Experimental Study of Unsteady Flow Behind a Francis Turbine Runner Exit

The flows behind the runner exit of a high specific speed Francis turbine were studied by using a probe for unsteady water flow. A 5-hole pitot probe was used along with pressure transducers, set near the holes, to measure the flows. The mean velocity and total head distributions behind the runner exit between one pitch of the runner vanes from the crown to the band, were examined under five operating conditions. Especially, flows near the vane wake and flows when a reverse flow occurred on the suction surface were examined. And, some comparisons were made with flow pattern obtained by the oil film method.