METHOD FOR STARTING A GAS TURBINE

Abstract

Based on a state of the gas turbine, a normal start mode or a hot start mode is selected as the start mode. When start-up control is started based on the start mode, the speed of the gas turbine gradually increases. In a low speed range, an opening degree of an inlet guide vane provided by a compressor of the gas turbine is maintained at a first opening degree, and an exhaust valve is maintained at a second opening degree. In a high speed range, the inlet guide vane is controlled at a first intermediate opening degree larger than the first opening degree, and the exhaust valve is controlled at a second intermediate opening degree smaller than the second opening degree. The first intermediate opening degree is set larger in the hot start mode than in the normal start mode. The second intermediate opening degree is set larger in the hot start mode than in the normal start mode.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Japanese Patent Application No. 2024-065919, filed on April 16, 2024. The entire contents of the above-mentioned application are incorporated herein by reference. TECHNICAL FIELD

[0002] The disclosure relates to a method for starting a gas turbine. STATE OF THE ART

[0003] In a gas turbine, combustion gas, produced by the mixed combustion of fuel from a fuel supply system and combustion air, is used to drive a turbine. The combustion air used to generate the combustion gas is generated by a compressor of the gas turbine. Specifically, an inlet guide vane (IGV) is provided at the inlet of the compressor to vary the volume of the intake air flow by adjusting its opening degree. An exhaust valve is provided downstream of the inlet guide vane to exhaust part of the compressed air generated by the compressor to the outside.

[0004] A related technology for starting this type of gas turbine is known, for example, from JP 2000-291449 A. In JP 2000-291449 A, when the gas turbine is stopped and driven by the starting motor, the inlet guide vane is set to a predetermined opening degree and the exhaust valve is set to a relatively large opening degree, so that at low speed in the initial stage of start-up, most of the compressed air is exhausted to the outside as exhaust air. Subsequently, when the speed increases sufficiently, the opening degree of the exhaust valve is reduced to the point where the exhaust valve is completely closed, resulting in a transition to continuous operation. In JP 2000-291449 A, the exhaust valve can not only open and close but also continuously adjust its opening degree.Thus, at low speed in the initial stage of starting, the exhaust valve is set to a predetermined intermediate opening degree, which reduces the amount of compressed air wastefully discharged to the outside as exhaust air during starting compared to when the exhaust valve is set to the fully open state, thereby improving the efficiency of the gas turbine and avoiding the phenomenon of fluid instability during starting.

[0005] Here, there is a difference in heat capacity between the rotating element and the stationary element that constitute the compressor. Since the heat capacity of the rotating element is usually larger than that of the stationary element, it is more difficult to cool the rotating element than the stationary element after the gas turbine is stopped. Thus, when the gas turbine is restarted from a hot state where the time elapsed since the last stop is relatively short, the rotating element is in a state of thermal expansion compared to the stationary element, and the clearance between the rotating element and the stationary element is reduced, so contact may occur. Therefore, the start-prohibited time is usually set until this condition is resolved, or measures are taken to increase the set clearance in advance.However, the former limits the use of the gas turbine, and the latter reduces its efficiency.

[0006] JP 2022-30038 A addresses these issues by temporarily enlarging the inlet guide vane opening during gas turbine startup, thereby increasing the intake airflow volume and the pressure ratio in the compressor. This increases the temperature of the compressed air flowing through the compressor flow path, and reduces the cooling of the stationary components and the rotating components of the compressor located adjacent to the flow path, thus promoting heating during startup. Thus, the clearance between the stationary component and the rotating component is easily restored to a suitable value, and contact between the stationary component and the rotating component can be reduced. PRESENTATION OF THE INVENTION

[0007] In JP 2022-30038 A, the opening degree of the inlet guide vane is temporarily controlled to increase to avoid contact between the stationary element and the rotating element during startup. Such a temporary increase in the opening degree of the inlet guide vane occurs at a stage where the rotational speed reaches a relatively high range in a startup sequence in which the rotational speed of the gas turbine gradually increases. In this rotational speed range, the opening degree of the exhaust valve is controlled to be small, so that if the opening degree of the inlet guide vane is increased as described in JP 2022-30038 A, the load on the front stage of the compressor increases, causing aerodynamic instability and surging.

[0008] At least one embodiment of the disclosure has been provided in consideration of the above circumstances, and an object of the disclosure is to provide a method for starting a gas turbine capable of appropriately preventing surging in the compressor while reducing the occurrence of contact between the stationary member and the rotating member during start-up.

[0009] A method for starting a gas turbine according to at least one embodiment of the disclosure comprises the following to solve the above-mentioned problem: Selecting a normal start mode or a hot start mode as the start mode based on a state of the gas turbine; gradually increasing the speed of the gas turbine by starting a start-up control based on the start-up mode; Maintained in a low speed range, wherein the speed of the gas turbine is less than a first speed, an opening degree of an inlet guide vane provided in a compressor of the gas turbine to a first opening degree, and an opening degree of an outlet valve provided downstream of the inlet guide vane in the compressor to a second opening degree; and Control, in a high speed range, wherein the speed includes a second speed which is higher than the first speed, the opening degree of the inlet guide vane to a first intermediate opening degree which is greater than the first opening degree, and the degree of opening of the exhaust valve to a second intermediate degree of opening which is smaller than the second degree of opening, wherein the first intermediate opening degree when the hot start mode is selected as the start mode is set larger than the first intermediate opening degree when the normal start mode is selected as the start mode, and the second intermediate opening degree when the hot start mode is selected as the start mode is set larger than the second intermediate opening degree when the normal start mode is selected as the start mode.

[0010] According to at least one embodiment of the disclosure, it is possible to provide a method for starting a gas turbine capable of appropriately preventing surging in the compressor while reducing the occurrence of contact between the stationary member and the rotating member during start-up. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The disclosure will be described with reference to the accompanying drawings, wherein like reference numerals refer to like elements. Fig. 1 is a schematic diagram showing a schematic configuration of a gas turbine according to an embodiment. Fig. 2 is a flowchart showing a method for starting the gas turbine according to Fig. 1 shows. Fig. 3 is a time chart showing a change in the opening degree of the intake guide vane and the exhaust valve with respect to the rotational speed when in step S1 of Fig. 2 the normal start mode is selected. Fig. 4 is a time chart showing a change in the opening degree of the intake guide vane and the exhaust valve with respect to the rotational speed when in step S1 of Fig. 2 the hot start mode is selected. DESCRIPTION OF THE EMBODIMENTS

[0012] Some embodiments of the disclosure will be described below with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, or the like of the configurations described as embodiments or illustrated in the drawings are not intended to limit the scope of the disclosure, but are merely illustrative examples.

[0013] First, with reference to Fig. 1 describes the overall configuration of a gas turbine 1 to which the method for starting a gas turbine according to at least one embodiment of the disclosure is applied. Fig. 1 is a schematic diagram showing the schematic configuration of the gas turbine 1 according to an embodiment.

[0014] The gas turbine 1 has a compressor 2 for generating compressed air as combustion air, a combustion chamber 4 for generating combustion gas by mixing and burning fuel with combustion air, and a turbine 6, which has a common rotor shaft 5 with the compressor 2 and can be driven by the combustion gas generated by the combustion chamber 4. A generator 7 is connected to the rotor shaft 5 and can generate electricity by driving the generator 7 using the power of the turbine 6. The generator 7 is electrically connected to a power grid 8 and can feed the electricity generated by the generator 7 into the power grid 8.

[0015] At the inlet of compressor 2, an inlet guide vane 3A is provided for adjusting the air intake. The opening degree of the inlet guide vane 3A can be adjusted by an actuator 3B. An exhaust valve 9A is provided downstream of the inlet guide vane 3A in compressor 2 so that part of the compressed air generated by compressor 2 can be discharged. The opening degree of the exhaust valve 9A can be adjusted by an actuator 9B.

[0016] Next, a method for starting the gas turbine 1 having the above configuration will be described. Fig. 2 is a flowchart showing a method for starting the gas turbine 1 according to Fig. 1 shows. Fig. 3 is a time chart showing a change in the opening degree of the intake guide vane 3A and the exhaust valve 9A with respect to the rotational speed when in step S1 of Fig. 2 the normal start mode is selected. Fig. Fig. 4 is a time chart showing a change in the opening degree of the intake guide vane 3A and the exhaust valve 9A with respect to the rotational speed when in step S1 of Fig. 2 the hot start mode is selected.

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

[0018] Such a start-up mode can be selected based on the state of the gas turbine 1. Specifically, the start-up mode can be selected based on whether at least some of the components of the gas turbine 1 are heated up or not. In this case, the component of the gas turbine 1 that serves as a benchmark for judging whether the gas turbine 1 is heated up or not can be a component on the rotating side of the compressor 2 of the gas turbine 1 (e.g., a rotor) or a component on the stationary side (e.g., a compressor casing surrounding the rotor). The temperatures of these components can be measured directly or be estimated values ​​calculated based on various parameters related to the operating state of the gas turbine 1 (e.g., the casing temperature and the cavity temperature of the compressor 2). When the start-up mode is selected, these temperatures are compared with a predetermined threshold value.If the temperature is below the threshold, the normal start mode is selected as the start mode, and if the temperature is not below the threshold, the hot start mode is selected as the start mode.

[0019] In another embodiment, it can be determined whether or not at least some of the components of the gas turbine 1 are heated up based on the time elapsed since the last stop of the gas turbine 1. In this case, although the temperatures of at least some of the components of the compressor 2 cannot be directly measured, it is possible to readily assess whether or not at least some of the components of the compressor 2 are heated up based on the time elapsed since the last stop. The time elapsed since the last stop is measured, for example, with a timer, and the measurement result is compared with a predetermined threshold value, thereby providing a criterion for selecting the start mode.That is, if the elapsed time is not less than the threshold, the normal start mode is selected as the start mode, and if the elapsed time is less than the threshold, the hot start mode is selected as the start mode.

[0020] The gas turbine 1 then performs startup control according to the startup mode selected in step S1 (step S2). During the startup control, the rotational speed R of the gas turbine 1 is controlled to gradually increase with elapsed time.

[0021] In the initial stage where the rotational speed R is relatively low when the start-up control is started (low-speed range), the opening of the intake guide vane 3A is maintained at a relatively small first opening degree V1, and the opening of the exhaust valve 9A is maintained at a relatively large second opening degree V2 (step S3). When the gas turbine 1 is started in the stop state, the start-up control is started by a torque exerted by the drive of the generator 7 as an electric motor, and then, when the rotational speed R increases to a certain degree, the start-up control switches to turbine drive using the combustion gas generated by the combustion chamber 4.In the low speed range where the rotational speed R is relatively low, by maintaining the opening of the exhaust valve 9A at a relatively large second opening degree V2, it is possible to appropriately avoid the phenomenon of fluid instability which is likely to occur in the compressor 2 at low speed in the initial stage of start-up.

[0022] As in Fig. 3 and Fig. 4, in the low speed range, the first opening degree V1, in which the opening degree of the inlet guide vane 3A is maintained, and the second opening degree V2, in which the opening of the exhaust valve 9A is maintained, are set as common target values ​​for both the normal start mode and the hot start mode.

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

[0024] When the rotational speed R continues to increase and exceeds the first rotational speed R1 (step S4: YES), the opening degree of the intake guide vane 3A increases monotonically with respect to the rotational speed R, and the exhaust valve 9A is maintained at a second intermediate opening degree VM2 (step S5). The second intermediate opening degree VM2 is an intermediate opening degree between the fully closed state (0%) and the fully opened state (100%). In the high rotational speed range where the rotational speed R exceeds the first rotational speed R1, the opening degree of the intake guide vane 3A is increased, thereby increasing the intake air flow volume and the pressure ratio in the compressor 2, so that the temperature of the compressed air flowing from the compressor 2 through the flow path to the combustion chamber 4 rises, thereby promoting warm-up during startup.Thus, the occurrence of contact between the stationary element and the rotating element during restart is appropriately reduced.

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

[0026] When the rotational speed R continues to increase and exceeds the second rotational speed R2 (step S6: YES), the opening degree of the intake guide vane 3A is maintained at a 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 opened state (opening degree is 100%). At this time, as in step S5, the opening degree of the exhaust valve 9A is maintained at the second intermediate opening degree VM2.

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

[0028] When the rotational speed R continues to rise and exceeds the third rotational speed R3 (step S8: YES), as in step S7, the opening degree of the inlet guide vane 3A is maintained at the first intermediate opening degree VM1, while the opening degree of the exhaust valve 9A is controlled in the fully closed state (opening degree is 0%) (step S9). When the rotational speed R reaches a fourth rotational speed R4 (rated rotational speed) (step S10: YES), a series of startup controls is completed (step S11). Thus, the gas turbine 1 is brought into the no-load rated speed operation state, and then the generator 7 is connected to the power grid 8.

[0029] In the high speed range where the speed R is higher than the first speed R1 in the series of starting controls described above, as a comparison of Fig. 3 and Fig.As shown in Figure 4, in the hot start mode, the values ​​of the first intermediate opening degree VM1 and the second intermediate opening degree VM2 are set larger than those in the normal start mode. Specifically, the first intermediate opening degree VM1-H in the hot start mode is set larger than the first intermediate opening degree VM1-S in the normal start mode, so that the intake air flow volume and the pressure ratio in the compressor 2 increase, and the occurrence of contact between the stationary element and the rotating element during startup is more appropriately prevented. On the other hand, the second intermediate opening degree VM2-H in the hot start mode is set larger than the second intermediate opening degree VM2-S in the normal start mode, so that the load on the front stage of the compressor 2 is reduced, and the occurrence of surging can be appropriately reduced.

[0030] As already stated, according to the embodiments described above, it is possible to provide a method for starting a gas turbine capable of appropriately preventing surging in the compressor 2 while reducing the occurrence of contact between the stationary member and the rotating member during start-up.

[0031] The content shown in the embodiments described above is to be understood, for example, as follows. (1) A method for starting a gas turbine according to one aspect comprises: Selecting a normal start mode or a hot start mode as the start mode based on a state of the gas turbine; gradually increasing the speed of the gas turbine by starting a start-up control based on the start-up mode; Maintained in a low speed range, wherein the speed of the gas turbine is less than a first speed, an opening degree of an inlet guide vane provided in a compressor of the gas turbine to a first opening degree, and an opening degree of an outlet valve provided downstream of the inlet guide vane in the compressor to a second opening degree; and Control, in a high speed range, wherein the speed includes a second speed which is higher than the first speed, the opening degree of the inlet guide vane to a first intermediate opening degree which is greater than the first opening degree, and the degree of opening of the exhaust valve to a second intermediate degree of opening which is smaller than the second degree of opening, wherein the first intermediate opening degree when the hot start mode is selected as the start mode is set larger than the first intermediate opening degree when the normal start mode is selected as the start mode, and the second intermediate opening degree when the hot start mode is selected as the start mode is set larger than the second intermediate opening degree when the normal start mode is selected as the start mode.

[0032] According to aspect (1) described above, when the rotational speed is in the low-speed range during the start-up of the gas turbine, in which the rotational speed gradually increases according to the start-up mode, the opening of the inlet guide vane is maintained at a relatively small first opening degree and the opening of the exhaust valve is maintained at a relatively large second opening degree. In this way, the phenomenon of fluid instability that is likely to occur in the compressor at low rotational speed in the initial stage of start-up can be appropriately avoided. Subsequently, when the rotational speed reaches the high-speed range, the opening of the inlet guide vane is increased to the first intermediate opening degree to increase the volume of the intake air flow and the pressure ratio in the compressor, thereby increasing the temperature of the compressed air flowing from the compressor through the flow path to the combustor, thereby promoting heating during start-up.This can appropriately prevent the occurrence of contact between the stationary element and the rotating element during the restart of the gas turbine.

[0033] As the starting mode executed during gas turbine startup, a normal start mode or a hot start mode can be selected based on the state of the gas turbine. In the hot start mode, the values ​​of the first intermediate opening degree and the second intermediate opening degree are each set larger than those in the normal start mode. Specifically, in the hot start mode, the occurrence of contact between the stationary element and the rotating element during gas turbine restart can be appropriately reduced by increasing the opening degree of the inlet guide vane in the high speed range more than in the normal start mode. At this time, in the hot start mode, the opening degree of the exhaust valve is increased more than that in the normal start mode, thereby preventing the load on the front stage of the compressor and appropriately reducing the occurrence of surging.

[0034] (2) According to a further aspect, according to aspect (1) described above, the opening degree of the inlet guide vane is controlled such that the opening degree increases monotonically with respect to the speed as the speed increases from the first speed to the second speed.

[0035] According to the aspect (2) described above, when the rotational speed of the gas turbine, which successively increases during start-up, is in the range from the first rotational speed to the second rotational speed, the opening of the inlet guide vane is controlled to increase monotonously with respect to the rotational speed.

[0036] (3) According to a further aspect, according to aspect (1) or (2) described above, the opening degree of the exhaust valve is maintained at the second intermediate opening degree while the speed increases from the first speed to the second speed.

[0037] According to aspect (3), when the rotational speed of the gas turbine, which successively increases during start-up, is in the range from the first rotational speed to the second rotational speed, the opening of the exhaust valve is maintained at the second intermediate opening degree regardless of the rotational speed.

[0038] (4) According to a further aspect, according to any one of aspects (1) to (3) the condition of the gas turbine is determined based on a casing temperature of the compressor and / or a temperature of a cavity that communicates with a flow path of the compressed air generated by the compressor.

[0039] According to aspect (4) described above, the gas turbine state used for selecting the starting mode is determined based on the casing temperature and / or the compressor cavity temperature. The casing temperature or the compressor cavity temperature is suitable for determining whether the gas turbine is in a hot state before starting.

[0040] (5) According to a further aspect, according to any one of the aspects (1) to (3) described above the state of the gas turbine is determined based on the time elapsed since the last stop of the gas turbine.

[0041] According to the aspect (5) described above, the state of the gas turbine used for selecting the start mode can be easily determined based on the time elapsed since the last stop of the gas turbine.

[0042] (6) According to a further aspect, according to any one of the aspects (1) to (5) described above the first speed is 65% to 75% of the rated speed of the gas turbine.

[0043] According to the aspect (6) described above, by setting the first speed within the range of 65% to 75% of the rated speed, it is possible to appropriately avoid the phenomenon of fluid instability likely to occur in the compressor at low speed in the initial stage of starting in the low speed range where the first speed is the upper limit of the speed.

[0044] (7) According to a further aspect, according to any one of the aspects (1) to (6) described above the second speed is 85% to 95% of the rated speed of the gas turbine.

[0045] According to the above-described aspect (7), by setting the second rotational speed within the range of 85% to 95% of the rated rotational speed, it is possible to appropriately prevent the occurrence of contact between the stationary member and the rotating member during start-up in the high rotational speed range including the second rotational speed.

[0046] While the preferred embodiments of the invention have been described above, it is understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the invention. The scope of the invention is therefore determined solely by the following claims. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2024-065919

[0001] JP 2000-291449 A

[0004] JP 2022-30038 A [0006, 0007]

Claims

[1] Method for starting a gas turbine, comprising: Selecting a normal start mode or a hot start mode as the start mode based on the state of the gas turbine; successive increase of the gas turbine speed by starting a start-up control based on the start mode; Maintain, in a low speed range, where the speed of the gas turbine is less than a first speed, of an opening degree of an inlet guide vane provided in a compressor of the gas turbine to a first opening degree, and of an opening degree of an outlet valve provided downstream of the inlet guide vane in the compressor to a second opening degree; and Controls, in a high speed range, where the speed includes a second speed that is higher than the first speed, of the opening degree of the inlet guide vane to a first intermediate opening degree that is larger than the first opening degree, and of the opening degree of the exhaust valve to a second intermediate opening degree, which is smaller than the second opening degree, wherein The first intermediate opening degree, when hot start mode is selected as the start mode, is set higher than the first intermediate opening degree, when normal start mode is selected as the start mode, and The second intermediate opening degree is set higher when hot start mode is selected as the start mode than the second intermediate opening degree when normal start mode is selected as the start mode. [2] Method for starting a gas turbine according to claim 1, wherein the opening degree of the inlet guide vane is controlled such that the opening degree increases monotonically with respect to the rotational speed as the rotational speed increases from the first rotational speed to the second rotational speed. [3] Method for starting a gas turbine according to claim 1, wherein the degree of opening of the exhaust valve is maintained at the second intermediate degree of opening while the rotational speed increases from the first rotational speed to the second rotational speed. [4] Method for starting a gas turbine according to claim 1, wherein the state of the gas turbine is determined on the basis of a casing temperature of the compressor and / or a temperature of a cavity that is connected to a flow path of the compressed air generated by the compressor. [5] Method for starting a gas turbine according to claim 1, wherein the state of the gas turbine is determined on the basis of the time elapsed since the last stop of the gas turbine. [6] Method for starting a gas turbine according to claim 1, wherein the first rotational speed is 65% to 75% of the rated rotational speed of the gas turbine. [7] Method for starting a gas turbine according to claim 1, wherein the second speed is 85% to 95% of the rated speed of the gas turbine.

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