JP6038674B2 - Gas turbine combustor and gas turbine - Google Patents

Description

  Embodiments described herein relate generally to a gas turbine combustor and a gas turbine.

  In a gas turbine used in a gas turbine plant, a combined cycle plant, or the like, the operating conditions are high temperature and high pressure to increase efficiency, and NOx emissions tend to increase. As a factor of NOx generation, flame temperature is dominant. Therefore, in order to suppress the generation of NOx, it is effective to lower the flame temperature.

  Premixed lean combustion is used as a combustion method that suppresses local increase in flame temperature and suppresses NOx emissions. In this premixed lean combustion, a premixed gas in which fuel and air are premixed under fuel lean conditions is burned.

  Premixed lean combustion has a drawback that the combustion range is narrow, and various devices have been made to compensate for this drawback. In the gas turbine combustor, for example, the above-described premixed lean combustion is used in combination with diffusion combustion having a wide combustion range and capable of stable combustion. Further, in order to stabilize the flame in the premixed lean combustion, the temperature in the combustion region is always set to a predetermined temperature or more, or a flame holding mechanism is provided.

  FIG. 8 is a view showing a cross section of a conventional gas turbine combustor 200. FIG. 9 is a view schematically showing a cross section of the premixing duct 214 in the conventional gas turbine combustor 200. FIG. 10 is a plan view of the premixing duct 214 in the conventional gas turbine combustor 200 as viewed from the outlets 220a, 221a, and 222a side.

  As shown in FIG. 8, the gas turbine combustor 200 includes a combustor liner 211 having a pilot nozzle 210 in the center on the head side, and a premixing duct 214 around the combustor liner 211.

  The periphery of the combustor liner 211 is covered with a gas turbine outer cylinder 213. The premixing duct 214 is provided between the combustor liner 211 and the gas turbine outer cylinder 213, and forms a premixed gas composed of fuel and air. A plurality of premixing ducts 214 are provided in the circumferential direction.

  High-temperature and high-pressure combustion air 216 from a compressor (not shown) cools the wall surface of the combustor liner 211, and between the combustor liner 211 and the gas turbine outer cylinder 213, the head of the premixing duct 214. It flows toward the club side.

  A part of the air 216 flows into the pilot nozzle 210 as air for a pilot flame (not shown). The remaining air 216 flows into the premixing duct 214, mixes with the fuel 218 injected from the main fuel nozzle 217, and becomes a premixed gas.

  The premixing duct 214 is formed with three branch paths 220, 221, and 222 that communicate with the combustion chamber 215 in the combustor liner 211 along the axial direction of the combustor liner 211 (the axial direction of the premixing duct 214). Has been. Then, the premixed gas is supplied to the combustion chamber 215 via the outlets 220a, 221a, and 222a of the branch paths 220, 221, and 222.

  As shown in FIGS. 9 and 10, the opening area of the outlet is configured to increase with the order of the outlet 220a, the outlet 222a, and the outlet 221a. That is, the opening area of the outlet 220a on the most upstream side is the smallest, and the opening area of the second outlet 221a adjacent to the outlet 220a is the largest.

  Further, in the premixing duct 214, the channel cross-sectional area of the main channel 223 that guides the premixed gas to the respective branch channels 220, 221, and 222 is configured to gradually decrease as it goes downstream. .

  The total opening area of each outlet 220a, 221a, 222a is determined by the speed setting of the premixed gas that flows into the combustion chamber 215. Further, the opening area of each outlet 220a, 221a, 222a is determined in consideration of the flame stability in the combustion chamber 215.

  In the combustion chamber 215, a recirculation region 219 is formed on the upstream side of the combustion chamber 215 due to the swirling flow of air 216 and fuel 218 that has passed through the pilot nozzle 210 during combustion. The recirculation region 219 maintains flame stability. An outlet 220a is located at a portion immediately downstream of the recirculation region 219. Part of the premixed gas flowing into the combustion chamber 215 from the outlet 220a is taken into the recirculation region 219, and the rest flows downstream.

  When the flow rate of the premixed gas from the outlet 220a is large, the formation of the recirculation region 219 is affected, and a stable flame cannot be obtained. Therefore, the opening area of the outlet 220a is minimized. The opening area of the outlet 221a is maximized, a large amount of premixed gas is introduced downstream of the recirculation region 219 and at a position that does not affect the recirculation region 219, and combustion is promoted.

  In such a premixing duct 214, the premixed gas first flows into the combustion chamber 215 from the outlet 220a, then flows into the combustion chamber 215 from the outlet 221a, and finally from the outlet 222a.

  Here, FIG. 11 is a view showing the flow velocity of the premixed gas in the vicinity of the wall surface along the wall surface of the conventional premixing duct 214 on the side facing the side where the branch path 220 is formed. The horizontal axis in FIG. 11 indicates the axial distance from the inlet to the outlet 222a in the premixing duct 214. The results shown in FIG. 11 are obtained by three-dimensional fluid analysis.

  As shown in FIG. 11, the flow velocity slightly decreases downstream of the outlet 220a, and the flow velocity decreases greatly downstream of the outlet 221a. This is because a large amount of premixed gas flows out from the outlet 221a having the largest opening area. The flow rate of the premixed gas then increases to the outflow rate at the outlet 222a.

JP 2000-346360 A

  When speed fluctuations occur due to changes in operating conditions of the gas turbine, the flame in the combustion chamber 215 may backfire into the premixing duct 214. In that case, if there is a deceleration zone in the flow of the premixed gas, the flame may stay in that portion and hold the flame. Flame holding in the premixing duct 214 leads to burning of the premixing duct 214.

  Therefore, in order to prevent the deceleration region on the downstream side of the outlet 221a in the premixing duct 214, it is conceivable to reduce the cross section of the flow path corresponding to the flow rate of the premixed gas. However, it is difficult to realize with a structure such as the premixing duct 214 that does not have a rectifying function inside. In addition, providing a structure inside the premixing duct 214 or complicating the shape of the inside tends to cause a complicated flow, and a vortex or a new deceleration region is likely to occur.

  A problem to be solved by the present invention is to provide a gas turbine combustor and a gas turbine capable of preventing flame holding due to backfire in a premixed duct forming a premixed gas and preventing the premixed duct from being burned out. To do.

The gas turbine combustor according to the embodiment includes a cylindrical combustor liner that forms a combustion chamber, a pilot fuel injection unit provided in the center of the head of the combustor liner, and an inlet that opens toward the upstream side. a, wherein extending in the axial direction of the combustor liner to the outer periphery of the combustor liner has a main flow path of decreasing with flow path cross-sectional area toward the downstream, and the fuel supplied to the combustion chamber A plurality of premixing ducts that form a premixed gas composed of air and the premixing ducts along the axial direction of the combustor liner, and the outlet opening area increases as it is located downstream from the main flow path; A branch path for branching the premixed gas to the combustion chamber.

It is a figure showing a meridional section of a gas turbine provided with a gas turbine combustor of an embodiment. It is a figure which shows the cross section of the gas turbine combustor of embodiment. It is the figure which showed typically the cross section of the premixing duct in the gas turbine combustor of embodiment. It is a top view when the premixing duct in the gas turbine combustor of the embodiment is viewed from the outlet side. It is the figure which showed the change of the axial direction of the premixing duct of the cross-sectional area of the main flow path and the branch path in the premixing duct of the gas turbine combustor of embodiment. It is the figure which showed the flow velocity of the premixed gas near the wall surface along the wall surface of the side facing the side where the branch path in the gas turbine combustor of the embodiment is formed. It is the figure which showed the flame holding range which flame-holds in a premixing duct in the relationship between the average flow rate ratio of the premixed gas in a premixing duct, and fuel concentration. It is the figure which showed the cross section of the conventional gas turbine combustor. It is the figure which showed typically the cross section of the premixing duct in the conventional gas turbine combustor. It is a top view when the premixing duct in the conventional gas turbine combustor is seen from the exit side. It is the figure which showed the flow velocity of the premixed gas of the wall surface vicinity along the wall surface of the side facing the side in which the branch path in the conventional premixing duct was formed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a meridional section of a gas turbine 150 including the gas turbine combustor 10 according to the embodiment. In FIG. 1, the gas turbine combustor 10 is not shown in cross section.

  As shown in FIG. 1, the gas turbine 150 mainly includes a compressor 151, a gas turbine combustor 10, and a turbine 152. In the compressor 151, air is sucked from the atmosphere and used as high-temperature and high-pressure combustion air. In the gas turbine combustor 10, fuel is mixed with combustion air from the compressor 151 and burned to generate high-temperature and high-pressure combustion gas. In the turbine 152, work is performed by passing the combustion gas generated by the gas turbine combustor 10, and rotational force is obtained. The combustion gas discharged from the gas turbine combustor 10 flows into the turbine 152 through the transition piece 153.

  The rotational force obtained by the turbine 152 is transmitted to the compressor 151 and drives the compressor 151. Further, this rotational force is transmitted to a generator (not shown) and is taken out as a shaft output. Combustion gas that has worked in the turbine 152 is exhausted from the gas turbine 150 to the outside.

  Next, the configuration of the gas turbine combustor 10 according to the embodiment will be described.

  FIG. 2 is a diagram illustrating a cross section of the gas turbine combustor 10 according to the embodiment. As shown in FIG. 2, the gas turbine combustor 10 includes a combustor liner 22 that is housed in a gas turbine casing 20 and is an inner cylinder that is concentrically formed as a double cylinder in an outer cylinder 21. A pilot fuel injection unit 30 is provided at the center of the head of the combustor liner 22. The pilot fuel injection unit 30 is provided coaxially with the central axis of the combustor liner 22 at the head of the combustor liner 22, for example. Further, on the downstream side of the combustor liner 22, there is provided a transition piece 153 that is constituted by a double cylinder including an outer cylinder 153a and an inner cylinder 153b and guides combustion gas to the turbine 152 through the inner cylinder 153b. Yes.

  The combustor liner 22 forms a cylindrical combustion chamber 23 that generates combustion gas that drives the gas turbine 150, and forms an air passage 24 between the outer cylinder 21. In this air passage 24, high-pressure air AR from the compressor 151 introduced between the outer cylinder 153a and the inner cylinder 153b from an ejection hole (not shown) formed in the outer cylinder 153a of the transition piece 153. However, it flows toward the pilot fuel injection unit 30 side. At this time, the high-pressure air AR flows while cooling the inner cylinder 153 b of the transition piece 153 and the combustor liner 22.

  The air passage 24 is provided with a premixing duct 40 extending along the axial direction of the combustor liner 22. A plurality of premixing ducts 40 are provided in the circumferential direction of the outer periphery of the combustor liner 22. In the premixing duct 40, the premixed gas composed of the fuel F and the air AR is guided into the combustor liner 22 (combustion chamber 23) along the axial direction of the combustor liner 22 (axial direction of the premixing duct 40). Three branch paths 42, 43, and 44 are provided. The premixed gas is jetted into the combustion chamber 23 from the outlets 42a, 43a, 44a of the branch paths 42, 43, 44.

  Here, an example in which the three branch paths 42, 43, and 44 are provided is shown, but it is sufficient that two or more branch paths are provided. The configuration of the premixing duct 40 will be described in detail later.

  A main fuel injection unit 50 that supplies fuel F into the premixing duct 40 is provided on the outer periphery of the pilot fuel injection unit 30. A fuel injection port 51 formed on an end surface of the main fuel injection unit 50 on the premixing duct 40 side is provided so as to face the inlet 41 of the premixing duct 40.

  The main fuel injection unit 50 and the pilot fuel injection unit 30 are accommodated in the outer cylinder 21. The main fuel injection part 50 extends from the head plate 25 to the premixing duct 40 side, and the pilot fuel injection part 30 extends from the head plate 25 to the head side of the combustor liner 22.

  For example, as shown in FIG. 2, the pilot fuel injection unit 30 includes a diffusion combustion fuel injection unit 31 for securing flame holding in the combustion chamber 23 in the center. From the diffusion combustion fuel injection section 31, for example, the fuel F injected into the air AR passing through the swirler 34 provided immediately upstream of the outlet is injected into the combustion chamber 23. On the outer periphery of the diffusion combustion fuel injection section 31, the fuel F is injected into the air AR that has passed through the swirler 34, and a premixed gas in which the fuel F and the air AR are premixed is injected into the combustion chamber 23. A fuel injection unit 32 is provided.

  The flow that flows out from the pilot fuel injection unit 30 into the combustion chamber 23 passes through swirlers 33 and 34 provided in the pilot fuel injection unit 30 to form a swirling flow. Therefore, as shown in FIG. 2, a recirculation region 26 formed by this swirling flow exists on the upstream side of the combustion chamber 23 (upstream side in the combustor liner) during the combustion reaction. By this recirculation region 26, a stable flame is formed on the upstream side of the combustion chamber 23.

  Here, the outlet 42 a of the branch path 42 located on the most upstream side is formed so as to be located immediately downstream of the recirculation region 26. That is, the upstream edge of the outlet 42 a is formed so as to be located immediately downstream of the recirculation region 26.

  On the other hand, the remainder of the combustion air AR guided to the pilot fuel injection unit 30 side through the air passage 24 is combined with the fuel F injected from the fuel injection port 51 of the main fuel injection unit 50 and the premixing duct 40. It is led from the inlet 41 into the premixing duct 40. Then, a premixed gas is formed in the premixing duct 40 and is led into the combustion chamber 23 via the branch paths 42, 43, 44 and burns.

  The pilot fuel injection unit 30 and the main fuel injection unit 50 are supplied with fuel F having a predetermined flow rate from a fuel supply mechanism (not shown).

  Here, the configuration of the premixing duct 40 will be described in more detail.

  Drawing 3 is a figure showing typically the section of premixing duct 40 in gas turbine combustor 10 of an embodiment. FIG. 4 is a plan view of the premixing duct 40 in the gas turbine combustor 10 according to the embodiment as viewed from the outlets 42a, 43a, and 44a. Note that the cross section of the flow path indicated by the broken line in FIG. 3 corresponds to the cross section of the flow path at a point indicated by a symbol in FIG.

  As shown in FIGS. 3 and 4, in the premixing duct 40, the channel cross-sectional area of the main channel 45 that guides the premixed gas to the branch channels 42, 43, 44 gradually decreases as it goes downstream. Is configured to do. The opening areas of the outlets 42a, 43a, 44a of the branch paths 42, 43, 44 are configured to increase as they are located downstream. That is, the opening area of the most upstream side outlet 42a is the smallest, and the opening area of the most downstream side outlet 44a is the largest.

  The opening areas of the outlets 42a, 43a, 44a are, for example, 18% to 22% for the outlet 42a, 25% to 35% for the outlet 43a, and 25% to 35% for the outlet 44a when the total opening area of the outlets 42a, 43a, 44a is 100%. It is preferably set in the range of 47 to 53%.

  Since the pressure of the premixed gas in the main channel 45 is substantially constant, and the pressure in the combustion chamber 23 is substantially constant, the outlets 42a, 43a, 43a, The flow rate of the premixed gas ejected from 44a is determined.

  Here, as described above, since the outlet 42a is formed immediately downstream of the recirculation region 26 that stabilizes the flame, a part of the premixed gas flowing into the combustion chamber 23 from the outlet 42a is recirculated. Captured in region 26. Therefore, it is necessary to eject the premixed gas from the outlet 42a to the extent that the formation of the recirculation region 26 is not affected. Therefore, the opening area of the outlet 42a is set to the above range. The flow rate of the premixed gas introduced into the combustion chamber 23 from the outlet 42a is, for example, about half of the flow rates of the fuel F and the air AR supplied to the pilot fuel injection unit 30.

  When the opening area is larger in the outlet 43a than in the outlet 44a, in the vicinity of the wall surface on the side facing the side where the branch path 42 is formed in the premixing duct 40, for example, A deceleration region in which the flow rate of the premixed gas is greatly reduced is generated downstream of the outlet 43a. Further, when the difference in opening area between the outlets 42a, 43a, 44a is small, in the vicinity of the wall surface on the side facing the side where the branch path 42 is formed in the premixing duct 40, for example, downstream of the outlet 43a. A deceleration region in which the flow rate of the premixed gas is greatly reduced is generated. When the deceleration region occurs, when the flame backfires in the premixing duct 40, the flame stays in the deceleration region and holds the flame. Therefore, in order to prevent formation of the deceleration region and prevent flame holding in the premixing duct 40, the opening areas of the outlet 43a and the outlet 44a are set to the above-described ranges.

  Here, FIG. 5 shows changes in the axial direction of the premixing duct 40 in the cross-sectional areas of the main flow path 45 and the branch paths 42, 43, 44 in the premixing duct 40 of the gas turbine combustor 10 of the embodiment. FIG. In FIG. 5, the cross-sectional area of the flow path at the inlet 41 of the premixing duct 40 is 1, and the cross-sectional areas of the flow paths are shown as area ratios. In FIG. 5, the change in the cross-sectional area of the main flow path 45 is indicated by a solid line, and the change in the cross-sectional area of the branch paths 42, 43, and 44 is indicated by a broken line. Further, as described above, the channel cross section at the point indicated by the symbol in FIG. 5 is indicated by a broken line in FIG.

  As shown in FIG. 5, the channel cross-sectional area of the main channel 45 gradually decreases as it goes downstream. Also in the branch paths 42, 43, 44, the flow path cross-sectional area decreases with going downstream (the outlets 42a, 43a, 44a).

  FIG. 6 is a diagram showing the flow velocity of the premixed gas near the wall surface along the wall surface on the side facing the side where the branch path 42 is formed in the premixing duct 40 of the gas turbine combustor 10 of the embodiment. is there. The horizontal axis in FIG. 6 indicates the axial distance from the inlet to the outlet 44a in the premixing duct 40. The results shown in FIG. 6 are obtained by three-dimensional fluid analysis. For comparison, FIG. 6 shows the flow velocity of the premixed gas in the vicinity of the wall surface along the wall surface on the side facing the side where the branch path 220 is formed in the conventional premixing duct 214 shown in FIG. It also shows.

  As shown in FIG. 6, in the premixing duct 40, there is no deceleration region downstream of the outlet 43a. On the other hand, as described above, in the conventional premixing duct 214, a deceleration region exists downstream of the outlet 221a.

  As described above, in the premixing duct 40 according to the embodiment, since there is no deceleration region of the premixed gas flow in the premixing duct 40, a speed fluctuation occurs due to a change in operating conditions of the gas turbine. At this time, even if the premixing duct 40 is backfired, the flame stays and does not hold the flame.

  FIG. 7 is a view showing a flame holding range in which the flame is held in the premixing duct 40 in the relationship between the average flow rate ratio of the premixed gas in the premixing duct 40 and the fuel concentration. Here, the horizontal axis shows the average flow rate ratio of the premixed gas, where the average flow velocity (set operation flow velocity) of the premixed gas ejected from the outlets 42a, 43a, 44a during normal operation is 1. The fuel concentration is high or low based on the fuel concentration at which the premixed gas has a stoichiometric ratio (equivalent ratio 1). FIG. 7 also shows a flame holding range in which flame is held in the conventional premixing duct 214 for comparison. The results shown in FIG. 7 were obtained by an actual pressure combustion test.

  Here, the inside of the line indicating the boundary of the flame holding range in FIG. 7 is the flame holding region. Further, FIG. 7 shows an allowable range (a range indicated by an arrow in FIG. 7) in which flame holding is not caused when the flow velocity fluctuates (decreases) from the set operation flow velocity. Here, the allowable range in the fuel concentration condition where the flame holding region is the widest and the premixed gas has the stoichiometric ratio (equivalent ratio 1) is shown.

  As shown in FIG. 7, when the average flow velocity is reduced, the range of the fuel concentration to be held is expanded. Further, in the premixing duct 40 of the embodiment, the flame holding region is narrow and the allowable range is wide as compared with the conventional premixing duct 214. That is, the premixing duct 40 of the embodiment shows that it is difficult to hold the flame in the premixing duct 40 even when a speed fluctuation occurs due to a change in the operating conditions of the gas turbine.

  Here, in the range of the normal change of the operating conditions of the gas turbine, it is a condition that cannot actually occur that the average flow velocity ratio falls below 0.75. Therefore, it can be said that the premixing duct 40 of the embodiment does not hold the flame in the premixing duct 40 even when a speed fluctuation occurs due to a change in operating conditions of the gas turbine.

  According to the gas turbine combustor 10 of the above-described embodiment, there is no deceleration region of the premixed gas flow in the premixed duct 40. For this reason, when a speed fluctuation occurs due to a change in operating conditions of the gas turbine or the like, even if a backfire occurs in the premixing duct 40, the flame stays and does not hold the flame. As a result, it is possible to prevent the premixing duct from being burned out and to provide a highly reliable gas turbine combustor 10.

  According to the embodiment described above, it is possible to prevent flame holding due to backfire in the premixing duct forming the premixed gas and to prevent burning of the premixed duct.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Gas turbine combustor, 20 ... Gas turbine casing, 21,153a ... Outer cylinder, 22 ... Combustor liner, 23 ... Combustion chamber, 24 ... Air passage, 25 ... Head plate, 26 ... Recirculation area, 30 ... Pilot Fuel injection unit 31 ... Diffusion combustion fuel injection unit 32 ... Premixed combustion fuel injection unit 33,34 ... Swirler 40 ... Premixing duct 41 ... Inlet 42,43,44 ... Branch, 42a, 43a, 44a ... outlet, 45 ... main flow path, 50 ... main fuel injection part, 51 ... fuel injection port, 150 ... gas turbine, 151 ... compressor, 152 ... turbine, 153 ... transition piece, 153b ... inner cylinder, AR ... Air, F ... fuel.

Claims (3)

A cylindrical combustor liner forming a combustion chamber;
A pilot fuel injection section provided in the center of the head of the combustor liner;
An inlet that opens toward the upstream side, and has a main flow path that extends along the axial direction of the combustor liner on the outer periphery of the combustor liner, and whose cross-sectional area decreases as it goes downstream A premixing duct for forming a premixed gas composed of fuel and air supplied to the combustion chamber;
A plurality of premixing ducts are provided along the axial direction of the combustor liner, and the outlet opening area increases as it is located downstream, and the premixed gas is branched from the main flow path and led to the combustion chamber. And a gas turbine combustor.   The outlet of the branch path located on the most upstream side is located immediately downstream of a recirculation region formed on the upstream side in the combustor liner during a combustion reaction. The gas turbine combustor as described. A compressor that draws air from the atmosphere into high-temperature and high-pressure air;
The gas turbine combustor according to claim 1, wherein fuel is burned using air from the compressor;
A gas turbine comprising: a turbine rotated by combustion gas generated by the gas turbine combustor.

Images