JP7479268B2 - Combustion equipment - Google Patents

Description

The present invention relates to a tension combustion type combustion device in which a combustion fan for supplying combustion air to a burner is positioned downstream in the flow direction of the combustion exhaust gas generated from the burner.

Conventionally, a combustion device is known in which burners, each long in one direction, are arranged in a row in a direction perpendicular to the long direction inside a rectangular cylindrical combustion housing, and a heat shield is provided on the inner surface of the outer wall of the combustion housing with a gap between them (see, for example, Patent Document 1). In this device, a combustion fan for supplying combustion air to the burners is arranged upstream of the burners.

Patent Application No. 2016-125684

In addition to combustion devices in which the combustion fan is located upstream of the burner, there are also combustion devices called tension combustion types in which the combustion fan is located downstream of the burner.

In the case of a combustion device in which the combustion fan is located downstream of the combustion chamber, negative pressure acts uniformly on the entire combustion chamber inside the combustion housing. This means that cooling air cannot be directed at the outer wall or heat shield of the combustion housing, which can lead to insufficient cooling and the outer wall or heat shield of the combustion housing may overheat.

One possible solution is to increase the overall volume of air by increasing the rotation speed of the combustion fan, but this can lead to a deterioration in combustion conditions and reduced thermal efficiency due to the supply of excessive combustion air or large amounts of air flowing.

In view of the above, the present invention aims to provide a tension combustion type combustion device that can prevent overheating by promoting cooling of the outer wall and heat shield of the combustion case while suppressing deterioration of the combustion state and reduction in thermal efficiency.

In order to achieve this objective, the present invention provides a tensile combustion device in which a heat shield plate is provided on the inner surface of a combustion housing having a combustion chamber that houses a burner inside, and a combustion fan for supplying combustion air to the burner is arranged downstream in the flow direction of the combustion exhaust gas generated from the burner, the device being characterized by having a closed space portion formed in the partial area between the outer wall of the combustion housing and the heat shield plate by the heat shield plate abutting against the periphery of a partial area of the outer wall of the combustion housing, an air inlet hole formed in the outer wall of the combustion housing at a position that forms the closed space portion and that introduces air into the closed space portion, and an outlet opening formed in the heat shield plate at a position that forms the closed space portion and that allows the air in the closed space portion to flow out to the combustion chamber.

With the above configuration, the closed space formed by a portion of the outer wall of the combustion housing and the heat shield is designed so that fresh outside air passes through the inside via the air inlet holes and the outflow openings. The outside air cools the outer wall of the combustion housing and the heat shield at the location of the closed space.

The portion of the outer wall of the combustion housing that forms the closed space can be set at any desired position. Moreover, the closed space is closed on all sides by the contact between the outer wall of the combustion housing and a heat shield. This closed space is cooled by introducing outside air, which is expected to have a high cooling effect.

This allows, for example, a closed space to be provided in the hottest areas of the heat shield and the outer wall of the combustion housing, allowing those areas to be cooled efficiently with a small amount of outside air. Therefore, by introducing a relatively small amount (the minimum necessary amount) of outside air and concentrating cooling on the areas that require it most, it is possible to minimize the deterioration of the combustion state and the decrease in thermal efficiency caused by the introduction of outside air.

The combustion device of the present invention is a tension combustion type in which the combustion fan is located downstream of the burner, so the inside of the combustion case is under negative pressure during burner combustion. This prevents combustion exhaust from leaking out of the combustion case through the air inlet holes. And by setting the size and number of the air inlet holes, the desired amount of air can be accurately introduced.

As described above, the present invention can minimize the effects of deterioration of the combustion state and reduced thermal efficiency, while still providing sufficient and efficient cooling.

A specific embodiment of the closed space is to have the heat shield in the position corresponding to the partial area bulge toward the combustion chamber and have the outer wall of the combustion housing abut against the periphery of the bulging portion.

As a further preferred embodiment, the closed space is formed inside the first protrusion by a first protrusion that protrudes outward from the partial area of the outer wall of the combustion housing and the heat shield that abuts against the periphery of the first protrusion of the outer wall of the combustion housing.

The first protrusion that constitutes the closed space bulges outward from the combustion housing, so the closed space is formed away from the burner flame and is less susceptible to the heat of the burner flame.

The present invention is also characterized in that the heat shield has a second protrusion that bulges into the closed space at a position corresponding to the first protrusion.

The second convex portion is shaped to bulge into the closed space, which keeps the heat shield away from the burner flame at the closed space, further preventing the heat shield from overheating.

The present invention is also characterized in that the outlet opening is formed downstream of the burner and downstream of the air introduction hole.

This allows the flow of external air that enters the closed space through the air inlet hole and flows through the outlet opening toward the combustion chamber to follow the flow of the combustion exhaust, allowing the smooth flow of external air to efficiently cool the outer wall and heat shield of the combustion housing.

The present invention is also characterized in that the heat shield has an inclined piece that inclines from the downstream end of the outlet opening toward the upstream side of the closed space in a direction approaching the outer wall of the combustion case.

The outside air that enters the closed space through the air inlet hole and heads toward the outflow opening is guided against the inclined piece and flows into the combustion chamber through the outflow opening. The inclined piece is inclined in a direction approaching the outer wall of the combustion housing toward the upstream side of the closed space. As a result, the outside air that is guided by the inclined piece and enters the combustion chamber comes into contact at an acute angle with the combustion exhaust flowing inside the combustion chamber, and continues to flow along the heat shield even after entering the combustion chamber. This allows the heat shield downstream of the outflow opening to be cooled as well.

The present invention is also characterized in that it includes a cover plate that is continuous with the heat shield plate, is located upstream of the closed space and downstream of the burner, and covers the inner surface of the combustion box.

In tension combustion equipment, the combustion air is pulled by the fuel gas ejected from the burner's flame port, which can easily cause turbulence due to eddies, and the combustion exhaust may come into contact with the outer wall of the combustion housing downstream of the burner, causing the outer wall to overheat.

According to the present invention, by providing a cover plate, it is possible to prevent the combustion air from coming into contact with the outer wall of the combustion housing even if the flow of the combustion exhaust is disturbed, and it is possible to suppress the temperature rise of the outer wall of the combustion housing.

1 is an explanatory perspective view showing a main part of a combustion device according to an embodiment of the present invention; FIG. 2 is an explanatory cross-sectional view of a combustion housing and a heat exchange housing in the combustion apparatus of the present embodiment. FIG. FIG. FIG. 13 is an explanatory perspective view showing a modified example of the second protrusion.

One embodiment of the present invention will be described with reference to the drawings. The combustion device of this embodiment is used as a heat source unit for a water heater, and as shown in Figure 1, it has a combustion housing 1 and a heat exchange housing 2.

As shown in FIG. 2, a combustion chamber 3 is formed inside the combustion housing 1. A plurality of burners 4 having a flame port 4a at the upper end are provided inside the combustion chamber 3. Each burner 4 is formed in an elongated shape that is elongated in one direction (referred to as the front-rear direction in this embodiment), and the burners 4 are arranged side by side in a direction perpendicular to the longitudinal direction (referred to as the lateral direction in this embodiment).

The heat exchanger 5 for supplying hot water, which is the object to be heated, is housed inside the heat exchanger housing 2. A combustion fan (not shown) is connected to the top of the heat exchanger housing 2 (downstream in the direction of the flow of the combustion exhaust air).

The combustion fan forcibly flows in the direction of exhaust the combustion exhaust gas generated by the combustion of the burner 4. At this time, the combustion chamber 3 becomes negative pressure, and combustion air is drawn from the outside into an air supply chamber (not shown) formed below the burner 4.
Since the combustion air is supplied in a pulled manner in this manner, the combustion apparatus of this embodiment is called a tension combustion type combustion apparatus.

A gap is formed between each adjacent burner 4 to allow ventilation. The air below each burner 4 is supplied to the burner 4 as secondary air as it flows through these gaps toward the combustion chamber 3.

The combustion box 1 is formed in a roughly rectangular cylindrical shape and is provided with a pair of first combustion section outer walls 6 located on the front and rear sides and facing each other in an upright state, and a pair of second combustion section outer walls 7 located on the left and right sides and facing each other in an upright state. Both first combustion section outer walls 6 are located on the front and rear end sides of each burner 4, and both second combustion section outer walls 7 are located on the left and right sides of each burner 4.

As shown in Figures 1 and 2, the base end of an ignition electrode 8 that ignites the burner 4 and the base end of a flame rod 9 that detects the combustion of the burner 4 are supported on one of the first combustion section outer walls 6.

The heat exchange housing 2 is formed in a generally rectangular tubular shape continuing from the combustion housing 1, and includes a first heat exchange section outer wall 10 formed integrally with and continuing from the upper edge of the first combustion section outer wall 6, and a second heat exchange section outer wall 11 connected to the upper edge of the second combustion section outer wall 7. The second heat exchange section outer wall 11 is formed in a tubular shape with its front and rear ends connected to the left and right ends of the first heat exchange section outer wall 10.
As shown in FIGS. 2 and 3 , the combustion chamber 3 is provided with a heat shield plate 12 that covers the inner surface of the first combustion section outer wall 6 , and a cover wall plate 13 that is continuous with the heat shield plate 12 .

A first protrusion 14 that bulges outward is formed in a portion of the first combustion section outer wall 6 of the combustion housing 1. The first protrusion 14 is located above the burner 4 (downstream of the burner 4), and the combustion chamber 3 side of the first protrusion 14 is covered by a heat shield plate 12. The first protrusion 14 is formed in a substantially rectangular shape, as shown in FIG. 3.

The heat shield 12 covers the inner surface side of the first combustion section outer wall 6 and abuts against the periphery of the first protrusion 14 from the combustion chamber 3 side. As a result, a closed space 15 is formed in the recess on the inner surface side of the first combustion section outer wall 6 formed by the first protrusion 14, with the outer periphery of the first protrusion 14 closed by the heat shield 12 (see Figure 4).

The heat shield 12 at a position corresponding to the closed space 15 is formed with a second protrusion 16 that bulges toward the inside of the closed space 15. The second protrusion 16 is formed in a substantially rectangular shape that is slightly smaller than the first protrusion 14. As shown in Figures 2 and 3, the second protrusion 16 is a recess when viewed from the combustion chamber 3 side.

As shown in FIG. 1, a plurality of air introduction holes 17 are formed in the first combustion section outer wall 6 in the portion where the first protrusion 14 is formed. The air introduction holes 17 are provided to penetrate the first combustion section outer wall 6 and introduce outside air into the closed space 15.

As shown in FIG. 3, an outflow opening 18 is formed in the heat shield 12 at a position above the second protrusion 16 that covers the closed space 15. The outflow opening 18 is provided to allow air to pass through the heat shield 12 and flow from the closed space 15 into the combustion chamber 3. The outflow opening 18 is disposed above the air introduction hole 17 (downstream in the flow direction of the combustion exhaust gas).

Furthermore, as shown in FIG. 4, an inclined piece 19 is provided on the upper edge of the outflow opening 18. The inclined piece 19 can be formed at the same time as the outflow opening 18 by bending the heat shield 12 at a position corresponding to the outflow opening 18 toward the inside of the closed space 15 when cutting out the outflow opening 18 from the heat shield 12, and thus freeing it. If the outflow opening 18 is horizontally elongated, the inclined piece 19 can also be formed horizontally elongated, so that the inclined piece 19 acts like a reinforcing rib to improve the strength of the heat shield 12.

The first combustion section outer wall 6 and the heat shield plate 12 form a closed space 15, and the air inlet holes 17 and the outlet openings 18 allow outside air to pass through the inside of the closed space 15, cooling the first combustion section outer wall 6 and the heat shield plate 12 in the part that forms the closed space 15. In other words, the part where the closed space 15 is provided can be cooled in a focused manner.

As mentioned above, the combustion device of this embodiment employs a tension combustion system. As the hot water heater is a tension combustion system, the combustion chamber 3 is under negative pressure during combustion operation (when the combustion fan is operating). Therefore, in the closed space 15, a flow occurs from the air inlet hole 17 to the outflow opening 18, so that the combustion exhaust gas in the combustion chamber 3 does not leak from the air inlet hole 17.

The closed space 15 can be formed to an appropriate size using the first protrusion 14 and the heat shield 12, and the amount of air introduced into the closed space 15 can be easily set by the size and number of the air introduction holes 17. By providing the closed space 15 at a desired position on the first combustion section outer wall 6, it is possible to selectively cool that position.

Therefore, a closed space 15 is provided in the hottest part of the first combustion section outer wall 6, and the amount of air introduced from the air inlet hole 17 is set to the minimum amount required for cooling. This makes it possible to efficiently cool the first combustion section outer wall 6 and the heat shield plate 12 while keeping the amount of air flowing into the combustion chamber 3 from the outside small.

Furthermore, when the air introduced into the closed space 15 flows from the outflow opening 18 toward the combustion chamber 3, it comes into contact with an inclined piece 19 provided along the upper edge of the outflow opening 18 and is guided diagonally upward. This allows the air entering the combustion chamber 3 from the closed space 15 to flow between the combustion exhaust and the heat shield 12 in parallel with the flow of the combustion exhaust flowing inside the combustion chamber 3, thereby suppressing the temperature rise of the heat shield 12.

The cover wall plate 13 is located below the first convex portion 14 and above the burner 4 (upstream of the first convex portion 14 in the flow direction of the combustion exhaust gas and downstream of the burner 4 in the flow direction of the combustion exhaust gas).

As shown in FIG. 3, the covering wall plate 13 has a blocking portion 20 at its lower end that blocks the gap between the covering wall plate 13 and the first combustion section outer wall 6. The blocking portion 20 prevents air from entering between the covering wall plate 13 and the first combustion section outer wall 6. Meanwhile, the blocking portion 20 provided at the lower end of the covering wall plate 13 guides air between the covering wall plate 13 and the burner 4.

As a result, the air curtain effect of the air passing between the cover plate 13 and the burner 4 prevents the flame of the burner 4 from falling toward the cover plate 13 and the heat shield plate 12, and prevents the cover plate 13 and the heat shield plate 12 from overheating.

In this embodiment, an example is shown in which the heat shield 12 is provided with a second protrusion 16 having a substantially rectangular flat surface facing the first protrusion 14, but the shape of the second protrusion of the present invention is not limited to that shown in this embodiment.

For example, as shown in FIG. 5, a plurality of elongated grooves 21 (non-penetrating) extending vertically may be formed in the substantially rectangular surface of the second protrusion 16 of the heat shield 12, arranged horizontally at a predetermined interval from each other. This makes it possible to increase the effective surface area of the second protrusion 16, which is provided in a relatively narrow range, and improve the cooling effect of the heat shield 12.

In addition, in this embodiment, a combustion device in which the combustion fan is placed at the top and the combustion exhaust flows from bottom to top inside the combustion chamber 3 (heat exchange housing 2 is provided on top of the combustion housing 1) has been described as an example, but the present invention can also be suitably used in a combustion device in which the combustion fan is placed at the bottom and the combustion exhaust flows from top to bottom inside the combustion chamber (a configuration that is the inverted top and bottom of this embodiment) and similar effects can be obtained.

1...combustion box, 3...combustion chamber, 4...burner, 12...heat shield, 14...first protrusion, 15...closed space, 17...air inlet hole, 18...outlet opening, 16...second protrusion, 19...inclined piece, 20...covering wall plate.

Claims (6)

A tension combustion type combustion apparatus, comprising: a combustion chamber having a burner therein; a heat shield plate provided on the inner surface of the combustion chamber; and a combustion fan for supplying combustion air to the burner, the combustion fan being disposed downstream in the flow direction of the combustion exhaust gas generated from the burner;
a closed space formed in a partial region between the outer wall of the combustion housing and the heat shield plate by the heat shield plate being in contact with the periphery of a partial region of the outer wall of the combustion housing;
an air inlet hole formed in an outer wall of the combustion casing at a position that defines the closed space, the air inlet hole introducing air into the closed space;
a discharge opening formed in the heat shield at a position forming the closed space and allowing air in the closed space to flow out into the combustion chamber. 2. The combustion apparatus according to claim 1,
a combustion device characterized in that the closed space is formed inside the first convex portion by a first convex portion bulging outward from the partial region of the outer wall of the combustion housing and the heat shield abutting the periphery of the first convex portion of the outer wall of the combustion housing. 3. The combustion apparatus according to claim 2,
The combustion device according to claim 1, wherein the heat shield has a second protrusion that protrudes into the closed space at a position corresponding to the first protrusion. The combustion device according to any one of claims 1 to 3,
The combustion device is characterized in that the outflow opening is formed downstream of the burner and downstream of the air introduction hole. The combustion device according to any one of claims 1 to 4,
A combustion device characterized in that the heat shield plate has an inclined piece that inclines from the downstream end of the outlet opening toward the upstream side of the closed space in a direction approaching the outer wall of the combustion case. The combustion device according to any one of claims 1 to 5,
a cover wall plate provided continuously with the heat shield plate, positioned upstream of the closed space and downstream of the burner, and covering the inner surface of the combustion box.