Patent ID: 7770395

Claim:
A combustor comprising: a pilot nozzle provided at a center of an axis of the combustor, and performing diffusion combustion; main nozzles provided circumferentially around the pilot nozzle so as to be equally spaced with each other, and performing premixed combustion; a combustor basket covering outside circumferences of the pilot nozzle and the main nozzles; an external cylinder provided around an outside circumference of the combustor basket so as to form a passageway of a compressed air between an inside wall thereof and an outside wall of the combustor basket; and a cylinder-type sleeve provided with a side wall having a first end and formed in a tapered shape which is connected to a distal end serving as an inlet of the compressed air of the external cylinder, wherein a length of the side wall of the sleeve changes in a manner that the longer a distance to a compressed air outlet which discharges the compressed air is, the longer a length of the side wall of the sleeve is, while the shorter a distance to the compressed air outlet is, the shorter a length of the side wall of the sleeve is, and wherein an open space is formed between an external surface of the side wall of the sleeve and a casing of a gas turbine, the sleeve first end being spaced from the casing.