JP3960814B2 - Gas turbine equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas turbine apparatus, and more particularly to a control technique for preventing an operating gas turbine engine from exceeding an upper limit speed and causing an overspeed trip.
[0002]
[Prior art]
A gas turbine engine includes a turbine rotatably mounted via a rotating shaft, a combustor for generating combustion gas, a fuel control valve for adjusting a fuel supply amount to the combustor, and air for compressing air. And a compressor.
[0003]
In the above configuration, the fuel adjusted by the fuel adjustment valve and the air compressed by the air compressor are supplied to the combustor, and an air-fuel mixture of the compressed air and the fuel is formed in the combustor. The air-fuel mixture is combusted in the combustor to generate combustion gas, and the combustion gas is supplied to the turbine so that the turbine rotates at high speed. A generator is attached to one end of the rotating shaft, and power is generated by driving the generator with a turbine via the rotating shaft.
[0004]
In such a gas turbine device, various operation controls such as start-up control or constant speed operation control are performed by controlling the valve opening of the fuel control valve. For example, when supplying generated power, the valve opening of the fuel control valve is adjusted in accordance with the load state while operating at a predetermined rated speed, and thus generated power corresponding to the amount of fuel combustion energy is supplied. . That is, when the supply amount of generated power is large, the valve opening degree of the fuel control valve is increased, and conversely, when the generated power amount is small, the valve opening degree of the fuel control valve is decreased. As a result, the rotational speed of the gas turbine is kept substantially constant.
[0005]
[Problems to be solved by the invention]
However, the engine load may suddenly lighten during operation at the constant speed. In such a case, the rotational speed of the gas turbine increases, and depending on the degree of the increase, the upper limit speed is reached, and an overspeed trip may be activated to stop the engine operation. On the other hand, when an overspeed trip occurs, it is necessary to inspect the inside of the engine and the like, which greatly impedes the operation of the gas turbine device.
[0006]
The present invention has been made in view of such conventional problems, and is a gas turbine that can reliably prevent an operating speed of a gas turbine from exceeding a predetermined upper limit speed and causing an overspeed trip. The object is to provide an apparatus.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a gas turbine apparatus according to the present invention is a gas turbine engine that rotates and drives a gas turbine by mixing and burning air and fuel. A coordinate system with the rotation speed and acceleration as axes is provided, and a boundary line in which the acceleration decreases as the rotation speed of the gas turbine increases is set in the coordinate system, and a region where the acceleration is larger than the boundary line is set. the gas turbine engine is set as a region likely to cause overspeed trip, the rotational speed and acceleration of the gas turbine during operation enters the region, that it has to stop the supply of fuel Features.
[0008]
In the gas turbine apparatus control method of the present invention, a coordinate system having the rotation speed and acceleration of the gas turbine as axes is provided, and a boundary where the acceleration decreases as the rotation speed of the gas turbine increases in the coordinate system. set the line, the region acceleration is greater than the boundary line, the gas turbine engine is a region likely to cause the overspeed trip to set, monitor the rotational speed and acceleration of the gas turbine during operation Then, when the rotational speed and the acceleration reach the region, the fuel supply to the engine is stopped.
[0009]
According to the present invention configured as described above, an overspeed trip can be predicted from a combination of rotational speed and acceleration during operation, thereby completely preventing the overspeed trip by shutting off the fuel supply. can do. That is, for example, when an acceleration of a predetermined value or more is present during operation at the rated speed, it can be predicted that the trip speed will be reached due to the overshoot of the rotational speed. Therefore, by cutting off the fuel supply at that time, the rotational speed of the gas turbine can be rapidly reduced. Thereby, an overspeed trip can be reliably prevented.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a gas turbine apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing the overall configuration of the gas turbine apparatus of the present embodiment.
[0011]
As shown in FIG. 1, a gas turbine apparatus according to the present embodiment includes a turbine 1, a generator 5 that is rotated and driven by the turbine 1, a combustor 2 that supplies combustion gas to the turbine 1, and a combustor 2. The fuel adjustment valve 8 that adjusts the amount of fuel supplied to the fuel, the air compressor 3 that supplies compressed air to the combustor 2, and the heat of the combustion gas that has been supplied to the turbine 1 add compressed air. A regenerative heat exchanger 4 for heating and a control device 10 for controlling the turbine 1 are provided.
[0012]
The turbine 1 has a plurality of rotating blades (not shown) for receiving fluid and rotating, is housed in a casing (not shown), and is rotatably supported via a rotating shaft 6. The air compressor 3 is configured to be driven by the turbine 1 via the rotating shaft 6 to compress air. The air compressor 3 is connected to the combustor 2 through a pipe 7, and the air compressed by the air compressor 3 is supplied to the combustor 2 through the pipe 7. A regenerative heat exchanger 4 is installed in the middle of the pipe 7 so that the compressed air exiting the air compressor is heated by the regenerative heat exchanger 4 and then supplied to the combustor 2. It has become.
[0013]
The fuel control valve 8 is disposed upstream of the combustor 2, and fuel supplied from a fuel supply source (not shown) passes through the fuel control valve 8 and is then supplied to the combustor 2. The fuel adjustment valve 8 is configured such that the opening degree of the valve is variable, and the amount of fuel supplied to the combustor 2 is adjusted by operating the opening degree of the valve. Further, a fuel cutoff valve 9 is provided, and when an emergency stop of the engine is necessary, the fuel cutoff valve 9 can be immediately closed to shut off the fuel supply.
[0014]
The fuel and compressed air supplied to the combustor 2 form an air-fuel mixture in the combustor 2. The air-fuel mixture is ignited by an unillustrated ignition plug in the combustor 2 to generate high-temperature and high-pressure combustion gas. The combustion gas is supplied to the turbine 1 to rotate the turbine 1 at a high speed.
A generator 5 is connected to the end of the rotating shaft 6, and power is generated by the generator 5 being driven to rotate at high speed by the turbine 1 via the rotating shaft 6.
[0015]
The gas turbine device includes various sensors, and the control device 10 controls the valve opening degree of the fuel control valve 8 based on these signals. The rotation sensor 12 detects the speed of the rotation shaft, and the valve opening degree of the fuel control valve is feedback-controlled so that the rotation speed becomes constant during constant speed operation. Further, when the gas turbine device is started, the valve opening of the fuel control valve is similarly feedback-controlled so that the acceleration obtained by differentiating the detected rotational speed becomes a predetermined value. An exhaust gas temperature (EGT) sensor 13 is provided in the exhaust part of the combustion gas of the gas turbine, and the temperature of the combustion exhaust gas discharged from the turbine is measured. The fuel control valve 8 is controlled so that the temperature does not rise excessively.
[0016]
FIG. 2 shows a control device according to an embodiment of the present invention. This control device includes a rotational speed (NR) control 21, an exhaust gas temperature (EGT) control 22, an acceleration (ACC) control 23, etc. as the first stage control selection (LSS), and most of them are opened. Select a lesser one. Further, as the second stage selection (HSS), the higher valve opening degree between the result of the first stage selection and the other control is selected and output to the fuel control valve (FCV).
[0017]
Further, this apparatus includes an overspeed trip prediction calculation unit 27 and a fuel cutoff valve control 25, and the possibility that the gas turbine apparatus will cause an overspeed trip is predicted from the relationship between the rotational speed and the acceleration during operation. When entering the region, the fuel cutoff valve 9 is immediately closed to prevent an overspeed trip.
[0018]
The rotational speed (NR) control 21, the exhaust gas temperature (EGT) control 22, and the acceleration (ACC) control 23 are feedback control by a PID computing unit, respectively, and control in which the measurement value detected by the sensor approaches the set value is performed. . The rotational speed (NR) control 21 is control in which, for example, the set value is the rated operation speed and the rotational speed is constant. Accordingly, when the engine load increases or decreases, the rotational speed increases or decreases. Correspondingly, the valve opening degree of the fuel control valve (FCV) increases or decreases, the fuel supply amount is adjusted, and the rotational speed is returned to the set value. . That is, as the engine load decreases, the rotational speed increases, so that the valve opening of the fuel control valve (FCV) is output from the PID calculator so that the difference from the set value becomes small. When the valve opening of the fuel control valve (FCV) increases, the fuel supply amount increases, and the rotational speed increases to return to the original set rotational speed. As a result, when the load on the engine decreases, the rotational speed once increases, and thereafter, a so-called overshoot that decreases and returns to the original speed occurs.
[0019]
The exhaust gas temperature (EGT) control 22 and the acceleration (ACC) control 23 are controls used when starting the gas turbine apparatus. The gas turbine is rotated by a motor at a relatively low speed, and the ignition speed is set after ignition. This is mainly used when the engine speed increases to a predetermined speed. The exhaust gas temperature (EGT) control 22 is a control for adjusting the fuel control valve (FCV) so that the combustion exhaust gas temperature becomes a predetermined value at that time. The acceleration (ACC) control 23 is a control for opening the fuel control valve (FCV) so that the acceleration becomes a predetermined value at that time.
[0020]
FIG. 3 shows an example of fluctuations in the rotation speed when the engine load suddenly decreases. The solid line in the figure indicates, for example, a state where the load is halved. In this case, the rotational speed increases due to a decrease in the load, but the rotational speed (NR) control 21 described above operates and the valve opening of the fuel control valve decreases so that the rotational speed becomes a constant value. As a result, the amount of fuel supplied decreases, and the rotational speed once increased decreases and returns to the original constant speed when the required time elapses. When this load is suddenly reduced, the rotational speed rapidly increases as shown in the figure, and an acceleration indicated by the inclination of the tangent line A (hereinafter referred to as acceleration A) appears.
[0021]
In addition, when the engine load is sharply reduced, for example, as shown by a dotted line in the figure, the rotational speed of the gas turbine rapidly increases as shown by a dotted line. The acceleration B at this time is larger than the acceleration A. Accordingly, the overshoot magnitude b at the acceleration B is larger than the overshoot magnitude a at the acceleration A.
[0022]
If the trip speed that defines the upper limit speed of the engine is set at the position in the figure, an overspeed trip occurs in the case of acceleration B. When an overspeed trip occurs, the generator output is cut off, the fuel supply to the engine is stopped, and the operation of the gas turbine device is forcibly stopped. Furthermore, not only the operation of the gas turbine device is stopped, but also the inside of the engine needs to be inspected, which is very troublesome. Therefore, a gas turbine device that can be operated at the full upper limit speed without causing an overspeed trip is preferable.
[0023]
FIG. 4 shows a configuration example of a control device (overspeed trip prediction calculation unit 27) for preventing the above-described overspeed trip. In this control device, a coordinate system having the vertical and horizontal axes of the rotational speed and acceleration of the gas turbine is provided, and a region K where the gas turbine engine can be predicted to cause an overspeed trip is arranged, and this is indicated by diagonal lines in the figure. Show. In this coordinate system, the horizontal axis is the rotation speed, and the vertical axis is the acceleration. As shown in FIG. 3, the magnitudes a and b of the rotational speed overshoot can be measured from the magnitudes A and B of the acceleration when the load is suddenly reduced (t ₁ ).
[0024]
That is, there is an acceleration β that can be predicted from the characteristics and load characteristics of the target gas turbine device to cause an overshoot that may reach the trip speed during operation at the rotational speed α. As the rotational speed α increases, the acceleration β predicted to reach the trip speed decreases. Therefore, a region K in which the possibility of an overspeed trip of the gas turbine engine can be predicted can be arranged in the coordinate system with the rotation speed and acceleration of the gas turbine as axes as shown in FIG. The region K is wider than the acceleration β with some margin.
[0025]
Further, as shown in FIG. 4, even when the acceleration is almost zero, the rotational speed may gradually increase and approach the trip speed. Also in this case, if the speed γ causing the overspeed trip is exceeded, it is necessary to stop the fuel supply immediately and temporarily stop the engine operation. For this reason, the region in which the possibility of an overspeed trip in FIG. 4 can be predicted includes a region where the acceleration is zero.
[0026]
This gas turbine apparatus includes a rotation speed sensor 12 and can constantly monitor the rotation speed of the rotation shaft, and can always monitor the acceleration obtained by differentiating the rotation speed. Therefore, for example, if there is a sudden decrease in load at time t ₁ , the rotational speed of the rotary shaft increases, but the gas turbine apparatus shown in FIG. 4 causes an overspeed trip due to the magnitude of the rotational speed and acceleration at this time. It is determined whether or not the region K can be predicted.
[0027]
In this control device, a fuel cutoff valve 9 is provided. Accordingly, when the gas turbine apparatus shown in FIG. 4 enters the region K where the possibility of causing an overspeed trip can be predicted from the magnitude of the rotational speed and acceleration of the gas turbine apparatus, the fuel cutoff valve control 25 immediately performs the cutoff valve. 9 is closed to stop the fuel supply. As a result, the supply of combustion gas to the engine is cut off, the rotation speed starts to decrease, and an overspeed trip can be avoided.
[0028]
FIG. 5 shows an operation example of this control apparatus. For example, a gas turbine system during operation at rated speed is the load suddenly decreases at time t _1. When the degree of sudden decrease in the load is small, the acceleration at this time does not enter the region K where there is a high possibility of causing a trip. Control action is performed. When the degree of sudden decrease of the load is large and the acceleration detected at this time enters the region K where it is predicted that an overspeed trip will occur, the fuel cutoff valve 9 is shut off at the time of this detection, and the fuel to the engine The supply of is immediately stopped. As a result, the rotational speed decreases rapidly, and an overspeed trip can be avoided.
[0029]
When the rotational speed decreases and returns to the original rotational speed (for example, the rated rotational speed), this may be detected and the cutoff of the fuel cutoff valve may be released. As a result, fuel is supplied from the fuel control valve, and the original PID control with a constant rotational speed is performed. As a result, even if there is an acceleration at which an overspeed trip is predicted when the load is suddenly reduced, it is possible to continue the operation safely without causing an overspeed trip without causing an overshoot of the rotational speed. Note that the engine may be stopped as it is, as indicated by a dotted line in the figure.
[0030]
According to the control device described above, when entering the region K where the possibility that the rotational speed and acceleration may cause an overspeed trip is entered, the shutoff valve is immediately closed and the fuel supply is stopped. Can be prevented. Therefore, it becomes possible to operate at the full upper limit speed of the gas turbine apparatus, and the ability of the gas turbine apparatus can be fully exhibited.
[0031]
In addition, the gas turbine apparatus of this invention is not limited only to the above-mentioned illustration example, Of course, it can add various changes within the range which does not deviate from the summary of this invention.
[0032]
【The invention's effect】
As described above, according to the present invention, it is possible to reliably prevent an overspeed trip and to provide a gas turbine apparatus having high stability and reliability.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall configuration of a gas turbine apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a configuration example of a control device in FIG. 1;
FIG. 3 is a diagram illustrating the relationship between rotational speed overshoot and acceleration.
FIG. 4 is a diagram illustrating a region K in which a possibility that the gas turbine apparatus may cause an overspeed trip is predicted, in which the horizontal axis indicates the rotation speed and the vertical axis indicates the acceleration.
FIG. 5 is a diagram showing an operation example of the gas turbine apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Turbine 2 Combustor 3 Air compressor 4 Regenerative heat exchanger 5 Generator 6 Rotating shaft 7 Piping 8 Fuel control valve 9 Fuel shut-off valve 10 Control device 12 Rotation sensor 13 EGT sensor 21 Rotational speed (NR) control 22 Exhaust gas temperature ( EGT) control 23 acceleration (ACC) control 25 fuel cutoff valve control 27 overspeed trip prediction calculation unit

Claims (3)

In a gas turbine engine that rotates and drives a gas turbine by mixing air and fuel and burning,
The control device is provided with a coordinate system with the rotational speed and acceleration of the gas turbine as axes, and a boundary line is set in the coordinate system so that the acceleration decreases as the rotational speed of the gas turbine increases. the region acceleration is greater than the line, the gas turbine engine is set as a region likely to cause overspeed trip, the rotational speed and acceleration of the gas turbine during operation enters the area, the fuel supply A gas turbine apparatus characterized by stopping the operation.   The region in which the gas turbine engine is likely to cause an overspeed trip is a region where the rotational speed is predicted to exceed the trip speed due to overshoot from the relationship between the rotational speed and acceleration of the gas turbine. The gas turbine apparatus according to claim 1, wherein In a gas turbine engine that rotates and drives a gas turbine by mixing air and fuel and burning,
A coordinate system with the rotation speed and acceleration of the gas turbine as axes is provided, and a boundary line is set in the coordinate system so that the acceleration decreases as the rotation speed of the gas turbine increases, and the acceleration is higher than the boundary line. a large area, the gas turbine engine is configured to have a region with a high possibility of causing an overspeed trip, monitors the rotational speed and acceleration of the gas turbine during operation, the rotational speed and the acceleration is the area When the fuel gas reaches the engine, the supply of fuel to the engine is stopped.

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