JPH0428904A - Burning device - Google Patents

Abstract

PURPOSE:To constitute a recirculating system without using a special heat- resistant material thereby reducing the cost and to eliminate components of high temperature while assuring the durability of fan thereby reducing the formation of nitrogen oxides for household use by branching the exhaust passage from the halfway position and installing a connecting tube to the air supply chamber for constituting an exhaust recirculating system and by installing a means for controlling the air resistance at the air flow-in portion of air supply chamber. CONSTITUTION:When a fan 8 is operated, air is drawn from an air supply port 21, whereby an air supply chamber 22 comes into a negative pressure zone and the inside of a connecting tube 20 whose one end opens to the air supply chamber 22 is included in the negative pressure zone. The other end of the connecting tube 20 opens to within an exhaust passage 15 consisting of an exhaust hood 13 and an exhaust top 14. Therefore, part of exhaust gas is drawn by this negative pressure to within the air supply chamber 22 via the connecting tube 20. This exhaust gas, together with fresh air whose flow rate is controlled by dampers 24, 24', enters the fan 8 through the air supply port 21, and then fed to a burner 9 again.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the combustion system of mainly domestic combustion devices such as water heaters and space heaters, and particularly relates to a device for suppressing the production of nitrogen oxides.

BACKGROUND OF THE INVENTION Conventionally, this type of combustion apparatus has been developed mainly for industrial use, such as in Japanese Utility Model Application Publication No. 2-7414.
There was something like the one shown in the picture. That is, a combustion gas suction passage 2 is formed near the outer periphery of the burner body 1, an inlet 3 of the combustion gas suction passage 2 is provided at a position to suck the combustion gas flowing backward within the burner body 1, and the combustion gas is passed through the circulation passage 4. The air was supplied to the air suction path 6 of the fan 5, and a damper 7 for adjusting the flow rate was installed at the entrance of the air suction path 6.

In such a configuration, a part of the high-temperature combustion gas burned in the burner body l is guided from the combustion gas suction path 2 to the inlet 3, passes through the circulation path 5, enters the air suction path 6, and is sucked together with fresh air by the fan 5. The air passes through the fan 5 from the air suction passage 6 and is again supplied to the burner body 1, where exhaust gas recirculation is performed and the generation of nitrogen oxides is reduced.

Problems to be Solved by the Invention However, in a combustion apparatus having such a configuration, the high temperature combustion gas is directly recirculated, so the recirculation path becomes extremely hot and requires expensive constituent materials. Additionally, the durability of the fan is reduced by the recirculating hot combustion gases. Furthermore, the complicated structure of the burner body and the presence of high-temperature parts made it impossible to apply it to household combustion equipment, where the control device also had to be housed in the main body case.

Therefore, the present invention reduces costs by constructing a recirculation system without using special heat-resistant materials, guarantees the durability of the fan, eliminates high-temperature components, and generates less nitrogen oxide, making it safe for household use. The purpose is to obtain a combustion device.

In order to achieve the above object, the present invention includes a fan, a burner provided downstream of the fan, a combustion chamber downstream of the burner, a heat exchanger, and a heat exchanger for directing combustion gas into the atmosphere. The exhaust passages leading to the air are housed in the main body case in close contact with each other, an air supply chamber is provided upstream of the fan's air supply port, and a connecting pipe is provided that branches from the middle of the exhaust passage and reaches the air supply chamber. The exhaust gas recirculation system is constructed by the exhaust gas recirculation system, and the air inflow section of the air supply chamber is provided with an adjustment control means that can adjust the ventilation resistance.

In addition, the main body, which consists of a fan, a burner installed downstream of the fan, a combustion chamber downstream of the burner, a heat exchanger, and an exhaust passage that leads combustion gas to the atmosphere, is housed in the case. An exhaust recirculation system is constructed by branching from the middle of the exhaust passage and connecting a pipe to the fan.The fan is installed on one side of the burner, the connecting pipe is placed on one side of the main body, and the connecting pipe is placed on the opposite side of the main body. Control means are installed on the side of the main body.

Effect With the above configuration, when the fan operates, the air supply chamber becomes a negative pressure region. When a negative pressure region occurs, the gas inside the connecting pipe and fresh air flow into the air supply chamber from the air inlet and are sent to the fan through the air supply port. Air supplied from the fan is turned into high-temperature gas in the combustion chamber by the burner, but turned into low-temperature exhaust gas by the heat exchanger and released into the atmosphere through the exhaust passage. Since one end of the connecting pipe O is connected to the exhaust passage, a part of the combustion exhaust gas flowing through the exhaust passage passes through the communicating pipe, passes through the air supply chamber, and is guided to the fan, forming an exhaust gas recirculation system. become. Because relatively low-temperature exhaust gas flows inside the connecting pipe, special materials and processing methods are not required. Furthermore, by adjusting the ventilation resistance of fresh air using the adjustment means, it becomes possible to adjust the balance with the ventilation resistance of the exhaust gas recirculation system, and it becomes possible to adjust the circulation rate of exhaust gas. In addition, the connecting pipe has a fan attached to one side of the burner and is moved to one side of the main body, and the control means is installed on the side of the main body on the opposite side of the connecting pipe, so the temperature of the connecting pipe is relatively low. In addition, heat transfer from the connecting pipe to the control means is reduced, and the control means can also be housed integrally within the main body case.

Embodiment Hereinafter, a case where an embodiment of the present invention is applied to a water heater will be described based on the accompanying drawings.

1 [ffl~ In Figure 3, a fan 8 is attached to one side of the burner 9, a drum-type combustion chamber 11 around which a water pipe 10 is wound, a heat exchanger 12 with fin pipe 2, and an exhaust hood that collects exhaust gas. 13. Exhaust valve 1 constituting the exhaust outlet
Four exhaust passages 15 are successively connected to each other in an airtight manner. A gas block 16 having a function of adjusting the flow rate of gas fuel is connected to the burner 1J. A water inlet on the upstream side of the water pipe 1o is connected to a water block 17 having a function of adjusting the amount of water entering. Further, a hot water outlet bi 118 is connected to the outlet of the heat exchanger 12, and a control block 19 is housed on the side of the main body of the water heater opposite to the fan 8. Here, one end of a connecting pipe 20 is open to the exhaust hood 14, and the other end is open to an air supply chamber 22 provided upstream of an air supply port 21 of the fan 8. A damper 24 is attached to the air inflow portion 23 of the air supply chamber 22 as a means for adjusting ventilation resistance. The above components are housed within the main body case 25.

Next, the operation of the configuration of this embodiment will be explained. When the hot water tap is opened and water begins to flow inside the water heater body, water flow is detected within the water block 17, and the fan 8 is operated in response to a command from the control block 19 to supply combustion air to the burner 9. On the other hand, fuel is supplied to the burner 9 at a flow rate determined by the control block 19 according to the hot water supply load.
supplied to

The supplied air and fuel are combusted in the combustion chamber 11 by the burner 9, becoming high-temperature combustion exhaust gas, and reaching the heat exchanger 12. Here, the water that has passed through the water block 17 and the water pipe 10 is
It is heated by high-temperature exhaust gas in the heat exchanger 12, becomes hot water, passes through the hot water tap 18, and is supplied for hot water supply. On the other hand, most of the low-temperature exhaust gas from which heat has been removed is collected in the exhaust hood 13 and released into the atmosphere from the exhaust top 14.

Here, when the fan 8 operates, air is sucked through the air supply port 21 and the air supply chamber 22 becomes a negative pressure region, and the inside of the connecting pipe 20 whose one end opens into the air supply chamber 22 is also included in the negative pressure region. Connecting pipe 2
Since the other end of the exhaust gas is opened into an exhaust passage 15 consisting of an exhaust hood 13 and an exhaust top 14, a portion of the exhaust gas is sucked into the air supply chamber 22 through the communication pipe 20 due to this negative pressure. This exhaust gas flows from the air supply port 21 to the fan 8 along with fresh air whose flow rate is adjusted by the damper 24.24''.
and is supplied to the burner 9 again. The large amounts of inert gas and water vapor contained in the exhaust gas cause slow combustion and increase the heat capacity of the combustion gas, which lowers the flame temperature and suppresses the production of nitrogen oxides.

Figure 4 shows the circulation rate of exhaust gas, the production of nitrogen oxides, and c.
Curve a, which shows an example of the characteristic of combustion performance expressed as o/Co, with respect to excess air ratio m, is for the case without exhaust gas recirculation, curve C is for the damper 24 with small ventilation resistance, and curve C is for the damper with large ventilation resistance. When a damper 24' is installed, the amount of fresh air sucked decreases, and the amount of exhaust gas sucked increases accordingly, increasing the circulation rate. Therefore, since the flame temperature also decreases by 9%, the amount of nitrogen oxides produced also decreases. On the other hand, combustion performance deteriorates slightly, but there is no practical problem if the set point is selected appropriately. Furthermore, by removing the lid of the main body case 25, the damper 24.24'' can be replaced.

Therefore, it is necessary to replace the damper 24.24゛ with the optimum displacement to suppress the generation of nitrogen oxides and ensure safe combustion in response to various fuel types and various installation forms of water heaters. This can be easily achieved by

Furthermore, the control block 19 is installed on the side of the main body opposite to the connecting pipe 20 provided on one side of the main body, and the connecting pipe 20 is connected because the low-temperature exhaust gas that has passed through the heat exchanger 12 passes through the connecting pipe 20. The amount of heat transferred from the tube 20 is small, so that the control block 19 can be mounted inside the main body case 25.

Effects of the Invention As is clear from the above explanation, the combustion apparatus of the present invention provides the following effects.

1. The exhaust gas recirculation system is constructed by installing a connecting pipe that branches off from the middle of the exhaust passage after passing through the heat exchanger and connects it to the air supply chamber installed upstream of the fan. Since the component parts are kept at a relatively low temperature, there is no need for new temperature measures or a new power source, and it is possible to reduce nitrogen oxides while suppressing noise increases.

2. An air supply chamber is provided on the upstream side of the fan, and a connecting pipe that guides the exhaust gas and an adjustment means that adjusts the ventilation resistance of fresh air are provided to control the amount of recirculated exhaust gas. Even with various installation configurations of combustion equipment, it is possible to realize optimal conditions that can reduce nitrogen oxides and ensure stable combustion in response to these conditions.

3. Since the method involves constructing an exhaust recirculation system by installing a new connecting pipe that branches off from the middle of the exhaust route, it can be easily applied to existing combustion equipment, and the manufacturing process can be easily modified. It can be realized inexpensively.

4. A connecting pipe through which the relatively low-temperature exhaust gas that has passed through the heat exchanger passes is installed on one side of the main body by installing a fan on one side of the burner, and a control means is installed on the side of the main body on the opposite side of the connecting pipe. Because of this, even if exhaust gas recirculation is performed, the amount of heat transferred from the connecting pipe to the control means can be controlled to be small, and installation within the main body case is possible.

[Brief explanation of the drawing]

Fig. 1 is a partially sectional perspective view of an embodiment of the present invention applied to a water heater, Fig. 2 is a vertical sectional view of Fig. 1, and Fig. 3 is a longitudinal sectional view of Fig.
The figure is a partial perspective view showing the main parts of the exhaust gas recirculation system near the fan, Figure 4 is a comparative explanatory diagram showing the combustion characteristics depending on the circulation rate of the exhaust gas recirculation, and Figure 5 is an overall sectional view of the conventional example. It is. 8...Fan, 9...Burner, 11.
... Combustion chamber, 12 ... Heat exchanger, 15.
...Exhaust passage, 19...Control block,
20... Connecting pipe, 21... Air supply port, 2
2... Air supply chamber, 23... Air inflow section,
24.24゛ ・・・・−・Damper, 25・・・・・・
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Claims (2)

[Claims] (1) A main body consisting of a fan, a burner provided downstream of the fan, a combustion chamber downstream of the burner, a heat exchanger, and an exhaust passage for guiding combustion exhaust gas into the atmosphere, which are successively placed in close contact with each other. The fan is housed in a case, an air supply chamber is provided upstream of the air supply port of the fan, and a connecting pipe is provided that branches from the middle of the exhaust passage and reaches the air supply chamber to constitute an exhaust gas recirculation system. . A combustion apparatus, wherein an air inflow portion of the air supply chamber is provided with an adjustment control means for adjusting ventilation resistance. (2) A main body including a fan, a burner provided on the downstream side of the fan, a combustion chamber downstream of the burner, a heat exchanger, and an exhaust passage for guiding combustion exhaust gas into the atmosphere, which are successively placed in close contact with each other. The exhaust recirculation system is constructed by storing the exhaust passage in a case, branching from the middle of the exhaust passage, and providing a connecting pipe to the fan.The fan is attached to one side of the burner, and the connecting pipe is connected to the main body. A combustion device in which a control means is placed on one side of the main body and installed on a side of the main body opposite to the connecting pipe.