Two-stage combustion device

Abstract

This can suppress the deterioration of combustion performance caused by the leakage of first-stage air. [Solution] The two-stage combustion device includes a fuel supply pipe (20) configured to supply first-stage fuel (F1) and second-stage fuel (F2), a hub (10), a straightening member (30) having a central hole through which the fuel supply pipe (20) passes and multiple straightening sections (32) that straighten first-stage air (A1), a cylindrical casing (40) that covers the outer surface of the fuel supply pipe (20) between the hub (10) and the straightening member (30) and is attached to the straightening member (30) to form a first-stage air flow path (61) for the first-stage air (A1) between the outer surface of the fuel supply pipe (20), an inner cylinder (90) that covers the outer surface of the casing (40), and an outer cylinder (91) that covers the outer surface of the inner cylinder (90) and forms a second-stage air flow path (62) for the second-stage air (A2) between the outer surface of the inner cylinder (90). The fuel supply pipe (20) has a first-stage fuel supply section (51) having first-stage injection holes (23) and a second-stage fuel supply section (52) having second-stage injection holes (24).

Description

[Technical Field]

[0001] The present invention relates to a two-stage combustion device. [Background technology]

[0002] In combustion devices such as industrial gas burners, a diffusion combustion system in which fuel and air are supplied separately is often adopted to prevent flashbacks, which are when a flame flows backward upstream of the fuel nozzle after combustion has stopped, and to prevent abnormal combustion such as blowout. However, in combustion devices using the diffusion combustion system, the combustion reaction occurs rapidly in an extremely narrow area where both fuel and air are supplied by diffusion, which tends to result in high peak flame temperatures. As a result, there is a tradeoff: a significant increase in nitrogen oxides (NOx), especially in combustion devices using hydrogen fuel, which has a fast combustion speed and high flame temperature.

[0003] Therefore, two-stage combustion devices have been developed that suppress the generation of NOx by using a two-stage combustion method (see, for example, Patent Document 1). 8 and 9 show the cross-sectional structure of a conventional two-stage combustion device.

[0004] As shown in Figures 8 and 9, the two-stage combustion device generates combustion in a furnace 100 and includes a hub 10, a fuel supply pipe 20, a flow straightening member 30, an inner cylinder 90, an outer cylinder 91, a connecting flange 93, and an ignition rod 80.

[0005] The fuel supply pipe 20 is disposed through the through-hole 11 of the hub 10 and is configured to supply first stage fuel F1 and second stage fuel F2 separately. The fuel supply pipe 20 has an inner pipe 21 and an outer pipe 22 that covers the outer peripheral surface of the inner pipe 21. The base end of the inner pipe 21 protrudes further to the base end side (to the right in FIGS. 8 and 9) than the base end surface of the hub 10.

[0006] The base end of the outer pipe 22 is located inside the hub 10. A flow path for the first-stage fuel F1 is formed between the inner peripheral surface of the outer pipe 22 and the outer peripheral surface of the inner pipe 21. A connection port 13 for introducing the first-stage fuel F1 into the flow path is opened on the outer peripheral surface of the hub 10.

[0007] A flow path (not shown) for second-stage fuel F2 is formed inside the inner pipe 21. A fuel pipe (not shown) is connected to the base end of the inner pipe 21. The flow straightening member 30 has a central hole 31 through which the fuel supply pipe 20 passes and a plurality of flow straightening portions 32 that straighten the first stage air A1. The flow straightening portions 32 are, for example, grooves formed on the outer peripheral surface of the flow straightening member 30.

[0008] The inner cylindrical body 90 covers the outer circumferential surfaces of the fuel supply pipe 20 and the flow straightening member 30 . The outer cylindrical body 91 covers the outer peripheral surface of the inner cylindrical body 90. The outer peripheral surface of the outer cylindrical body 91 is provided with a flange (not shown) that is fixed to the furnace 100.

[0009] The connecting flange 93 connects the base ends of the inner cylindrical body 90 and the outer cylindrical body 91 together over the entire circumference. A first-stage air flow path 161, which is a flow path for first-stage air A1, is formed between the inner peripheral surface of the inner cylinder 90 and the outer peripheral surface of the fuel supply pipe 20. A connection port 12 connected to the first-stage air flow path 161 is opened on the outer peripheral surface of the hub 10.

[0010] A second-stage air flow path 62, which is a flow path for second-stage air A2, is formed between the inner peripheral surface of the outer cylindrical body 91 and the outer peripheral surface of the inner cylindrical body 90. A connection port 92 connected to the second-stage air flow path 62 is opened on the outer peripheral surface of the outer cylindrical body 91.

[0011] First-stage injection holes 23 are opened in the outer peripheral surface of the fuel supply pipe 20 at a portion downstream of the straightening member 30, and inject first-stage fuel F1 toward the first-stage air A1 that has flowed through each straightening section 32.

[0012] At the tip of the fuel supply pipe 20, a second-stage injection hole 24 for injecting the second-stage fuel F2 is opened. The ignition rod 80 ignites the first-stage fuel F1 and extends along the fuel supply pipe 20. The ignition rod 80 is inserted into the insertion hole 19 that penetrates the hub 10 and the insertion hole 39 that penetrates the straightening member 30.

[0013] 8, FL1 is a flame resulting from the combustion of first-stage fuel F1 and first-stage air A1, and FL2 is a flame resulting from the combustion of second-stage fuel F2 and second-stage air A2. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Japanese Patent Application Publication No. 2023-494 Summary of the Invention [Problem to be solved by the invention]

[0015] In the two-stage combustion device, a gap is provided around the entire circumference between the flow straightening member 30 and the inner cylinder 90 so that the subassembly SA including the hub 10, fuel supply pipe 20, and flow straightening member 30 can be easily attached to and detached from the inner cylinder 90 during maintenance, etc. This gap is set relatively large in consideration of the deposition of oxides on the outer peripheral surface of the flow straightening member 30 and the inner peripheral surface of the inner cylinder 90, deformation of the flow straightening member 30 and the inner cylinder 90, etc.

[0016] However, as shown in Fig. 8, a portion of the first-stage air A1 leaks through the gap, making it difficult for the flow straightening section 32 to achieve the straightening effect on that portion of the first-stage air A1. As a result, there is room for improvement in terms of improving combustion performance.

[0017] Furthermore, since the ignition rod 80 has a ceramic outer cylinder, it is difficult to improve the machining precision of the outer cylinder. Also, because there is a large difference in the thermal expansion coefficient between the outer cylinder and the surrounding components, a relatively large gap is provided between the inner peripheral surface of the insertion hole 39 of the flow straightening member 30 and the outer peripheral surface of the ignition rod 80 to accommodate dimensional variations in the outer cylinder.

[0018] However, if a portion of the first stage air A1 leaks through the gap, it becomes difficult for the portion of the first stage air A1 to achieve the rectification effect of the rectification section 32. As a result, there is room for improvement in improving combustion performance. [Means for solving the problem]

[0019] Various aspects of a two-stage combustion system for solving the above problems will be described below. [Aspect 1] A two-stage combustion device, a fuel supply pipe configured to supply first stage fuel and second stage fuel; a hub supporting a base end of the fuel supply pipe; a straightening member having a central hole through which the fuel supply pipe passes and a plurality of straightening portions that straighten the first-stage air; a cylindrical casing that covers an outer peripheral surface of the fuel supply pipe between the hub and the straightening member and is attached to the straightening member to form a first-stage air flow path that is a flow path for the first-stage air between the outer peripheral surface of the fuel supply pipe and the straightening member; an inner cylindrical body covering an outer peripheral surface of the casing; an outer cylinder that covers an outer peripheral surface of the inner cylinder and forms a second-stage air flow path between the outer peripheral surface of the inner cylinder and the outer cylinder, the fuel supply pipe includes a first-stage fuel supply section having a first-stage injection hole that injects the first-stage fuel toward the first-stage air after flowing through each of the flow straightening sections, and a second-stage fuel supply section that is provided at a tip of the fuel supply pipe and has a second-stage injection hole that injects the second-stage fuel. Two-stage combustion device.

[0020] According to this configuration, the outer peripheral surface of the fuel supply pipe between the hub and the straightening member is covered by the casing, thereby forming a first-stage air flow path for the first-stage air between the inner peripheral surface of the casing and the outer peripheral surface of the fuel supply pipe. This allows almost all of the first-stage air to flow through the straightening portion of the straightening member. Therefore, deterioration of combustion performance due to leakage of the first-stage air can be suppressed.

[0021] Furthermore, with the above configuration, an insulating space is formed between the casing and the inner cylinder, through which air does not flow around the entire circumference. Therefore, when second-stage air preheated to several hundred degrees is supplied to the second-stage air passage, for example, the insulating space can prevent the heat of the inner cylinder heated by the high-temperature second-stage air from transferring to the first-stage air passage. This prevents the fuel supply pipe from becoming too hot, allowing the second-stage air to become even hotter.

[0022] Furthermore, with the above configuration, since the casing is attached to the flow straightening member, the subassembly including the hub, fuel supply pipe, flow straightening member, and casing can be attached and detached as a unit to and from the inner and outer cylinders, thereby protecting the flow straightening member and fuel supply pipe by the casing.

[0023] [Aspect 2] The tip of the casing covers the outer circumferential surface of the rectifying member. 2. The two-stage combustion apparatus of embodiment 1.

[0024] This configuration allows the tip end of the casing to be attached to the outer peripheral surface of the straightening member. This eliminates the need to attach the mounting portion of the casing to the base end surface of the straightening member, which prevents the casing from obstructing the flow of first-stage air in the first-stage air passage. This further contributes to improved combustion performance.

[0025] [Aspect 3] A male thread is formed on the outer circumferential surface of the flow rectifying member, An internal thread is formed on the inner peripheral surface of the tip of the casing to be threaded onto the external thread. 3. The two-stage combustion apparatus of embodiment 2.

[0026] According to this configuration, the casing can be easily attached to and detached from the rectifying member. [Aspect 4] a ring-shaped connecting flange that connects the base ends of the inner and outer cylindrical bodies together; A heat insulating structure is provided between the hub and the connecting flange to suppress heat transfer from the connecting flange to the hub.

[0023] A two-stage combustion apparatus according to any one of embodiments 1 to 3.

[0027] With this configuration, the transfer of heat from the connecting flange that connects the base ends of the inner and outer cylinders to the hub is suppressed by the insulating structure, thereby suppressing temperature rise in the hub and, ultimately, thermal damage to sensors and other devices placed near the hub.

[0028] [Aspect 5] an ignition rod extending along the fuel supply pipe and inserted through the insertion holes of the hub and the flow straightening member to ignite the first-stage fuel; a protective tube that covers an outer peripheral surface of the ignition rod between the hub and the rectifying member and is inserted into the insertion hole of the rectifying member,

[0023] A two-stage combustion apparatus according to any one of embodiments 1 to 4.

[0029] According to this configuration, the outer peripheral surface of the ignition rod is covered by the protective tube between the hub and the rectifier member. The tip of the protective tube is inserted into the insertion hole of the rectifier member. Unlike the outer tube of the ignition rod, the protective tube can be made of a metal material, i.e., the same material as the rectifier member, thereby improving the processing precision of the protective tube. Unlike the outer tube of the ignition rod, the protective tube does not need to consider the thermal expansion difference between the protective tube and the rectifier member. Therefore, it is not necessary to set a gap between the protective tube and the rectifier member that takes into account the processing precision or the thermal expansion difference, and the gap can be reduced. This prevents the first-stage air from flowing into the insertion hole, so that almost all of the first-stage air flows into the rectifying portion of the rectifier member. This contributes to improved combustion performance.

[0030] Furthermore, with the above-described configuration, when the ignition rod is attached to or detached from the hub and the rectifier member, the movement of the ignition rod is guided by the inner peripheral surface of the protective tube, which contributes to improving the ease of maintenance of the ignition rod.

[0031] [Aspect 6] A two-stage combustion device, a fuel supply pipe configured to supply first stage fuel and second stage fuel; a hub supporting a base end of the fuel supply pipe; a straightening member having a central hole through which the fuel supply pipe passes and a plurality of straightening portions that straighten the first-stage air; an inner cylindrical body provided on the outer circumferential side of the flow straightening member; an outer cylinder that covers an outer peripheral surface of the inner cylinder and forms a second-stage air flow path between the outer peripheral surface of the inner cylinder and the outer cylinder; an ignition rod extending along the fuel supply pipe and inserted through the insertion holes of the hub and the flow straightening member to ignite the first-stage fuel; a protective tube that covers an outer peripheral surface of the ignition rod between the hub and the rectifying member and is inserted into the insertion hole of the rectifying member, the fuel supply pipe includes a first-stage fuel supply section having a first-stage injection hole that injects the first-stage fuel toward the first-stage air after flowing through each of the flow straightening sections, and a second-stage fuel supply section that is provided at a tip of the fuel supply pipe and has a second-stage injection hole that injects the second-stage fuel. Two-stage combustion device.

[0032] According to this configuration, the outer peripheral surface of the ignition rod is covered by a protective tube between the hub and the rectifying member. The tip of the protective tube is inserted into the insertion hole of the rectifying member. This prevents the first-stage air from flowing into the insertion hole of the rectifying member, so that almost all of the first-stage air flows through the rectifying portion of the rectifying member. This prevents a decrease in combustion performance due to leakage of the first-stage air.

[0033] Furthermore, with the above-described configuration, when the ignition rod is attached to or detached from the hub and the rectifier member, the movement of the ignition rod is guided by the inner peripheral surface of the protective tube, which contributes to improving the ease of maintenance of the ignition rod. [Effects of the Invention]

[0034] According to the present invention, it is possible to suppress a decrease in combustion performance caused by leakage of first-stage air. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 is a cross-sectional view of a two-stage combustion device according to one embodiment. [Figure 2] 2 is a cross-sectional view of the connecting flange of FIG. 1 and a subassembly removed from the connecting flange. [Figure 3] FIG. 3 is a cross-sectional view of the subassembly and the ignition rod removed from the subassembly. [Figure 4] FIG. 4 is a cross-sectional view of a two-stage combustion device with preheated second-stage air being introduced into the second-stage air flow path. [Figure 5] FIG. 5 is a cross-sectional view of a first variant of the subassembly. [Figure 6] FIG. 6 is a cross-sectional view of a second variant of the subassembly. [Figure 7] FIG. 7 is a cross-sectional view of a third variant of the subassembly. [Figure 8] FIG. 8 is a cross-sectional view of a conventional two-stage combustion device. [Figure 9] 9 is a cross-sectional view of the connecting flange of FIG. 8 and a subassembly removed from the connecting flange. DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, one embodiment of a two-stage combustion device will be described with reference to FIGS. As shown in FIG. 1, the two-stage combustion device generates combustion in a furnace 100 and includes a hub 10, a fuel supply pipe 20, a flow straightening member 30, a casing 40, a spacer 70, an ignition rod 80, a protective pipe 81, an inner cylinder 90, an outer cylinder 91, and a connecting flange 93.

[0037] In the following description, the base end side (right side in FIG. 1) and the tip end side (left side in FIG. 1) of the two-stage combustion device will be simply referred to as the base end side and the tip end side, respectively. <Hub 10> 3, the hub 10 is columnar. The hub 10 has a through-hole 11. The through-hole 11 is provided on the central axis of the hub 10.

[0038] The hub 10 is provided with an insertion hole 19 that passes through the hub 10 along the axial direction of the hub 10 . As shown in FIG. 1, a connection port 12 and a connection port 13 are opened on the outer peripheral surface of the hub 10.

[0039] The hub 10 is made of metal, and in this embodiment, the hub 10 is made of stainless steel. <Fuel supply pipe 20> 3, the fuel supply pipe 20 is disposed to pass through the through-hole 11 and is configured to supply first-stage fuel F1 and second-stage fuel F2 separately. A base end of the fuel supply pipe 20 is supported by the hub 10.

[0040] As shown in FIGS. 1 and 3, the fuel supply pipe 20 has a first-stage fuel supply portion 51 and a second-stage fuel supply portion 52. As shown in FIG. 1, the first-stage fuel supply section 51 has first-stage injection holes 23 that inject first-stage fuel F1 toward the first-stage air A1 that has flowed through each of the flow straightening sections 32.

[0041] The second-stage fuel supply section 52 is provided at the tip of the fuel supply pipe 20 and has second-stage injection holes 24 that inject the second-stage fuel F2. The fuel supply pipe 20 of this embodiment has an inner pipe 21 and an outer pipe 22 that covers the outer peripheral surface of the inner pipe 21 .

[0042] The base end of the inner tube 21 protrudes further to the base end side than the base end surface of the hub 10 . The base end of the outer pipe 22 is located inside the hub 10. Between the inner peripheral surface of the outer pipe 22 and the outer peripheral surface of the inner pipe 21, a flow path (not shown) for the first stage fuel F1 is formed.

[0043] The connection port 13 of the hub 10 is connected to the flow path. A fuel pipe (not shown) is connected to the connection port 13. The first stage fuel F1 is introduced into the flow path through the fuel pipe and the connection port 13.

[0044] A flow path (not shown) for second-stage fuel F2 is formed inside the inner pipe 21. A fuel pipe (not shown) is connected to the base end of the inner pipe 21. The second-stage fuel F2 is introduced into the inner pipe 21 through the fuel pipe and an opening on the base end side of the inner pipe 21.

[0045] 1 and 3, first-stage injection holes 23 that inject first-stage fuel F1 toward the first-stage air A1 that has flowed through each of the flow straightening sections 32 are opened in a portion of the outer circumferential surface of the fuel supply pipe 20 that is downstream of the flow straightening member 30. A plurality of first-stage injection holes 23 are provided at intervals from one another in the circumferential direction of the fuel supply pipe 20.

[0046] Second-stage injection holes 24 that inject second-stage fuel F2 are opened at the tip of the fuel supply pipe 20. A plurality of second-stage injection holes 24 are provided at intervals from one another in the circumferential direction of the fuel supply pipe 20 around the central axis of the fuel supply pipe 20.

[0047] The fuel supply pipe 20 is made of metal. In this embodiment, the fuel supply pipe 20 is made of stainless steel. <Flow straightening member 30> 3, the flow straightening member 30 of this embodiment is disk-shaped. The flow straightening member 30 has a central hole 31 through which the fuel supply pipe 20 passes. The central hole 31 is provided on the same axis as the through-hole 11 of the hub 10.

[0048] 1, the rectifying member 30 has a plurality of rectifying portions 32 that rectify the first-stage air A1. In this embodiment, the rectifying portions 32 are grooves formed on the outer peripheral surface of the rectifying member 30. The rectifying portions 32 extend in a spiral shape around the central axis of the rectifying member 30.

[0049] 3, the rectifying member 30 is provided with an insertion hole 39 that penetrates the rectifying member 30 along the axial direction of the rectifying member 30. The insertion hole 39 is provided on the same axis as the insertion hole 19 of the hub 10.

[0050] In this embodiment, a male thread (not shown) is formed on the outer peripheral surface of the flow rectifying member 30. The male thread is formed on the outer peripheral surface of the tip end portion of the flow rectifying member 30. The flow rectifying member 30 is made of metal. In this embodiment, the flow rectifying member 30 is made of stainless steel.

[0051] <Casing 40> As shown in FIGS. 1 to 3, casing 40 is cylindrical, covers the outer peripheral surface of fuel supply pipe 20 between hub 10 and rectifying member 30, and is attached to rectifying member 30. Casing 40 forms a first-stage air flow path 61, which is a flow path for first-stage air A1, between the outer peripheral surface of fuel supply pipe 20 and casing 40. The first-stage air flow path 61 is connected to connection port 12 of hub 10 described above. First-stage air A1 is introduced into first-stage air flow path 61 through connection port 12.

[0052] The base end of the casing 40 abuts against the tip surface of the hub 10 . The tip of the casing 40 covers the outer peripheral surface of the flow rectifying member 30. The inner peripheral surface of the tip of the casing 40 is formed with a female thread (not shown) that screws onto the male thread of the flow rectifying member 30.

[0053] The casing 40 of this embodiment is made of metal, specifically stainless steel. <Ignition rod 80 and protective tube 81> As shown in FIGS. 1 to 3, the ignition rod 80 ignites the first stage fuel F1.

[0054] The ignition rod 80 extends along the fuel supply pipe 20 and is inserted through both the insertion hole 19 of the hub 10 and the insertion hole 39 of the flow straightening member 30. The ignition rod 80 is inserted from the base end side of the hub 10, in this order, through the insertion hole 19 of the hub 10 and the insertion hole 39 of the flow straightening member 30. The ignition rod 80 has a well-known configuration.

[0055] The protective tube 81 covers the outer peripheral surface of the ignition rod 80 between the hub 10 and the rectifier member 30. The base end of the protective tube 81 is inserted into the insertion hole 19 of the hub 10. The tip end of the protective tube 81 is inserted into the insertion hole 39 of the rectifier member 30.

[0056] The protective tube 81 is made of metal. In this embodiment, the protective tube 81 is made of stainless steel. <Inner cylindrical body 90, outer cylindrical body 91, and connecting flange 93> As shown in FIGS. 1 and 2, the inner cylindrical body 90 covers the outer peripheral surface of the casing 40.

[0057] The outer cylindrical body 91 covers the outer peripheral surface of the inner cylindrical body 90. The outer peripheral surface of the outer cylindrical body 91 is provided with a flange (not shown) that is fixed to the furnace 100. 1, a second-stage air flow path 62, which is a flow path for second-stage air A2, is formed between the inner peripheral surface of the outer cylindrical body 91 and the outer peripheral surface of the inner cylindrical body 90. The outer cylindrical body 91 is provided with a connection port 92 connected to the second-stage air flow path 62.

[0058] The connecting flange 93 is annular, and connects the base ends of the inner cylindrical body 90 and the outer cylindrical body 91 together over the entire circumference. <Spacer 70> 1 to 3, the spacer 70 is annular and is provided between the hub 10 and the connecting flange 93. The spacer 70 covers the outer peripheral surface of the casing 40. An air layer is formed between the inner peripheral surface of the spacer 70 and the outer peripheral surface of the casing 40.

[0059] The spacer 70 of this embodiment is formed from a material with lower thermal conductivity than the connecting flange 93. The spacer 70 is preferably made of, for example, ceramic. The spacer 70 of this embodiment functions as a heat insulating structure that suppresses heat transfer from the connecting flange 93 to the hub 10. The spacer 70 is fixed to the tip surface of the hub 10.

[0060] 7, FL1 is a flame resulting from the combustion of first-stage fuel F1 and first-stage air A1, and FL2 is a flame resulting from the combustion of second-stage fuel F2 and second-stage air A2. <Operation of this embodiment> 1, the outer peripheral surface of the fuel supply pipe 20 is covered by the casing 40 between the hub 10 and the rectifying member 30, and a first-stage air flow path 61, which is a flow path for the first-stage air A1, is formed between the inner peripheral surface of the casing 40 and the outer peripheral surface of the fuel supply pipe 20. As a result, substantially all of the first-stage air A1 flows through the rectifying portion 32 of the rectifying member 30. Therefore, a decrease in combustion performance due to leakage of the first-stage air A1 can be suppressed (the above is the effect).

[0061] <Effects of this embodiment> (1) Because of the above-mentioned effects, it is possible to suppress the deterioration of combustion performance caused by the leakage of the first stage air A1.

[0062] (2) As shown in Fig. 4, an insulating space S in which no air flows is formed around the entire circumference between the casing 40 and the inner cylinder 90. For this reason, when second-stage air A2 preheated to several hundred degrees is supplied to the second-stage air flow path 62, for example, the insulating space S can prevent the heat of the inner cylinder 90 heated by the high-temperature second-stage air A2 from transferring to the first-stage air flow path 61. This prevents the fuel supply pipe 20 from becoming too hot, allowing the second-stage air A2 to become even hotter.

[0063] (3) As shown in Fig. 2, the casing 40 is attached to the flow straightening member 30, so that the subassembly SA including the hub 10, fuel supply pipe 20, flow straightening member 30, and casing 40 can be attached and detached as a unit to the inner cylinder 90 and the outer cylinder 91. This allows the flow straightening member 30 and the fuel supply pipe 20 to be protected by the casing 40.

[0064] (4) The tip end of the casing 40 covers the outer peripheral surface of the rectifying member 30. This makes it possible to attach the tip end of the casing 40 to the outer peripheral surface of the rectifying member 30. This eliminates the need to attach the attachment portion of the casing 40 to the base end surface of the rectifying member 30, making it possible to prevent the flow of the first-stage air A1 in the first-stage air flow path 61 from being obstructed by the casing 40. This further contributes to improving combustion performance.

[0065] (5) A male thread is formed on the outer peripheral surface of the flow rectifying member 30. A female thread that screws into the male thread is formed on the inner peripheral surface of the tip of the casing 40. This allows the casing 40 to be easily attached to and detached from the flow rectifying member 30.

[0066] (6) An annular connecting flange 93 is provided to connect the base ends of the inner cylindrical body 90 and the outer cylindrical body 91. A spacer 70 is provided between the hub 10 and the connecting flange 93 to suppress the transfer of heat from the connecting flange 93 to the hub 10. As a result, the transfer of heat from the connecting flange 93 to the hub 10 is suppressed by the spacer 70, which suppresses a temperature rise in the hub 10 and, in turn, thermal damage to sensors and the like disposed near the hub 10.

[0067] (7) The two-stage combustion device includes an ignition rod 80 that ignites the first-stage fuel F1, and a protective tube 81 that covers the outer surface of the ignition rod 80 between the hub 10 and the straightening member 30 and is inserted into the insertion hole 39 of the straightening member 30.

[0068] With this configuration, the outer circumferential surface of the ignition rod 80 is covered by the protective tube 81 between the hub 10 and the rectifying member 30. The tip of the protective tube 81 is inserted into the insertion hole 39 of the rectifying member 30. Unlike the outer tube of the ignition rod 80, the protective tube 81 can be made of a metal material, i.e., the same material as the rectifying member 30, thereby improving the processing precision of the protective tube 81. Unlike the outer tube of the ignition rod 80, the protective tube 81 does not need to consider the thermal expansion difference between the protective tube 81 and the rectifying member 30. For these reasons, it is not necessary to set a gap between the protective tube 81 and the rectifying member 30 that takes into account the processing precision and the thermal expansion difference, and therefore the gap can be made small. This prevents the first-stage air A1 from flowing into the insertion hole 39 of the rectifying member 30, so that substantially all of the first-stage air A1 flows through the rectifying portion 32 of the rectifying member 30. This prevents a decrease in combustion performance due to leakage of the first-stage air A1.

[0069] Furthermore, with the above configuration, when the ignition rod 80 is attached to or detached from the hub 10 and the rectifier member 30, the movement of the ignition rod 80 is guided by the inner peripheral surface of the protective tube 81. This contributes to improving the maintainability of the ignition rod 80.

[0070] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0071] As in the first modified example of the subassembly SA shown in Fig. 5, the rectifying portion 32 may be a hole penetrating the rectifying member 30. Note that in Fig. 5, the same reference numerals are used to designate the same or corresponding components as those in the above embodiment, and redundant explanations will be omitted. Also, in Fig. 5, the ignition rod 80 and the protective tube 81 are not shown.

[0072] The protective pipe 81 may be omitted. Even in this case, as long as the two-stage combustion device includes the casing 40, the same effects as the above effects (1) to (6) can be achieved. As in a second modified example of the subassembly SA shown in Fig. 6, the tip of the casing 40 may not cover the outer peripheral surface of the rectifying member 30. In this case, an attachment portion 41 that protrudes inward is provided at the tip of the casing 40. The attachment portion 41 is fastened to the base end surface of the rectifying member 30 via a screw 42, thereby attaching the casing 40 to the rectifying member 30. Note that in Fig. 6, components that are the same as or correspond to those in the above embodiment are denoted by the same reference numerals as in the above embodiment, and redundant description will be omitted. Also, the ignition rod 80 and the protective tube 81 are not shown in Fig. 6.

[0073] The spacer 70 may be fixed to the connecting flange 93 . In the above embodiment, an air layer is provided between the inner circumferential surface of the spacer 70 and the outer circumferential surface of the casing 40, but such an air layer may not be provided.

[0074] The heat insulating structure may be omitted. For example, the spacer 70 may be made of the same material as the connecting flange 93. Alternatively, the spacer 70 may be omitted and the connecting flange 93 and the hub 10 may be brought into contact with each other.

[0075] As in a third modified example of the subassembly SA shown in FIG. 7 , the fuel supply pipe 120 may not include the inner pipe 21 and the outer pipe 22. In this case, the fuel supply pipe 120 is formed from a single pipe. The through-hole 111 of the hub 110 has a reduced-diameter portion 114 that opens at the base end surface of the hub 110 and an expanded-diameter portion 115 that opens at the tip end surface of the hub 110 and has a larger diameter than the reduced-diameter portion 114. The base end of the fuel supply pipe 120 is inserted into the expanded-diameter portion 115. In other words, the base end of the fuel supply pipe 120 is supported by the hub 110. A common passage 125 is provided inside the fuel supply pipe 120. The common passage 125 extends along the axial direction of the fuel supply pipe 120. The base end of the common passage 125 communicates with the reduced-diameter portion 114 of the through-hole 111.

[0076] A first-stage injection hole 123 is connected to the tip of the common passage 125. The first-stage injection hole 123 extends from the tip of the common passage 125 radially outward of the fuel supply pipe 120 and opens to the outer circumferential surface of the fuel supply pipe 120.

[0077] A second-stage injection hole 124 is connected to the tip of the common passage 125. The inner diameter of the second-stage injection hole 124 is preferably smaller than the inner diameter of the common passage 125. In FIG. 7, the same or corresponding components as those in the above embodiment are denoted by the same reference numerals as those in the above embodiment, and redundant explanations will be omitted.

[0078] The casing 40 may be omitted from the two-stage combustion device. Even in this case, as long as the two-stage combustion device is provided with the protective tube 81, an effect equivalent to the above effect (7) can be achieved. [Explanation of symbols]

[0079] 10,110…hub 11,111...Through holes 12...Connection port 13...Connection port 19...Through hole 20,120…Fuel supply pipe 21…Inner pipe 22…Outer tube 23,123…1st stage injection hole 24,124…Second stage injection hole 30...flow straightening member 31...Center hole 32... Rectifier section 39...Through hole 40...Casing 41...Mounting part 42...Screw 51...First stage fuel supply section 52...Second stage fuel supply section 61,161...First stage air flow path 62...Second stage air flow path 70...Spacer 80...Ignition rod 81...Protection tube 90...Inner cylinder 91...Outer cylinder 92...Connection port 93...Connecting flange 100...Furnace 114...Reduced diameter part 115...Expanded diameter part 125…Common passage A1...first stage air A2...Second stage air F1…1st stage fuel F2…Second stage fuel S...insulated space SA…Subassembly

Claims

1. A two-stage combustion device, a fuel supply pipe configured to supply first stage fuel and second stage fuel; a hub supporting a base end of the fuel supply pipe; a straightening member having a central hole through which the fuel supply pipe passes and a plurality of straightening portions that straighten the first-stage air; a cylindrical casing that covers an outer peripheral surface of the fuel supply pipe between the hub and the straightening member and is attached to the straightening member to form a first-stage air flow path that is a flow path for the first-stage air between the outer peripheral surface of the fuel supply pipe and the straightening member; an inner cylindrical body covering an outer peripheral surface of the casing; an outer cylinder that covers an outer peripheral surface of the inner cylinder and forms a second-stage air flow path between the outer peripheral surface of the inner cylinder and the outer cylinder, the fuel supply pipe includes a first-stage fuel supply section having a first-stage injection hole that injects the first-stage fuel toward the first-stage air after flowing through each of the flow straightening sections, and a second-stage fuel supply section that is provided at a tip of the fuel supply pipe and has a second-stage injection hole that injects the second-stage fuel. Two-stage combustion device.

2. The tip of the casing covers the outer circumferential surface of the rectifying member. The two-stage combustion system of claim 1 .

3. A male thread is formed on the outer circumferential surface of the flow rectifying member, An internal thread is formed on the inner peripheral surface of the tip of the casing to be threaded onto the external thread.

3. The two-stage combustion system of claim 2.

4. a ring-shaped connecting flange that connects the base ends of the inner and outer cylindrical bodies together; A heat insulating structure is provided between the hub and the connecting flange to suppress heat transfer from the connecting flange to the hub. The two-stage combustion apparatus according to any one of claims 1 to 3.

5. an ignition rod extending along the fuel supply pipe and inserted through the insertion holes of the hub and the flow straightening member to ignite the first-stage fuel; a protective tube that covers an outer peripheral surface of the ignition rod between the hub and the rectifying member and is inserted into the insertion hole of the rectifying member, The two-stage combustion system of claim 1 .

6. A two-stage combustion device, a fuel supply pipe configured to supply first stage fuel and second stage fuel; a hub supporting a base end of the fuel supply pipe; a straightening member having a central hole through which the fuel supply pipe passes and a plurality of straightening portions that straighten the first-stage air; an inner cylindrical body provided on the outer circumferential side of the flow straightening member; an outer cylinder that covers an outer peripheral surface of the inner cylinder and forms a second-stage air flow path between the outer peripheral surface of the inner cylinder and the outer cylinder; an ignition rod extending along the fuel supply pipe and inserted through the insertion holes of the hub and the flow straightening member to ignite the first-stage fuel; a protective tube that covers an outer peripheral surface of the ignition rod between the hub and the rectifying member and is inserted into the insertion hole of the rectifying member, the fuel supply pipe includes a first-stage fuel supply section having a first-stage injection hole that injects the first-stage fuel toward the first-stage air after flowing through each of the flow straightening sections, and a second-stage fuel supply section that is provided at a tip of the fuel supply pipe and has a second-stage injection hole that injects the second-stage fuel. Two-stage combustion device.

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