Turbine and gas turbine

A turbine comprising:

• a turbine rotor that extends along an axis and that is rotatable around the axis;
• a turbine casing that covers the turbine rotor from an outer peripheral side;
• a plurality of turbine rotor vane rows that are arranged in a direction along the axis, the turbine rotor vane rows including a plurality of turbine rotor vanes that are arranged on an outer peripheral surface of the turbine rotor in a circumferential direction around the axis;
• a plurality of turbine stator vane rows that are arranged in the direction along the axis, the turbine stator vane rows including a plurality of turbine stator vanes that are provided on an inner peripheral surface of the turbine casing to be adjacent to the turbine rotor vanes while being on one side in the direction along the axis and that are arranged in the circumferential direction;
• and
• a diffuser in which an exhaust gas flow path through which an exhaust gas flows from the one side to the other side in the direction along the axis is formed, the diffuser being provided closer to the other side in the direction along the axis than a last stage rotor vane row that is closest to the other side in the direction along the axis among the plurality of turbine rotor vane rows,
• wherein the diffuser includes
• an inner cylinder that extends along the axis,
• an outer cylinder that covers the inner cylinder from the outer peripheral side and that forms the exhaust gas flow path between the inner cylinder and the outer cylinder, and
• a plurality of struts that are provided at intermediate positions in the exhaust gas flow path, that connect the inner cylinder and the outer cylinder to each other in a radial direction, and that are arranged in the circumferential direction,
• the outer cylinder includes a first inclined surface that extends from an inner side in the radial direction centered on the axis to become closer to an outer side from an inlet of the exhaust gas flow path on the one side in the direction along the axis toward the other side,
• the first inclined surface forms an angle equal to or larger than 16° and equal to or smaller than 24° with respect to the axis in a cross-sectional view including the axis, and
• a throat width at end portions of the turbine rotor vanes of the last stage rotor vane row that are on the outer side in the radial direction with respect to the axis is set to be larger than a throat width at an intermediate portion in the radial direction.