JPH01142220A - Fuel controller for gas turbine - Google Patents

Abstract

PURPOSE:To reduce sudden fluctuation of rotational speed of a high pressure shaft, in a device for controlling a fuel quantity supplied from a fuel pump by the opening adjustment of a by-pass valve, by applying a differential arithmetic processing to the opening signal of an extraction valve in an air compressor so as to correct a low pressure shaft rotational speed command signal. CONSTITUTION:In a two-shaft gas turbine, a fuel pump 1 is driven through a gear train 2 by a high pressure shaft 9, and its discharging fuel is burned after being supplied to a combustor 7 together with high pressure air from an air compressor 8, so that the high pressure/high temperature gas generated there is supplied to a high pressure turbine 5 and a low pressure turbine 6 in this order so as to drive load 20 such as a generator or the like. And a fuel flow rate is controlled by adjusting the opening of a by-pass valve 3. In this occasion, two first-order lag opening signals having different time constants are generated on the basis of the opening signal of an extraction valve4, and a low pressure rotational speed correction signal is generated by the difference between both opening signals so as to correct the low pressure shaft rotational speed command signal. Thereby, the opening of the by-pass valve 3 is controlled on the basis of a command signal after the correction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a fuel control device for a gas turbine.

(Prior Art) The prior art will be described with reference to FIGS. 2, 5, and 6. FIG. 2 is a configuration diagram of a two-shaft gas turbine to be controlled. An air compressor 8 takes in air from the atmosphere, compresses it to a predetermined pressure, and supplies combustion air to the combustor 7. The air compressor 8 is directly connected to a high pressure turbine 5 (described later) via high pressure #9, and obtains rotational force from the high pressure turbine 5.

4 is a bleed valve, and when the air compressor 8 is at low speed, this bleed valve 4
This is to prevent the air compressor 8 from entering the surge region by opening and bleeding air. When the rotational speed of the air compressor 8 rises to around the rated rotational speed, the air bleed valve 4 is closed to perform efficient operation. 1 is a fuel pump, which is connected to a high pressure turbine 5 via a high FEi 1119° gear 2.
More rotational power is obtained, and sufficient discharge pressure is obtained to supply fuel to the combustor 7.

The fuel is supplied through a bypass valve 3 that connects the outlet and inlet of the fuel pump 1.
By controlling the opening degree of the combustor 7, the fuel flow rate to the combustor 7 can be adjusted. In the combustor 7, fuel is mixed and burned with air to generate high temperature, high pressure combustion gas. This high-temperature, high-pressure combustion gas is supplied to a high-pressure turbine 5, and the high-pressure turbine 5 obtains rotational power. The combustion gas leaving the high-pressure turbine 5 further enters the low-pressure turbine 6 and provides rotational force to the low-pressure turbine 6. The rotational force of the low pressure turbine 6 is transmitted via the low pressure shaft 10 to a load 20 such as a generator. The rotation speed control during the startup process is performed by the high pressure shaft 9. Control is performed on either one of the low-pressure shafts 10, and the other shafts are not controlled. Now low pressure axis IO
The case where the rotation speed is controlled will be explained with reference to FIG. 101 is a rotation speed command signal of the low pressure shaft 10, 1
03 is a rotational speed signal of the low-pressure shaft 10, and 11 is an adder that takes the difference between the low-pressure shaft rotational speed command signal 101 and the low-pressure shaft rotational speed signal 103 and outputs a low-pressure shaft rotational speed deviation signal 104. 12
is a controller that performs P engineering calculations, and the low pressure shaft rotation speed deviation signal 104
is input, and a control signal 105 for the bypass valve 3 is output.

107 is an opening signal of the bypass valve 3. 13 is an adder that inverts the bypass valve opening degree signal 107 and the bypass valve control signal 105 and calculates the sum, and outputs the operation signal 106 of the bypass valve 3.
Output. While the low-pressure shaft 10 is being accelerated, the low-pressure shaft rotation speed command signal 101 increases in a ramp-like manner. Therefore adder 1
1, the controller 12 generates a positive deviation in the low pressure shaft rotation speed deviation signal 104, which is the output of the bypass valve control signal 1.
Increase 05. Therefore, the bypass valve operation signal 106, which is the output of the adder 13, decreases, the bypass valve 3 moves in the closing direction, the bypass valve opening signal 107 also decreases, and further,
By moving the bypass valve 3 in the closing direction, the fuel flow rate to the combustor 7 increases, so the high pressure turbine 5 and the low pressure turbine 6 are accelerated, and the low pressure shaft rotation speed signal 103 also increases. In this way, the low pressure shaft 10 is stably controlled to the low pressure shaft rotational speed command signal lot.

(Problems to be Solved by the Invention) For the purpose of shortening the start-up time, it is conceivable to close the bleed valve 4 in order to increase the efficiency of the air compressor 8 while the low-pressure shaft 10 is accelerating. However, during acceleration of the low pressure shaft 10, the oil valve 4
When closed, the load on the compressor 8 increases, so the number of revolutions of the high pressure shaft 90 during acceleration temporarily decreases. FIG. 6 shows the opening of the bleed valve and the rotational speed of the high pressure shaft 9° and the low pressure shaft 10 over time on the horizontal axis when the bleed valve 4 is closed during acceleration control of the low pressure shaft 10. As described above, the low-pressure shaft 10 shifts smoothly, but the rotation speed of the high-pressure shaft 9 temporarily decreases.

FIG. 7 shows the operating state of the air compressor 8 at this time, where the horizontal axis represents the flow rate and the vertical axis represents the pressure ratio. Point ■ is the point at which the bleed valve 4 begins to close. When the bleed valve 4 closes, the flow rate of the compressor 8 decreases and the pressure ratio increases.

The rotation speed of the high pressure shaft 9 decreases. Therefore, the operating point of the air compressor 8 is point ! in FIG. It moves towards point ■ and moves in a direction approaching the surge limit.

In some cases, it is conceivable that the point (2) may be exceeded and the surge limit may be further exceeded. Further, since the temperature of the combustor 7 and the inlet temperature of the high-pressure turbine 5 change suddenly, this is not preferable from the viewpoint of the life of the materials.

An object of the present invention is to provide a gas turbine fuel control system that is safe and has a short start-up time, which allows a margin for the surge limit even when the bleed valve 4 is closed during acceleration of the low-pressure shaft 10.

[Structure of the invention]

(Means for solving the problem) In order to solve the above problem, differential calculation processing is performed on the opening degree signal of the bleed valve 4 of the air compressor 8, and this signal is used to command the rotation speed of the low pressure shaft IO. By correcting the signal 101,
This structure is designed to reduce rapid fluctuations in the high-pressure shaft rotation speed.

(Function) According to the above-described gas turbine fuel control device, the operating state of the compressor 8 has a margin with respect to the surge limit, and the temperature of the combustor 7 and the inlet temperature of the high-pressure turbine 5 change gradually. Therefore, it is preferable from the viewpoint of the life of the material.

(Example) FIG. 1 shows an embodiment of a control system according to the present invention.

In FIG. 1, 110 is an opening signal of the bleed valve 4, 14 is a first-order lag calculator with a time constant T, and 15 is a first-order lag calculator with a time constant T2 larger than T1, which is the bleed valve opening signal. 11
0 as input, and the first primary delayed opening signal 111.
A second primary delayed opening signal 112 is output. 16 is an adder which takes the difference between the first primary delayed opening signal 111 and the second primary delayed opening signal 112, and outputs the low pressure shaft rotation speed correction signal 1.
Outputs 13. An adder 17 calculates the difference between the low pressure shaft rotation speed command signal 101 and the low pressure shaft rotation speed correction signal 113 multiplied by the adjustment parameter K, and outputs the low pressure shaft rotation speed correction command signal 102. The rest is the same as the conventional one shown in FIG.

A case will be described in which the control system configured as described above is used. The low pressure shaft rotational speed correction signal 113 has the following transfer function.

X□1o: Value of the bleed valve opening signal 110 Then it returns to zero. Bleed valve opening signal 11O2 when the bleed valve opening signal 110 changes stepwise; first primary delayed opening signal 111. Second
First-order delayed opening signal 112. Low pressure shaft rotation speed correction signal 11
The movement of No. 3 is shown in Figure 4. Actually, the opening signal 1 of the bleed valve 4
10 changes in a ramp-like manner, and the integral time constant at this time is T
o, if T x < T < T 2 , a differential signal can still be obtained as shown in FIG. When the low-pressure shaft rotational speed command signal 101 is corrected using such a signal, the low-pressure shaft rotational speed correction command signal 102 is corrected in the -temporal increasing direction when the bleed valve 4 is closed. Bleed valve 4 of air compressor 8 during acceleration of low pressure shaft ■0
When the control system of the present invention is applied in a closing operation, as shown in FIG. 3, the rotational speed of the low-pressure shaft 10 temporarily increases, and the rotational speed of the high-pressure shaft 9 temporarily decreases. The amount and rate of decrease in the rotational speed of the high-pressure shaft 9 are small and a rapid decrease can be suppressed.

In this way, if the rotation speed of the high-pressure shaft decreases gradually,
Since the operating state of the air compressor 8 has a margin with respect to the surge limit, stable operation is possible even if there is a disturbance for some reason. Furthermore, rapid changes in the temperature of the combustor 7 and the inlet temperature of the high-pressure turbine 5 can be suppressed, which is preferable from the viewpoint of the lifespan of equipment materials.

During this explanation, the signal that is the source of correction is the bleed valve opening signal 110.
However, the same effect can be obtained by using the bleed valve open command signal instead of this signal.

[Effects of the Invention] As described above, according to the present invention, in a two-shaft gas turbine, high-speed startup can be performed safely and stably to close the bleed valve 4 during acceleration of the low pressure shaft A preferred gas turbine fuel control system can be provided.

[Brief explanation of the drawing]

Fig. 1 is a control block diagram of the present invention, Fig. 2 is a gas turbine system configuration diagram, Fig. 3 is a characteristic diagram showing the rotation speed response when the present invention is implemented, and Fig. 4 is a correction circuit of the present invention. 5 is a control block diagram according to the prior art, FIG. 6 is a characteristic diagram showing the rotation speed response according to the prior art, FIG. 7 is a characteristic diagram of the air compressor, and FIG. FIG. 3 is a characteristic diagram showing the ramp response of the correction circuit of the present invention. 1... Fuel pump 2... Gear 3... Bypass valve 4... Bleed valve 5... High pressure turbine 6
...Low pressure turbine 7...Combustor 8...
Air compressor 9...High pressure shaft 1O...Low pressure shaft Agent Patent attorney Nori Chika Ken Yudo Daishi Maru Healthy Congratulations 1 Yako 1 Koro 5 Fantasy B Strange Question 3 Figure 4 Figure 4 Phase 4 Naka

Claims (1)

[Claims] It is equipped with a fuel pump that receives driving force from the high-pressure shaft of a two-shaft gas turbine via a transmission means such as a gear, and a bypass valve that returns a portion of the fuel discharged from the fuel pump to its inlet side. In systems that control the fuel flow rate by changing the speed, differential calculation processing is applied to the opening signal of the air compressor's bleed valve, which is directly connected to the high-pressure shaft. A fuel control device for a gas turbine, characterized in that it reduces rapid fluctuations in high-pressure shaft rotational speed by correcting a command signal.