Authors: ZHANG Fei, GAO Zhong-xin, PAN Luo-ping, GE Xin-feng (China Institute of Water Resources and Hydropower Research, Beijing 100038, China)

Abstract: The pressure fluctuation in Francis turbine draft tubes during partial load was analyzed based on field test data of the Three Gorges Hydropower Plant. Inapplicability of two current used formulas for calculating the vortex belt frequency of turbine draft tube pressure fluctuation was analyzed. The test results indicated that in lower partial load, under certain water head the main frequency of draft tube pressure fluctuation decrease with the increase of discharge. In higher partial load the main frequency has the distribution of V type with the variation of discharge, which may have the relation with draft tube inherent frequency. In certain guide vane angle, during partial load the main frequency of draft tube pressure fluctuation had no definite relation with water head. Meanwhile, in partial load the draft tube pressure fluctuation may have direct influence to unit stability. The pressure fluctuation in draft tube was the main cause influencing the stability parameter variation.

Key words: Draft tube, partial load, pressure fluctuation, main frequency, stability

Published in: Journal of Hydraulic Engineering, Vol. 42, No. 10, 2011
Article ID: 0559-9350 (2011) 10-1234-05