combustor

Abstract

To solve a problem that when a ceramic foam is provided to prevent a flame from flowing back to an upstream side, flowing resistance of an air-fuel mixture increases.SOLUTION: A combustor 10 includes: a cylindrical body 11; a ceramic foam 21 with a continuous air hole; and an ignition plug 20 mounted to the cylindrical body 11. The cylindrical body 11 includes: a first supply port 13 serving as a fuel supply port; a second supply port 14 serving as an air supply port; and a discharge port 15 of combustion gas. The ceramic foam 21 is located on the downstream side of the first supply port 13 and the upstream side of the ignition plug 20 in the cylindrical body 11. The ceramic foam 21 has an air gap 21S that extends along a central axis CL of the cylindrical body 11 and is opened on an end surface on the downstream side in the ceramic foam 21.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a combustor. [Background technology]

[0002] The combustor in Patent Document 1 includes a cylindrical outer wall, a main burner, a pilot burner, and an ignition device. The main burner and the pilot burner are connected to the outer wall. Both the main burner and the pilot burner are connected to sources of combustion gas and combustion air. Therefore, a mixture of combustion gas and air is supplied to the inside of the outer wall via the main burner and the pilot burner. The ignition device ignites the mixture supplied to the inside of the outer wall. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-280215 Summary of the Invention [Problem to be solved by the invention]

[0004] In a combustor, in order to perform stable combustion even when the combustible component fraction in the fuel or the oxygen fraction in the air is low, it may be necessary to use a pilot burner with a high concentration of combustible fuel or to stabilize the flame by swirling flow. In such a combustor, stable combustion may be difficult depending on the flow rate of the mixture, the heat value of the fuel, and the oxygen concentration in the air. Therefore, a premixed combustor using ceramic foam as in Patent Document 1 has been proposed to perform stable combustion under lean mixture conditions. However, in a combustor like that in Patent Document 1, there is a problem that the resistance when the mixture flows through the ceramic foam is large. [Means for solving the problem]

[0005] In order to solve the above problems, the present invention provides a combustor comprising a cylindrical body, a ceramic foam having continuous pores, and an ignition plug attached to the cylindrical body, wherein the cylindrical body has a fuel supply port, an air supply port, and a combustion gas exhaust port, and when the fuel supply port side is the upstream side and the exhaust port side is the downstream side, the ceramic foam is located downstream of the fuel supply port inside the cylindrical body and upstream of the ignition plug, and the ceramic foam extends along the central axis of the cylindrical body and has a gap that opens at the downstream end face of the ceramic foam. Effect of the Invention

[0006] According to the present invention, it is possible to suppress the flow resistance to the mixture flowing through the combustor and the resulting increase in pressure loss while suppressing the backflow and blow-away of the flame. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a combustor. [Diagram 2] FIG. 2 is an explanatory diagram showing the flow velocity of the mixture inside the combustor. [Diagram 3] FIG. 3 is a cross-sectional view of a modified ceramic foam. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] <Outline of combustor configuration> As shown in FIG. 1, the combustor 10 includes a cylindrical body 11. The cylindrical body 11 includes an outer cylinder 12 and an inner cylinder 17. In FIG. 1, the inner cylinder 17 and the like are illustrated by solid lines through the outer cylinder 12. The outer cylinder 12 is cylindrical with a cavity inside. Specifically, the outer cylinder 12 includes a cylindrical circumferential wall 12A, a first end wall 12B that closes an opening on one side of the circumferential wall 12A, and a second end wall 12C that closes an opening on the other side of the circumferential wall 12A. The central axis CL of the outer cylinder 12 is the central axis of the cylindrical body 11.

[0009] The outer cylinder 12 also has a first supply port 13 as a fuel supply port, a second supply port 14 as an air supply port, and an exhaust port 15. The first supply port 13 is cylindrical. The first supply port 13 penetrates the first end wall 12B. That is, the first supply port 13 communicates the inside and outside of the outer cylinder 12. The first supply port 13 receives a supply of fuel from a fuel supply source 30. The fuel supply source 30 is, for example, a fuel cell. Therefore, the first supply port 13 receives a supply of reacted exhaust fuel gas discharged from the anode of the fuel cell. Therefore, the combustor 10 of this embodiment combusts residual fuel gas such as lean hydrogen and carbon monoxide.

[0010] The second supply port 14 is cylindrical. The second supply port 14 penetrates the circumferential wall 12A near the first end wall 12B. That is, the second supply port 14 communicates the inside and outside of the outer cylinder 12. The second supply port 14 receives a supply of air from an air supply source 40. The air supply source 40 is, for example, a fuel cell. Therefore, the second supply port 14 receives a supply of reacted air in which some of the oxygen has been consumed, which is discharged from the cathode of the fuel cell.

[0011] The exhaust port 15 is cylindrical. The exhaust port 15 penetrates the second end wall 12C. That is, the exhaust port 15 communicates the inside and outside of the outer cylinder 12. The exhaust port 15 discharges the combustion gas in the cylindrical body 11. The exhaust port 15 is connected to a device that utilizes the thermal energy of the combustion gas. Examples of this type of device include a turbine for generating electricity, a compressor for compressing air, and a heat exchanger for heating other fluids.

[0012] The inner cylinder 17 is generally cylindrical. The outer diameter of the inner cylinder 17 is smaller than the inner diameter of the outer cylinder 12. The inner cylinder 17 is located inside the outer cylinder 12. The central axis of the inner cylinder 17 coincides with the central axis CL of the outer cylinder 12. The inner cylinder 17 can be roughly divided into an upstream portion 17A and a downstream portion 17B. The upstream portion 17A is cylindrical. The upstream end of the upstream portion 17A is connected to the first end wall 12B of the outer cylinder 12. Therefore, the inside of the upstream portion 17A is connected to the inside of the first supply port 13. The upstream portion 17A also has a plurality of through holes 18. Each through hole 18 is located near the upstream end of the upstream portion 17A. Each through hole 18 is arranged in the circumferential direction.

[0013] The downstream portion 17B is generally cylindrical. The diameter of the downstream portion 17B decreases toward the downstream side. The upstream end of the downstream portion 17B is connected to the downstream end of the upstream portion 17A. The downstream end of the downstream portion 17B is connected to the second end wall 12C. Therefore, the inside of the upstream portion 17A is in communication with the inside of the discharge port 15. The downstream portion 17B has a plurality of through holes 19. The through holes 19 are aligned in the circumferential direction.

[0014] The combustor 10 includes an ignition plug 20. The ignition plug 20 is attached to the cylindrical body 11. Specifically, the ignition plug 20 is located near the downstream end of the upstream portion 17A of the inner cylinder 17. The tip of the ignition plug 20 is located inside the inner cylinder 17. Specifically, the tip of the ignition plug 20 is located radially outward of a gap 21S of a ceramic foam 21, which will be described later, rather than downstream of the gap 21S. The ignition plug 20 ignites a mixture of hydrogen gas and air by spark discharge.

[0015] <Ceramic foam composition> As shown in FIG. 1, the combustor 10 includes a ceramic foam 21. The material of the ceramic foam 21 is a ceramic that can withstand the combustion heat of the air-fuel mixture, such as alumina, cordierite, silicon carbide, aluminum titanate, or a mixture of these. The ceramic foam 21 has continuous pores. That is, the ceramic foam 21 has countless pores. In the ceramic foam 21, these pores are connected to each other. The porosity of the ceramic foam 21 is, for example, 0.01 PPI or more and 1000 PPI or less. In the drawing, the continuous pores of the ceramic foam 21 are simply illustrated by dots.

[0016] The ceramic foam 21 has a cylindrical shape. Therefore, the ceramic foam 21 has voids 21S in addition to the above-mentioned continuous pores. The voids 21S are open at an end face of the ceramic foam 21 on the upstream side and are also open at an end face of the ceramic foam 21 on the downstream side.

[0017] The ceramic foam 21 is located in the upstream portion 17A of the inner cylinder 17. More specifically, the ceramic foam 21 is located downstream of the first supply port 13 and upstream of the ignition plug 20. The outer diameter of the ceramic foam 21 is approximately the same as the inner diameter of the upstream portion 17A of the inner cylinder 17. The outer peripheral surface of the ceramic foam 21 is in contact with the inner peripheral surface of the upstream portion 17A. That is, the central axis of the ceramic foam 21 coincides with the central axis CL of the outer cylinder 12, which is the central axis of the inner cylinder 17. The void 21S extends along the central axis CL. More specifically, the central axis of the void 21S coincides with the central axis CL.

[0018] <Operation of the embodiment> 2, the position of the upstream end of the ceramic foam 21 is designated as position X0. A position downstream of position X0 is designated as position X1. In FIG. 2, the flow velocity of the air-fuel mixture is diagrammatically illustrated by the length of the arrow.

[0019] In the vicinity of position X0, the flow velocity of the mixture is fast in the voids 21S. However, the mixture flowing through the continuous pores of the ceramic foam 21 is not yet subjected to much resistance, so the degree of decrease in the flow velocity is small. Therefore, in the vicinity of position X0, the flow velocity of the mixture is relatively uniform. If the flow velocity of the mixture in the vicinity of position X0 is relatively fast and uniform, the flame is difficult to maintain. In other words, in the vicinity of position X0 of the ceramic foam 21, the flame is difficult to backflow.

[0020] On the other hand, the flow of the air-fuel mixture is not easily impeded in gaps 21S. Rather, because a part of the air-fuel mixture flowing through the continuous pores of ceramic foam 21 flows into gaps 21S, the flow speed of the air-fuel mixture in gaps 21S becomes faster at position X1 on the downstream side. On the other hand, the flow speed of the air-fuel mixture flowing through the continuous pores of ceramic foam 21 becomes slower toward the downstream side. Therefore, at position X1, the effect of retaining the flame in the continuous pores of ceramic foam 21 is higher than at position X0, and the flame is less likely to be blown away.

[0021] <Effects of the embodiment> (1) According to the above embodiment, the flow speed of the air-fuel mixture is relatively uniform near the upstream end of the ceramic foam 21. As a result, the flame is less likely to flow back near the upstream end of the ceramic foam 21. That is, in terms of stable flame combustion, the ceramic foam 21 has the same effect as when the ceramic foam 21 does not have the voids 21S. On the other hand, since the ceramic foam 21 has the voids 21S, an increase in resistance to the air-fuel mixture flowing through the voids 21S can be suppressed.

[0022] (2) According to the above embodiment, the gaps 21S are open not only at the downstream end face but also at the upstream end face of the ceramic foam 21. Therefore, the air-fuel mixture flows smoothly through the gaps 21S from the upstream end to the downstream end of the ceramic foam 21.

[0023] (3) According to the above embodiment, a flame is maintained within the continuous pores of the ceramic foam 21, particularly near the downstream end of the ceramic foam 21. Therefore, combustion can be maintained within the cylindrical body 11 even with a lean fuel such as the reacted exhaust fuel gas discharged from a fuel cell.

[0024] <Example of change> This embodiment can be modified as follows: Furthermore, this embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0025] The shape of the cylindrical body 11 is not important. As long as there is a space inside through which the combustion gas can flow, any shape is acceptable. Furthermore, the cylindrical body 11 is not limited to a double structure of the outer cylinder 12 and the inner cylinder 17, and may be composed of a single cylindrical member.

[0026] In the above embodiment, the first supply port 13 as a fuel supply port and the second supply port 14 as an air supply port are provided, but both may be configured as one supply port. Even in this case, the cylindrical body 11 can be said to have an air supply port and a combustion gas exhaust port.

[0027] The fuel supply source 30 is not limited to a fuel cell. The fuel is not limited to hydrogen. Similarly, the air supply source 40 is not limited to a fuel cell. The shape of the voids 21S in the ceramic foam 21 is not limited to the example in the above embodiment. For example, the ceramic foam 121 shown in Fig. 3 has voids 121S. The voids 121S are frustum-shaped. The inner diameter of the voids 121S increases toward the downstream side. The central axis of the voids 121S coincides with the central axis CL of the outer cylinder 12, which is the central axis of the cylindrical body 11. In this way, the shape of the voids 21S in the ceramic foam 21 does not have to be a simple columnar shape, but may be any shape that extends along the central axis CL as a whole.

[0028] The voids 21S of the ceramic foam 21 do not necessarily have to be open at the upstream end face of the ceramic foam 21. In other words, the voids 21S of the ceramic foam 21 only need to be open at the downstream end face of the ceramic foam 21. When the voids 21S are open only at the downstream end face of the ceramic foam 21, it is preferable that the voids 21S extend over half or more of the dimension of the ceramic foam 21 in the direction along the central axis CL.

[0029] The central axis of the voids 21S in the ceramic foam 21 does not need to coincide with the central axis CL of the outer cylinder 12, which is the central axis of the cylindrical body 11. In addition, the central axis of the voids 21S in the ceramic foam 21 does not need to be parallel to the central axis CL of the outer cylinder 12. Even if the central axis of the voids 21S is not parallel to the central axis CL of the outer cylinder 12, it is sufficient that the voids 21S as a whole extend along the central axis CL.

[0030] The ceramic foam 21 may have a plurality of voids 21S. In this case, the voids 21S may all have the same shape or may have different shapes. Furthermore, the plurality of voids 21S may not be uniformly distributed throughout the ceramic foam 21. In other words, the plurality of voids 21S may be distributed unevenly in a particular portion of the ceramic foam 21. [Explanation of symbols]

[0031] 11...Cylinder body 13...First supply port 14...Second supply port 15...Exhaust port 20...Spark plug 21...Ceramic foam 21S...Gap CL...Central axis

Claims

[Claim 1] The present invention relates to a spark plug, and more particularly to a spark plug that is attached to a cylinder. The cylinder has a fuel supply port, an air supply port, and a combustion gas exhaust port, When the fuel supply port side is the upstream side and the fuel discharge port side is the downstream side, the ceramic foam is located inside the cylinder downstream of the fuel supply port and upstream of the ignition plug, The ceramic foam has voids extending along the central axis of the cylindrical body and opening at a downstream end face of the ceramic foam. Combustor.

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