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.

The ventilation systems in nuclear power plants, hydropower plants, and other large-scale projects involve the transportation of fluids through large-scale pipelines. To achieve a more stable flow velocity distribution, the fluid needs to pass through a straight pipe section of sufficient length upon entering the pipe. Typically, this straight pipe section should be at least 15 times the inner diameter of the pipe. However, for large-diameter irregular square pipes with a diameter exceeding 1m, where the curved section is short and there are no long straight pipe sections before and after it, the flow field inside the pipe becomes complex, requiring accurate measurement of the flow rate.In this regard, a numerical simulation analysis is conducted to address this challenge. A mean velocity evaluation method based on the coefficient of variation is proposed. This method identifies multiple points within the pipe that best represent the average flow velocity, determining the insertion depth of sensors and the weight coefficients of these multiple measuring points. A calculation formula is derived, utilizing the cross-sectional average velocity as a function with the velocity values at multiple points in the flow field as independent variables. To validate the accuracy of the proposed method, flow measurement experiments are performed on a wind tunnel test bench. The calculated values obtained from the derived formula through numerical analysis are compared with the experimental results. The relative error within the full range is found to be less than 0.54%, confirming the accuracy of the formula. The research findings present a novel measurement method for airflow in large-diameter irregular square pipes and offer valuable practical insights for engineering applications.