CHARACTERISTIC FIELDS OF COUNTER-ROTATING HYDROTURBINE STAGES

Abstract

The research investigated two counter-rotating stages with different blade grids of pump impellers. Using the ANSYS CFX software package, the fields of pressure-energy characteristics of stages with and without partial blade trimming were determined. In accordance with modeling practice recommendations for energy characteristics of pump equipment, a 5 % discrepancy between physical and numerical modeling was accepted in this software package. The study explored two types of stages in terms of structural configuration: the first being a narrow-blade stage, and the second being a wide-blade stage. The first stage of the research involved determining the operating points of the two investigated counter-rotating stages and constructing pressure-energy characteristics. These characteristics comprised variations in head, power, and efficiency coefficient concerning the flow rates of the pump equipment. The second stage of the research involved determining the pressure-energy characteristics and the operating zones of the counter-rotating stages, where the impeller was trimmed by 15 %. This allowed forecasting the potential decrease in stage head characteristics, obtaining additional characteristics of trimmed stages, and enabling the modeling of the corresponding pump equipment operation across a wider range of stage head characteristics. Based on the results of this study, operating points were obtained for constructing energy characteristics, allowing for the operation of stages with different geometric characteristics (up to 15 % impeller trimming). A characteristic field was created within which the stage head could be adjusted by trimming. The first stage performed reasonably well at lower flow rates, unlike the second stage, which exhibited inferior performance both in terms of head and energy efficiency. It was established that not all counter-rotating stages can be adjusted through impeller trimming. This is primarily because it significantly affects the pressure-energy characteristics of the respective pump equipment compared to conventional equipment. In this work, the characteristic values of counter-rotating stages were computed without considering the discharge device, which can significantly influence the energy characteristics of the equipment. Therefore, in further research, based on the designed stages, a spiral discharge will be created, and comprehensive studies of counter-rotating stages with discharge will be conducted to compare the obtained energy characteristics of corresponding equipment variants.