JPS5948299B2 - Gas turbine fuel switching system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel switching system for a gas turbine that uses different types of fuel.

In recent years, crude oil and residual oil have been increasingly used as fuel for gas turbines, but in general, heavy oil-fired gas turbines have a transport system for light oil such as light kerosene in addition to the heavy oil transport system. Often attached.

The reason is as follows. (1) When crude oil is used, the crude oil contains volatile matter, so when the gas turbine is stopped, the volatile matter from the fuel transfer system is released into the gas turbine. Since there is a risk of leaking into the gas distribution area of the engine and causing sparks or explosions (at the next startup), it is recommended to operate with light oil when starting or stopping 2, and to fill the fuel system with light oil.

(2) When using residual oil, it has a high viscosity, so it is generally heated before use, but when the oil is stopped, the residual oil may cool down and solidify in the system, so at least when it is stopped, light oil should be used. It is a good idea to keep the fuel transfer system filled with light oil while operating the vehicle.

(3) Light oil should also be available as a backup in case the supply of heavy oil is interrupted or trouble occurs in the heavy oil transfer system.

In order to satisfy the above-mentioned demands, a gas turbine fuel switching system that is currently commonly used will be explained with reference to FIG.

In this explanation, for convenience, heavy oil will be referred to as H fuel and light oil will be referred to as L7 fuel.

In the figure, D indicates H fuel storage tank 1 and transfer pump 3.
and a supply D1 having a check valve 7 and equipped with a pressure sensor 11, connecting the downstream side of the transfer pump 3 with the storage tank 1, and from a return line D2 having a pressure regulating valve 5. This is the H fuel transfer system.

E is L fuel storage tank 2, transfer pump 4 and check valve 8
A fuel transfer system consisting of a supply pipe E1 having a pressure sensor 12 and a return pipe E2 connecting the downstream side of the transfer pump 4 and the storage tank 2 and having a pressure regulating valve 6. It is a systematic.

The H fuel system and the L fuel system E are connected to switching valves (
It is connected in parallel to the gas turbine fuel transfer system F via a three-way valve) 9.

Reference numeral 10 denotes a solenoid valve that controls operating air to the switching valve using an external electric signal.

In the gas turbine fuel switching system described above, when the gas turbine is started, the H, IJA, and E transfer pumps 3 and 4 are started in response to the start signal.

At this time of startup, the solenoid valve 10 is held in a demagnetized state, so the switching valve 9 does not operate and the fuel flows into the gas turbine system F.
flows to

In this case, the H fuel flows through the pressure regulating valve 5 and is returned to the tank 1 for circulation.

If the H fuel is a high viscosity fuel oil that requires heating,
Since the Hi fuel is warmed by the circulation operation, it becomes possible to send fuel at a required temperature to the gas turbine fuel transfer system F.

When the startup of the gas turbine is completed and the H fuel becomes usable, a fuel switching signal is issued according to a preset program or an operator's command.

Since the solenoid valve 10 is excited by this fuel switching signal,
The switching valve 9 is switched and H fuel is supplied to the gas turbine fuel transfer system F.

At this time, the L fuel transfer pump 4 is normally operated for backup.

When stopped, the solenoid valve 10 is demagnetized by the stop signal, and the switching valve 9 is switched to the L fuel transfer system side. Therefore, after the gas turbine fuel transfer system F is filled with L fuel by operating with L fuel for a predetermined time, Stop the gas turbine.

Note that the check valves 7 and 8 serve to prevent fuel from temporarily flowing back into one of the fuel transfer systems due to the pressure difference between the two fuel transfer systems and E during the fuel switching.

If, during operation with H fuel, a problem occurs in the fuel transfer system, such as the transfer pump 3 stopping, and fuel cannot be supplied, the pressure detector 11 detects low pressure in the fuel transfer system. When this detection signal demagnetizes the electromagnetic valve 10, the switching valve 9 automatically switches to the L fuel transfer system E, allowing continued operation.

A block diagram of such a control system is shown in FIG.

Conversely, if a problem occurs in the Lm fuel transfer system E and fuel supply becomes impossible, the pressure sensor 12 performs the same operation as described above.

However, in the fuel switching system, if a trouble occurs in the fuel transfer system and the H fuel cannot be transferred while operating with one fuel, for example, the H fuel, as described above, the switching valve 9 ensures that the H fuel is not transferred. Although the switching operation is performed, there is always a time delay (response delay) until the pressure detector 11 detects the pressure drop in the supply pipe D1 and the switching valve 9 operates.

As a result, if the supply of H fuel suddenly stops, the changeover valve 9 will not be switched in time, so fuel will not be supplied to the gas turbine, and there is a risk that the gas turbine will extinguish and trip.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the drawbacks of the prior art and to provide a highly reliable gas turbine fuel switching system that does not cause tripping of the gas turbine.

To achieve this objective, the present invention connects two lines in parallel to the gas turbine fuel transfer system, one line being equipped with a fuel tank, a transfer pump and a check valve, respectively, and the other line being equipped with a fuel tank, a transfer pump and a check valve, respectively. A gas turbine fuel in which the pipes are each provided with a fuel tank for a fuel different from the fuel, a transfer pump, and a check valve, and the different fuels from both pipes are switched and supplied to a gas turbine fuel transfer system. In a switching system, the transfer pump in one line is configured with a pump whose discharge pressure changes depending on the discharge flow rate, and the transfer pump in the other line is configured with a pump whose discharge flow rate is constant regardless of the discharge pressure. The conduit provided with the constant discharge flow rate pump is provided with a return conduit that communicates the upstream side of the check valve with the fuel tank and has a pressure regulating valve, and is provided downstream of the constant discharge flow rate pump. a constriction capable of producing a pressure difference greater than the pressure difference between the set pressure of the pressure regulating valve and the maximum discharge pressure of the transfer pump in the one conduit, and a bypass conduit that communicates the upstream and downstream sides of the constriction; The bypass pipe is provided with a switching valve that is switched by an external signal to guide the upstream pressure or the downstream pressure of the throttle to the pressure supply port of the pressure regulating valve.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, A is the H fuel transfer system, which includes a supply pipe A1 equipped with an H fuel storage tank 21, a transfer pump 23, a throttle and a check valve 27 in that order, and an upstream side of the check valve 27. A return pipe A2 that communicates with the storage tank 21 and has a pressure regulating valve 25; and a bypass pipe A3 that communicates the first stream side and the downstream side of the throttle 30 and has a three-way solenoid valve 31.
It is composed of

B is an L fuel transfer system, which is comprised of F, a supply pipe B1 provided with a fuel storage tank 22, a transfer pump 24, and a check valve 28 in that order.

C is a gas turbine fuel transfer system, to which the H fuel transfer system A and L fuel transfer system B are connected in parallel.

The transfer pump 23 of the H fuel transfer system A is constituted by a pump whose discharge flow rate is constant regardless of the discharge pressure, such as a gear pump.

4. The transfer pump 24 of the fuel transfer system B is constituted by a pump whose discharge pressure changes depending on the discharge flow rate, for example, a centrifugal pump, as shown in FIG.

The set pressure of the pressure regulating valve 25 is set to a value higher than the maximum discharge pressure output of the transfer pump 24 shown in FIG.

When the three-way solenoid valve 31 is energized, it guides the pressure on the downstream side of the throttle 30 to the pressure supply [-1 of the pressure regulating valve 25 , and when demagnetized, it switches to supply the pressure on the upstream side of the throttle 30 to the pressure of the pressure regulating valve 25 . It can be guided to the supply port.

When the three-way solenoid valve 31 is energized, the aperture 30
The opening degree of the pressure regulating valve 250 is adjusted so that the downstream pressure is equal to the set pressure of the pressure regulating valve 25, and the three-way solenoid valve 31
When the pressure is demagnetized, the opening degree of the pressure regulating valve 25 is adjusted so that the pressure of the -I- flow of the throttle 30 becomes equal to the set pressure of the pressure regulating valve 25.

The restrictor 30 allows the discharge amount (constant) of the transfer pump 23 to be fully excited, and the pressure drop due to the restrictor 30 (that is, the pressure difference between the upstream of the restrictor 30 and the downstream side) is equal to the set pressure of the pressure regulating valve 25 and the pump 24. Throttle 3 so that the difference is greater than the minimum discharge pressure difference.
A diameter of 0 is set.

(Since the flow rate through the throttle 30 is constant, a predetermined pressure drop can be given by changing the diameter of the throttle.

) Next, the operation of the fuel switching system constructed as described above will be explained.

When starting up the gas turbine, the three-way solenoid valve 31 is demagnetized to the power that starts the transfer pumps 23, 24 according to the starting signal.

FIG. 5 is a diagram showing the pressure relationship of various parts when the three-way solenoid valve 31 is in a demagnetized state.

When the three-way solenoid valve 31 is demagnetized, the upstream pressure of the throttle 30 is adjusted to be equal to the set pressure.
The upstream pressure becomes the pressure at point A, which is the sum of the pressure drop of the throttle 30 and the pressure caused by the force drop -F due to the resistance of the return pipe A2.

Since the pressure at point A is higher than the set pressure of the pressure regulating valve 25, the valve 25 is fully open, but because of the throttle 30, the discharge pressure of the pump 23 is maintained at the pressure at point A.

On the other hand, the pressure downstream of the throttle 30, that is, upstream of the check valve 27, is at two points.

The pressure at the two points is lower than the pressure at the discharge pressure cover point of the pump 24.

Therefore, the check valve 28 is opened and the fuel flows into the gas turbine fuel transfer system C, and the check valve 27 is kept closed.

The reason why the check valve 27 is kept closed is that the gas turbine fuel transfer system C has a resistor such as a fuel adjustment valve to the gas turbine, and the pressure of the L fuel that has passed through the check valve 28 is maintained in the check valve. 2
This is because it acts on the downstream side of 7.

In this state, all the discharge amount of the transfer pump 23 passes through the return pipe A2 and returns to the H fuel storage tank 21 (2
ing.

Next, when a switching signal to the Hg family is given to the solenoid valve 31, the three-way solenoid valve 31 is energized, and the pressure regulating valve 25 is closed to the throttle 3.
The opening degree of the pressure regulating valve 25 is controlled so that the downstream pressure of 0, that is, the upstream pressure of the check valve 27 becomes equal to the set pressure.

, FIG. 6 is a diagram showing the pressure relationship of each part at this time.

As shown in the figure, the downstream pressure of the throttle 30 becomes the pressure at two points, and becomes equal to the set pressure of the pressure regulating valve 25.

3. The discharge L-F force of the sharpening transfer pump 23 is the pressure at point H, which is the sum of the pressures at two points and the f and fE force drops of the throttle 30.

The pressure at two points, which is the flow pressure of the throttle 30, is the pressure of the transfer pump 2.
Since the pressure at point C, which is the discharge pressure of No. 4, is higher than the pressure at point C, the check valve 27 is in the open state. (also low) acts on the F flow of the check valve 28, and the downstream pressure becomes higher than the pressure at the F-flow pressure point of the check valve 28, so the check valve 28 is closed.

By closing the check valve 28, the pump 24 enters a shut-off operation and its discharge pressure becomes the maximum discharge pressure, which is the pressure at the bottom point.

However, since the pressure at the two points downstream of the throttle 30 is higher, the check valve 28 remains closed.

Therefore, the gas turbine fuel transfer system C has a check valve 2.
H fuel is supplied via 8.

The load on the gas turbine is reduced and the gas turbine fuel transfer C
When the flow rate to the system decreases, the flow rate of the valve 25 increases by the amount of decrease, and the upstream pressure of the check valve 27 maintains the pressure at two points.

FIG. 7 is a diagram summarizing the upstream pressures of the check valves 27 and 28 during operation with the HP8 charge and Lffi charge described above.

When the gas turbine is stopped, the operation opposite to the above is performed, and H
A switch is made from ffi charges to Lg charges.

The control system is shown in a block diagram as shown in FIG.

It is clear that this diagram is significantly simplified compared to FIG.

Next, during operation using H fuel, trouble occurred in the fuel transfer system A, and HP! Considering the case where the supply of fuel No. 8 is stopped, when the pressure on the upstream side of the check valve 27 becomes lower than the pressure on the upstream side of the check valve 28, the switch from the H fuel to the L fuel is instantaneously performed. You will be killed.

Therefore, there is no time delay due to switching, so
There is no risk of turbine I lip caused by fuel shortage as in the conventional case.

As explained above, according to the present invention, it is possible to perform the same function as the conventional technology in normal switching operations, and in the event of trouble in the fuel transfer system, the fuel can be switched immediately even in the event of a momentary fuel cutoff. As a result, there is no risk of turbine tripping due to fuel starvation, and reliability is improved.

Furthermore, not only can the switching valve for switching between the fuel transfer system and the turbine fuel transfer system be omitted, but also the pressure detector of one of the fuel transfer systems can be eliminated, so the control system can be significantly simplified.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional gas turbine fuel switching system, FIG. 2 is a control block diagram of the same fuel switching system, FIG. 3 is a diagram showing an embodiment of the gas turbine fuel switching system of the present invention, and FIG.
The figure is a flow rate-discharge pressure characteristic diagram of the centrifugal pump used in the fuel switching system, Figure 5 is an explanatory diagram showing the pressure relationship of each part in the L fuel supply state, and Figure 6 is the pressure relationship of each part in the H fuel supply state. An explanatory diagram showing H, L! FIG. 8 is a control block diagram according to the present invention. A...H fuel transfer system, B...L chemical transfer system, A,, B,...supply pipe line, A2...
...Return pipe line, A3...Bypass pipe line,
C...Gas turbine fuel transfer system, 21...
...Hi fuel storage tank, 22...L fuel storage tank, 23...Transfer pump (gear pump),
24... Transfer pump (vortex pump), 25...
...Pressure regulating valve, 27.28...Check valve,
30... Throttle, 31... Three-way solenoid valve.

Claims (1)

[Claims] 1 Two pipes are connected in parallel to a gas turbine fuel transfer system, one pipe is equipped with a fuel tank, a transfer pump, and a check valve, and the other pipe is equipped with a fuel different from the above fuel. In a gas turbine fuel switching system, which is equipped with a fuel tank, a transfer pump, and a check valve, and which switches and supplies different types of fuel from both pipes to the gas turbine fuel transfer system, the transfer of one pipe The pump is constituted by a pump whose discharge pressure changes with the discharge flow rate, and the transfer pump in the other pipe line is constituted by a pump whose discharge flow rate is constant regardless of the discharge pressure, and the constant discharge flow rate pump is provided. The pipeline includes a return pipeline that connects the flow side of the check valve L with the fuel tank and has a pressure regulating valve, and a return pipeline that is provided downstream of the constant discharge flow rate pump and that is connected to the set pressure of the pressure regulating valve. A constriction capable of creating a pressure difference between the maximum discharge pressure of the transfer pump in the one conduit and the pressure difference device-1, a bypass conduit that communicates the upstream side and the downstream side of the constriction, and the bypass conduit. 1. A gas turbine fuel switching system, comprising: a switching valve that is installed in a gas turbine and is switched by an external signal to guide the upstream pressure or the downstream pressure of the throttle to the pressure supply of the pressure regulating valve.