JPH09196315A - Liquid combustion burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a flame of a liquid combustion burner by providing a vaporization flame holder plate in the vicinity of a downstream side of a solid flame holder plate in which the neighbourhood of a central part thereof is recessed toward an upperstream side so as to face the flame holder plate, and forming a precombustion space between both flame holder plates. SOLUTION: A flame holder plate 26 is provided in the vicinity of a tip end in a combustion cylinder 2. The flame holder plate 26 is adapted such that the neighbourhood of a center thereof is cone-shaped which is recessed toward an upstream side. A hole 28 is provided substantially at the center of the flame holder plate 26, and a nozzle 12 is provided in the vicinity of the upstream side of the hole 28. A fuel 16 injected from the nozzle 12 is injected toward the downstream side of the flame holder plate 26 through the hole 28. Combustion air is also supplied to the downstream side from the hole 28. Further, a disk shaped vaporization flame holder plate 30 is provided in the vicinity of the downstream side of the flame holder plate 26 so as to oppose the flame holder plate 26 whereby a precombustion space 32 is formed between the vaporization flame holder plate 30 and the flame holder plate 26. A central axis of the vaporization flame holder plate 30 and the flame holder plate 26 is arranged substantially on a central axis of the combustion cylinder 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid combustion burner using a liquid fuel, and more specifically to a means for enabling a shortened flame thereof.

[0002]

2. Description of the Related Art FIG. 14 is a sectional view showing an example of a conventional liquid combustion burner.

This burner is provided near the tip of the combustion cylinder 2 to which combustion air 4 is supplied from the outside, and liquid fuel 16 is supplied from the outside to atomize it. A nozzle 12 for injecting toward the tip of the combustion cylinder 2 (that is, to the downstream side), a flame holding plate 6 provided near the nozzle 12 in the combustion cylinder 2 for stabilizing a flame 18, and this flame holding plate. The combustion air 4 supplied between the combustion cylinder 2 and the outer peripheral portion of the combustion cylinder 2 and the inner wall of the combustion cylinder 2 is held by the flame holding plate 6
And an annular air port 10 for ejecting the air from the surrounding area to the downstream side. The ignition device is not shown (the same applies to the embodiments described later).

The combustion cylinder 2 has, for example, a cylindrical shape, and the inside thereof is normally burned via a wind box 3 which functions to stabilize the flow of the combustion air 4 as shown in the figure. Air 4 is supplied.

The flame holding plate 6 has a function of stabilizing the flame 18 by creating a negative pressure region at the downstream side thereof with the flow velocity of the combustion air 4 and bringing the ignition surface close to the flame holding plate 6. In this example, it has a disc shape. In this example, a hole 8 through which the fuel 16 injected from the nozzle 12 passes is provided at the center thereof. Further, in order to prevent the soot from adhering to the surface of the flame holding plate, a plurality of small holes 9 or slits for ventilation may be provided in the plate surface of the flame holding plate 6.

[0006]

In the above liquid combustion burner, the combustion air 4 is ejected from the tip of the combustion tube 2 in the axial direction thereof, and the fuel 16 is simply injected from the nozzle 12 toward the downstream side. Flame 18
14 is shown in FIG. 14 up to the middle thereof, but is elongated along the axis of the burner.

However, in recent years, space saving and cost reduction have been promoted as a tendency of boilers and the like, and the combustion chambers of the boilers and the like have also been changed to those having a short depth dimension in accordance therewith. However, it has become necessary to shorten the flame, and the conventional burner shown in FIG. 14 cannot meet this requirement because the flame 18 is elongated.

Therefore, the main object of the present invention is to provide a liquid combustion burner capable of shortening the flame.

[0009]

In order to achieve the above object, the liquid combustion burner according to the present invention has a flame-retardant plate having a three-dimensional shape in which the vicinity of its central portion is recessed upstream, and the flame-retardant plate is downstream. It is characterized in that a vaporization flame holding plate is provided near the side so as to face the flame holding plate, and a pre-combustion space is formed between both flame holding plates.

According to the above structure, most of the fuel injected from the nozzle hits the vaporization flame stabilizing plate provided on the downstream side and accelerates vaporization while heading toward the outer peripheral direction thereof.
An annular flame is formed from the pre-combustion space toward the outer circumference thereof. On the other hand, the combustion air is ejected almost axially from the outlet of the combustion tube, so that the flame toward the outer peripheral direction and the combustion air flowing in the axial direction are combined, and the pre-combustion occurs near the outlet of the combustion tube. A cone-shaped flame that spreads greatly from the space to the downstream side is formed. as a result,
Can shorten the flame.

[0011]

1 is a sectional view showing an example of a liquid combustion burner according to the present invention. The same or corresponding portions as those of the conventional example in FIG. 14 are designated by the same reference numerals, and the differences from the conventional example will be mainly described below.

In this embodiment, the combustion cylinder 2 described above is used.
A flame holding plate 26, which corresponds to the flame holding plate 6 of the conventional example, is provided in the vicinity of the tip portion of the inside. In this example, the flame holding plate 26 has a mortar shape (in other words, a conical shape) in which the vicinity of the central portion is recessed upstream. The hole 2 is formed at the center of the flame holding plate 26.
8 is provided, and in this example, the above-mentioned nozzle 12 is provided near the upstream side of this hole 28, and the fuel 1 injected from the nozzle 12 is provided.
6 is injected through the hole 28 to the downstream side of the flame stabilizing plate 26. The combustion air 4 is also slightly supplied to the downstream side from the hole 28. When the amount of combustion is large, a plurality of small holes 2 for ventilation are provided in the plate surface of the flame holding plate 26.
9 or slits may be provided, but if the combustion amount is small, the small holes 29 or slits are unnecessary.

Further, in this example, the annular air port 10 as described above is formed between the outer peripheral portion of the flame holding plate 26 and the inner wall of the combustion tube 2 described above.

Further, in the present example, a disk-shaped vaporization flame holding plate 30 is provided near the downstream side of the flame holding plate 26 so as to face the flame holding plate 26, whereby the vaporization flame holding plate 30 is provided. A pre-combustion space 32 is formed between the plate 30 and the flame holding plate 26. The central axes of the vaporizing flame holding plate 30 and the flame holding plate 26 are the nozzle 12 and the combustion cylinder 2 in this example.
It is located almost on the central axis of.

In this liquid combustion burner, the nozzle 1
Most of the fuel 16 sprayed from No. 2 hits the vaporization flame stabilizing plate 30 provided on the downstream side and heads in the outer peripheral direction (see arrow E), so the annular flame 18 heading in the outer peripheral direction from the pre-combustion space 32. Will be formed. on the other hand,
Since the combustion air 4 is ejected from the outlet of the combustion tube 2 in the substantially axial direction (see arrow F), the flame 18 directed toward the outer periphery and the combustion air 4 flowing in the axial direction are combined (more The flames 18 are directed obliquely outward as indicated by an arrow G, and their forces are combined, if they are accurately expressed), and are directed toward the downstream side of the pre-combustion space 32 near the exit of the combustion tube 2. Conical flame 1 that spreads widely in a radial direction
8 are formed. As a result, the flame 18 can be shortened, that is, shortened.

In this case, unlike the case where the flame holding plate 26 is formed in a three-dimensional shape by making the flame holding plate 26 three-dimensional as described above, a relatively large volume of pre-combustion is provided between the flame holding plate 26 and the vaporizing flame holding plate 30. A space 32 is formed, and the heat generated by the combustion (pre-combustion) of the fuel 16 therein causes the fuel 1 sprayed therein
Vaporization of 6 is promoted. Moreover, on the downstream side of the vaporizing flame stabilizing plate 30, due to the flame 18 and the air flow (see arrow F) ejected from the air port 10 at the outer peripheral portion of the flame stabilizing plate 26, the exhaust gas circulation flow as shown in the illustrated example. 34 is generated, and the vaporization flame holding plate 30 is heated by the heat of the exhaust gas circulation flow 34, so that the vaporization of the fuel 16 in the pre-combustion space 32 is further promoted. Therefore, even if the vaporization flame stabilizing plate 30 is provided, the vaporization of the fuel 16 sprayed from the nozzle 12 is not hindered by it, and rather the vaporization of the fuel 16 is promoted by the above-mentioned action, 16 burns better.

Further, the flame 18 spreads in a conical shape as described above, and as a result, its thickness becomes thin and becomes a so-called thin film flame. When a thin film flame is formed, heat exchange between the thin film flame and a combustion furnace such as a boiler is improved and the combustion temperature of the flame 18 is lowered, so that the NOx (nitrogen oxide) concentration in the exhaust gas is lowered. Moreover, by providing the vaporization flame stabilizing plate 30, the exhaust gas circulation flow 34 is generated as described above, whereby a part of the exhaust gas is recirculated into the flame 18 to become a so-called exhaust gas self-recirculation type, which Since the combustion temperature of the flame 18 drops, the NOx concentration in the exhaust gas also drops for this reason. With these two effects, in this burner,
In addition to shortening the flame, N in the exhaust gas compared to the conventional burner
The effect that the Ox concentration can be reduced can be obtained.

2 and 3 show examples of the measurement results of the visible flame length and the visible flame width in the burner of the conventional example shown in FIG. 14 and the burner of the embodiment shown in FIG. 1, respectively. The visible flame length is a measurement of the length of a portion where a flame is visually recognized. The same applies to the visible flame width, which in other words represents the thickness of the flame.

As can be seen from both figures, in the burner of the embodiment, the burner of the conventional example is more
The visible flame length is small and the visible flame width is large. That is,
In the burner of the example, a thick and short flame is obtained,
It can be seen that shortening of the flame has been realized. Further, it can be seen that the effect of shortening the flame becomes more remarkable as the combustion amount increases. In both figures, the values of visible flame length and visible flame width have upper and lower widths because the flame shape changes slightly when the air-fuel ratio during combustion is changed. This is because there are variations.

FIG. 4 is a sectional view showing another example of the liquid combustion burner according to the present invention. FIG. 5 is a front view of the liquid combustion burner of FIG.

In this embodiment, the air port 10 described above is replaced by
Instead of an annular shape, it is divided into a plurality (in the illustrated example, five) in the circumferential direction of the flame holding plate 26, and they are arranged substantially evenly in the circumferential direction of the flame holding plate 26. The portion 11 that is not the air port is closed by, for example, providing a baffle plate. This air port 1
The number of divisions of 0 is not limited to a specific one,
For example, 4 to 12, usually 6 to 8, but the combustion cylinder 2
The larger the inner diameter of, the larger the number of divisions.

When the air port 10 is divided as described above, the downstream side of the air port 10 is particularly in the air-rich region and no flame is formed, so that the flame 18 is divided radially as shown in FIG. 5, for example. It becomes a shaped flame, that is, a divided flame. As a result, the combustion temperature of the flame 18 can be further lowered as compared with the case of the embodiment of FIG.
The Ox concentration can be further reduced.

1 and 4, the distance A from the tip of the combustion cylinder 2 to the front surface of the flame holding plate 26 and the distance from the vaporizing flame holding plate 30 to the front surface of the flame holding plate 26 are the same. By adjusting the distance B, it is possible to adjust the shape of the flame 18 to match the combustion chamber of the boiler or the like. For example, the smaller the distance A is and the smaller the distance B is, the larger the flow of the fuel 16 in the outer peripheral direction is. Therefore, the flame 18 can be further widened to shorten the flame.

Further, the ratio A / C between the distance A, the distance B, the inner dimension C of the combustion cylinder 2 and the outer dimension D of the vaporizing flame stabilizing plate 30,
NOx in exhaust gas depending on the size of B / C and D / C
The concentration and combustion state change. The measurement results are shown in FIG.
As shown in FIG. These are the measurement results for the burner with the air port 10 shown in FIG. 4 divided, but also in the case of the burner without the air port 10 shown in FIG. 1, except that the NOx concentration is slightly higher, The result of the tendency similar to this is obtained.

As can be seen from FIG. 6, the ratio A / C is 0 to
Within the range of 0.4, the NOx concentration can be reduced to 80 ppm or less. By the way, the regulated value of NOx concentration in exhaust gas in major cities such as Tokyo, Osaka and Nagoya is 80 ppm in the case of liquid fuel. Ratio A / C
As the NOx concentration increases, the flame holding plate 26 is located deeper in the combustion cylinder 2 and the flame 18 increases.
It is thought that this is because the spread of the gas becomes smaller and the combustion temperature becomes higher.

As can be seen from FIG. 7, the ratio B / C is 0.0
If it is within the range of 5 to 0.35, the NOx concentration will be 80 pp
It can be suppressed to m or less and stable combustion can be maintained. If the ratio B / C is made smaller than 0.05, the pre-combustion space 32 becomes narrower, combustion instability at that space occurs, and the NOx concentration also rises. Ratio B / C is 0.35
If it is made larger than this, the effect of the vaporization flame holding plate 30 is reduced, and the combustion air 4 that wraps around the pre-combustion space 32 from the outer peripheral portion of the flame holding plate 26 is relatively increased, so that the pre-combustion space 32 is increased. Instability of combustion occurs at NOx concentration.

As can be seen from FIG. 8, the ratio D / C is 0.5.
Within the range of 1.0, the NOx concentration can be suppressed to 80 ppm or less, and stable combustion can be maintained. When the ratio D / C is smaller than 0.5, the vaporization flame holding plate 30 becomes relatively small and its effect is lowered, and the combustion coming from the outer peripheral portion of the flame holding plate 26 into the pre-combustion space 32 is performed. The amount of the working air 4 becomes relatively large, combustion instability occurs in the pre-combustion space 32, and the NOx concentration also rises. When the ratio D / C is made larger than 1.0, the combustion air 4 from the outer peripheral portion of the flame holding plate 26 comes into contact with the vaporizing flame holding plate 30, causing combustion instability in the precombustion space 32 and NOx. The concentration also increases.

The following can be said whether the air port 10 is divided or not.

That is, the shape of the vaporizing flame stabilizing plate 30 is not limited to the plate shape described above, and for example, the downstream side is concave dish-shaped as shown in FIG. 9 and the upstream side is concave as shown in FIG. It may be plate-shaped, or a conical shape having a concave downstream side as shown in FIG. 11. By doing so, the flow direction and the like of the fuel 16 sprayed from the nozzle 12 can be variously changed, so that the shape of the flame 18 and the combustion state thereof can be variously changed. Further, the material of the vaporization flame stabilizing plate 30 is not limited to a particular material, and may be, for example, metal or ceramics.

The vaporizing flame stabilizing plate 30 may be provided with a function of heating, for example, by adding an electric heater. When the vaporization flame holding plate 30 is heated by an electric heater or the like, the vaporization property of the fuel 16 is further increased at the time of ignition to facilitate ignition, and the combustibility after ignition is also improved.

The shape of the flame holding plate 26 is not limited to the above-mentioned mortar shape, but, for example, as shown in FIG.
It may have a bottomed cylindrical shape having an opening on the downstream side, more specifically, a bottomed cylindrical shape, and the point is that the vicinity of the central portion thereof should be a three-dimensional shape recessed to the upstream side. By doing so, the pre-combustion space 32 having a relatively large volume can be formed between the flame holding plate 26 and the vaporization flame holding plate 30. The action and effect thereof are as described above.

Combustion cylinder 2, flame holding plate 26 and vaporizing flame holding plate 3
The front shape of 0 is not limited to the circular shape in the above example, and may be another shape such as a polygon.

The position of the nozzle 12 is not limited to the vicinity of the upstream side of the flame holding plate 26 as in each of the above examples, but may be located near the downstream side of the flame holding plate 26 as shown in FIG. That is, it may be in the pre-combustion space 32. This is because it is sufficient that the fuel 16 can be sprayed from the nozzle 12 to the downstream side of the flame holding plate 26. In that case, the hole 28 at the center of the flame holding plate 26 may be closed by the fuel supply pipe 13 to the nozzle 12. In that case, if ventilation to the downstream surface side of the flame holding plate 26 is insufficient, a plurality of small holes or slits may be provided in the plate surface of the flame holding plate 26 as described above.

The number of nozzles 12 is not limited to one as in each of the above-mentioned examples, but may be two or more when increasing the combustion amount.

The method of spraying the fuel 16 from the nozzle 12 is
Various methods such as a hydraulic atomization method in which the fuel 16 is atomized only by hydraulic energy, a vapor atomization method in which the fuel 16 is atomized by steam, and an air atomization method in which the fuel 16 is atomized by air can be adopted.

[0036]

Since the present invention is configured as described above, it has the following effects.

According to the first aspect of the present invention, the fuel sprayed from the nozzle and hitting the vaporization flame stabilizing plate toward the outer peripheral direction and the combustion air flowing from the outlet of the combustion cylinder in the substantially axial direction thereof are combined to form the combustion cylinder. Since a conical flame that greatly spreads from the pre-combustion space toward the diagonally downstream side is formed near the outlet of the, the flame can be shortened.

Moreover, since the flame spreads as described above to become a thin film flame, and by providing the vaporization flame holding plate, an exhaust gas circulation flow is generated, and the combustion temperature of the flame is lowered by both of these actions, so that The NOx concentration can be reduced.

According to the second aspect of the present invention, the flame becomes a radially divided flame, which further lowers the combustion temperature of the flame, so that the NOx concentration in the exhaust gas can be further reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a liquid combustion burner according to the present invention.

FIG. 2 is a diagram showing an example of a measurement result of a visible flame length.

FIG. 3 is a diagram showing an example of a measurement result of a visible flame width.

FIG. 4 is a sectional view showing another example of the liquid combustion burner according to the present invention.

5 is a front view of the liquid combustion burner of FIG. 4. FIG.

FIG. 6 shows the NOx concentration (O _{2 in the} exhaust gas with respect to the ratio A / C.
It is a figure which shows an example of the measurement result of (= 0% conversion).

FIG. 7 shows the NOx concentration (O _{2 in the} exhaust gas with respect to the ratio B / C.
It is a figure which shows an example of the measurement result of (= 0% conversion).

FIG. 8 shows the NOx concentration (O _{2 in the} exhaust gas with respect to the ratio D / C.
It is a figure which shows an example of the measurement result of (= 0% conversion).

FIG. 9 is a diagram showing another example of the shape of the vaporizing flame stabilizing plate.

FIG. 10 is a diagram showing another example of the shape of the vaporizing flame stabilizing plate.

FIG. 11 is a diagram showing another example of the shape of the vaporizing flame stabilizing plate.

FIG. 12 is a diagram showing another example of the shape of the flame holding plate.

FIG. 13 is a diagram showing another example of nozzle positions.

FIG. 14 is a sectional view showing an example of a conventional liquid combustion burner.

[Explanation of symbols]

 2 Combustion Cylinder 4 Combustion Air 10 Air Port 12 Nozzle 16 Fuel 18 Flame 26 Flame Retaining Plate 30 Evaporative Flame Retaining Plate 32 Pre-combustion Space

Claims (2)

[Claims] 1. A combustion cylinder to which combustion air is supplied from the outside, a nozzle which is provided in the combustion cylinder and which is supplied with liquid fuel from the outside and injects it toward the tip of the combustion cylinder.
A flame holding plate provided near the nozzle in the combustion cylinder to stabilize the flame, and provided between the flame holding plate and the inner wall of the combustion cylinder or near the peripheral edge of the flame holding plate and supplied into the combustion cylinder. In a liquid combustion burner provided with an air port for ejecting the combustion air thus generated from the vicinity of the flame holding plate to the downstream side,
The flame holding plate has a three-dimensional shape in which the vicinity of its central portion is recessed on the upstream side, and a vaporizing flame holding plate is provided near the downstream side of this flame holding plate so as to face the flame holding plate, and between both flame holding plates. A liquid combustion burner characterized by forming a pre-combustion space. 2. The liquid combustion burner according to claim 1, wherein the air port is divided into a plurality of portions in the circumferential direction of the flame holding plate, and these are arranged substantially evenly in the circumferential direction of the flame holding plate.