| 主权项 |
1. A fluid machine utilizing an unsteady flow, the fluid machine comprising a casing having an annular shape and an axial cross-section of a non-streamline shape, and an impeller disposed at a throat section inside the casing to rotate around an axis, wherein the fluid machine is configured to split a surrounding flow into an internal flow and an external flow at a front edge and to force the flows to cause separations, such that vortex streets are formed downstream of the casing by the separations, and a negative pressure region having a cell structure in an annular direction is formed by the vortex streets and vortex street fluctuations, whereby a velocity of the internal flow inside the casing is increased,
wherein a reference line serving as a reference for forming the thickness of the casing connects the front edge and a rear edge in the axial cross-section, and includes a cycloid curve having a convex portion at the throat section between the front and rear edges, the throat section and a vortex generating portion disposed downstream of the throat section to generate the negative pressure region are formed on a radially inner circumferential face of the casing, a first outflow gradient is formed on an outer circumferential face of the casing and at the rear edge to separate the external flow at the rear edge, and a second outflow gradient is formed on a throat-side adjacent face adjacent to the vortex generating portion and at a boundary between the throat-side adjacent face and the vortex generating portion to separate the internal flow, the first outflow gradient is equal to or larger than a gradient of a conical generatrix line connecting the front edge and the rear edge, and the second outflow gradient is equal to or smaller than a reference gradient, the reference gradient being a gradient of a front end of the vortex generating portion when the reference cycloid curve forms the inner circumferential face, and the negative pressure region of high vorticity is generated behind the vortex generating portion by virtue of the non-streamline shaped casing to increase the velocity of the internal flow. |
