JP7561682B2 - Gas turbine - Google Patents

Description

The present invention relates to a gas turbine that rotates the turbine using combustion gas generated in a combustor, and in particular to a gas turbine that is less susceptible to ignition failure or ignition delay during start-up.

Patent Document 1 discloses an invention of a method for confirming ignition of a gas turbine. According to this invention, after receiving a tolerance signal related to a gas flow control valve, a fuel supply pressure signal, an igniter signal, and a compressor pressure release signal, an ignition status related to a gas turbine combustor is determined based on changes in each of the above signals that satisfy a predetermined condition, and an ignition status signal is output based on the determined ignition status. According to this invention, it is possible to control a gas turbine system and detect and confirm flame ignition.

Patent Document 2 discloses an invention for a fuel control device for a gas turbine. According to this invention, the first supply line L1 for fuel control is a line that increases along the ignition limit line LM in the ignition region, and the start of fuel supply is delayed compared to when the fuel flow rate is constant, and starts at a higher rotation speed (larger air volume). The time when the first supply line L1 crosses the ignition limit line LM is delayed compared to when the fuel flow rate is constant, and the tolerance (T) for ignition delay of the first supply line L1 is equivalent to when the fuel flow rate is constant. As a result, less fuel is supplied with less air, the total amount of fuel input until ignition is reduced, and conditions are always met for ignition under lean conditions, which reduces unburned and incomplete combustion and reduces black smoke at start-up.

JP 2012-17738 A JP 2013-44263 A

Gas turbines are internal combustion engines that use combustion gases produced in a combustor to rotate a turbine, which rotates a compressor that compresses the air for combustion, and extracts the remaining energy from an output shaft. However, there have been issues with gas turbines, such as poor ignition or delayed ignition during startup, making them unstable to start.

The present invention has been made to solve the problems in the conventional technology described above, and aims to provide a gas turbine with good starting properties that is less susceptible to ignition failure or ignition delay during start-up.

The gas turbine according to claim 1 comprises:
A gas turbine that rotates a turbine by combustion gas generated in a combustor,
a fuel pump for supplying fuel to the combustor;
a nozzle for supplying fuel to an interior of the combustor;
a fuel cutoff valve provided between the fuel pump and the nozzle;
a pressure sensor provided between the fuel cutoff valve and the nozzle;
a control unit that confirms that the pressure of the fuel detected by the pressure sensor before ignition has increased to or above a first threshold value;
a fuel control valve provided between the fuel pump and the fuel cutoff valve,
The control unit is characterized in that it operates the fuel pump before ignition, opens the fuel cut-off valve and the fuel control valve, and after confirming that the pressure detected by the pressure sensor has increased to or above the first threshold value, performs control to close either the fuel cut-off valve or the fuel control valve, or both .

The gas turbine according to claim 2 is the gas turbine according to claim 1,
The nozzles include a main nozzle and a sub-nozzle,
the pressure sensor is provided between the fuel cutoff valve and the sub-nozzle,
The present invention is characterized in that a restriction having a predetermined passage area is provided between the pressure sensor and the sub-nozzle or in the sub-nozzle.

The gas turbine according to claim 3 is the gas turbine according to claim 1 ,
The control unit is characterized in that after closing either the fuel cut-off valve or the fuel control valve, or both, it controls to open the fuel cut-off valve and the fuel control valve after confirming that the rotational speed of the gas turbine has increased to or above a second threshold value.

According to the gas turbine of the first aspect, the control unit can confirm that the fuel piping from the fuel pump to the pressure sensor is filled with fuel before main ignition (see FIG. 2 , details will be described later) based on the pressure detected by the pressure sensor. This makes it possible to prevent poor ignition at start-up due to an inability to supply the required amount of fuel.
Furthermore, by filling the piping with fuel before the main ignition, the pressure in the fuel piping can be increased without delay when the fuel shutoff valve and the fuel control valve are next controlled to open. By sending fuel to the combustor in advance, the fuel is ignited once before the main ignition, and then immediately thereafter, either the fuel shutoff valve or the fuel control valve, or both, are closed to extinguish the flame, thereby creating an environment in the combustor that is easy to ignite, such as by raising the temperature in the combustion chamber and allowing the vaporized fuel to float, and thus enabling reliable ignition at any time. Generally, the higher the rotation speed of a gas turbine at the time of ignition at start-up, the less black smoke is emitted, but ignition at high rotation speeds is likely to be unstable, which can cause poor start-up. This gas turbine eliminates such problems.

According to the gas turbine described in claim 2, the following three effects can be obtained. First, in addition to the main nozzle that supplies fuel for main combustion into the combustor, a sub-nozzle that supplies a small amount of fuel for ignition into the combustor is provided, which can promote ignition at the time of starting. Second, by providing a pressure sensor between the sub-nozzle and the fuel cutoff valve, the pressure of the fuel sent to the sub-nozzle can be detected and it can be ensured that there is fuel in the fuel pipe. Third, by providing a restriction having a predetermined passage area, such as an orifice, between the pressure sensor and the sub-nozzle or inside the sub-nozzle, or by making the outlet of the sub-nozzle a restriction and setting the outlet diameter of the outlet to a predetermined passage area, the relationship between the pressure and the flow rate of the fuel can be made constant. In other words, by setting the passage area of the restriction through which the fuel passes to a predetermined value, the fuel can be managed so that a predetermined flow rate is obtained at a predetermined pressure. This makes it possible to send an optimal amount of fuel for ignition to the combustor, and the fuel can be reliably atomized and sprayed into the combustor.

According to the gas turbine of claim 3 , it is confirmed that the fuel piping from the fuel pump to the pressure sensor is filled with fuel before main ignition, and by controlling the opening of the fuel cutoff valve and the fuel control valve at the time of main ignition, the pressure is immediately increased to the pressure required for ignition, so that the timing of ignition can be set arbitrarily, and black smoke at start-up can be reduced by igniting after the rotational speed of the gas turbine has reached the second threshold value or higher.

FIG. 1 is a schematic configuration diagram of a gas turbine according to an embodiment. 1 is a diagram showing the relationship between the rotation speed of a gas turbine, the opening degree of a fuel control valve, the operating status of each part, and the timing of a command signal, with the horizontal axis representing time, during operation of the gas turbine of an embodiment. FIG. FIG. 1 is a diagram showing an ignition impossible region and other ignition possible regions in the operation of a gas turbine of an embodiment, based on the relationship between the rotation speed of the gas turbine, the fuel oil pressure, and the fuel control valve opening, in which FIG. 1 shows ignition by a conventional gas turbine as a comparative example (conventional (1) example with fuel in the fuel pipe), FIG. 1 shows ignition difficulty by a conventional gas turbine as a comparative example (conventional (2) example without fuel in the fuel pipe), and FIG. 1 shows ignition by a gas turbine of an embodiment. FIG. 1 shows the relationship between the rotation speed of the gas turbine and the exhaust temperature for confirming the ignition state in the operation of a gas turbine of an embodiment.

The overall configuration of a power generating device using a gas turbine according to an embodiment will be described with reference to FIG.
This gas turbine 1 includes a compressor 3 and a turbine 4 attached to a common rotor 2 that is freely rotatable, and a combustor 5 that supplies combustion gas for driving the turbine 4. The combustor 5 is connected to an air passage 9 that guides the compressed air compressed by the compressor 3, and a fuel supply system that supplies fuel. The fuel supply system will be described in detail later. Furthermore, the combustor 5 is provided with an ignition plug 10, which can ignite and burn the mixture of compressed air and fuel supplied to the combustor 5 to generate combustion gas. A thermometer 30 is installed at the outlet of the turbine 4, and it can be confirmed that the exhaust temperature increases due to ignition. The combustor 5 and the turbine 4 are connected by a combustion gas passage 11, and the combustion gas generated in the combustor 5 is guided to the turbine 4 through the combustion gas passage 11, which can be used to rotate the rotor 2. A generator 13 is connected to the rotor 2 via a reduction gear 12 and an output shaft 16. When the gas turbine 1 is driven, the rotational force of the rotor 2 is converted to an appropriate rotational speed by the reduction gear 12, and the generator 13 is driven to obtain electric power. The reducer 12 is connected to a starter 14, which is an electric motor that drives the rotor 2 when the gas turbine 1 is started, and a main pump 23, which will be described later, and is also provided with a rotational speed detection means 15.

Next, the configuration of a fuel supply system connected to the combustor 5 will be described with reference to FIG.
The fuel supply system is composed of a fuel tank 24 for storing fuel, a fuel pump 6 for sending fuel, a fuel control valve 7 for controlling the flow rate of fuel sent from the fuel pump 6, a fuel cutoff valve 8 for opening and closing a flow passage connecting the fuel control valve 7 and the combustor 5 as necessary, and a nozzle for supplying fuel to the combustor 5, and these are connected by a fuel pipe. The fuel stored in the fuel tank 24 is pressurized by the fuel pump 6 and sent to the fuel control valve 7. The fuel pump 6 is driven by a battery (not shown) when the gas turbine 1 is started, and fuel is supplied by a main pump 23 with a motor driven by power obtained from the reduction gear 12 when the gas turbine 1 is operating at the rated rotation speed.

The fuel control valve 7 can continuously and freely adjust the fuel flow rate. The amount of fuel required corresponding to the rotation speed or load of the gas turbine 1 is set based on the test results, and the fuel control valve 7 can continuously adjust the opening based on the command given to the control unit 20 described later, and send the required amount of fuel to the fuel cutoff valve 8. The fuel cutoff valve 8 can send the fuel sent from the fuel control valve 7 to the nozzle at any time, or cut off the supply of the fuel sent from the fuel control valve 7 to the nozzle, by opening and closing at any time. The nozzle is composed of a main nozzle 22 that sends fuel to the combustor 5 after main ignition, and a sub-nozzle 21 that sends ignition fuel to the combustor 5 before main ignition, and is installed at the head of the combustor 5. In addition, a pressure regulating valve 17 is provided upstream of the main nozzle 22 (on the fuel cutoff valve 8 side) to control the pressure of the fuel sent to the main nozzle 22. Between the sub-nozzle 21 and the fuel cutoff valve 8, a pressure sensor 18 is installed upstream of the pipe close to the fuel cutoff valve 8. In addition, an orifice 19 is provided in the sub-nozzle 21 or on the upstream side of the pipe close to the sub-nozzle 21 as a "throttle" that controls the flow of fuel, but as another configuration example, the outlet of the sub-nozzle 21 may be used as an orifice. The diameter of the orifice 19 is determined so that there is a predetermined correspondence between the fuel pressure and the flow rate of the fuel passing through it, and when the pressure sensor 18 detects a predetermined pressure, the orifice 19 sends the fuel at a predetermined flow rate to the sub-nozzle 21.

The power generation device, which is composed of the gas turbine 1 and the generator 13 shown in FIG. 1, is controlled as a whole by a control unit 20 that functions as a fuel control device. That is, as shown in FIG. 1, the fuel pump 6, the fuel control valve 7, the fuel cutoff valve 8, the spark plug 10, the starter 14, the rotation speed detection means 15, etc. are connected to the control unit 20, and the control unit 20 appropriately controls each part of the device, such as the fuel pump 6, the fuel control valve 7, the fuel cutoff valve 8, the spark plug 10, the starter 14, etc., based on the information on the rotation speed obtained from the rotation speed detection means 15, the exhaust temperature from the thermometer 30, information from other sensors not shown, etc., and instructions from the outside, and controls the fuel flow rate to generate power using the gas turbine 1.

Next, an operating state from start-up to rated operation of the gas turbine 1 in this embodiment will be described with reference to FIG.
When a command to start the engine (start command) is received, the control unit 20 starts the starter 14 using the battery to start driving the rotor 2, starts the starting fuel pump 6 using the battery, and starts ignition using the spark plug 10. At the same time, it sends command 1 to the fuel control valve 7 to set the opening of the fuel control valve 7 to a predetermined value and open the fuel cutoff valve 8. Note that the valve opening indicated by command 1 (and command 2, described later) sent to the fuel control valve 7 varies depending on the type and displacement of the gas turbine 1, the type of the fuel control valve 7, etc., and is set appropriately based on test results.

The control unit 20 confirms that the fuel pressure detected by the pressure sensor 18 has reached a predetermined threshold value (hereinafter referred to as the first threshold value) or higher due to the fuel supply from the fuel pump 6. This allows the control unit 20 to confirm that the fuel piping from the fuel pump 6 to the pressure sensor 18 is filled with fuel before main ignition by detecting a pressure equal to or higher than the first threshold value, thereby preventing poor ignition at start-up due to a lack of the required amount (or pressure) of fuel.

Fuel sent from the fuel pump 6 to the orifice 19 via the fuel control valve 7 and the fuel cutoff valve 8 passes through the opening of the orifice 19 and is sent to the sub-nozzle 21. At this point, the pressure control valve 17 is closed so that fuel is not sent to the main nozzle 22 even if the fuel cutoff valve 8 is opened. The first threshold value, which is the reference value of the fuel pressure detected by the pressure sensor 18 and confirmed by the control unit 20, and the diameter of the opening of the orifice 19 differ depending on the type and displacement of the gas turbine 1, and are set to appropriate values in advance based on test results. In this way, the flow rate of fuel supplied to the sub-nozzle 21 can be managed by the fuel with a pressure exceeding the first threshold value detected by the pressure sensor 18 and the orifice 19 with a diameter selected to provide a predetermined flow rate according to the pressure of this fuel, and the optimal amount of fuel for ignition can be sent to the combustor 5.

In the combustor 5, the spark plug 10 is continuously operated and ignites the fuel supplied from the auxiliary nozzle 21 through the orifice 19. This ignition is called pre-ignition in comparison with the later main ignition, because it is performed in advance before the later main ignition. In general, the higher the rotation speed of the gas turbine 1 at the time of ignition at start-up, the less black smoke is emitted. However, ignition at high rotation speeds is likely to be unstable, which can cause starting problems. Therefore, in the embodiment, the temperature inside the combustor 5 is raised by pre-ignition, and an environment that is easy to ignite is created by allowing the vaporized fuel to float, etc., so that main ignition can be reliably obtained even at high rotation speeds. Then, as described below, main ignition is performed after the rotation speed has increased to a certain extent, thereby reducing the generation of black smoke.

Next, when the control unit 20 confirms that the fuel pressure detected by the pressure sensor 18 is equal to or greater than the first threshold, it sends command 2 to the fuel control valve 7 to change the opening of the fuel control valve 7 and close the fuel cutoff valve 8. Closing the fuel cutoff valve 8 extinguishes the pre-ignition. The opening of the fuel control valve 7 by command 2 is smaller than the opening of the fuel control valve 7 by command 1 described above, but since the fuel control valve 7 is already filled with fuel, it is possible to maintain the flow path from the fuel control valve 7 to the fuel cutoff valve 8 in a fuel-filled state by simply supplying a relatively small amount of fuel. In addition, the flow path downstream of the closed fuel cutoff valve 8 is maintained in a fuel-filled state because the control unit 20 has confirmed that the detection value of the pressure sensor 18 is equal to or greater than the first threshold, as described above.

Next, the control unit 20 confirms with the rotation speed detection means 15 that the rotation speed of the gas turbine 1 has increased to N% or more, and then opens the fuel shutoff valve 8, sends fuel from the auxiliary nozzle 21 into the combustor 5, and ignites it. This ignition is called main ignition in contrast to the pre-ignition described above (see Figure 2). The rotation speed N (%) of the gas turbine at which main ignition begins is called the second threshold. By setting the second threshold as large as necessary or as large as possible, main ignition will occur after the rotation speed of the gas turbine 1 has increased, which has the effect of reducing black smoke at startup.

After this, the starter 14, starting fuel pump 6, and spark plug 10 are stopped at an appropriate time, but the main pump 23 linked to the reduction gear 12 continues to supply fuel to the combustor 5 to continue operation. Until the rotation speed reaches 100%, the fuel flow rate is increased by the fuel control valve 7 in accordance with the amount of air, and after the rotation speed reaches 100%, the fuel flow rate is controlled to maintain the rotation speed at 100%.

Figure 3 shows the relationship between the rotation speed (horizontal axis) of the gas turbine and the fuel oil pressure and fuel control valve opening (vertical axis), showing the non-ignitable region (gray-colored region) where ignition is not possible and the other ignitable regions. It also shows graphs showing the changes in rotation speed and fuel oil pressure when main ignition is performed (divisions (a) and (c)) and when main ignition is attempted but fails (division (b)) for the gas turbine 1 of the embodiment (division (c)) and a conventional gas turbine as a comparison example (divisions (a) and (b)). Diagram (d) shows an example of the relationship between exhaust temperature and rotation speed to confirm the ignition state during operation of the gas turbine of the embodiment. The configuration of the fuel supply system of the gas turbine of the comparison example is generally similar to that of the embodiment.

In Figure 3, in the non-ignitable region where the rotational speed is relatively high, ignition is difficult due to the strong flow of compressed air, but ignition is possible even at high rotational speeds as long as there is enough fuel pressure to enter the ignition region, and if ignition occurs at high rotational speeds, there is little black smoke. Conversely, in the ignition region, ignition is possible at relatively low rotational speeds, but black smoke is likely to be generated due to the lack of air.

In the comparative example shown in Figures 3(a) and (b), the fuel control valve 7 and fuel cutoff valve 8 are opened as described in the embodiment, and control to confirm that fuel at a predetermined pressure is present in the flow path between the fuel pump 6 and the pressure sensor 18 is not performed before main ignition. However, even if confirmation is not performed, there are cases where fuel at a pressure above the predetermined value is present in the flow path between the fuel pump 6 and the pressure sensor 18, and cases where there is almost no fuel present and the pressure sensor 18 cannot detect a pressure above the predetermined value.

Figure 3 (a) shows a case where fuel with a pressure equal to or greater than a predetermined value is present in the flow path between the fuel pump 6 and the pressure sensor 18. In this case, when the rotation speed of the gas turbine reaches a predetermined value, the control unit 20 issues an "open" command to the fuel control valve 7 and the fuel cutoff valve 8, and the fuel oil pressure and the fuel control valve opening gradually increase, leading to main ignition. However, in this case, it is not possible to operate the engine by increasing the rotation speed to a desired range before main ignition and reducing the generation of black smoke.

Figure 3(b) shows a case where fuel with a pressure equal to or greater than a predetermined value is not present in the flow path between the fuel pump 6 and the pressure sensor 18. In this case, even if the control unit 20 issues an "open" command to the fuel control valve 7 and the fuel cutoff valve 8 at the same time as in Figure 3(a), the amount of fuel required for main ignition is not present in the flow path between the fuel pump 6 and the pressure sensor 18, so main ignition cannot occur immediately. It takes a certain amount of time for an ignitable amount of fuel to fill the fuel pipe and increase the fuel oil pressure, and compared to the case in Figure 3(a), there is a delay from the "open" command to the time when ignition should occur, and moreover, as shown in the figure, main ignition often fails.

In contrast, in the embodiment shown in FIG. 3(c), before main ignition, the fuel control valve 7 and fuel cutoff valve 8 are opened, and the presence of fuel in the flow path between the fuel pump 6 and the pressure sensor 18 is confirmed by the control unit 20 determining that the pressure detected by the pressure sensor 18 exceeds the first threshold value. Therefore, since the flow path between the fuel pump 6 and the pressure sensor 18 is filled with fuel, when the main ignition operation (resupply of fuel by outputting an "open" command to the fuel control valve 7 and the fuel cutoff valve 8) is performed at the desired rotation speed, the amount of fuel supplied increases and immediately reaches the required amount, resulting in immediate main ignition.

In this way, according to the embodiment shown in FIG. 3(c), the presence of fuel in the flow path between the fuel pump 6 and the pressure sensor 18 is confirmed before main ignition, and since ignition failure or ignition delay is unlikely to occur at start-up, the timing of main ignition can be changed as desired after the confirmation is completed. Therefore, compared to the conventional example shown in FIG. 3(a), ignition can be delayed to a time that the driver considers necessary, as shown by the difference in the timing of the "open" command. The difference between the main ignition of the conventional example shown in FIG. 3(a) and the main ignition of the embodiment shown in FIG. 3(c) is, for example, several percent in rotation speed and several seconds or more in time.

As shown in FIG. 3(d), in the embodiment shown in FIG. 3(c), the exhaust temperature maintains a predetermined value that makes ignition easy even after the pre-ignition flame has been extinguished. After the second threshold is exceeded and an "open" command is output to the fuel control valve 7 and the fuel cutoff valve 8, main ignition is quickly achieved. Thereafter, the exhaust temperature rises steadily as the gas turbine rotation speed increases smoothly.

As described above, according to the gas turbine 1 of the embodiment, the pressure sensor 18 detects that the fuel pipe from the fuel pump 6 to the pressure sensor 18 is filled with fuel before main ignition, so that ignition delays and ignition failures seen in conventional examples due to a lack of fuel can be prevented and starting performance can be improved. In addition, since ignition occurs at a higher rotation speed than in conventional examples, the generation of black smoke can be reduced.

Reference Signs List 1 gas turbine 4 turbine 5 combustor 6 fuel pump 7 fuel control valve 8 fuel cutoff valve 18 pressure sensor 19 orifice 20 control unit 21 auxiliary nozzle 22 main nozzle

Claims (3)

A gas turbine that rotates a turbine by combustion gas generated in a combustor,
a fuel pump for supplying fuel to the combustor;
a nozzle for supplying fuel to an interior of the combustor;
a fuel cutoff valve provided between the fuel pump and the nozzle;
a pressure sensor provided between the fuel cutoff valve and the nozzle;
a control unit that confirms that the pressure of the fuel detected by the pressure sensor before ignition has increased to or above a first threshold value;
a fuel control valve provided between the fuel pump and the fuel cutoff valve,
the control unit operates the fuel pump before ignition, opens the fuel cutoff valve and the fuel control valve, and after confirming that the pressure detected by the pressure sensor has increased to or above the first threshold, performs control to close either the fuel cutoff valve or the fuel control valve, or both . The nozzles include a main nozzle and a sub-nozzle,
the pressure sensor is provided between the fuel cutoff valve and the sub-nozzle,
2. The gas turbine according to claim 1, wherein a restriction having a predetermined passage area is provided between said pressure sensor and said sub-nozzle or in said sub-nozzle. 2. The gas turbine according to claim 1, wherein the control unit performs control to open the fuel cutoff valve and the fuel control valve after confirming that a rotation speed of the gas turbine has increased to a second threshold value or higher after closing either the fuel cutoff valve or the fuel control valve, or both .

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