Combustion burner for boiler

1. A combustion burner comprising:

an inner cylinder defining, at a radially-inner side, a fuel supply passage for supplying fuel;

an outer cylinder surrounding the inner cylinder and defining an air supply passage between the inner cylinder and the outer cylinder; and

a swirler in the air supply passage, the swirler being configured to swirl air in the air supply passage,

wherein the swirler includes a plurality of blades radially disposed between the inner cylinder and the outer cylinder, the plurality of blades extending from a leading edge on an air-supply side toward a trailing edge on a combustion-space side of the air supply passage,

wherein the trailing edge of each of the plurality of blades includes a cutout portion positioned at least on an inner cylinder side such that the trailing edge at the cutout portion recedes from the combustion-space side upstream in a burner axial direction,

wherein each of the plurality of blades has, at least on the inner cylinder side of the blade, a section with a thickness varied in the burner axial direction, the thickness being smaller at the trailing edge on the combustion-space side including the cutout portion than at a maximum-thickness section of the blade, and

wherein, for each of the plurality of blades, the cutout portion is defined such that a cutout width increases from an outer cylinder side toward a center part in a radial direction, as seen from a side surface of the blade.

2. The combustion burner for a boiler according to claim 1 ,

wherein the side surface is a first side surface and each of the plurality of blades has a second side surface, and the first side surface or the second side surface includes an inclined portion at least on the inner cylinder side, the inclined portion being inclined so that the thickness of the blade decreases toward the trailing edge on the combustion-space side.

3. The combustion burner for a boiler according to claim 2 ,

wherein the inclined portion is a first inclined portion, the first side surface includes the first inclined portion, the second side surface includes a second inclined portion corresponding to the first inclined portion, and the first inclined portion and the second inclined portion define the trailing edge on the combustion-space side into a tapered shape.

4. The combustion burner for a boiler according to claim 1 ,

wherein the side surface is a first side surface and each of the plurality of blades has a second side surface, and the first side surface or the second side surface includes an inclined portion at least on the inner cylinder side, the inclined portion being inclined so that the thickness of the blade decreases toward the trailing edge on the combustion-space side,

wherein each of the plurality of blades is inclined from the burner axial direction,

wherein each of the plurality of blades has a bent region bent at the air-supply side so as to have a curvature center at the air-supply side, and a linear region defined linearly at the combustion-space side, and

wherein the linear region includes a first portion having a constant thickness, and a second portion which is positioned on a downstream side of the first portion and at which the first side surface or the second side surface includes the inclined portion such that the thickness of the blade decreases toward the trailing edge.

5. The combustion burner for a boiler according to claim 4 ,

wherein the inclined portion is inclined by an angle in a range of from 5 to 10° with respect to a portion of the first side surface or the second side surface other than the inclined portion, in the linear region.

6. The combustion burner for a boiler according to claim 1 ,

wherein a first part of the trailing edge at an outer circumferential surface of the inner cylinder is positioned further upstream than a second part of the trailing edge at an inner circumferential surface of the outer cylinder.

7. The combustion burner for a boiler according to claim 6 ,

wherein the plurality of blades is inclined in the same direction with respect to the burner axial direction and spaced from one another in a burner circumferential direction, the leading edge on the air-supply side of a first of the plurality of blades and the trailing edge on the combustion-space side of a second of the plurality of blades being overlapped in the burner axial direction to define an overlapping region,

wherein the first of the plurality of blades is adjacent to the second of the plurality of blades, and

wherein the cutout portion is defined such that the overlapping region remains.

8. The combustion burner for a boiler according to claim 1 ,

wherein, for each of the plurality of blades, the leading edge extends radially as seen from the side surface of the blade.