1. Field of the Invention
The present invention relates to a combustor containing a fuel nozzle to supply fuel. Particularly, it relates to a gas turbine combustor.
2. Description of the Related Art
The path of air for combustion that enters the combustor 100 through an air inlet 110 thereof is changed by about 180° at an inner tube end portion 120 to allow the air to flow into an air passage 140. A part of air for combustion is mixed with fuel injected from injection ports 260 of the hollow column 250 and, then, flows into the swirler 290 of the fuel nozzle 200. Accordingly, the air for combustion is rotated mainly in a peripheral direction and mixture of the air for combustion and the fuel is promoted. Thus, pre-mixed air is produced in the mixing chamber 150.
The remaining of air for combustion flows into the swirler 390 disposed between the pilot nozzle 300 and the pre-mixing nozzle 170. The air for combustion is burnt with fuel injected from the pilot nozzle 300, in the pilot combustion chamber 160, to produce a pilot flame. Pre-mixed air mixed with fuel injected from the injection ports 260 of the hollow column 250 is brought into contact with the pilot flame and then is burnt to produce a main flame.
a is a sectional view taken along the line A—A in FIG. 1.
However, the thickness of the planar hollow column 250 is reduced, so that the thickness 270 of the passage 410 in the planar hollow column 250 is relatively reduced. Accordingly, the fuel passing through the hollow column 250 flows two-dimensionally. Thus, a vortex 900 occurs in the vicinity of a tip end 420 of the hollow column 250. If a plurality of fuel injection ports 260 are formed in one hollow column 250, the vortex occurs around the injection port 260a that is most distant from the axis B of the fuel nozzle 200. Therefore, it is difficult to inject fuel through the injection port 260a. Accordingly, the flow coefficient of the farmost injection port 260a is smaller than that of other injection ports, and a deviation of the flow coefficient between the farmost injection port 260a and the other injection ports is increased. Thus, the stability of injection of fuel is reduced as the flow coefficient is decreased. There is a possibility that a combustion vibration may occur because uniform pre-mixed air is not produced due to scattering of a flow coefficient.
If pre-mixed air in which a mixture of fuel and air is unbalanced is used, NOx is formed. Therefore, it is necessary to produce pre-mixed air having a uniform concentration to reduce NOx. However, in a combustor containing a fuel nozzle disclosed in Japanese Patent Application No. 2001-173005, the concentration of fuel becomes high in the vicinity of the axis B of the fuel nozzle 200 and becomes low in the vicinity of the injection port 260a due to the vortex 900. Accordingly, it is difficult to produce pre-mixed air that is uniformly mixed. It is preferable that the amount of fuel injected from the injection port be determined in accordance with only the size of the injection port, regardless of the distance of the injection port from the axis. In terms of reduction of NOx, it is necessary to avoid scattering of a flow coefficient in each injection port.
Therefore, the object of the present invention is to provide a combustor containing a fuel nozzle in which a vortex cannot occur in a hollow column.
To achieve the above object, one embodiment of the present invention provides a combustor comprising a fuel nozzle which is comprised of a rodlike body which has a fuel passage and which is located in an air passage; a plurality of hollow members which are connected to the fuel passage and which extend in radial directions from the rodlike body into the air passage; at least one injection port formed in each hollow member to inject a fuel from the fuel passage into the air passage; and a projection which extends from a farmost inner wall of each hollow member that is most distant from an axis of the rodlike body to the injection port that is most distant from the axis.
Namely, according to the one embodiment of the present invention, fuel can be uniformly injected through the injection port because an occurrence of a vortex in the hollow column can be prevented. Thus, uniformly mixed pre-mixed air can be produced because the occurrence of NOx can be reduced. A combustion vibration can be prevented because the flow coefficient can be stabilized.
According to a other embodiment of the present invention, there is provided a combustor comprising a fuel nozzle which is comprised of a rodlike body which has a fuel passage and which is located in an air passage; a plurality of hollow members which are connected to the fuel passage and which extend in radial directions from the rodlike body into the air passage; at least one injection port formed in each hollow member to inject a fuel from the fuel passage into the air passage, wherein a hole which is connected to the air passage and through which the fuel leaks is formed in a farmost inner wall of each hollow member that is most distant from an axis of the rodlike body.
Namely, according to another embodiment of the present invention, the occurrence of the vortex can be relatively easily prevented, without providing a projection, by leaking a part of fuel through a hole. Accordingly, the occurrence of NOx can be reduced because the uniformly mixed pre-mixed air can be produced. The combustion vibration can be prevented because the flow coefficient can be stabilized. Also, the combustor containing such a fuel nozzle can be easily manufactured at a low cost.
According to another embodiment of the present invention, there is provided a combustor comprising a fuel nozzle which is comprised of a rodlike body which has a fuel passage and which is located in an air passage; a plurality of hollow members which are connected to the fuel passage and which extend in radial directions from the rodlike body into the air passage; at least one injection port formed in each hollow member to inject a fuel from the fuel passage into the air passage; wherein an inner wall of each hollow member is formed to be adjacent to all the injection port on an upstream or downstream side in the direction of the airflow.
Namely, according to the other embodiment of the present invention, the occurrence of the vortex can be relatively easily prevented without providing the projection. Accordingly, the occurrence of NOx can be reduced because the uniformly mixed pre-mixed air can be produced. A combustion vibration can be prevented because the flow coefficient can be stabilized. Also, the combustor containing such a fuel nozzle can be easily manufactured at a low cost.
These and other objects, features and advantages of the present invention will be more apparent, in light of the detailed description of exemplary embodiments thereof, as illustrated by the drawings.
The present invention will be more clearly understood from the description as set below with reference to the accompanying drawings, wherein:
a is a sectional view taken along the line A—A in
b is a partially enlarged view in which a fuel nozzle contained in a gas turbine combustor is enlarged;
a is an axial direction sectional view of a fuel nozzle contained in a gas turbine combustor according to a fourth embodiment of the present invention; and
b is an axial direction sectional view of a fuel nozzle contained in a gas turbine combustor according to a fifth embodiment of the present invention.
Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following drawings, similar members are designated by the same reference numerals. The scale of these drawings is changed as necessary for easy understanding.
As shown in
During operation air is supplied into the air passage around the fuel nozzle 20 and, then, it flows in the axial direction of the fuel nozzle 20. Fuel is supplied from a source of fuel (not shown) into the fuel nozzle 20. The fuel flows toward the plural hollow columns 25 through the passage 51 in the rodlike body 21 of the fuel nozzle 20 and, then flows outwardly through the passages 41 of the hollow columns 25 in radial directions. Finally, the fuel is injected into the air passage, in a direction perpendicular to the airflow, through the plural injection ports 26 formed in each hollow column 25. As described above, in this embodiment, the projection 40 is formed in the hollow column 25. The projection 40 shields and prevents the swirl component of the flow of fuel in the vicinity of the tip end 42 of the hollow column 25 and, thus the occurrence of vortex can be prevented.
The amount of flow of fuel injected from each injection port 26 in one hollow column 25 becomes substantially equal by preventing the occurrence of the vortex. Accordingly, pre-mixed air in which air and fuel are uniformly mixed can be produced. Therefore, the amount of NOx, produced when the pre-mixed air is burnt, can be reduced and the flow coefficient can be stabilized and, thus, the combustion vibration can be prevented.
As shown in
Similar to the above-described embodiment, such columnar member 46 shields the swirl components in the passage 41 of the hollow column 25 so as to prevent the occurrence of a vortex. Therefore, the amount of flow of fuel injected from each injection port 26 in one hollow column 25 becomes substantially equal and the flow coefficient of each injection port 26 becomes substantially equal. Accordingly, pre-mixed air in which air and fuel are uniformly mixed can be produced. Therefore, the occurrence of NOx can be prevented when the pre-mixed air is burnt, and the flow coefficient can be stabilized and, thus, combustion vibration can be prevented. In this embodiment, the hollow column 25 according to this embodiment can be formed by only inserting the columnar member 46 into the opening for the core. Namely, the hollow column 25 according to this embodiment can be easily formed at a low cost in comparison with the hollow column according to the first embodiment formed by electric discharge machining. Therefore, the combustor comprised of the fuel nozzle containing such hollow column 25 can be easily manufactured at a low cost.
The opening 45 according to this embodiment makes fuel leak from the hollow column 25 during operation. A part of the fuel leaks through the opening 45, so that a revolving flow is not produced in the vicinity of the tip end of the hollow column 25 and, thus the occurrence of a vortex can be prevented. Therefore, the flow coefficient of the injection port 26a that is most distant from the axis B is larger than that of related art, and a difference between the flow coefficient of the injection port 26a and that of other injection ports 26 is reduced. Consequently, the occurrence of NOx can be reduced because uniformly mixed pre-mixed air can be produced, the flow coefficient can be stabilized and, thus, combustion vibration can be prevented. In this embodiment, as the hole for the core to be used in casting operation can be used as the opening for leaking fuel, the hollow column according to this embodiment can be easily formed at a low cost in comparison with the hollow column according to the first embodiment formed by electric discharge machining. Therefore, the combustor comprised of the fuel nozzle containing such hollow column 25 can be easily manufactured at a low cost. The amount of flow of fuel in this embodiment is larger than that in other embodiments because the opening 45 for leaking fuel is provided. Therefore, it is preferable that the size of the injection port 26 in this embodiment is smaller than that in the above described other embodiments.
a and 8b are axial direction sectional views of fuel nozzles contained in gas turbine combustors according to fourth and fifth embodiments of the present invention, respectively. In these embodiments, the above described projection, opening and columnar member are not provided, and inner walls 48, 44 of the hollow column 25 that are positioned on an upstream or downstream side in the direction of the airflow are disposed to be adjacent to the injection port 26. In
The amount of the flow of fuel passing through each injection port 26 is reduced by positioning the inner wall of the hollow column 25 as shown in
In the above-described embodiment, the injection port is formed so that fuel is injected in a direction perpendicular to the airflow. However, an injection port formed so that fuel is injected in a direction parallel with the airflow is within the scope of the present invention.
According to the present invention, fuel can be uniformly injected through the injection port because the occurrence of the vortex in the hollow column can be prevented. Thus, there can be obtained a common effect in which the occurrence of NOx can be reduced because the uniformly mixed pre-mixed air can be produced, and the combustion vibration can be prevented because the flow coefficient can be stabilized.
Although the invention has been shown and described with exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto without departing from the spirit and the scope of the invention.
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