Application of CFD to the Design of Manifolds Employed in the Thermodynamic Method to Obtain Efficiency in a Hydraulic Turbine

Abstract

This study presents the design and implementation of different types of manifolds (sampling system) to measure water flow properties (velocity, pressure, and temperature) through the high- and low-pressure section of a Francis-type low head hydraulic turbine (LHT of 52 m) to calculate it is efficiency using the Thermodynamic Method (TM). The design of the proposed manifolds meets the criteria established in the “International Electrotechnical Commission—60041” Standard for the application of the TM in the turbine. The design of manifolds was coupled to the turbine and tested by the Computational Fluid Dynamics (CFD) application, under the same experimental conditions that were carried out in a power plant, without the need for on-site measurements. CFD analyses were performed at different operating conditions of volumetric flow (between values of 89.67 m3/s and 35.68 m3/s) at the inlet of turbine. The mechanical power obtained and the efficiency calculated from the numerical simulations were compared with the experimental measurements by employing the Gibson Method (GM) on the same LTH. The design and testing of manifolds for high- and low-pressure sections in a low head turbine allows for the constant calculation of efficiency, avoiding breaks in the generation of electrical energy, as opposed to other methods, for example, the GM. However, the simulated (TM) and experimental (GM) efficiency curves are similar; therefore, it is proposed that the design of the manifolds is applied in different geometries of low-head turbines.