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.
In the context of fluid transfer, the selection between axial flow pumps and mixed flow pumps is determined by the specific hydraulic requirements of the application, primarily the desired head and flow rate. Axial flow pumps are best suited for applications demanding high flow rates with a low head, as their design propels fluid parallel to the pump axis, maximizing volume transfer with minimal pressure increase. Conversely, mixed flow pumps represent a versatile hybrid, providing balanced performance of both moderate head and high flow. This makes them the optimal choice for tasks requiring a significant increase in pressure in addition to substantial fluid volume.
Several studies have addressed related phenomena: Fan Yang et al., examined the hydraulic stability and internal flow characteristics of a vertical submersible pump stations in both forward and reverse operating modes. Zhang et al.. explored the generation and evolution of tip leakage vortices in axial flow pumps, assessing the effects of gap width and the cavitation on vortex formation through experimental and numerical methods. Chen et al. utilized hybrid numerical techniques to study the structural vibration and noise generated by flow within axial-flow pumps, validating pressure fluctuations experimentally and identifying the blade-passing frequency as the dominant vibration frequency.
Vortex formation at pipe intakes is a critical concern affecting pumping station performance. Sabouki et al.. combined experimental and numerical approaches study vortex generation in water intake systems. Xiaohui Wang et al. used detached eddy simulation to analyze vortex evolution, demonstrating that vortices consistently form at the impeller inlet region and maintain stable size and location throughout operation.
Jie Gong et al. investigated the impact of cavitation and vortex dynamics on axial flow pump performance, showing that cavity growth at lower ambient pressures induces earlier vortex merging. Wang et al. examined the long-term effects of cavitation-induced vibrations, highlighting the increase in frequency amplitude with rising flow rates and the non-stationary behavior of vibration signals.
A substantial body of work further explores the impact of vortices on pump performance through both numerical and experimental methods. These studies reveal the ability to detect vortex-induced vibrations in real-time and inform open-design vortex pump impeller development.
Ramadhan Al-Obaidi applied CFD methodologies for qualitative and quantitative flow field analyses in mixed flow pumps, incorporating frequency domain pressure variation analysis under different operating conditions. Additionally,
investigations into hydrodynamic and vibratory characteristics of mixed flow pump system highlight strong correlations between vibration deformation, hydraulic forces, and impeller pressure distribution.
CFD studies utilizing the standard k-ε turbulence model and the ANSYS Fluent software provide insights into complex centrifugal and mixed-flow pump patterns, emphasizing the influence of impeller blade geometry on efficiency and noise production.
Fluid-induced instabilities, often manifesting as high amplitude sub-synchronous vibrations caused by vortices or whirl phenomenon, typically occur when pumps operate below their optimal efficiency point. These instabilities arise where shear layers exist between fundamental and circulating flows. Understanding these mechanisms aids in improving pump-turbine reliability and operational efficiency.
Vortex pump vibrations are primarily periodic or quasi-periodic, with Cavitation often introducing oscillatory frequency characteristics. Frequency spectrum analyses, often performed via FFT methods, are critical for identifying vibration modes, critical speed, and the influence of flow conditions on vibration levels to prevent pump failures.
Various cavitation detection techniques are reviewed in the literature, including vibration, pressure pulsation, and acoustic methods, each with unique strengths and limitations.
Model-based approaches analysing voltage and current signals detect torque oscillations linked to hydraulic instabilities, employing advanced neural network architectures for early fault detection. A CNN-LSTM-attention network and a dynamic detection threshold are used in this method to detect abnormal operating conditions and early damage.
This study addresses a significant gap knowledge regarding vibration thresholds capable of inducing resonance within water pumping stations. To remedy this shortcoming, the study focuses on characterizing vibrations caused by water vortices and pump component malfunctions. The problem of water vortices was addressed with a thorough approach. A comprehensive solution involving the construction of a specialized curtain wall inside the water channel. This novel strategy guarantees are enough to sustain peak performance that proposed and validated to effectively eliminate vortex formation, ensuring sustained peak performance through continuous root cause monitoring during station operation.