Clearance control system for a gas turbine

Abstract

In the clearance control system of a gas turbine, when the control device is in a load steady state where the variation range of the load changes within a preset range, the regulating device is operated in such a way that the first flow rate is greater than the second flow rate; when the control device is in a load variation state where the load is outside the range, the regulating device is operated in such a way that the second flow rate is greater than the first flow rate.

Description

Technical Field

[0001] The present disclosure relates to a clearance control system for a gas turbine.

[0002] This application claims priority based on Japanese Patent Application No. 2020-150225 filed with the Japan Patent Office on September 8, 2020, the content of which is incorporated herein by reference. Background Art

[0003] Patent Document 1 describes a gas turbine that reduces the clearance between the stationary side components and the rotating side components of a turbine by cooling a shroud ring during rated operation.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014-58979 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, in a state where the shroud ring is cooled during rated operation, there is a problem that it is impossible to cope with excessive clearance reduction caused by a sudden change in the load of the gas turbine.

[0009] In view of the above circumstances, an object of at least one embodiment of the present disclosure is to provide a clearance control system for a gas turbine that can cope with changes in the load of the gas turbine.

[0010] Means for Solving the Problems

[0011] To achieve the above object, in the clearance control system of a gas turbine according to the present disclosure, the gas turbine includes: a compressor that generates compressed air; a combustor that burns fuel using the compressed air; a turbine that is driven by combustion gas generated by combustion of the fuel in the combustor, and the clearance control system of the gas turbine controls the clearance between the stationary side components and the rotating side components of the turbine. Among them, the clearance control system of the gas turbine includes: a cooling passage formed in the stationary side component for the flow of a cooling medium for cooling the stationary side component; a combustor internal flow path that communicates with the cooling passage at a position downstream of the cooling passage in the flow direction of the cooling medium and is formed in the combustor; a supply device that supplies the cooling medium to at least one of the cooling passage and the combustor internal flow path; an adjustment device that adjusts the flow rate of the cooling medium flowing in the cooling passage, i.e., the first flow rate, and the flow rate of the cooling medium bypassing the cooling passage and flowing in the combustor internal flow path, i.e., the second flow rate; and a control device that detects the load of the gas turbine and operates the adjustment device based on the load. When the load is in a load stable state where the variation range of the load changes within a preset range, the control device operates the adjustment device such that the first flow rate is greater than the second flow rate. When the load is in a load variation state outside the range, the control device operates the adjustment device such that the second flow rate is greater than the first flow rate.

[0012] Advantages of the Invention

[0013] According to the clearance control system of the gas turbine of the present disclosure, in the case of a load variation of the gas turbine, excessive clearance reduction may occur. However, in such a case, since the cooling amount of the stationary side components of the turbine is reduced, it is possible to cope with the load variation of the gas turbine. Brief Description of the Drawings

[0014] Figure 1 is a schematic structural diagram of a clearance control system of a gas turbine according to an embodiment of the present disclosure.

[0015] Figure 2 is a diagram showing the structure inside the turbine of a gas turbine according to an embodiment of the present disclosure.

[0016] Figure 3 is a set of diagrams for explaining the operation of a clearance control system of a gas turbine according to an embodiment of the present disclosure.

[0017] Figure 4 is a diagram for explaining the load stable state in a gas turbine according to an embodiment of the present disclosure.

[0018] Figure 5A diagram showing a modified example of the operation of the clearance control system of a gas turbine for explaining an embodiment of the present disclosure.

[0019] Figure 6 A diagram for explaining another way of the load stable state in a gas turbine according to an embodiment of the present disclosure. Detailed implementation mode

[0020] Hereinafter, the clearance control system of the gas turbine according to the embodiment of the present disclosure will be described based on the drawings. This embodiment represents one way of the present disclosure and does not limit the disclosure, and can be arbitrarily changed within the scope of the technical idea of the present disclosure.

[0021] <Structure of the clearance control system of a gas turbine according to an embodiment of the present disclosure>

[0022] As Figure 1 shown, the gas turbine 1 includes: a combustor 4 that burns fuel to generate combustion gas; a compressor 2 that supplies compressed air as combustion air to the combustor 4; and a turbine 6 that has a rotating shaft 5 shared with the compressor 2 and is configured to be driven by the combustion gas generated by the combustor 4. A generator 7 is connected to the rotating shaft 5, and the generator 7 is configured to be driven by the output of the turbine 6.

[0023] As Figure 2 shown, in the turbine 6, a clearance, namely clearance 13, is formed between a stator vane ring 11 as a stationary-side component and a moving blade 12 as a rotating member. A cooling passage 21 through which a cooling medium described later flows is formed in the stator vane ring 11. By flowing the cooling medium through the cooling passage 21, the stator vane ring 11 is cooled. By changing the flow rate of the cooling medium flowing through the cooling passage 21 of the stator vane ring 11, the cooling amount of the stator vane ring 11 changes, and the size of the clearance 13 is controlled. Generally, if the cooling amount of the stator vane ring 11 is increased during the operation of the gas turbine 1, the clearance 13 becomes smaller, and if the cooling amount is decreased, the clearance 13 becomes larger.

[0024] As Figure 1 shown, the clearance control system 20 is used to control the clearance 13 by adjusting the cooling amount of the stator vane ring 11 (refer to Figure 2) size, having a cooling path 21, a burner internal flow path 22 formed in the burner 4, an external compressor 23 that extracts and boosts the air in the machine room 3 of the gas turbine 1 as a cooling medium, a supply path 24 with one end connected to the external compressor 23 and the other end branched into a first path 24a and a second path 24b respectively connected to the cooling path 21 and the burner internal flow path 22, flow control valves 25a and 25b respectively provided in the first path 24a and the second path 24b, and a control device 26. In the flow direction of the cooling medium flowing in the supply path 24, the cooling path 21 and the burner internal flow path 22 are communicated in such a way that the burner internal flow path 22 is located on the downstream side of the cooling path 21. The control device 26 is electrically connected to the generator 7 and the flow control valves 25a and 25b respectively. As will be described later, the flow control valves 25a and 25b respectively adjust the flow rate of the cooling medium flowing in the cooling path 21, i.e., the first flow rate, and the flow rate of the cooling medium bypassing the cooling path 21 and flowing in the burner internal flow path 22, i.e., the second flow rate. Therefore, they constitute the adjustment device 25.

[0025] <Operation of the gap control system of a gas turbine according to an embodiment of the present disclosure>

[0026] Next, the operation of the gap control system 20 according to an embodiment of the present disclosure will be described. As Figure 1 shown, when starting the gas turbine 1, the compressed air generated by the compressor 2 is supplied to the burner 4 to burn the fuel, generating combustion gas. The combustion gas is supplied to the turbine 6 to drive the turbine 6. The generator 7 is driven by the rotation of the rotating shaft 5 caused by the rotation of the turbine 6.

[0027] As Figure 3 shown in the graph (a) of, after starting the gas turbine 1, the rotational speed of the gas turbine 1 increases. If it becomes a no-load rated speed operation state at time t1, the generator 7 is connected to an unillustrated power system (load connection). After the load connection, the load of the gas turbine 1 increases and stabilizes at time t2. It should be noted that the load of the gas turbine 1 is detected by the control device 26 based on the power generation amount of the generator 7. In Figure 3 the graph (a) of, as the state where the load is stable after time t2, it is simply depicted by a horizontal straight line without load variation, but actually even in the state where the load is constant after time t2, the load varies within a certain range. For example, as Figure 4 shown, the load varies within the range defined by the first upper limit value L max-1 and the first lower limit value L min-1 . The moving average of such a varying load is shown as the load trend in Figure 3 the graph (a) of.

[0028] In this embodiment, if the load remains within the range of the first upper limit value L max-1 and the first lower limit value L min-1 for a specified time Δt, the control device 26 determines that the load of the gas turbine 1 is in a stable state (load stable state). In this embodiment, the specified time Δt is described as a fixed time preset in the control device 26.

[0029] As Figure 3 shown in graph (b) of max-1 if the load remains within the range of the first upper limit value L min-1 and the first lower limit value L during the period from time t2 until the elapse of the specified time Δt, that is, if the gas turbine 1 reaches a load stable state at time t3, the control device 26 starts the cooling of the shroud 11.

[0030] Next, the cooling operation of the shroud 11 will be described. As Figure 1 shown, the control device 26 fully closes the flow control valve 25a and fully opens the flow control valve 25b until the gas turbine 1 reaches a load stable state (until Figure 3 time t3 in Figure 2 ). The air in the machine room 3 of the gas turbine 1 extracted as the cooling medium is pressurized by the external compressor 23 and flows in the supply passage 24, but only flows in the second passage 24b and then flows in the burner internal flow path 22. In this case, the cooling medium bypasses the cooling passage 21 and does not flow in the cooling passage 21, so the shroud 11 (refer to

[0031] is not cooled.

[0032] As Figure 3 shown in graph (b) of max-1 when the cooling of the shroud 11 starts at time t3, the cooling of the shroud 11 continues as long as the gas turbine 1 is in a load stable state. During the operation of the gas turbine 1, the gas turbine 1 may sometimes change from a load stable state to a load variation state outside the range defined by the first upper limit value L min-1 of the load and the first lower limit value L within a specified time Δt. In Figure 3In Chart (b), as an example, a phenomenon of a significant reduction in load at time t4 is shown. If the gas turbine 1 is in a load change state, the control device 26 stops the cooling of the shroud 11.

[0033] At time t5, the reduction in load stops. If, in this state, the load remains within the above range during the period from time t5 to after a specified time Δt, that is, if the gas turbine 1 becomes in a load stable state at time t6, the control device 26 starts cooling the shroud 11 again. Then, similarly, if the gas turbine 1 becomes in a load change state at time t7, the control device 26 stops the cooling of the shroud 11. If the increase in load stops at time t8 and the gas turbine 1 becomes in a load stable state at time t9 in this state, the control device 26 starts cooling the shroud 11 again. Although not shown in Chart (b) of Figure 3 , such an operation continues during the operation of the gas turbine 1 thereafter.

[0034] If the load starts to decrease to stop the gas turbine 1 at time t 10 , the control device 26 stops the cooling of the shroud 11. If the load becomes zero at time t 11 and the generator 7 is disconnected from the power system, the gas turbine 1 is stopped.

[0035] <Effect of the clearance control system of the gas turbine according to an embodiment of the present disclosure>

[0036] As shown in Chart (c) of Figure 3 , if the shroud 11 is cooled, the clearance 13 (refer to Figure 2 ) becomes smaller, and if the cooling of the shroud 11 is stopped, the clearance 13 becomes larger. That is, according to the above operation of the clearance control system 20, the shroud 11 is cooled to reduce the clearance 13 when the gas turbine 1 is in a load stable state, and the cooling of the shroud 11 is stopped to increase the clearance 13 when the gas turbine 1 is in a load change state.

[0037] The clearance 13 is formed along the circumferential direction of the turbine 6. Therefore, Figure 3 what is shown in Chart (c) of

[0038] In the case where such elliptical deformation occurs, based on the load of the gas turbine 1, even if there is no problem with the average value of the clearance 13, there may be a portion where the clearance 13 is very small locally in the circumferential direction. Such elliptical deformation tends to occur when the gas turbine 1 is in a load-changing state and converges when the gas turbine 1 becomes a load-stable state. Therefore, in the case where the gas turbine 1 is in a load-changing state, the cooling of the vane ring 11 is stopped to increase the margin of the clearance 13, and in the case where the gas turbine 1 is in a load-stable state, the vane ring 11 is cooled to reduce the margin of the clearance 13, thereby being able to cope with the load change of the gas turbine 1.

[0039] In addition, elliptical deformation also occurs when the load of the gas turbine 1 decreases and when the load increases. However, the average clearance becomes larger when the load decreases, and on the other hand, the average clearance becomes smaller when the load increases. Therefore, when the load increases, not only elliptical deformation but also excessive clearance reduction occurs from the viewpoint of the average clearance. In such a case, by determining that the gas turbine 1 is in a load-changing state and stopping the cooling of the vane ring 11 to increase the margin of the clearance 13, it is also possible to cope with excessive clearance reduction.

[0040] In this way, in the case of a load change of the gas turbine 1, excessive reduction of the clearance 13 may occur. However, in such a case, since the cooling amount of the vane ring 11 of the turbine 6 is stopped or reduced, it is possible to cope with the load change of the gas turbine 1.

[0041] In this embodiment, as described above, when the operation of the gas turbine 1 is stopped, the load decreases, that is, it changes. However, since the cooling amount of the vane ring 11 is reduced from the start of the load decrease, it is also possible to cope with excessive reduction of the clearance 13 that occurs when the gas turbine 1 is stopped.

[0042] <Modification example of the clearance control system of the gas turbine according to an embodiment of the present disclosure>

[0043] In the above embodiment, the specified time Δt is a fixed time preset in the control device 26, but is not limited to this method. The control device 26 may also be based on the load relative to the first upper limit value L of the load max-1 and the first lower limit value L min-1 to determine the specified time Δt based on the value of the load changing within the defined range or the change amount of the load value when the load is in a changing state. Thereby, it is possible to more appropriately determine whether the gas turbine 1 has become a load-stable state, and thus it is possible to more appropriately cope with the load change of the gas turbine 1.

[0044] In the above embodiment, regardless of the value of the load, it is assumed that the load is within the range defined by the first upper limit value L of the load max-1 and the first lower limit value L min-1When it varies within the defined range, it is in a load stable state. When the load varies in a manner that deviates from this range during the specified time Δt, it is in a load variation state, but it is not limited to this manner. For example, it can also be as Figure 6 shown, a second upper limit value L of the load is preset max-2 (for example, 95%) and a second lower limit value L min-2 (for example, 80%). The control device 26 determines that it is in a load stable state when the load is equal to or higher than the second upper limit value L max-2 (during the period from time t2 to time t4), and determines that it is in a load variation state when the load is equal to or lower than the second lower limit value L min-2 (during the period from time t1 to time t 12 or after time t 13 ) and operates the flow control valves 25a and 25b regardless of the load variation amplitude. Thus, cooling is performed when the necessity of cooling the vane ring 11 is high based on the load value of the gas turbine 1, and cooling is not performed when the necessity of cooling the vane ring 11 is low, thereby simplifying the control of cooling the vane ring 11.

[0045] In the above-described embodiment, when in the load stable state, the cooling of the vane ring 11 is stopped. In this case, it becomes a state where the cooling medium does not flow in the cooling passage 21. If this state continues, drain accumulates in the cooling passage 21, and when the cooling medium flows in the cooling passage 21 again later, the drain is brought into the burner internal flow path 22. In order to suppress the accumulation of drain in the cooling passage 21, as Figure 5 shown, even when the cooling of the vane ring 11 is not performed, the cooling medium can be made to flow in the cooling passage 21 at a minimum flow rate such that the cooling of the vane ring 11 is minimized. That is, the flow control valve 25a can be slightly opened instead of being fully closed.

[0046] In addition, for a purpose different from suppressing the accumulation of drain in the cooling passage 21, the method of turning on and off the cooling of the vane ring 11 is not limited to being based on the load stable state and the load variation state. The cooling amount of the vane ring 11 can also be adjusted according to the load variation amplitude when transferring from the load stable state to the load variation state and when transferring from the load variation state to the load stable state. That is, the control device 26 can also determine the ratio of the first flow rate of the cooling medium flowing in the cooling passage 21 to the second flow rate of the cooling medium bypassing the cooling passage 21 and flowing in the burner internal flow path 22 according to the load variation amplitude, and operate the flow control valves 25a and 25b so as to obtain the first flow rate and the second flow rate based on this ratio. Thus, it is possible to more appropriately respond to the load variation of the gas turbine.

[0047] In the above-described embodiments, the load of the gas turbine 1 is directly detected based on the power generation amount of the generator 7, but the load of the gas turbine 1 may also be indirectly detected according to other indicators that can estimate the load. As such an indicator, for example, the opening degree of the inlet guide vane (IGV) for adjusting the intake air amount of the compressor 2 can be used.

[0048] In the above-described embodiments, the air extracted from the machine room 3 of the gas turbine 1 is used as the cooling medium, but the present invention is not limited to this method. A part of the compressed air compressed by the compressor 2 or any fluid supplied from the outside of the gas turbine 1 can be used as the cooling medium. Therefore, the supply device that supplies the cooling medium to at least one of the cooling passage 21 and the burner internal flow path 22 is not limited to the external compressor 23, and any device can be used according to the cooling medium used. Furthermore, the regulating device 25 is not limited to the flow regulating valves 25a and 25b, and for example, any device such as a three-way valve that can distribute the cooling fluid in two directions can be used.

[0049] The content described in each of the above embodiments is understood as follows, for example.

[0050] [1] In a clearance control system of a gas turbine according to one aspect, the gas turbine (1) includes: a compressor (2) that generates compressed air; a burner (4) that burns fuel using the compressed air; and a turbine (6) that is driven by combustion gas generated by the combustion of the fuel in the burner (4). The clearance control system (20) of the gas turbine (1) controls the clearance (13) between the stationary side member (stator vane ring 11) and the rotating side member (rotating blade 12) of the turbine (6), wherein,

[0051] The clearance control system (20) of the gas turbine (1) includes:

[0052] A cooling passage (21) formed in the stationary side member (11) through which a cooling medium for cooling the stationary side member (11) flows;

[0053] A burner internal flow path (22) that communicates with the cooling passage (21) at a position downstream of the cooling passage (21) in the flow direction of the cooling medium and is formed in the burner (4);

[0054] A supply device (external compressor 23) that supplies the cooling medium to at least one of the cooling passage (21) and the burner internal flow path (22);

[0055] A regulating device (25) that regulates the flow rate of the cooling medium flowing in the cooling passage (21), i.e., the first flow rate, and the flow rate of the cooling medium bypassing the cooling passage (21) and flowing in the burner internal flow path (22), i.e., the second flow rate; and

[0056] A control device (26) that detects the load of the gas turbine (1) and operates the regulating device (25) based on this load,

[0057] When the control device (26) is in a load stable state where the variation range of the load changes within a preset range, it operates the regulating device (25) such that the first flow rate is greater than the second flow rate. When it is in a load variation state where the load is outside the range, it operates the regulating device (25) such that the second flow rate is greater than the first flow rate.

[0058] According to the clearance control system of the gas turbine of the present disclosure, in the case of a load variation of the gas turbine, excessive clearance reduction may occur. However, in such a case, since the cooling amount of the stationary side components of the turbine is reduced, it is possible to cope with the load variation of the gas turbine.

[0059] [2] The clearance control system of the gas turbine of another aspect is based on the clearance control system of the gas turbine in [1],

[0060] When stopping the operation of the gas turbine (1), the control device (26) operates the regulating device (25) such that the second flow rate is greater than the first flow rate from the start of the load drop.

[0061] According to such a structure, when the load decreases during the stop of the gas turbine operation, i.e., there is a variation, but since the cooling amount of the stationary side components of the turbine is reduced from the start of the load drop, it is possible to cope with the clearance reduction that occurs during the stop of the gas turbine operation.

[0062] [3] The clearance control system of the gas turbine of yet another aspect is based on the clearance control system of the gas turbine in [1] or [2],

[0063] The control device (26) determines the ratio of the first flow rate to the second flow rate based on the load change amounts when transferring from the load stable state to the load variation state and when transferring from the load variation state to the load stable state, and operates the regulating device (25) such that the first flow rate and the second flow rate are based on this ratio.

[0064] According to such a structure, since the cooling amount of the stationary side components of the turbine is adjusted based on the load change amount, it is possible to more appropriately cope with the load change situation of the gas turbine.

[0065] [4] The clearance control system of the gas turbine according to yet another aspect is based on the clearance control system of the gas turbine in [1] or [2],

[0066] The upper limit value (second upper limit value L max-2 ) and the lower limit value (second lower limit value L min-2 ) of the load are preset, and when the load is equal to or higher than the upper limit value (L max-2 ), the control device (26) operates the adjusting device (25) as the load stable state, and when the load is equal to or lower than the lower limit value (L min-2 ), the control device (26) operates the adjusting device (25) as the load change state.

[0067] According to such a structure, cooling is performed when the necessity of cooling the stationary side components of the turbine is high based on the value of the load of the gas turbine, and cooling is not performed or the cooling amount is reduced when the necessity of cooling the stationary side components of the turbine is low, thereby simplifying the control of the cooling of the stationary side components of the turbine.

[0068] [5] The clearance control system of the gas turbine according to yet another aspect is based on the clearance control system of the gas turbine in [1] or [2],

[0069] The control device (26) determines that the load is in the stable state when the change range of the load has been within the range for a specified time, and the specified time is determined by the control device (26) based on the change amount of the load with respect to the load value that has changed within the range or the load value during the load change state.

[0070] According to such a structure, it is possible to more appropriately determine whether the gas turbine has entered the load stable state, and thus it is possible to more appropriately cope with the load change situation of the gas turbine.

[0071] [6] The clearance control system of the gas turbine according to yet another aspect is based on the clearance control system of the gas turbine in [1] or [2],

[0072] When the control device (26) operates the adjusting device (25) such that the second flow rate is greater than the first flow rate, the control device (26) operates the adjusting device (25) such that the first flow rate becomes zero.

[0073] According to such a structure, since the on / off control of the cooling of the stationary side components of the turbine is performed, the control of the cooling of the stationary side components of the turbine can be simplified.

[0074] Explanation of reference numerals:

[0075] 1 … Gas turbine;

[0076] 2 … Compressor;

[0077] 4 … Burner;

[0078] 6 … Turbine;

[0079] 11 … Vane ring (stationary side component);

[0080] 12 … Moving vane (rotating side component);

[0081] 13 … Clearance;

[0082] 20 … Clearance control system;

[0083] 21 … Cooling passage;

[0084] 22 … Inner flow path of burner;

[0085] 23 … External compressor (supply device);

[0086] 25 … Regulating device;

[0087] 26 … Control device.

Claims

1. A clearance control system for a gas turbine, the gas turbine comprising: a compressor that generates compressed air; a combustor , which uses the compressed air to combust fuel; and a turbine, which is driven by combustion gas generated by combustion of the fuel in the burner, wherein a clearance control system of the gas turbine controls a clearance between a stationary-side component and a rotating-side component of the turbine, where the clearance control system of the gas turbine includes: a cooling passage, which is formed in the stationary-side component and through which a cooling medium for cooling the stationary-side component flows; an in-burner flow path, which communicates with the cooling passage at a position downstream of the cooling passage in a flow direction of the cooling medium and is formed in the burner; a supply device, which supplies the cooling medium to at least one of the cooling passage and the in-burner flow path; a regulating device, which regulates a flow rate of the cooling medium flowing in the cooling passage, i.e., a first flow rate, and a flow rate of the cooling medium bypassing the cooling passage and flowing in the in-burner flow path, i.e., a second flow rate; and a control device, which detects a load of the gas turbine and operates the regulating device based on the load, wherein the control device operates the regulating device such that the first flow rate is greater than the second flow rate in a load stable state where a variation range of the load changes within a preset range, and operates the regulating device such that the second flow rate is greater than the first flow rate in a load variation state where the load is outside the range.

2. The clearance control system of the gas turbine according to claim 1, wherein when stopping operation of the gas turbine, the control device operates the regulating device such that the second flow rate is greater than the first flow rate from when the load starts to decrease.

3. The clearance control system of the gas turbine according to claim 1 or 2, wherein the control device determines a ratio between the first flow rate and the second flow rate based on a load change amount when transferring from the load stable state to the load variation state and when transferring from the load variation state to the load stable state, and operates the regulating device such that the first flow rate and the second flow rate are based on the ratio.

4. The clearance control system of the gas turbine according to claim 1 or 2, wherein an upper limit value and a lower limit value of the load are preset, and the control device operates the regulating device as the load stable state when the load is equal to or greater than the upper limit value, and operates the regulating device as the load variation state when the load is equal to or less than the lower limit value.

5. The clearance control system of the gas turbine according to claim 1 or 2, wherein the control device determines that the load is in the load stable state when the variation range of the load has changed within the range for a specified time, and the specified time is determined by the control device based on a change amount of the load with respect to a value of the load changing within the range or a value of the load in the load variation state.

6. The clearance control system of the gas turbine according to claim 1 or 2, wherein When the control device operates the adjustment device in such a manner that the second flow rate is greater than the first flow rate, the control device operates the adjustment device in such a manner that the first flow rate becomes zero.

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