A Mathematical Model for the Swirling Flow Ingested by the Draft Tube of Francis Turbines

摘要

We introduce and validate a mathematical model, derived from the turbomachinery throughflow theory, for computing the swirling flow exiting a Francis turbine runner operated within a range of discharge values. This swirling flow, further ingested by the draft tube, is used as inlet condition for numerically assessing the draft tube performance for variable discharge without actually computing the runner. The present methodology can be used when refurbishing the turbine runner, in order to insure that the new runner is a best match for the existing draft tube.