EP1584868A2

EP1584868A2 - Cylindrical burner

Info

Publication number: EP1584868A2
Application number: EP05252224A
Authority: EP
Inventors: Misako Rinnai Corporation Tachi; Yoshihiko Rinnai Corporation Takasu
Original assignee: Rinnai Corp
Current assignee: Rinnai Corp
Priority date: 2004-04-09
Filing date: 2005-04-08
Publication date: 2005-10-12
Anticipated expiration: 2025-04-08
Also published as: EP1584868B1; EP1584868A3; JP3958754B2; JP2005299998A

Abstract

The invention provides a cylindrical burner including: a heat chamber having a plurality of burner ports; and a distribution pipe in the heat chamber having a plurality of distribution holes, wherein, even if a mixed gas is supplied while keeping a motion component in a radial direction of a heat chamber, uniform combustion is performed over an entire periphery of the heat chamber. An inlet pipe, which extends in an axial direction to a position in front of a top end of the heat chamber, is provided in the distribution pipe to rectify the mixed gas into a flow that hardly has a motion component in the radial direction and supply the mixed gas into the distribution pipe. An annular baffle board, which narrows a gap between the distribution pipe and the heat chamber, is provided in an outer periphery of the distribution pipe a predetermined distance apart to the base end side from the top end of the inlet pipe. The distribution holes are not formed in the distribution pipe in a portion closer to the inlet pipe in an axial direction area between the top end of the inlet pipe and the top end of the heat chamber and a portion between the top end of the inlet pipe and a position near an arrangement section of the baffle board.

Description

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a cylindrical burner that is used in a spiral water pipe heat exchanger and the like.

Description of the Related Art

Conventionally, there is known a spiral water pipe heat exchanger in which, as shown in FIG. 1, a spiral condensed water pipe 101 and a spiral heating water pipe 102 are housed in a housing 100 and a cylindrical burner A serving as a heat source is arranged in a space surrounded by the heating water pipe 102. An upstream end of the condensed water pipe 101 is connected to a water supply header 103, a downstream end of the condensed water pipe 101 and an upstream end of the heating water pipe 102 are connected with each other via a relay header 104, and a downstream end of the heating water pipe 102 is connected to an outlet hot water header 105. Mixed gas of fuel gas and air is forcibly supplied to the cylindrical burner A via a fuel pipe B and burns on an outer peripheral surface of the cylindrical burner A. Combustion exhaust gas of the cylindrical burner A passes an arrangement portion of the condensed water pipe 101 to be discharged from an exhaust port 106 at an end of the housing 100. Then, water vapor in the combustion exhaust gas is condensed with latent heat thereof collected by water flowing to the condensed water pipe 101. The condensed water is discharged from a drain hole 107 of the housing 100. The water, which is preheated with the latent heat collected, is heated by combustion flames of the cylindrical burner A when the water passes the heating water pipe 102 and changes to high-temperature hot water. The hot water is sent to the outside of the heat exchanger via the outlet hot water header 102. Note that, in FIG. 1, the condensed water pipe 101 and the heating water pipe 102 are formed in a double helical shape.

In addition, as the cylindrical burner, conventionally, there is known a cylindrical burner including: a heat chamber, in a peripheral surface of which a plurality of burner ports are opened; a base plate having an inlet port mounted at a base end of the heat chamber; and a cover plate mounted at a top end of the heat chamber, wherein mixed gas flowing in an internal space of the heat chamber from the inlet port is jetted from the burner ports of the heat chamber and burnt (see, for example, Japanese Utility Model Publication No. Sho 61-26737). Note that, in this cylindrical burner, the heat chamber is constituted by combining plural strip-like combustion plates of ceramics having a plurality of burner ports in a cylindrical shape.

Pressure distribution of the mixed gas in the heat chamber is high on the top end side of the heat chamber that serves as a dead-end portion of the mixed gas flowing in from the inlet port. Therefore, jet quantity of the mixed gas from the heat chamber is large on the top end side compared with the base end side. As a result, axial direction distribution of the jet quantity of the mixed gas is made non-uniform. In this case, it is conceivable to provide a distribution pipe, which partitions the space in the heat chamber into inner and outer two chambers, extending in an axial direction from the base plate to the cover plate in the inside of the heat chamber, causing the mixed gas to flow into the inner chamber on the inner side of the distribution pipe from the inlet port, and causing the mixed gas, which has flown into the inner chamber, to flow into the outer chamber on the outer side of the distribution pipe via a plurality of distribution holes formed in the distribution pipe. Consequently, pressure distribution in an axial direction in the outer chamber is uniformalized by reducing an arrangement density of the distribution holes on a top end side of the distribution pipe. Thus, it is possible to uniformalize the axial direction distribution of the jet quantity of the mixed gas from the heat chamber.

Incidentally, in general, the fuel pipe B is formed in an L shape bending in a direction perpendicular to the axial direction of the heat chamber (in a radial direction of the heat chamber) in order to reduce a space occupied by the fuel pipe B. Therefore, the mixed gas flows into the inlet port from the fuel pipe while keeping a motion component in the radial direction of the heat chamber. A jet quantity of the mixed gas from the heat chamber increases in a peripheral direction portion matching this radial direction. As a result, a peripheral direction distribution of the jet quantity of the mixed gas is made non-uniform.

In view of the problems described above, embodiments of the invention seek to provide a cylindrical burner that can advantageously uniformalize distributions of a jet quantity of the mixed gas from a heat chamber in both a peripheral direction and an axial direction such that uniform combustion is preferably performed over an entire area on a peripheral surface of the heat chamber, even if mixed gas flows in from an inlet port which has or maintain a component of motion in a radial direction with respect to the heat chamber.

In order to substantially alleviate the above problems, preferred embodiments of the invention provide a cylindrical burner including: a heat chamber, in a peripheral surface of which a plurality of burner ports are opened; a base plate having an inlet port mounted at a base end of the heat chamber; a cover plate mounted at a top end of the heat chamber; and a distribution pipe, which partitions the space in the heat chamber into inner and outer two chambers, extending in an axial direction from the base plate to the cover plate in the inside of the heat chamber, the cylindrical burner causing the mixed gas to flow into an inner chamber on an inner side of the distribution pipe from the inlet port and causing the mixed gas, which has flown into the inner chamber, to flow into an outer chamber on an outer side of the distribution pipe via a plurality of distribution holes formed in the distribution pipe, wherein an inlet pipe, which is connected to the inlet port and extends in the axial direction to a position closer to a top end of the distribution pipe, is arranged in the inner chamber, an annular baffle board, which is located in a section a predetermined distance apart from a top end of the inlet pipe to a base end side of the distribution pipe and narrows a gap between an outer periphery of the distribution pipe and an inner peripheral surface of the heat chamber, is arranged in the outer periphery of the distribution pipe, and assuming that an opening area of distribution holes per a unit area of the distribution pipe is a distribution hole density, the distribution hole density falls to zero or a very small value near zero in a portion closer to the top end of the inlet pipe in an axial direction area between the top end of the inlet pipe and the top end of the distribution pipe and a portion between the top end of the inlet pipe and the portion near the arrangement section of the baffle board.

According to an embodiment of the invention, even if mixed gas flows in from the inlet port while keeping a motion component in the radial direction of the heat chamber, the mixed gas is rectified to a flow, which hardly has a motion component in the radial direction, in a process of passing the inlet pipe. Thus, a peripheral direction distribution of the jet quantity of the mixed gas from the heat chamber is advantageously uniformalized.

However, since the mixed gas flows into the inner chamber from the inlet pipe in a position close to the top end of the heat chamber, mixed gas pressure in the inner chamber is extremely high at the top end portion. Thus, it is difficult to realize uniformalization of an axial direction distribution of the mixed gas pressure in the outer chamber only by setting distribution hole densities in respective parts of the distribution pipe. Here, a part of the mixed gas, which has flown into the inner chamber from the inlet pipe, flows to the outer chamber in the axial direction area between the top end of the inlet pipe and the top end of the heat chamber and the remaining mixed gas flows to the base end side of the heat chamber through a void (an outer peripheral void of the inlet pipe) between an outer periphery of the inlet pipe and the distribution pipe. In this case, if distribution holes are formed in a portion closer to the top end of the inlet pipe (an area indicated by "c" in FIG. 4) in the axial direction area between the top end of the inlet pipe and the top end of the heat chamber, the mixed gas, which should be caused to flow into the outer peripheral void of the inlet pipe, flows to the outer chamber via the distribution holes in this portion (the "c" area). As a result, the amount of the mixed gas flowing into the outer peripheral void of the inlet pipe is insufficient. However, in the invention, a distribution hole density in the portion (the "c" area) closer to the top end of the inlet pipe in the axial direction area between the top end of the inlet pipe and the top end of the heat chamber is set to substantially zero. Thus, it is possible to supply the mixed gas sufficiently to the outer peripheral void of the inlet pipe. Therefore, it is possible to uniformalize an axial direction distribution of a mixed gas pressure in the outer chamber in this area by appropriately setting a distribution hole density in an area from the arrangement section of the baffle board to the base end of the heat chamber. As a result, it is also possible to uniformalize an axial direction distribution of the jet quantity of mixed gas from the heat chamber in this area.

In addition, in the axial direction area between the top end of the inlet pipe and the top end of the heat chamber, the mixed gas flows into the outer chamber from distribution holes in a limited portion other than the portion closer to the top end of the inlet pipe (the "c" area). The mixed gas, which has flown into the outer chamber, flows in the outer chamber toward the base end side. However, the mixed gas is prevented from flowing further to the base end side by the baffle board in the outer periphery of the distribution pipe. Note that, in a portion between the top end of the inlet pipe and the position near the arrangement section of the baffle board (an area indicated by "d" in FIG. 4), the velocity of flow of the mixed gas flowing to the outer peripheral void of the inlet pipe is high and the pressure in the outer peripheral void of the inlet pipe tends to be negative. Thus, if distribution holes are formed in the portion between the top end of the inlet pipe and the position near the arrangement section of the baffle board (the "d" area), the mixed gas, which has flown into the outer chamber, is sucked into the outer peripheral void of the inlet pipe. However, since distribution hole density in the portion between the top end of the inlet pipe and the position near the arrangement section of the baffle board (the "d" area) is preferably set to substantially zero, the mixed gas, which has flown into the outer chamber, is advantageously never sucked into the outer peripheral void of the inlet pipe. Therefore, the pressure distribution of the mixed gas in the portion of the outer chamber between the arrangement section of the baffle board and the top end of the heat chamber is easily uniformalized by setting the distribution hole density to substantially zero and by a function of the baffle board. As a result, the axial direction distribution of the jet quantity of the mixed gas from the heat chamber between the arrangement section of the baffle board and the top end of the heat chamber may be uniformalized.

However, if burner ports are present in an axial direction position matching a portion where the distribution holes are formed (a portion other than the portion closer to the top end of the inlet pipe) in the axial direction area between the top end of the inlet pipe and the top end of the heat chamber, the mixed gas flowing from the distribution holes proceeds straight to the outside in the radial direction toward the burner ports. As a result, the jet quantity of the mixed gas from the burner ports is made excessive. In this case, a leading end in the axial direction in the burner port opened area of the heat chamber is set to be located in the portion closer to the top end of the inlet pipe (the "c" area) in the axial direction area between the top end of the inlet pipe and the top end of the heat chamber or the portion between the top end of the inlet pipe and the portion near the arrangement section of the baffle board (the "d" area). Consequently, there is no burner ports in the axial direction position matching the portion where the distribution holes are formed in the axial direction area between the top end of the inlet pipe and the top end of the heat chamber. Thus, the deficiency described above never occurs.

Further, the distribution hole density in the portion other than the portion closer to the top end of the inlet pipe (the "c" area) in the axial direction area between the top end of the inlet pipe and the top end of the distribution pipe is set appropriately such that the mixed gas pressure in the outer chamber in the area from the arrangement section of the baffle board to the top end of the heat chamber and the mixed gas pressure in the outer chamber in the area from the arrangement section of the baffle board to the base end of the heat chamber are equal. Consequently, it is possible to uniformalize the axial direction distribution of the jet quantity of the mixed gas from the heat chamber over the entire length of the heat chamber. Therefore, it is possible to obtain uniform combustion over the entire peripheral area of the heat chamber in conjunction with the uniformalization of the peripheral direction distribution of the jet quantity of the mixed gas from the heat chamber due to the action of the inlet pipe.

Pressure of the mixed gas tends to be low in a portion near the arrangement section of the baffle board (an area indicated by "e" in FIG. 4) in the outer chamber. Therefore, it is desirable to set the distribution hole density in the portion near the arrangement section of the baffle board (the "e" area) larger than the distribution hole density in a portion between the base end of the heat chamber and the portion near the arrangement section of the baffle board (an area indicated by "f" in FIG. 4) to compensate for the pressure drop in the portion near the arrangement section of the baffle board (the "e" area) in the outer chamber.

When the axial direction area between the top end of the inlet pipe and the top end of the heat chamber is divided into three portions, namely, the portion closer to the top end of the inlet pipe (the "c" area), a middle portion (an area indicated by "b" in FIG. 4), and a portion closer to the top end of the heat chamber (an area indicated by "a" in FIG. 4), in the portion closer to the top end of the heat chamber (the "a" area), mixed gas pressure in the inner chamber is extremely high. If the distribution hole density in this portion is increased, a large amount of the mixed gas flows from this portion to the outer chamber. As a result, the amount of the mixed gas supplied to the outer peripheral void of the inlet pipe tends to be insufficient. On the other hand, if the distribution pipe density in the portion closer to the top end of the heat chamber (the "a" area) is set to zero or a very small value near zero and distribution holes are formed concentratedly in the middle portion (the "b" area), mixed gas pressure in the inner chamber in the middle portion (the "b" area) is lower than that in the portion near the top end of the heat chamber (the "a" area). Thus, the mixed gas never flows to the outer chamber excessively and it is possible to supply the mixed gas to the outer peripheral void of the inlet pipe sufficiently.

Note that, although a reason will be explained later, it is desirable to set a distance between the top end of the inlet pipe and the top end of the heat chamber in a range of 15 to 35% of the total length of the heat chamber. In addition, it is desirable to set a distance between the top end of the inlet pipe and the baffle board in a range of 80 to 100% of the distance between the top end of the inlet pipe and the top end of the heat chamber.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example to the accompanying drawings in which:

FIG. 1 is a schematic sectional side view of a spiral water pipe heat exchanger that uses a cylindrical burner as a heat source;

FIG. 2 is a plan view of a cylindrical burner in an embodiment of the invention;

FIG. 3 is a sectional view cut along line III-III in FIG. 2; and

FIG. 4 is a sectional view cut along line IV-IV in FIG. 3.

A cylindrical burner in an embodiment of the invention shown in FIG. 2 is a burner that is used as a heat source for a spiral water pipe heat exchanger in FIG. 1. This burner includes a heat chamber 1 of a cylindrical shape, a base plate 2 mounted at a base end of the heat chamber 1, and a cover plate 3 mounted at a top end of the heat chamber 1. As shown in FIG. 3, the heat chamber 1 is constituted by combining plural (six in an example shown in the figure) strip-like combustion plates 1b of ceramics, which have a plurality of burner ports 1a, in a cylindrical shape. In the heat chamber 1, as shown in FIG. 4, a distribution pipe 4 extending in an axial direction thereof from the base plate 2 to the cover plate 3 is provided. Note that the distribution plate 4 is formed in a hexagonal cylindrical shape similar to an inner surface shape of the heat chamber 1. Apluralityof distribution holes 4a are formed on a peripheral surface of the distribution pipe 4 in a predetermined layout described later.

The distribution pipe 4 is fixed to the base plate 2 at a base end thereof by spot welding or the like. A cap 4b is fastened to a top end of the distribution pipe 4. A projected portion 4c, which is fit and inserted in an inner periphery of the cover plate 3 formed in an annular shape, is formed in this cap 4b. In assembling the burner, first, the plural combustion plates 1b are combined in a cylindrical shape to preliminarily assemble the heat chamber 1. Next, the preliminarily assembled heat chamber 1 is bound by an appropriate binding element such as a band such that the combustion plates 1b are not disarranged. In this state, the distribution pipe 4 is inserted into the heat chamber 1 to set the base plate 2 in abutment against an end face on the base end side of the heat chamber 1 via a packing 5. Next, the cover plate 3 is set in abutment against an end face on the top end side of the heat chamber 1 via another packing 5. In this case, the projected portion 4c is inserted into the inner periphery of the cover plate 3. Finally, the projected portion 4c is crushed inwardly in the axial direction. Consequently, the cover plate 3 is caulked and fixed to the distribution pipe 4 in a state in which the cover plate 3 is pressed inwardly in the axial direction. Thus, the heat chamber 1 is held firmly between the base plate 2 and the cover plate 3.

Note that an annular seat plate 6 opposed to the end face on the base end side of the heat chamber 1 is fixed to the base plate 2 by spot welding or the like. Annular flange sections 6a and 3a bending inwardly in the axial direction are formed in outer peripheries of the seat plate 6 and the cover plate 3, respectively, such that the packings 5 do not deviate in the radial direction.

An inner space of the heat chamber 1 is partitioned into an inner chamber 7 on an inner side of the distribution chamber 4 and an outer chamber 8 on an outer side of the distribution pipe 4 by the distribution pipe 4. As shown in FIG. 4, an inlet port 2a, in which a mixture of fuel gas and primary air forcibly supplied from a fuel pipe B is caused to flow, is provided in the base plate 2. An inlet pipe 9, which stretches to the inlet port 2a and extends in the axial direction to a position closer to a top end of the heat chamber 1, is provided in the inner chamber 7. Consequently, the mixed gas supplied from the fuel pipe B flows into the inner chamber 7 via the inlet pipe 9, flows into the outer chamber 8 from the inner chamber 7 via the distribution holes 4a, and jets from the burner ports 1a of the heat chamber 1 to burn.

The inlet pipe 9 is provided to rectify the mixed gas, which flows into the inlet port 2a from the fuel pipe B bending in the radial direction of the heat chamber 1 while keeping a motion component in the radial direction of the heat chamber 1, to a flow, which hardly has the motion component in the radial direction, and cause the mixed gas to flow into the inner chamber 7. Peripheral direction distribution of the jet quantity of the mixed gas from the heat chamber 1 is uniformalized by this rectifying action. Here, a distance L2 between a top end of the inlet pipe 9 and the top end of the heat chamber 1 is set in a range of 15 to 35% of a total length L1 of the heat chamber 1. A reason for this is as described below. If the distance L2 is shorter than the distance in this range, mixed gas pressure between the top end of the inlet pipe 9 and the top end of the distribution pipe 4 is made excessive and an outflow resistance of the mixed gas from the inlet pipe 9 increases to increase a pressure loss of the burner. On the other hand, if the distance L2 is longer than the distance in the range, the mixed gas cannot be sufficiently rectified to the flow, which does not have the radial direction motion component, due to the insufficient length of the inlet pipe 9. Note that, in this embodiment, a portion on the inner peripheral side of the cover plate 3 is sunken inwardly in the axial direction in order to increase rigidity of the cover plate 3. A length of the distribution pipe 4 is shorter than a length of the heat chamber 1 because of the sunken portion. Even in this case, the pressure loss of the burner does not increase so much if the distance L2 between the top end of the inlet pipe 9 and the top end of the heat chamber 1 is set to about 15% or more of the total length L1 of the heat chamber 1.

An annular baffle board 10, which narrows a gap between an outer periphery of the distribution pipe 4 and an inner peripheral surface of the heat chamber 1, is provided in the outer periphery of the distribution pipe 4 in a position a predetermined distance L3 apart to the base end side of the distribution pipe 4 from the top end of the inlet pipe 9. It is preferable that the baffle board 10 narrows the gap between the inner peripheral surface of the heat chamber 1 and the outer peripheral surface of the distribution pipe 4 (a radial direction width of the outer chamber 8) to be half or less. For example, assuming that a radial direction height of the baffle board 10 is H1 and a gap between the inner peripheral surface of the heat chamber 1 and the baffle board 10 is H2, the gap is set such that a ratio of H1 and H2 is about 4:3. The distance L3 is set in a range of 80 to 100% of the distance L2 between the top end of the inlet pipe 9 and the top end of the heat chamber 1. A reason for this will be described later.

An arrangement pattern of the distribution holes 4a formed in the distribution pipe 4 is set as described below in relation to the inlet pipe 9 and the baffle board 10. For convenience of explanation, the heat chamber 1 is sectioned in the axial direction as follows. A portion closer to the top end of the heat chamber 1 in the axial direction area between the top end of the heat chamber 1 and the top end of the inlet pipe 9 is set as an "a" area, a middle portion in the axial direction area between the top end of the heat chamber 1 and the top end of the inlet pipe 9 is set as a "b" area, a portion closer to the top end of the inlet pipe 9 in the axial direction area between the top end of the heat chamber 1 and the top end of the inlet pipe 9 is set as a "c" area, a portion between the top end of the inlet pipe 9 and the portion near the arrangement section of the baffle board 10 is set as a "d" area, a portion near the arrangement portion of the baffle board 10 around the baffle board 10 is set as an "e" area, and a portion between the "e" area and the base end of the heat chamber 1 is set as an "f" area. The distribution holes 4a are formed only in the "b" area, the "e" area, and the "f" area and are not formed in the "a" area, the "c" area, and the "d" area. Assuming that an opening area of the distribution holes 4a per a unit area of the distribution pipe 4 is the distribution hole density, distribution hole densities in the "b" area and the "e" area are set larger than the distribution hole density in the "f" area. Incidentally, distribution hole densities in the a, c, and "d" areas are zero. Note that axial direction widths of the a, b, and "c" areas are set to a width obtained by equally dividing the axial direction area between the top end of the heat chamber 1 and the top end of the inlet pipe 9 into three parts, that is, L2/3 and an axial direction with of the "e" area is also set to L2/3.

A part of the mixed gas, which has flown into the inner chamber 7 from the inlet pipe 9, flows into the outer chamber 8 via the distribution holes 4a in the "b" area. The remaining mixed gas flows to a void in the inner chamber 7 between the inlet pipe 9 and the distribution pipe 4 (hereinafter referred to as an outer peripheral void of the inlet pipe 9) and flows into the outer chamber 8 from the distribution holes 4a in the "e" area and the "f" area. Here, if distribution holes are formed in the "c" area, the mixed gas, which should be caused to flow into the outer peripheral void of the inlet pipe 9, flows to the outer chamber 8 via the distribution holes in the "c" area. As a result, the amount of the mixed gas flowing into the outer peripheral void of the inlet pipe 9 is made insufficient. However, in this embodiment, since the distribution holes 4a are not formed in the "c" area, it is possible to supply the mixed gas sufficiently to the outer peripheral void of the inlet pipe 9. Therefore, it is possible to uniformalize the axial direction distribution of the mixed gas pressure in the outer chamber 8 in the area from the arrangement section of the baffle board 10 to the base end of the heat chamber 1 by appreciately setting the distribution hole density in "f" area. As a result, it is possible to uniformalize an axial direction distribution of the jet quantity of the mixed gas from the burner ports 1a of the heat chamber 1 in this area.

However, in a portion closer to the baffle board 10 in the area from the arrangement section of the baffle board 10 to the base end of the combustion chamber 1, the predominant flow of the mixed gas in the outer peripheral void of the inlet pipe 9 changes to a flow in the axial direction. Thus, the mixed gas flows into the outer chamber 8 from the distribution holes 4a less easily and mixed gas pressure in the portion of the outer chamber 8 closer to the arrangement section of the baffle board 10 tends to be low. In this embodiment, the distribution hole density in the "e" area near the arrangement section of the baffle board 10 is set large. Therefore, the mixed gas flows into the outer chamber 8 from the distribution holes 4a in the "e" area easily. As a result, drop in mixed gas pressure in the portion of the outer chamber 8 closer to the arrangement section of the baffle board 10 is compensated.

The mixed gas, which has flown into the outer chamber 8 from the distribution holes 4a in the "b" area, flows toward the base end side of the heat chamber 1 in the outer chamber 8. Here, in the "d" area, the velocity of flow of the mixed gas flowing to the outer peripheral void of the inlet pipe 9 is high and the pressure in the outer peripheral void of the inlet pipe 9 tends to be negative. Therefore, if the distribution holes 4a are formed in the "d" area, the mixed gas in the outer chamber 8 is sucked into the outer peripheral void of the inlet pipe 9. However, in this embodiment, since the distribution holes 4a are not formed in the "d" area, the mixed gas, which has flown into the outer chamber 8 from the distribution holes 4a in the "b" area, flows toward the base end side of the heat chamber 1 in the outer chamber 8 without being sucked into the outer peripheral void of the inlet pipe 9. In this case, if the mixed gas flows directly to the base end in the outer chamber 8, pressure in the "d" area of the outer chamber 8 falls. However, since the mixed gas is prevented from further flowing toward the base end side by the baffle board 10. Thus, pressure distribution of the mixed gas in a portion of the outer chamber 8 between the arrangement section of the baffle board 10 and the top end of the heat chamber 1 is uniformalized easily.

However, if the burner ports 1a are present in the "b" area, the mixed gas, which has flown in from the distribution holes 4a in the "b" area, proceeds straight to the outside in the radial direction toward the burner ports in the "b" area directly. As a result, the jet quantity of the mixed gas from the burner ports in the "b" area is made excessive. Here, at respective ends on the base end side and the top end side of the heat chamber 1, the burner ports 1a are not formed in order to prevent flames from touching the flange sections 3a and 6a to generate CO or prevent the flange sections 3a and 6a from deteriorating. In this embodiment, a leading end of a burner port forming area of the heat chamber 1 is located in the "c" area. The "b" area is a non-burner port portion where no burner port 1a is present. Thus, the mixed gas, which has flown in from the distribution holes 4a in the "b" area, is prevented from proceeding to the outside in the radial direction directly and jetting from the burner ports 1a. Therefore, the axial direction distribution of the jet quantity of the mixed gas from the burner ports 1a of the heat chamber 1 between the arrangement section of the baffle board 10 and the top end of the heat chamber 1 is uniformalized in conjunction with pressure equalization by the function of the baffle board 10. Note that the leading end of the burner port forming area of the heat chamber 1 may be located in the "d" area. In addition, dummy burner ports 1c of a blank hole shape are formed in non-burner port portion at the respective ends of the heat chamber 1 because of a reason relating to formation such as uniformalization of a shrinking percentage at the time of firing of the ceramics combustion plate 1b.

Here, the portion of the outer chamber 8 between the arrangement section of the baffle board 10 and the top end of the heat chamber 1 and the portion of the outer chamber 8 between the arrangement section of the baffle board 10 and the base end of the heat chamber 1 are not blocked completely but communicate with each other via a gap between the baffle board 10 and the inner peripheral surface of the heat chamber 1. Thus, a large pressure difference is not caused on both sides of the baffle board 10. If the distribution hole density in the "b" area is set appropriately such that mixed gas pressure in the outer chamber 8 in the area from the arrangement section of the baffle board 10 to the top end of the heat chamber 1 and a mixed gas pressure in the outer chamber 8 in the area from the arrangement section of the baffle board 10 to the base end of the heat chamber 1 are substantially equal, it is possible to uniformalize the axial direction distribution of the jet quantity of the mixed gas from the burner ports 1a of the heat chamber 1 over the entire length of the heat chamber 1. It is possible to obtain uniform combustion over an entire area of the burner port forming area of the heat chamber 1 in conjunction with uniformalization of the peripheral direction distribution of the jet quantity of the mixed gas from the burner ports 1a of the heat chamber 1 due to a rectifying action of the inlet pipe 9. Note that, in order to supply the mixed gas to the burner ports 1a, which are present in the area from the arrangement section of the baffle board 10 to the top end of the heat chamber 1, through the distribution hoes 4a in the limited area of the "b" area, it is necessary to set the distribution hole density in the "b" area larger than the distribution hole density in the "f" area.

Incidentally, it is also conceivable to form the distribution holes 4a from the "b" area to the "a" area. Here, a portion of the "a" area in the inner chamber 7 is a portion where the mixed gas flowing out in the axial direction from the inlet pipe 9 comes to a dead end. Thus, pressure of the mixed gas is extremely high in the portion. Therefore, if the distribution holes 4a are formed in the "a" area, a large amount of the mixed gas flows to the outer chamber 8 in the "a" area and cannot be supplied to the outer peripheral void of the inlet pipe 9 sufficiently. In this embodiment, since the distribution holes 4a are not formed in the "a" area, such deficiency never occurs.

The distance L3 between the top end of the inlet pipe 9 and the baffle board 10 is set in the range of 80 to 100% of the distance L2 between the top end of the inlet pipe 9 and the top end of the heat chamber 1 as described above. A reason for this is as described below. When the distance L3 is shorter than the distance in the range, a portion, where a pressure of the outer peripheral void of the inlet pipe 9 tends to be negative, enters an area between the arrangement section of the baffle board 10 and the base end of the heat chamber 1. Thus, mixed gas pressure in the portion of the outer chamber 8 closer to the arrangement section of the baffle board 10 in this area falls. On the other hand, when the distance L3 is longer than the distance in the range, an axial direction length in the portion of the outer chamber 8 between the arrangement section of the baffle board 10 and the top end of the heat chamber 1 is made too long. Thus, the axial direction distribution of the mixed gas pressure in this portion of the outer chamber 8 is made non-uniform easily.

Note that, in the embodiment, no distribution holes 4a are formed in the a, c, and "d" areas. However, a few distribution holes 4a may be formed in the a, c, and "d" areas as long as distribution hole density is a very small value near zero. Although the cylindrical burner in the embodiment is suitable as a burner for a heat source of a spiral water pipe heat exchanger, an application of the invention is not limited to this.

Claims

A cylindrical burner comprising:

a heat chamber, in a peripheral surface of which a plurality of burner ports are opened;

a base plate having an inlet port mounted at a base end of the heat chamber;

a cover plate mounted at a top end of the heat chamber; and

a distribution pipe, which partitions the space in the heat chamber into inner and outer two chambers, extending in an axial direction from the base plate to the cover plate in the inside of the heat chamber,

the cylindrical burner causing the mixed gas to flow into an inner chamber on an inner side of the distribution pipe from the inlet port and causing the mixed gas, which has flown into the inner chamber, to flow into an outer chamber on an outer side of the distribution pipe via a plurality of distribution holes formed in the distribution pipe, wherein

an inlet pipe, which is connected to the inlet port and extends in the axial direction to a position closer to a top end of the heat chamber, is arranged in the inner chamber, an annular baffle board, which is located in a section a predetermined distance apart from a top end of the inlet pipe to a base end side of the distribution pipe and narrows a gap between an outer periphery of the distribution pipe and an inner peripheral surface of the heat chamber, is arranged in the outer periphery of the distribution pipe, and

assuming that an opening area of distribution holes per a unit area of the distribution pipe is a distribution hole density, the distribution hole density falls to zero or a very small value near zero in a portion closer to the top end of the inlet pipe in an axial direction area between the top end of the inlet pipe and the top end of the heat chamber and a portion between the top end of the inlet pipe and the portion near the arrangement section of the baffle board.
The cylindrical burner according to claim 1, wherein an axial direction leading end in a burner port opening area of the heat chamber is located in a portion closer to the top end of the inlet pipe in the axial direction area between the top end of the inlet pipe and the top end of the heat chamber or a portion between the top end of the inlet pipe and the portion near the arrangement section of the baffle board.
The cylindrical burner according to claim 1 or 2, wherein a distribution hole density in the portion near the arrangement section of the baffle board is larger than a distribution hole density in the portion between the base end of the heat chamber and the portion near the arrangement section of the baffle board.
The cylindrical burner according to claim 1, 2 or 3, wherein the axial direction area between the top end of the inlet pipe and the top end of the heat chamber is sectioned into three portions, namely, a portion closer to the top end of the inlet pipe, a middle portion, and a portion closer to the top end of the heat chamber, a distribution hole density in the portion closer to the top end of the heat chamber is zero or a very small value near zero, and distribution holes are concentratedly formed in the middle portion.
The cylindrical burner according to any one of claims 1 to 4, wherein a distance between the top end of the inlet pipe and the top end of the heating chamber is set in a range of 15 to 35% of a total length of the heat chamber and a distance between the top end of the inlet pipe and the baffle board is set in a range of 80 to 100% of the distance between the top end of the inlet pipe and the top end of the heat chamber.