Measuring Flow Through A Bulb Turbine At Rock Island Dam Using An Acoustic Scintillation Flow Meter

摘要

Recent optimization work at Rock Island Powerhouse Two on the Columbia River byPublic Utility District No. 1 of Chelan Co., has afforded the opportunity to utilize theAcoustic Scintillation Flow Meter (ASFM) system to perform discharge measurements ina run-of-the-river horizontal-shaft bulb turbine. The intakes to these turbines presentparticular problems in making absolute measurements of the turbine flow. The ASFMwas chosen for the absolute flow measurements at Unit U6 because of its ability tomeasure flow using unobtrusive acoustic paths oriented directly across the intake. Theabsolute flow was measured at two heads, over a series of discharges covering the fulloperating range of the turbine. Sufficient transducers were available for the instrumentto install ten acoustic paths in one bay and twenty in the other. The additional density inone bay allowed a determination of the effect of the trash rack support structures on thevertical variations in the flow field. The contribution of this variability to the uncertaintyin the absolute flow measurement, along with the uncertainty in the measurement of theflows in the boundary zones at the top and bottom of the measurement section, arediscussed.