COMBUSTION APPARATUS

In a combustion apparatus that includes a burner constituted by a burner body, an inside of which an air-fuel mixture is supplied to and one surface of which is made into an open surface, and a combustion plate covering the open surface of the burner body, and a combustion box enclosing a combustion space of the air-fuel mixture ejecting from the combustion plate, an offset part that is positioned at a portion which is away from the swelling part in an inflow direction of the air-fuel mixture to the inner chamber and does not oppose to a tip part(s) of the ignition electrode(s) through the combustion plate is provided with the opposite wall of the burner body and the offset part offsets to a combustion-plate side so that a distance between the offset part and the combustion plate becomes shorter than that between the combustion plate and a general part of the opposite wall except the swelling part and the offset part.

TECHNICAL FIELD

The invention relates to a combustion apparatus that includes a burner constituted by a burner body, an inside of which an air-fuel mixture is supplied to and one surface of which is made into an open surface, and a combustion plate covering the open surface of the burner body, and a combustion box enclosing a combustion space of the air-fuel mixture ejecting from the combustion plate.

BACKGROUND ART

Conventionally, as this kind of the combustion apparatus, there has been known the combustion apparatus in which an ignition electrode faced to the combustion plate is mounted on a predetermined side plate of the combustion box and a swelling part, an inside of which becomes an inflow chamber of the air-fuel mixture and which swells in a direction away from the combustion plate, is provided with a part of an opposite wall of the burner body, which opposes to the combustion plate at a distance (See Patent document No. 1, for example). In this combustion apparatus, on a premise that a direction from the predetermined side plate of the combustion box to a side plate, opposite to the predetermined side plate, of the combustion box is a predetermined direction, the air-fuel mixture is configured to flow in the inflow chamber with a direction component along the predetermined direction.

REFERENCE

SUMMARY OF INVENTION

Technical Problem

In the above-mentioned combustion apparatus, the air-fuel mixture flowing from the inflow chamber to a space between the opposite wall of the burner body and the combustion plate is liable to go forward in an inflow direction of the air-fuel mixture. Then, since the inflow direction of the air-fuel mixture has a direction component going from the side plate of the combustion box, on which the ignition electrode is mounted, to the side plate opposite to the side plate previously mentioned, the air-fuel mixture is not sufficiently distributed to a part of the combustion plate opposite to a tip part of the ignition electrode, at which spark discharge occurs. As a result, an ignition performance is sometimes deteriorated.

In the light of the above-mentioned problem, an object of the invention is to provide a combustion apparatus that can improve the ignition performance.

Solution to Problem

In order to accomplish the object, the invention presupposes a combustion apparatus that includes a burner constituted by a burner body, an inside of which an air-fuel mixture is supplied to and one surface of which is made into an open surface, and a combustion plate covering the open surface of the burner body; and a combustion box enclosing a combustion space of the air-fuel mixture ejecting from the combustion plate, wherein an ignition electrode(s) faced to the combustion plate is mounted on a predetermined side plate of the combustion box and a swelling part, an inside of which becomes an inflow chamber of the air-fuel mixture and which swells in a direction away from the combustion plate, is provided with a part of an opposite wall of the burner body, which opposes to the combustion plate at a distance, and wherein on a premise that a direction from the predetermined side plate of the combustion box to a side plate, opposite to the predetermined side plate, of the combustion box is a predetermined direction, the air-fuel mixture is configured to flow in the inflow chamber with a direction component to the predetermined direction. In the combustion apparatus, an offset part that is positioned at a portion which is away from the swelling part in an inflow direction of the air-fuel mixture to the inflow chamber and does not oppose to a tip part(s) of the ignition electrode(s) through the combustion plate is provided with the opposite wall of the burner body and the offset part offsets to a combustion-plate side so that a distance between the offset part and the combustion plate becomes shorter than that between the combustion plate and a general part of the opposite wall except the swelling part and the offset part.

According to the invention, a flow resistance of a space between the opposite wall of the burner and the combustion plate increases at the offset part that is away from the swelling chamber in the inflow direction of the air-fuel mixture to the inflow chamber. Therefore, a flow of the air-fuel mixture forward in the inflow direction from the inflow chamber is moderately suppressed. According to this, the air-fuel mixture is sufficiently distributed to the part of the combustion plate which is opposite to the tip part(s) of the ignition electrode(s), at which spark discharge occurs, and an ignition performance is improved.

In the invention, it is desirable that an inclining part, which is positioned between the swelling part and the offset part and a distance from the combustion plate of which continuously decreases toward the offset part, is provided with the opposite wall. Here, if a step is provided at an end portion of the offset part near the swelling part, in a state where a supply amount of the air-fuel mixture to the burner body is large, due to pressure loss at the step, there is possibility that the air-fuel mixture is not sufficiently distributed to a space between the offset part and the combustion plate. By provision of the inclining part as above-mentioned, the pressure loss decreases and even in the state where the supply amount of the air-fuel mixture to the burner body is large, the air-fuel mixture can be sufficiently distributed to the space between the offset part and the combustion plate.

DESCRIPTION OF EMBODIMENTS

A combustion apparatus, which is shown inFIGS.1through5, of an embodiment of the invention includes a totally-aerated burner1that is constituted by a burner body11, an inside of which an air-fuel mixture (a mixed gas of a fuel gas and a primary air) is supplied to and a lower surface as one surface of which is made into an open surface111, and a combustion plate12covering the open surface111of the burner body11; and a combustion box2enclosing a combustion space of the air-fuel mixture ejecting from the combustion plate12. At an upper end of the combustion box2, a box flange part22that is fitted to a body flange part112enclosing the open surface111of the burner body11by a screw21is provided. In the combustion box2, a heat exchanger3for hot-water supply is housed.

The heat exchanger3is constituted by a fin-tube type heat exchanger that includes a plurality of fins31and a plurality of heat-absorbing tubes32piercing the fins31. At an outside of each of side plates23,24of one side and the other side in lateral direction of the combustion box2, a plurality of U-shaped vent pipes33connecting adjacent two heat-absorbing tubes32,32are provided and all of the heat-absorbing tubes32are connected in series. A pipe34with which a water inlet34ais provided at an end portion is connected to the heat-absorbing tube32at an upstream end.

Referring toFIG.5, at an inside of a part of a side plate25of a front side of the combustion box2, which is positioned above the heat exchanger3, three water passages, i.e., a first water passage41, a fifth water passage45, and a ninth water passage49, which consist of a pipe, are disposed in sequence from below so as to come into contact with the side plate25. Also, at an inside of a part of a side plate26of a rear side of the combustion box2, which is positioned above the heat exchanger3, three water passages, i.e., a third water passage43, a seventh water passage47, and an eleventh water passage4ii, which consist of a pipe, are disposed in sequence from below so as to come into contact with the side plate26. Additionally, at an outside of the side plate23at one side in the lateral direction of the combustion box2, as shown inFIGS.1,4, a connecting pipe35connecting the heat-absorbing tube32at a downstream end of the heat exchanger3to the first water passage41is provided and at a part of the side plate23, which is positioned above the heat exchanger3, a fourth water passage44connecting the third water passage43and the fifth water passage45, an eighth water passage48connecting the seventh water passage47and the nineth water passage49, and a twelfth water passage412connected to the eleventh water passage411are provided. Further, with the side plate24of the other side in the lateral direction of the combustion box2, as shown inFIGS.2,4, a second water passage42connecting the first water passage41and the third water passage43, a sixth water passage46connecting the fifth water passage45and the seventh water passage47, and a tenth water passage410connecting the nineth water passage49and the eleventh water passage411, each of which is positioned above the heat exchanger3, are provided. Each of the second, sixth, and tenth water passages42,46,410, and each of the fourth, eighth, and twelfth water passages44,48,412are constituted by cavities inward in the lateral direction, which are formed at each of the side plates24,23, and lids41fitted to the outside surface of each of the side plates24,23so as to cover the cavities. Water heated in the heat exchanger3flows in the first water passage41through the twelfth water passage412in sequence and are supplied from a hot water outlet42provided with an end portion of the twelfth water passage412to a hot water pipe, not shown, connecting to the hot water outlet42. Then, each of the side plates23through26of the combustion box2are configured to be cooled by water flowing in the first water passage41through the twelfth water passage412.

Furthermore, on the side plate25of the front side of the combustion box2, electrode parts5having a pair of ignition electrodes51,51protruding in the combustion box12and facing to the combustion plate12, and a pair of flame rods52,52are provided. In this connection, one of the ignition electrodes51,51is applied to high voltage and the other is grounded. Spark discharge is performed between tip parts of the ignition electrodes51,51and the air-fuel mixture ejecting from the combustion plate12is ignited. Also, with the electrode parts5, an inspection window53through which visual inspect in the combustion box2is possible is additionally provided.

Next, detailed explanation regarding the burner1will be made. With reference also toFIG.6, a combustion plate12has a burner frame121with a shape of a picture frame and an air-fuel mixture permeable body123covering an opening122enclosed by the burner frame121from a burner-body11side (from above), through which the air-fuel mixture permeates. The air-fuel mixture permeable body123can be constituted by woven or nonwoven fabric of a heat-resistant fiber such as a metal fiber and the like, or a porous sintered compact and the like. On a rear surface (upper surface), which is a surface of an upstream side in a flowing direction of the air-fuel mixture, of the air-fuel mixture permeable body123, a distribution plate124in which a plurality of distribution holes124aare opened is overlapped. Then, the air-fuel mixture supplied in the burner body11ejects from the opening122through the distribution holes124aand the air-fuel mixture permeable body123, and totally aerated combustion (combustion unnecessary for secondary air) is performed. In this connection, a sectional shape along a front-to-back direction of the opening122, as shown inFIG.5, curves into an arcuate shape and the sectional shapes of the air-fuel mixture permeable body123and the distribution plate124similarly curves into the arcuate shape along the front-to-back direction.

The burner frame121has an opening peripheral edge part1211around the opening122, a side plate part1212bending from the opening peripheral edge part1211to the burner-body11side (upward), and a frame flange part1213outwardly extending from an upper end of the side plate part1212. With a portion of the opening peripheral edge part1211, which is close to an inner circumference, a squeezed part1211athat comes down by one step is provided. A peripheral edge part of the air-fuel mixture permeable body123is overlapped on the squeezed part1211a. In a state where the distribution plate124is overlapped on the rear surface of the air-fuel mixture permeable body123, the combustion plate12is assembled by spot-welding a peripheral part of the distribution plate124to a portion of the opening peripheral part1211of an outside of the squeezed part1211aat a constant distance. The frame flange part1213is sandwiched between the body flange part112and the box flange part22. Additionally, a packing6is interposed between the frame flange part1213and the body flange part112, and a sealing property between the burner body11and the combustion plate12is secured. In this connection, the packing6has a portion outwardly extending beyond the frame flange part1213. This portion is interposed between the body flange part112and the box flange part22, and the sealing property between the body flange part112and the box flange part22is secured.

The burner body11has a swelling part1131that is provided with a part of an opposite wall113opposite to the combustion plate12at a distance and swells upward, as a direction away from the combustion plate12. An inside of the swelling part1131is made into an inflow chamber1131aof the air-fuel mixture. Additionally, in the swelling part1131, on a premise that one side in lateral direction of the combustion box2, at which the side plate23exists, is defined to be a right side, an inflow port1131bis opened diagonally in front and rightward. Further, the air-fuel mixture from the fan, not shown, is configured to flow in the inflow chamber1131athrough the inflow port1131bwith a rear direction component as a direction from the side plate25disposed at a front side of the combustion box2, on which the electrode parts5, i.e., the ignition electrodes51,51, are mounted, to the side plate26disposed at a rear side and opposite to the side plate25. Specifically, the air-fuel mixture flows diagonally in rear and leftward and the flowing direction of the air-fuel mixture is represented by an arrow “a” as shown inFIG.3.

In this case, the air-fuel mixture flowing to a space between the opposite wall113of the burner body11and the combustion plate12is liable to go forward in an inflow direction of the air-fuel mixture from the inflow chamber1131a. Further, since the inflow direction of the air-fuel mixture has a direction component going from the side plate25of the front side of the combustion box2, on which the ignition electrode51is mounted, to the side plate26of the rear side opposite to the side plate25, the air-fuel mixture flowing in the inflow direction as previously mentioned is not sufficiently distributed to a part of the combustion plate12opposite to tip parts of the ignition electrodes51,51, at which spark discharge occurs. As a result, there is a possibility that an ignition performance is sometimes deteriorated.

Then, in the embodiment, with the opposite wall113of the burner body11, an offset part1132that is positioned at a portion which is away from the swelling part1131in the inflow direction (diagonally in rear and leftward) of the air-fuel mixture to the inflow chamber1131ais provided. The offset part1132offsets to the combustion plate 12-side so that a distance between the offset part1132and the combustion plate12becomes shorter than that between the combustion plate12and a general part1133of the opposite wall113except the swelling part1131and the offset part1132. In this connection, in the embodiment, a part of the opposite wall113opposite to the tip parts of the ignition electrodes51,51through the combustion plate12, i.e., a part of the opposite wall113positioned just above the tip parts of the ignition electrodes51,51, is a part of the swelling wall1131. Therefore, the offset part1132is positioned at a portion that does not oppose to the tip parts of the ignition electrodes51,51through the combustion plate12. Additionally, in the embodiment, the offset part1132is provided to range to a part of the opposite wall113, which is separated leftward from the swelling part113.

According to the above-mentioned constitution, a flow resistance of the space between the opposite wall113of the burner body11and combustion plate12becomes large at the offset part1132that is away from the swelling part1131in the inflow direction of the air-fuel mixture to the inflow chamber1131a. Therefore, a flow of the air-fuel mixture, which goes forward in the inflow direction from the inflow chamber1131a, is moderately suppressed. Due to this, the air-fuel mixture is sufficiently distributed to even a part of the combustion plate12opposite to the tip parts of the ignition electrodes51,51, at which the spark discharge occurs, and the ignition property is improved.

In this connection, if there is a step that exists at an end portion of the offset part1132, which comes close to the swelling part1131, in a state where a supply amount of the air-fuel mixture to the burner body11is large, due to pressure loss at the step, there is a possibility that the air-fuel mixture will not be sufficiently distributed to the space between the offset part1132and the combustion plate12.

Then, in the embodiment, as shown inFIGS.4,5, with the opposite wall113of the burner body11, an inclining part1134that is positioned between the swelling part1131and the offset part1132and of which a distance from the combustion plate12continuously decreases toward the offset part1132is provided. Due to provision of the inclining part1134, the pressure loss decreases. Therefore, even at the state where an amount of the air-fuel mixture to the burner body11is large, the air-fuel mixture can be sufficiently distributed to the space between the offset part1132and the combustion plate12.

In this connection, in the embodiment, the general part1133adjacent to the swelling part113is provided between the swelling part1131and offset part1132and the inclining part1134is provided between the general part1133and the offset part1132. It is also possible that only the inclining part1134is provided between the swelling part1131and the offset part1132without provision of the general part1133.

Though the embodiment of the invention is explained with reference to the drawings in the above, the invention is not limited to the embodiment. For example, the part of the opposite wall113that is positioned just above the tip parts of the ignition electrodes51,51may be a part of the general part1133adjacent to the swelling part1131, which is different from the above-mentioned embodiment. Further, in the above-mentioned embodiment, though a pair of the ignition electrodes51,51are provided, only one ignition electrode is provided and the spark discharge may be performed between a tip part of the ignition electrode and the combustion plate. Furthermore, in the above-mentioned embodiment, though the lower surface of the burner body11is made into the open surface111, the invention is similarly applicable to a combustion apparatus in which an upper surface of the burner body11is made into the open surface111and the combustion box2is disposed over the burner1.

EXPLANATION OF SYMBOLS