| 摘要 |
PURPOSE:To improve the efficiency of a water turbine without need for providing a water introducing board by specifying the sectional area in each position of a semi-spiral casing and making the distribution of flow velocity at the inlet part of a stay vane nearly uniform in a circumferential direction. CONSTITUTION:The sectional area in each position of the spiral part 1a of a semi-spiral casing 1 is set as shown by the table, when the winding starting point D0 of a scroll in the tangential position of the entering and discharging directions of a fluid to the circumference of a runner 4, is defined as a starting point, when the percentage of the sectional area of the casing 1 in an arbitrary position toward an winding end part D1 in the flowing direction of the fluid, to the sectional area of the casing 1 at the starting point is defined as Ak, and when the ratio of the percentage of the winding angle up to the arbitrary position to the whole winding angle from the winding starting point D0 to the winding end part D1 is defined as thetak. By this structure, the distribution of flow velocity at the inlet part of a stay vane 2 can be made nearly uniform, improving the efficiency of a water turbine.
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