JP7615787B2 - Combustor and fuel cell system - Google Patents

Description

The present invention relates to a combustor and a fuel cell system.

Conventionally, combustors that mix and burn fuel gas and air have been proposed. For example, Patent Document 1 describes a combustor that includes a fuel cell that generates power using fuel gas and oxidant gas, and a combustor that mixes and burns anode offgas (fuel gas) discharged from the anode of the fuel cell and cathode offgas (air) discharged from the cathode of the fuel cell. In the combustor of Patent Document 1, multiple cathode offgas outlets are formed so that the cathode offgas is obliquely ejected between multiple anode offgas outlets. Patent Document 2 describes a combustor that arranges a swirl plate with multiple inclined holes inclined to the air flow direction in an air flow path, thereby making the air passing through the inclined holes a swirling flow. Patent Document 3 describes a combustor that promotes mixing of fuel gas and air by supplying air and fuel gas in the same direction and then ejecting the air from a direction perpendicular to the ejection direction of the fuel gas.

JP 2018-181840 A JP 2016-118353 A JP 2017-33869 A

Since each of the combustors described above uses diffusion combustion, it is necessary to make the air flow rate greater than the fuel gas flow rate to stabilize the combustion. However, in configurations in which air is ejected from multiple ejection holes, such as the combustors of Patent Documents 1 and 2, the pressure loss in the air flow path increases. Also, in the combustor of Patent Document 3, the air flow path is bent so that the air ejection direction is perpendicular to the fuel gas ejection direction, so the pressure loss increases. When the air pressure loss increases in this way, it becomes necessary to enlarge the air blower to ensure the air flow rate, which may increase noise and costs.

The main objective of this invention is to reduce air pressure loss and stabilize combustion in the combustor.

The present invention takes the following measures to achieve the above-mentioned main objective.

The combustor of the present invention comprises:
A combustor that mixes and burns fuel gas and air,
a gas flow pipe having a closed end in an axial direction and a plurality of ejection holes formed in a side wall thereof for ejecting the fuel gas that has flowed toward the end to the outside;
a guide tube having an open axial end and arranged coaxially with the gas flow pipe so as to surround the gas flow pipe, the guide tube guiding air to flow between the gas flow pipe and the guide tube toward the end;
an ignition device that ignites a mixed gas of the fuel gas ejected from the ejection hole into the guide pipe and the air that flows between the gas flow pipe and the guide pipe;
The gist of the invention is to provide the following:

In the combustor of the present invention, an ignition device ignites a mixed gas of fuel gas ejected from the gas flow pipe between the nozzle hole and the guide pipe, and air flowing between the gas flow pipe and the guide pipe, to cause combustion. Therefore, there is no need for the air to pass through the nozzle hole or to bend its flow direction, and since the tip of the guide pipe is open, the flow of the mixed gas and its combustion gas can be aligned with the flow direction of the air, reducing air pressure loss. In addition, the fuel gas can be ejected perpendicular to the air and forcibly mixed, so the fuel gas and air can be mixed efficiently. Therefore, air pressure loss can be suppressed and combustion in the combustor can be stabilized.

In the combustor of the present invention, the guide tube may have an extension section extending parallel to the axial direction so that the cross-sectional area of the space between the guide tube and the gas flow tube is larger than the cross-sectional area of the gas flow tube, and an expanding section that is continuous with the extension section and expands in diameter from a point facing the gas flow tube toward the tip. In this way, a larger amount of air than the combustion gas can be circulated to increase the air flow rate, thereby improving the mixing efficiency and stabilizing the combustion. In addition, the mixed gas can be diffused to reduce the flow rate of the mixed gas, preventing the flame length from becoming longer and reducing the combustion range. This prevents the object to be heated from becoming locally hot, and allows the object to be heated appropriately.

In the combustor of the present invention, the guide tube may have a notch formed on the edge of the tip, and the ignition device may be disposed radially outside the guide tube and ignite the mixed gas by discharging electricity into the guide tube through the notch. In this way, ignition can be reliably performed at a position closer to where the fuel gas and air are mixed.

In the combustor of the present invention, the gas flow pipe may be configured such that the multiple ejection holes are equally spaced in the circumferential direction and multiple pairs are formed at positions facing each other in the radial direction. In this way, the fuel gas can be ejected evenly into the space between the guide pipe and the gas flow pipe, preventing unevenness in the concentration of the mixed gas, thereby making the combustion more stable.

The fuel cell system of the present invention comprises:
a fuel cell stack that generates power using a reformed gas containing hydrogen and an oxidant gas containing oxygen;
a reformer that reforms a raw fuel gas to generate a reformed gas;
any one of the combustors described above that combusts a mixed gas of fuel gas and air as off-gas discharged from the fuel cell stack and supplies the combustion gas toward the reformer;
The gist of the invention is to provide the following:

The fuel cell system of the present invention includes a fuel cell stack, a reformer, and any of the combustors described above. Therefore, as described above, it is possible to suppress air pressure loss and stabilize combustion in the combustor, and therefore it is possible to appropriately raise the temperature of the reformer and ensure a stable supply of reformed gas.

1 is a diagram showing an outline of the configuration of a fuel cell system 10. FIG. 2 is a diagram showing an outline of the configuration of a combustion unit 22. FIG. 2 is a perspective view of a combustor 30 disposed in the bulkhead 26. FIG. FIG. 2 is a perspective view including a partial cross section of a combustor 30. 2 is an explanatory diagram showing the state of combustion in a combustor 30. FIG.

Next, we will explain the form for implementing the present invention.

Figure 1 is a schematic diagram showing the configuration of a fuel cell system 10, and Figure 2 is a schematic diagram showing the configuration of a combustion unit 22. As shown in Figure 1, the fuel cell system 10 of this embodiment includes a power generation module 20, a raw fuel gas supply device 40, an air supply device 50, a reforming water supply device 60, and an exhaust heat recovery device 70.

The power generation module 20 includes a fuel cell stack 21 and a combustion unit 22, and the fuel cell stack 21 and the combustion unit 22 are housed in a box-shaped module case 29 formed from a heat insulating material. The fuel cell stack 21 is configured as a solid oxide fuel cell in which a plurality of fuel cells are arranged, each of which includes a solid electrolyte made of an oxygen ion conductor, an anode provided on one side of the solid electrolyte, and a cathode provided on the other side of the solid electrolyte. The fuel cell stack 21 generates electricity through an electrochemical reaction between hydrogen in a fuel gas (reformed gas) supplied to the anode and oxygen in air (oxidizer gas) supplied to the cathode. The output terminal of the fuel cell stack is connected to a power line connecting a commercial power source and a load via a power conditioner (not shown). The DC power output from the fuel cell stack 21 to the output terminal is added to the AC power from the commercial power source through voltage conversion and DC/AC conversion by the power conditioner and supplied to the load.

2, the combustion unit 22 includes a vaporizer 23, a reformer 24, and a combustor 30. The vaporizer 23 and the reformer 24 are arranged in a combustion chamber 25 through which combustion gas flows, and the combustor 30 is arranged in a partition 26 between the combustion chamber 25 and the air introduction chamber 27 through which air is introduced. The vaporizer 23 evaporates reforming water to generate steam and preheats raw fuel gas (e.g., natural gas or LP gas). The reformer 24 generates fuel gas (reformed gas) from the raw fuel gas and steam. The vaporizer 23 and the reformer 24 may be integrally configured. The combustor 30 supplies heat (combustion gas) required for the generation of steam in the vaporizer 23 and the steam reforming reaction in the reformer 24 to the combustion chamber 25.

The raw fuel gas supply device 40 includes a raw fuel gas supply pipe 41 that connects the gas supply source 1 that supplies the raw fuel gas to the combustion unit 22 (vaporizer 23), a raw fuel gas supply valve 42 (two valves), a raw fuel gas pump 43, and a desulfurizer 44 that are provided in the raw fuel gas supply pipe 41 in order from the gas supply source 1 side. The raw fuel gas supply device 40 supplies raw fuel gas from the gas supply source 1 to the combustion unit 22 through the desulfurizer 44 by operating the raw fuel gas pump 43 with the raw fuel gas supply valve 42 open. The desulfurizer 44 removes sulfur contained in the raw fuel gas, and can employ, for example, a room temperature desulfurization method in which sulfur compounds are adsorbed and removed by an adsorbent such as zeolite. The raw fuel gas supplied to the vaporizer 23 of the combustion unit 22 is preheated in the vaporizer 23, and then supplied to the reformer 24, where it is reformed into fuel gas (reformed gas). The reformed fuel gas is then supplied to the anode of the fuel cell stack 21.

The air supply device 50 includes an air supply pipe 52 that connects a filter 51 that communicates with the outside air to the fuel cell stack 21, and an air blower 53 that is provided in the air supply pipe 52. The air supply device 50 operates the air blower 53 to supply air sucked in through the filter 51 to the cathode of the fuel cell stack 21.

The reforming water supply device 60 includes a reforming water tank 61 that stores reforming water, a reforming water supply pipe 62 that connects the reforming water tank 61 to the combustion unit 22 (vaporizer 23), and a reforming water pump 63 provided on the reforming water supply pipe 62. The reforming water supply device 60 operates the reforming water pump 63 to supply reforming water from the reforming water tank 61 to the vaporizer 23 of the combustion unit 22. The reforming water supplied to the vaporizer 23 is converted into steam by the vaporizer 23 and used in the steam reforming reaction in the reformer 24.

The combustor 30 is supplied with fuel gas (fuel off-gas, anode off-gas, solid arrow in FIG. 2) and air (oxidant off-gas, cathode off-gas, dashed arrow in FIG. 2) that have passed through the fuel cell stack 21 (each fuel cell), and burns the mixed gas. The combustor 30 supplies the combustion gas generated by the combustion of the mixed gas to the vaporizer 23 and reformer 24 of the combustion chamber 25. The supplied combustion gas flows through the combustion chamber 25 (dotted arrow in FIG. 2) and is discharged from the exhaust hole 25a of the combustion chamber 25 into the module case 29. The discharged combustion exhaust gas is supplied to the heat exchanger 75 via the combustion catalyst 28. The combustion catalyst 28 is an oxidation catalyst that catalyzes the off-gas that remains unburned in the combustor 30 to be re-burned.

The exhaust heat recovery device 70 includes a hot water tank 71 for storing hot water, a heat exchanger 75, a circulation pipe 72 that connects the hot water tank 71 and the heat exchanger 75 to form a circulation path for the hot water, and a circulation pump 73 provided on the circulation pipe 72. The exhaust heat recovery device 70 operates the circulation pump 73 to circulate the hot water, thereby taking out the hot water from the bottom of the hot water tank 71, heating it by heat exchange with the combustion exhaust gas in the heat exchanger 75, and returning the heated hot water to the top of the hot water tank 71. The heat exchanger 75 is connected to the reforming water tank 61 via a condensed water supply pipe 76 and is connected to the outside air via an exhaust pipe 77. The combustion exhaust gas supplied to the heat exchanger 75 is cooled by heat exchange with the hot water, and the water vapor component is condensed and collected in the reforming water tank 61 via the condensed water supply pipe 76 and a water purifier (not shown). The remaining exhaust gas is discharged to the outside air via exhaust pipe 77.

Here, the detailed configuration of the combustor 30 will be described. FIG. 3 is a perspective view of the combustor 30 arranged in the partition wall 26, and FIG. 4 is a perspective view including a partial cross section of the combustor 30. The combustor 30 includes a fuel gas flow pipe 32, a guide pipe 34, and an ignition plug 38.

The fuel gas flow pipe 32 is configured as a cylindrical member with its front and rear ends in the axial direction closed. This fuel gas flow pipe 32 is connected to the fuel gas introduction pipe 31 extending vertically so as to introduce the fuel gas (combustion off-gas) that has passed through the fuel cell stack 21 to the combustion unit 22 side, and is arranged so that its axial direction is horizontal. The rear end of the fuel gas flow pipe 32 is located in the air introduction chamber 27, and the tip of the fuel gas flow pipe 32 is located closer to the combustion chamber 25 than the partition wall 26. In addition, the fuel gas flow pipe 32 has a plurality of ejection holes 33 formed in the side wall near the tip, penetrating in the radial direction. All of the ejection holes 33 have an elliptical shape with the axial direction of the fuel gas flow pipe 32 as the longitudinal direction, and are formed at positions spaced the same distance from the tip of the fuel gas flow pipe 32. In addition, the plurality of ejection holes 33 are formed in pairs at equal intervals in the circumferential direction and at positions facing each other in the radial direction so as to penetrate in the radial direction, and as an example, five pairs (10 in total) of ejection holes 33 are provided in the radial direction. As a result, the fuel gas that flows axially through the fuel gas flow pipe 32 toward the tip changes direction radially as it bends near the tip, and is ejected to the outside from the multiple ejection holes 33.

The guide tube 34 is configured as a cylindrical member (annular member) with open axial ends. The guide tube 34 is arranged coaxially with the fuel gas flow tube 32 so as to surround the fuel gas flow tube 32, and forms an annular flow path 30a between the guide tube 34 and the outer circumferential surface of the fuel gas flow tube 32. The guide tube 34 also guides the air (oxidizer off-gas) introduced into the air introduction chamber 27 by an air introduction tube (not shown) to flow from the rear end into the flow path 30a, and the air flows through the flow path 30a to the tip side in parallel with the flow direction of the fuel gas in the fuel gas flow tube 32. In this embodiment, the fuel gas flow tube 32 and the guide tube 34 are configured so that the cross-sectional area of the annular flow path 30a is larger than the cross-sectional area of the fuel gas flow tube 32, and a larger amount of air can be supplied (flowed) than the fuel gas.

The guide pipe 34 has a different shape at the front end and rear end, with an extension 34a extending parallel to the axial direction with a constant inner and outer diameter formed at the rear end, and an enlarged diameter portion 34b continuing from the extension 34a and enlarging toward the front end formed at the front end. The extension 34a is formed to have a diameter that makes the cross-sectional area of the flow path 30a larger than the cross-sectional area of the fuel gas flow pipe 32. The extension 34a is supported so as to be fitted into the opening of the partition wall 26, and extends to near the center position in the longitudinal direction of the ejection hole 33 of the fuel gas flow pipe 32. That is, the guide pipe 34 has an extension 34a extending parallel to the axial direction to a position facing the ejection hole 33 of the fuel gas flow pipe 32, and the enlarged diameter portion 34b has a larger inner and outer diameter toward the front end than the position facing the ejection hole 33. Furthermore, the guide tube 34 has a notch 35 formed at the edge of the tip of the enlarged diameter portion 34b so that a portion of the circumferential direction penetrates in the radial direction.

The ignition plug 38 is configured to ignite a mixture of fuel gas ejected from the ejection hole 33 into the flow passage 30a and air flowing through the flow passage 30a by discharging a gas. The ignition plug 38 is disposed radially outside the guide tube 34, and discharges a gas through the cutout 35 toward the inside of the guide tube 34 (radially inward).

Here, FIG. 5 is an explanatory diagram showing the state of combustion in the combustor 30. As shown in the figure, the fuel gas introduced from the fuel gas introduction pipe 31 flows in the axial direction (horizontal direction) through the fuel gas flow pipe 32 and is ejected radially outward from the multiple ejection holes 33 so as to be perpendicular to the axial direction (solid line arrow in FIG. 5). In addition, the air guided by the guide pipe 34 flows linearly from the air introduction chamber 27 through the flow path 30a parallel to the axial direction (dotted line arrow in FIG. 5). For this reason, it is not necessary to pass the air through an ejection hole smaller than the flow path or to bend the flow direction of the air, so that it is possible to prevent the flow resistance of the air from increasing. Then, the air flowing through the flow path 30a is mixed with the fuel gas ejected into the flow path 30a to generate a mixed gas. The guide pipe 34 has an open tip, and the flow direction of the generated mixed gas and its combustion gas can be aligned in the same direction as the flow direction of the air, so that it is possible to prevent the flow of the air in the flow path 30a from being affected. As a result, the pressure loss of the air can be reduced. In addition, by ejecting the fuel gas from the ejection hole 33 perpendicular to the air in the flow path 30a, mixing can be forced, improving the mixing efficiency.

In addition, since the cross-sectional area of the flow path 30a is larger than that of the fuel gas flow pipe 32, a larger amount of air can be flowed than the fuel gas, and the flow rate of the air can be increased, thereby improving the mixing efficiency. In addition, the fuel gas and the air are mixed at a location near the ejection hole 33, and the guide pipe 34 having the expanded diameter portion 34b is expanded at the tip side from the location facing the ejection hole 33 (mixing location), so that the cross-sectional area of the tip is the largest. As a result, the mixed gas flows toward the combustion chamber 25 while diffusing, so the flow rate decreases, and the air flow rate can be increased to increase the mixing efficiency up to the mixing location, and the flow rate can be quickly decreased after mixing. As a result, the flame length in the combustion of the mixed gas can be prevented from becoming long, the combustion range can be kept small, and the burner hole load can be reduced. This makes it possible to prevent the flame length from becoming too long or the flame from being blown away. The combustor 30 is arranged to supply combustion gas toward the combustion chamber 25 (reformer 24), and shortening the flame length prevents localized heating of the reformer 24, allowing the reformer 24 to be appropriately heated. Furthermore, because localized heating can be prevented, the distance between the combustor 30 and the reformer 24 can be shortened, allowing the combustion unit 22 (power generation module 20) to be made smaller.

The ignition plug 38 ignites the mixed gas by discharging electricity toward the mixing location on the radial inside through the notch 35. This allows the mixed gas to be reliably ignited by discharging electricity toward the mixed gas at a location closer to the mixing location. The fuel gas flow pipe 32 has a plurality of ejection holes 33 that are equally spaced in the circumferential direction and formed in a plurality of pairs in the radial direction, which makes it easier to eject the fuel gas evenly into the flow path 30a and perpendicular to the axial direction, thereby suppressing unevenness in the concentration of the mixed gas and making the combustion more stable. In this way, the combustor 30 supplies the combustion gas of the flame that combusts the mixed gas to the combustion chamber 25, so that the vaporizer 23 and the reformer 24 in the combustion chamber 25 can be appropriately heated.

In the combustor 30 of the fuel cell system 10 described above, a mixture of fuel gas that flows through the fuel gas flow pipe 32 and is ejected from the ejection hole 33, and air that flows through the flow path 30a between the guide pipe 34 and the fuel gas flow pipe 32 is ignited and burned. This reduces the pressure loss of the air and stabilizes the combustion in the combustor 30. In addition, in the fuel cell system 10, the vaporizer 23 and the reformer 24 can be appropriately heated to stably supply the reformed gas.

In addition, the mixed gas is diffused along the expanded diameter portion 34b, which prevents the flame length from becoming too long and allows the reformer 24 to be appropriately heated.

In addition, the spark plug 38 discharges electricity into the guide tube 34 through the notch 35, ensuring reliable ignition of the mixed gas.

In addition, multiple pairs of ejection holes 33 are formed at equal intervals in the circumferential direction on the side wall of the fuel gas flow pipe 32, which prevents unevenness in the concentration of the mixed gas and makes combustion more stable.

In the above-described embodiment, the multiple ejection holes 33 are formed in pairs at equal intervals in the circumferential direction of the side wall of the fuel gas flow pipe 32 and at positions facing each other in the radial direction, but this is not limited to the above, and the ejection holes 33 may be formed at different intervals or at positions that do not face each other in the radial direction. In addition, the ejection holes 33 are not limited to being oval in shape, and may be other shapes such as circular or rectangular. In addition, the ejection holes 33 are not limited to being formed at positions at the same distance from the tip of the fuel gas flow pipe 32, and may be formed at positions at different distances. For example, the multiple ejection holes 33 may be formed in a staggered pattern at positions that are staggered in a side view.

In the embodiment, the guide tube 34 is provided with a notch 35, but this is not limited thereto, and the notch 35 may not be provided. In such a case, the ignition plug 38 may discharge, for example, from an opening at the tip of the guide tube 34 toward the inside of the guide tube 34.

In the embodiment, the guide tube 34 has the extension portion 34a and the enlarged diameter portion 34b, but this is not limited, and the guide tube 34 may not have the enlarged diameter portion 34b. That is, the guide tube 34 may be formed to extend with a constant inner and outer diameter over the entire axial length. Also, the cross-sectional area of the flow path 30a in the extension portion 34a is larger than the cross-sectional area of the fuel gas flow tube 32, but this is not limited, and both may have the same cross-sectional area. However, in order to ensure the air flow rate and stabilize the combustion, it is preferable to have the same cross-sectional area as in the embodiment.

In the embodiment, the fuel gas flow pipe 32 extends in a direction perpendicular to the fuel gas introduction pipe 31, but this is not limited thereto, and the fuel gas flow pipe 32 may extend in the same direction as the fuel gas introduction pipe 31. For example, the axial direction of the fuel gas flow pipe 32 may be vertical, the combustor 30 may be configured to supply combustion gas (flame) upward, and the combustion chamber 25 may be disposed above the combustor 30.

In the embodiment, the fuel gas flow pipe 32 and the guide pipe 34 are cylindrical, but the present invention is not limited to this and may be formed into a polygonal or elliptical cylindrical shape. In addition, the air introduced from the air introduction pipe to the air introduction chamber 27 flows through the guide pipe 34, but the present invention is not limited to this and the air introduction pipe and the guide pipe 34 may be connected and the air may be introduced directly from the air introduction pipe to the guide pipe 34.

In the embodiment, the combustor 30 is illustrated as being used in the fuel cell system 10, but the present invention is not limited to this and may be used in other systems.

The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem will be explained. In the embodiment, the fuel gas flow pipe 32 corresponds to the "gas flow pipe", the guide pipe 34 corresponds to the "guide pipe", and the ignition plug 38 corresponds to the "ignition device". The extension portion 34a corresponds to the "extension portion", and the enlarged diameter portion 34b corresponds to the "enlarged diameter portion". The notch portion 35 corresponds to the "notch portion". In addition, the fuel cell stack 21 corresponds to the "fuel cell stack", the reformer 24 corresponds to the "reformer", and the combustor 30 corresponds to the "combustor".

The correspondence between the main elements of the embodiment and the main elements of the invention described in the Means for Solving the Problem column does not limit the elements of the invention described in the Means for Solving the Problem column, since the embodiment is an example for specifically explaining the form for implementing the invention described in the Means for Solving the Problem column. In other words, the interpretation of the invention described in the Means for Solving the Problem column should be made based on the description in that column, and the embodiment is merely a specific example of the invention described in the Means for Solving the Problem column.

The above describes the form for carrying out the present invention using an embodiment, but the present invention is not limited to such an embodiment, and it goes without saying that the present invention can be carried out in various forms without departing from the spirit of the present invention.

The present invention can be used in the combustion chamber manufacturing industry, etc.

1 Gas supply source, 10 Fuel cell system, 20 Power generation module, 21 Fuel cell stack, 22 Combustion unit, 23 Carburetor, 24 Reformer, 25 Combustion chamber, 25a Exhaust hole, 26 Partition, 27 Air introduction chamber, 28 Combustion catalyst, 29 Module case, 30 Combustor, 30a Flow path, 31 Fuel gas introduction pipe, 32 Fuel gas flow pipe, 33 Jet hole, 34 Guide pipe, 34a Extension portion, 34b Enlarged diameter portion, 35 Notch portion, 37 Spark plug, 40 Raw fuel gas supply device, 41 Raw fuel gas supply pipe, 42 Raw fuel gas supply valve, 43 Raw fuel gas pump, 44 Desulfurizer, 50 Air supply device, 51 Filter, 52 Air supply pipe, 53 Air blower, 60 Reforming water supply device, 61 Reforming water tank, 62 Reformed water supply pipe, 63 reformed water pump, 70 exhaust heat recovery device, 71 hot water tank, 72 circulation pipe, 73 circulation pump, 75 heat exchanger, 76 condensed water supply pipe, 77 exhaust pipe.

Claims (4)

A combustor that mixes and burns fuel gas and air,
a gas flow pipe having a closed end in an axial direction and a plurality of ejection holes formed in a side wall thereof for ejecting the fuel gas that has flowed toward the end to the outside;
a guide tube having an open axial end and arranged coaxially with the gas flow pipe so as to surround the gas flow pipe, the guide tube guiding air to flow between the gas flow pipe and the guide tube toward the end;
an ignition device that ignites a mixed gas of the fuel gas ejected from the ejection hole into the guide pipe and the air that flows between the gas flow pipe and the guide pipe;
Equipped with
The guide tube has a notch formed on the edge of the tip,
The ignition device is disposed radially outside the guide pipe and ignites the mixed gas by discharging electricity into the guide pipe through the notch.
Combustor . 2. The combustor of claim 1,
the guide pipe has an extension portion extending parallel to the axial direction so that a cross-sectional area of a space between the guide pipe and the gas flow pipe is larger than a cross-sectional area of the gas flow pipe, and an expanded diameter portion continuing from the extension portion and expanding in diameter from a position facing the ejection hole of the gas flow pipe toward a tip thereof. The combustor according to claim 1 or 2 ,
the gas flow pipe has a plurality of pairs of the ejection holes formed at equally spaced intervals in a circumferential direction and at positions opposed to each other in a radial direction. a fuel cell stack that generates power using a reformed gas containing hydrogen and an oxidant gas containing oxygen;
a reformer that reforms a raw fuel gas to generate a reformed gas;
a combustor according to any one of claims 1 to 3 , which combusts a mixed gas of fuel gas and air as off-gas discharged from the fuel cell stack, and supplies the combustion gas to the reformer;
A fuel cell system comprising:

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