An experimental evaluation of vibration patterns arising from vortex flow in mixed flow pumps a case study in Upper...

Mixed flow pumps, characterized by high flow rate and moderate head, are the preferred choice for pumping station installations. Nevertheless, the development of inlet vortices significantly impairs the performance of mixed-flow pumps, threatening operational stability and safety. This focuses on a large pumping station where unstable and fluctuating vibration levels were observed across four pumping units during extended operation. Over a continuous 6 h period, total vibration velocity levels were recorded at 2 h intervals. Both velocity and acceleration spectra were analyzed at all measurement sites to investigate the pronounced fluctuations in vibration. Computational fluid dynamics (CFD) simulations were employed as the primary method to realistically visualize the complex turbulent flows occurring in the pump intake under various operating conditions. The results showed that vibration magnitudes increased notably near the blade-passing frequency whenever a vortex was present. Furthermore, a vortex's presence was successfully recognized at measurement points due to sudden spikes in vibration intensity. The formation, pattern, and regularity of vortex flows were examined using numerical simulation to address this issue. Based on the numerical findings, recommendations for improving and modifying the pumping station inlet design were proposed. Experimental validation confirmed that constructing a curtain wall to reduce free vortices above and below the water surface is an effective and practical solution to mitigate vortex formation. Maximum vibration level reduced by about 73% after execution of the curtain wall to the pump intake. This research presents an innovative and effective solution to an actual problem occurring in a large pumping station. This solution is considered a scalable procedure which can be applied to any pumping station exposed to the problem of vortices.