JPH0328602A - Combustion unit - Google Patents

Abstract

PURPOSE:To make it possible to reduce the generation of nitrogen oxides and inhibit vibration combustion in a combustion unit such as hot water supply equipment or the like by installing a connection pipe which introduces a part of exhaust gas in a combustion chamber near a fan intake port, forming an exhaust recycling system, and connecting the connection pipe and an exhaust top with an exhaust pipe. CONSTITUTION:A greater part of exhaust gas radiated and cooled in a heat exchanger 15 is collected in an exhaust hood 16 and discharged into an atmosphere from an exhaust top 17. A part of the exhaust air flows through an exhaust pipe 24 and joins a part of the exhaust gas from an opening 25 and it is introduced into a fan 10 by way of a connection pipe 23 and absorbed into the fan 10. The gas is mixed with fresh air and sent to a burner 11 again. As a result, inert gas contained in the exhaust gas and vapor induce slow combustion and increase the thermal capacity of combustion gas. It is, therefore, possible to lower the temperature of flames and inhibit the generation of NOx and vibration combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the combustion system of household combustion equipment, such as water heaters and space heaters, and particularly relates to a device for suppressing the production of nitrogen oxides. Prior Art Conventionally, this type of combustion equipment has been applied to large industrial boilers as shown in Figure 3. That is, a recirculation passage 2 is branched from the middle of the exhaust passage 1, and a relay fan 3 and a damper 4 for adjusting the flow rate are arranged 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 recirculated exhaust gas flow rate was controlled by the damper 4 to minimize the production of nitrogen oxides while maintaining stable combustion in response to various operating conditions of the boiler. Problems to be Solved by the Invention However, in the above structure, since the exhaust gas is recirculated, the primary air ratio of the burner decreases and the flame becomes unstable. a) or 4(
b), and oscillatory combustion is likely to occur.

Therefore, the present invention solves this conventional yA problem.
The exhaust gas recirculation system aims to reduce the generation of nitrogen oxides and also suppress the occurrence of oscillatory combustion. Means for solving the problem In order to achieve the above object, the present invention provides a fan, a burner provided downstream of the fan, a combustion chamber downstream of the burner, and a heat exchanger. An exhaust hood and an exhaust knob are successively arranged in close contact with each other, and a connecting pipe is provided to guide the exhaust gas from the combustion chamber to the vicinity of the intake port of the fan to form an exhaust recirculation system. is provided with an exhaust pipe that communicates with the connecting pipe and opens the other end to the IJF air top.

Operation The present invention has the above-mentioned aspect, so that when the fan operates, a part of the exhaust gas is guided into the fan from the combustion chamber and the exhaust top through the connecting pipe opened near the intake port of the fan, thereby producing fresh combustion air. The inert gas and water content contained in the exhaust gas cause slow combustion, lowering the flame temperature and suppressing the production of nitrogen oxides.
On the other hand, since a part of the combustion chamber is directly opened to the exhaust top through the exhaust pipe, the combustion chamber, heat exchanger, and exhaust hood 1.'
, the acoustic space determined by the exhaust top, etc. is opened, and the resonance sharpness (Q) of the resonant frequency is reduced, making it difficult for resonance to occur even if the source is the same.

Embodiment F From the following, a case in which an embodiment of the present invention is applied to a water heater will be described based on the accompanying drawings.

In FIGS. 1 and 2, on the downstream side of the fan 10, there is a burner 11, a drum-type combustion chamber 13 around which a water pipe 12 is wound, and a fin-pipe heat exchanger having a diagonal pipe 14 connected to the water pipe 12. 15. An exhaust hood 16 that collects the exhaust gas and an exhaust top l7 that crosses the exhaust outlet are successively connected to each other in an airtight manner. A gas block 18 having a function of adjusting the flow rate of gas fuel is connected to the burner 1l, and a water block 19 having a function of adjusting the amount of water input is connected to the water inlet on the upstream side of the water pipe 12. Further, a hot water tap vibrator 20 is connected to the outlet of the heat exchanger 15, and a control block 21 is housed on the side of the main body of the water heater.

Further, the combustion chamber I3 is provided with an opening 25 that communicates with a connecting pipe 23 whose other end opens near the intake port 22 of the fan 10, and an exhaust pipe 24 whose other end opens into the exhaust top I7. ing.

In the above configuration, when the hot water tap is opened and water begins to flow inside the water heater body, the water flow is detected in the water valve l9,
The fan 10 operates according to a command from the control block 2l, and combustion air is supplied to the burner.

On the other hand, the fuel roughness is determined by the gas blower 18, and the flow rate determined by the control block 21 according to the supply/& load is supplied to the burner 11. The supplied air and fuel are combusted in the combustion chamber 13 by the burner l1 and become high-temperature exhaust gas for heat exchange.
It reaches 8l5. Here, the water that has passed through the water block 19 and the water pipe 12 is heated by high-temperature exhaust gas in the heat exchanger 15, and then passes through the hot water pipe 20 to be used 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 16 and released into the atmosphere from the exhaust top 17, but a portion passes through the exhaust pipe 24 and enters the exhaust gas from the opening 25. the communication pipe 2 from the opening 25.
3 to the fan 1.0 side, and is sucked into the fan 10. This exhaust gas is uniformly mixed with fresh combustion air and is supplied to the burner 11 again. As a result, the large amount of inert gas and water vapor contained in the exhaust gas causes slow combustion, and the heat capacity of the combustion gas increases, which lowers the flame temperature and suppresses the production of nitrogen oxides. effective. Figure 2 shows the exhaust gas characteristics with and without exhaust gas recirculation. On the other hand, an open part 25 and an exhaust pipe 2 opened to the combustion part l3.
4, the configuration has an acoustically open resonant space,
The Q of the resonant frequency becomes small, making it possible to suppress the occurrence of oscillatory combustion. Effects of the Invention As described above, according to the combustion apparatus of the present invention, a part of the combustion chamber is opened directly to the exhaust top through the air pipe, and part of the exhaust gas is guided to the upstream side of the fan, thereby reducing the amount of combustion air. Go inside again
This system has the effect of reducing nitrogen oxides without requiring a new power source, as well as suppressing the occurrence of oscillatory combustion associated with it.

[Brief explanation of drawings]

Figure 1 is an overall perspective view with some parts missing when the present invention is applied to a water heater as an example of the present invention, Figure 2 is a comparative explanatory diagram showing combustion performance with and without exhaust gas recirculation, and Figure 3 is FIG. 4, which is an overall configuration diagram of the conventional example, is a diagram showing the relationship between the presence or absence of exhaust gas recirculation and the oscillating combustion occurrence region. IO...Fan, 11...Burner, 1
3... Combustion chamber, 15... Heat exchanger, l
6...exhaust hood, l7...exhaust top, 22...intake port, 23...connecting pipe, 24...exhaust pipe, 25...Opening.

Claims (1)

[Claims] A fan, a burner provided downstream of the fan, a combustion chamber downstream of the burner, a heat exchanger, an exhaust hood, and an exhaust top are sequentially provided in close proximity to each other, and a part of the exhaust gas is discharged from the combustion chamber. A combustion device comprising a connecting pipe that guides gas to the vicinity of the intake port of the fan to constitute an exhaust gas recirculation system, and an exhaust pipe that communicates with the connecting pipe at one end and opens at the exhaust top at the other end.