Acoustic Scintillation Flow Measurements in the Intake at Kootenay Canal Power Plant

Acoustic Scintillation was one of the three intake flow measurement methods tested in the comparisons carried out in Unit #1 at BC Hydro’s Kootenay Canal power plant in October, 2009, sponsored by CEATI (the Centre for Energy Advancement through Technological Innovation) and supervised by the PTC-18 Committee of the ASME. The comparison was run as a blind test; none of the test participants had knowledge of the reference or any other test discharges until after the final results were submitted 30 days after the completion of the measurements. Each unit at Kootenay Canal has a single intake, 7.44 m high and 4.88 m wide. Both current meters and acoustic scintillation sensors had to be deployed in the maintenance gate slot, the only one available for installing instruments. The preferred method to install Acoustic Scintillation Flow Meter (ASFM) sensors is on a fixed frame deployed in a slot. In this case, the slot was wide enough that a combined frame could be used, thus allowing both systems to be operated at the same time, which greatly reduced the time required to collect data and meant that comparisons among all the test and reference methods could be made with simultaneous data. The current meters were mounted on the cross-member of a travelling frame, or trolley, which moved up and down within the larger stationary frame. The ASFM arrays were mounted in pairs on opposite vertical sides of the stationary part of the frame, upstream of the current meter frame. The ASFM transducer pairs formed sixteen sampling paths, spaced at 0.46m vertically. Two paths could be sampled simultaneously: one from the upper 8 and one from the lower 8. The sampling order for the paths had to be arranged such that any two active paths were never within 0.5m of each other or the position of the current meter frame. Each ASFM acoustic path was sampled for 50 seconds; a discharge measurement therefore required approximately 8 minutes, and three could be made at each condition while the current meter sampling was under way. The procedures used to compute the laterally-averaged velocity at each path, and their integration to compute the discharge (including estimation of the boundary layer contribution) are described. The mean of the three individual discharges was reported as the result for each of the 36 flow conditions in the primary program. The results were reported immediately following each run at the site; a period of 30 days was then allowed for review and checking. The final results differed from the field results by an average of 0.04%. The mean difference between the ASFM discharges and the reference was 0.44%.