Rotary machine

A rotary machine comprising:

• a casing;
• a nozzle configured to introduce a fluid from an outer circumferential side of the casing to an inner circumferential side of the casing in a radial direction;
• a volute having a space in communication with the nozzle at the outer circumferential side;
• a guide section having a first flow path in communication with the volute at an inner circumferential side of the volute, and a second flow path extending from an inner circumferential side of the first flow path toward a downstream side of the casing along a central axis, and configured to guide the fluid introduced from the volute;
• and
• an impeller connected to the guide section in an axial direction into which the fluid guided by the guide section is introduced,
• wherein the volute comprises:
• an annular opening section in communication with the guide section at an inner circumferential side of the space of the volute;
• and
• an inner wall surface extending from the annular opening section to a same position, with respect to the axial direction, as a position of a first portion of the impeller in the axial direction, thereby increasing a width dimension along the central axis,
• wherein the first portion of the impeller is a part at a most upstream side of the casing in the axial direction among parts of the impeller, at a side opposite from a connection section with the central axis sandwiched therebetween, of which a dimension in the axial direction gradually decreases,
• a plurality of vanes are installed at the first flow path of the guide section and extend toward the second flow path,
• the plurality of vanes comprises:
• first vanes, each having an inner circumferential vane and an outer circumferential vane connected to each other;
• and
• second vanes, installed at positions different from those of the first vanes in a circumferential direction, and each second vane only having an outer circumferential vane which is the same cross-sectional profile as the outer circumferential vane in the each of the first vanes,
• the inner circumferential vanes of the first vanes are disposed nearer to the second flow path than the outer circumferential vanes of the first vanes and the second vanes, and
• a height of the first vanes along the central axis is the same as that of the second vanes.