An Analysis of Cavitation Damage in a Francis Turbine Operating Under Small Opening Conditionby Liang-jun Cheng, Huazhong Univ of Science &, Technology, Wuhan, China,
Document Type: Proceeding Paper
Part of: Water Power '87
In this paper some new formulae are derived to estimate the pressure and the relative velocities in the crown and the band regions of the Francis turbine runner operating under any gate opening. The so-called ring vortex in the crown region was found by the negative value of W//c and the cavitation damage in the crown and the band regions could be explained by the values of P//c/ gamma , P//b/ gamma , W//c, W//b which are calculated by those formulae. As an example the cavitation damages of a Francis turbine with the specific speed n//s equals 220 (KW,m) operating under four small gate openings at two working heads are illustrated. Now all those formulae derived in this paper are adopted in the preliminary design of a new important hydropower station in order to forecast the danger of cavitation damage of the water turbine.
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