The Calculation Model of Hydraulic Characteristics in Draft Tube Inlet Zone

To study the influence of hydraulic characteristics in the interface zone between the runner outlet and the draft tube inlet, a decomposition and calculation method of the effective head of hydro turbine is proposed in this paper. Firstly, it analyzes traditional definition and composition of the hydro turbine head, and proposes that inlet zone of the draft tube should be decomposed into few parts detail so that the role of each parts to runner can be reflect in head loss form. Secondly, the outlet circulation of runner is expressed into the head loss by means of the outlet velocity triangle of runner, and combines with the inlet vacuum of the draft tube to obtain the modified expression of the effective head of hydro turbine. At last, Simulation is done with actual hydroelectric plant data, the rationality and error of simulation results are analyzed, and results indicate that proposed method is effective.