JP2010242982A - Pre-mix burner - Google Patents

Abstract

A premixed burner capable of improving the flame stability of a main flame by improving the flame holding property of a sub flame.
A cylindrical header portion 2 concentric with a fuel gas conduction pipe 1 and having a diameter larger than that of the fuel gas conduction pipe 1 and an air supply passage around the fuel gas conduction pipe 1 are provided at the tip of the fuel gas conduction pipe 1. 12, a baffle plate 4 concentric with the fuel gas conduction pipe 1 is provided around the fuel gas conduction pipe in an upstream portion of the air flow from the cylindrical header portion 2, and the baffle plate 4 has a central axis of the fuel gas conduction pipe 1. The distance from the central axis of the cylindrical header portion 2 is shorter than the distance from the central axis of the cylindrical header portion 2 to the peripheral wall. A plurality of secondary air injection holes 8 are provided in a portion longer than the distance to the peripheral wall, and the main gas fuel injection holes 5 for radially injecting the main fuel gas are provided on the peripheral wall of the cylindrical header portion 2. What is the primary air outlet location of the baffle plate 4? Become not provided at a position.
[Selection] Figure 1

Description

  The present invention relates to a premixed low NOx gas burner.

  Japanese Patent Application Laid-Open No. 11-337022 describes a premixed burner that mixes fuel gas injected from the burner tip and air. This burner closes the front end surface of the gas nozzle that supplies fuel gas, and injects fuel gas radially into the peripheral portion near the front end of the gas nozzle, and the gas nozzle periphery on the base side of the main gas fuel injection hole A sub-gas fuel injection hole is provided in the part. In this burner, an over-air portion with a large amount of combustion air and an over-fuel portion with a large amount of fuel gas are alternately formed, so that shade is generated in the flame, and the amount of NOx generated is reduced by the concentration combustion. In addition, the stability of the flame is also improved by generating a sub flame by the sub fuel gas injected from the sub gas fuel injection hole.

  However, in the burner described in JP-A-11-337022, in order to perform stable combustion, it is premised that the inflow speed of the combustion air and the ejection speed of the fuel gas can be kept high to some extent. This condition can be applied to a relatively large-capacity burner, but with a relatively small-capacity burner with a small capacity of the blower and a low fuel gas supply pressure (low pressure supply), a sufficient air flow rate and gas ejection flow rate can be obtained. Since this is not possible, there is a problem that flame holding becomes unstable and vibration combustion or the like is likely to occur.

Japanese Patent Application Laid-Open No. 11-337022

  The problem to be solved by the present invention is that even if the supply pressure of the fuel gas is low, premixing that can improve the combustion stability of the main flame by keeping the flame holding property of the sub flame high. To provide a burner.

  According to the first aspect of the present invention, a cylindrical header portion that is concentric with the fuel gas conduction pipe and has a larger diameter than the fuel gas conduction pipe at the tip of the fuel gas conduction pipe that supplies the fuel gas, and the periphery of the fuel gas conduction pipe And a baffle plate concentric with the fuel gas conduction pipe around the fuel gas conduction pipe in the upstream portion of the air flow from the cylindrical header portion, and the baffle plate from the central axis of the fuel gas conduction pipe The distance from the central axis of the cylindrical header portion to the peripheral wall is less than the distance from the central axis of the cylindrical header portion to the peripheral wall. A plurality of secondary air injection holes are provided in the long part, and a main gas fuel injection hole for injecting main fuel gas radially from the central axis of the cylindrical header part is provided on the peripheral wall of the cylindrical header part. Primary air jet of baffle plate Characterized in that provided in a position that does not overlap the holes installation position.

  According to the second aspect of the present invention, in the premixed burner, the baffle plate primary air ejection hole installation position overlaps with the peripheral wall of the portion sandwiched between the cylindrical header portion of the fuel gas conduction pipe and the baffle plate. A sub-gas fuel injection hole for injecting the sub-fuel gas in a direction not to be provided is provided.

  According to a third aspect of the present invention, in the premixed burner, a fuel gas conduction pipe flow path reducing member for narrowing a gas flow path of the fuel gas conduction pipe is provided near the tip of the burner.

By carrying out the present invention, a negative pressure region is generated between the cylindrical header portion and the baffle plate, and a part of the fuel gas is drawn into the negative pressure region and burned in the negative pressure region. A small and stable flame is generated. Therefore, the state of fire transfer to the main flame generated on the downstream side of the cylindrical header portion is greatly improved, and abnormalities such as vibration combustion are less likely to occur. In addition, if the flame holding gas is injected toward the negative pressure region from the portion between the cylindrical header portion of the peripheral wall of the fuel gas conduction pipe and the baffle plate, the main gas injected from the main gas fuel injection hole in the negative pressure region. The fuel gas and the fuel gas injected from the sub-gas fuel injection hole are mixed with the air, so that combustion in the negative pressure region can be further stabilized. And by providing a fuel gas conduction pipe flow path reducing member near the burner tip of the fuel gas conduction pipe and increasing the pressure in the fuel gas conduction pipe, propagation of pressure fluctuation due to combustion to the gas flow path can be suppressed, and combustion The stability of the can be further improved.

Sectional drawing in the front-end | tip part of the burner which is implementing this invention The perspective view in the front-end | tip part of the burner which is implementing this invention Plan view of FIG. 2 viewed from below

  An embodiment of the present invention will be described with reference to the drawings. 1 is a cross-sectional view of a tip portion of a burner embodying the present invention, FIG. 2 is a perspective view of the tip portion of the burner embodying the present invention, and FIG. 3 is a plan view of FIG. .

  The burner has a fuel gas conduction pipe 1 for supplying fuel gas at the center, and a cylindrical header portion 2 is provided at the tip of the fuel gas conduction pipe 1. The cylindrical header portion 2 has the same central axis as the fuel gas conduction pipe 1 and has a cylindrical shape having a diameter larger than that of the fuel gas conduction pipe 1, and closes the lower surface (front wall) of the cylindrical header portion 2. A main gas fuel injection hole 5 is provided on the peripheral wall. The main gas fuel injection holes 5 inject the fuel gas sent from the fuel gas conducting pipe 1 in the circumferential direction, and are provided at equal intervals in eight directions.

  On the outer periphery of the burner, a combustion cylinder 3 is provided which is concentric with the fuel gas conduction pipe 1 and is a cylinder surrounding the fuel gas conduction pipe 1 and the cylindrical header portion 2. Between the fuel gas conduction pipe 1 and the combustion cylinder 3 is an air supply flow path 12 for supplying combustion air, and closes the air supply flow path 12 from the outer surface of the fuel gas conduction pipe 1 to the inner surface of the combustion cylinder 3. A baffle plate 4 is provided. The baffle plate 4 is provided on the upstream side of the air flow at a predetermined distance from the cylindrical header portion 2. The baffle plate 4 has a primary air ejection hole 7 and a secondary air in order from the side close to the fuel gas conduction pipe. An ejection hole 8 and a tertiary air ejection port 9 are provided. The primary air ejection hole 7 and the secondary air ejection hole 8 are small holes that penetrate the baffle plate 4, and the tertiary air ejection port 9 is formed by cutting out the peripheral edge of the baffle plate 4. The secondary air ejection holes 8 and the tertiary air ejection ports 9 are arranged on lines extending radially from the central axis of the baffle plate in eight directions at equal intervals. The primary air ejection hole 7 is located at a position where the distance from the central axis of the fuel gas conduction pipe 1 to the primary air ejection hole 7 is shorter than the distance from the central axis of the cylindrical header part 2 to the peripheral wall of the cylindrical header part. It arrange | positions and the air injected directly from the primary air ejection hole 7 collides with the upper surface (rear wall) of the cylindrical header part 2. In the secondary air ejection hole 8, the distance from the central axis of the fuel gas conduction pipe 1 to the secondary air ejection hole 8 is longer than the distance from the central axis of the cylindrical header part 2 to the peripheral wall of the cylindrical header part. Place it in the position.

  A sub gas fuel injection hole 6, which is a small hole penetrating the peripheral wall, is provided in a portion sandwiched between the cylindrical header portion 2 and the baffle plate 4 of the fuel gas conduction pipe 1. Similarly to the main gas fuel injection hole 5, the subgas fuel injection holes 6 inject fuel gas in the circumferential direction, and are provided at equal intervals in eight directions. The main gas fuel injection hole 5 and the sub gas fuel injection hole 6 inject fuel gas in the same direction, and the injection direction is shifted by a half pitch from the radial line in which the primary air injection holes 7 are installed. Arrange them so that they do not overlap.

  The gas flow path of the fuel gas conduction pipe 1 is provided with a flow path reducing portion in the middle. A fuel gas conduction pipe flow path reducing member 11 that narrows the flow path of the fuel gas conduction pipe 1 is provided at the joint between the fuel gas conduction pipe 1 and the cylindrical header portion 2. The upper surface of the cylindrical header portion 2 is formed by opening an opening smaller than the diameter of the fuel gas conduction pipe 1 in the central axis portion of the fuel gas conduction pipe 1 and provided with a fuel gas conduction pipe flow path reducing member 11. As a result, the fuel gas sent through the fuel gas conduction pipe 1 has a pressure difference before and after the fuel gas conduction pipe flow path reducing member 11.

  The operation of this burner will be described. Combustion air sent through the air supply channel 12 is divided into a primary air ejection hole 7, a secondary air ejection hole 8, and a tertiary air ejection port 9, and is injected from the baffle plate 4 toward the tip of the burner. . Since the primary air that has passed through the primary air ejection hole 7 has the cylindrical header portion 2 immediately below, the primary air flows radially along the upper surface of the cylindrical header portion after colliding with the upper surface of the cylindrical header portion. Since air is jetted from the primary air ejection hole 7 and the secondary air ejection hole 8 at a high speed, a negative pressure region 10 is generated at a portion slightly downstream from the air flow on the downstream side of the baffle plate 4. The negative pressure region 10 is generated in a portion surrounded by the primary air ejection holes 7, the secondary air ejection holes 8, and the cylindrical header portion 2, and is shifted by a half pitch from the arrangement position of the primary air ejection holes 7. Eight negative pressure regions 10 are generated in the portion.

  Most of the fuel gas injected from the main gas fuel injection holes 5 provided on the peripheral wall of the cylindrical header portion 2 is injected sideways and then mixed with the combustion air from the baffle plate 4, and together with the combustion air, Burns while flowing downward. However, if the negative pressure region 10 exists, a part of the fuel gas injected from the main gas fuel injection hole 5 goes to the upper surface side of the cylindrical header portion 2 toward the negative pressure region 10. And since the primary air injected from the primary air ejection hole 7 becomes a radial flow by the cylindrical header part 2, the effect | action which pushes fuel gas downward to an air flow is small. Therefore, a part of the fuel gas injected from the main gas fuel injection hole 5 can be effectively led to the negative pressure region 10.

  The fuel gas taken into the negative pressure region 10 is mixed with air in the negative pressure region 10 and burned, and a small and stable flame is generated in the negative pressure region 10. By generating a stable flame between the cylindrical header portion 2 and the baffle plate 4, the state of fire transfer to the main flame generated on the downstream side of the cylindrical header portion 2 is greatly improved, such as vibration combustion. It is difficult to cause abnormalities.

  Further, a sub gas fuel injection hole 6 is provided in a portion between the cylindrical header portion 2 and the baffle plate 4 on the peripheral wall of the fuel gas conduction pipe, and the fuel gas is injected from the sub gas fuel injection hole 6 toward the negative pressure region 10. By doing so, the fuel gas injected from the sub-gas fuel injection hole 6 is also mixed in the negative pressure region 10. Thereby, the combustion in the negative pressure region 10 can be further stabilized.

  In addition, if the supply pressure of the fuel gas is low and the difference between the pressure of the gas injection section and the pressure in the furnace becomes small, the pressure change due to the formation of the combustion flame is transmitted in the direction of the fuel gas conduction pipe, and the gas injection pressure becomes unstable. This makes vibration combustion more likely to occur. When the fuel gas conduction pipe flow path reducing member 11 is provided at the connection portion of the cylindrical header portion 2 near the tip of the fuel gas conduction pipe 1, a pressure difference is generated before and after the fuel gas conduction pipe flow path reduction member 11. To do. Even if the pressure itself for supplying the fuel gas is the same, if the pressure in the fuel gas conduction pipe 1 increases, the pressure fluctuation transmitted to the fuel gas conduction pipe 1 can be suppressed. This can further improve the stability of combustion.

1 Fuel gas conduit
2 Cylindrical header
3 Combustion cylinder
4 Baffle plate
5 Main gas fuel injection hole
6 Subgas fuel injection hole
7 Primary air outlet
8 Secondary air outlet
9 Tertiary air outlet
10 Negative pressure range
11 Fuel gas conduction pipe flow path reduction member
12 Air supply flow path

Claims (3)

  A cylindrical header portion that is concentric with the fuel gas conduction pipe and has a diameter larger than that of the fuel gas conduction pipe at the tip of the fuel gas conduction pipe that supplies the fuel gas, and the periphery of the fuel gas conduction pipe serves as an air supply flow path. A baffle plate concentric with the fuel gas conduction pipe is provided around the fuel gas conduction pipe in the upstream portion of the air flow from the cylindrical header portion. The distance from the central axis of the fuel gas conduction pipe is the center of the cylindrical header portion. The primary air injection hole in the part shorter than the distance from the shaft to the peripheral wall, and the secondary air injection hole in the part where the distance from the central axis of the fuel gas conduction pipe is longer than the distance from the central axis of the cylindrical header part to the peripheral wall A plurality of the main gas fuel injection holes for injecting main fuel gas radially from the central axis of the cylindrical header portion are provided on the peripheral wall of the cylindrical header portion. Overlap Previously mixed burner, characterized in that provided in the position.   2. The premix burner according to claim 1, wherein the sub-fuel is disposed in a direction in which the peripheral wall of the portion sandwiched between the cylindrical header portion of the fuel gas conducting pipe and the baffle plate does not overlap with the primary air ejection hole installation position of the baffle plate. A premixed burner comprising a sub-gas fuel injection hole for injecting gas.   3. The premixing burner according to claim 1, wherein a fuel gas conduction pipe flow path reducing member for narrowing the gas flow path of the fuel gas conduction pipe is provided near the tip of the burner.

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