Sediment erosion in turbine materials is caused by various flow phenomena. The study of these phenomena can identify suitable measures to minimize their effect on the turbine. Various experimental test rigs have been developed alongside numerical analysis to study erosion and predict wear. In hydraulic turbines, erosion in Francis turbines is mostly seen at the guide vanes and runners, and in Pelton turbines, the needle and the bucket regions are the most vulnerable components. Prediction of wear due to erosion in various parts of the turbine is difficult, as wear depends on the properties of flow, base material, and sediment. Past studies have shown that the test rigs developed to investigate erosion have considered reducing the number of independent parameters to simplify the experiment. Erosion rates and wear patterns are predicted through both quantitative and qualitative methods. This article aims to conduct a systematic review of experimental setups and the results of those studies. This work is expected to be useful in understanding the vulnerable areas of erosion in hydraulic turbines and different mathematical relationships developed to quantify erosion, as well as to know the contemporary understanding in the sector of experimental investigation of sediment erosion.

A clearance gap (CG) between guide vanes (GVs) and facing plates exists at both ends of a Francis turbine and allows the opening angle to be adjusted for varying operating conditions. Leakage flow is induced through this gap due to the pressure difference between the two sides of the guide vanes. While some research works have used qualitative approaches to visualize and predict the strength of a leakage vortex (LV), this paper presents a method for quantifying vortices along a trajectory. In this paper, a prototype high-head Francis runner with specific speed of 85.4 is considered as a reference case. A systematic investigation across both space and time is carried out, i.e., analysis of the spatial temporal progression of LV for three operating conditions. While travelling from the CG to runner leading edge, LV evolution and trajectory data are observed and the values of vorticity and turbulent kinetic energy are calculated for the LV trajectory. Frequency spectrum analyses of pressure oscillations in the vaneless space, runner blade, and draft tube are also performed to observe the peak pressure pulsation and its harmonics. Unsteady fluctuations of the runner output torque are finally studied to identify the patterns and magnitudes of torque oscillations.

Water‐suspended sediments wear down hydro turbine components by erosion, reducing their lifetime. Nonetheless, even heavily sediment‐loaded rivers are a valuable renewable and clean energy resource. Forecasting sediment erosion and optimizing the hydraulic turbine design for extended durability by numerical flow simulations became imperative to operate the hydropower plant safely and economically in sediment‐laden environments. This strategy is challenged by the unknown model parameters, that is, the lack of reliable validation data. Therefore, in this study, a 2 kW Francis‐type model turbine is tested in a non‐recirculating sediment‐laden test facility. The Francis turbine runner and the guide vanes are coated with four different colors to visualize locations of surface degradation qualitatively due to erosion during operation in representative sediment concentrations. The turbine is tested at two different operating conditions OP₁ and OP₂ for visualizing the locations of erosion. For operating condition OP₁, with low rotational speed, erosion is primarily observed at the leading and trailing edge of the suction and pressure side, respectively. The Francis turbine runner is particularly eroded in the transition between the hub and the blades on the suction side towards the trailing edge. Meanwhile, for operating condition OP₂, with higher rotational speed, the trailing edge of the pressure side of the blade and the region of the shroud close to the trailing edge of the blades are found to be vulnerable to erosion. Test for the material erosion of the runner is conducted at OP₃ conditions with high sediment concentration over 45 h, reporting the weight loss in intervals of 15 h. It is observed that the cumulative erosion rate of the Francis runner made of brass material is 0.016 mg g⁻¹ h⁻¹ after 45 h of operation. Similarly, the percentage loss of the runner with respect to the hours of operation is calculated to be 0.0065%, 0.04%, and 0.07% for 15, 30, and 45 h of operation, respectively. This data set can also be useful for qualitative and quantitative validation of computational fluid dynamic simulations for erosion prediction.

Despite the initiation of the master plan, envisioned by the government of Nepal, complete electrification of rural Nepal still seems over ambitious for quite a long time. Thus Micro Hydropower Plants (MHP) can still be very effective for rural electrification. Decades of manufacturing of same type turbines have saturated the turbine manufacturing industries of Nepal, which demands for some new innovations and that could be the introduction of Francis turbine in Nepalese MHP. It’s undeniable that there are umpteen opportunities for the turbine manufacturers to manufacture and install the Francis turbines in Nepalese MHP. The feasibility studies performed by different institutions and the government policy strengthen the claim. In addition to that, data received from, NMHDA and a local turbine manufacturing industry suggest that there are abundant sites suitable for installation of Francis turbine. This paper illustrates the need of introducing the Francis turbine in Nepalese MHP and discusses about the opportunities available for the turbine manufacturers to enter into the market of Francis turbines for micro hydro and subsequently for larger hydropower projects in the near future. The challenges associated with the introduction of Francis turbine in MHP are highlighted.