DRAFT TUBE INNER PRESSURE PREDICTING AND CONTROLLING METHOD AND STATIC DRAFT HEAD SELECTING METHOD FOR HYDRAULIC MACHINERY

摘要

PROBLEM TO BE SOLVED: To predict pressure in a draft tube with good accuracy when a load is shut out by finding out a minimum pressure of a low pressure side reference cross section and rotating speed from change of an operating condition which is estimated while assuming that phase change is not generated even if pressure of water in a pipe passage becomes saturated steam pressure and less, and finding out minimum pressure by a specified expression. SOLUTION: It is assumed that phase change is not generated even if water pressure in a draft tube 8 is reduced lower than saturated steam pressure of water in its temperature, and operating point change is estimated. A minimum value H2min of pressure of a low pressure side reference cross section of a reversible pump-turbine and rotating speed (n) in this time are found out from its estimated result, and a minimum pressure Hdmin in the reversible pump-turbine is estimated by an expression: Hdmin =H2min -H, and an expression: H=k(Ue2 /2 g). H is a liner outlet part draft tube inner local pressure sinking rate, Ue is liner outlet outer periphery speed when the minimum value H2min is generated, (g) is gravitational acceleration, and (k) is a value found out by an experiment or 0.06. Pressure in the draft tube 8 when a load is shut out is predicted with a high accuracy on the basis of an experiment result by the predicting method.