COMBUSTOR AND COMBUSTOR ARRAY

Abstract

A combustor includes a distal end portion which forms a nozzle extending along an axis and opening at a distal end; an intermediate portion having a mixing surface which defines a mixing space in which air and fuel are mixed, by gradually expanding to an outer side in a radial direction of the axis from the nozzle to a rear, behind the distal end portion; a proximal end portion which forms a fuel space to which fuel is supplied from outside, behind the intermediate portion; and a plurality of air introduction pipes which penetrate the proximal end portion in a direction of the axis, have a distal end communicating with the mixing space, are arranged in a circumferential direction of the axis to surround the axis, and have a fuel supply hole formed on an inner side in a radial direction of the axis to communicate with the fuel space.

Claims

1. A combustor comprising: a distal end portion which forms a nozzle extending along an axis and opening at a distal end; an intermediate portion having a mixing surface which defines a mixing space in which air and fuel are mixed, by gradually expanding to an outer side in a radial direction of the axis from the nozzle to a rear, behind the distal end portion; a proximal end portion which forms a fuel space to which fuel is supplied from outside, behind the intermediate portion; and a plurality of air introduction pipes which penetrate the proximal end portion in a direction of the axis, have a distal end communicating with the mixing space, are arranged in a circumferential direction of the axis to surround the axis, and have a fuel supply hole formed on each inner side in a radial direction of the axis to communicate with the fuel space.

2. The combustor according to claim 1, wherein the mixing surface is curved to be convex to the outer side in the radial direction of the axis in a cross-sectional view including the axis.

3. The combustor according to claim 1, wherein the nozzle extends, while being eccentric in the radial direction with respect to the axis from the distal end side to the rear.

4. The combustor according to claim 1, wherein the air introduction pipe extends, while being eccentric in the radial direction with respect to an auxiliary axis extending parallel to the axis from the intermediate portion side to the rear.

5. The combustor according to claim 1, wherein the air introduction pipe is twisted to be directed from one side in the circumferential direction of the axis toward the other side, from the intermediate portion side to the rear.

6. The combustor according to claim 1, wherein a lightening part as a hollow part is formed in a portion closer to an outer peripheral side than the nozzle at the distal end portion.

7. The combustor according to claim 1, further comprising: a protruding part provided on a front side of the proximal end portion and protruding into the mixing space along the axis, the fuel supply hole being formed on an outer peripheral surface of the protruding part.

8. A combustor comprising: a distal end portion which forms a nozzle extending along an axis and opening at a distal end; an intermediate portion which forms a mixing space expanding from the nozzle in a direction intersecting the axis behind the distal end portion; a proximal end portion which forms a fuel space to which fuel is supplied from outside behind the intermediate portion; and a plurality of air introduction pipes which penetrate the proximal end portion in a direction of the axis, have a distal end communicating with the mixing space, and are arranged in a circumferential direction of the axis to surround the axis, wherein a fuel supply hole through which the fuel space and the mixing space communicate with each other is formed on a surface facing the distal end side of a portion surrounded by the plurality of air introduction pipes in the proximal end portion, and an extension cylinder part, which extends in the direction of the axis to cover the fuel supply hole from an outer peripheral side and has an air hole formed to communicate with the mixing space, is provided on the surface facing the distal end side.

9. A combustor array comprising: a plurality of combustors according to claim 1, wherein the plurality of combustors are arranged in the plural in a plane orthogonal to the axis.

10. The combustor array according to of claim 9, wherein the plurality of combustors are arranged in a grid shape at equal intervals in the plane orthogonal to the axis.

11. The combustor array according to of claim 9, wherein each of the plurality of combustors has a hexagonal shape when viewed from the direction of the axis, and is arranged in a honeycomb shape by contacting of end faces thereof.

12. The combustor array according to of claim 9, wherein the plurality of combustors are arranged in an annular shape.

13. The combustor array according to of claim 9, wherein the plurality of combustors are arranged in a staggered manner so that positions of the axis differ from each other in the plane orthogonal to the axis.

14. The combustor array according to of claim 9, wherein the plurality of combustors are arranged along a curved concave surface which is convex from one to the other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 is a plan view showing a configuration of a combustor array according to a first embodiment of the present invention.

[0036] FIG. 2 is a cross-sectional view showing the configuration of the combustor according to the first embodiment of the present invention.

[0037] FIG. 3 is a cross-sectional view showing a configuration of a combustor according to a second embodiment of the present invention.

[0038] FIG. 4 is a cross-sectional view showing a configuration of a combustor according to a third embodiment of the present invention.

[0039] FIG. 5 is a cross-sectional view showing a configuration of a combustor according to a fourth embodiment of the present invention.

[0040] FIG. 6 is a plan view showing the configuration of the combustor according to the fourth embodiment of the present invention.

[0041] FIG. 7 is a cross-sectional view showing a configuration of a combustor according to a fifth embodiment of the present invention.

[0042] FIG. 8 is a cross-sectional view showing a configuration of a combustor according to a sixth embodiment of the present invention.

[0043] FIG. 9 is a cross-sectional view showing a configuration of a combustor according to a seventh embodiment of the present invention.

[0044] FIG. 10 is a plan view showing a first modified example of a combustor array according to an embodiment of the present invention.

[0045] FIG. 11 is a plan view showing a second modified example of the combustor array according to an embodiment of the present invention.

[0046] FIG. 12 is a plan view showing a third modified example of the combustor array according to the embodiment of the present invention.

[0047] FIG. 13 is a plan view showing a fourth modified example of the combustor array according to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

[0048] A first embodiment of the present invention will be described with reference to FIGS. 1 and 2. A combustor array 100 according to the present embodiment is equipped with a plurality of combustors 1. Each combustor 1 is a small device that forms a small-size flame. That is, the combustor array 100 is configured as a so-called micro flame combustor.

[0049] More specifically, as shown in FIG. 1, the combustor array 100 is equipped with a plurality of (9) combustors 1 arranged in a grid shape in a plane orthogonal to an axis O that is a central axis of the combustor 1. When viewed from a direction of the axis O, the combustor 1 has a rectangular (square) cross-sectional shape. Outer surfaces of a pair of adjacent combustors 1 about each other without a gap.

[0050] Next, the configuration of the combustor 1 will be described with reference to FIG. 2. FIG. 1 is a cross-sectional view taken along a line A-A of FIG. 2. As shown in FIG. 2, the combustor 1 is equipped with a distal end portion 31, an intermediate portion 32, a proximal end portion 33, and an air introduction pipe 12.

[0051] A nozzle 11 which extends along the axis O and has a distal end 11T opening outward is formed in the distal end portion 31. As shown in FIG. 1, the nozzle 11 has a circular cross-sectional shape centered on the axis O.

[0052] The intermediate portion 32 is integrally provided on a side opposite to the distal end 11T of the distal end portion 31 in a direction of the axis O (a rear end 11R). In the following description, a side at which the distal end 11T is located when viewed from the rear end 11R in the direction of the axis O is called a front and a front side, and an opposite side thereto is called a rear and a rear side. A mixing space 32V communicating with the nozzle 11 is formed inside the intermediate portion 32. The mixing space 32V expands in a direction (a radial direction) intersecting the axis O. More specifically, the mixing space 32V is defined by a conical mixing surface S1 that has a diameter gradually expanding outward in the radial direction from a rear end 11R of the nozzle 11 to the rear along the axis O, and a cylindrical surface S2 extending in a cylindrical shape from an end edge on a rear side of the mixing surface S1 along the axis O. That is, the mixing space 32V is gradually reduced in diameter from the rear side toward the nozzle 11.

[0053] The proximal end portion 33 is integrally provided on the side to the rear of the intermediate portion 32. A fuel space 33V as a hollow part is formed inside the proximal end portion 33. Fuel supplied from the outside is stored in the fuel space 33V. A surface facing the front side of the proximal end portion 33 is configured by an annular surface S3 connected to the cylindrical surface S2 of the mixing space 32V and a central surface S4 located on the inner peripheral side of the annular surface S3. The annular surface S3 and the central surface S4 expand at the same position in the direction of the axis O. Further, both the annular surface S3 and the central surface S4 expand in a direction orthogonal to the axis O.

[0054] The air introduction pipe 12 is a flow path that penetrates the proximal end portion 33 in the direction of the axis O. Air supplied from the outside is guided into the aforementioned mixing space 32V through the air introduction pipe 12. A plurality (four) of air introduction pipes 12 are provided to surround the axis O at intervals in the circumferential direction. Each air introduction pipe 12 extends along an auxiliary axis O2 that extends parallel to the axis O. An inner diameter of the air introduction pipe 12 is constant over the entire region in the direction of the auxiliary axis O2. End portions on a front side of each air introduction pipe 12 communicate with the above-described mixing space 32V. End portions on the rear side of each air introduction pipe 12 communicate with an air supply source (not shown).

[0055] Each one fuel supply hole 40 is formed on the introduction pipe inner side surface 12A, which is a portion on an inner side in the radial direction of the axis O, in the inner peripheral surfaces of the plurality of air introduction pipes 12. The introduction pipe inner side surface 12A is a region facing the axis O side when the air introduction pipe 12 is viewed from the direction of the axis O. In the inner peripheral surface of the air introduction pipe 12, a region except the introduction pipe inner side face 12A (that is, a region facing a side opposite to the axis O) is an introduction pipe outer side surface 12B. Each fuel supply hole 40 communicates with the fuel space 33V and the space inside the air introduction pipe 12. The fuel stored in the fuel space 33V is guided into the air introduction pipe 12 through the fuel supply hole 40.

[0056] Next, the operation of the above-described combustor 1 will be described. When operating the combustor 1, fuel and air are supplied to the combustor 1, respectively. Air flows from the rear toward the front through the plurality of air introduction pipes 12. Fuel is supplied (sprayed) into the air flow from the fuel space 33V through the aforementioned fuel supply hole 40. The fuel flows from the rear toward the front along the introduction pipe inner side surface 12A in the air introduction pipe 12. Thereafter, the fuel and air are mixed in the mixing space 32V to form a premixed gas. At this time, a region having a relatively high fuel concentration (a high concentration region X) is formed to cover the introduction pipe inner side surface 12A and the central surface S4 from the outside. The premixed gas is guided by the mixing surface S1 of the mixing space 32V to contract toward the inner side in the radial direction of the axis O. The contracted premixed gas is guided to the outside through the nozzle 11. By igniting the premixed gas with an ignition device (not shown), a premixed flame extending forward from the nozzle 11 is formed. When such a phenomenon occurs simultaneously in each combustor 1, the combustor array 100 operates as a micro flame combustor that forms a plurality of small-scale flames.

[0057] As described above, according to the aforementioned configuration, the air guided into the mixing space 32V through the air introduction pipe 12 is mixed with fuel in the mixing space 32V to form a premixed gas. By igniting the premixed gas, a flame is formed on a downstream side from the nozzle 11 of the distal end portion 31. Here, the fuel supply holes 40 are formed in each of the portions on the inner side in the radial direction of the plurality of air introduction pipes 12, that is, portions close to the axis O (the introduction pipe inner side surface 12A). Accordingly, in the mixing space 32V, as the portion is closer to the axis O, the fuel concentration becomes higher (a high concentration region X is formed). Further, since the nozzle 11 extends around the axis O, the fuel concentration is highest in a region through which the axis O passes, in a flame region formed on the downstream side of the nozzle 11. In other words, the fuel concentration is relatively low in the inner peripheral surface of the nozzle 11, the inner surface of the mixing space 32V, and ae region along the surface on an outer side in the radial direction (the introduction pipe outer side surface 12B) of each air introduction pipe 12. As a result, it is possible to reduce a likelihood that flashback occurs along the surfaces. Therefore, the combustor 1 and the combustor array 100 can be operated more stably.

[0058] Furthermore, according to the aforementioned configuration, the mixing surface S1 gradually expands to the outer side in the radial direction from the nozzle 11 toward the rear. In other words, the mixing surface S1 is gradually reduced in diameter toward the nozzle 11 from the outer side to the inner side in the radial direction. Therefore, for example, as compared with a configuration in which the mixing surface S1 expands in the radial direction of the axis O, the fuel and air can be gradually contracted and directed toward the nozzle, while promoting the mixing of the fuel and air. As a result, the pressure loss in the mixing space 32V can be reduced. Therefore, the combustor 1 and the combustor array 100 can be operated more stably.

[0059] In addition, according to the aforementioned configuration, by arranging a plurality of combustors 1 in which the likelihood of occurrence of flashback is reduced, it is possible to provide a combustor array 100 that has a high output and can be more stably operated. In particular, according to the aforementioned configuration, the plurality of combustors 1 are arranged in a grid shape in a plane orthogonal to the axis O. Therefore, the distribution of the flame in the plane orthogonal to the axis O is made uniform, and a more stable flame can be obtained.

[0060] The first embodiment of the present invention has been described above. Further, various changes and modifications can be made to the aforementioned configuration without departing from the gist of the present invention.

Second Embodiment

[0061] Next, a second embodiment of the present invention will be described with reference to FIG. 3. In addition, components similar to those of the first embodiment are denoted by the same reference numerals, and repeated description will not be provided. As shown in FIG. 3, in a combustor 1 according to the present embodiment, a shape of a mixing surface S1b is different from that of the first embodiment. The mixing surface S1b has a curved surface shape that is curved to be convex to the outer side in the radial direction of the axis O in a cross-sectional view including the axis O. The mixing surface S1b is smoothly connected to a cylindrical surface S2 located on the rear side.

[0062] According to the aforementioned configuration, since the mixing surface S1b is curved to be convex to the outer side in the radial direction of the axis O, the fuel and air can be more gradually contracted. Therefore, it is possible to further reduce a pressure loss in the mixing space 32V.

[0063] The second embodiment of the present invention has been described above. Further, various changes and modifications can be made to the aforementioned configuration without departing from the gist of the present invention.

Third Embodiment

[0064] Subsequently, a third embodiment of the present invention will be described with reference to FIG. 4. In addition, configurations similar to those of each of the aforementioned embodiments are denoted by the same reference numerals, and repeated description will not be provided. As shown in FIG. 4, in a combustor 1 according to the present embodiment, shapes of a nozzle 11b and an air introduction pipe 12b are different from each of the aforementioned embodiments. The nozzle 11b extends while being eccentric in the radial direction with respect to the axis O from the distal end 11T toward the rear end 11R. More specifically, the nozzle 11b is formed by alternately connecting a portion which is eccentric with respect to the axis O (an eccentric portion E1) and a portion centered on the axis O (a centered portion C1). Further, the eccentric portion E1 and the centered portion C1 are connected in a smooth curved surface shape.

[0065] Furthermore, the air introduction pipe 12b extends while being eccentric in the radial direction with respect to the auxiliary axis O2 from the intermediate portion 32 side toward the rear. More specifically, the air introduction pipe 12b is formed by alternately connecting a portion which is eccentric with respect to the auxiliary axis O2 (an eccentric portion E2) and a portion centered on the auxiliary axis O2 (a centered portion C2). Further, the eccentric portion E2 and the centered portion C2 are connected in a smooth curved surface shape.

[0066] According to the aforementioned configuration, the nozzle 11b extends while being eccentric in the radial direction with respect to the axis O from the distal end 11T side to the rear. Therefore, for example, as compared with a case in which the nozzle 11b extends linearly along the axis O, more turbulent flow components can be imparted to the flow of the fuel and air in the nozzle 11b. As a result, it is possible to further promote the mixing of fuel and air in the nozzle 11b.

[0067] Furthermore, according to the aforementioned configuration, the air introduction pipe 12b extends while being eccentric in the radial direction with respect to the auxiliary axis O2 that is the central axis of the air introduction pipe 12b from the intermediate portion 32 side to the rear. Therefore, for example, as compared to a case in which the air introduction pipe 12b extends linearly along the auxiliary axis O2, more turbulent flow components can be imparted to the air flow in the air introduction pipe 12b. As a result, it is possible to further promote mixing of fuel and air in the mixing space 32V.

[0068] The third embodiment of the present invention has been described above. Further, various changes and modifications can be made to the aforementioned configuration without departing from the gist of the present invention.

Fourth Embodiment

[0069] Next, a fourth embodiment of the present invention will be described with reference to FIGS. 5 and 6. In addition, configurations similar to those of each of the aforementioned embodiments are denoted by the same reference numerals, and repeated description will not be provided. As shown in FIGS. 5 and 6, in the present embodiment, a configuration of an air introduction pipe 12c is different from those of each of the aforementioned embodiments. The air introduction pipe 12c has an upstream part 12c1 extending along the aforementioned auxiliary axis O2, and a downstream part 12c2 connected to a downstream side (a front side) of the upstream part 12c1. As shown in FIG. 6, the downstream part 12c2 is gradually twisted from the one side in the circumferential direction of the axis O toward the other side, from the intermediate portion 32 side to the rear. That is, the downstream part 12c2 is inclined with respect to the axis O in a cross-sectional view including the axis O.

[0070] According to the aforementioned configuration, the air introduction pipe 12c is twisted to be directed from one side in the circumferential direction of the axis O toward the other side from the intermediate portion 32 side to the rear. Therefore, the swirl component directed from one side in the circumferential direction toward the other side can be imparted to the flow of the air which passes through the air introduction pipe 12c. As a result, it is possible to further promote mixing of fuel and air in the mixing space 32V.

[0071] The fourth embodiment of the present invention has been described above. Further, various changes and modifications can be made to the aforementioned configuration without departing from the gist of the present invention.

Fifth Embodiment

[0072] Subsequently, a fifth embodiment of the present invention will be described with reference to FIG. 7. In addition, configurations similar to those of each of the aforementioned embodiments are denoted by the same reference numerals, and repeated description will not be provided. As shown in FIG. 7, in the present embodiment, a lightening part VL as a hollow part is formed in a portion of the distal end portion 31 on the outer peripheral side of the nozzle 11. The lightening part VL has a cross-sectional shape along the outer shapes of the nozzle 11 and the mixing surface S1. The lightening part VL communicates with the outside. That is, air can circulate in the lightening part VL.

[0073] According to the aforementioned configuration, the lightening part VL as the hollow part is formed in the portion closer to the outer peripheral side than the nozzle 11 at the distal end portion 31. As a result, convection is generated in the air exposed to the high temperature of the flame in the lightening part VL. Since the uneven temperature distribution along the nozzle 11 is reduced by the convection, the flame formed from the nozzle 11 can be more effectively held.

[0074] The fifth embodiment of the present invention has been described above. Further, various changes and modifications can be made to the aforementioned configuration without departing from the gist of the present invention.

Sixth Embodiment

[0075] Next, a sixth embodiment of the present invention will be described with reference to FIG. 8. In addition, configurations similar to those of each of the aforementioned embodiments are denoted by the same reference numerals, and repeated description will not be provided. As shown in FIG. 8, in the present embodiment, a protruding part 33P protruding toward the mixing space 32V side along the axis O is provided on a surface facing the front side of the proximal end portion 33 (that is, a central surface S4). The protruding part 33P has a columnar shape centered on the axis O, and a fuel supply hole 40b through which the fuel space 33V and the mixing space 32V communicate with each other is formed on the outer peripheral surface (a protruding part outer peripheral surface 33S). A plurality of fuel supply holes 40b are formed at intervals in the circumferential direction of the axis O. That is, the fuel guided by the fuel supply hole 40b is directly supplied (sprayed) into the mixing space 32V.

[0076] According to the aforementioned configuration, the protruding part 33P protruding into the mixing space 32V along the axis O is provided on the front side of the proximal end portion 33. Further, the fuel supply hole 40b is formed on the outer peripheral surface (the protruding part outer peripheral surface 33S) of the protruding part 33P. Therefore, fuel can be supplied to a region in the mixing space 32V closer to the nozzle 11. As a result, it is possible to further promote mixing of fuel and air in the mixing space 32V.

[0077] The sixth embodiment of the present invention has been described above. Further, various changes and modifications can be made to the aforementioned configuration without departing from the gist of the present invention.

Seventh Embodiment

[0078] Subsequently, a seventh embodiment of the present invention will be described with reference to FIG. 9. In addition, configurations similar to those of each of the aforementioned embodiments are denoted by the same reference numerals, and repeated description will not be provided. As shown in FIG. 9, in the present embodiment, a cylindrical extension cylinder part 33T centered on the axis O is provided on a central surface S4 of the proximal end portion 33. Furthermore, a cylindrical outer extension cylinder part 33U centered on the axis O is provided on an annular surface S3c of the proximal end portion 33. The fuel supply hole 40c is formed on the central surface S4. One fuel supply hole 40c is formed on the axis O. A plurality of air holes 50 penetrating the extension cylinder part 33T in the radial direction are formed in the extension cylinder part 33T. The mixing space 32V and the space on the inner peripheral side of the extension cylinder part 33T communicate with each other by the air hole 50.

[0079] According to the aforementioned configuration, the air guided into the mixing space 32V through the air introduction pipe 12 is mixed with fuel in the mixing space 32V to form a premixed gas. By igniting the premixed gas, a flame is formed on a downstream side from the nozzle 11 of the distal end portion 31. Here, the fuel supply hole 40c is formed on a surface facing the distal end 11T side of the portion surrounded by the plurality of air introduction pipes 12 in the proximal end portion 33 (a central surface S4). That is, the fuel is injected from the fuel supply hole 40c in the direction of the axis O. Further, the fuel supply hole 40c is covered with the extension cylinder part 33T from the outer peripheral side. In addition, the extension cylinder part 33T is formed with an air hole 50 through which the mixing space 32V communicates with the space on the inner peripheral side of the extension cylinder part. Therefore, after mixing the fuel and air to a certain extent in the space on the inner peripheral side of the extension cylinder part 33T, the air-fuel mixture can be supplied to the mixing space 32V. That is, it is possible to further promote mixing of fuel and air in the mixing space 32V.

[0080] Furthermore, since the fuel supply hole 40c is provided on the axis O, the fuel concentration increases in the mixing space 32V as the portion is closer to the axis O. Therefore, in the flame region formed on the downstream side of the nozzle 11, a fuel concentration becomes the highest in the region through which the axis O passes. In other words, the fuel concentration is relatively low in the inner peripheral surface of the nozzle 11, the inner surface of the mixing space 32V, and a region along the surface on an outer side in the radial direction of each air introduction pipe 12 (an introduction pipe outer side surface 12B). As a result, it is possible to reduce the likelihood that flashback occurs along these surfaces. Therefore, the combustor 1 and the combustor array 100 can be operated more stably.

[0081] The seventh embodiment of the present invention has been described above. Further, various changes and modifications can be made to the aforementioned configuration without departing from the gist of the present invention. As a modified example common to the each of the above embodiments, the number of the combustors 1 included in the combustor array 100 is not limited to nine, and may be eight or less or ten or more. Further, the number of air introduction pipes 12 in the combustor 1 is not limited to four, and may be three or less or five or more.

[0082] Furthermore, the combustors 1 in the above-described combustor array 100 can also be disposed in a staggered manner as shown in FIG. 10 (a first modified example). Specifically, a plurality of combustors 1 are arranged in a plane orthogonal to the axis O in a staggered manner so that the positions of the axes O are different from each other. Moreover, as shown in FIG. 11, it is also possible to form each combustor 1 in a hexagonal shape when viewed from the direction of the axis O, and to arrange the combustors in a honeycomb shape by bringing their end faces into contact with each other (a second modified example). In addition, as shown in FIG. 12, it is also possible to configure an annular combustor array 100 by forming outer diameters of each of the combustors 1 in a circular arc shape and connecting the combustors 1 in the circumferential direction (a third modified example).

[0083] Further, in each of the above-described embodiments and modified examples, examples in which the combustor 1 is arranged on a plane have been described. However, as shown in FIG. 13, it is also possible to adopt a configuration in which the combustors 1 are arranged along a curved surface (a fourth modified example). Specifically, these combustors 1 are arranged along a curved concave surface that is convex from one to the other. Note that such a curved surface may be one continuous surface. It may be a polyhedron formed by a plurality of planes connected to each other.

[0084] While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.

EXPLANATION OF REFERENCES

[0085] 100 Combustor array [0086] 1 Combustor [0087] 11, 11b Nozzle [0088] 11R Rear end [0089] 11T Distal end [0090] 12, 12b, 12c Air introduction pipe [0091] 12c1 Upstream part [0092] 12c2 Downstream part [0093] 12A Introduction pipe inner side surface [0094] 12B Introduction pipe outer side surface [0095] 31 Distal end portion [0096] 32 Intermediate portion [0097] 32V Mixing space [0098] 33 Proximal end portion [0099] 33P Protruding part [0100] 33S Protruding part outer peripheral surface [0101] 33T Extension cylinder part [0102] 33U Outer extension cylinder part [0103] 33V Fuel space [0104] 40, 40b, 40c Fuel supply hole [0105] 50 Air hole [0106] C1, C2 Centered part [0107] E1, E2 Eccentric part [0108] O Axis [0109] O2 Auxiliary axis [0110] S1, S1b Mixing surface [0111] S2 Cylindrical surface [0112] S3 Annular surface [0113] S4 Center plane [0114] VL Lightening part [0115] X High concentration region