JPH01139919A - Method and device for gas turbine combustion - Google Patents

Abstract

PURPOSE:To maintain the differential pressure of fuels at an optimum level to perform a stable combustion by supplying either part of main fuel or fluid other than fuel such as air, nitrogen, steam, etc., to at least either one of pilot fuel and main fuel in proportion to the amount of fuel. CONSTITUTION:An auxiliary line 10 is provided as a branch of a main fuel pipe 4, and, at the end of the auxiliary line, an auxiliary nozzle 10 is provided as a pilot fuel nozzle. Under the condition where a gas turbine is operated below 1/4 load at a low fuel/air ratio, the fuel is supplied only from the pilot fuel nozzle 1 for diffuse flame. When the gas turbine load is greater than 1/4, 5-10% of all fuel is supplied from the pilot fuel nozzle 1 and 95-90% from the main fuel nozzle 2. In such a case, a fluid such as air, nitrogen or steam, etc., is added through the auxiliary line 12 to the pilot fuel flowing in the pilot fuel pipe 3 so that the calorific value supplied by the fuel system may be maintained at a constant level while the flow rate alone is increased, i.e. the differential pressure may be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a gas turbine combustion method and a combustion apparatus thereof. However, the present invention is applicable not only to gas turbines but also to combustion devices in general such as jet engines and boilers.

2. Description of the Related Art There is a conventional gas turbine combustion apparatus, for example, as shown in FIG. It is connected to a supply source (not shown) via a pilot fuel pipe 3 and a main fuel pipe 4, and a control valve 5 is provided in the middle of each of these fuel pipes.
．． 6 is provided.

In order to reduce NOx in the gas turbine, a premixture of fuel and air is formed in the diffusion flame pilot combustor 7 and the premix nozzle 8, and this premixture is supplied to the main combustor 9I. , is burning.

Therefore, the diffusion flame pilot burns at about 1/4 the load of a gas turbine with low vacuum pressure, and at higher loads, for example, burns about 30% of the total fuel amount, making it the main source of the premixed flame. However, it has the disadvantage of high NOx generation. On the other hand, the main premixed flame cannot achieve stable low NOx unless it is burned at a nearly constant void ratio.
Combustion is performed at approximately 1/4 load or more of the gas turbine, and an air bypass mechanism (not shown) is used to adjust the amount of air flowing into the combustor as shown in Figure 6, thereby increasing the void ratio of the combustor. are being adjusted. With this method, NOx can be reduced by 100%.
It is set to be less than pp■, which is less than 1/3 compared to the NOx of the conventional diffusion combustion method.

In the above description, gas turbine load means load ratio, where 4/4 represents rated load and 0/4 represents no load.

Problems to be Solved by the Invention In the conventional premixing system, the amount of pilot fuel is relatively large, about 30% of the total amount of fuel, and there is a limit to reducing NOx.

Therefore, if the proportion of the pilot fuel in the total fuel amount is lowered, for example, to about 5%, and the proportion of the premixed fuel is increased, it becomes possible to reduce NOx.

However, when the load on the gas turbine is low, it is necessary to burn 100% of the pilot fuel, so it is necessary to supply a range of 5 to 1 (1%) as the amount of pilot fuel. As shown in Figure 7, the fuel differential pressure at the time is 0.25% to 100%, and the differential pressure range is significantly expanded.When the differential pressure is small, the fuel flow rate increases due to a small change in the combustor internal pressure. significantly decreased,
Alternatively, since fuel is no longer supplied, there is a problem that misfires occur or stable combustion cannot be achieved.

Further, such unstable combustion problems occur not only in connection with pilot fuel but also in connection with main fuel.

In other words, essentially, pilot fuel has a large flow rate change of 5 to 100%, while main fuel has a large flow rate change of 25 to 10%.
0% and the flow rate change is smaller than that of the pilot fuel, so there is some margin, but due to the design of the main fuel nozzle and the constraints on the maximum pressure that can be supplied with the main fuel, unstable combustion similar to that with the pilot fuel occurs, and this is due to the experimental results. , confirmed on both actual machines.

In the above explanation, the reason why the ratio of the pilot fuel amount to the total fuel amount (pilot fuel ratio) is set to about 5% is as follows. That is, as shown in FIG. 9, the pilot fuel ratio and N0II are in a proportional relationship,
A pilot fuel ratio of 0% is preferable in terms of NOx reduction, but this will cause misfires, and a pilot fuel ratio of 5% to 5% in summer will not make much of a difference in NOx reduction. This is because, taking into account that a higher pilot fuel ratio is preferable, a pilot fuel ratio of around 5% is judged to be optimal.

Regarding Figure 7, the pilot fuel nozzle differential pressure ratio is fuel differential pressure/maximum fuel differential pressure at each load (1 in Figure 7).
/4 load, pilot fuel ratio 100%),
The fuel differential pressure is expressed as (pilot fuel nozzle population pressure) - (pilot fuel nozzle outlet pressure; combustor internal pressure). Since the fuel differential pressure is proportional to the square of the flow rate, the pilot fuel differential pressure is (0,05/l) from the flow rate ratio of 0.05/l.
l)”=0.0025/1.

Means for Solving the Problems In order to solve these conventional problems, the present invention provides the following:
In the gas turbine combustion method, a part of the main fuel is supplied as at least one of the pilot fuel and the main fuel flowing through different systems depending on the amount of fuel, or a fluid other than the fuel such as air, nitrogen, or steam is supplied as the fuel. The fuel is supplied to at least one of the pilot fuel and the main fuel depending on the amount to maintain the fuel differential pressure at an optimum value and to achieve stable combustion.

The present invention also provides a gas turbine combustion system comprising a pilot fuel nozzle and a main fuel nozzle and a pilot fuel pipe and a main fuel pipe respectively connecting each of these nozzles to a fuel supply source for carrying out such a combustion method. In the fuel tank, a part of the main fuel is supplied from an auxiliary nozzle as at least one of pilot fuel and main fuel through an auxiliary line, or a fluid other than fuel such as air, nitrogen, or water vapor is supplied through the pilot fuel pipe and the main fuel pipe. An auxiliary line is attached to supply at least one of the two.

Effect: According to such a means, the fuel pressure difference can be maintained at a constant value or higher regardless of the gas turbine load and the amount of pilot or main fuel, and stable combustion can be achieved.

Examples below! a,! Four embodiments of the invention will now be described in detail with reference to Figures b, 2.3 and 4. In these figures, the same parts as shown in FIG. 5 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 1a shows a first embodiment of the invention, in which the main fuel pipe 4
An auxiliary line 10 is branched from the auxiliary line 10, and an auxiliary nozzle 11 as a pilot fuel nozzle is attached to the tip of this auxiliary line.
It has been established. And these auxiliary nozzles 11
are preferably of a smaller nozzle diameter than the existing pilot fuel nozzle l, as shown in FIG. 1b, and these nozzles! and 11 are arranged alternately and at equal intervals on the same circumference.

Therefore, when the gas turbine has a low fuel/air ratio and is under about 174 load, all the fuel is supplied from the diffusion flame pilot fuel nozzle 1 and combusted. At higher gas turbine loads, the auxiliary nozzle 11 supplies 5 to 10% of the total fuel amount, and the main fuel nozzle 2 supplies 95 to 90% of the total fuel amount.

In this way, it is possible to provide a plurality of pilot fuel systems and use the fuel systems differently depending on the amount of pilot fuel to be supplied, thereby ensuring a pilot fuel supply differential pressure of at least 0.5% of the maximum supply pressure. .

FIG. 2 shows a second embodiment of the present invention, in which an auxiliary line 12 is attached in the middle of the pilot fuel pipe 5, and fluid other than fuel such as air, nitrogen, steam, etc. can be supplied through this auxiliary line. A control valve 13 is provided in the middle of the auxiliary line 12.

Therefore, when the gas turbine has a low fuel-air ratio and the load is less than about 174, all the fuel is supplied from the diffusion flame pilot fuel nozzle 1 and combusted. At higher gas turbine loads, 5 to 10% of the total fuel amount is supplied from the pilot fuel nozzle l.
Also, 95 to 90% of the fuel is supplied from the main fuel nozzle 2, but at this time, a fluid other than the fuel such as air, nitrogen or water vapor is added to the pilot fuel flowing in the pilot fuel pipe 3 through the auxiliary line 12, This makes it possible to keep the amount of heat supplied from the fuel system constant and increase only the flow rate, that is, increase the differential pressure.

In this way, it is possible to add fluids other than fuel such as air, nitrogen, and water vapor to the pilot fuel system, and when the amount of fuel to be supplied decreases, the fluid other than fuel is added or increased to increase the pilot fuel and fluid supply pressure other than fuel. can be ensured to be at least 0.5% of the maximum supply pressure.

According to the first and second embodiments described above, it is therefore possible to maintain the differential pressure ratio of the pilot fuel nozzle above the minimum level necessary for stable combustion, as shown in FIG.

FIG. 3 shows a third embodiment of the present invention, in which an auxiliary line 14 is branched from the main fuel pipe 4, and an auxiliary arm shield 15 as a main fuel nozzle is provided at the tip of this line. It is something. That is, a plurality of main fuel systems are provided, and the fuel systems are selectively used depending on the amount of main fuel to be supplied, so that the main fuel supply differential pressure is at least 105 times higher than the maximum supply pressure.

Note that a control valve 16 is provided in the middle of the auxiliary line 14.

FIG. 4 shows a fourth embodiment of the present invention, in which an auxiliary line 17 is provided in the middle of the main fuel pipe 4, through which fluids other than fuel such as air, nitrogen, and water vapor can be added to the main fuel. 1. In order to ensure that fluid other than fuel is at least 10% of the supplementation pressure when the amount of fuel to be supplied decreases. -It's something new.

Note that a control valve 18 is provided in the middle of the auxiliary line 17.

In each of the embodiments described above, in order to maintain the fuel differential pressure at a certain constant value, the pressure and flow rate of each fuel line are measured with a pressure converter, differential pressure converter, etc., and the pressure and flow rate are set in advance. Of course, a method may be adopted in which the flow rate of the scheduled flow rate is checked and fed back, thereby controlling the flow rate to a predetermined flow rate.

Effects of the Invention As detailed above, according to the present invention, combustion can be performed while maintaining the fuel differential pressure at an optimum value regardless of the gas turbine load and the amount of pilot or main fuel, thereby achieving stable combustion. and can significantly reduce NOx.

For example, an example of the effect of the present invention in the case of pilot fuel is shown in FIGS. 7 and 8 in comparison with the conventional example. The differential pressure can be maintained above a certain value,
Stable combustion becomes possible.

In addition, the pilot fuel ratio of the diffusion flame, which generates a large amount of NOx, can be set to 5%, and the main fuel ratio of the premixed flame, which generates a small amount of NOx, can be set to 95%, so NO! Concentrations can be as low as 50 ppm or less.

[Brief explanation of the drawing]

FIG. 1a is a schematic diagram showing one embodiment of the present invention, FIG. 1b is a diagram showing an example of arrangement of two types of pilot fuel nozzles in the gas turbine combustion device, FIGS. 2, 3, and 4.
The figure is a schematic diagram showing three other different embodiments of the present invention, Figure 5 is a schematic diagram showing a conventional example, and Figure 6 is a diagram showing the relationship between the gas turbine load, the combustor inflow air amount ratio, and the void ratio. figure,
FIGS. 7 and 8 are diagrams showing changes in the differential pressure ratio and NOx ratio of the pilot fuel nozzle, shown to explain the effects of the present invention in comparison with conventional examples, and FIG. 9 is a diagram showing changes in the pilot fuel ratio and NOx ratio. FIG. l... Pilot fuel nozzle, 2... Main fuel nozzle, 3... Pilot fuel pipe, 4... Main fuel pipe, 7...
・Pilot combustor, 8...Premix nozzle, 9...Main combustor, 10.12.14.17 (and 11 other figures 1α, 1b, 2, 3, 4) Sennosu 7th Hatarot 4° Metsuhiki No. 51! 1st Figure λ Tarbin - Loading Force Starbin ◆ Ma

Claims (1)

[Claims] 1. A part of the main fuel is supplied as at least one of the pilot fuel and the main fuel flowing through different systems depending on the amount of fuel, or a fluid other than fuel such as air, nitrogen, or water vapor is supplied. A gas turbine combustion method characterized by supplying at least one of pilot fuel and main fuel according to the amount of fuel to maintain fuel differential pressure at an optimal value and achieve stable combustion. 2. In a gas turbine combustor equipped with a pilot fuel nozzle, a main fuel nozzle, and a pilot fuel pipe and a main fuel pipe that connect each of these nozzles to a fuel supply source, a portion of the main fuel is transferred from the auxiliary nozzle to the pilot fuel and the main fuel nozzle. An auxiliary line for supplying at least one of fuel or a fluid other than fuel such as air, nitrogen, or steam to at least one of the pilot fuel pipe and the main fuel pipe is attached. Gas turbine combustion equipment.