JP3192802B2 - Combustor and operating method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustor having a premixed main nozzle and a diffusion combustion type pilot nozzle, and more particularly to a gas turbine combustor and a method of operating the same.

[0002]

2. Description of the Related Art A combustor according to the present invention will be described with reference to FIG. According to FIG. 7, a pilot nozzle 3 is provided at the center toward the combustion region of the inner cylinder 2 of the combustor 1, and a plurality of main nozzles 4 are provided around the pilot nozzle 3.

[0003] The pilot nozzle 3 has a plurality of fuel injection holes, the number and direction of which are arbitrarily set. At the outlet of the pilot nozzle 3, a protruding trumpet-shaped cone 5 is attached so as to enlarge the circulating flow region of the fuel injected from the pilot nozzle 3. As a result, stable combustion can be performed even in a state where the pilot fuel amount is small, and NO
x is reduced.

[0004] Reference numeral 6 denotes a fuel pipe to the main nozzle 4, and 7 denotes a fuel pipe provided to each main nozzle 4.
A main swirler 8 for providing a swirling flow in the same direction to the supplied air to premix air and fuel, and a pilot swirler 8 provided in a pilot nozzle.

[0005]

A combustor 1 having a premixed main nozzle 4 and a diffusion combustion type pilot nozzle 3
In order to stabilize the lean combustion of the premixed gas, there is a strong demand for lowering NOx. At the same time, it is possible to stabilize the combustion while reducing the diffusion flame, which generates an extremely large amount of NOx. It has become a challenge.

In the combustor 1, when the flame temperature locally decreases, carbon monoxide (CO) or unburned hydrocarbon (UH
There is a problem that C) is generated and discharged. In particular, at a partial load, a low-temperature portion is generated, and CO and UHC are generated.
Is more likely to occur.

The present invention has been made in view of the above circumstances, and it is possible to simultaneously reduce the NOx and the combustion stability by reducing the combustion gas, that is, the diffusion flame of the pilot nozzle. An object of the present invention is to provide a combustor that does not cause a temperature drop and a method of operating the combustor.

[0008]

According to the present invention, there is provided, in accordance with the present invention, a plurality of diffusion combustion type pilot nozzles in the center of a combustor of a gas turbine and a plurality of swirlers having the same swirling direction around the pilot nozzles. In a combustor having a premixed main nozzle, the number of fuel injection holes of the pilot nozzle is provided in a circumferential shape by the number of main nozzles, and each fuel injection hole is directed to the middle of two adjacent main nozzles. According to another aspect of the present invention, there is provided a method of operating a combustor, wherein a main nozzle is used every other when a partial load operation is performed on the combustor.

[0009]

According to the above-mentioned means, the diffusion flame from the pilot nozzle is efficiently supplied toward the middle where the mixing of fuel and air between two adjacent premixing main nozzles is promoted. Thus, the diffusion flame can be reduced more than before. In addition, at the time of partial load, even if every other main nozzle is used, the combustion gas from the pilot nozzle supplied between the two adjacent main nozzles burns with the premixed flame burning from the main nozzle. This avoids direct interference with the air supplied from the main nozzles which are not provided, so that the flame temperature does not decrease locally.

[0010]

FIG. 1 is an overall structural view of a combustor of a gas turbine,
FIG. 2 shows a cross section taken along the line AA. 1 is the same as that of FIG. 7 and, therefore, the same parts as those shown in FIG. 7 are denoted by the same reference numerals, and the details are omitted. 1 and 2, reference numeral 9 denotes a pilot flame holding region formed by a combustion gas (diffusion flame) from the pilot nozzle 3; 10 denotes a main combustion region formed by a premixed flame from the main nozzle 4; Combustion gas from the pilot nozzle 3, and fuel injection holes 12 are provided on the distal end surface of the pilot nozzle 3 by the same number as the number of the main nozzles 4 in a circumferential shape.

While the angle θ1 of the cone 5 for expanding the circulating flow in the pilot flame holding region 9 is set to 35 ° to 50 °, the fuel injection angle θ2 of the pilot nozzle 3 is approximately equal to 30 ° to 50 °. It is set to 45 °. The cone 5 expands the circulating flow and at the same time, turns the pre-mixed flow supplied from the main nozzle 4 while being swirled from the main nozzle 4 and the pre-mixed flow supplied from the main nozzle 4 adjacent thereto from the pilot nozzle 3. It also has a role to make the combustion gas 11 easily reach.

On the other hand, the positional relationship between the main nozzle 4 and the cone 5 is such that the tip of the cone 5 is at least positioned with respect to the gas hole position of the main nozzle 4 so that the fuel and air from the main nozzle 4 can be sufficiently mixed. It is designed to be at least 以上 the downstream diameter of the inner cylinder diameter D.

FIGS. 3 and 4 schematically show the operation of the combustor according to the present invention during combustion. FIG. 3 shows a case of full load, and FIG. 4 shows a partial load. Respectively.

According to FIG. 3, each premix main nozzle 4
Since the main swirlers 7 have the same swirling direction, the premixed gas 13 of the two adjacent main nozzles 4 has a swirling flow opposite to each other at an intermediate position between the premixed air and their collision. Therefore, between the adjacent main nozzles 4, the mixing of the fuel and the air is promoted.
The fuel injection holes 12 of the pilot nozzle 3 are set in this portion so as to supply the combustion gas 11 from the pilot nozzle 3. As described above, since the combustion gas 11 of the pilot nozzle 3 is supplied to the portion where the premixing is promoted, the combustion is stabilized, and therefore, stable combustion can be achieved even by supplying a small amount of pilot fuel. Become. Since the reduction of the pilot fuel reduces the diffusion flame, the generation of NOx can be suppressed.

According to experimental results, stable combustion is obtained with half the pilot fuel of the conventional pilot nozzle, and at the same time, the NOx value is reduced by 15%.

Referring to FIG. 4, every other main nozzle 4 is used at the time of partial load. That is, the burning main nozzles 4a (shaded) and the non-burning main nozzles 4b (shaded) are alternately positioned. Although the fuel is stopped, the main nozzle 4b that is not burning is supplied with air for cooling and other reasons. For this reason, the main nozzle 4 burning by this air
The premixed flame of a is interfered and tends to lower the flame temperature locally. However, since the combustion gas 11 from the pilot nozzle 3 reaches and burns between the burning premixed flame and the air from the main nozzle 4b that is not burning, the premixing flame from the main nozzle 4a The premixed gas can be burned without locally lowering the flame temperature of the flame, so that the generation of carbon monoxide CO and unburned hydrocarbon UHC is suppressed.

In order to make the above operation and effect more effective, the size (flame length) of the combustion gas 11 from the pilot nozzle 3 in the radial direction must be larger than the pitch circle diameter d of the main nozzle 4. It is desirable to have.

Although the combustor 1 is illustrated as a type having a cone 5, the present invention can provide the same effect even when there is no cone or when the number of main nozzles 4 is other than eight as shown. Needless to say.

FIGS. 5 and 6 show the effect of the combustor of the present invention in comparison with the case of the conventional combustor.
FIG. 6 is a graph of NOx, and FIG. 6 is a graph of UHC-NOx. In each of the graphs, the lower the data indicated by the solid line to the lower right, the lower the CO and the lower the UHC. However, both FIGS. 5 and 6 are on the left side of the data of the conventional example. This shows that lower CO, lower UHC and lower NOx are achieved. However, although the shape of the combustor is the same as that of the conventional example of FIG. 5 and FIG. 6, only the pilot nozzle has six fuel injection holes and the injection direction is arbitrary.

[0020]

According to the present invention, since the combustion gas of the pilot nozzle is supplied to the space between the main nozzle and the main nozzle adjacent thereto, combustion can be performed even if the combustion gas of the pilot nozzle is reduced. Stable and low NOx
Has become possible.

Further, in the combustion operation of every other main nozzle at the time of partial load, it is possible to prevent a local decrease in the flame temperature of the premixed flame, and to reduce and prevent the emission of CO and UHC.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a combustor according to the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a schematic diagram showing a combustion state of a combustor according to the present invention.

FIG. 4 is a schematic view showing another combustion state of the combustor according to the present invention.

FIG. 5 shows CO-NO showing the effect of the combustor according to the present invention.
It is a graph of x.

FIG. 6 is a UHC-N showing the effect of the combustor according to the present invention.
It is a graph of Ox.

FIG. 7 is a cross-sectional view showing an example of a conventional combustor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustor 2 Inner cylinder 3 Pilot nozzle 4 Main nozzle 9 Pilot flame holding area 10 Main combustion area 11 Combustion gas from pilot nozzle 12 Fuel injection hole 13 Premixed gas

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F23R 3/28 F23R 3/30

Claims (2)

(57) [Claims] 1. A combustor comprising a diffusion combustion type pilot nozzle in the center of a combustor of a gas turbine and a plurality of premixing type main nozzles each having a swirler in the same swirling direction around the pilot nozzle. A combustor characterized in that fuel injection holes are provided circumferentially in the number of main nozzles, and each of the fuel injection holes is directed to the middle between two adjacent main nozzles. 2. A method for operating a combustor according to claim 1, wherein when the combustor is operated under partial load, every other main nozzle is used.