Patent Application
20150362193
The present invention relates to a combustor including a burner (main burner) performing a premixed combustion, and a gas turbine using the combustor.
For example, Patent Literature 1 describes a combustor employing a premixed combustion system. This combustor includes not only a main burner performing a premixed combustion but also a pilot burner for diffusion combustion to stably keep the premixed combustion. A diffuse flame generated by the pilot burner is used as a pilot light by which the main burner generates a premixed flame, thereby keeping the premixed combustion. In a general combustor, a main burner is equally spaced in the circumferential direction radially and outwardly about a pilot burner.
The main burner includes a main nozzle and a main swirler in a cylindrical burner external cylinder (main burner cylinder). An extension tube is connected to a leading end of the burner external cylinder. The main burner mixes a fuel and air inside to generate premixed gas, and injects the generated premixed gas from the leading end of the extension tube. More specifically, the main nozzle injects a fuel to compressed air, which is supplied from a compressor (not illustrated), at an upstream side of the main swirler, and the main swirler swirls the flow of the air and the fuel. This generates premixed gas that is a mixture of air and fuel, and also generates a swirl flow of the premixed gas. The premixed gas is injected from the extension tube, and further combusted with the diffusion flame generated by the pilot burner at the downstream side of the extension tube. Thus, a premixed combustion is implemented.
Meanwhile, flashback of the main burner is likely to occur due to a low flow rate in the vicinity of an inner wall face of the extension tube. The occurrence of flashback leads to a fire damage of the combustor. Therefore, the flashback has to be prevented as much as possible. Patent Literature 1 describes that the shape of the extension tube is improved and film air is introduced from a joint portion of the burner external cylinder and the extension tube, in order to prevent the flashback. The extension tube is shaped such that an inlet is circular according to the burner external cylinder, and an outlet is formed into a trapezoid having two radial edges and circumferential edges which are a radially inward edge and a radially outward edge for connecting the respective radial edges.
Patent Literature 1: Japanese Unexamined Patent Publication No. 2006-78127
The configuration in which the outlet of the extension tube is trapezoidal and film air is introduced as described in Patent Literature 1 can prevent flashback. However, the extension tube has the circular inlet and the outlet deformed into a trapezoid, so that a high flow rate portion and a low flow rate portion are generated on the outlet of the extension tube. This might cause unevenness in the introduced film air. In addition, since flashback is likely to occur on the low flow rate portion at the outlet of the extension tube, film air is demanded to be introduced especially into this portion.
The present invention is accomplished to solve the above problems, and aims to provide a combustor and a gas turbine which can prevent unevenness of film air, while preventing an occurrence of flashback.
According to an aspect of the present invention, a combustor includes: a pilot burner; a plurality of main burners, each of which is provided radially and outwardly along a circumferential direction about the pilot burner, and is including a main nozzle disposed in a main burner cylinder; an extension tube extending toward a downstream side from the main burner cylinder of each of the main burners, including a circular inlet communicating with the main burner cylinder, and including an outlet at the downstream side formed of two radial edges parallel to the radial direction and two circumferential edges formed along the circumferential direction so as to connect both ends of the radial edges; an air passage formed outside of the main burner cylinder; and an inner communication hole formed at a position corresponding to the radially and inwardly circumferential edge on a side of the inlet of the extension tube to communicate between the air passage and an inside of the extension tube.
According to this combustor, the inner communication hole is formed, whereby air is introduced into the main burner cylinder from the air passage through the inner communication hole The air becomes film air to be flowing downward along the inner wall faces of the main burner cylinder and the extension tube. This film air reduces a fuel concentration in a low flow rate region near the wall face. Consequently, an occurrence of flashback can be prevented. Especially, the radially and inwardly circumferential edge is a portion which is close to the flame from the pilot burner and so is greatly affected by the flashback. When the film air is supplied corresponding to this portion, the occurrence of flashback can be prevented, and unevenness of film air can be prevented.
Advantageously, the combustor further includes a corner communication hole formed at a position corresponding to corners that communicate at least the radially and outwardly circumferential edge and the radial edge on the side of the inlet of the extension tube and, except for the position of the inner communication hole, to communicate between the air passage and the inside of the extension tube.
The corner where the circumferential edge and the radial edge are in communication with each other is the portion where a fluid is diffused in the radial direction from the circular inlet, and so the flow rate is particularly liable to be reduced. According to the combustor described above, the inner communication hole corresponding to the corner is formed, whereby an effect of preventing the unevenness of film air and preventing the occurrence of flashback can significantly be obtained.
Advantageously, in the combustor, the inner communication hole is continuously formed in the circumferential direction, and the corner communication hole is continuously formed in the circumferential direction at the position corresponding to the corners that communicate the radially and outwardly circumferential edge and the radial edge.
According to the combustor described above, film air is supplied based on a portion where a velocity is low. Accordingly, the combustor can significantly provide an effect of preventing the unevenness of film air and preventing the occurrence of flashback.
Advantageously, in the combustor, the inner communication hole is formed to have a larger aperture area than that of the corner communication hole.
The radially and inwardly circumferential edge is a portion which is close to the flame from the pilot burner and so is greatly affected by the flashback. In view of this, the combustor described above is preferably configured such that the inner communication hole is formed to have a larger aperture area than that of the corner communication hole in order to significantly provide an effect of preventing an occurrence of flashback.
Advantageously, in the combustor, the inner communication hole is continuously formed in the circumferential direction, and the corner communication hole is discontinuously formed in the circumferential direction.
Since the corner communication hole is discontinuously formed within the range excluding the inner communication hole, the combustor described above can supply a relatively large amount of air to the inner communication hole corresponding to the radially and inwardly circumferential edge that is the portion close to the flame from the pilot burner and so is greatly affected by flashback.
According to another aspect of the present invention, a combustor includes: a pilot burner; a plurality of main burners, each of which is provided radially and outwardly along a circumferential direction about the pilot burner, and is including a main nozzle disposed in a main burner cylinder; an extension tube extending toward a downstream side from the main burner cylinder of each of the main burners, including a circular inlet communicating with the main burner cylinder, and including an outlet at a downstream side formed of two radial edges parallel to the radial direction and two circumferential edges formed along the circumferential direction so as to connect both ends of the radial edges; an air passage formed outside of the main burner cylinder; and a corner communication hole formed at a position corresponding to corners that communicate the radially and outwardly circumferential edge and the radial edge on a side of the inlet of the extension tube.
The corner where the circumferential edge and the radial edge are in communication with each other is the portion where a fluid is diffused in the radial direction from the circular inlet, and so the flow rate is particularly liable to be reduced. According to the combustor described above, the inner communication hole corresponding to the corner is formed, whereby an effect of preventing the unevenness of film air and preventing the occurrence of flashback can significantly be obtained.
Advantageously, the combustor further includes: a plurality of main swirlers provided to radially extend in the main burner cylinder; and a vane communication hole formed at a position corresponding to the downstream end of the main swirler to communicate between the air passage and the inside of the main burner cylinder.
The flow rate is likely to be reduced and, the fuel concentration tends to be increased, at the upstream side of the main swirler. Accordingly, when the vane communication hole is formed on the position corresponding to the downstream end of the main swirler, the air introduced from the vane communication hole into the main burner cylinder can block flames of flashback.
According to still another aspect of the present invention, a gas turbine includes: a compressor; a combustor; and a turbine, and any one of the above combustor is applied.
The gas turbine described above can prevent damage on the combustor through the prevention of flashback, and therefore, can maintain turbine performance.
According to the present invention, and unevenness of film air can be prevented while preventing an occurrence of flashback.
An embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited by the embodiment. The elements in the embodiment below include those that are easily substitutable by a person skilled in the art or that are substantially equivalents thereof.
The compressor 11 has an air inlet port 15 from which air is introduced, and has a plurality of stator vanes 17 and rotor blades 18 which are provided alternately in a compressor casing 16. The combustor 12 supplies a fuel to compressed air (combustion air) compressed by the compressor 11, and can combust the air with an ignition with the burner. The turbine 13 includes a plurality of nozzles 21 and rotor blades 22 which are provided alternately in a turbine casing 20. The exhaust chamber 14 has an exhaust diffuser 23 formed continuously with the turbine 13. The rotor 24 is disposed so as to penetrate through the radially central parts of the compressor 11, the combustor 12, the turbine 13, and the exhaust chamber 14. The end of the rotor 24 at the side of the compressor 11 is supported by a bearing 25, while the end at the exhaust chamber 14 is supported by a bearing 26 so as to be rotatable about the rotation axis L. A plurality of disk plates are fixed to the rotor 24, and each of the rotor blades 18 and 22 is connected thereto. Further, a drive shaft of a power generator not illustrated is connected to the end of the rotor 24 at the side of the compressor 11.
In the gas turbine configured as described above, air introduced from the air inlet port 15 of the compressor 11 is compressed through a plurality of stator vanes 17 and rotor blades 18 to be turned into high-temperature and high-pressure compressed air. The combustor 12 supplies a predetermined fuel to this compressed air to combust the air. The high-temperature and high-pressure combustion gas that is an operating fluid generated in the combustor 12 passes through the plurality of nozzles 21 and the rotor blades 22 included in the turbine 13 to rotationally drive the rotor 24. This drives the power generator connected to the rotor 24. The exhaust gas passing through the rotor 24 is transformed into a static pressure with the exhaust diffuser 23 in the exhaust chamber 14, and then, exhausted to the atmosphere.
The external cylinder 31 is fixed to a casing housing 27 forming the turbine casing 20. A pilot burner 35 is provided along the center axis S at the central part of the inner cylinder 32. A plurality of main burners 36 are provided around the pilot burner 35 at the central part in the inner cylinder 32. The main burners 36 are equally spaced and parallel to the pilot burner 35 along the circumferential direction about the center axis S so as to surround the pilot burner 35 radially and outwardly about the pilot burner 35 (center axis S). The base end of the transition piece 33 is formed into a cylinder, and connected to the inner cylinder 32. The transition piece 33 is formed such that its cross-section is curved to be smaller toward the leading end, and is open toward the first-stage nozzle 21 of the turbine 13.
The pilot burner 35 has a pilot nozzle 35a formed at its tip end and disposed in a combustion cylinder 35A that is cylindrical and has a widened leading end. The pilot burner 35 also has a pilot swirler 35B disposed between its outer peripheral surface and an inner peripheral surface of the combustion cylinder 35A.
The main burner 36 has a main nozzle 36a formed at its tip end and disposed in a cylindrical main burner cylinder 36A. An extension tube 36B is provided to the main burner cylinder 36A at the downstream side where a fuel is injected with the main nozzle 36a (right side in
As illustrated in
The main burner 36 also has a main swirler 36C disposed between the outer peripheral surface of the main nozzle 36a and the inner peripheral surface of the main burner cylinder 36A.
The external cylinder 31 has a top-hat portion 34 at its base end. The top-hat portion 34 is disposed along the inner peripheral surface of the base end of the external cylinder 31, and includes a cylindrical member 34A that forms a part of the air passage 30 at the outside of the external cylinder 31 and a lid member 34B that closes an opening at the base end of the cylindrical member 34A. The base end of the above pilot burner 35 is supported to the lid member 34B, and a fuel port 35C of the pilot burner 35 is disposed outside the lid member 34B. A pilot burner fuel line not illustrated is connected to the fuel port 35C to supply a fuel to the pilot burner 35. In addition, the base end of the above main burner 36 is supported to the lid member 34B, and a fuel port 36D of the main burner 36 is disposed outside the lid member 34B. A main burner fuel line not illustrated is connected to the fuel port 36D to supply a fuel to the main burner 36.
A partition wall 37 is provided at the base end of the external cylinder 31 in the cylindrical member 34A of the top-hat portion 34. With this partition wall 37, the air passage 30 is in communication with the inner cylinder 32. A straightening vane 38 is provided at the inlet portion of the air passage 30 and between the external cylinder 31 (cylindrical member 34A of the top-hat portion 34) and the inner cylinder 32. The straightening vane 38 is a porous vane formed to close the air passage 30 and to have many pores for allowing the upstream side and the downstream side of the air passage 30 to be in communication with each other.
When high-temperature and high-pressure compressed air flows into the air passage 30 in the gas turbine combustor 12 as described above, the compressed air is straightened through the straightening vane 38 and turned back by the partition wall 37 at the base end of the inner cylinder 32, thereby being guided to the combustion cylinder 35A of the pilot burner 35 and the main burner cylinder 36A of the main burner 36. The compressed air then becomes an airflow swirling with the main swirler 36C in the main burner cylinder 36A in the main burner 36, is mixed with the fuel injected from the main nozzle 36a in the extension tube 36B to become premixed gas, and flows into the transition piece 33. The compressed air also becomes an airflow swirling with the pilot swirler 35B in the combustion cylinder 35A in the pilot burner 35, is mixed with the fuel injected from the pilot nozzle 35a, combusted with an ignition with a pilot fire not illustrated to become combustion gas, and injected into the transition piece 33. In this case, a part of the combustion gas is injected so as to be diffused with flames in the transition piece 33, whereby the premixed gas flowing into the transition piece 33 from each main burner 36 is ignited and combusted.
Specifically, flame stabilization for stable combustion of the lean premixed fuel from the main burner 36 can be attained by the diffusion flame with the pilot fuel injected from the pilot burner 35. Further, the premixing of the fuel by the main burner 36 can equalize the fuel concentration to reduce NOx. In this case, the insides of the main burner cylinder 36A of the main burner 36 and the extension tube 36B become a premixing region, while the region where the premixed gas is combusted with the diffusion flame from the pilot burner 35 becomes a combustion region. The combustion region is downstream of the combustion cylinder 35A and inside the transition piece 33. Therefore, the combustion gas formed by the combustion of the premixed gas flows into the transition piece 33.
In the premixed combustor 12 as described above, the premixed gas flowing into the main burner cylinder 36A becomes a swirl flow at the downstream of the main swirler 36C. This tends to cause flashback from the combustion region to the premixing region. Specifically, the fuel injected from the main nozzle 36a is made uniform throughout the inside of the main burner cylinder 36A with the swirl flow. With this, the distribution of the fuel concentration is almost constant from the central part to the inner wall face of the main burner cylinder 36A. On the other hand, the velocity of the premixed gas is zero on the inner wall face, increases with distance from the inner wall face (velocity boundary layer), and becomes almost constant at the outside of the velocity boundary layer (at the central part of the main burner cylinder 36A). Specifically, the velocity boundary layer where the velocity is low is present in the vicinity of the inner wall face of the main burner cylinder 36A and the extension tube 36B, while the fuel concentration is high in the velocity boundary layer. Therefore, flashback from the combustion region is likely to occur in this velocity boundary layer.
Especially, in the present embodiment, the extension tube 36B is formed such that the inlet 36Ba is formed into a circular shape and the outlet 36Bb is formed into a trapezoidal shape. It has been found according to the study by the present inventors that a portion where a flow rate is low is generated at the outlet 36Bb of the extension tube 36B with this structure. Specifically, this phenomenon is noticeable at the portion of the radially and inwardly circumferential edge 36Bd and both of radially outward corners 36Be. Accordingly, flashback is likely to occur at the portion where the flow rate is low, and this might increase the temperature of the inner wall face of the extension tube 36B to damage the combustor 12. In order to avoid this, the main burner 36 is configured as described below in the present embodiment.
As illustrated in
In
The predetermined range will be described. As illustrated in
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Especially, the combustor 12 according to the present embodiment includes the inner communication hole H1a and the corner communication hole H1b formed to correspond to the portion where the flow rate is low at the outlet 36Bb of the extension tube 36B. This configuration can further prevent the unevenness of film air, while preventing the occurrence of flashback.
The combustor 12 according to the present embodiment can significantly provide the effect of preventing the unevenness of film air while preventing the occurrence of flashback by forming both the inner communication hole H1a and the corner communication hole H1b. Even when only one of the inner communication hole H1a and the corner communication hole H1b is formed, the effect of preventing the unevenness of film air and preventing the occurrence of flashback can be obtained. When one of the inner communication hole H1a and the corner communication hole H1b is formed, the inner communication hole H1a corresponding to the radially and inwardly circumferential edge 36Bd, which is the portion close to the flame from the pilot burner 35 and so is greatly affected by flashback, is preferably formed. Alternatively, when one of the inner communication hole H1a and the corner communication hole H1b is formed, the corner communication hole H1b corresponding to the corner 36Be where the fluid is diffused in the radial direction and so the flow rate is particularly liable to be reduced, is preferably formed.
The radially and inwardly circumferential edge 36Bd is the portion close to the flame from the pilot burner 35 and so is greatly affected by flashback. Therefore, when both the inner communication hole H1a and the corner communication hole H1b are formed, the inner communication hole H1a is preferably formed to have a larger aperture area than that of the corner communication hole H1b to significantly obtain the effect of preventing the occurrence of flashback.
In
The predetermined range will be described. As illustrated in
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Especially, the combustor 12 according to the present embodiment includes the inner communication hole H1a and the corner communication hole H1b formed to correspond to the portion where the flow rate is low at the outlet 36Bb of the extension tube 36B. This configuration can significantly provide an effect of preventing the unevenness of film air while preventing the occurrence of flashback. In addition, the corner communication hole H1b is discontinuously formed within the range excluding the inner communication hole H1a, and with this, relatively large amount of air can be supplied to the inner communication hole H1a corresponding to the radially and inwardly circumferential edge 36Bd that is the portion close to the flame from the pilot burner 35 and so is greatly affected by flashback.
Meanwhile, the flow rate is likely to be reduced, so that the fuel concentration tends to be increased, at the upstream side of the main swirler. When a vane communication hole H2 is formed on the position corresponding to the downstream end of the main swirler, the compressed air is introduced from the vane communication hole H2 into the main burner cylinder 36A, and this compressed air can block flames of flashback.
Furthermore, the gas turbine 10 having the above combustor 12 can prevent damage on the combustor 12 because of the prevention of flashback, and therefore, can maintain turbine performance.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-018481 | Feb 2013 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/050360 | 1/10/2014 | WO | 00 |
