Unsteady Analysis of Molten Salt Pump Based on Dynamic Mode Decomposition

As the main heat storage medium in photothermal power station, binary molten salt undergoes thermal decomposition above ۴۵۰°C, generating gas that accumulates within molten salt pump flow passages and affects pump performance. This study investigates molten salt pumps using thermal decomposition experimental data. The Eulerian-Eulerian multiphase flow model is employed to solve flow field parameters in pump passages, while dynamic mode decomposition (DMD) conducts modal analysis on unsteady velocity fields. Results show DMD accurately captures core characteristics of gas-liquid two-phase flow. Under different thermal decomposition gas generation rates, liquid and gas phase velocity fields remain stable or slightly decaying. The Mode ۱ (frequency =۰) dominates the flow field as the fundamental mode. The increase of thermal decomposition gas generation rate leads to the formation of large-scale vortex and enhances turbulent fluctuations due to strengthened gas-liquid interactions, resulting in a decrease in the frequency of the third-order mode and an increase in the frequency of the fourth-order mode in the liquid-phase velocity field; in contrast, the gas phase velocity field is insensitive to changes in the thermal decomposition gas generation rate, with its flow frequencies primarily determined by the flow passage geometry and the periodic rotation of the impeller. Furthermore, the generation of thermal decomposition gas severely degrades pump performance. At ۱.۰Qd, the efficiency decreases significantly, with a maximum reduction of ۱۱.۱%; At ۰.۱۵Qd, the head decreases obviously by ۲۵%.

کلیدواژه ها:

Molten salt pump ، Dynamic Mode Decomposition ، Thermal decomposition reaction ، Gas-liquid two-phase flow ، Numerical simulation