JPH0313701A - Burning apparatus - Google Patents

Abstract

PURPOSE:To reduce the nitrogen oxides without having an additional power source and achieve a stable burning by forming an exhaust gas recirculation system by adding a connecting pipe which is diverted from the exhaust gas line and has an open end near to the air intake of a fan, and providing a flow rate control means which, disposed in the way of the exhaust gas recirculation system, controls the exhaust gas recirculation rate. CONSTITUTION:When a fan 10 is operated, a negative pressure zone is created near the air intake. The exhaust gas intake 31 disposed in the casing 29 is included in this negative pressure zone, and so is the exhaust gas chamber 30. Therefore, the exhaust gas in the circulation chamber 25 is drawn into the exhaust gas chamber 30 through a connecting pipe 28 on account of the negative pressure. Such exhaust gas is introduced from the intake 31 to the fan 10, and is uniformly mixed with the fresh combustion air in the casing 29 to be supplied to the burner 11. This way, the burning becomes slow due to the inert gas and water vapor which are contained in large quantity in the exhaust gas. And, since the thermal capacity of the exhaust gas is increased, the flame temperature becomes lower, reducing the forming of the nitrogen oxides.

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 to a combustion device that suppresses the production of nitrogen oxides.

2. Description of the Related Art Conventionally, this type of combustion apparatus has been applied to a large industrial boiler as shown in FIG.

That is, a recirculation passage 2 was branched from the middle of the exhaust passage 1, and a relay fan 3 and a damper 4 for a flow of 1 m were installed in the middle. The recirculated exhaust gas is mixed with fresh combustion air supplied from a blower fan 5 and sent to a burner 7 together with fuel supplied from a fuel supply pipe 6, where it is combusted in a combustion chamber 8 and passed through a heat exchanger 9. After that, it becomes exhaust gas and is released into the atmosphere through the exhaust passage 1. Here, the damper 4 controls the recirculated exhaust gas flow rate so as to maintain stable combustion and minimize the production of nitrogen oxides in response to various operating conditions of the boiler.

Problems to be Solved by the Invention However, a combustion device having such a configuration requires a plurality of fans 3.5. Furthermore, a motor is required to drive the damper 4 in order to adjust the flow rate of the recirculated exhaust gas. Therefore, the combustion apparatus becomes larger, the noise becomes louder, and the cost increases significantly, so that it cannot be used as a household combustion apparatus as it is.

Therefore, the present invention aims to simplify the exhaust gas recirculation system, downsize the combustion device, prevent noise increase, and further reduce costs.

Means for Solving the Problems In order to achieve the above objects, the present invention includes a fan, a burner provided downstream of the fan, a combustion chamber downstream of the burner,
A heat exchanger and an exhaust passage are provided in close contact with each other, and a connecting pipe is provided that branches off from the middle of the exhaust passage and has an opening near the fan intake port to constitute an exhaust gas recirculation system. A flow control means for controlling the amount of recirculated exhaust gas is provided in the middle of the flow.

Effect: With the above configuration, when the fan operates, a negative pressure region is generated at the intake port. Since the opening of the connecting pipe is located near the intake port, when this negative pressure region occurs, the gas inside the connecting pipe is drawn toward the fan (this means that one end of the connecting pipe is connected to the exhaust passage). Because they are connected, part of the combustion exhaust gas flowing through the exhaust passage is guided to the fan through the communication pipe, forming an exhaust recirculation system without providing any additional driving force. The flow rate control means provided in the middle of the system makes it possible to adjust the flow rate of the recirculated exhaust gas so as to ensure optimal combustion conditions corresponding to the fuel type and supply/exhaust resistance.

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 to 3, on the downstream side of the fan 10, there is a burner 11, a drum-type combustion chamber 13 wrapped around a water pipe 12, a fin-pipe heat exchanger 14, an exhaust hood 15 for collecting exhaust gas, and an exhaust outlet. The exhaust tops 16 constituting the exhaust tops 16 are successively connected to each other in an airtight manner. A gas block 17 having a function of adjusting the flow rate of gas fuel is connected to the burner 11. A water block 18 having a function of adjusting the amount of water entering is connected to a water inlet on the upstream side of the water pipe 12. Further, a hot water outlet pipe 19 is connected to the outlet of the heat exchanger 14, and a control block 20 is housed on the side of the main body of the water heater.

Here, a communication port 21 is opened on the side of the exhaust hood 15, and an exhaust cover 23 for exhaust gas recirculation having an I[22]
covered with. The space inside the exhaust cover 23 is the communication port 2.
A small exhaust chamber 24 and a circulation chamber 25 having the same size as each other are separated by a damper 26. The damper 26 is provided with a plurality of small openings 27. The bottom surface of the circulation chamber 25 is configured in the shape of a funnel, and a connecting pipe 28 is connected thereto.

On the other hand, an exhaust gas chamber 30 is provided near the air supply port of the casing 29 of the fan 10, and a connecting pipe 28 is connected thereto. Further, an exhaust gas inlet 31 is provided in the casing 29 at a position near the air supply opening where a negative pressure region is generated, and communicates with the exhaust gas chamber 30 .

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 18, and the fan 10 is operated in response to a command from the control block 20 to blow combustion air to the burner 1.
1. On the other hand, fuel is supplied to the burner 11 through a gas block 17 at a flow rate determined by a control block 20 according to the hot water supply load. The supplied air and fuel are combusted in the combustion chamber 13 by the burner 11 and become high-temperature combustion exhaust gas, which reaches the heat exchanger 14, where the water block 1
8. The water that has passed through the water pipe 12 is heated by high-temperature exhaust gas in the heat exchanger 14, becomes hot water, and passes through the hot water pipe 19.
Provided 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 15 and released into the atmosphere from the exhaust top 16.

Here, a part of the exhaust gas inside the exhaust hood 15 is transferred to the communication port 21.
It passes through and enters the small exhaust chamber 24. Exhaust gas is damper 26
After the flow rate is adjusted by the small opening 27 provided in the circulation chamber 2
5. If 122 of the exhaust cover 23 is removed here, the damper 26 can be replaced. Therefore, by replacing the damper 26, the optimum displacement can be easily achieved to suppress the generation of nitrogen oxides and ensure stable combustion in response to various fuel types and various installation configurations of water heaters. can.

On the other hand, when the fan 10 operates, a negative pressure region is generated near the air supply port. Exhaust gas inlet 3 provided in the casing 29
0 is also included in the negative pressure region, and the exhaust gas chamber 30 also becomes a negative pressure chamber. Therefore, due to this negative pressure, the exhaust gas in the circulation chamber 25 is sucked into the exhaust gas chamber 30 through the connecting pipe 28. This exhaust gas enters the fan lO through the exhaust gas suction port 31, is uniformly mixed with fresh combustion air in the casing 29, and is supplied to the burner 11 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. FIG. 4 shows the exhaust gas characteristics with and without exhaust gas recirculation. By appropriately setting the damper 26 and the excess air ratio, the CO generation characteristics are slightly deteriorated, but the generation of nitrogen oxides can be significantly reduced, and the increase in noise can be suppressed at the same time.

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

(1) An exhaust recirculation system is constructed by branching from the middle of the exhaust passage and installing a connecting pipe near the fan intake port, eliminating the need for a new power source and reducing nitrogen oxides while suppressing noise. can be realized.

(2) In order to provide a means to control the amount of recirculated exhaust gas in the middle of the exhaust gas recirculation system, it can be used with various fuels with different physical properties and with various installation configurations of combustion equipment.
It is possible to realize optimal conditions that reduce nitrogen oxides and ensure stable combustion.

(3) Since the method involves constructing an exhaust recirculation system by installing a new connecting pipe branching from the middle of the exhaust route, it can be easily applied to existing combustion equipment, and the manufacturing process can be easily modified. Therefore, it can be realized at low cost.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional overall perspective view of an embodiment of the combustion apparatus of the present invention applied to a water heater, FIG. 2 is a partial cross-sectional perspective view showing the main part of the exhaust passage in FIG. 1, and FIG. The figure is a partial cross-sectional perspective view showing the main parts of the exhaust gas recirculation system near the fan intake port.
The figure is a comparative explanatory diagram showing combustion performance with and without exhaust gas recirculation, and FIG. 5 is an overall configuration diagram of a conventional example. lO...fan, ll...burner, 1
3... Combustion chamber, 14... Heat exchanger, 1
5...Exhaust hood, 21...Communication port,
22...Lid, 23...Exhaust cover, 2
6... Damper, 28... Connecting pipe, 30
...Exhaust gas chamber, 31...Exhaust gas suction port. Name of representative: Patent attorney Shigetaka Awano and one other figure

Claims (1)

[Claims] A fan, a burner provided downstream of the fan, a combustion chamber downstream of the burner, a heat exchanger, and an exhaust passage are successively provided in close contact with each other, and branched from the middle of the exhaust passage to the fan. An exhaust gas recirculation system is constructed by providing a connecting pipe having an opening near an air supply port, and a flow rate control means for controlling the amount of recirculated exhaust gas is provided in the middle of the exhaust gas recirculation system.