Energy loss dynamic decomposition analysis under different working conditions in centrifugal pump

Centrifugal pumps often experience deviations from their design conditions due to changes in pipeline system pressure, flow rate, and other factors, which can affect the pump's performance. If they do not operate under design conditions, it can lead to internal flow disturbances and a sharp decrease in efficiency. This paper proposes an energy loss dynamic decomposition method based on numerical simulations of a whole pipeline system model validated by experiments. The entropy production rate (EPR) of centrifugal pump under different working conditions is analyzed through dynamic mode decomposition, aiming to investigate the internal flow patterns and energy loss evolution under different working conditions. Results show that the EPR can be decomposed into time-averaged EPR and fluctuating EPR at various frequencies. Under the small flow rate condition, both time-averaged EPR and fluctuating EPR are relatively high, and the spatial distribution of entropy production is non-uniform. Under the large flow rate condition, time-averaged EPR is large due to friction and impact losses. The fluctuating EPR at design and the large flow rate conditions are similar, and the spatial non-uniformity of EPR is also similar. Furthermore, by reconstructing the low-frequency EPR, the locations of low-frequency EPR under the three working conditions are clarified. Low-frequency EPR mainly occurs under the small flow rate condition, caused by backflow near the impeller blade inlet and outlet. This study reveals the mechanisms of energy loss inside the impeller in centrifugal pump under different working conditions, providing theoretical support for expanding the operational range of centrifugal pump.