Abstract
This study aims to clarify the causes of flow instabilities in low-solidity inducers. High-speed photography was utilized to observe the instability phenomena around a low-solidity inducer. Additionally, FFT (Fast Fourier Transform) analysis was conducted to classify the characteristics of the static pressure fluctuation at the suction side, discharge side, and near the inducer. Furthermore, CFD (Computational Fluid Dynamics) calculations were performed to investigate the internal flow around the inducer. As a result of this study, the instability phenomena were caused by the leak back flow at the inlet of the impeller. The pressure pulsations occurring in a pump with a low-solidity inducer is caused by cavitation formation and dissipation at the tailing edge of the inducer. This phenomenon is due to the leakage flow from the impeller, which alters the primary flow of the inducer, resulting in a backflow vortex at the tailing edge and subsequent cavitation. Cavitation will not occur at the tailing edge without the influence of the impeller leakage flow. The impact of the impeller leakage flow is intermittent, and the periodic phenomena lead to pressure pulsations.
