JP3951189B2 - Burner - Google Patents

Description

  The present invention relates to a burner capable of stabilizing combustion.

  In a burner of a combustion apparatus that burns with combustion air that has a low excess air ratio and is slightly larger than the theoretical air volume, such as a business boiler, in order to suppress the generation of nitrogen oxides NOx, An effective means is to form a diffusion flame in which combustion proceeds while mixing fuel and air in the combustion chamber.

  In diffusion combustion of gaseous fuel, in order to ensure flame holding properties, two types of bluff body flame holders are often provided in the burner. FIG. 4 is a view for explaining the structure of an example of such a conventional burner, FIG. 4 (a) is a sectional view of the burner, and FIG. 4 (b) is a front view of a burner throat portion of the burner. Referring to the figure, combustion air is supplied to a burner throat 49 of a burner 40 from a wind box 44 as primary air, secondary air, and tertiary air. Arrow 45 indicates primary air, arrow 46 indicates secondary air, and arrow 47 indicates the flow of tertiary air. Reference numeral 48 denotes an air register that directs the flow of tertiary air. The burner 40 is provided with a plurality of gas fuel ejection nozzles (gas spuds) 43, each of which is provided with a flame holder (frame holder) 50 to hold the flame for each gas spud 43, and generally in the center of the burner. A method in which a large common flame holder (impeller) 51 as compared with the frame holder 50 is provided to enhance the flame holding of the burner 40 as a whole is employed. Gas fuel is supplied to the gas spud 43 through the fuel gas ring 42 as indicated by an arrow 41.

The above conventional technique exhibits excellent flame holding performance when exhaust gas mixing for reducing nitrogen oxide NOx is not performed or when the exhaust gas mixing ratio is small, that is, when the O2 concentration of the wind box 44 is about 19% or more. To do. However, when the O2 concentration in the wind box 44 is less than about 19% due to an increase in the exhaust gas mixture ratio, unstable combustion may occur due to a change in the flame holding form. The reason for the unstable combustion will be described in order below.
(1) First, the decrease in O2 concentration in the wind box 44 triggers the flame holding performance in the frame holder 50, and the oxygen consumption in the vicinity of the frame holder 50 decreases.
(2) Next, the oxygen consumption reduction in the vicinity of the frame holder 50 contributes to the combustion in the wake of the impeller 51, so that the flame holding performance in the wake of the impeller 51 is enhanced.
(3) Assisted by strengthening the flame holding in the downstream of the impeller 51, improving the flame holding performance in the frame holder 50, and increasing the oxygen consumption in the vicinity of the frame holder 50.
(4) O2 partial pressure downstream of the impeller 51 decreases due to an increase in oxygen consumption in the vicinity of the frame holder 50, and flame holding performance downstream of the impeller 51 decreases.
(5) The flame holding performance in the frame holder 50 is also reduced due to the reduction in the flame holding performance in the wake of the impeller 51, the state returns to the state (1), and the steps (1) to (5) are repeated.
The above phenomenon is caused by unstable combustion as a result of the two types of flame holding mechanisms of the frame holder 50 and the impeller 51 interfering with each other.

  An object of the present invention is to provide a burner that does not cause unstable combustion even when the O2 concentration of combustion air is low.

The solution to the above problem is that a secondary air flow path is formed surrounding the primary air flow path, and a plurality of gaseous fuel injection nozzles are arranged in the secondary air flow path around the primary air flow path. In this burner, an annular flame stabilizer is provided between the outer periphery of the tip end portion of the primary air flow path and the ejection nozzle, and an annular flame stabilizer is provided on the outer periphery of the tip end portion. The side nozzle hole is located on the downstream side of the flame holder and is formed toward the axis of the flame holder, and includes a liquid fuel burner in the primary air flow path. A flame holder at the tip of the liquid fuel burner, and the flame holder at the tip of the liquid fuel burner in the primary air flow path upstream of the flame holder provided at the tip of the primary air flow path or Position adjusting means for moving in the axial direction of the primary air flow path so as to be located downstream, Serial Ri and ejection nozzle Na is formed so as to be burned by switching the liquid fuel burner, flame holder tip of the liquid fuel burner, when burning a gaseous fuel, provided at the tip portion of primary air passage coercive It is positioned upstream of the flame unit, when combusting liquid fuel, is located downstream of the flame stabilizer provided at the tip portion of the primary air passage and gist of that by comprising.

  Furthermore, the gist also includes a burner provided with means for adjusting the flow rate of the primary air and / or the secondary air.

  The fuel injected from the side injection port is annularly held by a single flame holder and burned to form a flame holding region. Since such a flame holder is the only flame holder in the entire burner, a plurality of flame holding mechanisms interfere with each other so that unstable combustion does not occur. Since the fuel injected from the main nozzle is injected around the flame holding area, it is ignited by the flame holding area to form a diffusion flame.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the structure of a burner according to an embodiment of the present invention. FIG. 1A is a sectional view of such a burner, and FIG. 1B is a front view of a burner throat portion of such a burner. In the figure, combustion air is supplied to a burner throat portion 5 of a burner 1 by a wind box 6 separately into primary air and secondary air. The burner 1 also has a primary air sleeve 2 serving as a primary air flow path through which combustion primary air flows, and a combustion primary flow that is provided in the burner throat portion 5 and flows from the primary air flow path 5. A primary air discharge port 3 that discharges air and a secondary air discharge port 4 that is disposed around the primary air discharge port and discharges secondary air for combustion are provided. Arrow 7 indicates the flow of primary air, and arrow 8 indicates the flow of secondary air.

  A flame holder 14 is provided at the tip of the primary air discharge port 3. The flame holder 14 is annular and is the only flame holder in the burner 1 of the present embodiment. In the burner 1 of the present embodiment, a flame holder is additionally provided at the tip of the gas spud 9 or the like. Not. In the flame holder 14, the axial cross section of the primary air sleeve 2 protrudes from the tip of the primary air discharge port 3 in a dogleg shape as shown in FIG.

  For example, eight gas spuds 9 are provided in the burner throat 4, and the tip portion thereof is disposed at the tip portion of the secondary air discharge port 4. A side nozzle 11 and a main nozzle 12 are provided at the tip of the gas spud 9. The fuel gas is supplied to the gas spud 9 through the fuel gas ring 13 as shown by an arrow 15. About 10% to 50% of the fuel gas is injected from the side nozzle 11, and the remaining 90% to 50% is injected from the main nozzle 12. Reference numeral 16 denotes the fuel gas from the side injection hole 11 injected in this manner, and reference numeral 17 denotes the fuel gas injected from the main injection hole 12.

  Reference numeral 19 denotes a primary air damper that adjusts the flow rate of the primary air, and reference numeral 10 denotes an air register that directs the flow of the secondary air. By controlling the distribution of the primary air and the secondary air by the primary air damper 19 and the air register 10, the flow rate of the primary air and the secondary air can be adjusted to enhance the stable combustion condition. That is, the local air-fuel ratio of the flame holder 14 can be optimized by adjusting the opening degree of the primary air damper 5, and the swirling strength of the secondary air is changed by adjusting the opening degree of the air register 10, and the tubular recirculation is performed. The size of the flame holding area 18 can be optimized.

  Next, a burner according to another embodiment of the present invention will be described. FIG. 3 is a view for explaining the structure of a burner according to another embodiment of the present invention. FIG. 3A is a cross-sectional view of such a burner, and FIG. 3B is a front view of a burner throat portion of the burner. 1 and the like are members similar to the members described with reference to FIG. The burner according to this embodiment is a burner in which both fuel gas and liquid fuel can be combusted, and the present invention is applied to a burner that can select which fuel to burn by switching.

  The burner of this embodiment is provided with a liquid fuel burner 20 for burning liquid fuel in the primary air sleeve 2. The liquid fuel burner 20 has a liquid fuel injection port 22 and a second flame holder having a circular or rectangular shape at the front end for stabilizing the combustion of the liquid fuel injected from the injection port 22. An impeller 21 is provided. Further, a liquid fuel burner slide device (not shown) that moves the tip of the liquid fuel burner 20 including the injection port 22 and the impeller 21 in the axial direction of the primary air sleeve 2 manually or automatically is provided by known means. As a result, the tip of the liquid fuel burner 20 can be accommodated in the primary air sleeve 2 as shown in FIG. 3A or can be positioned at the tip 21 ′ of the flame holder 14. Thus, when the fuel gas is burned, the tip of the liquid fuel burner 20 is accommodated in the primary air sleeve 2 so as not to interfere with the flame holding mechanism by the flame holder 14.

  Next, operation | movement of the burner 1 concerning a present Example is demonstrated. The fuel gas injected from the side nozzle 11 is held by the flame holder 14 and burned. As shown in FIG. 2, an annular recirculation flame holding area 18 is formed in the downstream of the flame holder 14 due to the bluff body effect. It is formed. Fuel gas is injected from the main nozzle 12 around the flame-holding region 18, and the gas is ignited and burned by the flame in the flame-holding region 18 to form a diffusion flame. Since the flame holder 14 is the only flame holder in the entire burner 1, a plurality of flame holding mechanisms interfere with each other so that unstable combustion does not occur. In addition, since the flame holder 14 is an annular flame holder, stable combustion can be maintained as a whole of the flame holding mechanism even if fluctuation occurs in a part of the recirculation flame holding region 18.

Further, as described above, the primary air damper 19 and the air register 10 appropriately adjust the flow rates of the primary air and the secondary air to optimize the local air-fuel ratio of the flame holder 14, and the recirculation flame holding region. The size of 18 is optimized.

  Further, with respect to the burner 1 described with reference to FIG. 3, when the fuel gas is burned, the tip of the liquid fuel burner 20 is placed on the primary air sleeve 2 so as not to interfere with the flame holding mechanism by the flame holder 14. Housed inside. When burning the liquid fuel, the tip of the liquid fuel burner 20 is positioned at the tip 21 ′ of the flame holder 14. As a result, the liquid fuel is held by the impeller 21 and burned, and is stably burned without being interfered by the flame holder 14.

  According to the burner 1 according to the present embodiment described above, the flame holder 14 is the only flame holder in the entire burner 1, so that a plurality of flame holding mechanisms interfere with each other so that unstable combustion does not occur. .

  In addition, since the flame holder 14 is an annular flame holder, stable combustion can be maintained as a whole of the flame holding mechanism even if fluctuation occurs in a part of the recirculation flame holding region 18.

  In the burner 1 described with reference to FIG. 3, the tip of the liquid fuel burner 20 can be accommodated in the primary air sleeve 2, so that the liquid fuel is burned even when the fuel gas is burned. Also when performing the combustion, the flame is held by only one of the flame holder 14 and the impeller 21 and burned, and unstable combustion is performed even in a burner that can select which of fuel gas and liquid fuel to burn by switching. It does not occur.

  Furthermore, the local air-fuel ratio of the flame holder 14 can be optimized by the primary air damper 5 and the air register 10, and the size of the recirculation flame holding area 18 can be optimized.

    According to the burner according to the present invention described above, since the flame holder is the only flame holder in the entire burner, a plurality of flame holding mechanisms interfere with each other so that unstable combustion does not occur.

  Further, since the flame holder is an annular flame holder, stable combustion can be maintained as a whole of the flame holding mechanism even if fluctuation occurs in a part of the flame holding region.

  Further, in the burner provided with the fuel injection port, the fuel injection port can be accommodated in the primary air discharge port. Therefore, when the fuel gas is burned or when the liquid fuel is burned, the fuel burner is annular. Even in the burner in which the flame is held by only one of the flame holder and the second flame holder and burned and it is possible to select which one of the fuel gas and the liquid fuel is burned, unstable combustion does not occur. .

It is a figure explaining the structure of the burner concerning one Example of this invention, Fig.1 (a) is sectional drawing of this burner, FIG.1 (b) is a front view of the burner throat part of this burner. It is a figure explaining the recirculation flame holding area formed with the burner concerning one Example of this invention. It is a figure explaining the structure of the burner concerning the other Example of this invention, Fig.3 (a) is sectional drawing of this burner, FIG.3 (b) is a front view of the burner throat part of this burner. . It is a figure explaining the structure of the conventional burner, Fig.4 (a) is sectional drawing of this burner, FIG.4 (b) is a front view of the burner throat part of this burner.

Explanation of symbols

1 Burner
9 Gas spat 11 Side nozzle 12 Main nozzle 14 Flame stabilizer

Claims (1)

In a burner in which a secondary air flow path is formed surrounding a primary air flow path, and a plurality of gaseous fuel ejection nozzles are arranged in the secondary air flow path around the primary air flow path,
An annular flame stabilizer is provided on the outer periphery of the distal end portion and extends between the outer periphery of the distal end portion of the primary air flow path and the ejection nozzle, and a main injection port and a side injection port are formed at the distal end portion of the ejection nozzle, The side nozzle is located on the downstream side of the flame holder and is formed toward the axis of the flame holder,
A liquid fuel burner is provided in the primary air channel, a flame holder is provided at the tip of the liquid fuel burner, and a flame holder at the tip of the liquid fuel burner is provided at the tip of the primary air channel. Position adjusting means for moving in the axial direction of the primary air flow path so as to be located in or downstream of the primary air flow path upstream of the flame stabilizer, and the jet nozzle of the gaseous fuel and the liquid fuel burner are provided Ri Na is combustible formed by switching,
The flame holder at the tip of the liquid fuel burner is positioned upstream of the flame holder provided at the tip of the primary air flow path when burning gaseous fuel, and when the liquid fuel is burned, burner, characterized in Rukoto such by positioning downstream of the flame stabilizer provided at the tip portion of the air passage.

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