Experimental facility for determination of cavitational processes in the npp pipelines
DOI:
https://doi.org/10.15276/opu.1.60.2020.07Keywords:
cavitation, throttle, nozzle, vibration, experimental facility, NPP, ANSYS, CFXAbstract
The obtained experience during operating thermal and nuclear power plants has shown that the vibrations are one of the main causes of the cracks occurrence in the pipelines and elements of thermal-mechanical equipment. The large pressure drops that are accompanied by the appearance of non-stationary processes can occur at the places of throttles and valves installation. These processes are associated with the static and the total pressure pulsations in the system. The paper analyzes the international and domestic experience in the cavitation processes research, the nature of their formation, as well as methods of the registration. The report presents the design of the experimental facility that was developed for the studying of the cavitation processes in the NPP pipelines. Moreover, the paper was augmented by the description of the main design features of the installation components. The experimental stand is designed to study the processes that lead to the appearance of vibrations in the NPP pipelines at the places of the throttle installation. The installation is a closed circulation loop that filled by water. It should be noted that the selected arrangement of the main stand’s equipment allows changing the distance between the throttles, as well as their quantity. In order to ensure the occurring of the continuous cavitation process in the experimental facility, the mathematical model of the experimental stand was developed in advance. The results of the performed simulations have made it possible to select the necessary equipment according to the design's characteristics. The previous detailed analysis of non-stationary and stationary processes occurring at the locations of throttles was carried out using the ANSYS software package. The CFX module was used as the tool for cavitation’s simulation. For this purpose, Rayleigh-Pleset cavitation model was implemented. At the same time, for the first stage of the cavitation’s calculation, the SST model of the turbulence was chosen, and for the second stage - LES WALE. The experimental results will allow us to develop methods to reduce the level of vibrations in the relevant NPP equipment elements and to validate high-performance computational fluid dynamics programs for the stationary and non-stationary processes’ analysis of two-phase flows in the pipelines with throttle nozzles.
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