A parking fuel return mechanism, a fuel system and a gas turbine

Abstract

The present invention provides a parking fuel return mechanism, a fuel system and a gas turbine. The parking fuel return mechanism includes: a switching member; a parking fuel return valve, including a second pressure flow path and a third pressure flow path; wherein, the switching member is fixedly connected to the parking fuel return valve and acts on the parking fuel return valve to generate a switching force, the second pressure flow path is connected to the second pressure source, and the third pressure flow path is connected to the third pressure source; the fuel return mechanism has a first state and a second state. The beneficial effect of the present invention is that the fuel flow path is switched by the pressure difference between the first pressure source of the fuel system and the pressure generated by the switching member, relying on the structure of the fuel system and the parking fuel return mechanism itself, without the need for other pressure sources, with a light weight, which can reduce the overall weight of the fuel system and improve the thrust-to-weight ratio of the engine.

Description

Technical Field

[0001] The present invention relates to the technical field of aeroengine control, and particularly to a parking fuel return mechanism, a fuel system and a gas turbine. Background Art

[0002] The principle of a traditional aeroengine fuel system is as Figure 1 shown, which mainly consists of a low-pressure pump 1, a high-pressure pump 2, a return oil pressure reducing valve 11, a differential pressure valve 10, a metering valve 9, a high-pressure shut-off valve 5, a distribution valve 6, a first nozzle 7, a second nozzle 8, a constant pressure valve 3, an actuating mechanism 4, etc. Among them, the metering structure is the main mechanism for supplying power fuel to the engine. After the fuel supply is pressurized by the low-pressure pump 1, it flows to the high-pressure pump 2, and then is increased to the pressure required by the system by the high-pressure pump 2 to become high-pressure oil. The high-pressure oil is metered by the metering valve 9 and then flows through the opened high-pressure shut-off valve 5 to the fuel nozzle, where it is atomized and sprayed into the combustion chamber for combustion. The metering valve 9 is used to meter the fuel quantity flowing into the engine combustion chamber; the high-pressure shut-off valve 5 is used to maintain a sufficient minimum servo pressure in the system and cut off the fuel supply to the engine combustion chamber after the engine stops; the differential pressure valve 10 is used to ensure a constant pressure difference before and after the metering valve 9, and the metering fuel flowing into the combustion chamber can be controlled by the constant pressure difference control and the position of the metering valve; the return oil pressure reducing valve 11 is used to return the fuel provided by the high-pressure pump 2 that is more than the engine combustion demand to the front of the high-pressure pump 2. The distribution valve 6 is used to improve the atomization effect of the fuel nozzle. When the flow rate in the combustion chamber is small, the fuel is supplied to some nozzles of the combustion chamber, and when the flow rate in the combustion chamber is large, the fuel is supplied to all nozzles of the combustion chamber. After the engine stops, the high-pressure pump 2 and the low-pressure pump 1 stop working, the metering valve 9 and the high-pressure shut-off valve 5 are closed, the metering fuel flow path 12 is in a static state and no longer supplies fuel to the combustion chamber. There is still residual fuel in the pipeline from the high-pressure shut-off valve 5 to the distribution valve 6, the annular pipeline behind the distribution valve 6, and the elbow connecting the annular pipeline and the nozzle. The pipeline from the high-pressure shut-off valve 5 to the distribution valve 6 and the annular pipeline behind the distribution valve 6 are called the fuel manifold, and the elbow connecting the annular pipeline and the nozzle is called the fuel manifold.

[0003] According to the usage and test experience of aeroengines, when the engine runs in a steady state for a long time, the internal fuel flow path and the internal and external bypass air paths of the engine reach thermal equilibrium. When the engine stops, during the process of the engine transitioning from a hot state to a cold state, the fuel manifold and the manifold will be radiated by the residual heat of the combustion chamber and the temperature will rise. The residual fuel inside them expands due to heat, resulting in an increase in the pressure inside the pipes. When the nozzle orifice cannot withstand the pressure, the fuel will flow into the combustion chamber, which does not meet the requirements of airworthiness regulations.

[0004] In existing engines, a fuel collection device is provided on the fuel metering fuel flow path 12 of certain models to collect the fuel generated due to expansion after shutdown, avoiding the fuel flowing into the combustion chamber. However, this structure will increase the weight of the engine fuel system and reduce the engine economy. Summary of the Invention

[0005] The object of the present invention is to provide a shutdown fuel return mechanism.

[0006] Another object of the present invention is to provide a fuel system.

[0007] Another object of the present invention is to provide a gas turbine.

[0008] A shutdown fuel return mechanism according to one aspect of the present invention is used for the fuel system of a gas turbine. The fuel system includes a first pressure source, a second pressure source, and a third pressure source. The shutdown fuel return mechanism includes: a switching member; a shutdown fuel return valve, including a second pressure flow path and a third pressure flow path; wherein, the switching member is fixedly connected to the shutdown fuel return valve and acts on the shutdown fuel return valve to generate a switching force. The second pressure flow path is connected to the second pressure source, and the third pressure flow path is connected to the third pressure source; the fuel return mechanism has a first state and a second state: in the first state, the force exerted by the first pressure source on the shutdown fuel return valve is greater than the switching force, and the second pressure flow path is communicated; in the second state, the force exerted by the first pressure source on the shutdown fuel return valve is less than the switching force, and the third pressure flow path is communicated.

[0009] In one or more embodiments of the shutdown fuel return mechanism, the switching member is an elastic member, and the generated switching force is an elastic force.

[0010] In one or more embodiments of the shutdown fuel return mechanism, both ends of the second pressure flow path respectively have a second pressure input port and a second pressure output port, and the second pressure input port is connected to the second pressure source; both ends of the third pressure flow path respectively have a third pressure input port and a third pressure output port, and the third pressure input port is connected to the third pressure source.

[0011] In one or more embodiments of the shutdown fuel return mechanism, a check valve is provided at the third pressure input port. When the third pressure generated by the third pressure source is greater than the set value of the check valve, the check valve opens.

[0012] A fuel system according to another aspect of the present invention, the fuel system includes the parking fuel return mechanism as described above, as well as a low-pressure pump, a high-pressure shut-off valve, and a distribution valve. The low-pressure pump is connected to the third pressure output port of the third pressure flow path, and the high-pressure shut-off valve is connected to the second pressure input port of the second pressure flow path. The fuel system has a first state and a second state: in the first state, the force exerted by the first pressure source on the parking fuel return valve is greater than the switching force, the second pressure output port of the second pressure flow path is connected to the distribution valve, and the second pressure flow path is communicated; in the second state, the force exerted by the first pressure source on the parking fuel return valve is less than the switching force, the third pressure input port of the third pressure flow path is connected to the distribution valve, and the third pressure flow path is communicated.

[0013] In one or more embodiments of the fuel system described above, the first pressure source is the system pressure, the high-pressure shut-off valve generates the second pressure source, and the fuel in the fuel manifold and the manifold generates the third pressure source.

[0014] In one or more embodiments of the fuel system described above, the fuel system includes a nozzle, and the nozzle is connected to the distribution valve.

[0015] In one or more embodiments of the fuel system described above, the nozzle has a check valve.

[0016] In one or more embodiments of the fuel system described above, the first state is normal operation, and the pressure and force conditions are such that the pressure Pn at the nozzle of the fuel system is less than the second pressure Pfm generated by the second pressure source, the pressure Pb at the low-pressure pump is less than the system pressure Pcb generated by the first pressure source, and the force Npcb exerted by the first pressure source on the parking fuel return valve is greater than the switching force Nt generated by the switching member; the second state includes an initial second state, which is just after parking, and the pressure and force conditions are such that the pressure Pn at the nozzle of the fuel system is greater than the third pressure Pm generated by the third pressure source and greater than the pressure Pb at the low-pressure pump, the pressure Pb at the low-pressure pump is approximately equal to the system pressure Pcb generated by the first pressure source and approximately equal to the fuel supply pressure of the fuel pump of the fuel system, which is greater than the opening pressure Py of the one-way valve at the third pressure input port, and the force Npcb exerted by the first pressure source on the parking fuel return valve is less than the switching force Nt generated by the switching member; the second state further includes a final second state, which is complete parking, and the pressure and force conditions are such that the pressure Pn at the nozzle of the fuel system is greater than the third pressure Pm generated by the third pressure source and greater than the opening pressure Py of the one-way valve at the third pressure input port and greater than the pressure Pb at the low-pressure pump, the pressure Pb at the low-pressure pump is approximately equal to the system pressure Pcb generated by the first pressure source and approximately equal to zero, and the force Npcb exerted by the first pressure source on the parking fuel return valve is less than the switching force Nt generated by the switching member.

[0017] A gas turbine according to another aspect of the present invention includes a combustion chamber and further includes the fuel system as described above for supplying fuel to the combustion chamber.

[0018] In one or more embodiments of the gas turbine described above, the gas turbine has a first state and a second state: in the first state, the gas turbine is operating and the second pressure flow path is connected to supply fuel to the combustion chamber; in the second state, the gas turbine is parked and the third pressure flow path is connected to prevent the fuel system from returning fuel.

[0019] The beneficial effects of the present invention are as follows:

[0020] The fuel flow path is switched by the pressure difference between the first pressure source and the switching member of the fuel system. Relying on the structure of the fuel system and the parking fuel return mechanism itself, no other pressure source is required, the weight is light, the overall weight of the fuel system can be reduced, and the thrust-to-weight ratio of the engine can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other features, properties, and advantages of the present invention will become more apparent from the following description in conjunction with the accompanying drawings and embodiments, in which the same reference numerals always represent the same features. It should be noted that these drawings are only examples and are not drawn under the condition of equal scale, and should not be used to limit the actual scope of protection required by the present invention, where:

[0022] Figure 1 is a schematic diagram of a typical aviation engine fuel system.

[0023] Figure 2 is a schematic structural diagram of a parking fuel return mechanism in the first state of an embodiment.

[0024] Figure 3 is a schematic structural diagram of a parking fuel return mechanism in the initial second state of an embodiment.

[0025] Figure 4 is a schematic structural diagram of a parking fuel return mechanism in the final second state of an embodiment.

[0026] Reference numerals:

[0027] 1 - low-pressure pump, 2 - high-pressure pump, 3 - constant pressure valve, 4 - actuating mechanism, 5 - high-pressure shut-off valve, 6 - distribution valve, 7 - first nozzle, 8 - second nozzle, 9 - metering valve, 10 - differential pressure valve, 11 - fuel return pressure reducing valve, 12 - metered fuel flow path, 13 - servo fuel flow path;

[0028] 14 - first pressure source, 15 - second pressure source, 16 - third pressure source;

[0029] 601 - distribution valve, 602 - switching member, 603 - high-pressure shut-off valve, 604 - parking fuel return valve, 605 - nozzle, 606 - fuel manifold and manifold, 609 - low-pressure pump;

[0030] 607 - third pressure flow path, 6071 - third pressure input port, 6072 - third pressure output port, 608 - second pressure flow path, 6081 - second pressure input port, 6082 - second pressure output port. Detailed embodiments

[0031] Reference will now be made in detail to various embodiments of the present invention, examples of which are shown in the accompanying drawings and described as follows. Although the present invention will be described in conjunction with exemplary embodiments, it should be understood that this specification is not intended to limit the present invention to those exemplary embodiments. On the contrary, the present invention is intended to cover not only these exemplary embodiments, but also various alternative forms, modifications, equivalents and other embodiments that may be included within the spirit and scope of the present invention as defined by the appended claims.

[0032] In the following description, the "bottom surface", "upper", "lower" or other orientation terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention. At the same time, specific terms are used in this application to describe the embodiments of this application. For example, "one embodiment" and / or "an embodiment" mean a certain feature, structure or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that the "one embodiment" or "an embodiment" mentioned twice or more at different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures or characteristics in one or more embodiments of this application can be appropriately combined.

[0033] It should be explained that the "pressure" such as the second pressure, the third pressure, the system pressure, the opening pressure, the high-pressure, the low-pressure, etc. described in the following embodiments refers to the pressure, and its unit is Pa. The gas turbine takes an aeroengine as an example in the following embodiments, but is not limited thereto, and the following embodiments can also be applied to occasions such as ground gas turbines and marine gas turbines.

[0034] Figure 1Shown is a typical aeroengine fuel system, which mainly includes a low-pressure pump 1, a high-pressure pump 2, a constant-pressure valve 3, an actuating mechanism 4, a high-pressure shutoff valve 5, a distribution valve 6, a first nozzle 7, a second nozzle 8, a metering valve 9, a differential-pressure valve 10, and a return-oil pressure-reducing valve 11. Its working principle is as follows: After the fuel supply oil is pressurized by the low-pressure pump 1, the system low-pressure oil is formed, and the pressure of the low-pressure oil is Pb. The low-pressure oil is further pressurized by the high-pressure pump 2 to form high-pressure oil, and the pressure of the high-pressure oil is Ps. One way of the high-pressure oil is supplied to the constant-pressure valve 3 of the servo system for modulating the constant-pressure oil, and the pressure of the constant-pressure oil is Pc. One way of the constant-pressure oil is used to control the actuating mechanism 4; the other way is supplied to the metering valve 9. The pressure before the metering valve 9 is P1, and the pressure after the metering valve 9 is P2. The differential-pressure valve 10 senses the pressures before and after the metering valve 9 and controls the return-oil flow rate by controlling the position of the return-oil pressure-reducing valve 11, so as to maintain the constant differential pressure before and after the metering valve 9, making the metering flow rate only related to the opening of the metering valve 9. The fuel enters the high-pressure shutoff valve 5 through the metering valve 9. When the metering flow rate is small, the high-pressure shutoff valve 5 closes to ensure that the fuel system has enough high-pressure oil. When the metering flow rate increases, the high-pressure shutoff valve 5 opens, and the pressure after the high-pressure shutoff valve 5 is P22. The metered oil enters the fuel distribution valve 6 after passing through the high-pressure shutoff valve 5, and the fuel after distribution is supplied to the fuel nozzle.

[0035] In a typical aeroengine fuel system, the pressure conditions of each part of the metering fuel flow path 12 are: Ps > P1 > P2 > P22; the pressure conditions of each part of the servo fuel flow path 13 are: Ps>Pc>Pb, and Pc - Pb = constant.

[0036] Refer to Figure 2 、 Figure 3 As shown, in one embodiment, a parking return-oil mechanism is used for the fuel system of a gas turbine. The fuel system includes a first pressure source 14, a second pressure source 15, and a third pressure source 16. The parking return-oil mechanism includes a switching member 602 and a parking return-oil valve 604. The parking return-oil valve includes a second pressure flow path 608 and a third pressure flow path 607; wherein, the switching member 602 is fixedly connected to the parking return-oil valve 604 and acts on the parking return-oil valve 604 to generate a switching force Nt. The second pressure flow path 608 is connected to the second pressure source 15, and the third pressure flow path 607 is connected to the third pressure source 16. The parking return-oil mechanism has a first state and a second state:

[0037] (1) In the first state, the force Npcb exerted by the first pressure source 14 on the parking return-oil valve is greater than the switching force Nt, and the second pressure flow path 608 is communicated.

[0038] (2) In the second state, the force Npcb exerted by the first pressure source 14 on the parking return-oil valve is less than the switching force Nt, and the third pressure flow path 607 is communicated.

[0039] The fuel flow path is switched by the pressure difference generated by the first pressure source 14 of the fuel system and the switching member 602. Depending on the structures of the fuel system and the parking fuel return mechanism itself, no other pressure source is required, and it is light in weight, capable of reducing the overall weight of the fuel system and increasing the thrust-to-weight ratio of the engine.

[0040] Continue to refer to Figure 2 、 Figure 3 As shown, in one embodiment, a specific example of the switching member 602 may be an elastic member, and the generated switching force Nt is an elastic force. The switching member 602 is composed of an elastic member and is a pure mechanical structure. Even after the engine stops rotating, it can still operate to ensure fuel return, prevent leakage, and has a simple structure, making it easy to realize the rapid switching between the starting and stopping states of the engine through the pressure difference between the first pressure source and the elastic member without affecting the normal operation of the engine. In another alternative embodiment, the switching member 602 is a spring.

[0041] Continue to refer to Figure 2 、 Figure 3 As shown, in one embodiment, the specific structure of the second pressure flow path 608 may be that both ends of the second pressure flow path 608 are respectively provided with a second pressure input port 6081 and a second pressure output port 6082, and the second pressure input port 6081 is connected to the second pressure source 15; the specific structure of the third pressure flow path 607 may be that both ends of the third pressure flow path 607 are respectively provided with a third pressure input port 6071 and a third pressure output port 6072, and the third pressure input port 6071 is connected to the third pressure source 16. The setting of the pressure input port and the pressure output port facilitates connection to each pipeline to realize the supply of fuel and the discharge of fuel during parking fuel return.

[0042] Refer to Figure 3 As shown, in one embodiment, the specific structure of the third pressure input port 6071 may be provided with a check valve. When the third pressure generated by the third pressure source 16 is greater than the set value Py of the check valve, the check valve opens. When the parking fuel return mechanism is in the first state, although the third pressure flow path 607 is not connected, there is still a risk of fuel leakage. Installing a check valve can effectively prevent fuel from leaking into the fuel system through the third pressure flow path 607 and causing danger.

[0043] Refer to Figure 2 、 Figure 3As shown, in one embodiment, a fuel system includes a parking fuel return mechanism as described above, as well as a low-pressure pump 609, a high-pressure shutoff valve 603, and a distribution valve 601. The low-pressure pump 609 is connected to the third pressure output port 6072 of the third pressure flow path, and the high-pressure shutoff valve 603 is connected to the second pressure input port 6081 of the second pressure flow path. The fuel system has a first state and a second state:

[0044] (1) In the first state, the force Npcb exerted by the first pressure source 14 on the parking fuel return valve is greater than the switching force Nt. The second pressure output port 6082 of the second pressure flow path is connected to the distribution valve 601, and the second pressure flow path 608 is in communication;

[0045] (2) In the second state, the force Npcb exerted by the first pressure source 14 on the parking fuel return valve is less than the switching force. The third pressure input port 6071 of the third pressure flow path is connected to the distribution valve 601, and the third pressure flow path 607 is in communication.

[0046] In another embodiment, the specific configurations of the first pressure source 14, the second pressure source 15, and the third pressure source 16 may be that the first pressure source 14 is the system pressure, which is generated by the fuel output by the fuel pump flowing through the hydraulic mechanical device. The second pressure source 15 is generated by the fuel flowing through the high-pressure shutoff valve 603, and the third pressure source 16 is generated by the fuel in the fuel manifold and the manifold 606.

[0047] In another embodiment, the specific structure of the fuel system may further include a nozzle 605. The nozzle 605 is connected to the distribution valve 601 and is used to atomize the fuel supplied to the combustion chamber to make the combustion more complete.

[0048] In an alternative embodiment, the specific structure of the nozzle 605 may further include a nozzle check valve, which can not only prevent fuel backflow but also prevent the fuel in the fuel manifold and the manifold 606 from flowing back to the combustion chamber again after thermal expansion.

[0049] Figure 2The specific implementation shown is an example of the fuel flow direction in the first state. The first state is the normal operating state. At this time, the system pressure Pcb generates an upward force Npcb on the bottom surface of the parking return valve 604, which overcomes the spring force Nt. The parking return valve 604 compresses the spring 602 and moves upward, causing the metered incoming fuel Pfm to open the high-pressure shutoff valve 603 and flow to the second pressure input port 6081 of the parking return valve 604 and flow out from the second pressure output port 6082 to the distribution valve 601. Subsequently, it pushes open the nozzle 605 with a check valve function and enters the combustion chamber for combustion. The opening pressure of the nozzle check valve is Pn. The fuel with a pressure of Pb at the low-pressure pump 609 is blocked at the third pressure input port 6071 of the parking return valve 604 with a check valve function. The pressure condition in the first state is Pcb > Pb, Pfm > Pn, Npcb > Nt.

[0050] Figure 3 The specific implementation shown is an example of the fuel flow direction in the initial state of the second state. The initial second state is the state where the engine has just stopped and the fuel pump is still being supplied with fuel. At this time, the system pressure Pcb generates an upward force Npcb on the bottom surface of the parking return valve 604, which cannot overcome the spring force Nt. The parking return valve 604 is pressed downward by the spring 602, causing the fuel in the fuel manifold and manifold 606 to flow into the third pressure flow path 607 through the third pressure input port 6071 of the parking return valve 604 with a check valve function and flow out from the third pressure output port 6072 to the flow path connected to the low-pressure pump. The opening pressure of the check valve is Py, and the pressure at the low-pressure pump is Pb. When the fuel in the fuel manifold and manifold 606 rises in temperature and pressure due to heat radiation, the pressure of the fuel in the fuel manifold and manifold 606 at this time is Pm, which overcomes the opening pressure Py of the check valve and the pressure Pb at the low-pressure pump and flows to the low-pressure pump. At the same time, the fuel pressure Pm in the fuel manifold and manifold 606 is lower than the opening pressure Pn of the nozzle check valve and cannot open the nozzle 605 with a check valve function and flow to the combustion chamber. The pressure condition in the initial second state is Pn > Pm > Pb ≈ Pcb ≈ the fuel supply pressure of the fuel pump > Py, Nt >

[0051] Npcb.

[0052] Figure 4 The specific implementation shown is an example of the fuel flow direction in the final state of the second state. The final second state is the state where the engine has stopped and the fuel pump is not being supplied with fuel. This example follows the Figure 3 element numbers and some content of the example shown above. The same numbers are used to represent the same or similar elements, and the description of the same technical content is selectively omitted. For the description of the omitted part, reference can be made to the Figure 3 example shown above, and this example will not be repeated here. Figure 4 The example shown andFigure 3 In comparison, the difference lies in that the pressure and force-bearing conditions in the final second state are Pn > Pm > Py > Pb ≈ Pcb ≈ 0, and Nt > Npcb.

[0053] Reference Figure 2 、 Figure 3 As shown, in one embodiment, a gas turbine includes a combustion chamber and the fuel system as described above for supplying fuel to the combustion chamber. In another embodiment, the gas turbine has a first state and a second state:

[0054] (1) In the first state, the gas turbine operates, and the second pressure flow path 608 is connected to supply fuel to the combustion chamber;

[0055] (2) In the second state, the gas turbine stops, and the third pressure flow path 607 is connected to prevent the fuel system from returning oil.

[0056] In summary, the beneficial effects of the parking oil return mechanism, fuel system, and gas turbine introduced in the above embodiments include but are not limited to one or a combination of the following:

[0057] 1. The fuel flow path is switched by the pressure difference generated by the first pressure source and the switching member of the fuel system. Relying on the structure of the fuel system and the parking oil return mechanism itself, without the need for other pressure sources, it is lightweight and can reduce the overall weight of the fuel system, improving the thrust-to-weight ratio of the engine.

[0058] 2. The switching member is composed of an elastic member and is a pure mechanical structure. Even after the engine stops rotating, it can still operate to ensure fuel return, prevent leakage, and has a simple structure, making it easy to quickly switch between the starting and stopping states of the engine through the pressure difference between the first pressure source and the elastic member without affecting the normal operation of the engine.

[0059] 3. The pressure input port and pressure output port are provided to facilitate connection to each pipeline to achieve fuel supply and the discharge of parking oil return.

[0060] 4. Installing a one-way valve at the third pressure input port can effectively prevent fuel from leaking into the fuel system through the third pressure flow path and causing danger.

[0061] 5. Setting the nozzle one-way valve can not only prevent fuel from flowing backward but also prevent the fuel in the fuel main pipe and manifold from flowing back to the combustion chamber again after being heated and expanded.

[0062] Although the present invention is disclosed above in preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, all modifications, equivalent changes and decorations made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention fall within the protection scope defined by the claims of the present invention.

Claims

1. A parking fuel return mechanism for the fuel system of a gas turbine, the fuel system comprising a first pressure source, a second pressure source, and a third pressure source, characterized in that, The parking fuel return mechanism includes: A switching member; A parking fuel return valve, including a second pressure flow path and a third pressure flow path; Wherein, the switching member is fixedly connected to the parking fuel return valve and acts on the parking fuel return valve to generate a switching force, the second pressure flow path is connected to the second pressure source, and the third pressure flow path is connected to the third pressure source; The fuel return mechanism has a first state and a second state: In the first state, the force exerted by the first pressure source on the parking fuel return valve is greater than the switching force, and the second pressure flow path is connected; In the second state, the force exerted by the first pressure source on the parking fuel return valve is less than the switching force, and the third pressure flow path is connected.

2. The parking fuel return mechanism according to claim 1, characterized in that, The switching member is an elastic member, and the generated switching force is an elastic force.

3. The parking fuel return mechanism according to claim 1, characterized in that, Both ends of the second pressure flow path respectively have a second pressure input port and a second pressure output port, and the second pressure input port is connected to the second pressure source; both ends of the third pressure flow path respectively have a third pressure input port and a third pressure output port, and the third pressure input port is connected to the third pressure source.

4. The parking fuel return mechanism according to claim 3, characterized in that, A check valve is provided at the third pressure input port, and when the third pressure generated by the third pressure source is greater than the set value of the check valve, the check valve opens.

5. A fuel system, characterized in that, The fuel system includes the parking fuel return mechanism according to any one of claims 1-4, as well as a low-pressure pump, a high-pressure shut-off valve, and a distribution valve. The low-pressure pump is connected to the third pressure output port of the third pressure flow path, and the high-pressure shut-off valve is connected to the second pressure input port of the second pressure flow path; the fuel system has a first state and a second state: In the first state, the force exerted by the first pressure source on the parking fuel return valve is greater than the switching force, the second pressure output port of the second pressure flow path is connected to the distribution valve, and the second pressure flow path is connected; In the second state, the force exerted by the first pressure source on the parking fuel return valve is less than the switching force, the third pressure input port of the third pressure flow path is connected to the distribution valve, and the third pressure flow path is connected.

6. The fuel system according to claim 5, characterized in that, The first pressure source is the system pressure, the high-pressure shut-off valve generates the second pressure source, and the fuel in the fuel manifold and the manifold generates the third pressure source.

7. The fuel system according to claim 5, characterized in that, The fuel system includes a nozzle, and the nozzle is connected to the distribution valve.

8. The fuel system according to claim 7, characterized in that, The nozzle has a check valve.

9. The fuel system according to claim 5, characterized in that, The first state is normal operation, and the pressure and force conditions are that the pressure Pn at the nozzle of the fuel system is less than the second pressure Pfm generated by the second pressure source, the pressure Pb at the low-pressure pump is less than the system pressure Pcb generated by the first pressure source, and the force Npcb exerted by the first pressure source on the parking fuel return valve is greater than the switching force Nt generated by the switching member; The second state includes an initial second state, which is just after parking. The pressure and force conditions are that the pressure Pn at the nozzle of the fuel system is greater than the third pressure Pm generated by the third pressure source, which is greater than the pressure Pb at the low-pressure pump. The pressure Pb at the low-pressure pump is approximately equal to the system pressure Pcb generated by the first pressure source, which is approximately equal to the supply pressure of the fuel pump of the fuel system, which is greater than the opening pressure Py of the check valve at the third pressure input port. The force Npcb exerted by the first pressure source on the parking oil return valve is less than the switching force Nt generated by the switching member; The second state further includes a final second state, which is a complete stop. The pressure and force conditions are that the pressure Pn at the nozzle of the fuel system is greater than the third pressure Pm generated by the third pressure source, which is greater than the opening pressure Py of the check valve at the third pressure input port, which is greater than the pressure Pb at the low-pressure pump. The pressure Pb at the low-pressure pump is approximately equal to the system pressure Pcb generated by the first pressure source, which is approximately equal to zero. The force Npcb exerted by the first pressure source on the parking oil return valve is less than the switching force Nt generated by the switching member.

10. A gas turbine, comprising a combustion chamber, characterized in that, It further includes a fuel system according to any one of claims 5-9, for supplying fuel to the combustion chamber.

11. The gas turbine according to claim 10, characterized in that, The gas turbine has a first state and a second state: In the first state, the gas turbine operates, and the second pressure flow path is connected to supply fuel to the combustion chamber; In the second state, the gas turbine stops, and the third pressure flow path is connected to prevent the fuel system from returning oil.

Images