JPS6234115Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a surface combustion burner mixer that burns a mixture of fuel gas and combustion air through an air permeable panel made of ceramics or the like near its outer surface. Although there are some differences in structure, conventional surface combustion burners have a mixer for pre-mixing fuel gas and combustion air at a predetermined ratio, and piping that supplies mixed gas from the mixer to the burner. However, in the case of a large turndown, there was a risk of explosion in the burner and the system, and there were many other defects. In order to eliminate these defects, for example,
A burner with a structure as shown in Publication No. -8721 was proposed. The burner with this structure is of the type shown in FIG. After mixing with the fuel gas supplied from the gas supply pipe 3 provided at the end of the combustion chamber 5 through the ventilation panel 6
The structure is such that the fuel is ejected and burns near the surface of the panel 6. However, according to experiments conducted by the present inventors, this type of burner does not mix fuel gas and combustion air sufficiently, resulting in bright flames and soot, especially in low air ratio combustion, and uneven flame distribution. A phenomenon was observed. In addition, because the panel has a two-layer structure, there is a large pressure loss, and in order to improve gas mixing, the volume of the mixing chamber, that is, the premix gas volume, must be made larger than necessary, and it is extremely dangerous in the event of flashback. However, they found that the mixing ratio of fuel gas and combustion air fluctuates greatly due to the influence of the flow velocity of each fluid, making it impossible to supply a constant mixing ratio. The present invention was made in order to eliminate the drawbacks of the conventional burner described above, and it includes a gas supply pipe inside the air supply pipe connected to the inlet side of the mixing and diffusion chamber, and a gas supply pipe located near the tip of the gas supply pipe in the circumferential direction. A plurality of ejection holes are provided in the air mixture, and a first baffle plate that moves forward and backward according to the flow velocity of the air mixture gas is provided in front of the opening, and a second baffle plate is further provided in front of the air mixture. The point is that a gas constriction part is formed. This structure allows for extremely good mixing of the fuel gas and combustion air, and also keeps the flow rate of the mixed gas through the mixing diffusion chamber constant, especially as the combustion load fluctuates, thereby keeping the pressure drop and stirring state constant. The purpose of the present invention is to provide a mixer for a surface-fired burner that can be used. Examples of this invention will be described below. FIG. 2 is a longitudinal section showing an embodiment of a surface combustion burner according to the present invention, in which a gas supply pipe 9 is located in the center of the burner body, a combustion air supply pipe 8 is concentrically arranged outside the burner body, and a gas supply pipe 9 is located in the center of the burner body. A mixing and diffusion chamber 13 and a ventilation panel 14 are arranged in front of the tube 9. Further, a plurality of gas ejection holes 10 are opened in the circumferential direction near the tip of the gas supply pipe 9, and an air supply pipe 8 and a pipe wall 15 of the mixing and diffusion chamber 13 are provided at the downstream end of the gas supply pipe. In order to maintain a constant flow rate of the mixed gas between the fuel gas and combustion air flowing through the same area, and to obtain good mixing under any load, change the direction of flow velocity (as indicated by the arrow).
A first baffle plate 11 having a movable structure that moves forward and backward is attached, and a second baffle plate 11 for stirring and mixing the mixed gas again at a predetermined flow rate is installed in the mixing diffusion chamber 13 in front of the first baffle plate 11. A baffle plate 12 is attached. Note that there is a breathable panel 14 on the exit side of the mixing and stirring chamber 13, and between it and the second baffle plate 12, a decompression function material 16 is attached for promoting the dispersion of mixed gas. Further, 17 indicates a combustion chamber. FIG. 3 shows an enlarged detailed structure of the first baffle plate portion of FIG. 2. FIG. That is, a shaft 19 having a stopper 18 at the tip is attached to the end face of the gas supply pipe 9,
The first baffle plate 11 penetrated by the shaft 19 is connected to the end surface of the gas supply pipe 9 by a spring 20. Next, the operation of the surface combustion burner of the present invention having the above structure will be explained. First, the fuel gas supplied from the gas supply pipe 9 is directed toward the axis of the gas supply pipe 9 through a plurality of gas ejection holes 10, for example, 4 to 8, with a diameter of 2 to 3 mm, which are opened near the tip of the gas supply pipe. The air is ejected almost at right angles, and after mixing with the combustion air flowing into the air supply pipe 8 along the outer surface of the gas supply pipe 9, the flow velocity is 4 to 20 m/sec.
It passes through a gap between the first baffle plate 11 and the pipe wall 15 of the mixing diffusion chamber 13, which is designed to set any desired flow velocity within the range of 2 m/min.
A second baffle plate 1 designed to be equal to or greater than sec
Pass 2. Here, it goes without saying that the second baffle plate may have a movable structure. During this time, the turbulent flow generated when passing through the first and second baffle plates causes effective and uniform stirring. The relationship between the first baffle plate 11 and the second baffle plate 12 is preferably such that the distance 1 between them is in the range of 1/4D<1<2D (D: inner diameter of the air supply pipe). In the above description, the first baffle plate 11 of the movable structure
When the load is high, the gas mixture moves to the downstream side, for example, to the position shown in FIG. is the first baffle plate 1
1 moves to the upstream side, for example, to the position shown in FIG. 2 112, and the gap between the mixing and diffusion chamber 13 and the pipe wall 15 becomes narrower. That is, since the first baffle plate 11 automatically moves in response to changes in the mixed gas flow rate,
The flow rate of the mixed gas passing through this section is always kept constant. The operation of the first baffle plate can be understood by the following equation. S=Q/tanθ・x・(2r+tanθ・x)π where Q: Flow rate of mixed gas (m ³ /sec) S: Flow rate at which the mixed gas passes through the first baffle plate 11 (m/sec) θ : Incline angle between mixing diffusion chamber 13 and tube wall 15 r: Maximum radius (m) of first baffle plate 11 x: First baffle when Q=0 (m ³ /sec) is set to 0 Moving distance of plate 11 (m) Solving the above equation for moving distance x

[Formula] becomes. If r, S, and θ are kept constant in the above equation, the moving distance x of the first baffle plate 11 changes as the flow rate Q of the mixed gas increases. In other words, if the spring 20, first baffle plate 11, and mixing diffusion chamber 13 are designed to satisfy the above equation, the first baffle plate 11 will move proportionally and remain constant depending on the flow rate of the mixed gas. The flow velocity is maintained. Next, FIGS. 4 to 8 show other embodiments of the first baffle plate portion according to the present invention. These figures will be explained below. Fig. 4 shows a case in which a spring is attached to the downstream side of the first baffle plate 11, and Figs. 5 and 6 show cylinders 22, 23, 24 filled with compressible gas, such as a dart pot, instead of the spring 21. This is an example using . 7 and 8 utilize a spring 25 and a leaf spring 26 from the pipe wall of the mixing and diffusion chamber. In addition, in Figures 2 to 8, the first baffle plate is perpendicular to the axis of the gas supply pipe and has a conical shape, but it is also possible to use a disc-shaped, cylindrical, spherical, etc. Any type may be used as long as it is bilaterally symmetrical and does not cause any side effects. Alternatively, grooves or blades may be provided on the side surface to rotate depending on the flow velocity of the mixed gas. Although the ejection holes provided in the gas supply pipe are arranged in one row in the circumferential direction, it goes without saying that a plurality of rows can be employed. As is clear from the above explanation, according to the present invention, by making the first baffle plate movable, the flow rate of the mixed gas flowing through the same part becomes constant as the combustion load increases, and as a result, the stirring state is kept constant. can be maintained and combustion management can be facilitated, which is very beneficial.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing the overall structure of a conventional surface combustion burner, FIG. 2 is a longitudinal sectional view showing an embodiment of the overall structure of the surface combustion burner according to the present invention, and FIG. It is a detailed view. Figures 4 and 5
6, 7, and 8 are longitudinal cross-sectional views showing other embodiments of the movable portion. 1, 8... Combustion air supply pipe, 2... Dispersion chamber,
3, 9... Gas supply pipe, 4... Mixing chamber, 5, 17
... Combustion chamber, 6, 7, 14 ... Ventilation panel, 1
0... Gas ejection hole, 11, 111, 112... First baffle plate, 12... Second baffle plate, 13... Mixing diffusion chamber, 15... Mixing diffusion chamber wall, 16... Pressure reduction functional material , 18... Stopper, 19... Axis, 2
0,21,25...Spring, 22,23,2
4... Cylinder, 26... Leaf spring.

Claims (1)

[Scope of utility model registration request] An air supply pipe is connected to a mixing diffusion chamber formed on the rear surface of the breathable panel, a gas supply pipe is embedded in the air supply pipe, and a gas ejection hole is provided in the gas supply pipe to eject the air in a circumferential direction. A hole is formed, and a mixture gas constriction portion is formed by a first baffle plate that moves forward and backward according to the flow velocity of the mixture gas in front of the hole, and a second baffle plate provided in front of the first baffle plate. A mixer with a flat combustion burner.