Effects of blockage location in the impeller passages of a high-speed coolant pump on energy loss and unsteady flow characteristics

High-speed coolant pumps are core components of thermal management systems in new energy vehicles and data centers. Their operational stability directly determines system heat transfer efficiency and safety. Investigating the impact of impeller blockage is crucial to enhancing equipment reliability. However, the influence of blockage location within flow passages on unsteady flow and energy loss remains unclear. Using combined numerical simulations and experiments, this study analyzes how blockages at different locations on the impeller pressure surface affect the energy characteristics, internal flow, and pressure fluctuations of a high-speed coolant pump. Results show that inlet blockage has the most significant impact on hydraulic performance. Under high flow rates, impeller entropy production accounts for over 50% of the total loss. Mid-section blockage causes local flow acceleration and static pressure drops, raising upstream pressure fluctuations at the shaft frequency. However, this disturbance weakens downstream due to passage constraints. Outlet blockage severely disrupts outflow uniformity, creating a high-kinetic-energy distorted jet. This jet strongly impinges on the tongue, inducing flow separation and mixing losses that cause a sharp efficiency drop under high flow rates. Additionally, pressure fluctuation characteristics and rotor radial force vector distributions can effectively locate the flow distortion source.