Axial-flow turbopumps are widely used in applications such as water jet propulsion. As these systems become smaller and faster, cavitation within the pump has become a major concern, potentially causing noise, vibration, and cavitation erosion due to strong pressure pulses during bubble collapse. This study focuses on evaluating cavitation intensity in the tip clearance region of an axial-flow pump to better understand the associated impact forces. Experiments were conducted using a test loop with a 160 mm diameter impeller. Measurements included flow rate, rotational speed, suction pressure, and dissolved oxygen concentration. A sensor was installed near the tip clearance to record impulsive forces, and high-speed video was used to observe cavitation behavior. Tests were performed at a fixed cavitation number σ = 0.3 across various flow coefficients (0.06 ≤ Φ ≤ 0.126), and in some cases, different rotational speeds (1350–1800 rpm) were applied. Results showed that cavitation intensity increased sharply between Φ = 0.090 and 0.110, aligning with regions of unstable pump performance. Visualization confirmed that vortex formation, influenced by flow separation and bubble movement, contributed to the intensity rise. The intensity also increased exponentially with rotational speed, suggesting the importance of vortex dynamics beyond mere velocity effects.
Murakami et al. (Wed,) studied this question.