JP2010054142A - Combustor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combustor capable of further reducing an NOx emission value. <P>SOLUTION: This combustor is provided with a burner comprising a fuel nozzle jetting fuel, a first air hole plate disposed at a downstream side in the fuel jetting direction with respect to the fuel nozzle, and comprising an air hole for supplying a fuel flow and an air flow to a combustion chamber at the downstream side, and a barrier disposed between the first air hole plate and the combustion chamber as a member independent from the first air hole plate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a combustor.

One of the power plants that support industrial power is a gas turbine power plant that uses fossil resources such as natural gas and oil as fuel. Since this gas turbine power plant uses fossil resources as fuel and emits carbon dioxide (CO ₂ ), which is one of the global warming substances, improvement in power generation efficiency is required more than ever. As means for increasing the power generation efficiency, there is an increase in the temperature of combustion gas in the gas turbine combustor. However, as the combustion gas becomes hot, nitrogen oxides (NOx), which are environmental inhibitors in the combustion exhaust gas, increase exponentially. Therefore, measures to reduce NOx while increasing power generation efficiency are important technical issues. It has become.

  Therefore, Patent Document 1 discloses a technique for reducing NOx by disposing a fuel nozzle on the upstream side of an air hole plate having air holes.

JP 2003-148734 A

  In Patent Document 1, an annular air flow wraps around the outer peripheral side of the fuel flow inside the air hole and flows downstream, and is ejected into the combustion chamber. Then, when the fuel flow is ejected into the combustion chamber, it can be rapidly mixed with the air flow.

  However, a high temperature portion is formed when a fuel rich region remains in the combustion chamber. Since NOx increases exponentially as the temperature rises, it is necessary to further improve the fuel dispersibility in the air so as not to form a local high temperature portion and to reduce the NOx emission value.

  An object of the present invention is to provide a combustor that can further reduce the NOx emission value.

  The present invention includes a fuel nozzle that ejects fuel, and a first air hole that is disposed downstream of the fuel nozzle in the fuel ejection direction and supplies a fuel flow and an air flow to a downstream combustion chamber. And a burner provided with the first air hole plate and an obstacle as a separate member between the first air hole plate and the combustion chamber.

  According to the present invention, a combustor that can further reduce the NOx emission value can be provided.

  Gas turbine combustors that use fossil resources as fuel aim to increase the temperature of combustion gases in order to increase power generation efficiency. As the combustion gas increases in temperature, nitrogen oxides (NOx), which are environmental inhibitors in the combustion exhaust gas, increase exponentially. Therefore, a countermeasure for reducing NOx while increasing power generation efficiency is an important technical issue.

  As a combustion method for reducing NOx, there is a premixed combustion method in which fuel and air concentrations are made uniform by premixing fuel and air to avoid local high temperatures. However, the premixed combustion method has a “backfire” related to reliability, that is, there is a possibility that the fire returns to the upstream side of the premixed gas and the combustor member is melted. As a structure for preventing such backfire, there is a combustor structure disclosed in Patent Document 1. In the combustor structure of Patent Document 1, a plurality of fuel nozzles and air holes are assembled, and an air hole for supplying an air flow around the fuel flow is disposed on the downstream side of the fuel nozzle for supplying a low flow rate fuel It is. The air holes are provided in the air hole plate and are provided in a plurality of rows in the radial direction of the plate.

  This combustor structure has a feature that the fuel flow flows through the center portion and the air flow flows around the fuel flow, so that it does not become a complete premixed gas inside the air hole and is difficult to backfire. In addition, by arranging a plurality of air holes, that is, by arranging a large number of air holes, the fuel sprayed from the air holes is dispersed in the air and the concentration distribution is flattened to reduce NOx. However, since it does not become a complete premixed gas in the air hole, a gas having a fuel and air concentration distribution is burned in the combustion chamber, and NOx may not easily decrease.

  Further, in the above-described combustor structure, a plurality of air holes are aggregated. However, at each merging point where air and fuel merge, the basic flow form is close to the diffusion system. For this reason, when a fuel-rich region is formed during combustion, the fuel-rich region becomes a high-temperature part. When the high temperature part is formed and the temperature rises, the NOx increases exponentially, so the fuel dispersibility in the air is increased so as not to form a local high temperature part, and the NOx emission value is reduced. is important.

  In addition, the NOx emission level required for new power plants in the future is a single-digit ppm concentration that is even lower. For this reason, while taking advantage of the above-described characteristic that there is no risk of flashback due to the structure of the combustor, it is necessary to promote the mixing of fuel and air equivalent to the premixed combustion method, and to further reduce NOx.

  Therefore, the present invention does not change the basic nozzle arrangement of the combustor structure, and the three features of the mixing mechanism, the mixing region, and the flame holding mechanism from the characteristics of the mixed flow mode of fuel and air ejected from the air holes. The function was shared. As a result, a more homogeneous mixed gas can be combusted more stably than before, and a low NOx reduction can be realized.

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 2B shows a cross section of the compressor 17 that supplies compressed air to the combustor, the turbine 18 that is rotationally driven by the combustion gas discharged from the combustor, and the combustor. In FIG. 2B, the air 19 sent from the compressor 17 passes between the outer cylinder 22 and the combustor liner 21. A part of the air 19 flows into the combustion chamber 15 as the cooling air 20 of the combustor liner 21. The remainder of the air 19 passes through the air supply hole 29 and is guided to the downstream combustion chamber 15 side as the combustion air 8 via the air hole 5.

  In this embodiment, the fuel 7 and the fuel 7a are branched and supplied from a fuel supply system 23 having a control valve 23a. That is, the fuel supply system 23 is branched into two parts, a first fuel supply system 24 and a second fuel supply system 25. The first fuel supply system 24 and the second fuel supply system 25 are each provided with a control valve 24a and a control valve 25a that can be individually controlled independently. The control valve 24a and the control valve 25a are configured to independently control the respective fuel flow rates according to the load of the gas turbine. Here, the control valve 24a can control the flow rate of the surrounding fuel nozzle group, and the control valve 25a can control the flow rate of the central fuel nozzle group. In this embodiment, the fuel nozzle group is divided into a plurality of fuel nozzle groups in the central portion and the surrounding fuel nozzle groups, and corresponding fuel supply systems are provided so that the fuel flow rate can be controlled independently.

  The fuel 7 that has flowed down the first fuel supply system 24 flows through the fuel supply pipe 2 in the combustor. The fuel 7 that has flowed through the fuel supply pipe 2 is distributed and supplied to the plurality of fuel nozzles 4 through the fuel distributor 3. Similarly, the fuel 7a flowing down the second fuel supply system 25 is also distributed and supplied to a plurality of fuel nozzles 28 via a fuel distributor 27 from a fuel supply pipe 26 in the combustor. The fuel nozzle 4 and the fuel nozzle 28 are arranged so as to be paired with the air hole 5 provided in the first air hole plate 10. The fuel 7 and the fuel 7a flow from the injection holes such as the fuel nozzle 4 and the fuel nozzle 28 through the air hole 15 and flow into the mixing promoting space 6 as a jet substantially coaxial with the combustion air. The mixing promoting space 6 is surrounded by the partition wall 1 on the outer peripheral side for each burner. Further, an obstacle that partitions the mixing promotion space 6 and the combustion chamber 15 is provided on the downstream side of the first air hole plate 10. This obstacle corresponds to the second air hole plate 11 in FIG. The second air hole plate 11 is provided with a plurality of air holes, and the fuel flow and the air flow are guided to the combustion chamber 15 side via the second air hole plate 11 to form a flame. 2A is a front view of a multi-burner in which a plurality of burners are arranged, and seven burners 40 are arranged on a plane to constitute a combustor. The generated high-temperature combustion gas enters the turbine 18 to work and is exhausted.

  FIG. 1 is a view focusing on one burner 40 arranged on the outer periphery of a combustor to which the present invention is applied. For the sake of simplicity, FIG. 1 shows a plan view (A1-A1 cross section, A2-A2 cross section) and a flow direction cross section (axial cross section) of a burner having 30 air holes. Here, the basic shape of the air hole is circular, but shapes other than circular may also be established.

  FIGS. 1A and 1B are views of two air hole plates viewed from the downstream side, and FIG. 1C is a cross-sectional view of the burner cut along the burner axis. Inside the burner 40, a first air hole plate 10 is disposed downstream of the fuel nozzle 4 in the fuel ejection direction, and a plurality of pairs of fuel nozzles 4 and air holes 5 are provided in the radial direction of the first air hole plate 10. It is arranged. Further, a fuel flow / air flow which is a separate member from the first air hole plate 10 and is ejected from the air hole 5 directly flows into the combustion chamber 15 at a downstream position spaced apart from the first air hole plate 10. There are obstacles to prevent this. Since this obstacle is provided between the first air hole plate 10 and the combustion chamber 15, the fuel flow / air flow ejected from the air hole 5 is prevented from flowing directly into the combustion chamber 15. Depending on the object, it is possible to further mix the fuel flow and air flow. Therefore, it is possible to burn the mixed gas 13 having a more homogeneous fuel concentration than that of Patent Document 1, and to achieve low NOx.

  Next, the flow state of the fuel flow / air flow in the first air hole plate and the second air hole plate will be described. The combustion air 8 supplied from the air supply hole 29 in FIG. 2 flows into the space around the fuel nozzle 4 and then flows into the air hole 5. On the other hand, the fuel 7 is discharged from the fuel nozzle 4 via the fuel distributor 3 from the fuel supply pipe 2. The fuel 7 discharged from the fuel nozzle 4 merges with the combustion air 8 at the inlet of the first air hole plate 10 and flows into the air holes 5. Combustion air 8 and fuel 7 are mixed by a vortex formed downstream of the end face of fuel nozzle 4 by flowing into air hole 5 in a narrow space. The fuel 7 flows out into the mixing promotion space 6 wider than the air hole 5, so that the fuel is diffused into the combustion air.

  As shown in FIG. 1, the mixed gas 13 that has exited the first air hole plate 10 and entered the mixing promotion space 6 subsequently burns through the air holes 12 and 14 provided in the second air hole plate 11. It flows into the chamber 15. The air holes 12 are air holes in the first and second rows from the burner center, and the air holes 14 are air holes in the third row from the burner center. Then, the mixed gas 13 in the combustion chamber 15 is ignited by an ignition device (not shown), and a flame with a more uniform temperature is formed, thereby reducing the amount of NOx generated.

  Here, the minimum distance L necessary for mixing the fuel 7 and the combustion air 8 shown in FIG. 1 is a distance at which mixing is promoted by the vortex breakdown of the jet. As a result of the unsteady turbulent flow analysis for this “mixing promotion distance”, the mixing by vortex breakdown rapidly proceeds 20 mm downstream from the outlet of the air hole 5 with respect to the single hole diameter φ8 mm of the air hole 5. I understood. Therefore, the distance between the outlet end face of the air hole 5 and the inlet end face of the second air hole plate 11 (that is, the distance between the first air hole plate 10 and the obstacle) is equal to the single hole diameter of the air hole 5. It is preferably 2.5 times (= 20 mm / 8 mm) or more. However, while the mixing promotion is possible by taking a long “mixing promotion distance”, the total length of the combustor becomes long. Therefore, the maximum value of the interval can be obtained from the total length of the combustor allowed in design. As described above, in this embodiment, after the fuel 7 and the combustion air 8 are merged inside the air hole 5, the mixing is promoted by staying in the mixing promoting space 6 for a distance L at which vortex breakdown starts.

  The mixed gas 13 after the mixing is promoted is swirled to form a stable flame in the combustion chamber 15 by the second air hole plate 11 provided with the air holes 12 having a swirl angle for stabilizing the combustion. To do.

  As shown in the A1-A1 sectional view and the A2-A2 sectional view of FIG. 1, the basic function of the air holes 5 of the first air hole plate 10 is to join the fuel 7 and the combustion air 8 together. There is no need to turn (because of course turning). In addition, the air holes of the second air hole plate 11 swirl the mixed gas 13 mixed in the mixing promotion space 6 to stabilize the formation of the flame. A turning angle is provided in the air holes 12 in the second row. Specifically, among the air holes 12, the turning angle in the first row on the inner circumferential side is such that the axis of the air holes is inclined toward the axial center of the burner. The turning angle in the second row on the inner circumferential side is such that the axis of the air hole is inclined in the axial center direction of the burner and is inclined in the circumferential direction with respect to the axial center of the burner. Thus, by inclining the axis of the air hole 12 with respect to the burner central axis, the mixed gas 13 intersects immediately after the mixed gas 13 exits the air hole 12, and a triangular pyramid shape with a vortex inside is obtained. After passing through the flow form, a substantially conical flow form is created by the twisting action of the fluid. This conical flow has a flame holding function by a swirling flow caused by its internal twisting action and a central flow pressure that is reduced by a rapid expansion action of the flow to form a circulating flow.

  In the present embodiment, the twelve air holes 12 (first and second rows on the burner inner peripheral side) located in the center portion of the second air hole plate 11 are swivel holes. The same effect can be obtained when the air holes 14 in the row are also configured as swirl holes.

  In this embodiment, the mixed gas 13 after the mixing of the fuel 7 and the combustion air 8 is sufficiently promoted by the first air hole plate 10 and the mixing promotion space 6 is transferred from the second air hole plate 11 to the combustion chamber 15. Since the gas is guided and burned, it is possible to burn the mixed gas 13 having a more uniform fuel concentration as compared with Patent Document 1, and to achieve low NOx. Further, in the present embodiment, since the mixed gas having a more homogeneous fuel concentration is burned, there is little flame temperature unevenness, the thermal reliability of the metal member used can be improved, and the first air in which no flame is formed nearby. There is also an effect that the hole plate 10 can be made of an inexpensive material having lower heat resistance than the conventional one.

  FIG. 3 is an axial sectional view and a radial sectional view of the burner 40 in the second embodiment. The configuration and operation of parts different from the first embodiment will be described. The difference in configuration is that the second air hole plate 11 is provided with swirl vanes 30 instead of a total of 30 air holes consisting of air holes 12 and 14. That is, the second air hole plate 11 of the first embodiment is replaced with a swivel plate. Specifically, a circular spacer 31 is provided in the central axis portion of the burner 40, and 16 rectangular beams 16 are bridged in the radial direction between the circular spacer 31 and the partition wall 1 of the burner 40, and the 16 A feature is that a swirling wing 30 is provided on each upstream side of the rectangular beam 16. The BB cross-sectional view of FIG. 3A shows the swirl vane 30 that swivels clockwise, but the same effect can be obtained even in the counterclockwise direction.

  The mixed gas 13 of the fuel 7 and the combustion air 8 mixed in the mixing promotion space 6 obtains a rotational force by passing through the swirl vanes 30. Further, the mixed gas 13 flows into the combustion chamber 15 through the gaps between the plurality of rectangular beams 16. The circular spacer 31 provided in the central shaft portion of the swirl plate has a certain cross-sectional area, and the circulation flow in the combustion chamber 15 formed by the swirl flow of the mixed gas 13 is received by the central shaft portion to stabilize combustion. There is a function to make it. The rectangular beam 16 also has an effect of stabilizing the combustion of the mixed gas 13 by the vortex formed on the downstream side.

  The present embodiment has the following effects compared to the embodiment of FIG. First, the swirl plate of the present embodiment can form a stronger swirl flow in the flow of the mixed gas 13 in the combustion chamber 15, and can further reduce NOx by further promoting the mixing. Secondly, since the axial circulation flow formed in the combustion chamber 15 is also strengthened by the swirl force of the entire mixed gas 13, the combustion stability can be improved. Thirdly, according to the swivel plate structure, since it is connected to all the rectangular beams 16 via the circular spacer 31, it is formed by connecting the flames, and the combustion stability can be improved.

  Also in this embodiment, since the mixed gas having a more uniform fuel concentration is burned in the combustor structure of FIG. 3, there is little unevenness in the flame temperature, and the thermal reliability of the metal member used can be improved. In addition, there is an effect that the first air hole plate 10 in which the flame is not formed nearby can be made of an inexpensive material having lower heat resistance than the conventional one.

  FIG. 4 is an axial sectional view and a radial sectional view of the burner 40 in the third embodiment. The configuration and operation of parts different from the first embodiment will be described. The difference in configuration is that the second air hole plate 11 is provided with a central bluff body 32 and an outer peripheral bluff body 33 which are obstacles in the fluid in place of a total of 30 air holes 12 and 14. . Specifically, a circular central bluff body 32 is provided at the central axis portion of the burner, and a ring-shaped outer peripheral bluff body 33 is arranged at a certain distance from the central bluff body 32, and both bluff bodies are arranged. 32 and 33 are attached to the partition wall of the burner by a support stay 34.

  In the CC sectional view and the axial sectional view of FIG. 4, both the bluff bodies 32 and 33 are placed on the cross support stay 34, and the end surfaces of both the bluff bodies 32 and 33 are flush with the combustion chamber 15. The arrangement arranged as shown is shown. Both the bluff bodies 32 and 33 have a triangular cross section in the axial direction. Note that the end faces of both the bluff bodies 32 and 33 are not necessarily the same plane, and the cross-sectional shapes of both the bluff bodies 32 and 33 may be streamlined. The mixed gas 13 of the fuel 7 and the combustion air 8 mixed in the mixing promotion space 6 flows along the sharp bluff bodies 32 and 33 immediately after passing through the support stay 34 and flows into the combustion chamber 15. The mixed gas 13 that has flowed along both the sharp-shaped bluff bodies 32 and 33 is stirred while being caught in a vortex formed in the wake of both the bluff bodies 32 and 33 immediately after passing through both the bluff bodies 32 and 33. .

  Combustion stability is improved by the wake vortex of both the bluff bodies 32 and 33. Further, since both the bluff bodies 32 and 33 are connected by the support stay, the hot spots of the metal member are alleviated and the reliability is improved.

  The present embodiment has the following effects compared to the embodiment of FIG. Firstly, the vortex steadily and stably can be formed by both the bluff bodies 32 and 33 which are obstacles in the fluid, and the flame holding property is improved. Secondly, since it is easy to change the cross-sectional area of the flow path of the combustor depending on the area of each end face of both the bluff bodies 32 and 33, there is an advantage that it is easy to cope structurally when changing the pressure loss of the combustor. is there. Further, since the flow in the combustion chamber 15 is less complicated than in the case of FIG. 1, there is an advantage that it is easy to cope with an unstable phenomenon such as combustion vibration.

  Also in this embodiment, since the flame does not adhere to the first air hole plate 10 by the combustor structure of FIG. 4, the temperature rise of the first air hole plate 10 can be suppressed and the reliability can be improved. An inexpensive material with low heat resistance can be used for the one air hole plate 10.

  FIG. 5 is an axial sectional view and a radial sectional view of the burner in the fourth embodiment. The configuration and operation of parts different from the first embodiment will be described. The difference in configuration is that the second air hole plate 11 is provided with a lattice-type plate 35 in place of 30 air holes 12 and 14 in total. Specifically, a metal plate having rectangular air holes 36 arranged at regular intervals is attached to the partition wall of the burner. In the DD cross-sectional view and the axial cross-sectional view of FIG. 5, the arrangement of the pointed and line symmetric as the arrangement of the rectangular air holes 36 is shown. In this case, the mixed gas 13 is evenly distributed to the space of the combustion chamber 15. The mixed gas 13 of the fuel 7 and the combustion air 8 mixed in the mixing promotion space 6 passes through the rectangular air holes 36 of the lattice plate 35 and then flows into the combustion chamber 15. The flow velocity at the corner portion of the rectangular air hole 36 becomes slower than that at the central portion, and the mixed gas 13 immediately after exiting the rectangular air hole 36 creates a vortex at the closed portion of the lattice plate 35 and contributes to combustion stability. Form a flow. Since the rectangular air holes 36 can be evenly arranged in the vertical and horizontal directions, the lattice plate 35 has the effect of increasing the thermal reliability by equalizing the flame and equalizing the heat load on the metal member.

  The present embodiment has the following effects compared to the embodiment of FIG. First, due to its shape characteristics, it has a high degree of freedom in the arrangement and arrangement of the rectangular air holes, it becomes possible to control the flame shape, and it is easy to design the heat load of the metal member. Secondly, since it is easy to change the cross-sectional area of the air holes depending on the size and number of the rectangular air holes, there is an advantage that the structure can be easily handled when the pressure loss of the combustor is changed. Thirdly, since the lattice-type plate having no swivel angle is easy to manufacture with a casting, there is an advantage that the cost can be reduced.

  Also in the present embodiment, the flame does not adhere to the first air hole plate 10 by the combustor structure of FIG. 5, so that the temperature rise of the first air hole plate 10 can be suppressed and the reliability can be improved. An inexpensive material with low heat resistance can be used for the one air hole plate 10.

It is the structure figure (Example 1) which showed the Example of the combustor. It is the figure which showed the combustor cross section and the system of a compressor and a turbine. It is the structure figure (Example 2) which showed another Example of the combustor. It is the structure figure (Example 3) which showed another Example of the combustor. It is the structure figure (Example 4) which showed another Example of the combustor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Partition 2, 26 Fuel supply pipe 3, 27 Fuel distributor 4, 28 Fuel nozzle 5, 12, 14 Air hole 6 Mixing promotion space 7, 7a Fuel 8, 19 Air 10 1st air hole plate 11 2nd air Hole plate 13 Gas mixture 15 Combustion chamber 16 Rectangular beam 17 Compressor 18 Turbine 20 Cooling air 21 Combustor liner 22 Outer cylinder 23 Fuel supply system 24 First fuel supply system 25 Second fuel supply systems 23a, 24a, 25a Control Valve 29 Air supply hole 30 Swivel blade 31 Circular spacer 32 Central bluff body 33 Outer peripheral bluff body 34 Support stay 35 Grid plate 36 Rectangular air hole

Claims (7)

A fuel nozzle for ejecting fuel;
A first air hole plate that is disposed downstream of the fuel nozzle in the fuel ejection direction and includes air holes for supplying a fuel flow and an air flow to a downstream combustion chamber;
A combustor provided with a burner provided with the first air hole plate and an obstacle as a separate member between the first air hole plate and the combustion chamber. A combustor according to claim 1,
The combustor, wherein a distance between the first air hole plate and the obstacle is at least 2.5 times a diameter of the air hole. The combustor according to claim 1 or 2, wherein
The obstacle is constituted by a second air hole plate provided with air holes,
A combustor, wherein an axis of an air hole provided in the second air hole plate is inclined in a circumferential direction with respect to an axial center of the combustor. The combustor according to claim 1 or 2, wherein
The obstacle is constituted by a second air hole plate provided with air holes,
A combustor, wherein an axis of an air hole provided in the second air hole plate is inclined toward an axial center of the combustor. The combustor according to claim 1 or 2, wherein
The combustor characterized in that the obstacle is constituted by swirl feathers. The combustor according to claim 1 or 2, wherein
The combustor characterized in that the obstacle is constituted by an obstruction (bluff body) in a flow path. The combustor according to claim 1 or 2, wherein
The combustor is characterized in that the obstacle is constituted by a lattice plate.

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