To advance measurement methodologies for rotor health monitoring in pumped storage systems, this study proposes a novel non-invasive measurement framework integrating Motor Current Signature Analysis (MCSA) with hybrid deep learning. This method quantifies energy entropy shifts by employing Cyclic Autocorrelation Function (CAF) and Empirical Mode Decomposition (EMD), thereby addressing key metrological challenges including signal noise suppression and uncertainty propagation. Principal Component Analysis (PCA) is rigorously applied to reduce feature dimensionality while preserving measurement integrity. A novel SCSO-CNN-BiLSTM-Attention model is proposed, combining CNN’s spatial feature extraction, BiLSTM’s temporal dependency modeling, and attention-based critical weighting, optimized via Sand Cat Swarm Optimization (SCSO) for hyperparameter tuning with traceable uncertainty budgets. Validated on seven fault conditions, the model achieves 95.24% testing accuracy, outperforming traditional methods in both metrological robustness and computational efficiency. Key innovations include IMF1’s high-frequency sensitivity and IMF4’s low-frequency discriminability. T-SNE visualization confirms enhanced clustering through integrated RMS and IMF entropy features. Despite residual errors in cavitation-coupled faults, the framework demonstrates robust generalizability and real-time potential. This work provides a physics-informed AI solution for centrifugal pump health monitoring, balancing diagnostic precision with computational efficiency for industrial deployment.

This study presents a cavitation optimization framework combining feature selection with a Random Forest model to address performance degradation by cavitation in centrifugal pumps. A single-stage centrifugal pump with a specific speed of 36.77 is selected as the research object. Entropy production by cavitation (EPC) is introduced as the optimization objective to represent cavitation performance, effectively replacing the computationally intensive critical net positive suction head (NPSH3%) and thereby improving optimization efficiency. Furthermore, to address the dual challenges posed by redundant weakly correlated variables—namely, the inflation of optimization space dimensionality and the degradation of surrogate model accuracy—a feature selection method was implemented to identify significant influential parameters for use as optimization variables. Four surrogate models—Decision Tree (DT), Back Propagation Neural Network (BPNN), Extreme Gradient Boosting (XGBoost), and Random Forest (RF)—were selected to assess the effectiveness of feature selection. Through the feature selection approach, the Adjusted R2 coefficient of these surrogate models achieved a maximum improvement of 49.15%. Among the surrogate models, the Random Forest model demonstrates superior fitting performance, achieving Adjusted R2 coefficient of 0.93 for head and 0.94 for EPC. Final optimization using the non-dominated sorting genetic algorithm (NSGA-II) yields a 2.80% head increase, 3.89% NPSH3% reduction and 2.54% improvement in efficiency. The optimized impeller exhibits more uniform pressure distribution, reduced vapor volume, and decreased EPC, indicating mitigated cavitation intensity. The weakened cavitation intensity improves local entropy production distribution in wake regions, ultimately enhancing energy conversion efficiency.

Unsteady flow phenomena, especially in the blade tip region, play a critical role in the energy loss and performance degradation of axial-flow pumps operating as turbines. In this study, turbulence-related energy loss mechanisms in the axial-flow pump operating as turbine are systematically investigated using numerical simulations. Entropy production theory combined with the energy balance equation is employed to quantify the contributions of different energy loss terms. The results show that turbulence-related mechanisms dominate the energy loss in most components of the AFPAT, where the turbulent kinetic energy diffusion term and the turbulence production term together account for more than 60% of the overall dissipation. In contrast, the inlet section exhibits relatively weak turbulence activity and is mainly influenced by wall-related losses. High-loss regions are found to be strongly associated with complex vortex structures in the blade tip clearance. Timeresolved analysis further reveals a pronounced phase-dependent modulation of turbulence-related energy loss within each blade-passing cycle. To elucidate the underlying dynamic mechanisms, dynamic mode decomposition is applied to the Reynolds shear stress field. A low-frequency mode synchronized with the shaft rotation (2.09 Hz) is identified as the dominant energy-modulating mode, exhibiting a strong temporal correlation coefficient of 0.96 with the energy loss evolution. These findings deepen the understanding of unsteady turbulenceinduced energy losses in axial-flow pumps operating as turbines and provide a theoretical basis for blade tip clearance optimization and stable low-head energy recovery.

Vortex beams carrying orbital angular momentum (OAM) have attracted growing attention across fields, including optics and acoustics, for potential applications in particle manipulation and high-speed communication. Intracavity generation of OAM beams, such as OAM lasers, efficiently produces high-power, high-beam-quality vortices. This scheme, however, remains rarely explored in acoustics. Here, we propose and demonstrate an acoustic intracavity OAM generation mechanism with tunable topological charges via a single nonreciprocal nonlinear boundary in a compact resonator ring. In the linear regime, the boundary creates non-Hermitian complex effective magnetic fields piercing the ring, leading to a non-Hermitian Zeeman-like effect that splits clockwise and counterclockwise eigenmodes. Upon incorporation of nonlinearity to the boundary, all resonators are mutually locked, producing a single-mode self-oscillatory OAM radiation exhibiting hysteresis and bistability. Moreover, the topological charge is tunable by manipulating the boundary. Our work reveals intriguing physics related to nonlinear, non-Hermitian boundaries and offers potentials in the next generation of acoustic self-oscillatory OAM sources, switchers, and memory devices.

A piezoelectric cantilever-driven pneumatic servo pilot valve involves confined slit throttling, compressible jet expansion, shear layer instability, and pressure-induced structural deformation. These coupled mechanisms remain insufficiently understood, especially under different outlet back pressures. In this study, a three-dimensional fluid–structure interaction model was developed to investigate the flow regime, flow losses, and passive structural response of a nozzle–flapper pneumatic pilot valve under six operating conditions, combining three opening conditions and two outlet back pressures. The results show that outlet back pressure governs the flow regime. Under low back pressure, the pressure ratio far exceeds the critical pressure ratio of air, the slit chokes, and supersonic expansion develops with a maximum Mach number of 2.68, whereas under high back pressure the flow remains subsonic and incompressible. A key finding is the supersonic jet-induced negative pressure attraction effect under low back pressure. The choked slit flow forms a high-speed wall-attached jet along the lower surface of the piezoelectric cantilever. The combined effect of local supersonic expansion and wall-jet acceleration reduces the lower surface pressure below the upper surface pressure, causing the free end to bend toward the nozzle. Under high back pressure, this attraction mechanism disappears, and the distributed high pressure on the lower surface pushes the cantilever away from the nozzle. The energy loss analysis shows that the total flow loss under low back pressure is more than 300 times that under high back pressure, with the dominant loss region localized in the wall jet and downstream shear layer. These results reveal the pressure ratio controlled flow regime transition, supersonic jet-induced attraction mechanism, and localized irreversible loss structure in piezoelectric pneumatic pilot valves.

【Background】Data acquisition and numerical simulation are widely used for monitoring and evaluating pump performance, but they are often disconnected in practical application. This paper presents a digital twin platform for pumps to bridge this gap, in which machine learning, computational fluid dynamics (CFD), and modal decomposition techniques are applied in an integrated manner to represent high-dimensional flow fields using low-dimensional representations, thereby improving computational efficiency.【Method】The digital twin platform was developed based on LabVIEW and Python, consisting of four modules: data acquisition, numerical simulation, internal flow analysis, and feedback control. It collects boundary-condition data from sensors at regular temporal intervals and automatically feeds them into the simulation software for real-time computation. The platform also provides a graphical user interface to visualize internal flow fields, enabling feedback control and optimization of pump operation and maintenance. Compared with conventional monitoring systems, the platform supports real-time monitoring, efficient operation, and active regulation, while reducing maintenance costs and providing capabilities for prediction, early warning, and preventive control. As a demonstration example, the impeller was selected for transient flow simulation, in which proper orthogonal decomposition (POD) was applied to perform modal decomposition of pressure flow fields, evaluate reconstruction accuracy, and identify dominant frequencies of different modes.【Result】The pump digital twin platform was successfully applied to a pump test rig, enabling automated data acquisition and simulation. Modal decomposition results showed that the first five modes captured more than 70% of the total flow field energy, each exhibiting distinct error characteristics. Compared with high-flow conditions, low-flow conditions exhibited greater instability in the internal flow, due to flow separation in the mid-region of the impeller passage and rotor-stator interaction near the outlet. Under all operating conditions, the dominant frequencies of the first and second modes corresponded to the shaft frequency of 48.33 Hz, while high-order modes were associated with integer multiples of this frequency, likely resulting from asymmetric flow structures within the impeller.【Conclusion】The developed digital twin platform effectively integrates real-time operational data with numerical simulation. It overcomes the disconnection between physical operation and computational analysis, and significantly improves the intelligence and operational efficiency of pump systems.

Off-design operation reorganizes centrifugal-pump pressure pulsations through interaction between the rotating impeller discharge and the stationary volute. To clarify how the non-uniform impeller-outlet pressure field is concentrated and modulated in the volute, unsteady computational fluid dynamics was performed at 0.8Qd, 1.0Qd, and 1.2Qd. Fast Fourier transform, proper orthogonal decomposition (POD), variational mode decomposition, sample entropy, permutation entropy, and Lempel–Ziv complexity were combined to characterize the frequency content, spatial organization, temporal scales, and complexity of the pressure response. The 1.2Qd condition produced the strongest pulsations. The impeller response was dominated by the shaft frequency fr = 29.17 Hz and its low-order harmonics, whereas the volute response was governed by the blade passing frequency fimp = 175 Hz and its harmonics. The first four POD modes captured 91% and 90% of the fluctuating-pressure energy in the impeller and volute, respectively. The impeller modes were spatially distributed and phase shifted, whereas the volute modes were localized near the tongue and impeller outlet. The dominant impeller intrinsic mode functions retained 96.2% and 96.5% of the decomposed energy and remained close to the shaft-frequency scale; the dominant volute components exceeded 85% and clustered near fimp and 2fimp. Complexity analysis revealed an ordered low-frequency backbone with low-energy high-frequency complexity in the impeller, but stronger complexity across the blade passing frequency, its harmonics, and higher-frequency scales in the volute. The volute tongue concentrates and modulates the non-uniform impeller-outlet pressure field in a region-dependent multiscale response.

As the core energy-driven general machinery, pumps play an irreplaceable role in safeguarding national economic development and national defense security. However, the structural contradiction between the high energy consumption of traditional pump systems and the global “Dual Carbon” goals has become increasingly prominent. With the evolution of digital transformation and the continuous elevation of industrial internet security standards, the pump maintenance paradigm has undergone a profound shift from reactive responses to proactive, forward-looking interventions. To facilitate this transition, Digital Twin (DT) technology provides a system-level informatics solution by constructing virtual mirrors of physical entities. This paper aims to provide a comprehensive review of the lifecycle operation and maintenance of pumps, focusing specifically on how cutting-edge data perception and twin model frameworks serve as imperative elements to overcome bottlenecks in industrial deployment. Comprehensive analysis indicates that the interdisciplinary integration of multisource data fusion and non-intrusive reduced-order modeling synergistically improves real-time responsiveness while preserving the physical fidelity of fluid-dynamics knowledge. Furthermore, by leveraging the latest data mining and physical mechanism fusion technologies, this paper constructs a diversified paradigm for the “Four-Pre” functions, including pre-forecasting, pre-warning, pre-simulation, and pre-planning, which provides a critical reference framework for the architectural design and engineering application of subsequent industrial-grade pump DT. To further advance this paradigm, the deep coupling of real-time perception with reduced-order models and the construction of system-level dynamic architectures should be identified as future directions to empower the real-time, system-wide coordination of on-site industrial operations.

Hydrogen circulating pump is an important equipment of hydrogen fuel cell system, which can recover unreacted hydrogen and improve system efficiency. Roots pump is considered as one of the important forms of hydrogen circulating pump. Firstly, the model is ascertained through air experiments, then the impact of pressure ratio on different media is revealed in this paper. It is significant to recognize that when the pressure ratio rises from 1.1 to 1.2, the volumetric efficiency of air decreases by 7 %, while that of hydrogen decreases by 29 %. Additionally, it is revealed that the new profile area utilization coefficient is increased by 6 %. More importantly, the diametercenter distance ratio of the newly designed rotor profile can reach above 1.55. Compared with the traditional three-lobe rotor, the new rotor profile could be a better substitute without any changes to the original shell and other components. In addition, the pressure pulsation amplitude of the new rotor can be reduced by up to 66 % at the outlet pipeline monitoring point. The steady section of the windward side increases by about 20 degrees. The outcome of this research could serve as a guide for structure optimization and product replacement of hydrogen circulating pump.

Non-Hermitian band topology can give rise to phenomena with no counterparts in Hermitian systems. A well-known example is the non-Hermitian skin effect (NHSE), where Bloch eigenstates localize at a boundary, induced by a nontrivial spectrum winding number. In contrast, recent studies on lossy non-Hermitian lattices have uncovered an unexpected boundary-localized loss probability-a phenomenon that requires not only non-Hermitian band topology but also the closure of the imaginary (dissipative) gap. Here, we demonstrate the non-Hermitian edge burst in a classical-wave metamaterial: a lossy nonreciprocal acoustic crystal. We show that, when the imaginary gap remains closed, edge bursts can occur at the right boundary, left boundary, or both boundaries simultaneously, all under the same non-Hermitian band topology; the latter scenario is known as a bipolar edge burst. The occurrence of each scenario depends on the number and location of the imaginary gap closure points in the eigenenergy spectra. These findings generalize the concept of edge burst from quantum to classical wave systems, establish it as an intrinsic material property, and enrich the physics of the complex interplay between non-Hermitian band topology and other physical properties in non-Hermitian systems.

Global energy consumption is rising, making energy efficiency a global priority. Multistage centrifugal pumps, key components in thermal power systems, consume significant energy, so improving their efficiency is essential. This study integrates an intelligent optimization algorithm with computational fluid dynamics (CFD) for a multistage centrifugal pump operating at 5500 r/min. A baffle design within the interstage passage is proposed, along with a method for controlling the baffle shape. This design improves the internal flow regime while increasing both head and efficiency. The baffle shape parameters are selected as optimization variables, with head and efficiency as objectives. A backpropagation neural network (BPNN) combined with the NSGA-II algorithm is used to optimize the baffle design. Based on simulation results and entropy production theory, the flow field and entropy losses are visualized. Results show that the BPNN effectively predicts head and efficiency. The optimal design yields a thinner baffle with a larger cross-sectional area. Compared with the original model, the optimal model increases head by 9.7% and efficiency by 3.5%. This study provides strong support for BPNN applications in fluid machinery and offers a reference for optimizing interstage passages in multistage centrifugal pumps.

In loss-of-coolant accident(LOCA), the axial flow reactor coolant pump is likely to be in a vapor-liquid two-phase flow at low flow rates, which poses a threat to the safe operation of the reactors.Based on this special working condition, this paper studies the influence of vapor fraction on the flow patterns of axial flow reactor coolant pump(RCP) at low flow rates, and uses wavelet analysis and other methods to reveal the pressure pulsation characteristics in RCP with different vapor fractions.The results show that the performance of the RCP and the change in the flow pattern in the RCP are closely related to the vapor fraction.As the vapor fraction increases, the performance of the pump near the rated point shows a downward trend, and the hump range in the low flow rate area shows a downward trend first and rising trend.In the impeller, the flow channel is mainly blocked in the form of a vortex under pure liquid and low vapor fraction conditions, and the flow channel is mainly blocked in the form of a backflow under high vapor fraction conditions.In addition, the pressure pulsation amplitude and high pressure pulsation areas of each flow-passing components change with the different vapor fractions, but the main frequency is almost independent of the vapor fraction.

A pipeline-free dishwasher pump integrates the double-tongue volute flow channel with pipeline spraying to achieve the advantages of anti-fouling, water/energy conservation, and short cleaning cycles. However, its hydraulic efficiency is lower than traditional pumps due to unclarified unsteady flow mechanisms. In this paper, numerical calculations are performed to research the hydrodynamics of the double-tongue volute under different diameter ratios (d = 0.90, 0.94, and 0.98) of blade outlet diameter and the volute base circle diameter to investigate the unsteady evolution characteristics and the energy loss in the novel dishwasher pump. The numerical calculation results are validated against a PIV experiment. The effect of the diameter ratio on vortex structure, pressure pulsation and energy performance is employed. The vortical regions correspond to areas with high entropy generation coefficients, identifying them as primary contributors to energy dissipation. The diameter ratio influences the amplitude of pressure fluctuations, especially in the tongue region. Results from proper orthogonal decomposition (POD) analysis reveal that large-scale structures within the double-tongue volute are associated with the shaft frequency. Moreover, it is observed that the energy decay rate is linked to the frequency associated with the POD mode. Comprehensive analysis of hydrodynamics, entropy production, and POD results demonstrates that the optimal diameter ratio range is 0.92 < d < 0.94. Within this range, the pump achieves a balance between head (>= 2.1 m) and efficiency (>= 40%), with 64% weaker pressure pulsation amplitude than d = 0.98 and 12% higher energy proportion of large-scale vortices than d = 0.98.

Pump as turbine (PAT) is a key technology for industrial residual pressure-energy recovery. However, achieving satisfactory hydraulic performance under both pump and turbine operating modes remains challenging, primarily because the internal flow structure and energy conversion mechanism are altered during reverse operation, and the influence of geometric parameters on dual-mode performance remains unclear. In this study, the entropy production theory and vorticity transport analysis were combined to investigate the effects of geometric parameters on dual-mode hydraulic performance and flow mechanisms, elucidating the intrinsic relationship between vorticity generation and energy dissipation. The results indicate that the influence of blade geometric parameters on dual-mode performance is markedly asymmetric, which can be attributed to the reversal of the flow direction leading to changes in the velocity triangles. The blade wrap angle exhibits a strong positive correlation with efficiency in pump mode, whereas a negative correlation is observed in turbine mode. In pump mode, turbulent entropy production dominates, whereas wall entropy production increases in turbine mode. Vorticity transport analysis reveals that the Coriolis force term and the relative vorticity stretching term are the dominant mechanisms of vorticity generation, and their spatial distribution is consistent with that of the regions of high entropy production, indicating a strong correlation between vortex dynamics and irreversible energy dissipation. Velocity triangle analysis further demonstrates that the attack angle is the key parameter determining impact losses and separation losses. The parameter coordination design strategy proposed in this study provides a theoretical basis and quantitative reference for achieving efficient dual-mode operation of PAT.

Bloch wavefunctions in crystals experience localization within the bulk when disorder is introduced, a phenomenon commonly known as Anderson localization. This effect is considered universal, being applicable to all types of waves, quantum or classical. However, the interaction between disorder and topology-a concept that has profoundly transformed many branches of physics-necessitates revisiting the original Anderson localization picture. For instance, in the recently discovered topological Anderson insulator, the introduction of disorder induces topological boundary states that can resist localization due to protection from line-gap topology. While line-gap topology applies to both Hermitian and non-Hermitian systems, non-Hermitian systems uniquely exhibit point-gap topology, which has no Hermitian counterparts and leads to the non-Hermitian skin effect. Here, we experimentally demonstrate disorder-induced point-gap topology in a non-Hermitian acoustic crystal. This crystal, with non-Hermitian disorder in nearest-neighbor couplings, exhibits the non-Hermitian skin effect, where all eigenstates localize at a boundary. Interestingly, the boundary where localization occurs-either the left or right-depends on the strength of the disorder. As the disorder strength increases, the direction of boundary localization can be reversed. Additionally, we observe a "bipolar" skin effect, where boundary localization occurs at both the left and right boundaries when disorder is introduced in next-nearest-neighbor couplings. These findings experimentally reveal a non-Hermitian mechanism of disorder-induced localization that goes beyond the conventional framework of Anderson localization.

Given the burgeoning renewables-based microgrids, it is crucial for a stable power supply to enable more flexible micro-pumped hydro storage by the reversible mixed-flow pump (RMFP) with a broad high-efficiency zone (HEZ). Variable-speed operation is the most effective method to regulate operating conditions for scenarios of the RMFP without the guide vane. To reveal the effect of variable-speed regulation on the HEZ, we test the energy characteristics of RMFP at four speeds based on a bidirectional hydraulic test bench. The experiment shows that the RMFP receives an HEZ that is expanded by 53.4 % in pump mode and 60.3 % in turbine mode by accelerating from 830 r/min to 980 r/min. Moreover, the transition process of the acceleration regulation under full load is simulated based on a validated CFD numerical scheme. It is indicated that the acceleration regulation not only improves the efficiency and hydraulic dissipation but also alleviates the flow instabilities. The peak-to-peak value and the amplitude of the dominant frequency of the pressure fluctuation in the runner can be reduced by up to 49.4 % and 46.2 %, respectively. This study highlights the broad high-efficiency zone and stable internal flow that variable-speed regulation contributes to the RMFP, aiming at enhancing the flexibility of micro-pumped hydro storage.

As the core equipment of PWR primary circuits, the reactor coolant pump (RCP) exhibits performance evaluation deviations due to property differences between high-temperature operation and room-temperature experimental conditions. Through full-flow-domain modeling integrated with entropy production theory and vortex dynamics-based multiscale analysis, the mechanism by which temperature variations affect flow losses in RCPs has been systematically elucidated. The study reveals that reduced dynamic viscosity under elevated temperatures diminishes the dominant role of velocity gradients in viscous dissipation. Entropy production concentration zones exhibit a strong correlation with high-speed shear flows. Vortex structure analysis identifies the hub-region counter-rotating vortex and inlet horseshoe vortex as primary contributors to energy losses in the impeller domain. The formation mechanism of high-intensity vorticity in the volute outlet section is directly attributed to the tongue-guide vane interference effect. Notably, the viscosity-dissipation suppression effect under high-temperature conditions significantly weakens local vortex structure generation intensity, resulting in a 0.51 % reduction in total system vorticity volume. Furthermore, the dominant low-frequency component at 0.33fn is confirmed to be vortex-induced, with its amplitude decreasing as temperature rises. These findings provide a theoretical foundation for optimizing flow fields and enhancing the hydraulic performance of RCPs under high-temperature operating conditions.

Pump stations play a vital role in various fields, whose impeller usually be adjusted to meet the specific demand. However, the variation of blade angles would incur instability in the internal flow of the pump, which increases the risk of vortex formation. Also, due to the limitation of high computational cost and the requirement for high accuracy in traditional simulation, pump stations face delayed monitoring and reduced operation and maintenance. To solve the issues above, this paper performs an analysis of the pressure and velocity of the internal flow for each blade and quantitatively assess the flow losses of each component using entropy generation theory. Furthermore, combined with proper orthogonal decomposition, which generates the basic modes and corresponding time coefficients, the prediction of corresponding coefficients has been evaluated based on recurrent neural network, which has been used in real pump station for fast flow field reconstruction. Results show that the proper orthogonal decomposition analysis identifies the first five modes capturing over 99% of the total kinetic energy, where Mode 1 correlates with large-scale flow structures. Flow reconstruction using the first 3 modes, whose time coefficients were processed and input into the model with fixed parameters, and the average root mean square error values for -2°, 0°, and 2° are 0.05, 0.067 and 0.033. In addition, compared with the traditional computational fluid dynamic, the method of prediction reduces the cost obviously while the result agrees well with the original.

To enhance the gas-liquid mixed transport performance of the first-stage centrifugal impeller of the multistage side-channel pump, a diagonal perforation oriented towards the exit is fabricated in the front shroud of the impeller. Based on the Euler-Euler non-homogeneous model and the SST k -ω turbulence model, the gas-liquid two-phase unsteady numerical simulation of the internal flow under various inlet gas volume fraction (IGVF) is conducted, the reliability of the simulation is verified through comparison with experiments. The results indicate that under the circumstances of high flowrate and high IGVF, the perforation design of the front shroud can increase the head of the centrifugal impeller by 4

As vapor is transported with the mainstream and undergoes intense flow interaction, irreversible energy dissipation occurs according to the cascade principle of energy transmission, particularly under overload flow conditions where the cavitation development rate is rapid. To address this issue, fully adjustable (FA) and half-adjustable (HA) advanced inlet guide vanes (AIGV) are designed to improve hydraulic performance under multiple operating conditions. Entropy production theory and cavitation flow identification methods were combined to compare their suppression mechanism against hydraulic dissipation. The primary findings are as follows: 1) The AIGV effectively improves the efficiency of the mixed flow pump within overload flow rates and enhances its cavitation resistance. Compared with FA-AIGV, the novel HA-AIGV demonstrates a more significant improvement in comprehensive hydraulic performance. 2) AIGV creates a positive incidence angle at the impeller inflow, which delays the initial cavitation inception and suppresses both streamwise and spanwise vapor propagation. Consequently, energy dissipation caused by momentum vapor-liquid exchange is reduced.