Gas turbines that can use hydrogen as fuel

Abstract

To reduce NOx emissions in a gas turbine that can use hydrogen as fuel.SOLUTION: A gas turbine 1 is configured, so that when rotational frequency of a turbine shaft is predetermined rotational frequency in a combustor 6 to which fuel and compressed air are supplied, an amount of the compressed air to be supplied to a primary combustion field in the combustor is set to an amount that enables an equivalence ratio in the primary combustion field 8a to become an equivalence ratio preventing misfire in an operating state with the predetermined rotational frequency and predetermined load, so that when rotation of the turbine shaft 2 is started, fuel supply to the combustor is started, and so that after ignition within the combustor, the amount of the fuel to be supplied to the combustor is controlled to cause the rotational frequency of the turbine shaft to increase to the predetermined rotational frequency and before the rotational frequency of the turbine shaft reaches the predetermined frequency, the magnitude of the load increases to the predetermined load.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a gas turbine engine (hereinafter referred to as a "gas turbine"), and more particularly to the control of a gas turbine (hydrogen gas turbine) that can use hydrogen as fuel.

Background Art

[0002] From the perspective of preventing global warming and decarbonization, research and development of heat engines such as gas turbines that use hydrogen as fuel are progressing. When using hydrogen as fuel, if there are regions with high fuel concentration in the combustion field, the combustion temperature will rise and NOx generation will tend to increase. Therefore, in hydrogen-fueled gas turbines, various configurations are being considered to prevent the formation of regions with high fuel concentration in the combustion field of the combustor as much as possible. For example, Patent Document 1 proposes a configuration for a gas turbine combustor that employs a premixed combustion method in which a mixture of fuel and air is supplied to the combustion chamber to equalize the temperature of the flame formed in the combustion chamber and suppress NOx emissions. This configuration aims to achieve stable combustion throughout the entire operating process from ignition to rated load of the gas turbine by precisely controlling the fuel-air ratio of the premixed mixture, thereby improving efficiency, reducing NOx emissions, and reducing the number of parts. Specifically, the document discloses a configuration in which a burner that supplies fuel and air to the combustion chamber has an annular fuel nozzle having an annular pipe with multiple fuel injection holes and multiple supply pipes connected thereto, and an air hole plate that is spaced apart downstream of the annular fuel nozzle and has multiple air holes facing the multiple fuel injection holes. Patent Document 2 proposes a configuration in which, in order to achieve stable combustion and low NOx emissions across the entire load range of a gas turbine, the gas turbine combustor has multiple stages of combustion sections spaced apart in the axial direction, multiple fuel supply systems independently connected to each of these combustion sections, a premixed fuel supply section and a diffusion combustion fuel supply section provided in each of these fuel supply systems, and a control device that switches each of these fuel supply sections to supply only either premixed fuel or diffusion combustion fuel, and after starting combustion in a diffusion combustion method that enables stable combustion over a wide fuel-air ratio range, it switches to a premixed combustion method.Patent Document 3 proposes an operating method for a gas turbine engine combustor using a highly reactive fuel such as hydrogen, in which multiple fuel injection units are arranged in a ring to achieve low NOx combustion and prevent the generation of unburned gas during startup and shutdown. This method involves injecting a highly reactive main fuel from one part of the ring, and switching between injecting a less reactive auxiliary fuel and the main fuel from another part. During startup, the auxiliary fuel is injected and ignited, then switched to the main fuel to perform rated rotational speed operation, and during shutdown, the rotation is reduced by switching from the main fuel to the auxiliary fuel. Patent Document 4 describes a combustor for a gas turbine engine with a multi-stage burner configuration, which includes a main burner that supplies fuel or a premix to a primary combustion region upstream of the combustion chamber and a follow-up burner that supplies fuel or a premix to a secondary combustion region downstream of the primary combustion region of the combustion chamber. In order to promote the premixing of hydrogen-containing gas ejected from the follow-up burner with compressed air, it is proposed that after ejecting fuel and air from the nozzle of the follow-up burner, the mixture is passed through a duct of a certain length before being sent into the combustion chamber, thereby thoroughly mixing the fuel and air before combustion. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2016-23916 [Patent Document 2] Japanese Patent Publication No. 7-233945 [Patent Document 3] Japanese Patent Publication No. 2018-194210 [Patent Document 4] Japanese Patent Publication No. 2018-4138 [Overview of the project] [Problems that the invention aims to solve]

[0004] In conventional hydrogen gas turbine combustors, as described above, improvements are typically made to the combustion and compressed air supply structure, such as the combustion nozzle that supplies combustion and compressed air to the combustion field, in order to suppress NOx generation and prevent the formation of regions with high fuel concentrations. However, the structure of the conventional technology described above is somewhat complex, with a large number of parts. While this is feasible for combustors of medium to large gas turbines, it becomes difficult to manufacture combustors for small gas turbines because it is difficult to process and form many fine holes with small parts. Furthermore, a large number of parts negates the advantage of the lightweight nature of small gas turbines. Therefore, if there is a method to prevent regions with high fuel concentrations in the combustion field without complicating the combustion and compressed air supply structure, it would be advantageous as it would allow for the use of NOx-reduced configurations in various hydrogen gas turbines, regardless of size.

[0005] Incidentally, in the operation of a gas turbine, generally, at startup, the starter rotates the turbine shaft while fuel is supplied to the combustor to ignite it. Then, under no-load conditions, the amount of fuel is increased to raise the rotational speed of the turbine shaft to a predetermined speed, for example, the rated speed. After establishing the predetermined speed and no-load operating state, the amount of fuel is increased to increase the load (power generation in the case of a generator) to a predetermined load, for example, the rated load, while the predetermined speed is maintained. In this operating method, the equivalence ratio (amount of fuel / amount of compressed air) near the fuel supply point in the combustion field (primary combustion field) is adjusted so as not to misfire under the predetermined speed and no-load operating state. Consequently, when increasing the fuel supply to raise the load from no load to a predetermined load while maintaining the rotational speed at a predetermined speed, the equivalence ratio of the primary combustion field increases locally, leading to an increase in NOx generation (in the conventional technology described above, the combustion and compressed air supply structure is designed to suppress such a localized increase in the equivalence ratio of the primary combustion field).

[0006] As described above, when increasing the amount of fuel to raise the load from no load to a predetermined load, one method to reduce the equivalence ratio of the primary combustion field in order to suppress NOx generation is to increase the amount of compressed air supplied to the primary combustion field. In this regard, the inventors of the present invention have conducted research and found that in a configuration in which the amount of compressed air supplied to the primary combustion field is increased so that the equivalence ratio of the primary combustion field is suppressed in an operating state of predetermined rotational speed and predetermined load, when trying to bring the operating state to a predetermined rotational speed and no load at the start of the gas turbine, the equivalence ratio is too low and misfires occur. However, it has been found that by starting to apply the load after the combustor has ignited, before the rotational speed of the turbine shaft reaches the predetermined rotational speed, for example, at about half the predetermined rotational speed, and then controlling the amount of fuel so that the rotational speed reaches the predetermined rotational speed and the load becomes the predetermined load, it is possible to achieve an operating state of predetermined rotational speed and predetermined load while suppressing the increase in the equivalence ratio of the primary combustion field as much as possible. In other words, this operating method makes it possible to suppress NOx generation without using the complex combustion and air supply structure of the conventional technology described above, which is used to suppress localized increases in the equivalence ratio of the primary combustion field.

[0007] Thus, one of the objectives of the present invention is to reduce the amount of NOx generated or emitted in a gas turbine that can use hydrogen as fuel.

[0008] Furthermore, a further object of the present invention is to provide a gas turbine as described above, having a configuration in which the amount of compressed air supplied to the primary combustion field is increased so that the equivalent ratio of the primary combustion field of the combustor is kept lower when operating at a predetermined rotational speed and predetermined load, and to provide a configuration that controls the operating state so as to achieve the operating state of a predetermined rotational speed and predetermined load without misfiring during rotational startup. [Means for solving the problem]

[0009] According to the present invention, the above problem is solved by a gas turbine, A combustor supplied with fuel to be burned and compressed air, wherein the amount of compressed air supplied to the primary combustion field in the combustor when the rotational speed of the turbine shaft is a predetermined rotational speed is an amount that makes the equivalent ratio in the primary combustion field an equivalent ratio that does not misfire under the operating conditions of a predetermined rotational speed and a predetermined load, A fuel supply control means for controlling the amount of fuel supplied to the combustor. Load control means for controlling the magnitude of the load acting on the turbine shaft Includes, This is achieved by a gas turbine in which the fuel supply control means is configured to start supplying fuel to the combustor when the rotation of the turbine shaft is started, and after ignition in the combustor, to control the amount of fuel supplied to the combustor so that the rotational speed of the turbine shaft rises to the predetermined rotational speed, and the load control means is configured to increase the magnitude of the load to the predetermined load before the rotational speed of the turbine shaft reaches the predetermined rotational speed.

[0010] In the above configuration, the "gas turbine" may be any type of gas turbine in which a compressor, a turbine, and load equipment such as a generator on which the load acts are connected to the turbine shaft. The "combustor" may be any type of combustor, such as a can type or annular type, and as described above, the amount of compressed air supplied to the primary combustion field in the combustor when the rotational speed of the turbine shaft is a predetermined rotational speed is adjusted to satisfy the condition that the equivalent ratio in the primary combustion field does not misfire under the operating conditions of a predetermined rotational speed and a predetermined load. Here, the "predetermined rotational speed" may be a rotational speed at which the gas turbine rotates stably or efficiently, which can be appropriately set based on experiments, etc., and may be the "rated rotational speed" (rated value of rotational speed), which is the rotational speed during normal operation of the gas turbine. The "predetermined load" may be the magnitude of the load that the gas turbine outputs stably or efficiently, which can be appropriately set based on experiments, etc., and may be the "rated load" (rated value of load), which is the load during normal operation of the gas turbine. As already mentioned, the "primary combustion field" refers to the combustion field on the upstream side of the combustion chamber of the combustor, specifically the area near the fuel supply points such as fuel injection holes. Its specific range varies depending on the shape of the combustion chamber, but it can generally be the range from the upstream edge of the flame resulting from the combustion of fuel and compressed air upstream along the direction of gas flow in the combustion chamber to the downstream point where additional compressed air is supplied along the direction of gas flow (compressed air is usually supplied into the combustion chamber in multiple stages along the direction of gas flow). Furthermore, the amount of compressed air supplied to the primary combustion field is adjusted by appropriately adjusting the diameter of the supply port that delivers compressed air to the primary combustion field. The "fuel supply control means" may be a means of adjusting the amount of fuel supplied into the combustion chamber in any form. The "load control means" may be a means of controlling the magnitude of the load (work or power) acting on the turbine shaft in any form. When a gas turbine is used as a power source for a generator, the load is the amount of power output to the generator or the generated electricity, and the load control means may be means for adjusting the amount of power output or the generated electricity of the generator.

[0011] In the configuration of the present invention described above, when the rotation of the turbine shaft is started, the fuel supply control means starts supplying fuel to the combustor, and when the mixture of fuel and compressed air is ignited in the combustor, it controls the amount of fuel supplied to the combustor to increase so that the rotational speed of the turbine shaft rises to a predetermined rotational speed, while the load control means operates to increase the magnitude of the load to a predetermined load even before the rotational speed of the turbine shaft reaches a predetermined rotational speed (which may be the rated rotational speed). In this case, since the load is applied to the turbine shaft even before the rotational speed of the turbine shaft reaches a predetermined rotational speed, the amount of fuel required to increase the rotational speed of the turbine shaft is greater than in the no-load state, and the operating state of the gas turbine transitions to the predetermined rotational speed and predetermined load used in normal operation without going through the predetermined rotational speed and no-load state. In this case, in the present invention, it becomes unnecessary to ensure a high equivalence ratio in the primary combustion field to prevent misfires in the predetermined rotational speed and no-load state, and more compressed air is introduced to lower the equivalence ratio, thus suppressing the generation of NOx. Furthermore, it should be understood that the suppression of NOx generation can be achieved without using the complex combustion and air supply structures proposed in the aforementioned prior art. In the configuration of the present invention described above, as already mentioned, the amount of fuel used until the rotational speed reaches a predetermined speed is large. However, if the load equipment connected to the turbine shaft is a generator, the energy of the fuel used until the rotational speed reaches the rated speed can be converted into electrical energy and stored, so the loss until the rotational speed reaches a predetermined speed is not expected to be very large.

[0012] In the configuration of the present invention described above, when the load control means applies a load before the rotational speed of the turbine shaft reaches a predetermined rotational speed, in order to prevent the rotation of the turbine shaft from becoming unstable due to the start of the load application, the load control means may be configured to start increasing the magnitude of the load from the time the rotational speed of the turbine shaft reaches a rotational speed at which the load can be applied to the turbine shaft. Furthermore, in order to prevent the rotation of the turbine shaft from becoming unstable, the fuel supply control means may be configured to control the amount of fuel supplied to the combustor so that the rotational speed of the turbine shaft does not decrease from the start of rotation until it reaches a predetermined rotational speed. Specifically, the fuel supply control means may be configured to control the amount of fuel by referring to the rotational speed of the turbine shaft so that the rotational speed of the turbine shaft gradually increases up to a predetermined rotational speed.

[0013] Furthermore, in the above configuration, as already mentioned, when the gas turbine is started, the operating state of the gas turbine transitions to a predetermined rotational speed and load without going through a predetermined rotational speed and no-load state. Therefore, the equivalence ratio of the primary combustion field when the turbine shaft rotational speed is a predetermined rotational speed can be reduced to a range that does not misfire at a predetermined load, thereby suppressing NOx generation as much as possible. Accordingly, in the above configuration of the present invention, the amount of compressed air supplied to the primary combustion field in the combustor when the turbine shaft rotational speed is a predetermined rotational speed may be an amount that makes the equivalence ratio in the primary combustion field the usable lower limit of the equivalence ratio that does not misfire at the predetermined rotational speed and load operating state. That is, such compressed air amount may be maximized within a usable range that does not misfire at the predetermined rotational speed and load operating state.

[0014] The above-described configuration of the present invention is preferably applied when hydrogen is used as fuel for a gas turbine; therefore, the fuel may be hydrogen, but is not limited to hydrogen. [Effects of the Invention]

[0015] Thus, in the gas turbine of the present invention described above, to put it simply, since the operating state is shifted to a state of a predetermined rotational speed and a predetermined load without being in a state of a predetermined rotational speed and no load, as already mentioned, the equivalence ratio in the state of a predetermined rotational speed and a predetermined load can be reduced, and the reduction of the NOx generation amount can be achieved. Importantly, the configuration of the present invention improves the operating process at the start of the gas turbine, so that the reduction of the NOx generation amount is expected, and since no complicated improvement is required for the supply parts of fuel and compressed air, it should be understood that the present invention can be applied to small gas turbines in which it is difficult to realize a complicated structure regardless of the size of the gas turbine. The gas turbine of the present invention can be used for a gas turbine that is miniaturized to be mounted on a vehicle such as an automobile and uses hydrogen as fuel, and thereby, a wider spread of the hydrogen gas turbine is expected.

[0016] Other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments of the present invention.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1(A) and (B) are a schematic diagram of a gas turbine according to the present embodiment and a diagram showing the configuration of its control device in the form of a block diagram, respectively. [Figure 2] FIG. 2 is a diagram schematically showing the change in the combustion temperature T with respect to the equivalence ratio (fuel amount / compressed air amount) F / A. [Figure 3] FIG. 3(A) and (B) are diagrams schematically showing the change in the equivalence ratio F / A with respect to the increase in the rotational speed Rpm of the turbine shaft at the start of the gas turbine. (A) is the case of a conventional general operating method, and (B) is the case of the operating method according to the present embodiment. [Figure 4] FIG. 4 is a diagram showing the processing process at the start-up operation of the gas turbine according to the present embodiment in the form of a flowchart.

Explanation of Reference Numerals

[0018] 1... Gas turbine, 2... Turbine shaft, 3... Turbine, 4... Compressor, 5... Load equipment (generator), 6... Combustor, 7... Compressed air flow path, 7a... Compressed air supply port to the primary combustion field, 7b... Compressed air flow path to the primary combustion field, 7c... Compressed air supply port to the secondary combustion field, 8... Combustion chamber, 8a... Primary combustion field, 8b... Secondary combustion field, 9... Fuel supply device, 10... Combustion gas flow path, 50... Turbine operation command unit, 51... Load requirement unit, 52... Rotation speed control unit, 53... Rotation speed detection unit, 54... Load control unit, 55... Fuel quantity control unit, 60... Starter, 61... Igniter, f... Fuel flow, a... Compressed air flow

Best Mode for Carrying Out the Invention

[0019] Basic configuration of a gas turbine The configuration of this embodiment is applicable to various gas turbines. As shown in Figure 1(A), the gas turbine 1 may, in its basic configuration, have a turbine 3 connected to the turbine shaft 2, a compressor 4, load equipment 5 such as a generator, and a combustor 6. In basic operation, compressed air a, compressed by the rotation of the turbine shaft 2 in the compressor 4, is sent through the passage 7 to the combustion chamber 8 of the combustor 6, where it is mixed with fuel f from the fuel supply device 9 and burned. The resulting combustion gas is sent to the turbine 3 through the combustion gas passage 10, rotating the turbine shaft 2. This performs the compression of air in the compressor 4 and the operation of the load equipment 5, for example, generating electricity by rotating the rotor of a generator. More specifically regarding the combustor 6, typically, compressed air a is sent to the combustion chamber 8 in multiple stages so that the fuel and air are burned more efficiently. Specifically, compressed air a is partially injected from a supply port 7a near the fuel f supply port of the fuel device 9 (the right-hand region of the combustion chamber in the figure, primary combustion field 8a), mixed with fuel f in various ways, and another portion is discharged from a supply port 7c to a region downstream of the primary combustion field 8a (secondary combustion field 8b). The fuel supplied to the combustor 6 may be hydrogen (but is not limited to hydrogen). In this regard, in the gas turbine to which this embodiment is applied, even when the fuel is hydrogen, the specific structure of the combustor 6 may be any, for example, a structure that has conventionally used fossil fuels as fuel, and a special configuration as described in the aforementioned patent document is not essential.

[0020] gas turbine control system configuration The control of the gas turbine in Figure 1(A) may be performed by a control device as generally shown in Figure 1(B). The control device may be a computer device having a CPU, ROM, RAM, and input / output port devices interconnected by a bidirectional common bus, and the configuration and operation of each part of this embodiment, which will be described later, may be realized by the operation of the computer device according to a program.

[0021] In the control device, specifically, as shown in Figure 1(B), a turbine operation command unit 50, a load request unit 51, a rotational speed control unit 52, a rotational speed detection unit 53, a load control unit 54, a fuel quantity control unit 55, etc. may be configured. More specifically, the turbine operation command unit 50 may be configured to give control commands to the load request unit 51 and the rotational speed control unit 52 to instruct the operation of the gas turbine based on instructions from the user or requests from any machinery or equipment. The requests or instructions given to the turbine operation command unit 50 may be requests or instructions to operate the gas turbine at a predetermined rotational speed and predetermined load, which may be set as appropriate. The predetermined rotational speed may be, but is not limited to, the "rated rotational speed" set so that the gas turbine rotates stably or efficiently. "Load" is the work given to the load equipment 5 through the turbine shaft 2 of the gas turbine 1, and when the load equipment 5 is a generator, it may be expressed in power units. The "predetermined load" may be, but is not limited to, the "rated load" set so that the gas turbine outputs stably or efficiently.

[0022] The load request unit 51 may be configured to receive a control command from the turbine operation command unit 50, set a target value for the magnitude of the load to be generated by the gas turbine (load target value), and transmit that target value to the load control unit 54. The load target value may be a predetermined load instructed by the turbine operation command unit 50. The rotational speed detection unit 53 may be configured to detect the rotational speed of the turbine shaft 2 using any type of sensor and transmit the detected value to each unit.

[0023] The load control unit 54 may be configured to refer to the load target value from the load request unit 51 and the rotational speed detection value from the rotational speed detection unit 53, determine a requested value (load request value) for the magnitude of the load to be applied to the load equipment at the current turbine rotational speed (rotational speed detection value), within a range that does not exceed the load target value, and send a control command to the load equipment 5 to absorb the work of the load request value.

[0024] In general terms, the rotational speed control unit 52 is configured to refer to control commands from the turbine operation command unit 50, rotational speed detection values ​​from the rotational speed detection unit 53, and load request values ​​from the load control unit 54, and to set a target rotational speed (target rotational speed value) to be reached by the gas turbine based on the control commands from the turbine operation command unit 50, start and stop the starter 60, instruct the fuel quantity control unit to supply fuel, and instruct the igniter 61 to ignite. Here, the rotational speed target value may be a predetermined rotational speed instructed by the turbine operation command unit 50. The starter 60 may also be controlled to start upon receiving an instruction from the turbine operation command unit 50 to start operation and to stop when the igniter is ignited. Specifically, regarding the instruction to supply fuel to the fuel quantity control unit 55, first, the required rotational speed (required rotational speed value) to be generated at the turbine shaft at that moment is determined based on the rotational speed detection value and load request value of the turbine shaft 2, and this required rotational speed value may be given to the fuel quantity control unit 55 as a control command for fuel supply.

[0025] The fuel quantity control unit 55 may be configured to compare the rotational speed detection value with the rotational speed request value and control the amount of fuel supplied from the fuel supply device 9 so that the rotational speed detection value matches the rotational speed request value.

[0026] Relationship between combustion temperature and NOx production As is understood by those skilled in the art, as the combustion temperature of fuel and compressed air in the combustion chamber increases, the amount of NOx produced increases. As shown in Figure 2, the combustion temperature T is highest when the equivalence ratio F / A is the stoichiometric air-fuel ratio (ST), and as the equivalence ratio F / A is lower than the stoichiometric air-fuel ratio (lean: L) or higher than the stoichiometric air-fuel ratio (rich: R), the combustion temperature T decreases and the amount of NOx produced decreases. Therefore, in the operation of a gas turbine, it is desirable to use as little fuel as possible, and in order to suppress NOx production, it is preferable to burn the fuel and compressed air in a lean state with a lower equivalence ratio. In particular, when the fuel is hydrogen, the combustion temperature is high, so in order to suppress NOx production, it is desirable to keep the equivalence ratio as low as possible without misfires.

[0027] Operating conditions when starting up a gas turbine (1) Conventional gas turbine starting operation method As described in the section on the summary of the invention, in the operation method when starting up the gas turbine 1, conventionally, the turbine speed is generally increased to the rated speed (a predetermined speed normally used when operating a gas turbine) under no-load conditions, and then, when the load is increased, the fuel supply is increased while maintaining the rated speed. Specifically, when starting up the gas turbine 1, as illustrated in Figure 3(A), first, the rotation of the turbine shaft 2 is started by the starter 60, and the supply of compressed air a into the combustion chamber 8 begins. The amount of compressed air supplied increases in accordance with the increase in the rotation speed of the turbine shaft 2, unless a mechanism for releasing the flow in the middle of the flow path 7b is provided. When the rotation speed Rpm reaches RS, fuel supply begins, and when the rotation speed Rpm further reaches RF, the igniter 61 is activated, and combustion of fuel and air begins. Subsequently, as shown in the figure, the fuel supply is gradually increased so that the rotational speed Rpm increases until it reaches the rated rotational speed RT, under no-load conditions (when the load equipment 5 is not performing any work). Note that in the figure, the equivalence ratio F / A decreases as the rotational speed Rpm goes from RS to RT because the increase ratio of compressed air is greater than the increase ratio of fuel. After that, when the load equipment 5 is put to work, the fuel supply is increased while maintaining the rated rotational speed RT (P1), and the load is increased until it reaches the rated load (a predetermined load normally used when operating a gas turbine) (P2).

[0028] In the conventional operating method as shown in Figure 3(A) above, the operating state is first brought to the rated speed, no-load state P1, and then transitioned to the rated speed, rated load state P2. Therefore, it is necessary to ensure a sufficient equivalence ratio F / A so that misfires do not occur in the primary combustion field 8a at the rated speed, no-load state P1. That is, the amount of compressed air supplied to the primary combustion field 8a (the amount of compressed air supplied from the supply port 7a) must be kept within a range that does not cause misfires at the rated speed, no-load state P1. Consequently, when the fuel supply is increased to increase the load to the rated load in that state, the equivalence ratio F / A of the primary combustion field 8a increases accordingly, the combustion temperature rises, and the amount of NOx produced increases.

[0029] (2) Operation method for starting the gas turbine of this embodiment The amount of NOx generated under the conditions of a predetermined rotational speed and load (for example, the rated rotational speed and rated load) that are normally used when operating the gas turbine described above can be kept lower if the amount of air supplied to the primary combustion field 8a is increased and the equivalent ratio F / A of the primary combustion field 8a is reduced. In this regard, according to the inventor's research of this embodiment, in a configuration in which the amount of air supplied to the primary combustion field 8a is increased so as to suppress the equivalent ratio F / A of the primary combustion field 8a as much as possible under the operating conditions of a predetermined rotational speed and a predetermined load, when trying to bring the operating condition to a predetermined rotational speed and no load at the start of the gas turbine 1, the equivalent ratio F / A is too low and misfire occurs. However, it has been found that the operating condition of a predetermined rotational speed and a predetermined load can be achieved by starting the operation of the load equipment (increasing the load) after ignition in the combustion chamber 8 and before the rotational speed of the turbine shaft 2 reaches a predetermined rotational speed (for example, at about half the rated rotational speed RT), and then controlling the amount of fuel so that the rotational speed and load become a predetermined load as the rotational speed reaches a predetermined rotational speed. In other words, when starting up the gas turbine 1, instead of first bringing the operating state to a predetermined rotational speed and no load, as in the past, if the load is increased when the rotational speed of the turbine shaft 2 reaches a rotational speed at which a load can be applied (operation of load equipment), and then the operating state is directly brought to a predetermined rotational speed and predetermined load, it becomes possible to further increase the amount of air supplied to the primary combustion field 8a in order to further suppress the equivalent ratio F / A of the primary combustion field 8a in the operating state of predetermined rotational speed and predetermined load.

[0030] Thus, in this embodiment, to put it simply, in the combustor 6, the amount of compressed air supplied to the primary combustion field 8a is increased to a range that satisfies the equivalent ratio F / A that prevents misfires in the primary combustion field 8a under operating conditions of a predetermined rotational speed and predetermined load. When starting the gas turbine 1, the load is increased when the rotational speed of the turbine shaft 2 reaches a rotational speed at which a load can be applied, and the operating state is controlled to transition directly to the predetermined rotational speed and predetermined load state. The increase in the amount of compressed air supplied to the primary combustion field 8a can be achieved, for example, by enlarging the diameter of the compressed air supply port opening to the primary combustion field 8a. In the actual configuration, the amount of compressed air supplied to the primary combustion field 8a at a predetermined rotational speed can be set according to suitability. Preferably, the amount of compressed air supplied to the primary combustion field 8a at a predetermined rotational speed may be set to an amount that provides the lower limit of the equivalence ratio that does not misfire under the predetermined rotational speed and load conditions (it may be somewhat higher than the lower limit of the equivalence ratio that does not misfire, taking into consideration the stability of the control), in order to suppress the amount of NOx generated as much as possible.

[0031] The operation control of the gas turbine 1 at startup according to this embodiment may be specifically performed as shown in Figure 3(B). Referring to the same figure, first, when a command is given to start the gas turbine, the starter 60 starts the rotation of the turbine shaft 2, and the supply of compressed air a into the combustion chamber 8 begins. When the rotational speed Rpm reaches RS, fuel supply begins, and when the rotational speed Rpm further reaches RF, the igniter 61 is activated, and combustion of fuel and air begins. Here, the equivalent ratio until ignition is lower than in the case of Figure 3(A) because the amount of compressed air supplied to the primary combustion field 8a is relatively large. Subsequently, the amount of fuel supplied is increased so that the rotational speed Rpm and the equivalent ratio F / A increase, and when the rotational speed reaches Rx, operation to perform the work of the load equipment begins. After that, as shown by the solid line in the figure, the amount of fuel supplied is increased so that the rotational speed Rpm and the equivalent ratio F / A increase, aiming for a state P3 of a predetermined rotational speed and predetermined load. In the process of starting such a gas turbine, the fuel supply amount may preferably be controlled so that the rotational speed does not decrease from the start of rotation until it reaches a predetermined rotational speed, in order to ensure the rotational stability of the gas turbine. Furthermore, in the control when transitioning the operating state from after ignition to the predetermined rotational speed and predetermined load state P3, the fuel supply amount may be controlled so that the load requirement of the load equipment does not increase rapidly, and the rotational speed increases gradually in accordance with the load requirement. According to this operating method, as shown in the figure, it becomes possible to reduce the equivalence ratio at the predetermined rotational speed and predetermined load state from P2 to P3, and as a result, the amount of NOx generated can be suppressed.

[0032] In the specific control process for starting the gas turbine 1 according to this embodiment, for example, as shown in Figure 4, when the start of the gas turbine 1 is instructed (S0), the starter 60 starts rotating the turbine shaft 2 (S1), and when the rotational speed Rpm reaches RS (S2), fuel supply is started (S3). Here, the fuel supply amount Fq may be gradually increased by an increment ΔF, which may be set as appropriate, until the rotational speed Rpm reaches RF (S4). When the rotational speed Rpm reaches RF (S4), ignition of the fuel-compressed air mixture is performed, the operation of the starter 60 is stopped (S5), and the combustion gas from the combustor 6 produced by combustion rotates the turbine 3, causing the rotational speed Rpm to start to rise. Subsequently, as the fuel supply amount Fq increases, the rotational speed Rpm increases, and when the rotational speed Rpm reaches Rx, which is lower than the target rotational speed (e.g., rated rotational speed) RT, the load Ld is increased until it reaches the target load LT (S8, S9). The load Ld may be gradually increased by an increment ΔL, which may be set as appropriate. Then, the fuel supply amount Fq is increased so that the rotational speed Rpm matches the rotational speed requirement Rpmt(Ld), which is set in accordance with the load Ld (S10) (S11). Here, Rpmt(Ld) may be set so that when the load Ld reaches the predetermined load LT, the predetermined rotational speed RT (= Rpmt(LT)) is reached. In this way, the operating state of the gas turbine is controlled toward the predetermined rotational speed and predetermined load state (S12).

[0033] Thus, in the gas turbine of this embodiment described above, at startup, the load increase begins even before the rotational speed reaches a predetermined speed, and the operating state transitions directly to a predetermined speed and predetermined load state, and operation at a predetermined speed and no load state is not performed. As a result, there is no restriction on the amount of compressed air supplied to satisfy the equivalence ratio that must be ensured to prevent misfires in the predetermined speed and no load state, and it becomes possible to increase the amount of compressed air supplied to prevent misfires in the predetermined speed and predetermined load state, so that the equivalence ratio at the predetermined speed and predetermined load state can be sufficiently reduced, and the amount of NOx generated can be reduced. This embodiment can be used in any type of gas turbine, and it should be understood that a complex structure to prevent combustion concentration unevenness in the primary combustion field is not essential.

[0034] While the above description is made in relation to embodiments of the present invention, many modifications and changes are readily possible for those skilled in the art, and it will be clear that the present invention is not limited to the embodiments illustrated above, but can be applied to various devices without departing from the concept of the present invention.

Claims

1. A gas turbine operated in a predetermined rotational speed and predetermined load operating state in which the rotational speed of the turbine shaft is a predetermined rotational speed and the magnitude of the load acting on the turbine shaft is a predetermined load, A combustor supplied with fuel to be burned and compressed air, wherein the amount of compressed air supplied to the primary combustion field in the combustor when the rotational speed of the turbine shaft is a predetermined rotational speed is such that the equivalent ratio in the primary combustion field is such that misfires do not occur in the operating state, A fuel supply control means for controlling the amount of fuel supplied to the combustor. Load control means for controlling the magnitude of the load acting on the turbine shaft Includes, A gas turbine configured such that, at the start of rotation of the turbine shaft, the fuel supply control means starts supplying fuel to the combustor and ignites it in the combustor, and before the rotational speed of the turbine shaft reaches the predetermined rotational speed, the load on the turbine shaft is increased by the load control means up to the predetermined load, and the equivalent ratio at the predetermined rotational speed and predetermined load operating state is lower than the equivalent ratio at the predetermined rotational speed and predetermined load operating state when the amount of compressed air is the same amount that gives an equivalent ratio that does not cause misfire even at the predetermined rotational speed and predetermined load operating state when the rotational speed of the turbine shaft is the predetermined rotational speed and predetermined load operating state.

2. A gas turbine according to claim 1, wherein the load control means is configured such that the magnitude of the load begins to increase when the rotational speed of the turbine shaft reaches a rotational speed at which the load can act on the turbine shaft.

3. A gas turbine according to claim 1 or 2, wherein the fuel supply control means is configured to control the amount of fuel supplied to the combustor so that the rotational speed of the turbine shaft does not decrease from the start of rotation until it reaches the predetermined rotational speed.

4. A gas turbine according to claim 1 or 2, wherein the amount of compressed air supplied to the primary combustion field in the combustor when the rotational speed of the turbine shaft is the predetermined rotational speed is an amount that makes the equivalent ratio in the primary combustion field the usable lower limit of the equivalent ratio that does not misfire under the operating conditions of the predetermined rotational speed and predetermined load.

5. A gas turbine according to claim 1, wherein the fuel is hydrogen.

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