JPH0246841B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides a burner body that supplies a mixed gas of fuel gas and combustion air with one end of a cylindrical porous body, and the mixed gas is supplied into the inside of the porous body. Regarding the surface combustion burner, in which the combustion surface of the mixed gas that has passed through the porous body is formed by the outer peripheral surface of the porous body, the flame lift can be maintained even when the combustion load is increased and the primary air excess ratio is increased. The purpose of this invention is to enable stable surface combustion without generation, and also to allow modification that is inexpensive and easy to manufacture.

More specifically, as shown in Fig. 4, in a conventional surface combustion burner in which the combustion surface is simply formed of a porous body 4 such as a wire mesh, the combustion load is increased in order to make the burner more compact, and nitrogen oxidation If the primary air excess ratio is increased in order to reduce the amount of NOx generated, a lift of the flame will occur on the side A of the combustion surface connected to the burner body 2, which may impair uniform heating or cause incomplete heating. Therefore, in reality, the disadvantage is that the burner becomes large because the combustion load is small, or the air becomes more likely to be contaminated by NOx because the primary air excess ratio is small. However, the present invention is advantageous in terms of manufacturing, allows the burner to be made compact, and
This effectively suppresses air contamination caused by NOx, and also enables stable, uniform surface combustion without the above-mentioned flame lift.

Next, embodiments of the present invention will be described with reference to illustrative drawings.

As shown in Fig. 1, cylindrical punching metal 1
The burner main body 2 is fitted onto the upper end and the lid 3 is fitted onto the lower end, and a cylindrical wire mesh 4 is fitted onto the outer peripheral surface of the punching metal 1 with the burner main body 2 and the lid 3 fixed together. At the same time, a ring-shaped flame-holding wire mesh 5, which is coarser than the cylindrical wire mesh 4 and has a width of about 20 mm, is fitted onto the end of the cylindrical wire mesh 4 on the side connected to the burner body 2, and The combustion chamber is configured so that a mixed gas of fuel gas and combustion air is ejected from the combustion surface and burned on the surface of the combustion surface. and,
An electric fan 6 that supplies combustion air and an orifice 7 located downstream of the electric fan 6 are connected to the burner body 2.
A zero governor 9 is connected to the fuel gas supply pipe 8 which is installed inside the burner body 2 and connected to the burner body 2 near the downstream side of the orifice 7.
At the same time, a zero governor 9 is installed to reduce the pressure from the air supply path.
A pressure regulating pipe 10 is provided to automatically adjust the fuel gas supply amount by acting on the fuel gas, so that the mixture ratio of the fuel gas and combustion air is automatically maintained within an appropriate range that does not cause flame lift or backfire. It is configured so that In addition, a partition wall 11 is provided inside the burner body 2, and a cylinder 12 for gas mixing and dispersion supply is connected to the partition wall 11.
It is constructed so that the fuel gas and combustion air can be thoroughly mixed and evenly distributed over the combustion surface.

The surface combustion burner configured as described above is placed in a case 13 forming a combustion chamber, with the combustion surface positioned inside the combustion chamber, and the upper part of the case 13 is closed with a lid part 14 connected to the burner body 2. Case 1 is installed in such a way that the combustion gas flows from the downward flow path portion to the exhaust path 15 to prevent trouble with the burner due to drain.
At the same time, finned water pipes 16a and 16b are provided at the lower part of 3, and the outlet side water pipe portion 16a is arranged on the upper side of the combustion gas flow than the inlet side water pipe portion 16b, and the inlet side and outlet side water pipe portions 16a and 16b are arranged. The intermediate water pipe portion 16c to be connected is wound tightly around the case 13 at a position corresponding to the combustion chamber, thereby forming a water heater that takes out cold water supplied from the water pipe inlet side 16d as hot water from the water pipe outlet side 16e. There is. Further, a spark plug 17 and a flame detector 18 are provided on the lid portion 14 so that ignition can be easily performed, and the fuel gas supply can be automatically stopped when the flame is extinguished.

Incidentally, the surface combustion burner according to the present invention can be used in various water heaters, hot air heaters, and other various heating purposes.

Furthermore, various configuration changes can be made to form the combustion surface, such as using only the wire mesh 4, and the members forming the combustion surface are collectively referred to as the porous body 4.

Alternatively, several flame-holding wire meshes 5 may be stacked one on top of the other.

Next, the results of experiments that confirmed the effectiveness of the flame-holding wire mesh 5 will be explained.

First, the combustion load and primary air excess ratio were determined using a burner equipped with a heat-retaining wire mesh 5 (the burner of the present invention) and a burner without the wire mesh 5 (conventional burner), and using city gas (13A gas) as the fuel gas. When we investigated the limit of flame lift while making changes, we obtained the results shown in Figure 2. That is, it has been found that according to the burner of the present invention, stable surface combustion can be performed even when the combustion load and primary air excess ratio are greatly increased compared to conventional burners.

In addition, we investigated how combustion load and primary air excess ratio (λ) affect NOx generation in surface combustion burners, and the results shown in Figure 3 were obtained. In other words, the combustion load fluctuation is
It was found that if it is about 50 Kcal/hr・cm ² or more, there is almost no effect on NOx generation, and the amount of NOx generated can be reduced as the primary air excess ratio is increased, regardless of the combustion load.

From the above results, it can be seen that the burner of the present invention can increase the primary air excess ratio by about 0.4 compared to the conventional burner, assuming that the combustion loads are the same.
It has become clear that the amount of NOx generated can be reduced by more than 12ml/1000Kcal.

In summary, the present invention connects one end side of a cylindrical porous body to a burner body that supplies a mixed gas of fuel gas and combustion air in a state in which the mixed gas is supplied to the inside of the porous body. , in a surface combustion burner in which the combustion surface of the mixed gas that has passed through the porous body is formed by the outer circumferential surface of the porous body, a ring shape is formed at an end of the porous body on the side connected to the burner body; The flame-holding wire mesh is disposed on the side from which the mixed gas is ejected from the porous body and is fitted onto the outside, and its functions and effects are as follows. As previously explained in detail based on the experimental results, even if the combustion load is increased and the primary air excess ratio is increased, stable surface combustion without flame lift can be performed, resulting in a compact We are now able to provide a surface combustion burner that can effectively suppress NOx generation.

More specifically, in a conventional surface combustion burner without a flame-holding wire mesh 5, when the combustion load and primary air excess ratio are increased, flame lift occurs at the end of the combustion surface connected to the burner body 2. As a result of investigating the cause, it was found that the temperature at the connection end became low due to heat conduction from the porous body 4 to the burner body 2, making ignition of the gas uncertain.
After researching various means to solve this problem, we found that if the flame-holding wire mesh 5 is provided as described above, the heat dissipation due to heat conduction from the flame-holding wire mesh 5 to the burner body 2 will be caused by the high-temperature porous body between them. The flame holding wire mesh 5 is heated by the high-temperature tip of the flame formed by the porous body 4, and furthermore, the flame is suppressed sufficiently due to the presence of flame from the part of the porous body 4 that burns stably. Since the flame-holding wire mesh 5 is heated by radiant heat transfer, the flame-holding wire mesh 5 is stably maintained at a high enough temperature for gas ignition, and flame lift is sufficiently prevented. I found it.

Furthermore, instead of the flame-holding wire mesh 5, it is possible to provide a flame-holding coil or the like, but since it is difficult to install the coils in a fixed arrangement, there is a problem in terms of manufacturing, and the present invention is not suitable. When the ring-shaped flame-holding wire mesh 5 is fitted onto the cylindrical porous body 4 as shown in FIG.
It can be easily manufactured with stable quality using inexpensive commercially available products, and is also excellent in actual mass production.

[Brief explanation of the drawing]

The drawings show an embodiment of the surface combustion burner according to the present invention, FIG. 1 is a schematic vertical cross-sectional view of a water heater, FIGS. 2 and 3 are graphs showing experimental results, and FIG. 4 is a diagram showing a conventional burner. FIG. 2... Burner body, 4... Porous body, 5... Flame holding wire mesh.

Claims (1)

[Scope of Claims] 1. A state in which one end side of a cylindrical porous body 4 is connected to a burner body 2 that supplies a mixed gas of fuel gas and combustion air, and the mixed gas is supplied to the inside of the porous body 4. A surface combustion burner in which the combustion surface of the mixed gas passing through the porous body 4 is formed by the outer peripheral surface of the porous body 4, and the end of the porous body 4 on the side connected to the burner body 2 A surface combustion burner in which a flame-holding wire mesh 5 formed in a ring shape is disposed on the side of the mixed gas ejected from the porous body 4 and is externally attached to the surface of the surface combustion burner.