NUMERICAL INVESTIGATION OF THE INFLUENCE OF SPECIAL STRUCTURES ON SUPPRESSION OF PRESSURE PULSATIONS IN THE DRAFT TUBE OF A HIGH-HEAD HYDRAULIC TURBINE

摘要

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 flow in the outlet diffuser corresponds to vortex-core flow. 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 influence of various structural inserts into the draft tube, such as fins, a cross piece, and a hollow cylinder in the draft-tube cone. Consideration has been given to the influence of various constructions on the structure of flow 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 flow in the diffuser of the hydraulic-turbine draft tube.