This study evaluates the frequency characteristics of pressure fluctuations in large-scale tubular pumps under optimal operating conditions. Unlike hydraulic models, prototype systems are significantly affected by gravity-induced disturbances due to increased geometric scale, disrupting axial symmetry and altering pressure fluctuations, which challenge stable operation.
This study references a hydraulic model and employs a combination of theoretical analysis and numerical simulation methods, focusing on the optimal pump operating conditions. Emphasis is placed on the impact of gravity-induced asymmetry, and a newly derived pressure fluctuation equation is introduced to analyze the phenomenon comprehensively.
A new phenomenon, frequency transfer of pressure fluctuations, is identified in the prototype, where the primary frequency shifts from the blade passing frequency to the shaft rotating frequency. The newly derived pressure fluctuation equation reveals that waveform characteristics are determined by the energy source term, highlighting the impeller's key role in this transfer. An energy allocation imbalance among blade passages causes periodic excitation effects, which are the direct trigger of frequency transfer.
This study reveals the frequency transfer phenomenon, driven by gravity-induced forced vibration, which increases the risk of operational instability. As this effect is difficult to replicate in hydraulic models, the findings highlight its critical role in technical evaluations and provide key insights for designing stable large hydraulic systems.
