Axial flow rotating machine and diffuser

An axial flow rotating machine comprising:

• a rotor that includes a plurality of rotor blades and is configured to freely rotate around an axial line;
• a stator that includes a plurality of stator blades adjacent to the plurality of rotor blades;
• an axial flow rotating portion that is defined by the rotor and the stator;
• and
• a diffuser that is connected to the axial flow rotating portion on a downstream side of the axial flow rotating portion and that extends in an axial direction to define a circular flow path;
• wherein:
• an inner-circumferential inner wall of the diffuser includes a first inclination portion and a second inclination portion located downstream of the first inclination portion;
• the second inclination portion is continuous with the first inclination portion;
• the first inclination portion and the second inclination portion are inclined in opposite directions whereby the first inclination portion is inclined toward an outer-circumferential inner wall of the diffuser and the second inclination portion is inclined away from the outer-circumferential inner wall of the diffuser;
• the second inclination portion extends from the first inclination portion to a downstream end of the inner-circumferential inner wall of the diffuser such that a diameter of the inner-circumferential inner wall of the diffuser decreases over an entirety of the second inclination portion;
• the first inclination portion is a straight linear portion inclined at a first inclination angle in a cross section of the diffuser along the axial direction;
• and
• the second inclination portion is a straight linear portion inclined at a second inclination angle in the cross section of the diffuser along the axial direction.