JP3884596B2 - Premixing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a premixing device for mixing gas fuel and combustion air in advance, which is used in a combustion device such as a hot water boiler, a flue tube boiler, a cyclone ash melting device, etc. The present invention relates to a premixing device that uniformly mixes combustion air and combustion air into a microscopic region.
[0002]
[Prior art]
In general, in the premixed combustion method in which the fuel gas and the combustion air are separately supplied and mixed by the combustion burner, the fuel gas and the combustion air are mixed while being diffused. Therefore, the combustion is carried out while the rich mixture and the light mixture are formed, so that a place where the combustion temperature is locally high can be formed. Among NOx, especially thermal NOx is greatly affected by temperature, and if a high temperature portion exists locally, the NOx generation rate during combustion increases.
[0003]
Therefore, in a combustion apparatus such as a hot water boiler, a flue tube boiler, and a cyclone ash melting apparatus, a premixing system in which fuel gas and combustion air are mixed in advance before combustion has been adopted. In this premixing system, the fuel gas and the combustion air are uniformly mixed in advance, so that the maximum combustion temperature is low and the generated Nox can be kept low.
[0004]
However, in the conventional premixing device, the fuel gas and the combustion air can be mixed fairly uniformly, but it has been difficult to uniformly mix to a higher level . As a result, the combustion temperature is not stable, and the generation of a local high temperature portion in the combustion region has become the limit for reducing NOx.
[0005]
For example, FIG. 11 shows a premixed combustion apparatus disclosed in JP-A-8-86417. The fuel gas 84 is ejected from the fuel gas supply pipe 86 in a direction orthogonal to the combustion air 82 supplied by the blower 80. By this fluid collision, the combustion air 82 and the fuel gas 84 are primarily mixed, and after flowing in the direction of the arrow, the primary mixture 88 is combusted. Even if uniform mixing by fluid collision (hereinafter, the level of uniformity of mixing by fluid collision is referred to as macro mixing) is performed in this apparatus, the uniform mixing by the fluid collision of combustion air and fuel gas is performed. However, more uniform mixing (hereinafter, more uniform mixing at this level is called micro-mixing at the molecular level) was not performed, and this was the limit of NOx reduction. In addition, residual non-uniformity of mixing has also caused a backfire, that is, a phenomenon in which the flame flows back into the combustion nozzle.
[0006]
FIG. 12 shows a premixing device disclosed in JP-A-6-74423. The combustion air 82 supplied by the blower 80 is turned into a swirl flow by the swirl flow forming means 81, and the fuel gas is blown out orthogonally from the discharge holes 90 of the fuel gas supply pipe 86 with respect to the swirl flow. The primary mixture 88 macro-mixed by this ejection reaches the large diameter portion 92.
[0007]
However, in the large-diameter portion 92, macro-mixing is performed in the peripheral portion by overflow as shown in the figure, but micro-mixing is not performed. In other words, the macro mixing has already been performed at the time of forming the primary air-fuel mixture 88, and what should be performed next is local micro mixing at various points in the fluid. It must be said that this prior art is still insufficient in that this micromixing is not performed.
[0008]
FIG. 13 shows a premixed combustion apparatus disclosed in JP-A-5-231615. A primary air-fuel mixture in which fuel gas and combustion air have already been mixed flows from the inlet 95 through the conduit 94. The primary air-fuel mixture collides with an upright flat plate-like turbulent flow generating member 96, and Karman vortex 97 is generated from the upper and lower end edges as shown in the figure to form a turbulent flow region 98. This turbulent gas mixture is burned by the igniter 99.
[0009]
The turbulent flow generating member 96 generates a large Karman vortex as shown in the figure, and it is almost impossible to micromix the primary mixture at the molecular level. The point of mixing and stirring again using turbulent flow has advanced, but has not reached the level of micromixing.
[0010]
FIG. 14 also shows another premixed combustion apparatus disclosed in Japanese Patent Laid-Open No. 5-231615.
A difference from FIG. 13 is that a cone is used as the turbulent flow generation member 96. However, in such a large cone, a large Karman vortex street is generated at the periphery, and even if macro-mixing is possible, micro-mixing is impossible, as in FIG.
[0011]
[Problems to be solved by the invention]
As described above, a technique has been almost established in which a fuel gas is jetted and collided with a combustion air flow in an orthogonal shape to mix them both macroscopically. However, in this primary gas mixture, macro-mixing and stirring are performed, but micro-mixing that stirs air and gas at the molecular level is not performed.
[0012]
In addition, a technique for further mixing and stirring the primary gas mixture to obtain a secondary gas mixture has been developed. However, since the purpose of secondary mixing is to generate large vortices and large Karman vortices, micro-mixing cannot be performed. Although an attempt was made to increase the flow rate for micromixing, the pressure loss increased rapidly, and micromixing could not be performed sufficiently. There was also a blower limit for increasing the flow rate.
[0013]
Accordingly, an object of the present invention is to provide a premixing device for uniformly micromixing a macromixed primary mixture. Accordingly, it is an object of the present invention to provide a premixing device that can reduce the amount of NOx produced by lowering the combustion temperature of the secondary air-fuel mixture and prevent backfire of the combustion flame flowing back into the combustion device.
[0014]
[Means for Solving the Problems]
The invention according to claim 1 of the present invention is a premixing device for premixing fuel gas and combustion air before burning, a supply duct for supplying air and a large number of gases perforated in the circumferential direction of the supply duct It consists of a gas annular body that airtightly covers the gas ejection holes and these gas ejection holes. Gas is supplied into the gas annular body, and fuel gas is ejected perpendicularly to the air flow in the supply duct from the gas ejection holes. a fuel gas supply means for mixing both the primary, perpendicularly to the equally spaced intervals L ₃ the two to the primary mixture flow in the downstream position by a distance L ₀ from the primary mixing point width L ₁ is composed of a plurality of mixing accelerators having an angle width L ₂ and an angle angle θ arranged in a substantially V-shaped cross section , and the distance L _{0 is set} to L ₀ > 0.5D ₀ ( However, D ₀ to the diameter of the air supply duct), the Ang An angle θ to 60 ° to 100 °, the width L ₁ of the form piece with respectively regulated to 10 to 30 mm, toward the top line of the mixing promotion body on the upstream side, the primary mixture flow by both form piece The basic structure of the invention is to form a secondary gas mixture by mixing more uniformly.
[0015]
According to a second aspect of the present invention, there is provided a premixing device for premixing fuel gas and combustion air before combustion, a supply duct for supplying air and a gas supply tube provided in the diameter direction of the supply duct; The gas supply tube is made up of a number of gas injection holes perforated on the wall surface, and is arranged so that the gas injection direction is orthogonal to the air flow. The fuel gas is injected orthogonally to the air flow in the supply duct. a fuel gas supply means for mixing both the primary, perpendicularly to the equally spaced intervals L ₃ the two to the primary mixture flow in the downstream position by a distance L ₀ from the primary mixing point width L ₁ is composed of a plurality of mixing accelerators having an angle width L ₂ and an angle angle θ arranged in a substantially V-shaped cross section , and the distance L _{0 is set} to L ₀ > 0.5D ₀ ( However, D ₀ to the diameter of the air supply duct), the angle angle The θ to 60 ° to 100 °, the width L ₁ with respectively regulating the 10~30mm of the form piece, directed to the top line of the mixing promotion body on the upstream side, and more said primary mixture flow by both form piece The basic structure of the invention is to form a secondary mixture by mixing uniformly.
[0016]
The invention according to claim 3 is the invention according to claim 1 or 2, wherein the mixing accelerator is a mixing accelerator in which a plurality of cut pieces are formed by making zigzag notches on the edge of the shape piece. Is.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described in detail with reference to FIGS.
1 to 3 show a first embodiment of a premixing device according to the present invention, in particular FIG. 1 is a longitudinal sectional view thereof, FIG. 2 is a perspective view of a mixing accelerator, and FIG. 3 is a CC line of FIG. It is sectional drawing. Combustion air is supplied in the direction of arrow a from a blower (not shown) through the supply duct 2 having a circular cross section. A large number of gas ejection holes 4 are formed in the circumferential direction of the supply duct 2, and a gas annular body 6 is provided to airtightly cover these gas ejection holes 4 from the outside. The fuel gas is supplied from the gas pipe 8 in the direction of the arrow b, and the gas annular body 6 becomes a gas reservoir and blows out in the direction of the arrow c through the gas ejection hole 4.
[0018]
A mixing accelerator 10 is disposed in the supply duct 2.
[0019]
As can be seen from FIG. 2, the mixing accelerator 10 is an angle in which the two shaped pieces 28, 28 are opened at an angle angle θ, and the angle angle θ is 60 ° to 100 °, preferably 80 ° to 100 °. is there. The width L ₁ of the shape piece 28 is 30 mm or less, preferably 10 to 20 mm.
[0020]
A plurality of the angle-shaped mixing accelerators 10 are arranged at equal intervals over the entire length of the cross section of the supply duct 2 so that the top line 30 faces upstream. The interval L ₃ is set to 0.5L ₂ <L ₃ <2L ₂ where the angle width is L ₂ . Also, the efficiency of micromixing is increased when as many as possible the placing mixing promotion body 10 by reducing the L _2.
[0021]
The distance L ₀ between the gas ejection hole 4 and the mixing accelerator 10 is preferably as long as possible, but it is desirable that L ₀ <0.5D ₀ compared to the diameter D ₀ of the circular supply duct. Further, in order to surely perform the secondary mixing (micro mixing), it is desirable that the flow rate of the air-fuel mixture at the position of the mixing accelerator 28 is set to 10 m / s or more. When this flow rate is fast, secondary mixing is effective if the interval L ₃ is large.
[0022]
Next, the operation of the first embodiment will be described. As can be seen from FIG. 1 and FIG. 3, the fuel gas is ejected from the ejection port 4 in the direction of arrow c through the gas annular body 6. Combustion air in the direction of arrow a is primarily mixed in a large turbulent state with fuel gas that collides with fluid in an orthogonal shape. The primary mixture gradually becomes a stable flow from a large turbulent state, and this process is called macro mixing.
[0023]
As indicated by an arrow f, this primary air-fuel mixture is diverted from the top line 30 of the mixing accelerator 10 to the left and right, and forms a minute Karman vortex at its edges 28a and 28a while going up the shape piece 28. Since the Karman vortex is very small, it gradually becomes stable in the downstream flow process, and becomes a uniformly mixed secondary mixed flow g. Mixing after the mixing promotion body 10 with micromixing, the angle width L ₂ of the mixing promotion body 10 and smaller when more sequences number, micromixing takes place more granular.
[0024]
4 to 7 show a second embodiment of the premixing device according to the present invention. 4 is a longitudinal sectional view, FIG. 5 is a perspective view of a mixing accelerator, FIG. 6 is a perspective view of another mixing accelerator, and FIG. 7 is a sectional view taken along line EE of FIG.
In describing the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, the description thereof is omitted, and different parts are described.
[0025]
The second embodiment is different from the first embodiment in that the cross section of the supply duct 2 is rectangular and the shape of the angle-shaped mixing promoting body 10 is slightly different. The point that the cross section of the supply duct 2 is rectangular is the same as that of the first embodiment, and thus the description thereof is omitted.
[0026]
The mixing promoting body 10 shown in FIG. 5 forms a large number of cut pieces 32 by making zigzag notches on the edge 28a. Both ends of the cut piece 32 are edges 32 a, and as a result, twice as many edges 32 a as the cut pieces 32 are formed in one shape piece 28. In this example, since the edge 28a is left in the cut piece 32, the number of the edges 32a is small.
[0027]
In the mixing promoting body 10 shown in FIG. 6, since the notches are formed until the end edge 28a is completely lost, an extremely large number of cut pieces 32 can be formed, and as a result, the number of edges 32a can be increased rapidly.
[0028]
When the primary air-fuel mixture arrives at the mixing accelerator 10 shown in FIG. 5 or FIG. 6, as shown by the arrow f, first, the divided pieces 28 and 28 are first divided up and down, and each divided flow is the edge of the cut piece 32. A small Karman vortex is formed by further diverging left and right by 32a and 32a. When there are a large number of cut pieces 32, a large number of very small Karman vortices are formed, and therefore a uniform and uniform secondary mixed flow g is formed at the stage of a slight flow down.
[0029]
8-10 has shown 3rd Embodiment of the near-earing apparatus which concerns on this invention. 8 is a longitudinal sectional view, FIG. 9 is a sectional view taken along line FF in FIG. 8, and FIG. 10 is a sectional view taken along line GG in FIG. In the description of the third embodiment, the same parts as those of the second embodiment are denoted by the same reference numerals, the description thereof is omitted, and different parts are described.
[0030]
This third embodiment shows another example of the fuel gas supply means. Unlike the gas annular body 6, the third embodiment includes a gas supply cylinder 7 provided in the diameter direction of the supply duct 2. A large number of gas ejection holes 4 are formed in the axial direction on the side surface of the gas supply cylinder 7 at a position orthogonal to the air supply direction a, and fuel gas is ejected in the direction of arrow c.
[0031]
In this embodiment, since the gas supply cylinder 7 is located in the center of the supply duct 2, it has a surface where the flow of combustion air is disturbed, but the primary mixing with the fuel gas is performed on both sides of the gas supply cylinder 7. Done in If the primary mixed flow on both sides also flows down a little, they merge with each other, and after the secondary mixing by the mixing accelerator 10, there are almost the same effects as in the second embodiment, so the description thereof is omitted.
[0032]
The present invention is not limited to the above-described embodiments, and includes various modifications, design changes and the like within the technical scope without departing from the technical idea of the present invention.
[0033]
【The invention's effect】
According to the present invention, after the fuel gas and the combustion air are primarily mixed macroscopically, the primary mixed gas can be secondarily mixed microscopically, so that a uniform and uniform mixed gas can be generated. Therefore, even if this air-fuel mixture is combusted, there is no unevenness in the combustion temperature, NOx can be reduced, and at the same time backfire can be prevented, and uniform mixing with low pressure loss becomes possible.
[0034]
According to the invention of claim 3, higher efficiency can be achieved.
[0035]
According to the invention of claim 1, since the fuel gas supply means is not in the supply duct, the primary mixing of the fuel gas and the combustion air can be performed in a wide place and is not subject to mechanical disturbance. High efficiency of primary mixing can be achieved.
[0036]
According to the invention of claim 2, the structure of the fuel gas supply means is simple and easy to manufacture. In addition, since the air flow velocity in the vicinity of the gas ejection portion is fast, primary mixing and secondary mixing can be reliably performed even when the supply pressure of the fuel gas is low.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a premixing device according to a first embodiment of the present invention.
FIG. 2 is a perspective view of a mixing accelerator according to the first embodiment.
FIG. 3 is a cross-sectional view taken along the line CC of FIG.
FIG. 4 is a longitudinal sectional view of a premixing device according to a second embodiment of the present invention.
FIG. 5 is a perspective view of a mixing accelerator according to a second embodiment.
FIG. 6 is a perspective view of another mixing accelerator according to the second embodiment.
7 is a cross-sectional view taken along line EE in FIG.
FIG. 8 is a longitudinal sectional view of a premixing device according to a third embodiment of the present invention.
9 is a cross-sectional view taken along line FF in FIG.
10 is a cross-sectional view taken along the line GG of FIG.
FIG. 11 is a perspective view of a first conventional example of a premixed combustion apparatus.
FIG. 12 is a cross-sectional view of a main part of a second conventional example of a premix combustion apparatus.
FIG. 13 is a cross-sectional view of a third conventional example of the premixed combustion apparatus.
FIG. 14 is a cross-sectional view of a fourth conventional example of the premixed combustion apparatus.
[Explanation of symbols]
2 is a supply duct, 4 is a gas ejection hole, 6 is a gas annular body, 8 is a gas pipe, 10 is a mixing accelerator, 28 is a shape piece, 28a is an edge, 30 is a top line, 32 is a cut piece, 32a Is an edge, 80 is a blower, 82 is a combustion air, 84 is a fuel gas, 86 is a fuel gas supply pipe, 88 is a primary gas mixture, 90 is an ejection hole, 92 is a large diameter portion, 94 is a pipe line, and 95 is 96 is a turbulent flow generating member, 97 is a Karman vortex, 98 is a turbulent flow region, and 99 is an igniter.

Claims (3)

In a premixing device that premixes fuel gas and combustion air before burning, a supply duct for supplying air is supplied, a number of gas ejection holes formed in the circumferential direction of the supply duct, and these gas ejection holes A gas annular body that hermetically covers the gas, and a gas that supplies gas into the gas annular body and jets the fuel gas perpendicularly to the air flow in the supply duct from the gas ejection holes to primarily mix them. An angle angle θ is formed between the supply means and two pieces of width L ₁ arranged at equal intervals at an interval L ₃ perpendicular to the primary mixed airflow at a position downstream from the primary mixing point by a distance L _0. in is composed of a plurality of mixing promotion of consisting angle of the angle width L ₂ which is arranged in a substantially V-shaped cross section, and wherein the distance L ₀ L _0> 0.5D ₀ (where, D ₀ is the air supply duct The angle θ is 60 ° to 100 ° , The width L ₁ of the form piece with respectively regulated to 10 to 30 mm, 2 a top line of the mixing promotion body toward the upstream side, a mixture of the primary mixture flow more uniformly by both type Single order A premixing device characterized by forming a mixture. In a premixing device that premixes fuel gas and combustion air before burning, a supply duct that blows air, a gas supply cylinder installed in a diameter direction of the supply duct, and a wall surface of the gas supply cylinder A fuel which is composed of a large number of gas ejection holes and is arranged so that the gas ejection direction is perpendicular to the air flow, and the fuel gas is ejected orthogonally to the air flow in the supply duct to primarily mix them. An angle angle is formed between the gas supply means and two pieces of the width L ₁ arranged at equal intervals at an interval L ₃ perpendicular to the primary mixed airflow at a position downstream from the primary mixing point by a distance L _0. consists plurality mixing promotion of consisting angle of substantially V-shaped section angle width is arranged in L ₂ in theta, and the distance L ₀ L _0> 0.5D ₀ (where, D ₀ is the air supply duct The angle θ is 60 ° to 100 °. The width L ₁ with respectively regulating the 10~30mm of the form piece, directed to the top line of the mixing promotion body on the upstream side, more uniformly mixed to secondary mixing the primary mixture flow by both form piece A premixing device characterized by forming a gas.   The premixing device according to claim 1 or 2, wherein a zigzag notch is formed at an edge of the shape piece of the mixing accelerator to form a plurality of cut pieces.

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