combustor

Abstract

A heat storage body through which a gas and a liquid pass, a first fuel injector that is provided upstream of the heat storage body in a direction in which the gas and the liquid flow and injects a first fuel, an igniter that is provided downstream of the heat storage body in the direction in which the gas and the liquid flow, and a second fuel injector that is provided downstream of the first fuel injector and upstream of the igniter in the direction in which the gas and the liquid flow and injects a second fuel having lower ignitability than the first fuel.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to Japanese Patent Application No. 2025-026907 filed on Feb. 21, 2025. The disclosure of the above-identified application, including the specification, drawings, and claims, is incorporated by reference herein in its entirety.BACKGROUND1. Technical Field

[0002] The present disclosure relates to a combustor.2. Description of Related Art

[0003] In a gas turbine combustor and a gas turbine described in Japanese Unexamined Patent Application Publication No. 2024-013988 (JP 2024-013988 A), generation of CO is reduced by improving combustibility of a combustion gas in a first stage. Further, generation of NOx is reduced by improving mixability of the combustion gas in the first stage and a pre-mixed gas in a second stage.SUMMARY

[0004] An object of the present disclosure is to promote warming up of a combustor.

[0005] According to an aspect of the present disclosure,

[0006] a combustor includes:

[0007] a heat storage body through which a gas and a liquid pass;

[0008] a first fuel injector provided upstream of the heat storage body in a direction in which the gas and the liquid flow, the first fuel injector being configured to inject first fuel;

[0009] an igniter provided downstream of the heat storage body in the direction in which the gas and the liquid flow; and

[0010] a second fuel injector provided downstream of the first fuel injector and upstream of the igniter in the direction in which the gas and the liquid flow, the second fuel injector being configured to inject second fuel having ignitability lower than ignitability of the first fuel.

[0011] According to the present disclosure, it is possible to promote warming up of a combustor.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:

[0013] FIG. 1 is a diagram schematically showing a power generation system having a combustor in a first embodiment;

[0014] FIG. 2 is a schematic configuration diagram of a combustor according to the first embodiment;

[0015] FIG. 3A is a diagram showing a state of a flame at the time of start according to the first embodiment;

[0016] FIG. 3B is a diagram showing a state of a flame at the time of warm-up according to the first embodiment;

[0017] FIG. 3C is a diagram showing a state of a flame at a time of steady operation according to the first embodiment;

[0018] FIG. 4 is a flowchart showing a control flow of the combustor in the ECU;

[0019] FIG. 5A is a diagram showing a state of a flame at the time of start according to the second embodiment;

[0020] FIG. 5B is a diagram showing a state of a flame at the time of warm-up according to the second embodiment; and

[0021] FIG. 5C is a diagram showing a state of a flame at a time of steady operation according to the second embodiment.DETAILED DESCRIPTION OF EMBODIMENTS

[0022] In a process from start of the combustor to warm-up, lean combustion is difficult, and there is a possibility that NOx is emitted. That is, in a case where the warm-up of the combustor is not promptly performed, there is a possibility that NOx is emitted from the combustor.

[0023] Therefore, a combustor that is one of the aspects of the present disclosure includes a heat storage body, a first fuel injector, an igniter, and a second fuel injector. The heat storage body has a structure through which a gas and a liquid pass. The first fuel injector is provided upstream of the heat storage body in a direction in which the gas and the liquid flow, and injects the first fuel. The igniter is provided downstream of the heat storage body in the direction in which the gas and the liquid flow. The second fuel injector is provided downstream of the first fuel injector and upstream of the igniter in the direction in which the gas and the liquid flow, and injects the second fuel having lower ignitability than the first fuel.

[0024] The first fuel is, for example, a fuel having a sufficiently high concentration of a fuel component and thus having high ignitability, and the second fuel is, for example, a fuel having a lower concentration of the fuel component than the first fuel and thus having low ignitability. The first fuel and the second fuel may be fuels that can be used as fuels of the SOFC, such as hydrogen, city gas (CH4), and biomass gas. The first fuel may be a fuel containing the same concentration of the fuel component as the fuel supplied to the SOFC. Further, the second fuel may be the discharge fuel discharged from the SOFC.

[0025] The heat storage body can store heat generated by burning the first fuel and the second fuel. In addition, the combustion of the first fuel and the second fuel can be stabilized by the radiative heat from the heat storage body. The heat storage body may be, for example, a ceramic foam having pores or a ceramic having a honeycomb structure. Examples of the material of the ceramic include cordierite, silicon carbide, and aluminum titanate. By providing the heat storage body, it is possible to stabilize the combustion even at the time of the lean combustion and to reduce the amount of NOx emitted. In addition, since the combustion is stabilized by receiving the heat from the heat storage body, further lean operation is possible. For example, in a case where the concentration of the fuel component discharged from the SOFC is low, the combustion may be difficult. Even in such a case, the combustion at a lean air-fuel ratio is possible by receiving the radiative heat from the heat storage body.

[0026] For example, when the temperature of the heat storage body is low, the temperature of the heat storage body can be increased while the combustion is possible by increasing the proportion of the first fuel. In addition, for example, when the temperature of the heat storage body is high, the proportion of the second fuel is increased to make the combustion at a higher lean air-fuel ratio possible.

[0027] Hereinafter, an embodiment for implementing the present disclosure will be described in detail with reference to the drawings. Note that, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the scope of the present disclosure.First Embodiment

[0028] FIG. 1 is a diagram schematically showing a solid oxide fuel cell (SOFC) micro gas turbine hybrid power generation system 100 (hereinafter, referred to as power generation system 100) having a combustor 1 in a first embodiment. The power generation system 100 has an SOFC 2, a micro gas turbine (MGT) 3, and a regenerative heat exchanger 4 in addition to the combustor 1. The power generation system 100 adopts a two-stage power generation mechanism in which hydrogen and carbon monoxide extracted by reforming, for example, natural gas (CH4) are used for power generation in each of the SOFC 2 and the MGT 3. In addition, the power generation system 100 adopts cogeneration (combined heat and power generation) in which the exhaust heat generated in power generation is used as energy in the regenerative heat exchanger 4. The SOFC 2 is an example of a fuel cell.

[0029] A fuel supply pipe 101 that supplies natural gas (CH4) as fuel and a first end of an air supply pipe 102 that supplies air are connected to the SOFC 2. In addition, a first end of a discharge fuel pipe 103 through which the fuel (hereinafter, also referred to as discharge fuel) that is discharged without being used flows and a first end of an exhaust pipe 104 through which the exhaust gas (hereinafter, also referred to as exhaust air) that is at a high temperature and a high pressure flows are connected to the SOFC 2. The exhaust air is air in a state where oxygen is consumed and the amount of air is reduced in the SOFC 2. A second end of the discharge fuel pipe 103 and a second end of the exhaust pipe 104 are connected to the combustor 1. In addition, a follow-up fuel pipe 105 that supplies additional fuel (hereinafter, also referred to as follow-up fuel) is connected to the combustor 1.

[0030] In addition, a first end of a combustion gas exhaust pipe 106 for discharging the gas burned in the combustor 1 is connected to the combustor 1. A second end of the combustion gas exhaust pipe 106 is connected to an inlet of the turbine 32 of the MGT 3. In addition, a turbine exhaust pipe 107 is connected to an outlet of the turbine 32. The turbine exhaust pipe 107 is open to the outside through the regenerative heat exchanger 4.

[0031] Air is supplied to the inlet of the compressor 31 of the MGT 3. A second end of the air supply pipe 102 is connected to the outlet of the MGT 3. The regenerative heat exchanger 4 is interposed in the air supply pipe 102, and the heat of the exhaust gas from the turbine 32 that flows through the turbine exhaust pipe 107 is supplied to the air that flows through the air supply pipe 102. As a result, the air at a high temperature is supplied to the SOFC 2.

[0032] In the power generation system 100, power is generated in the following (1) to (5).

[0033] (1) Reform the natural gas (CH4) in the SOFC 2 to extract hydrogen (H2) and carbon monoxide (CO).

[0034] (2) Power is generated in the SOFC 2 by a chemical reaction between oxygen (O2) and hydrogen and carbon monoxide in the pressurized air sent from the compressor 31 of the MGT 3.

[0035] (3) The discharge fuel (hydrogen or the like) and the exhaust gas at a high temperature and a high pressure that are not used for power generation in the SOFC 2 are sent to the combustor 1.

[0036] (4) Burn the discharge fuel in the combustor 1, and rotate the turbine 32 of the MGT 3 to generate power.

[0037] (5) Recover the exhaust heat from the exhaust gas generated by the combustion.

[0038] The discharge fuel from the SOFC 2 is supplied to the combustor 1. From the start of the SOFC 2 to the completion of the warm-up, the realization of the lean combustion is difficult, and thus there is a possibility that a large amount of NOx is discharged by the diffusion combustion. On the other hand, after the warm-up is completed, the discharge fuel of the SOFC 2 in the combustor 1 is at a high temperature and thus immediately burns when mixed with air. However, in this case, the air-fuel ratio is excessively lean, and the combustion may be unstable. Therefore, in the present embodiment, the early warm-up is realized by using the heat storage and the radiative heat, and the lean combustion is stably performed.

[0039] FIG. 2 is a schematic configuration diagram of the combustor 1 according to the first embodiment. The combustor 1 is configured to include a casing 11, a ceramic foam (CF) 12, a discharge fuel injector 13, a follow-up fuel injector 14, and an ignition plug 15. The casing 11 is, for example, a cylindrical member, and the exhaust gas from the SOFC 2 flows through the inside. In FIG. 2, the exhaust gas of the SOFC 2 flows from the left to the right. The casing 11 is formed using a metal material, such as iron or SUS. The CF 12 is a porous member formed of cordierite, silicon carbide, or aluminum titanate, and the exhaust gas from the SOFC 2 passes through the inside. Instead of the CF 12, a member made of a ceramic having a honeycomb structure may be disposed.

[0040] The discharge fuel injector 13 is provided on the upstream side of the CF 12. The second end of the discharge fuel pipe 103 is connected to the discharge fuel injector 13. The discharge fuel injector 13 is an injector that injects the discharge fuel of the SOFC 2. The discharge fuel of the SOFC 2 includes hydrogen, carbon monoxide, or the like that is not used for power generation in the SOFC 2. The follow-up fuel injector 14 is provided on the upstream side of the discharge fuel injector 13. The follow-up fuel pipe 105 is connected to the follow-up fuel injector 14. The follow-up fuel injector 14 is an injector that injects fuel having higher ignitability than the discharge fuel injected from the discharge fuel injector 13. The follow-up fuel pipe 105 may be connected to the fuel supply pipe 101. That is, the follow-up fuel injected from the follow-up fuel injector 14 and the fuel supplied to the SOFC 2 may be the same. The ignition plug 15 is provided on the downstream side of the CF 12. The ignition plug 15 is a device that generates an electric spark to ignite the air-fuel mixture.

[0041] The follow-up fuel is an example of the first fuel, and the follow-up fuel injector 14 is an example of the first fuel injector. In addition, the discharge fuel is an example of the second fuel, and the discharge fuel injector 13 is an example of the second fuel injector. In addition, the CF 12 is an example of a heat storage body, and the ignition plug 15 is an example of an igniter.

[0042] The discharge fuel injector 13, the follow-up fuel injector 14, and the ignition plug 15 are connected to an electronic control unit 10 (hereinafter referred to as "ECU 10") via an electric wire. The ECU 10 includes a controller 110 and a storage unit 120. The controller 110 can be implemented by a hardware processor, such as a CPU. In addition, the controller 110 may be configured to include a RAM, a read-only memory (ROM), a cache memory, or the like. The storage unit 120 is a device that stores information, and is configured by a storage medium such as a RAM or a flash memory. The storage unit 120 stores a program executed by the controller 110, data used by the program, and the like.

[0043] The controller 110 controls the discharge fuel injector 13, the follow-up fuel injector 14, and the ignition plug 15. In addition, the temperature sensor 111 and the exhaust air amount control valve 112 are connected to the ECU 10. The temperature sensor 111 is a sensor that detects the temperature of the CF 12. The temperature sensor 111 may be a plurality of sensors that respectively detect the temperature of the upstream end surface and the downstream end surface of the CF 12, or may be a sensor that detects the temperature at any position in the combustor 1. The controller 110 may estimate the temperature of the CF 12 according to the temperature at any position in the combustor 1. At this time, the controller 110 may estimate the temperature of the upstream end surface and the downstream end surface of the CF 12. The estimation logic is stored in the storage unit 120. The exhaust air amount control valve 112 is a device that adjusts the amount of the exhaust air flowing through the combustor 1, and is controlled by the controller 110.

[0044] In addition, the controller 110 performs different controls at the time of start, at the time of warm-up, and at the time of steady operation of the SOFC 2, respectively. FIG. 3A is a diagram showing a state of a flame at the time of start according to the first embodiment. FIG. 3B is a diagram showing a state of a flame at the time of warm-up according to the first embodiment. FIG. 3C is a diagram showing a state of a flame at a time of steady operation according to the first embodiment. The controller 110 executes a start mode at the time of start, executes a warm-up mode at the time of warm-up, and executes a steady mode at the time of steady operation.

[0045] The start time refers to immediately after the start of the combustor 1. The temperature of the exhaust air at this time is, for example, a temperature between 25° C and 300° C. At the time of start, since the temperature of the exhaust air from the SOFC 2 is low, there is a possibility that the ignition is not performed with solely the discharge fuel having low ignitability. Therefore, the controller 110 supplies a greater amount of the follow-up fuel having high ignitability at the time of start. The ratio of the follow-up fuel to the discharge fuel at this time is, for example, a ratio between 6:4 and 9:1. That is, the follow-up fuel is injected more than the discharge fuel. The reference numeral 131 indicates a spray of the discharge fuel performed by the discharge fuel injector 13, and the reference numeral 141 indicates a spray of the follow-up fuel performed by the follow-up fuel injector 14. At this time, the amount of fuel injected from the discharge fuel injector 13 and the follow-up fuel injector 14 is determined by the pressure of the fuel and the valve opening time of the injector. When the pressure of the fuel supplied to both injectors is constant, the longer the valve opening time of the injector, the greater the fuel injection amount. Then, when the ignition plug 15 is ignited, the flame front 16 is formed near the ignition plug 15. As a result, the temperature of the CF 12 increases from the downstream side. In FIGS. 3A, 3B, and 3C, the reference symbol TA indicates a temperature. The temperature of the flame front 16 is, for example, 900° C. In the CF 12, the downstream side closer to the flame front 16 has a higher temperature TA. Since the distance from the fuel injected from the discharge fuel injector 13 and the follow-up fuel injector 14 to the ignition plug 15 is relatively long, the fuel and the air are well mixed, and the lean combustion is possible. After the flame front 16 is formed, even when the ignition plug 15 is stopped, the flame front 16 is maintained as long as the fuel is injected.

[0046] The warm-up time refers to a time when the temperature of the combustor 1 is increased to a steady temperature. The temperature of the exhaust air at this time is, for example, a temperature between 300° C and 500° C. At the time of warm-up, the temperature of the exhaust air is increased, and the temperature of the CF 12 is further increased, so that the combustion is possible by the radiative heat from the CF 12 even when the proportion of the follow-up fuel is decreased from the time of start. The ratio of the follow-up fuel to the discharge fuel at this time is, for example, a ratio between 1:9 and 4:6. That is, the discharge fuel is injected more than the follow-up fuel. In addition, the radiative heat from the CF 12 makes it possible to form the flame front 16 on the upstream side of the CF 12. At this time, the controller 110 may decrease the exhaust air amount to move the flame front 16 to the upstream side of the CF 12. In addition, the flame front 16 may be moved to the upstream side of the CF 12 by adjusting the amount of fuel injected from the discharge fuel injector 13 and the follow-up fuel injector 14. At the time of warm-up, in the CF 12, the upstream side closer to the flame front 16 has a higher temperature TA.

[0047] The steady time refers to a time after the temperature of the combustor 1 reaches a steady temperature. The temperature of the exhaust air at this time is, for example, a temperature between 500° C and 800° C. At the time of steady operation, the temperature of the exhaust air is sufficiently increased, and the temperature of the CF 12 is also sufficiently increased, so that the discharge fuel can be burned without injecting the follow-up fuel. Therefore, the ratio of the follow-up fuel to the discharge fuel is, for example, 0:10. In this way, the stable diffusion combustion is possible with solely the discharge fuel by the radiative heat from the CF 12. In addition, the temperature TA of the CF 12 is also maintained by burning the discharge fuel. The follow-up fuel may be injected in a case where the discharge fuel is difficult to ignite (for example, in a case where the CO concentration is high and the H2 concentration is low). In this case, the same as the warm-up time may be used, or in a further case where the combustion is difficult, the same as the start time may be used.

[0048] FIG. 4 is a flowchart showing a control flow of the combustor 1 in the ECU 10. The routine shown in FIG. 4 is executed in the ECU 10 in response to the start of the SOFC 2. In S101, the controller 110 executes the start mode. The start mode is a mode executed at the time of the start of the combustor 1 (may be the time of the start of the SOFC 2), and is a mode in which the ignitability is increased by relatively increasing the amount of the follow-up fuel injected as compared with the amount of the discharge fuel. When the processing of S101 is completed, the processing proceeds to S102.

[0049] In S102, the controller 110 starts the fuel injection from the discharge fuel injector 13 and the follow-up fuel injector 14. At this time, the controller 110 reduces the amount of the discharge fuel injected from the discharge fuel injector 13 as compared with the amount of the follow-up fuel injected from the follow-up fuel injector 14. The fuel injection amount from the discharge fuel injector 13 and the follow-up fuel injector 14 at this time may be decided according to the logic stored in the storage unit 120. In addition, for example, the controller 110 may adjust the fuel injection amount according to the temperature detected by the temperature sensor 111. In addition, the controller 110 may control the exhaust air amount control valve 112 such that a predetermined amount of the exhaust air flows through the combustor 1. The ignitability of the fuel is related to the fuel injection amount, the exhaust air amount, and the temperature of the CF 12. Therefore, the relationship between the fuel injection amount, the exhaust air amount, and the temperature of the CF 12 that can provide the stable combustion may be obtained in advance by an experiment, a simulation, or the like, and may be stored in the storage unit 120. The exhaust air amount may be the opening degree of the exhaust air amount control valve 112. The controller 110 may decide the fuel injection amount from each injector and the opening degree of the exhaust air amount control valve 112 according to the temperature of the CF 12. The controller 110 may control the discharge fuel injector 13 and the follow-up fuel injector 14 such that the fuel injection amounts thereof are the decided fuel injection amounts, and control the exhaust air amount control valve 112 such that the exhaust air amount control valve 112 has the decided opening degree. The controller 110 increases the amount of the follow-up fuel in the combustor 1 to promptly increase the temperature of the CF 12. Since the temperature of the CF 12 is increased, it is possible to supply the air at a high temperature to the SOFC 2 through the MGT 3 and the regenerative heat exchanger 4, and thus it is possible to promptly increase the temperature of the SOFC 2. When the processing of S102 is completed, the processing proceeds to S103.

[0050] In S103, the controller 110 operates the ignition plug 15 to perform ignition. As a result, the controller 110 forms the flame front 16 near the ignition plug 15. When the processing of S103 is completed, the processing proceeds to S104.

[0051] In S104, the controller 110 determines whether the temperature of the CF 12 is higher than a first temperature. The first temperature is a temperature of the CF 12 at which it is possible to move the flame front 16 to the upstream side of the CF 12. The first temperature may be, for example, the ignition temperature of hydrogen when the air-fuel ratio is the stoichiometric air-fuel ratio. In addition, the first temperature is also a temperature at which the combustion is possible even when the temperature is transitioned to the warm-up mode. When the controller 110 makes an affirmative determination in S104, the process proceeds to S105, and when the controller 110 makes a negative determination in S104, the process of S104 is executed again. The follow-up fuel injected from the follow-up fuel injector 14 may be gradually decreased when the start mode is executed. Even in this case, the amount of the follow-up fuel is increased as compared with the amount of the discharge fuel.

[0052] In S105, the controller 110 executes the warm-up mode. The warm-up mode is a mode executed at the time of the warm-up of the combustor 1. The warm-up mode is a mode in which the controller 110 reduces the amount of the follow-up fuel, and is a mode in which the flame front 16 is formed on the upstream side of the CF 12. When the warm-up mode is executed, the controller 110 stops the ignition by the ignition plug 15. Even when the controller 110 stops the ignition by the ignition plug 15, the follow-up fuel and the discharge fuel burn by the diffusion combustion. When the process of S105 is completed, the process proceeds to S106.

[0053] In S106, the controller 110 decreases the amount of the follow-up fuel injected from the follow-up fuel injector 14 as compared with the amount of the follow-up fuel injected when the start mode is executed. At this time, the controller 110 controls the fuel injection from the discharge fuel injector 13 and the follow-up fuel injector 14 and the flow rate of the exhaust air such that the flame front 16 can be formed on the upstream side of the CF 12. The control may be performed, for example, according to the temperature detected by the temperature sensor 111. The fuel injection amount and the flow rate of the exhaust air according to the temperature in this case may be obtained in advance by an experiment, a simulation, or the like, and may be stored in the storage unit 120. In addition, the controller 110 may calculate the fuel injection amount and the opening degree of the exhaust air amount control valve 112 for forming the flame front 16 on the upstream side of the CF according to the logic stored in the storage unit 120. When the process of S106 is completed, the process proceeds to S107.

[0054] In S107, the controller 110 determines whether the temperature of the CF 12 is higher than the second temperature. The second temperature is a temperature higher than the first temperature, and is a temperature at which the CF 12 can burn with solely the discharge fuel without injecting the follow-up fuel. In addition, the second temperature is a temperature at which the combustion is possible even when the temperature is transitioned to the steady mode. When the temperature of the upstream end surface of the CF 12 is increased by executing the warm-up mode and reaches the second temperature, the combustion is possible with solely the discharge fuel without the follow-up fuel. When the controller 110 makes an affirmative determination in S107, the process proceeds to S108, and when the controller 110 makes a negative determination in S107, the process of S107 is executed again. The follow-up fuel injected from the follow-up fuel injector 14 may be gradually decreased when the warm-up mode is executed. Even in this case, the follow-up fuel is not decreased to 0.

[0055] In S108, the controller 110 executes the steady mode. The steady mode is a mode executed when the combustor 1 is in a steady state, and is a mode in which the follow-up fuel is stopped and the combustion is performed with the discharge fuel. When the process of S108 is completed, the process proceeds to S109.

[0056] In S109, the controller 110 stops the injection of the follow-up fuel from the follow-up fuel injector 14. As a result, the controller 110 causes the fuel injection to be performed solely by the discharge fuel injector 13. The discharge fuel at this time is in a state in which the concentration of the fuel component is low, but the diffusion combustion is possible due to the radiative heat from the CF 12. When the process of S109 is completed, the present routine ends.

[0057] As described above, according to the present embodiment, since the follow-up fuel is supplied from the follow-up fuel injector 14 at the time of start, the flame front 16 can be more reliably formed on the downstream side of the CF 12. As a result, the temperature of the CF 12 can be increased. It is possible to promote the lean combustion by the effect of the heat storage and the radiative heat of the CF 12, and to further reduce the amount of NOx emitted. Here, in a case where the follow-up fuel is supplied, a relatively large amount of fuel is supplied, and thus there is a possibility that the NOx increases. On the other hand, according to the present embodiment, it is possible to promote the mixing of the fuel and the air by performing the combustion downstream of the CF 12, and further, it is possible to perform the lean combustion while the generation of the NOx is suppressed by using the heat storage and the radiative heat of the CF 12. In addition, the controller 110 can reduce the amount of the follow-up fuel used by gradually decreasing the amount of the follow-up fuel within a range in which the stability of the combustion can be ensured. In addition, since the controller 110 adjusts the position of the flame front 16 according to the temperature of the CF 12, the stability of the combustion can be measured.Second Embodiment

[0058] FIG. 5A is a diagram showing a state of a flame at the time of start according to the second embodiment. FIG. 5B is a diagram showing a state of a flame at the time of warm-up according to the second embodiment. FIG. 5C is a diagram showing a state of a flame at a time of steady operation according to the second embodiment. The discharge fuel injector 13 according to the second embodiment is disposed downstream of the CF 12 and upstream of the ignition plug 15.

[0059] In the second embodiment, at the time of start, the controller 110 injects the discharge fuel from the discharge fuel injector 13, injects the follow-up fuel from the follow-up fuel injector 14, and further performs ignition by the ignition plug 15. As a result, the flame front 16 is generated on the downstream side of the discharge fuel injector 13. As a result, the controller 110 increases the temperature of the CF 12.

[0060] In addition, in a case where the temperature TA of the CF 12 is increased to a temperature at which the flame front 16 can be formed downstream of the discharge fuel injector 13 even when the follow-up fuel is decreased, the operation is transitioned to the warm-up operation. At this time, the controller 110 reduces the amount of the follow-up fuel. When the amount of the follow-up fuel is reduced, the amount of the follow-up fuel injected may be reduced such that the position of the flame front 16 gradually moves from the position of the ignition plug 15 to the position of the discharge fuel injector 13.

[0061] Further, even when the injection of the follow-up fuel is stopped and the temperature of the CF 12 is increased to a temperature at which the discharge fuel can be burned, the operation is transitioned to the steady operation. At this time, the controller 110 sets the injection amount of the follow-up fuel to 0 and injects solely the discharge fuel as the fuel.

[0062] As described above, according to the second embodiment, the effect of the heat storage and the heat reflection from the CF 12 at the time of the steady operation is small, but it is possible to directly supply the high-temperature gas to the downstream of the CF 12.

Claims

1. A combustor comprising:a heat storage body through which a gas and a liquid pass;a first fuel injector provided upstream of the heat storage body in a direction in which the gas and the liquid flow, the first fuel injector being configured to inject first fuel;an igniter provided downstream of the heat storage body in the direction in which the gas and the liquid flow; anda second fuel injector provided downstream of the first fuel injector and upstream of the igniter in the direction in which the gas and the liquid flow, the second fuel injector being configured to inject second fuel having ignitability lower than ignitability of the first fuel.

2. The combustor according to claim 1, further comprising:a controller configured to executea start mode of causing the first fuel injector to inject the first fuel, causing the second fuel injector to inject the second fuel in an amount greater than the first fuel, and performing ignition with the igniter,a warm-up mode of causing the first fuel injector to inject the first fuel, causing the second fuel injector to inject the second fuel in an amount less than the first fuel, and causing a flame front to move upstream of a flame front in the warm-up mode in the direction in which the gas and the liquid flow, the warm-up mode being executed after the start mode, anda steady mode of causing the second fuel injector to stop injecting the second fuel, and causing a flame to be generated through injection of the first fuel from the first fuel injector, the steady mode being executed after the warm-up mode.

3. The combustor according to claim 1, wherein the heat storage body is a ceramic foam.

4. The combustor according to claim 1, wherein:the first fuel is the same fuel as fuel that is supplied to a fuel cell; andthe second fuel is fuel that is discharged from the fuel cell without being used in the fuel cell.

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