Gas turbine and its liquid fuel supply system

Abstract

In the fuel supply system 9 of the gas turbine 1 using liquid fuel, the size of the pumps 11a and 11b is made as small as possible relative to the size of the gas turbine. [Solution] The liquid fuel supply system 9 of the gas turbine includes a first pump 11a that pumps the liquid fuel during the pressure spraying process of the liquid fuel until ignition of the combustion field BF, and a second pump 11b that pumps the liquid fuel during the air blasting process of the liquid fuel after ignition of the combustion field. The first and second pumps may each be diaphragm pumps.

Description

Technical Field

[0001] The present invention relates to a liquid fuel supply system for a gas turbine engine (hereinafter referred to as a "gas turbine").

Background Art

[0002] In gas turbine engines, various configurations have been proposed for reducing NOx in exhaust gases. For example, in Patent Document 1, in a combustion device, as a configuration for realizing low NOx combustion, preventing backfire, and suppressing combustion vibration, a combustion cylinder forming a combustion chamber and a fuel injector having a plurality of annular fuel injection units arranged concentrically are provided. Each fuel injection unit has an annular fuel injection member having a plurality of fuel injection holes opening on an outer peripheral surface and / or an inner peripheral surface, and an annular air guide member for guiding air to the fuel gas injected from each fuel injection hole of the annular fuel injection member. A plurality of circumferential isolation walls that isolate the gas passage of the annular fuel injection unit at equal intervals in the circumferential direction and extend in the radial direction, and at least one of the isolation walls, a radial isolation wall that isolates the space between two adjacent annular fuel injection units in the radial direction and extends in the circumferential direction, are provided. Also, in Patent Document 2, in a small gas turbine using gaseous fuel having a configuration in which air is sucked and compressed by a centrifugal compressor, high-temperature combustion gas is generated in a combustor, a turbine is driven by the combustion gas, and power is generated by a generator coupled by a rotating shaft, a groove is provided on the shroud surface of the inducer portion from the inlet of the centrifugal compressor to feed gaseous fuel. Due to the pressure loss in the flow path before the centrifugal compressor and the speed increase due to the narrowing of the inlet pipe, the gaseous fuel is sucked by the negative pressure generated, and thus a configuration in which a fuel pump is unnecessary has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

[0004] In a fuel supply system for supplying liquid fuel to a combustor in a gas turbine, it is preferable to atomize the liquid fuel as much as possible before introducing it into the combustion field in order to reduce NOx emissions. In this regard, before ignition of the combustion field at the start of the gas turbine, the turbine rotation speed is usually low, and therefore the airflow is small and the temperature of the combustion field is not high, so the fuel is sprayed through relatively small holes under pressure to disperse in a mist-like form in the air (pressure spraying process). Then, after ignition of the combustion field, as the turbine rotation speed increases, the airflow into the combustion field increases and the temperature of the combustion field also increases, so the fuel delivery method is switched so that the liquid fuel is introduced into the combustion field together with the airflow, and the liquid fuel is atomized and evaporated and dispersed in the combustion field by exposure to the force of the airflow and the high temperature environment of the combustion field (air blasting process).

[0005] In large gas turbine generators and aircraft engines with outputs exceeding 100 kW, fuel supply, including the pressure spraying and air blasting processes described above, is typically performed by a single pump. In this case, during the pressure spraying process until ignition of the combustion field at the start of the gas turbine, the pump is used to pump fuel at a first pump output that achieves the spraying of liquid fuel. In the air blasting process after ignition of the combustion field, the pump output is increased to a second pump output higher than the first pump output, and the fuel supply path is switched to a flow path where it merges with the airflow, and fuel is pumped under pressure. Therefore, gear pumps or vane pumps with relatively high pump output are used to achieve the pump output required for both the pressure spraying and air blasting processes.

[0006] Incidentally, when gas turbines are installed as drive systems for mobile vehicles such as automobiles or small flying objects such as drones, small gas turbines with an output of less than 100 kW are used. Even with such small gas turbines, when liquid fuel is used, it is desirable that the pressure spray process is performed until the combustion field is ignited, and the air blast process is performed after the combustion field is ignited, as described above. In this regard, if the fuel supply for the pressure spray process and the air blast process is to be performed by a single pump, as in a large gas turbine, a pump with a relatively large pump output will be required, and the size (dimensions and weight) of the fuel supply pump will be relatively large in proportion to the overall gas turbine. However, when considering mounting a gas turbine on a mobile object, it is preferable that the size of the pump can also be reduced.

[0007] Thus, the main objective of the present invention is to minimize the size of the pump relative to the size of the gas turbine in a fuel supply system for a gas turbine using liquid fuel.

[0008] Regarding the above problem, in a configuration where a single pump performs both the pressure spraying process and the air blasting process, a second pump output higher than the first pump output was required to switch the fuel flow path for the transition from the pressure spraying process to the air blasting process. However, in the air blasting process itself, it is sufficient for liquid fuel to be injected into the airflow, and the delivery of the fuel itself does not require an output as high as the second pump output. In addition, generally, the maximum possible output of a pump varies depending on the pumping method, and by reducing the required output, it may be possible to use a pump with a more compact size, such as a diaphragm pump. Therefore, in a gas turbine, if separate pumps are used for the pressure spraying process and the air blasting process, the required output of each pump can be reduced, making it possible to select a pump with a smaller maximum possible output and a more compact size and weight, thereby minimizing the size of the pump relative to the size of the gas turbine. This knowledge is utilized in the present invention. [Means for solving the problem]

[0009] According to one aspect of the present invention, the above problem is addressed in a liquid fuel supply system for a gas turbine, A first pump that pumps the liquid fuel during the pressure atomization process of the liquid fuel before ignition of the combustion field, In the air blast process of the liquid fuel after ignition in the aforementioned combustion field, a second pump pressurizes the liquid fuel. This is achieved by a system that has [this feature].

[0010] In the above configuration, the "gas turbine" may be any type of gas turbine, except for the configuration specified above. In short, in a gas turbine, fuel is supplied from the combustion nozzle to the combustor, where compressed air and fuel are combusted, and the resulting combustion gases rotate the turbine to generate rotational force, while a compressor coaxial with the turbine compresses the air and sends it to the combustor. The "liquid fuel supply system" is a system that delivers liquid fuel from the fuel tank to the combustion nozzle. The "pressure spray process" is, as described above, the process of spraying liquid fuel into the air by applying pressure and pushing it out through relatively small holes until the combustion field ignites during the startup of the gas turbine. The "air blast process" is, as described above, the process of introducing liquid fuel into the combustion field together with the airflow after the combustion field has ignited. Therefore, in the gas turbine to which the present invention is applied, fuel is supplied by a pressure spray process until ignition of the combustion field, and then supplied by an air blast process after ignition of the combustion field. As a result, the liquid fuel is properly atomized, evaporated, and dispersed in the combustion field, and NOx emissions are reduced in the exhaust gas.

[0011] In the configuration of the present invention described above, separate pumps, namely a first pump and a second pump, are used to pump the liquid fuel to the combustion nozzle in the pressure spraying process and the air blasting process, respectively. Here, the first pump and the second pump only need to achieve the pressure spraying process and the air blasting process, respectively, so as already mentioned, the required pump output can be relatively low, and therefore, small pumps can be used for each, making it possible to reduce the ratio of the pump size to the size of the gas turbine, even with a small gas turbine.

[0012] Furthermore, diaphragm pumps may be used for both the first and second pumps mentioned above. Compared to pumps of the gear pump or vane pump type, diaphragm pumps have a smaller maximum output, but they are more compact in size. The combined size of two diaphragm pumps is far smaller than the size of a single gear pump or vane pump, and therefore, it is possible to advantageously reduce the size of the pumps relative to the size of the gas turbine.

[0013] The gas turbine to which the present invention is applied may be a gas turbine with an output of less than 100 kW, and more preferably, one with an output in the range of 5 kW to 50 kW.

[0014] As described above, by using separate pumps for the pressure spraying process and the air blasting process, the required pump output for each pump can be reduced, which in turn allows for the use of smaller pumps and thus makes it possible to reduce the overall size of the gas turbine. Thus, according to another aspect of the present invention, a gas turbine using liquid fuel, A first pump that pumps the liquid fuel during the pressure atomization process of the liquid fuel before ignition of the combustion field, In the air blast process of the liquid fuel after ignition in the aforementioned combustion field, a second pump pressurizes the liquid fuel. A gas turbine equipped with a liquid fuel supply system is provided. [Effects of the Invention]

[0015] Thus, in the present invention, in order to reduce NOx in the exhaust gas of a gas turbine, a gas turbine or its liquid fuel supply system is configured to perform a pressure spray process until ignition in the combustion field and an air blast process after ignition in the combustion field. By separating the pumps for supplying liquid fuel to the combustion field in each of the pressure spray process and the air blast process, the pump output required for each pump is reduced. As a result, it becomes possible to use pumps with smaller dimensions and weights, and thus it is possible to make the size of the pump relative to the size of the gas turbine as small as possible. The configuration of the present invention is advantageously used for small gas turbines mounted on mobile bodies.

[0016] Other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments of the present invention.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 is a diagram showing the overall configuration of a gas turbine to which the present embodiment is applied. [Figure 2] FIG. 2 is a diagram showing the configuration of the liquid fuel supply system of the gas turbine according to the present embodiment. [Figure 3] FIG. 3 is a diagram showing the configuration of the liquid fuel supply system of a conventional gas turbine.

Explanation of Reference Numerals

[0018] 1... Gas turbine, 2... Turbine shaft, 3... Turbine, 4... Compressor, 5... Load equipment (generator), 6... Combustor, 7... Compressed air flow path, 8... Combustion chamber, 9... Fuel supply system, 10... Combustion gas flow path, 11a... Pressure spray pump, 11b... Air blast pump, 11o... Combined pump, 12... Metering valve, 14... Combustion nozzle, 14a, b, c... Fuel flow paths, 14d... Flow path opening / closing valve, 15c... Fuel injection hole (for pressure spray), 15s... Fuel injection hole (for air blast), f... Fuel flow, a... Compressed air flow, BF... Combustion field

Best Mode for Carrying Out the Invention

[0019] Basic configuration of a gas turbine The gas turbine to which the present embodiment is applied may be a gas turbine in any form, except for the configuration of the pump in the fuel supply system. Briefly stated, as shown in FIG. 1, the gas turbine 1 may have a turbine 3 connected to a turbine shaft 2, a compressor 4, a load device 5 such as a generator, and a combustor 6. In the basic operation, the air (compressed air) a compressed by the rotation of the turbine shaft 2 in the compressor 4 is sent through a flow path 7 to a combustion chamber 8 of the combustor 6, where it is mixed with fuel f from a fuel supply system 9 and burned. The combustion gas is sent through a combustion gas flow path 10 to the turbine 3, rotating the turbine shaft 2, thereby performing the compression of air in the compressor 4 and the operation of the load device 5, for example, power generation by the rotation of the rotor of the generator. The fuel supplied to the combustor 6 may be hydrogen, but is not limited thereto.

[0020] Configuration of a liquid fuel supply system In the gas turbine as described above, when liquid fuel is used, as already described, in order to reduce NOx in the exhaust gas, the rotational speed of the turbine until ignition of the combustion field is low so that the liquid fuel is atomized as much as possible and introduced into the combustion field. Therefore, in a state where the air flow is small and the temperature of the combustion field is not high, a pressure spraying process is performed in which the fuel is sprayed under pressure from relatively small holes so as to be dispersed in a mist form in the space. Then, after ignition of the combustion field, when the rotational speed of the turbine increases and the air flow into the combustion field increases and the temperature of the combustion field also increases, an air blast process is performed in which the liquid fuel is introduced into the combustion field together with the air flow.

[0021] In the case where different processes are performed before and after ignition of the combustion field, the supply of liquid fuel to the combustion nozzle was previously carried out using a single pump 11o, as schematically depicted in Figure 3. In that case, until the combustion field is ignited during the startup of the gas turbine, the output of the pump is adjusted to the first output to perform the pressure spray process. At this point, the liquid fuel f passes through the metering valve 12 and the fuel passages 14a and 14b of the combustion nozzle, and is sprayed in a mist under pressure from the fuel injection hole 15c, as shown I in the figure. After that, when the combustion field is ignited, the output of the pump is increased to perform the air blast process. This causes the flow path opening valve 14d, which is located in the branch passage from the fuel passage 14a, to open, and the fuel flows into the fuel passage 14c. Here, as the turbine rotation speed increases and the compressed air flow a from the compressor also increases, the liquid fuel is injected from the fuel passage 14c through the fuel injection port 15s while being mixed with the compressed air flow a. Exposed to the force of the airflow and the high-temperature environment of the combustion field, it is agitated in space as shown in II in the figure, atomized and evaporated, and dispersed within the combustion field.

[0022] Therefore, when a single pump 11o is used to supply fuel for both the pressure atomization process and the air blast process, the pump 11o needs to be capable of supplying both a pump output to pump fuel to achieve the pressure atomization process and a higher pump output to switch the flow path for the air blast process. Typically, a gear pump or a vane pump would be used as a pump capable of supplying such pump output, but these types of pumps are generally large in size and weight, and the ratio of the pump size to the overall size of the gas turbine can be large. In particular, in small gas turbines with an output of 100kW or less, preferably 50kW to 5kW, which are intended to be mounted on a mobile body, the ratio of the pump to the total weight of the gas turbine can reach 20%, which is inefficient.

[0023] Incidentally, in the air blast process described above, the liquid fuel is atomized, evaporated, and dispersed within the combustion field due to exposure to the force of the compressed air flow and the high-temperature environment, so high pump output is not required for the fuel delivery itself. In other words, when only the air blast process is performed, high pump output is not required to perform both the pressure spray process and the air blast process with a single pump. Therefore, if the fuel delivery in the pressure spray process and the air blast process is performed with separate pumps, the number of pumps will increase, but the maximum possible output required for each pump can be reduced. Furthermore, when the maximum possible output is reduced, the variety of available pump types increases, allowing the use of pumps with a smaller size or weight ratio to the maximum possible output than gear pumps or vane pumps, such as diaphragm pumps. In fact, the dimensions and weight of two diaphragm pumps are significantly smaller than the dimensions and weight of one gear pump or vane pump.

[0024] Therefore, in this embodiment, as shown in Figure 2, a pressure spray pump 11a and an air blast pump 11b are used, and the pump used is switched according to the operating state of the gas turbine to supply liquid fuel. Specifically, until the combustion field is ignited at the start of the gas turbine, the fuel f is sprayed in a mist into the combustion field BF from the fuel injection hole 15c under pressure by the pump 11a through the fuel passage 14b in the combustion nozzle 14 via the metering valve 12, as shown in Figure I, achieving the pressure spray process. Then, when the combustion field is ignited, the pump 11b is activated, and from there, the fuel f is sent out from the fuel injection hole 15s, carried by the compressed air flow a, through the fuel passage 14c in the combustion nozzle 14 via the metering valve 12, as shown in Figure II, spreading into the combustion field BF, achieving the air blast process. In the above configuration, fuel passage 14b and fuel passage 14c are connected to pumps 11a and 11b, respectively, but are not connected to each other. Furthermore, the pumping of fuel from pump 11a may continue even after ignition of the combustion field.

[0025] As already mentioned, diaphragm pumps are advantageously used for pumps 11a and 11b. In that case, even two pumps combined are smaller than one gear pump or vane pump, and the size ratio of the two pumps combined will be about 5% of the total size of the gas turbine, even in the case of a small gas turbine mounted on a mobile unit.

[0026] Thus, in this embodiment, it is possible to reduce NOx emissions from the gas turbine exhaust while also reducing the ratio of the pump size to the overall size of the gas turbine. The configuration of this embodiment may be advantageously used for small gas turbines mounted on mobile structures.

[0027] While the above description is made in relation to embodiments of the present invention, many modifications and changes are readily possible for those skilled in the art, and it will be clear that the present invention is not limited to the embodiments illustrated above, but can be applied to various devices without departing from the concept of the present invention.

Claims

1. A liquid fuel supply system for a gas turbine, A first pump that pumps the liquid fuel during the pressure atomization process of the liquid fuel before ignition of the combustion field, In the air blast process of the liquid fuel after ignition in the aforementioned combustion field, a second pump pressurizes the liquid fuel. A system that has

2. The system according to claim 1, wherein the first and second pumps are each diaphragm pumps.

3. A system according to claim 1, wherein the gas turbine is a gas turbine with an output of less than 100 kW.

4. A gas turbine that uses liquid fuel, A first pump that pumps the liquid fuel during the pressure atomization process of the liquid fuel before ignition of the combustion field, In the air blast process of the liquid fuel after ignition in the aforementioned combustion field, a second pump pressurizes the liquid fuel. A gas turbine equipped with a liquid fuel supply system.

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