Some high-specific-speed centrifugal pumps exhibit instability in terms of hydraulic performance and cavitation characteristics, and there’s a lack of reliable numerical models to guide the optimization of cavitation instability. This paper, by conducting a study on mesh independence, analyzes the cavitation curves and cavitation counters for various mesh combinations in the numerical model, The findings indicate that the boundary layer grid not only influences the location of peak points but also the size of the peak. To achieve a stable NPSH peak position, the y+ at the blade leading edge of high-specific-speed centrifugal pumps needs to be controlled between 20–80. The turbulence model, evaporation coefficient, and condensation coefficient were simulated using the orthogonal experimental design method, analyzing the impact of these parameters on the NPSH peak. A visual high-speed photography test rig was established, and rotating cavitation and sheet cavitation is found at part-load. By comparing the cavitation and pressure counters with high-speed photography images, a numerical model was obtained that closely mirrors the experimental cavitation characteristics.

During operation, failures in a centrifugal pump’s rotary shaft seal—such as wear, deformation, or thermal cracking—can adversely affect system performance. This study utilizes both theoretical and experimental methods to investigate the vibration characteristics of centrifugal pumps under different rotary-shaft-seal conditions. Vibration signals are collected and processed using empirical mode decomposition (EMD) and autoregressive (AR) modeling to generate an EMD-AR spectrum. The results show that rotary-shaft-seal failure leads to decreases in both the head and efficiency of the centrifugal pump. For improved operation stability, centrifugal pumps should operate at or slightly above their design flow rates (Q_d), while avoiding low-flow conditions. Furthermore, the amplitude of the EMD-AR spectrum increases progressively as rotary-shaft-seal degradation worsens. Therefore, the EMD-AR spectrum provides a reliable diagnostic indicator for detecting rotary-shaft-seal damage.

In order to study the influence of impeller structural parameters on the hydraulic performance and casting moulding of spiral centrifugal pumps, this paper selects a double vane spiral centrifugal pump with a specific rotation number of 170 as the research object. The Plackett–Burman experimental design is used to screen the influencing factors, and the results show that the vane thickness and the impeller outlet width are the significant influencing factors. Based on this result, five different scenarios were set for these two key parameters, numerical calculations were carried out using numerical simulation software for each of the five flow ratio cases, and casting simulations were carried out for the model of each scenario using AnyCasting6.0 to analyze the influence of these two factors on the hydraulic performance and casting forming of the spiral centrifugal pump. It was found that in terms of vane thickness, a moderate increase in vane thickness improved the hydraulic performance at small flow rates, but an excessive increase at large flow rates led to a decrease in efficiency and an increase in the probability of casting defects. In terms of impeller outlet width, increasing the outlet width caused the design point to be shifted, leading to a decrease in efficiency at small flow rates, but an increase in efficiency when the design flow rate was higher. At the same time, increasing the outlet width makes casting defects more likely to occur at the blade and back cover joint than on the blade surface. The study in this paper clarifies the significant effects of these two parameters on the performance and casting quality of spiral centrifugal pumps, and provides guidance for the optimal design of spiral centrifugal pumps.

The conventional 3% head-drop criterion (NPSH3%) only registers cavitation once macroscopic hydraulic performance has already deteriorated, leaving its earlier development largely invisible. We address this gap with an acoustic-fingerprint diagnostic framework, applied here to a centrifugal fire pump fitted with a baseline impeller (Imp A) and a cavitation-optimized impeller (Imp B): synchronized contact-acoustic and hydraulic-performance tests were performed while stepping down the available net positive suction head (NPSHa) at four flow rates (146, 163, 169 and 212 m³/h), complemented by ANSYS CFX simulations of the internal vapour-phase distribution. In place of a single frequency line or the overall sound pressure level, we define a continuous frequency-band integral I and its NPSHa-normalized growth rate KI. Across both impellers and all four flow rates, 1000-2500 Hz consistently shows a coherent spectral rise, peak migration and peak-cluster reorganization, identifying it as the principal cavitation-sensitive band; its accelerated-growth interval coincides with, and at several conditions precedes, the CFD-predicted expansion of blade-surface vapour fraction. The framework thus provides earlier, more sensitive state information than the NPSH3% criterion, though its generality across pump types and measurement chains remains to be verified.

The internal flow characteristics of a gas-liquid wall-attachment fluidic component in the small-offset-ratio regime were investigated using particle image velocimetry (PIV), with D/b = 0.2. A stable wall-attached jet and an upstream recirculation region were observed at flow rates of 3 to 5 m ³ /h. The influence of flow rate on the internal flow structure was analyzed, and a method for determining the wall-attachment point was proposed. To further understand the flow behavior, numerical simulations were performed using different turbulence and two-phase flow models. The results indicate that the SST turbulence model combined with a free-surface two-phase flow model can accurately reproduce the wall-attachment phenomenon and the associated pressure difference in gas-liquid flow. Based on the PIV measurements, a numerical model for the two-phase flow in the investigated small-offset-ratio fluidic component at D/b = 0.2 was established. Validation against experimental data shows that the model predicts the attachment offset distance within 5%. The proposed numerical approach provides a basis for predicting the main flow characteristics and wall-attachment behavior and for conducting subsequent parametric analyses of the investigated configuration.

The vertical inline pump, a single-stage centrifugal pump with a bent elbow inlet, is widely used in marine engineering. The unique water inlet passage combined with uneven inflow at the impeller inlet tends to form an inlet vortex and secondary flow area, which reduces performance and causes vibration. To predict the performance of the elbow inline pump, this study uses spline curve fitting for the centerline and cross-sectional shape of the elbow passage. With four elbow inlet variables from experimental design as the input layer and targeting efficiency under pump operating conditions, a pump performance prediction model based on an improved sand cat swarm optimization algorithm combined with a BP neural network (MSCSO-BP) is proposed. Six test functions are used to effectively test the improved sand cat swarm optimization algorithm. The results show that compared to the unimproved algorithm, the improved algorithm has significantly faster convergence speed, shorter parameter optimization time, and higher accuracy. For more demanding multidimensional test functions, the improved optimization algorithm can more accurately find the optimal solution, enhancing the prediction accuracy and generalization ability of inline pump performance. This provides a more effective engineering solution for the design and optimization of inline pumps.