Performance Analysis of Multipath Acoustic Flowmeters Under Various Hydraulic Conditions

by Francis C. Lowell, Jr., O.R.E. Inc, Falmouth, United States,
James T. Walsh, O.R.E. Inc, Falmouth, United States,

Document Type: Proceeding Paper

Part of: Waterpower '91: A New View of Hydro Resources


Multipath, crossed plane acoustic flowmeters are being increasingly used for hydroelectric turbine efficiency measurement both for acceptance testing and efficiency mapping of units in order to allow more nearly optimum operation of multiunit powerplants. Because efficiency measurement requires accurate flowrate determination, one key question is how accurate the flow measurement actually is in the non-ideal environment of the typical powerplant. Data from eight separate 8-path crossed plane acoustic flowmeter installations and calibrations is presented, and site-specific problems are discussed. Individual acoustic path velocity data was logged during each calibration run, allowing estimation of the velocity profile and cross flow components resulting from the piping configuration upstream of the flowmeter, and allowing estimation of the effect of these profiles on flowmeter accuracy. The conclusion of this analysis is that high accuracy (± 0.5% of flowrate) can be achieved through proper orientation and location of a single acoustic plane with respect to the upstream piping configuration, even when the velocity profiles appear distorted on individual paths due to cross flow in the measurement section. These results are important when applied to installations which do not have crossed planes.

Subject Headings: Acoustics | Hydraulics | Flow measurement | Fluid velocity | Velocity profile | Hydro power | Power plants | Turbines

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