A new Francis runner design procedure to predict static stresses at speed-no-load operation

Hydraulic turbines undergo more start/stop cycles than ever before to meet the rapidly evolving electricity demand occurring in today’s electricity grids. Such cycles imply that the machines will operate more often and for longer periods of time at the speed-no-load (SNL) condition (a condition where the machines run at synchronous speed on the grid in waiting state with no electricity production). In this paper, the combined CFD-FEA procedure used to obtain static stresses under the challenging SNL operating condition is described. Validation with prototype strain gauge measurements, showing the high level of reliability achieved with the procedure developed, is also presented.