Forecasting the energy characteristics of a reversible hydraulic machine for a head up to 250 m

BACKGROUND: At present, in the pressure zone of 50–650 m for pumped storage power plants, hydroelectric units with classic single-stage radial-axial reversible hydraulic machines, which have a relatively simple design of the impeller and cylindrical guide vane, have received the most widespread energy performance, but are relatively quiet, large-sized and metal-intensive hydraulic machines. Numerical research and design of this type of machines are given special attention. The current trend is the design of flow parts based on numerical simulation of the flow. The most well-known commercial software products that implement finite volume numerical simulations are Ansys Fluent, Ansys CFX, StarCD, Numeca, Flow Vision and CADRUN. In the work under consideration, the calculations were performed using the Ansys CFX software package version 2021R1. Today, due to the lack of numerical capacity, the task of developing and using a technique that will allow obtaining an acceptable result with optimal time spent on data preparation and computational studies remains an urgent task.

AIMS: The aim of the work was to present an “economical” methodology for numerical simulation of energy characteristics.

METHODS: The methodology consists in describing the problem statement, the computational grids used, and the assumptions made for the optimal use of computing resources without a significant loss in the accuracy of the results.

Object of computational research: The presented article investigates the flow part of a radial-axial pump-turbine designed for application to a maximum head of up to 250 m.

RESULTS: Numerical modeling of power characteristics of on-pump and turbine modes is performed. A brief description of the problem statement, computational grids used, and assumptions made is given. A comparison of calculation results with experimental data of model tests is presented. The comparison results are presented in the relative form for the main parameters: pressure, efficiency, reduced rotational speed and flow rate.

CONCLUSIONS: It is recommended to use SST model of turbulence in a stationary statement in order to predict the power characteristics of pump-turbines. The use of economical block-structured grids, as well as the performing of calculations only in the region of one blade of the guide vanes, one impeller blade and a suction pipe with the use of preliminary results of calculations in a spiral chamber allow using computational resources optimally without significant loss of accuracy of the results.