| 摘要 |
PURPOSE:To check the growth of a swirl stream flowing in a draft tube from a runner of a water turbine and rectify it as well as to prevent a drop of turbine performance due to the swirl stream from occurring, by installing at least more than one piece of straightening vanes in a part where a flow velocity inside the draft tube is relatively slow. CONSTITUTION:A draft tube 1 is interposingly installed between a water turbine 2 and a tailrace 4 to discharge water flowing out of a runner 3 of the water turbine 2 to the tailrace 4. In this case, at least more than one piece of streamlined straightening vanes 5, whose each rear part is thinly formed, is set up inside the draft tube 1. And, size of each vane 5 is set in the relation that length Y is 3.X<=Y<=6.X to thickness X of the vane 5. As for a setup position of the vane 5, supposing that a distance ranging from a center line of a turbine main shaft 6 to a tip of the vane 5 is set down to L and a distance ranging from an outlet end face 7 of the draft tube 1 to a rear end of the vane 5 is set down to M, it is set up in a position where the distance between L and M comes 2.D<=L<=4.D, M>=0.5d to an inlet diameter D of the draft tube 1. |
