Method for starting gas turbine

Abstract

To prevent surging in a compressor while reducing the occurrence of contact between a stationary side member and a rotation side member during starting.SOLUTION: Based on the state of a gas turbine, either a normal start mode or a hot start mode is selected as a start mode. When startup control is started based on the start mode, the rotational speed of the gas turbine gradually increases. In a low rotational speed region, the opening degree of an inlet guide vane provided by a compressor is maintained at a first opening degree, and the opening degree of a bleed valve is maintained at second opening degree. In a high rotational speed region, the opening degree of the inlet guide vane is controlled to a first intermediate opening degree greater than the first opening degree, and the opening degree of the bleed valve is controlled to a second intermediate opening degree less than the second opening degree. The first intermediate opening degree is set to be larger in the hot start mode than that in the normal start mode. The second intermediate opening degree is set to be larger in the hot start mode than that in the normal start mode.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a gas turbine start-up method. [Background technology]

[0002] In a gas turbine, fuel supplied from a fuel supply system is mixed with combustion air and combusted to generate combustion gas, which is then used to drive the turbine. The combustion air used to generate the combustion gas is generated by a compressor included in the gas turbine. In particular, some gas turbines are equipped with inlet guide vanes (IGVs) at the inlet of the compressor to vary the intake air flow rate by adjusting the opening of the vanes, and have a bleed valve downstream of the inlet guide vanes to bleed a portion of the compressed air generated by the compressor to the outside.

[0003] Patent Document 1, for example, describes a technique for starting up this type of gas turbine. In this document, when a gas turbine that is stopped is driven by a startup motor, the opening of the inlet guide vane is set to a predetermined opening, and the opening of the bleed valve is set to a relatively large opening, thereby discharging most of the compressed air to the outside as bleed air at a low rotation speed during the initial startup period. Then, when the rotation speed has increased sufficiently, the opening of the bleed valve is reduced to fully closed, and steady operation is entered. This document particularly proposes that the bleed valve can be continuously adjusted, not just opened and closed, so that the bleed valve can be set to a predetermined intermediate opening during the low rotation speed during the initial startup period. This reduces the amount of compressed air wasted as bleed air during startup compared to when the bleed valve is fully open, thereby improving gas turbine efficiency and avoiding fluid instability during startup.

[0004] Here, there is a difference in heat capacity between the rotating and stationary components of the compressor. Typically, the rotating components have a larger heat capacity than the stationary components, so after a gas turbine is shut down, the rotating components are slower to cool than the stationary components. Therefore, when restarting a gas turbine from a hot state, which is a relatively short time since the previous shutdown, the rotating components are in a state of thermal expansion compared to the stationary components, narrowing the clearance between the two and creating a risk of contact. For this reason, measures are usually taken, such as setting a startup prohibition time until this condition is alleviated, or increasing the set clearance in the first place. However, the former restricts the use of the gas turbine, while the latter reduces efficiency.

[0005] In response to this issue, Patent Document 2 proposes temporarily increasing the opening of the inlet guide vanes during gas turbine startup to increase the intake air flow rate and pressure ratio in the compressor. This increases the temperature of the compressed air passing through the compressor's flow path, mitigating cooling of the stationary and rotating components of the compressor located adjacent to the flow path and promoting heating during startup. As a result, the clearance between the stationary and rotating components is more likely to return to an appropriate value, preventing contact between the stationary and rotating components. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-291449 [Patent Document 2] Japanese Patent Publication No. 2022-30038 Summary of the Invention [Problem to be solved by the invention]

[0007] In Patent Document 2, the opening of the inlet guide vane is controlled to be temporarily increased in order to avoid contact between the stationary-side member and the rotating-side member during startup. This temporary increase in the opening of the inlet guide vane is performed at a stage in the startup sequence where the gas turbine rotation speed gradually increases, when the rotation speed reaches a relatively high range. In this rotation speed range, the opening of the aforementioned bleed valve is controlled to be small. Therefore, if the opening of the inlet guide vane is increased as in Patent Document 2, the load on the front stages of the compressor increases, causing aerodynamic instability and the possibility of surging.

[0008] At least one embodiment of the present disclosure has been made in consideration of the above-described circumstances, and an object of the present disclosure is to provide a gas turbine start-up method that can effectively prevent surging in the compressor while suppressing contact between a stationary-side member and a rotating-side member during start-up. [Means for solving the problem]

[0009] In order to solve the above problem, a gas turbine start-up method according to at least one embodiment of the present disclosure includes: selecting one of a normal start mode and a hot start mode as a start mode based on a state of the gas turbine; gradually increasing the rotation speed of the gas turbine by starting startup control based on the startup mode; maintaining an opening degree of an inlet guide vane provided in a compressor of the gas turbine at a first opening degree and maintaining an opening degree of a bleed valve provided in the compressor downstream of the inlet guide vane at a second opening degree in a low rotation speed region where the rotation speed of the gas turbine is lower than a first rotation speed; in a high rotation speed region including a second rotation speed higher than the first rotation speed, controlling an opening degree of the inlet guide vane to a first intermediate opening degree larger than the first opening degree, and controlling an opening degree of the bleed valve to a second intermediate opening degree smaller than the second opening degree; Equipped with the first intermediate opening degree is set so that a value thereof when the hot start-up mode is selected as the start-up mode is larger than a value thereof when the normal start-up mode is selected as the start-up mode, The second intermediate opening degree is set so that the value when the hot start-up mode is selected as the start-up mode is larger than the value when the normal start-up mode is selected as the start-up mode. [Effects of the Invention]

[0010] According to at least one embodiment of the present disclosure, it is possible to provide a gas turbine start-up method that can suitably prevent surging in the compressor while suppressing contact between a stationary-side member and a rotating-side member during start-up. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating a schematic configuration of a gas turbine according to an embodiment. [Figure 2] 2 is a flowchart illustrating a method for starting the gas turbine of FIG. 1. [Figure 3] 3 is a time chart showing changes in opening degree of the inlet guide vane and the bleed valve with respect to the rotation speed when the normal start-up mode is selected in step S1 of FIG. 2. [Figure 4] 3 is a time chart showing changes in opening degree of the inlet guide vane and the bleed valve with respect to the rotation speed when the hot start mode is selected in step S1 of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the configurations described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure.

[0013] First, the overall configuration of a gas turbine 1 to which a gas turbine start-up method according to at least one embodiment of the present disclosure is applied will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing a general configuration of a gas turbine 1 according to one embodiment.

[0014] The gas turbine 1 includes a compressor 2 for generating compressed air as combustion air, a combustor 4 for generating combustion gas by mixing fuel with the combustion air and burning it, and a turbine 6 that has a rotating shaft 5 in common with the compressor 2 and can be driven by the combustion gas generated in the combustor 4. A generator 7 is connected to the rotating shaft 5, and can generate electricity by being driven by the output of the turbine 6. The generator 7 is electrically connected to an electric power grid 8, and the electric power generated by the generator 7 can be supplied to the electric power grid 8.

[0015] An inlet guide vane (IGV) 3A for adjusting the intake air volume is provided at the inlet of the compressor 2. The opening degree of the inlet guide vane 3A can be adjusted by an actuator 3B. In addition, a bleed valve 9A is provided in the compressor 2 downstream of the inlet guide vane 3A, so that a portion of the compressed air generated by the compressor 2 can be bled. The opening degree of the bleed valve 9A can be adjusted by an actuator 9B.

[0016] Next, we will explain the start-up method of the gas turbine 1 having the above configuration. Figure 2 is a flowchart showing the start-up method of the gas turbine 1 of Figure 1, and Figure 3 is a time chart showing changes in the opening degrees of the inlet guide vane 3A and the bleed valve 9A relative to the rotational speed when the normal start-up mode is selected in step S1 of Figure 2, and a time chart showing changes in the opening degrees of the inlet guide vane 3A and the bleed valve 9A relative to the rotational speed when the hot start mode is selected in step S1 of Figure 2.

[0017] First, when the start switch of the gas turbine 1 is turned ON, a start mode is selected (step S1) based on the state of the gas turbine 1. In step S1, either a normal start mode for starting the gas turbine 1 that is stopped in a cold state, or a hot start mode for starting the gas turbine 1 that is stopped in a state where at least a part of the gas turbine 1 is warmer than the cold state (hot state) can be selected as the start mode.

[0018] The selection of such a start-up mode can be made based on the state of the gas turbine 1. Specifically, the selection of the start-up mode can be made based on whether at least some of the components of the gas turbine 1 are warmed up. In this case, the components of the gas turbine 1 whose warm-up status is to be determined may be rotating components (e.g., the rotor) of the compressor 2 of the gas turbine 1, or stationary components (e.g., the compressor casing surrounding the rotor). The temperatures of these components may be directly measured temperatures, or may be estimated values ​​calculated based on various parameters related to the operating state of the gas turbine 1 (e.g., the casing temperature and cavity temperature of the compressor 2). In selecting the start-up mode, these temperatures are compared with preset thresholds. If the temperatures are below the thresholds, the normal start-up mode is selected as the start-up mode. If the temperatures are equal to or above the thresholds, the hot start-up mode is selected as the start-up mode.

[0019] In another embodiment, whether at least some of the components of the gas turbine 1 are warmed up may be determined based on the time elapsed since the gas turbine 1 was last shut down. In this case, although it is not possible to directly measure the temperatures of at least some of the components of the compressor 2, it is possible to simply evaluate whether at least some of the components of the compressor 2 are warmed up based on the time elapsed since the last shut down. The time elapsed since the last shut down is measured, for example, by a timer, and the measurement result is compared with a preset threshold value to become the criterion for selecting the start-up mode. That is, if the elapsed time is equal to or greater than the threshold value, the normal start-up mode is selected as the start-up mode, and if the elapsed time is equal to or greater than the threshold value, the hot start-up mode is selected as the start-up mode.

[0020] Next, the gas turbine 1 performs startup control in accordance with the startup mode selected in step S1 (step S2). When the startup control is performed, the rotation speed R of the gas turbine 1 is controlled so as to gradually increase over time.

[0021] In the initial stage (low rotation speed region) when the rotation speed R is relatively low after the start-up control is initiated, the opening of the inlet guide vane 3A is maintained at a relatively small first opening V1, and the opening of the bleed valve 9A is maintained at a relatively large second opening V2 (step S3). At start-up, the gas turbine 1, which is in a stopped state, is driven by the generator 7 as an electric motor to apply torque, thereby starting the start-up control. Thereafter, when the rotation speed R increases to a certain level, the turbine is driven using combustion gas generated by combustion in the combustor 4. In the low rotation speed region where the rotation speed R is relatively small, by maintaining the opening of the bleed valve 9A at the relatively large second opening V2, it is possible to suitably avoid the fluid instability phenomenon that is likely to occur in the compressor 2 when the rotation speed is low in such an initial stage of startup.

[0022] As shown in FIGS. 3 and 4, the first opening degree V1 at which the opening degree of the inlet guide vane 3A is maintained in the low rotation speed region, and the second opening degree V2 at which the opening degree of the bleed valve 9A is set, are set as common target opening degrees regardless of whether the start-up mode is the normal start-up mode or the hot start-up mode.

[0023] The first opening degree V1 of the inlet guide vane 3A in step S3 may be 0% (fully closed state). The second opening degree V2 of the bleed valve 9A in step S3 may be 100% (fully open state). Such opening degree control of the inlet guide vane 3A and the bleed valve 9A can be realized by transmitting control signals to the actuator 3B corresponding to the inlet guide vane 3A and the actuator 9B corresponding to the bleed valve 9A, respectively.

[0024] When the rotation speed R further increases and becomes greater than the first rotation speed R1 (step S4: YES), the opening of the inlet guide vane 3A is monotonically increased in proportion to the rotation speed R, and the bleed valve 9A is maintained at the second intermediate opening VM2 (step S5). The second intermediate opening VM2 is an intermediate opening between the fully closed state (0%) and the fully open state (100%). In this manner, in a high rotation speed region where the rotation speed R is greater than the first rotation speed R1, increasing the opening of the inlet guide vane 3A increases the intake air flow rate and pressure ratio in the compressor 2, thereby increasing the temperature of the compressed air passing through the flow path from the compressor 2 to the combustor 4 and promoting heating during startup. This effectively prevents contact between the stationary side member and the rotating side member during restart.

[0025] The first rotation speed R1 is, for example, 65 to 75% of the rated rotation speed.

[0026] When the rotation speed R further increases and becomes larger than the second rotation speed R2 (step S6: YES), the opening degree of the inlet guide vane 3A is maintained at the first intermediate opening degree VM1 (step S7). The first intermediate opening degree VM1 is an intermediate opening degree between the fully closed state (0%) and the fully open state (opening degree 100%). At this time, the opening degree of the extraction valve 9A is maintained at the second intermediate opening degree VM2 as in the above-mentioned step S5.

[0027] The second rotation speed R2 is, for example, 85 to 95% of the rated rotation speed.

[0028] When the rotation speed R further increases and becomes larger than the third opening degree R3 (step S8: YES), the opening degree of the inlet guide vane 3A is maintained at the first intermediate opening degree VM1 as in the above-mentioned step S7, while the opening degree of the extraction valve 9A is controlled to a fully closed state (0% opening degree) (step S9). Then, when the rotation speed R reaches the fourth rotation speed R4 (rated rotation speed) (step S10: YES), a series of startup controls is completed (step S11). As a result, the gas turbine 1 enters a no-load rated speed operating state, and thereafter the generator 7 is connected to the power grid 8.

[0029] 3 and 4, in the high rotation speed range where the rotation speed R is higher than the first rotation speed R1 during the series of startup controls described above, the first intermediate opening VM1 and the second intermediate opening VM2 are set to larger values ​​in the hot start mode than in the normal start mode. Specifically, by setting the first intermediate opening VM1-H in the hot start mode larger than the first intermediate opening VM1-S in the normal start mode, the intake air flow rate and pressure ratio of the compressor 2 are increased and contact between the stationary-side member and the rotating-side member during startup is more effectively suppressed. On the other hand, by setting the second intermediate opening VM2-H in the hot start mode larger than the second intermediate opening VM2-S in the normal start mode, the load on the earlier stages of the compressor 2 can be reduced, and surging can be effectively suppressed.

[0030] As described above, according to the above embodiment, it is possible to provide a gas turbine start-up method that can suitably prevent surging in the compressor 2 while suppressing contact between the stationary-side member and the rotating-side member during start-up.

[0031] The contents described in each of the above embodiments can be understood, for example, as follows.

[0032] (1) A gas turbine start-up method according to one aspect includes: selecting one of a normal start mode and a hot start mode as a start mode based on a state of the gas turbine; gradually increasing the rotation speed of the gas turbine by starting startup control based on the startup mode; maintaining an opening degree of an inlet guide vane provided in a compressor of the gas turbine at a first opening degree and maintaining an opening degree of a bleed valve provided in the compressor downstream of the inlet guide vane at a second opening degree in a low rotation speed region where the rotation speed of the gas turbine is lower than a first rotation speed; in a high rotation speed region including a second rotation speed higher than the first rotation speed, controlling an opening degree of the inlet guide vane to a first intermediate opening degree larger than the first opening degree, and controlling an opening degree of the bleed valve to a second intermediate opening degree smaller than the second opening degree; Equipped with the first intermediate opening degree is set so that a value thereof when the hot start-up mode is selected as the start-up mode is larger than a value thereof when the normal start-up mode is selected as the start-up mode, The second intermediate opening degree is set so that the value when the hot start-up mode is selected as the start-up mode is larger than the value when the normal start-up mode is selected as the start-up mode.

[0033] According to the above aspect (1), during startup of a gas turbine whose rotational speed gradually increases according to the startup mode, when the rotational speed is in a low rotational speed range, the opening of the inlet guide vane is maintained at a relatively small first opening, and the opening of the bleed valve is maintained at a relatively large second opening. This makes it possible to effectively avoid fluid instability that tends to occur in the compressor when the rotational speed is low in the early stages of startup. Thereafter, when the rotational speed reaches a high rotational speed range, the opening of the inlet guide vane is increased to a first intermediate opening, thereby increasing the intake air flow rate and pressure ratio in the compressor, thereby increasing the temperature of the compressed air passing through the flow path from the compressor to the combustor and promoting heating during startup. This makes it possible to effectively prevent contact between the stationary side member and the rotating side member during restart.

[0034] As the startup mode implemented during startup of such a gas turbine, either a normal startup mode or a hot startup mode can be selected based on the state of the gas turbine. In the hot startup mode, the first intermediate opening and the second intermediate opening are set to be larger than in the normal startup mode. Specifically, in the hot startup mode, the opening of the inlet guide vane is increased more in the high rotation speed range than in the normal startup mode, thereby more effectively suppressing contact between the stationary-side member and the rotating-side member during restart. In this case, in the hot startup mode, the opening of the bleed valve is increased more than in the normal startup mode, thereby reducing the load on the front stages of the compressor and effectively suppressing the occurrence of surging.

[0035] (2) In another embodiment, in the above embodiment (1), While the rotational speed increases from the first rotational speed to the second rotational speed, the opening degree of the inlet guide vane is controlled to increase monotonically with respect to the rotational speed.

[0036] According to the above aspect (2), when the rotation speed of the gas turbine, which gradually increases at startup, is in the range from the first rotation speed to the second rotation speed, the opening degree of the inlet guide vane is controlled to increase monotonically with respect to the rotation speed.

[0037] (3) In another aspect, in the above aspect (1) or (2), While the rotational speed increases from the first rotational speed to the second rotational speed, the opening degree of the air bleed valve is maintained at the second intermediate opening degree.

[0038] According to the above aspect (3), when the rotation speed of the gas turbine, which gradually increases during startup, is in the range from the first rotation speed to the second rotation speed, the opening degree of the bleed valve is maintained at the second intermediate opening degree regardless of the rotation speed.

[0039] (4) In another embodiment, in any one of the above (1) to (3), The state of the gas turbine is determined based on at least one of a casing temperature of the compressor or a temperature of a cavity communicating with a flow path of compressed air generated by the compressor.

[0040] According to the above aspect (4), the state of the gas turbine used to select the start-up mode is identified based on at least one of the casing temperature and the cavity temperature of the compressor. The casing temperature and the cavity temperature of the compressor are suitable as indicators for determining whether the gas turbine is in a hot state before start-up.

[0041] (5) In another embodiment, in any one of the above (1) to (3), The state of the gas turbine is determined based on the time elapsed since the gas turbine was last shut down.

[0042] According to the above aspect (5), The state of the gas turbine used to select the start-up mode can be easily identified based on the time elapsed since the gas turbine was last shut down.

[0043] (6) In another embodiment, in any one of the above (1) to (5), The first rotation speed is 65 to 75% of the rated rotation speed of the gas turbine.

[0044] According to the above aspect (6), by setting the first rotation speed in the range of 65 to 75% of the rated rotation speed, in the low rotation speed region where the first rotation speed is the upper limit rotation speed, it is possible to preferably avoid the fluid instability phenomenon that is likely to occur in the compressor when the rotation speed is low at the beginning of startup.

[0045] (7) In another embodiment, in any one of the above (1) to (6), The second rotation speed is 85 to 95% of the rated rotation speed of the gas turbine.

[0046] According to the above aspect (7), by setting the second rotation speed to 85 to 95% of the rated rotation speed, contact between the stationary side member and the rotating side member at startup can be suitably suppressed in the high rotation speed range that includes the second rotation speed. [Explanation of symbols]

[0047] 1. Gas turbine 2 Compressor 3A Inlet guide vane 3B Actuator 4 Combustor 5 Rotation Axis 6 Turbine 7. Generator 8 Power system 9A Bleed valve 9B Actuator

Claims

1. selecting one of a normal start mode and a hot start mode as a start mode based on a state of the gas turbine; gradually increasing the rotation speed of the gas turbine by starting startup control based on the startup mode; maintaining an opening degree of an inlet guide vane provided in a compressor of the gas turbine at a first opening degree and maintaining an opening degree of a bleed valve provided in the compressor downstream of the inlet guide vane at a second opening degree in a low rotation speed region where the rotation speed of the gas turbine is lower than a first rotation speed; in a high rotation speed region including a second rotation speed higher than the first rotation speed, controlling an opening degree of the inlet guide vane to a first intermediate opening degree larger than the first opening degree, and controlling an opening degree of the bleed valve to a second intermediate opening degree smaller than the second opening degree; Equipped with the first intermediate opening degree is set so that a value thereof when the hot start-up mode is selected as the start-up mode is larger than a value thereof when the normal start-up mode is selected as the start-up mode, the second intermediate valve opening is set so that a value thereof when the hot start mode is selected as the start mode is larger than a value thereof when the normal start mode is selected as the start mode.

2. 2. The gas turbine start-up method according to claim 1, wherein the opening degree of the inlet guide vane is controlled to increase monotonically with respect to the rotational speed while the rotational speed increases from the first rotational speed to the second rotational speed.

3. 3. The gas turbine start-up method according to claim 1, wherein an opening degree of the bleed valve is maintained at the second intermediate opening degree while the rotational speed is increased from the first rotational speed to the second rotational speed.

4. 3. The gas turbine start-up method according to claim 1, wherein the state of the gas turbine is identified based on at least one of a casing temperature of the compressor or a temperature of a cavity communicating with a flow path of compressed air generated by the compressor.

5. 3. The gas turbine start-up method according to claim 1, wherein the state of the gas turbine is identified based on the elapsed time since the gas turbine was last stopped.

6. 3. The gas turbine start-up method according to claim 1, wherein the first rotational speed is 65 to 75% of a rated rotational speed of the gas turbine.

7. 3. The gas turbine start-up method according to claim 1, wherein the second rotational speed is 85 to 95% of a rated rotational speed of the gas turbine.

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