JPH0743099B2 - Premixed combustion device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a premix combustion apparatus in which air and fuel are premixed in a mixing chamber, and the mixture is blown into a combustion chamber through a flame hole structure to perform combustion.

[0002]

2. Description of the Related Art Conventionally, Bunsen combustion has been the mainstream of continuous combustors using gas fuel, and premixed combustion has been put into practical use in some cases. Meanwhile, as means of the NO _X reduction in the exhaust, it is effective premixed combustion at a lean air-fuel mixture. In addition, the applicant of the present application, in Japanese Patent Application No. 4-131906, includes a large number of annular slit flame holes as main flame holes and auxiliary flame holes surrounding the same in the combustion part as a premixing combustor. Provided is a premixing combustor having a width that is narrow enough to prevent flashback at the upstream side, widens toward the downstream side, and has a configuration in which the tip of a central tapered rod-shaped part that constitutes the slit is projected from the combustion surface.

[0003]

However, in the above Bunsen combustion, since a high concentration of NO _X is generated in the wake of the high temperature internal flame, it is difficult to realize a low NO _X combustor. Moreover, since a large space is required for the secondary combustion, it is difficult to realize high-load combustion. In addition, in the above-mentioned premixed combustion, since the combustion speed is generally low, the flame is easily blown off, and the combustion amount is limited. Further, in the premixed combustion, the flame stable range is narrow, and in the practical combustor, the combustor structure for widening the flame stable range is generally complicated. Furthermore, in the premixed combustor of Japanese Patent Application No. 4-131906, when the combustion surface is made of metal, the machining cost of the flame hole is required, so the manufacturing cost is high and the shape of the auxiliary flame hole is processed. Since the shape is limited to the circular shape, the flame holding effect is exerted only on a part of the outer periphery of the main flame hole, and it is not sufficient to suppress blowout of the entire main flame hole. Therefore, it was difficult to perform stable combustion under leaner conditions.

Therefore, the present invention solves the above-mentioned drawbacks of the prior art, utilizes the NO _X reduction effect of lean premixed combustion, achieves high load combustion, further reduces combustion noise, and has a high turndown ratio of combustion amount. It is an object of the present invention to provide an inexpensive premixed combustion device that can achieve the above.

[0005]

In order to achieve the above object, the premixed combustion apparatus of the present invention premixes the air sent by the blower means and the fuel sent by the fuel supply means in the mixing chamber. In the premixed combustion device, the air-fuel mixture is blown out through a flame hole structure including a main flame hole and an auxiliary flame hole to perform combustion, and the flame hole structure has a plurality of cylindrical metal pipes. And to form auxiliary flame holes between the cylindrical metal pipes by arranging them so that they are in contact with each other, and in each cylindrical metal pipe inner hole, concentric cylindrical or rod-shaped annular slit A main flame hole consisting of an annular slit is formed by arranging a forming member, and the main flame hole consisting of the annular slit is a slit near the downstream outlet from which the mixture enters and the upstream slit width is narrow. In that the wider is the first feature. In addition to the first feature, the premixed combustion device of the present invention has a second aspect in which, in the auxiliary flame holes between the cylindrical metal pipes, a throttle portion is formed upstream of the mixture. It has a feature.

[0006]

According to the first feature described above, the premixed mixture of fuel and air, which has been mixed to an appropriate concentration in advance, is supplied from below, enters the main flame hole and the auxiliary flame hole formed by the annular slit, and rises. Then, it is blown out from the flame hole outlet and burned. Since a cylindrical metal pipe is used to form the main flame hole and the auxiliary flame hole, there is no need for hole processing and it is easy to take a large length of the metal pipe. The turbulence of the premixture supplied to the holes can be adequately damped by the long walls of the metal pipe. Therefore, the main flame is stabilized by reducing the turbulence of the air-fuel mixture. In addition, all the areas surrounded by the adjacent cylindrical metal pipes become auxiliary flame holes,
Therefore, the total area of the auxiliary flame holes is increased, the flame holding effect of the auxiliary flame holes against blow-off of the main flame is remarkably improved, and the stability of the main flame is increased. In addition, the main flame hole has a narrow slit width upstream of the mixture entering and a wide slit width near the downstream outlet where the mixture is blown out. When jetting out more, the speed is reduced enough to form a stable flame in the flame hole. In addition, the second
According to the above feature, since the auxiliary flame hole is provided with the throttle portion upstream, the flow rate of the air-fuel mixture is sufficiently reduced by the throttle portion to form the deceleration flame and improve the flame holding effect.

[0007]

1 is a longitudinal sectional view of an apparatus for embodying the present invention, FIG. 2 is a plan view of the apparatus for embodying the present invention, and FIG. 3 is an enlarged view of a portion A in FIG.

An air blower 15 serving as an air blower is provided below the case 10.
The fuel supply pipe 13 from the fuel supply means (not shown) is connected to the passage from the blower 15. In the case 10, the lower part partitioned by the partition plate 14 is the mixing chamber 12, and the flame hole constituting body 20 is formed above the partition plate 14 with a small interval. This flame hole structure
Reference numeral 20 denotes a thin-walled cylindrical metal pipe 21 made of a heat-resistant metal or the like having an inner diameter d ₁ and an appropriate length L, arranged so as to be staggered in contact with each other. To
A cylindrical or rod-shaped annular slit forming member 22 whose tip is narrowed to a taper 22a is arranged concentrically, whereby a main flame hole consisting of an annular slit is formed in the cylindrical metal pipe 21 around the annular slit forming member 22. Form 25. Further, a substantially triangular gap surrounded by each of the three cylindrical metal pipes 21 arranged in contact with each other in a staggered manner is formed as an auxiliary flame hole 23.

The main flame hole 25 is set so that the slit width W on the upstream side where the premixed air enters is narrowed and the passage speed of the premixed air becomes higher than the combustion speed even when the combustion amount is reduced to the minimum. ing. Therefore, flashback can be prevented. On the other hand, in the vicinity of the downstream outlet of the main flame hole 25, the slit width W is widened by the taper 22a to slow the passage speed of the premixed gas. A throttle portion 24 is formed upstream of the auxiliary flame hole 23 into which the premixed air enters, and even when the combustion amount is reduced to a minimum, the passage speed of the premixed air is higher than the combustion speed, and flashback does not occur. The diameter is d ₂ .

During operation, after the combustion air from the blower 15 and the fuel from the fuel supply pipe 13 are thoroughly mixed in the mixing chamber 12,
It is distributed to the combustion section 11 through the holes of the partition plate 14. The premixed gas passing through the main flame hole 25 formed of an annular slit has its turbulence appropriately damped by friction between the cylindrical metal pipe 21 having an appropriate length and the wall surface of the annular slit forming member 22, and the slit width is further increased. The taper 22a having a wide W is decelerated to form a cone-shaped flame 18 in the main flame hole 25. Meanwhile, the auxiliary flame hole 23
The premixed gas that has passed through the throttle portion 24 is decelerated by friction with the outer walls of the three cylindrical metal pipes 21 and forms an auxiliary flame 19 composed of a decelerated flame at the outlet of the auxiliary flame hole 23. Incidentally, reference numeral 26 is an auxiliary flame hole formed on the outer periphery of the flame hole forming portion 20 and forms an auxiliary flame that is sufficiently decelerated.

Since the auxiliary flame hole 23 faces the entire periphery of the main flame hole 25, its flame holding effect is remarkably greater than that of the conventional auxiliary flame hole dispersed apart around the main flame hole. . Further, in the conventional method of forming the flame holes by the method of forming the holes in the metal plate or the ceramic plate, due to the manufacturing cost and other reasons, it is sufficient to slow down the turbulence of the air flow of the premixed gas passing therethrough. Although it was difficult to form a flame hole having a depth (length), in this embodiment, since the flame hole is formed using the metal pipe 21, it is not possible to increase the length L of the metal pipe 21. It is easy, and the turbulence of the premixed gas supplied to the main flame holes 25 is damped by the friction of the wall of the pipe, and the main flame 18 is stably formed.

In the above embodiment, the turndown ratio can be set to about 1: 5 to 6 without switching the combustion surface, which is about twice as wide as that of the conventional gas appliance. The amount of NO _X emitted is about 20 ppm at an excess air ratio of 1.5, which is about 1/5 of that of a conventional general Bunsen combustor.

[0013]

According to the premixed combustion apparatus of the first aspect of the present invention, a plurality of cylindrical metal pipes are used and they are arranged so as to be in contact with each other. A main flame consisting of an annular slit by forming an auxiliary flame hole between the cylindrical metal pipes and arranging a cylindrical or rod-shaped annular slit forming member coaxially in each cylindrical metal pipe inner hole. Since the holes are formed, the auxiliary flame holes are very easily formed. Moreover, since both the main flame hole and the auxiliary flame hole can be configured using a cylindrical metal pipe,
The length (depth) of the flame hole is large, that is, the length is sufficient to attenuate the turbulent flow of the premixed gas passing through it.
Can be obtained at a very low cost and easily. Further, the main flame hole consisting of the annular slit has a narrow slit width in the upstream side where the air-fuel mixture enters and a wide slit width in the vicinity of the downstream outlet from which the air-fuel mixture blows out. The blowing speed of the premixed air from the flame hole is low,
In addition, turbulence can be reduced, so that a stable flame can be formed and flashback can be suppressed. Moreover, since the auxiliary flame hole can be contacted with a sufficiently large area around the main flame hole, a strong flame holding effect can be exerted on the main flame, and thus the stability of the flame is further increased, which results in combustion noise. Will also be lower. As described above, high load combustion with a large maximum combustion amount is possible, and combustion with a high turndown ratio that does not cause flashback even with low input is possible. Of course, because of premixed combustion, low NO _X combustion is possible. According to the premixed combustion apparatus of claim 2, in addition to the effect of the configuration of claim 1, the auxiliary flame holes between the cylindrical metal pipes are located upstream of the mixture. Since the throttle portion is formed, the stability of the auxiliary flame can be further increased.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a device embodying the present invention.

FIG. 2 is a plan view of an apparatus for carrying out the present invention.

FIG. 3 is an enlarged view of a portion A of FIG.

[Explanation of symbols]

 12 Mixing chamber 13 Fuel supply pipe 15 Blower 20 Flame hole component 21 Cylindrical metal pipe 22 Annular slit forming member 22a Taper 23 Auxiliary flame hole 24 Throttle section 25 Main flame hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-210313 (JP, A) JP-A-5-302705 (JP, A) Actually open 52-4531 (JP, U) Actual-open Sho 55- 131408 (JP, U) Actually opened 55-136906 (JP, U) Actually opened 1-117426 (JP, U) Actually opened 52-126434 (JP, U) Actually opened 52-84039 (JP, U) Actual Kohei 2-45616 (JP, Y2)

Claims (2)

[Claims] 1. The air sent by the blower means and the fuel sent by the fuel supply means are premixed in a mixing chamber, and the mixture is passed through a flame hole forming body composed of main flame holes and auxiliary flame holes. A premixed combustion device configured to perform blowing and combustion, wherein the flame hole constituting body uses a plurality of cylindrical metal pipes, and by arranging them so that they are in contact with each other, While forming an auxiliary flame hole in each of the cylindrical metal pipe inner hole, to form a main flame hole consisting of an annular slit by arranging a cylindrical or rod-shaped annular slit forming member coaxially, and The main flame hole formed of an annular slit is a premixing combustion device characterized in that the upstream slit width where the air-fuel mixture enters is narrow and the slit width near the downstream outlet where the air-fuel mixture blows is wide. 2. The auxiliary flame holes between the cylindrical metal pipes,
The premixed combustion apparatus according to claim 1, wherein a throttle portion is formed upstream of the mixture.