3,460,519

BOILER-FOR FIRING LIQUID OR GASEOUS Filed Jam 4, 196s 4 Smets-sheet 1 Aug. 12, 12969n G, QSPELT ET AL 3,460,519 i v BOILERFOR FIRING LIQUID OR GASEOUS FUEL Filed Jan. 4, 1968 4 sheets-sheet 2 l Aug. 12, 1969 G, OSPELT ET AL 3,460,59 V

BOILER FOR FIRING LIQUID OR GASEOUS FUEL Filed Jan. 4. 1968 4 Sheets-Sheet 3 JIAWIA Inventors: aJ/Qr @yo/f /f/ y ffy/- Allg. 12, 1969 G, OSPELT ET AL 3,460,519

BOILER F011 FIRING LIQUID OR GASEOUS FUEL Filed Jan. 4, 1968 4 sheets-sheet 4 United States Patent O 3,460,519 BOILER FOR FIRING LIQUID R GASEOUS FUEL Gustav Ospelt, Vaduz, Alfred Vogt, Schaan, and Hellmut Gutmann, Balzer-s, Liechtenstein, assignors to Gustav Ospelt Hovalwerlk AG, Vaduz, Liechtenstein Filed Jan. 4, 1968, Ser. No. 695,683 Claims priority, application Luxembourg, Jan. 12, 1967, 52,798; Sept. 8, 1967, 54,442 Int. Cl. F22h 7/12 U.S. Cl. 122-149 12 Claims ABSTRACT 0F THE DISCLOSURE A heating boiler having a iirebox extending in the longitudinal direction of the boiler and having a closed end and an open end `with a substantial-ly oval opening, said rebox being eccentric-ally located in said boiler and with the outer boiler wall dening a water jacket through which extend mutually spaced tiue gas passages having their longitudinal extension in the direction of the extension ofthe longitudinal axis of the Iirebox.

The present invention relates to a boiler for tiring liquid or gaseous fuel in a substantially horizontal rebox closed at one end and surrounded by a somewhat bell-shaped water jacket, said tirebox having a portion of its circumference surrounded by flue gas passages extending through said water jacket in the longitudinal direction of said trebox while in front of the open irebox end there is provided an overflow chamber which establishes communication between the ue gas passages and the lirebox and which is closed by a detachable cover carrying the burner extending into the lirebox.

IBoilers of the above mentioned type have become known in which the tirebox has the customary wellknown shape of a circular cylinder so that the burned or flue gases which are deviated -by 180 at the closed rebox end and flow to the open rebox end leave the rebox through a round exit opening which is formed by the open iirebox end. Subsequently, the burned or flue gases pass through a nest of boiler `tubes or tube packet arranged above the rebox in the water jacket surrounding the irebox. The said nest of boiler tubes or tube packet comprises a plurality of tubes of 4round or square cross section which `are arranged adjacent and above each other and extend in the direction of the axis of the trebox.

It is an object of the present invention to provide a boiler of the above general type which will have an irnproved arrangement for the guiding of the liuc or burned gases and will have an improved heat transfer from the ilue or burned gases to the boiler water.

It is another object of the invention to provide a boiler, as set forth in the preceding paragraph which will greatly improve the economy of the boiler while resulting in a compact simplified construction of the boiler.

These and other objects and advantages of the invena tion will appear more clearly from the following specilication, in connection with the accompanying drawings, in which:

FIGURE 1 is a vertical central section through a boiler according to the present invention;

FIGURE 2 represents a cross section taken along the line lI-II of FIG. l;

FIGURE 3 shows a vertical central section through a portion of a nrodied boiler according to the invention;

FIGURE 4 is a cross section taken along the line IV-IV of FIG. 3.

FIGURE 5 is -a vertical central section through a por- ICC tion of still another modification of the boiler according to the invention;

FIGURE 6 is a cross section `taken along the line VI--VI Of FIG. 5;

t FIGURE 7 diagrammatically shows a view of a tin equipped pipe;

FIGURE 8 is a cross section taken Ialong the line VIII-VIII of FIG. 7;

FIGURE 9 shows a view of -a modified flue gas passage or conduit for a boiler according to the invention;

FIGURE l0 is a section taken along the line X--X of FIG. 9; and

FIGURE 11 is a section taken along the line XL-XI of FIG. 9.

The boiler :according to the present invention is char- -acterized primarily in that the vl'irebox Iat its open end has an oval shape and is so eccentrically arranged with regard to the substantially cylindrical outer wall of said -boiler that the large diameter of said oval firebox end is located in spaced relationship to and adjacent the central axis of the outer wall of the boiler, whereas the small diameter of said oval iirebox end passes through said central -axis while the ue passages or conduits extend through that circumferential portion of the water jacket which has the greater radial width.

Referring now to the drawings in detail and FIGURES 1 and 2 thereof in particular, the boiler shown in FIG- URES 1 and 2 has a water jacket 2 contined toward the outside by a cylindrical outer Wall 1. Eccentrically arranged in said water jacket 2 yand offset thereto in downward direction is a rebox 3 which has a circular closed iirebox end t4 and an oval, or somewhat elliptical open iirebox end 5. The large diameter of said oval or elliptical open irebox end 5 is spaced from and loc-ated below the central axis of the outer wall 1. The small diameter of said oval or elliptical iirebox end 5 extends through said central axis.

Whereas with a circular open firebox end the gas flow leaving the lirebox is in its lateral portions, i.e., in the marginal portions relatively weak in comparison to its central portion so that the outer flue gas conduits are passed thro-ugh by the flue gases to a considerable less extent than the central Hue gas conduits, according to the present invention, in view of the oval or elliptical open irebox end, the gas iiow returning in the rebox is so shaped that it leaves the irebox with an increased volume at the narrowed portion of the oval, which means within the area of the outer ue gas conduits. Also, the outer flue gas conduits are therefore acted upon and passed through by the burned gases more intensively so that an improved exploitation of the heat exchanger surfaces of said flue gas conduits is realized, and in particular in these flue gas conduits the danger of an under cooling and corrosion will be avoided. Actual tests have proved that the dilerence in temperatures at which the flue gases enter the central and outer ilue gas conduits, with an oval open irebox end is considerably lower than with a customary circular open rebox end.

That circumferential portion of the water jacket 2 which has the larger radial width, in other words, that portion of the water jacket 2 which is located about the rebox 3 has extending therethrough ue gas conduits 6.

These flue gas conduits are formed by tubes 6 of flattened and approximately oval cross section. The tubes 6 are disposed with their longer cross sectional dimension perpendicular to the larger diameter of the oval iirebox end 5 and with their longer side faces are spaced apart. While the distance between the longer sides of each tube is constant, the depth of each tube 6 diminishes progressively in the direction of flow of the iiue gases as it clearly shown in FIG. 1.

The oval form of the open end of the firebox, particularly at the end 5, increases the water space available for accommodation of the flue gas tubes between `the wall of the firebox and the outer wall of the water jacket so that the outer wall of the water jacket can be a conventional and easily fabricated cylinder of sheet metal, while ample space is nevertheless available, especially for the flattened flue gas tubes 6, the major dimension of which is at the open end of the firebox. Also at the open end of the firebox, the wall of the combustion chamber and the outer wall of the water jacket are, in view of the oval form of the outer end of the combustion chamber, over a wide range, substantially equally vertically spaced so that identical flattened fiue gas tubes with substantially equal longer cross sectional dimension can be utilized and disposed adjacent one another in the water space with their larger side faces facing each other.

As the depth of the adjoining flattened tubes decreases towards the closed end of the combustion chamber, which can readily be achieved with the flattened configuration of the tubes, there is realized on one hand a progressive decrease in cross sectional area of the tubes in the direction of fiow of the gases and therefore, a substantially constant speed of flow of the combustion gases cooling off. This has a favorable effect on the heat transfer, and on the other hand makes it possible to make the closed end of the combustion chamber of increased cross sectional area. The flat and somewhat oval tubes 6 have a very large surface area and, therefore, bring about the advantage that sufficient heat exchange of the fiue gas conduits can be achieved with comparatively few tubes so as to reduce the manufacturing costs arising from welding the tubes 6 to the boiler. The iiattened tubes 6 also have the important advantage as compared with round or rectangular tubes that practically no dead or incompletely utilized core develops in the gas ow so that there is no need to provide in the tubes devices creating turbulence as, for instance, spiral inserts or the like.

At the open firebox end 5, the firebox 3 and the tubes 6 are connected by an overflow chamber or header 7 which is closed by a cover 8 and which carries a burner 9 projecting into the open end 5 of the firebox. The stream of burned gases owing back in the firebox 3 toward its open end is formed by the oval form of said open end 5 into a broad gas stream which is powerful and intensive at the lateral edge zones so that the outermost tubes 6 at the right and left hand are traversed by these intensive parts of the gas stream. In view of the progressively diminishing depths of the tubes 6, the speed of travel of the burned gases cooling off remains substantially constant so that a substantially constant heat exchange occurs throughout the length of the tubes 6.

As mentioned above, the tubes 6 can readily be fabricated from strips of wedge-shaped cut sheet metal by bending the strips longitudinally about wedge-shaped formers and welding the abutting edges to produce a tube of progressively decreasing depth. The wider sides of the tubes 6 are stiffened by transverse, preferably inwardly projecting ribs 1t), which additionally aid in creating a turbulence in the flue gases.

The firebox may advantageously be so designed that its cross section gradually merges from its oval shape at the open firebox end into a circular shape at the closed end of the firebox while both firebox ends have substantially the same circumference.

Despite providing a large heating surface which augmented by the high heat transfer from the combustion gases on their way through the boiler, yields a high boiler performance, the boiler has a compact pressure-resistant construction so that the Walls subject to the pressure of the boiler water, can be comparatively thin.

Inasmuch as the front oval shape of the firebox gradually merges with the rear circular shape, and since both firebox ends have substantially the same circumference, the firebox can be made of a simple round bottom and a rectangular mantle sheet. The cylinder formed in this way is then, at its open end, compressed into the desired oval shape.

According to one advantageous construction, the boiler has a wall at the open end of the firebox which Wall is substantially confined to the side of the larger diameter nearer the iiue gas tubes 6 and provides an outlet opening from the combustion chamber to the header. The boiler includes within the header finned tubes which preferably extend at right angles to the larger diameter of the open end of the firebox with their fins substantially parallel to the gas fiow, while between the wall and the cover, a burner tube extends through the header into the Iirebox.

More specifically, with the boiler according to FIGS. 3 and 4, a wall 20 is provided at the open end 5 of the firebox, which wall 20 leaves an exit opening 21 from the firebox 3 to the header 7, said opening being confined to the side of the larger diameter of the open end remote from' the tubes 6. In this way, the space of the header 7 is taken advantage of, and the boiler heating surface and the degree of efiiciency of the boiler is greatly increased. The flue gases which also in this instance leave the rebox in the' form of a wide gas flow strong at the marginal areas, are forced to leave the firebox 3 at the lowermost point of the header 7 and to iiow into the latter so as to pass therethrough on as long a path as possible up to the tubes 6. The wall 20 carries a burner tube 22 which is open to the firebox 3 and extends through the header 7 up to the cover 8. The wall 20 and the burner tube 22 form walls for confining boiler water. Within the header 7 transverse to the large diameter of the oval firebox end there are provided vertical finned pipes 23. These finned pipes or tubes are impinged upon by the upwardly owing flue gases so that already in the header 7 an intensive heat exchange to the boiler water occurs before the burned gases reach the tubes 6.

In this way, optimum use is made of the header. The finned tubes 23 are so arranged that the openings of the tubes 6 leading into the header 7 are not covered up. In this way, when tilting the cover 8 which is hinged to the boiler, into its open position, the tubes 6 can easily be cleaned between the finned pipes 23. The firebox 3 is accessible below the burner tube 22 for cleaning said firebox, since no finned pipes are required at the bottom side of the burner tube 22.

The boiler shown in FIGS. 5 and 6 corresponds in principle to the boiler in FIGS. 3 and 4. However, in contradistinction to FIGS. 3 and 4, with the arrangement of FIGS. 5 and 6, the header does not form a part of the boiler but represents a portion of a somewhat bell-shaped cover 30 in which a cavity is provided on the inner side of the cover and forms a header 31. The cover 30 is traversed by boiler water, and also in this instance, the header 31 comprises vertical water filled finned tubes 32. The inside of the cover 30 is provided with a burner surrounding tube 33 which is filled with boiler water and extends through the header 31 into the open firebox end S. This open end 5 is provided with a boiler water filled wall 34 which leaves an exit opening 35 from the fireboX 3 to the header 31 only on that side of the large diameter of the oval firebox end 5 which faces away from the tubes 6. The burned gases will also in this instance be forced to enter the header 31 is deeply as possible and with a wide gas tiow which is strong at the marginal areas. The burned gases flow through said header up to the tubes 6 along a path as long as possible. Since the finned pipes 32 are arranged on the inside of the cover 30 and are adapted together with the cover 3@ which is connected to the boiler by a hinge 36 (FIG. 6), to be tilted away from the boiler, the tubes 6 and the open rebox end 5 are completely freely accessible from the front for purposes of cleaning and inspection. Consequently, a large number of closely spaced finned tubes may be arranged on the inside of the cover 30. These finned tubes may, as shown in FIG. 6 in closed position of the cover 30 be located in front of the openings of the tubes 6 and also on the bottom side of the burner tube 33. In addition thereto, this boiler construction brings about the great advantage that the cavity on the inside of the cover 30` which cavity forms the header 31 may be dimensioned as deep as desired to permit at will the welding of only one finned pipe row or according to FIG. two linned pipe rows or more to the cover 30 without the necessity of any welding operations on the boiler, the boiler can be altered by simple exchange of the cover 30, for instance by the employment of a cover with three or more rows of finned pipes the boiler output may be considerably increased. With this boiler construction, it is also possible to make the finned pipes better accessible for cleaning purposes because the water cooled cover can without any diiculties have its outside provided with additional cleaning openings so that access will be gained tothe finned pipes from both sides. At the lowermost and highest points, the jacket 2 andthe cover 30 communicate with each other by water pipes 37. These pipes 37 are within the area of the hinge 36 provided with flexible metallic hoses to permit pivoting of the cover 30 without the necessity of emptying the boiler and disassembling the pipes 37.

In order to assure that the fins of the tubes 23 (FIG. 3) and 32 (FIG. 5) will be intensively raked by the burned gases over their entire finned surface, the fins are advantageously so arranged that they extend substantially parallel to the gas ow. Tubes with fins which extend in the direction of the gas flow, which in conformity with FIGS. 3-6 extend transverse to the large diameter of the oval iirebox end and thus are arranged vertically, may advantageously be designed as pipes with corrugated strips which are partic-ularly noted for the fact that they have an extremely large heat exchanging surface of the tins in spite of a relatively short overall diameter. They also have a very high heat transfer capability. Such corrugated strip tube is illustrated by Way of examples in FIGS. 7 and 8. More specifically two elongated corrugated metal strips 40 and 41 are coiled helically adjoining one another around the outer surface of a cylinder tube 42. The strips 40 and 41 are metallically connected to the outer surface of tube 4Z at their zones of contact to provide thermal conduction. As shown in FIG. 8, the arrangement may be such that by the application of two corrugated strips it can easily be assured that the ribs formed by the corrugated strips are offset relative to each other from coil to coil or winding to winding so that the corrugated strip ribs of each winding can be acted upon intensively inside and outside by the burned gases.

Instead of the tubes 6, also cylindrical tubes may be employed as iiue gas channels, if the tapering of the flue gas conduits in the direction of flow of the gases is not necessary. Advantageously, the cylindrical tubes are so designed that their wall is provided with peripheral depressions which bring about decreases or constrictions in the cross section.

FIG. 9 is a side view of a cylindrical tube 50 having in its wall spaced trough or groove-shaped depressions 51. This is clearly shown in FIGS. 9-11. FIG. 9 shows a view of a cylindrical pipe 50 having its wall provided with spaced bead-shaped or groove-shaped depressions 51. FIG. l0 is a cross section through pipe 50, and FIG. 1l is a longitudinal section through pipe 50. The depressions 51 convert the smooth cylindrical pipe into a grooved tube. The depressions which can easily be produced in ordinary cylindrical pipes by light and noncomplicated tools have the advantage that the burned gases are subjected to considerable turbulence which in turn forces them to an intensive heat transfer so that special assemblies, as for instance twisted metal strips become superfluous which heretofore had to be provided with customary smooth cylindrical pipe in order to produce a gas turbulence.

If desired, each cross sectional area of a pipe may be provided with two depressions which as shown in FIG. 10 are arranged diagrammatically opposite to each other. However, if desired, for instance, three depressions distributed over the circumference of the pipe or only one annular depression may be provided. The above mentioned grooved pipes are also useful with other boiler constructions of the type mentioned above.

It is, of course, to be understood that the present invention is, by no means, limited to the particular embodiments referred to above, but also comprises any modifications within the scope of the appended claims.

What We claim is:

1. A heating boiler which comprises: an outer portion of approximately cylindrical shape with the longitudinal axis thereof extending in the longitudinal direction of said boiler, an inner portion forming a tirebox and having its longitudinal extension in the direction of the longitudinal axis of said outer portion while being arranged within and eccentrically with regard to said outer portion so as to define therewith a larger water jacket portion and a smaller water jacket portion, said iirebox having a closed end and also having an open end with an oval opening the large diameter of which is transverse to and spaced from the longitudinal axis of said outer portion Whereas the small diameter of said oval opening at least nearly intersects the longitudinal axis of said outer portion, and a plurality of iiue gas passage means communicating with said firebox and extending into said larger water jacket portion in the longitudinal direction of said iirebox.

2. A boiler according to claim 1, in which said ilue gas passage means are formed by flattened mutually spaced tubes of approximately oval cross section with the longer cross sectional dimension thereof approximately per pendicular to the large diameter of said o'val opening and with their larger side faces spaced apart, the longer cross sectional dimension of said flue gas passage means continuously decreasing in the direction toward the closed end of said iirebox.

3. A boiler according to claim 2, in which the larger faces of the tubes are provided with ribs extending transverse to the longitudinal axes of said tubes.

4. A boiler according to claim 3, in which said ribs partially extend into the interior of said tubes.

5. A boiler according to claim 1, in which said ue gas passage means are formed by cylindrical tubes having peripheral depressions and locally reducing the cross section of the respective tube.

6. A boiler according to claim 1, in Which the cross section of the firebox changes its shape gradually from that end which comprises the oval opening to a circular form at the closed end of said irebox, both ends of said irebox having approximately the same peripheral length.

7. A boiler according to claim 1, which includes: a closure wall arranged at said open end of :said rebox and closing that portion only of said oval opening which is 10- cated on that side of said large diameter which is adjacent said ue gas passage means, a header interposed between and in communication with both the other portion of said opening of said iirebox and said llue gas passage means, burner tube means extending from the outside of said header through the latter into said tirebox, and iinned pipe means adapted to receive and contain boiler water while communicating with said water jacket and extending into said header, the iins of said nned pipe means being substantially parallel to the gas flow.

8. A boiler according to claim 7, in which said finned pipe means extend approximately at a right angle with regard to the large diameter of said oval opening.

9. A boiler according to claim 8, in which said nned pipe means are formed by tubes having ondulated strips connected to the outside of said tubes.

10. A boiler according to claim 7, in which said closure wall and said burner tube form a part of the water jacket.

11. A boiler according to claim 8, in which said iinned 7 8 pipe means extend laterally of the connections of said ue References Cited gas passage means with said header. D TES PATENTS 12. A boiler according to claim 7, in which said header UNITE STA and said finned pipe means form part of a cover hinged 3,171,388 3/1965 Ganz 122 149 to said boiler and adapted to be pivoted selectively in a 5 312301936 1/1966 Clefwer et al' 122*`149 direction away from said boiler, and in which flexible con- 313291131 7/1967 Wnght 122-'149 duit means are provided connecting said finned pipe means with Said Water jacket. CHARLES I. MYHRE, Primary Examiner

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