JPH06213448A - Swirling strength regulator for burner - Google Patents

Abstract

PURPOSE:To easily regulate a size of a recirculating area to be flame-stabilized in a burning zone to a suitable value by regulating a swirling strength at the time of premixing. CONSTITUTION:A tube 13 for blowing the air from a main pressure part 3 of the air to a swirling center 11 of a swirling area 5 is provided, and a valve 12 for regulating a flow rate of the air to be blown to the center 11 is provided at the tube 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a swirl intensity adjusting device capable of reducing NOx generated by adjusting the size of a mixture of fuel and air by a swirl (swirl flow) in a gas turbine combustor. It can also be applied to equipment for mixing and mixing gas and powder.

[0002]

2. Description of the Related Art In a gas turbine combustor, in order to reduce NOx in the exhaust gas of a combustor, a method has recently been adopted in which fuel and air are premixed and the premixed mixture is subjected to lean combustion. FIG. 5 shows an example of a conventional combustor using a tangential swirl flow in the premixing section, and FIG. 6 is a cross section taken along line AA.

In FIGS. 5 and 6, reference numeral 1 is a gas fuel supply pipe for main fuel, 2 is a gas combustion nozzle, 3 is a source pressure portion to which compressed air for combustion is supplied, and 4 is a premixed gas swirl. Vane 5 is for the swirl region of the premixer of the combustor, 6
Is a pilot flame gas fuel supply pipe, 7 is a pilot flame air flow passage outer cylinder that forms an air flow passage for pilot flame and functions as a support of the combustor premixing portion, 8 is a combustor outer cylinder, and 9 is a cone Reference numeral 10 indicates a combustion zone.

The pilot fuel injected from the pilot flame gas fuel supply pipe 6 installed in the central portion forms a pilot flame in the combustion zone 10 for maintaining the flame during the initial ignition of the combustor and the subsequent operation. To do. The main fuel injected from the gas fuel nozzle 2 enters the swirl region 5 by the air blown from the source pressure portion 3, and at this time, the swirl is generated by the vane 4 having the vane angle arbitrarily set in the tangential direction and the radial direction. A swirl of premixed gas is formed in the region 5 and then discharged to the downstream side, and the combustion zone 1
It burns lean at 0.

The pilot flame is useful for holding the flame species and for stable combustion of the premixed gas. However, the pilot flame is generally used only in the initial stage and is extinguished after the main fuel is ignited in order to reduce NOx generated from the pilot flame. Therefore, instead of the pilot flame, a flame holding mechanism that holds the type of flame is required.

As a flame holding mechanism, as shown in FIG.
By swirling the premixed gas strongly and supplying it to the combustion zone 10, a swirl system is formed in which a gas recirculation region in which a reverse flow is generated is formed in the center and the flame is held in this recirculation region. Alternatively, as shown in FIG. 8, there is a baffle plate system in which a baffle plate is placed in the flow of the premixed gas and the flame is held in the recirculation region formed on the downstream side of the premixed gas. The swirl system that uses the swirl in the premixing section will be used.

Generally, the fire-holding strength when the combustor flame is held by the swirl is defined by the swirl number S in the following equation. That is, S = (axial momentum component) / (axial momentum) ×
(Radius of Passage) FIG. 9 shows a change in the size of the circulation flow due to the swirl. According to this figure, the gas recirculation region increases as the swirl number S increases, and flame holding is enhanced. ing.

[0008]

By the way, the proper size of the gas recirculation region for holding the flame by the swirl of the combustor flame differs depending on the combustor. It is difficult to change the size of the area. In other words, the size of the recirculation region can be changed only by changing the total air amount or, if the total air amount is not changed, by changing the shape of the air inflow part and changing the swirl number. It took a great deal of time to seek flame holding ability.

The present invention has been made in view of the above circumstances, and provides a swirl strength adjusting device capable of changing the size of a recirculation region having a flame holding function without changing the total air amount or the device shape. The purpose is to provide.

[0010]

To solve the above problems, according to the present invention, the swirl of the premixed gas is generated by the air flowing in together with the fuel from the vicinity of the combustor premixing part from the source pressure part, and the swirl is used for combustion. A gas turbine combustor configured to generate a recirculation region for holding a flame species in a zone, a device for adjusting the swirl strength of a premixed gas generated in a swirl region of a combustor premixing section, There is provided a combustor swirl intensity adjusting device including a pipe for supplying air from a pressure portion to a central portion of a swirl, and a valve provided in the pipe for adjusting an air flow rate.

[0011]

According to the above-mentioned means, the pressure in the center of the swirl is lowered by the centrifugal force due to the swirling of the premixed gas in the swirl region of the premixer of the combustor, and the pressure is supplied to this swirl center by piping The pressure drop at the center of the swirl is alleviated by inflowing the generated air, and the strength of the swirl in the swirl region is adjusted. The strength of this swirl can be adjusted by controlling the flow rate of the valve installed in the pipe.

[0012]

1 shows the basic structure of a combustor swirl strength adjusting device according to the present invention. In the figure, the same parts as those shown in FIG. Is omitted.

According to FIG. 1, from the air source pressure portion 3 toward the swirl center portion 11 of the swirl region 5, a pipe provided with a valve 12 for adjusting the air flow rate is attached, and the air pressure of the air source portion 3 is increased. A part is supplied to the swirl center 11.

In the swirl region 5, the pressure in the central portion of the swirl (core region) 11 is extremely lowered by the centrifugal force generated by the swirling of air. Here, when the air flows from the air source pressure portion 3 toward the swirl central portion 11 through the pipe 13, the pressure drop in the swirl central portion 11 is alleviated. Since the flow rate of the air flowing from the source pressure portion 3 into the swirl region 3 is determined by the pressure difference between the source pressure portion 3 and the swirl center portion 11, the inflow of air from the pipe 13 causes the swirl center portion 1 to flow.
When the pressure of 1 increases, the amount of air flowing from the source pressure portion 3 decreases, and the swirl strength of the swirl region 5 decreases. This swirl strength reduction is adjusted by piping 13
It is possible by adjusting the flow rate of Therefore, the swirl number S can be changed without changing the total air amount by adjusting the valve 12, and the size of the recirculation region of the combustion zone 10 can be changed.

2 and 3 show an example in which the swirl intensity adjusting device according to the present invention is applied to a gas turbine combustor. According to this embodiment, in order to supply the air of the source pressure portion 3 to the central portion of the swirl, the pipe 13 provided with the valve 12 is connected to the air tank 14, and this air tank 14
Through a pipe 15 and inside the air passage outer cylinder 7 for pilot flame, and the air ejection nozzle hole 1 is formed on the outer peripheral surface.
6 are connected to the air inflow portion 17 having a large number of holes.
The number of the pipes 13 is preferably equal to or greater than the number of vanes 4 in order to make the air flow into the swirl region 5 uniform.

The air of the source pressure portion 3 supplied through the pipe 13 is first stored in the air tank 14, and after entering the air inflow portion 17 through the pipe 15, the swirl from the air ejection nozzle hole 16 thereof. It is jetted to the central portion 11 to increase the pressure in the swirl central portion 11. As a result, the swirl strength of the swirl region 5 is reduced, and the size of the gas recirculation region in the combustion zone 10 can be reduced accordingly.

In general, the behavior of swirling flow is often explained by Rankine's combined vortex theory. V _θ r around the swirling flow
= Constant (V _θ : turning speed, r = radius) is a free vortex region, and the central part is a forced vortex region represented by V _θ = rω (ω: angular velocity). The pressure distribution is shown in FIG. When the boundary between the forced vortex and a free vortex to occur at a distance of r = a, static pressure p swirling flow center is represented by ^{_{p = p 0 -pω 2 a 2}} (1-r 2 / 2a 2), The static pressure at the point of r = a is 1/2 of (p ₀ −p) in the above equation (p ₀ : static pressure at infinity. In this case, static pressure of air source pressure part 3). .

Now, as shown in the example of FIG. 2, when air is supplied to the swirl central part 11 from the air inflow part 17 in the central part, the region of the forced vortex generated by the swirl disappears in extreme terms. Will end up. In this case, as described above, the static pressure difference between the air source pressure portion 3 and the swirl center portion 11 becomes the first half, and the inflow is caused by the static pressure difference between the air source pressure portion 3 and the swirl center portion 11. The amount of air used was simply 1 /
√2.

By changing the magnitude of the fluid resistance of the pipe 13, the amount of air flowing in through the pipe 13 can be adjusted. That is, the valve 12 attached to the pipe 13
Thus, the amount of air in the pipe 13 can be easily adjusted, and thus the swirl number, which is an index of the turning strength, can be controlled.

[0020]

According to the present invention, in a gas turbine combustor utilizing a swirl for premixing fuel and air, and for flame holding for holding a spark during operation, swirl during premixing By adjusting the strength, it is possible to change the size of the recirculation region having the flame holding function without changing the total air volume or changing the shape of the device, so it is easy to obtain the appropriate flame holding ability. It becomes possible.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing the basic principle of a combustor swirl strength adjusting device according to the present invention.

FIG. 2 is a diagram showing an example in which the combustor swirl intensity adjusting device according to the present invention is applied to a premixing section of a gas turbine combustor using a tangential swirl flow.

FIG. 3 is a sectional view taken along the line BB of FIG.

FIG. 4 is an explanatory diagram showing a flow velocity distribution / static pressure distribution of a swirling flow.

FIG. 5 is a cross-sectional view showing an example of a conventional gas turbine combustor using a tangential swirl flow.

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

FIG. 7 is an explanatory diagram showing an example of a flame holding mechanism for a combustor flame.

FIG. 8 is an explanatory diagram showing another example of a flame holding mechanism for a combustor flame.

FIG. 9 is an explanatory diagram showing a change in size of a circulating flow due to a swirling flow.

[Explanation of symbols]

 1 Gas Fuel Supply Pipe 2 Gas Fuel Nozzle 3 Main Pressure Section 4 Vane 5 Swirl Area 6 Gas Fuel Supply Pipe 7 Air Flow Outer Tube 8 Combustor Outer Tube 9 Cone 10 Combustion Zone 11 Swirl Center 12 Valve 13 Pipe 14 Air Tank 15 Piping 16 Air jet nozzle hole 17 Air inflow part

Claims (1)

[Claims] Claim: What is claimed is: 1. A swirl of a premixed gas is generated by the air flowing in together with fuel from the source pressure part around the combustor premixing part, and this swirl is used to generate a recirculation region for holding a flame seed in the combustion zone. In the gas turbine combustor, the device for adjusting the strength of the swirl of the premixed gas generated in the swirl region of the combustor premixing section, a pipe for supplying air from the source pressure section toward the center of the swirl. A combustor swirl intensity adjusting device comprising: a valve provided in the pipe for adjusting an air flow rate.