Accuracy of the ultrasonic flow meter used in the hydroturbine intake penstock of the Three Gorges Power Station

Flows in large conduits are always difficult to measure. Ultrasonic flow meters developed in recent years are good for large flow conduits, especially for turbine performance testing in hydroelectric plants, because they are convenient to install, but then accuracy is difficult to estimate and there is no acknowledged estimation method when the installation requirements are not satisfied. The accuracy of the ultrasonic flow meter installed in the Three Gorges power station was analyzed both experimentally and with CFD analyses to analyze the effect of the complex flow field on the metering performance. A reduced scale (1:24) experimental system was built to study a series of cases, with the results showing that the flow error related to the complex flow field is about 0.3%. The penstock flow field of the Three Gorges dam was simulated, with the calculated flow error close to the experimental result. Analysis of the uncertainties in the experimental results and the Three Gorges flow meter measurement shows that the Three Gorges flow meter accuracy is better than 1%; thus the flow meter is sufficiently accurate for the turbine performance testing in the Three Gorges Power Station.

► Installation condition effects were analyzed by experiment and numerical simulation.
► Experiments show that the geometry increases the flowmeter reading by about 0.3%.
► The numerical simulations indicating the error caused by the geometry is 0.2%.
► The overall accuracy of the Three Gorges flowmeter is better than 1%.
► The double-plane flowmeter configuration neutralizes the transverse errors.