OPERATION METHOD FOR PROPELLER TYPE HYDRAULIC TURBINE

PURPOSE:To obtain high efficiency characteristics by shifting a draft tube under pressure in such a way as to keep the predetermined ratio of propeller outer diameter to draft tube inner diameter when larger or smaller output than the predetermined operation output is required. CONSTITUTION:The outer diameter of a propeller 3 is taken at Do and the inner diameter of a draft tube 5 taken at De respectively. In addition, a draft tube motion control device is provided so as to make the cross sectional area of the tube 5 variable relative to the change of operation output. When the operation output is less than the boundary of the change point of De/Do, the draft tube 5 moves under pressure along the curve of De/Do = 90%. Also, when the operation point is equal to or larger than the aforesaid change point, the tube 5 is so withdrawn as to be along the curve of De/Do = 98%. As aforementioned, the draft tube 5 is so pressed and moved that a waste loss is minimum with the operation output along the boundary of the change point of the predetermined constant value of De/Do, thereby giving desirable efficiency characteristics at all times.