Numerical Investigation of the Influence of Special Structures On Suppression of Pressure Pulsations in The Draft Tube of a High-Head Hydraulic Turbine

Abstract

The authors have performed numerical simulation of pressure pulsations in the draft tube of a hydraulic turbine that are excited by large-scale vortex structures. Numerical simulation of unsteady transfer in the draft tube in different operating regimes of the turbine has been carried out. It has been shown that the structure of fl ow in the outlet diffuser corresponds to vortex-core fl ow. Calculated data have been compared with experimental results and their agreement has been shown. To suppress pressure pulsations, a study has been made of the infl uence of various structural inserts into the draft tube, such as fi ns, a cross piece, and a hollow cylinder in the draft-tube cone. Consideration has been given to the infl uence of various constructions on the structure of fl ow behind the wheel and on pressure pulsations on the draft-tube wall. A comparison has been made of the constructions and optimum parameters have been selected to stabilize the fl ow in the diffuser of the hydraulic-turbine draft tube.