By installing a cylinder 53 having a bell-mouth construction to the downstream side of a combustor basket 2 a , compressed air flowing between the combustor basket 2 a and an external cylinder 2 c is throttled. In addition, by having a cross section of the downstream-side end surface of the cylinder 53 shaped in a semicircle and providing a back surface wall 2 d having a curvature being equivalent to a curvature of the semicircular curved surface, compressed air flow making 180 degrees turn can be made uniform and free from disturbance.
1. A combustor comprising:
a pilot nozzle provided on a center axis of said combustor, wherein the pilot nozzle performs diffusion combustion;
a plurality of main nozzles equally spaced apart from each other and provided around an outside circumference of the pilot nozzle, wherein the plurality of nozzles perform premixed combustion;
a combustor basket covering the outside circumferences of the pilot nozzle and the plurality of main nozzles;
a cylinder connected to an end of the combustor basket adjacent to a bases of each of the main nozzles, wherein the cylinder includes an outside wall curved upward in a direction from the tips of each of the main nozzles to the bases of each of the main nozzles wherein a cross-section of the outside wall adjacent to the bases of the main nozzle has a semicircular configuration;
an external cylinder provided around an outside circumferences of the combustor basket and the cylinder wherein a space between an inside wall of the external cylinder and an outside wall of the combustor basket or the cylinder functions as a passageway for compressed air;
a back surface wall that covers the inner side of the external cylinder around the bases of the main nozzles of the external cylinder, the back surface wall having a surface curved toward the inside wall of the external cylinder where a back surface is formed into a bowl shape with respect to the position of the bases of the main nozzles; and
a turning vane formed of a one-piece material and having a substantially arc-shape is provided between each of the main nozzles that are circumferentially adjacent to each other,
wherein the turning vane curves from the outside circumference of the main nozzle towards a central axis of the main nozzle, when viewed from a direction upstream of the cylinder, and connects the side surfaces of each of the adjacent main nozzles.
2. A combustor as described in claim 1 :
wherein, the cylinder has a tapered portion curved in an upward direction from side of tips of the main nozzles, and the tapered portion is constructed so as to bend, gently rounded.
3. A combustor as described in claim 1 :
wherein, a cross section being formed by a curved surface in a semicircular configuration on the outside wall of the cylinder and a curved surface of an inside wall of the back surface wall is approximately constant.
4. A combustor as described in claim 1 :
wherein, a curvature of the turning vanes is approximately equal to the curvature of a curved surface in a semicircular configuration on the outside wall of the cylinder.