CFD – Tool for Choosing a Suitable Flow Measurement Methods

Abstract

Verifying guaranteed turbine parameters, especially flow rate, is essential after turbine or pump-turbine rehabilitation. Extensive changes in the hydraulic circuit are realized in the case of the transformation of an existing hydropower plant (HPP) to a pumped storage power plant (PSP), replacing vertical Kaplan with a new reversible Francis turbine. The article introduces a methodology for choosing a suitable flow measurement method. Computational fluid dynamics (CFD) supported by standards (IEC, ASME, ISO) and scientific literature serves as a tool for choosing a suitable flow measurement method, its optimal position in the penstock, and quantifying the value of uncertainty. Two main flow measurement methods – the current meter and the ultrasonic method - were considered in this article. A “virtual flow measurement” was performed based on the velocity field obtained from the CFD model. The reconstructed flow rates obtained from the virtual measurement by both methods were compared with exact flow rate values from CFD. The flow deviation’s sensitivity to the current meter position or the ultrasonic paths rotation was performed for the selected profiles. The profiles with small deviations and low sensitivity to rotation correspond to the recommended profiles according to the standards.