STEAM TURBINE

To improve efficiently while mixing parallel blades and three-dimensional blades.SOLUTION: A steam turbine is equipped with a rotor shaft, a plurality of rotor vane rows, a casing, and a plurality of stator vane rows. The plurality of rotor vane rows is equipped with a plurality of upstream rotor vane rows disposed in an upstream area in a main channel, and a plurality of downstream rotor vane rows disposed in a downstream area with respect to the upstream area in the main channel. The upstream rotor vane row has a plurality of parallel blades, and the downstream vane row has a plurality of stator vanes disposed at intervals in a circumferential direction. An outer peripheral surface of the rotor shaft is formed so as to gradually increase a diameter in parallel with an axis or outward in a diametrical direction toward a second side in an axial direction with respect to the axis, on a cross section parallel with the axis in an area where the three-dimensional blades are disposed in the downstream area.SELECTED DRAWING: Figure 1 【課題】平行翼及び三次元翼を混在させつつ、効率を向上する。【解決手段】蒸気タービンは、ロータ軸と、複数の動翼列と、ケーシングと、複数の静翼列と、を備える。複数の動翼列は、主流路における上流領域に配置されている複数の上流動翼列と、主流路において上流領域に対して下流領域に配置されている複数の下流動翼列と、を備え、上流動翼列は、複数の平行翼を有し、下流動翼列は、複数の三次元翼を有し、静翼列は、周方向に間隔をあけて配置された複数の静翼を有し、ロータ軸の外周面は、下流領域における三次元翼が配置される領域で、軸線と平行な断面において、軸線と平行、又は軸線に対して軸方向の第二側に向かって径方向の外側に漸次拡径するよう形成されている。【選択図】図１