Influences of the Runner Gap and Seal Construction on the Safety in Operation of Francis Water Power Sets

The researches indicate that a main reason caused of the phenomenon of the lifting Francis water power sets is the mutation leakage rate of Francis runner. By the analysis of the example for a water power set, the immediate cause which create the water pressure head between the band space and crown space is the mutation leakage rate of Francis runner, and the mutation is related to the runner gap and seal construction . The phenomenon is much more obvious to the low specific speed Francis turbine.