JPH06185732A - Burner - Google Patents

Abstract

PURPOSE:To obtain a burner which has excellent fire transfer characteristics at the time of ignition and can burn stable lean premixed gas by providing a flame stabilizer having a bypass passage at an outlet of a premixer, and controlling a direction of a jet flow generated by a jet flow generator. CONSTITUTION:When a control stream flows from a channel 5 into a premixer, a pressure difference is generated above and below a jet flow, the jet flow is bent upward, the jet flow does not arrive at a bypass channel inlet 7, and since mixed gas does not flow in a bypass channel 8, a large circulation flow is formed at a rear of a flame stabilizer 6. When the stream does not flow from the channel 5, the jet flow flows straightly to a rear of the stabilizer 6 from the inlet 7 to the channel 8. In this case, the flow at the rear of the stabilizer 6 flows similarly to a bluff-body type flame stabilizer to form a circulation flow. Accordingly, the flow of the rear of the stabilizer can be controlled only according to presence/absence of the control flow from the channel 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas turbine combustor, and more particularly to a structure of a gas turbine combustor for reducing nitrogen oxides (hereinafter abbreviated as NOx) by adopting a premixed combustion system. .

[0002]

2. Description of the Related Art Conventionally, a gas turbine combustor has adopted a diffusion combustion system in which air and fuel are separately ejected and mixed and burned. In the diffusion combustion method, a high temperature part around 2000 ° C. locally occurs in a region where the fuel concentration is close to the equivalence ratio. Due to the existence of this high temperature region, diffusion combustion is excellent in flame stability. However, the production amount of nitrogen oxides (NOx) rapidly increases from about 1500 ° C., and therefore the NOx emission amount becomes extremely large when the diffusion combustion method is used. Conventionally, a means for injecting water or water vapor into a flame to lower the flame temperature in a high temperature region has been used to reduce NOx, but there is a problem that efficiency decreases because the average temperature of the whole is lowered. It was Therefore, in recent years, the diffusion combustion system is changing to a premixed combustion system using diffusion combustion as a pilot burner. An example thereof is shown in FIG. The premixed combustion method burns a premixed air mixture in which air and fuel are premixed. If the fuel is lean and premixed sufficiently, no local high temperature region will occur, so that NOx can be significantly reduced only by that combustion method. Further, since the combustion reaction region is small and the flame is short, it is suitable for high load combustion, and high efficiency can be achieved. On the other hand, on the other hand, contrary to diffusion combustion, because of the absence of a high-temperature region, the flame tends to be unstable, and the flame is easily blown off and a backfire is likely to occur. Therefore, various flame stabilizers are installed at the outlet of the premixer to stabilize the premixed combustion.

The flame stabilizer has a structure called a recess in which a structure having an inward inclination angle with respect to the flow of the air-fuel mixture is installed on the wall side of the combustion chamber, and a center of the premixer passage. There are two main types of flame stabilizers called Bluff Body, which have a structure with a triangular cross section. A conventional example using a recess is, for example, Japanese Patent Application No. 2-217015, and a conventional example using a bluff body is, for example, Japanese Patent Application No. 2-22066.
There is a 7th specification. Comparing the two, in the case of the recess, the flame transfer characteristics from the diffusion combustor at the time of ignition are good, but the flame stability at the time of lean combustion is inferior, and cooling is required to prevent damage to the recess. On the other hand, the bluff body has good flame stability at the time of lean combustion, but has a drawback that it has poor fire transfer characteristics and is difficult to ignite. Therefore, it is easy to ignite,
A flame stabilizer with good flame stability is required.

[0004]

As described above, in the prior art related to the combustor, stable and reliable transfer of the fire from the diffusion combustor to the premixer and the stable combustion of the lean premixed gas are simultaneously achieved. It was difficult to do.

An object of the present invention is to provide a combustor which is excellent in transfer characteristics during ignition and which enables stable lean premixed gas combustion.

[0006]

According to the present invention, the inside of the premixer is divided into two channels by a partition, and a jet generator is provided in the channel on the wall side of the outer shell of the separated channels. The above object is achieved by providing a flame stabilizer having an inward inclination angle at the mixer outlet and having a bypass flow path in a part thereof.

[0007]

[Function] A bypass flow path is provided in a part of the recess type flame stabilizer,
By controlling the inflow of the premixed gas to the bypass flow passage, the flow becomes the same as that of the recess type flame stabilizer when the premixed air does not flow into the bypass flow passage, and when the premixed air flows into the bypass flow passage. The flow path of the premixer may be formed so that the flow becomes similar to that of the bluff body flame stabilizer. In addition, the pressure and temperature of the combustion chamber are high, and if the structure has an operating part, there is a high risk of damage and it cannot be used in an actual machine.
A passive control structure with no moving parts is required. Therefore, the hydrodynamic characteristics of the jet generated by the jet generator provided in the premixer are used. When there is a flow from the direction perpendicular to the jet, the jet changes its blowing direction due to the pressure difference. Further, when there is a wall near the jet, if the flow velocity of the jet is high, the jet adheres to the wall due to the Coanda effect and flows. Therefore, it is possible to control the inflow of the air-fuel mixture from the premixer to the bypass flow passage by installing a control flow in a direction perpendicular to the jet flow or controlling the jet flow velocity and the distance between the jet outlet and the wall. It is possible to achieve a combustor having the characteristics of the recess flame stabilizer and the bluff body flame stabilizer described above.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a combustor for carrying out the present invention. In the combustor of this embodiment, the inside of the premixer is divided into two flow paths by the partition plate 2, and the jet generator 3 is provided in the flow path of the separated outer shell. The air-fuel mixture flowing through the flow path of the outer shell passes through the jet flow generating device 3 and flows out as a jet flow from the outlet 4. A control flow passage 5 for controlling the direction of the jet flow is installed downstream of the outlet 4, and a recess-type flame stabilizer 6 having a bypass flow passage 8 is provided in a part of the downstream. Depending on the presence or absence of the control flow from the flow path 5, the flow direction of the jet flow is changed, and the flow into the bypass flow path 8 is controlled. FIG. 2 shows changes in the flow of the air-fuel mixture with and without the control flow. When the control flow flows into the premixer from the flow path 5, a pressure difference is generated above and below the jet flow, and the jet flow is bent upward. Since the bent jet flow does not reach the bypass flow passage inlet 7 and the air-fuel mixture does not flow in the bypass flow passage 8, a large circulation flow is formed at the rear part of the flame stabilizer 6 as in the conventional recess. When the control flow does not flow from the flow path 5, the jet flow goes straight, flows from the bypass flow path inlet 7 through the bypass flow path 8, and flows out to the rear part of the flame stabilizer 6. In this case, the flow of the rear part of the flame stabilizer 6 is the same as that of the bluff body type flame stabilizer, and forms a circulation flow as shown in FIG. 2 (b). Therefore, the flow in the rear part of the flame stabilizer can be controlled only by the presence / absence of the control flow from the flow path 5, and the control flow is introduced at the time of ignition to improve the fire transfer characteristic from the diffusion combustor and to perform the rated operation. At times, it is possible to control the operation of the combustor to stop the flow of the control flow and improve the stability of the flame.

FIG. 3 shows another embodiment of the present invention. In this embodiment, the flow passage 5 of the control flow is not installed, but the flow velocity of the air-fuel mixture is changed, and the adhering of the air-fuel mixture into the bypass flow passage 8 is utilized by utilizing the adhesion of the jet flow to the wall surface 9 by the Coanda effect. Control. As the speed of the jet increases, the Coanda effect becomes stronger and the jet becomes more likely to adhere to the wall surface. On the other hand, when shifting from ignition to rated operation, the flow velocity of the air-fuel mixture is increased. Therefore, there is a difference between the flow rate of the air-fuel mixture at the time of ignition and the flow rate at the time of rated operation, and the wall surface 9 and the jet outlet 4 are set so that the flow rate at which the wall surface starts to adhere is between these flow rates.
If the distance between and is set, the inflow of the air-fuel mixture into the bypass passage 8 is controlled. FIG. 4 shows switching of the flow depending on the flow velocity of the air-fuel mixture. At the time of ignition with a slow air-fuel mixture velocity, the jet flow ejected from the jet flow outlet 4 does not adhere to the wall surface, and the bypass flow passage inlet 7
Since the jet flow does not reach, a large circulating flow is formed at the rear part of the flame stabilizer 6 as in the conventional recess. During the rated operation in which the air-fuel mixture flow rate is high, the jet flow adheres to the wall surface and flows out from the bypass passage inlet 7 through the bypass passage 8 to the rear part of the flame stabilizer 6. In this case, the flow at the rear of the flame stabilizer 6 is similar to that of the bluff body flame stabilizer. Therefore, by changing the air-fuel mixture flow rate, the flow behind the flame stabilizer can be controlled,
It is possible to improve the characteristics of transfer of heat from the diffusion combustor during ignition, and flame stability during rated operation.

[0011]

According to the present invention, it is possible to provide a combustor which has a good flame transfer characteristic at the time of ignition and a good flame stability at the time of rated operation with one flame stabilizer. Furthermore, the structure has no moving parts and is a passive structure that only controls the fluid, and has excellent reliability against damage and failure in the high-pressure, high-temperature combustor.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing the operation of the first embodiment.

FIG. 3 is a sectional view showing a second embodiment of the present invention.

FIG. 4 is a sectional view showing the operation of the second embodiment.

FIG. 5 is a sectional view of the overall structure of a diffusion-premix combustor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Partition plate, 2 ... Premixer partition plate, 3 ... Jet generating part, 4 ... Jet outlet, 5 ... Flow path, 6 ... Flame stabilizer, 7 ... Bypass flow path inlet, 8 ... Bypass flow path, 9 …wall.

Claims (1)

[Claims] 1. A combustor having a premixer for mixing air and fuel to produce a premixed gas, and burning the premixed gas at an outlet of the premixer, wherein a flow path is provided inside the premixer. A partition plate to be separated, a jet flow generator provided in the outer flow passage divided by the partition plate, and a flame stabilizer having a bypass flow passage at the outlet of the premixer are provided, and the jet flow generator is generated. A combustor, wherein the flow of the premixer into the bypass passage in the flame stabilizer is controlled by controlling the direction of the jet flow.