During the operation of a Pelton turbine, the centerline of the nozzle jet may deviate from the bucket pitch circle due to the low installation and maintenance accuracy, which will reduce the operating efficiency and the stability of the turbine and even cause severe vibrations and damages. Based on the VOF (Volume of Fluid) two-phase flow model and the SST k-ω turbulence model, the flow characteristics of a Pelton turbine were simulated with the nozzle jet deviating from the bucket pitch circle. The pressure pulsation inside the bucket and the force distribution of the runner were obtained, the turbine oscillation and efficiency were measured before and after the jet deviation, and the effects of the radial and axial deviations on the stability and efficiency of the Pelton turbine were analyzed. The results show that both the radial and axial deviations of the jet cause a significant increase in the axial force and the pressure pulsation amplitude of the turbine; the radial and tangential forces on the runner are slightly reduced; the maximum axial force on the runner is increased by 4 times and 2 times, respectively, after the axial and radial deviations within the maximum value allowed by the industry standard; and the efficiency of the turbine is reduced by 0.4% and 0.3%, respectively. The maximum relative amplitude of pressure pulsation in the radial offset case appears in the center of the bucket blade, while the axial offset case causes uneven pressure distribution on both sides of the diverter blade, uneven force on the bucket blade of the runner, and fatigue damage. By comparing the operation of the runner under the two offset cases, we can find that the axial offset of the jet has a greater impact on the stability of the runner than the radial offset, and the unit is more prone to vibration, increasing the risk of the unit lifting.

A combined numerical and experimental method study was performed to detect the inner flow state for a type of centrifugal pump. It was found that the inlet attack angles of blades in an impeller have a great influence on the flow instabilities in a centrifugal pump. The mechanism of the rotating stall in the impeller channel was explained. Meanwhile, flow state identification with vibration (FSIV) was proposed to detect the flow instabilities in a centrifugal pump. The relationship between the external vibration and the inner flow state has been established by FSIV. The characteristics and mechanism of the vibration produced by the flow instabilities in a centrifugal pump were investigated. It was found that the hump, the rotating stall, the backflow, the occurrence of unstable flow, and the cavitation in the centrifugal pump can be effectively detected by applying the vibration signals, which helps to obtain safe and steady operating conditions for the system.

In order to investigate the mechanism and the characteristics of the noise induced by unstable flow in a centrifugal pump, the internal flow characteristics in the pump were numerically researched, and the acoustic pressure fluctuations at the pump inlet and outlet were experimentally investigated. Obvious corresponding relationships between the flow instabilities, the cavitation and the noise were established. It was found that the rotating stall, the backflow, the hump, the occurrence of unstable flow and the cavitation in such a centrifugal pump were effectively detected through the noise, which could help to provide fundamental information on flow instabilities and guarantee safe and steady operating conditions for the system. The recirculation and prewhirl regions in the pump upstream pipe, which were caused by the backflow and the rotation of the impeller, presented the circumferential movement with a spiral shape, causing apparent broadband fluctuations at low frequency band of the acoustic pressure. The backflow and rotating stall could also result in broadband fluctuations of the pump outlet noise, which was distributed from 100 Hz to 150 Hz. Meanwhile, the broadband fluctuations of the pump outlet acoustic pressure distributed in the low frequency range, which was produced by the occurrence of cavitation, moved to the lower frequency band as the flow rate increased. The enhanced broadband fluctuations of the pump inlet and outlet noise distributed from 1 kHz to 6 kHz were caused by the coupling between the cavitation-induced noise and the system-produced noise. The broadband fluctuations of the pump inlet noise distributed between 6 kHz and 9 kHz were regarded as the typical frequency band of cavitation in the centrifugal pump.

The erosion of the fixed guide vane of a hydraulic turbine by sandy water is influenced not only by flow velocity and mud concentration but also by the direction and speed of the sandy water over the surface. This study aims to investigate the erosive effect of sediment-laden water on a specific type of hydraulic turbine’s fixed guide vane, validate the efficacy of the discrete phase model (DPM) in simulating wear on the fixed guide vane, and identify the critical areas of wear on its surface. To achieve these objectives, the wear model and DPM model are employed to conduct numerical simulations on the fixed guide vane. Additionally, samples of sand are collected from the power station site, and laboratory tests are conducted on the hydraulic turbine’s flow passage components using actual sediment concentration and sand-to-water ratio to determine the sediment wear conditions. The numerical simulation results of the guide vane’s surface wear rate are compared with the experimental data to verify the wear condition of the fixed guide vane under its rated working condition. These findings serve as a reference for the later-stage design of erosion-resistant solid guide vanes for hydraulic turbines.

During the flood season, Francis turbines often operate under low-head and full-load conditions, frequently experiencing significant pressure pulsations, posing potential threats to the safe and stable operation of the units. However, the factors contributing to substantial pressure pulsations in Francis turbines are multifaceted. This paper focuses on a mixed-flow hydroelectric generating unit at a specific hydropower station. Field tests were conducted to investigate abnormal vibrations and hydraulic pressure pulsations under low-head and full-load conditions. Utilizing the Navier–Stokes equations and the RNG k-ε turbulence model, the unsteady flow field within the turbine under these conditions was calculated. The results indicate that the abnormal pressure pulsations detected in the bladeless zone between the wicket gates and the turbine inlet are due to operational points deviating from the normal operating range of the turbine. When water flows at a large inflow angle, striking the turbine blade heads, it leads to significant flow separation and vortex formation at the back of the blade inlet edges, causing severe vibrations in the hydroelectric generating unit. These findings provide a basis and assurance for the safe and stable operation of the power station.

To address the measurement accuracy challenges posed by the internal flow complexity in atypical circular bend pipes with short turning sections and without extended straight pipe segments, this study designed an experimental circular “S”-shaped bent pipe with a diameter of 0.4 m and a bending angle of 135°. Numerical analysis was used to determine the stable region for velocity distribution within the experimental segment. Furthermore, a novel evaluation method based on the coefficient of variation was proposed to accurately locate the optimal position for installing thermal mass flow meters on the test cross section. Additionally, a formula for calculating the pipeline flow rate based on velocity differences was derived. This formula considers pipeline flow as the dependent variable and uses the velocity at two points in the test cross section as the independent variable. Experimental validation on a primary standard test bench demonstrated that the flow rate calculated by this method had an error controlled within 0.625% compared to the standard flow rate, thus effectively verifying the method’s high accuracy and engineering applicability. This research provides a new testing methodology and practical basis for flow measurement in complex pipeline systems, offering significant guidance for research and applications in related fields.