Investigation of the BulbT conical diffuser flow dynamics with TR-PIV and pressure measurements

[摘要] The three dimensional unsteady swirling flow inside the draft tube of a bulb turbine is investigated using time-resolved stereoscopic particle image velocimetry. The measurement plane located inside the conical diffuser, together with synchronous pressure measurements from thirteen sensors distributed across the draft tube, allow to link the draft tube flow dynamics to a known efficiency drop of the turbine. This paper presents the experimental setup and the first observations based on statistical analyses and instantaneous snapshots of the velocity field. After the efficiency drop, the intermittency and skewness of the draft tube pressure recovery are found to be reflected onto the velocity fields. Spectral analysis reveals the presence of a coherent and non-axisymmetric structure that rotates at the same frequency as the runner, but in the opposite direction.

[发布机构] Hydraulic Machine Laboratory (LAMH), Department of Mechanical Engineering, Laval University, Quebec City; QC; G1V 0A6, Canada^1

[关键词] Axisymmetric structure;Conical diffuser;Flow dynamics;Intermittency;Measurement planes;Stereoscopic particle image velocimetry;Time-resolved;Velocity field