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... With the widespread application of hydraulic energy and the development of water resource engineering, hydraulic machinery, as an indispensable component, plays a crucial role in the hydrodynamic environment [1]. Nonetheless, as a consequence of the substantial sediment content present in natural water, hydraulic machinery inevitably encounters a significant challenge in the form of sediment erosion during its operation [2]. This issue, prominent in the domain of hydraulic machinery, exerts an impact not only on the performance and longevity of mechanical components [3]. ...
Sediment erosion damage is one of the main causes of structural failure in reaction turbine units. To study the mechanism through which sediment erosion affects the water-guiding mechanism of a reaction turbine unit, this study obtained the average concentration and particle size of sediment during the flood season based on the statistics of the measured sediment data from the power station. Additionally, the characteristics of the solid–liquid two-phase flow of the diversion components of the reaction hydraulic turbine were numerically calculated. Based on the velocity triangle change in the guide apparatus and the flow similarity principle, a flow-around wear test device for the guide apparatus of the reaction turbine was designed. Furthermore, the similarity of the sand–water flow field between the guide apparatus of the prototype unit and the test device was compared and analyzed. The results demonstrated that the sand–water flow field of the diversion components of the prototype unit was axisymmetric and exhibited a potential flow distribution. Additionally, uniform sand–water flow occurred within the guide apparatus, with a small sand–water velocity gradient near the wall of the stay vanes (SV) and the guide vanes (GV). The maximum volume fraction of sediment particles was observed in the tailing area of the spiral casing, indicating an enrichment phenomenon of sediment particles. The velocity of the sediment particles on the surface of the guide vane in the single-channel sediment wear test device and prototype unit ranged from 6.2 to 7.8 m/s, and the velocity of the sediment particles on the surface of the stay vane ranged from 5.1 to 14.6 m/s, and the difference of the sediment particles’ velocity near the wall was 1 to 3 m/s. The trailing vorticity of the guide vane reached a maximum of 120 s−1. Consequently, the single-channel sediment erosion test device can unveil the sediment erosion mechanism of the guide apparatus of a reaction turbine.
... Suh predicted sediment erosion for different inlet solid-phase concentrations in a mixed-flow hydraulic turbine runner, and the results showed that the erosion location occurs mainly on the pressure side of the runner blades [8]. Neopane found that sediment wear is related to the sediment shape, concentration, particle size, and the turbine operating conditions, and that the wear rate can be reduced by operating the turbine at the optimum efficiency point [9]. Yasuyuki Nishi et al. studied the performance and flow field of a cross-flow turbine with a different number of blades and the results of the study reveal that the efficiency of an eight-bladed turbine is higher than a 24-bladed turbine [10]. ...
In order to study the internal flow state and wear law of a bulb cross-flow unit based on the particle non-uniform phase model in the Euler–Euler method, the solid-liquid two-phase flow condition of the hydraulic turbine under different solid-phase diameters, concentrations, and guide vane openings is calculated. The results show that (1) Under the same solid-phase physical parameters, the distribution of solid-phase concentration on the working surface of the blade is positively correlated with the opening degree of the guide vane, the concentration of the solid phase on the back of the blade is negatively correlated with the opening degree of the guide vane. (2) The addition of the solid phase changes the time-domain period of pressure pulsations at the rotor inlet and the tailpipe inlet under clear water conditions, and the tailpipe pressure pulsation coefficient decreases with increasing solid-phase concentration. The pressure pulsation coefficient increases with increasing solid-phase diameter and concentration at the inlet of the rotor. (3) Numerical simulation of the wear characteristics of cross-flow turbine by Finne’s wear model reveals that the two-phase flow condition with high concentration, large particle size and small openings has a more serious effect on turbine blade wear.
... Schematic of silt erosion mechanism[39]. ...
Francis turbine, a reaction type and medium head turbine is most widely used in hydropower plants to generate
electricity due to its wide range of operation. Cavitation erosion and silt erosion are hydraulic transient phenomena, which are the common problem associated with hydro turbines. The metallic surface gets damaged due
to high local stress caused by collapsing of the vapor bubble while silt erosion removes the material from turbine
surface due to the dynamic action of silt particles. Cavitation erosion depends on suction height, temperature,
and sigma factor while silt erosion depends on silt size, concentration, flow velocity, and impingement angle. The
investigations have been carried out by various researchers on cavitation and silt erosion in the hydro turbines
individually and combined. It is revealed that the combined effect of cavitation and silt erosion is more severe
than the individual effect. In coalesced effect, the cavitation mechanism may be inhibited or promoted by effect
of silt erosion. In this study, a comprehensive review has been carried out to evaluate the effect of cavitation
erosion, silt erosion, and combined erosion on the performance of Francis turbine. Due to combined effect,
various factors like surface properties, erosion parameters, and flow characteristics are responsible for efficiency
loss and material degradation. At present few studies are only marked on the combined effect in hydro turbines.
It is therefore required to carry the extensive work for understanding and develop the correlation between the
material erosion and performance loss by numerically and experimentally.
... Hydro-abrasive erosion has become a global operation and maintenance problem in hydropower plants. The hydro-abrasive erosion in hydraulic turbines is primarily due to the flow of suspended sediment into the water, which is subject to kinetic energy, gravity force, viscosity, friction, and centrifugal effects [2]. ...
... India alone faces a loss of 120-150 million $ US years because of erosion in hydro-turbines [5]. Several researchers [2,[6][7][8][9][10][11][12][13] identified and predicted the erosion in Francis turbine components by using experimental studies, analytical studies, case studies, and numerical modelling (CFD analysis) [14,15]. The flow situation in a Francis turbine is unusual, and the erosion rate is heavily influenced by the turbine's operation. ...
... The flow situation in a Francis turbine is unusual, and the erosion rate is heavily influenced by the turbine's operation. Because of the increased turbulence, operating at off-design speeds up erosion and increases the likelihood of secondary flows and vortices [2]. During full-load operations, the guide vanes and runner vanes are particularly vulnerable to erosion [16]. ...
Hydro-abrasive erosion creates problems for the safe and effective running of hydropower projects. This is of even greater concern in hilly regions. The huge losses in the revenue of the hydropower plant have become a burden on the hydropower project developers. These losses are mainly due to the reduced capacity of the generation of electricity units (kWh). The high amount of silt entering the plant, especially in the monsoon season causes heavy hydro-abrasive erosion in the turbine and other underwater components. The deterioration of underwater plant equipment due to this kind of erosion can also lead to a total shutdown of the hydropower plant. In the current scope of the study, efforts have been made to validate the existing erosion models for the Francis turbine with the operational hydropower plant and carry out the numerical erosion modelling in the Francis turbine to predict the turbine efficiency losses at maximum and part-load conditions. Various developed erosion models are analyzed for the study period of FY 2018–19 based on influencing parameters like silt concentration, silt size, hardness, and site-specific flow constant. The site chosen for this purpose was the MB-II hydropower plant, a 304 MW hydropower project having four generating units of Francis turbine located at the foot of the Himalayan hills in the Uttarkashi district of Uttarakhand, India. The calibration factor is calibrated for the MB-II hydropower plant using GRG Nonlinear algorithm using a multi-start solver.
... Sediment erosion of the hydropower turbine components is one of the critical factors influencing their operation and service life [14,15]. The problem is more pronounced in run-of-river schemes, requiring periodic maintenance and even stopping power production during the high sediment loading period [16]. ...
Guide vanes of Francis turbine are being severely eroded while working with sediment laden water. The vane shape is generally aerodynamic for directing the flow to runner vanes with the effective transformation of pressure energy to kinetic energy. Suspended particles result in erosion of the spanwise surfaces, and leading and trailing edge side of the guide vane. The eroded portions showed the formation of secondary flow and horseshoe vortex along with increased leakage flow on guide vane surfaces. Flow turbulence generated through the guide vanes increases the flow instability in the main flow and reduces the hydraulic and mechanical efficiency of the turbine. This review focuses on the impact of sediment particles on erosive wear of guide vanes of Francis turbine. The investigated flow field around different guide vane profiles have also been summarized along with an estimation of erosion through field study, laboratory test setup, and numerical study. The review also focuses on the post erosion problems, vulnerable locations, research gaps, and the possible solutions, for mitigating the erosion of the guide vanes.
... Water after leaving GV tries to escape through this gap before entering the runner blade inlet. Wear and tear of turbine material due to sediment flow is one of the major challenges for hydropower plants operating in Himalayan regions of Nepal [2,[6][7][8][9][10][11]. While past studies were limited to study the erosion at GV and runner blade of Francis turbine, erosion towards the hub and shroud region at circumferential locations were not examined at all. ...
Sediment induced erosion in exposed components of hydraulic turbines is a major issue in most of the sediment laden hydropower projects. Gradual removal of material can change the components profile which can lead to change in flow characteristics and compromise in the efficiency as well. Among several components in Francis turbine, this study focuses on the runner sidewall gaps to develop a numerical model for erosion prediction. A prototype high head Francis runner with specific speed of 85.4 rpm has been considered as the reference case. A simplified numerical model based on the concept of rotating disc apparatus (RDA) is conceptualized to make analogy with the gap available between runner blades and guide vanes (GVs). Fillet gaps are introduced in the model to emulate the gaps available between runner blade and GV for real case scenario. Four samples with 90° separation of each are mounted on the disc rotating at 750 rpm. Sediment size of 150 μm diameter with particle mass flow rate based on the maximum amount of sediment passing through the reference turbine is used. Numerical calculation is done in ANSYS® with Tabakoff erosion model. Results give an indication of critical zones in the gap region. Erosion pattern, rate density and vorticity are compared with the actual turbine.
... Despite several preventive measures being practiced, the problems of sediment erosion in turbine components have still been a challenge for operating run-off-rivers projects in the monsoon period. The rivers of the Himalayan regions consist of abundant quartz particles along with other hard minerals like feldspar, muscovite, biotite, hornblende, magnetite, etc [2][3][4]. Moreover, sometimes the sediment in these rivers can be so huge that having a properly designed flushing system and sediment settling basin may not be enough. ...
... The thickness of the blade was decreased from 80% span from the pressure side and the effect on the structural integrity was studied. The thickness was reduced by 1,4,8,16,18,21 and 34 mm in the first case. The effect of the erosion on its safety factor is given in Figure 8(a). ...
The geographical condition of Nepal has always challenged the hydropower plants in Nepal. The huge potential run-off rivers flowing through this terrain carry an immense amount of sediment. This sediment constitutes quartz particles with enough hardness, which corrodes the material of the hydraulic turbines and other components of the hydropower plant. The sediment erosion hindered the growth of hydropower plants as it significantly increased the maintenance cost and decreased the efficiency and life span of the plant itself. This paper takes this problem into account to investigate the structural integrity of one of the reference cases of eroded low head Francis turbine of Nepal by performing one-way FSI. CFD analysis was conducted on the single passage of the runner and structural analysis of the runner was conducted as well. For the structural integrity, the thickness of the blade at the trailing edge was decreased to 80 percent of its span. From the results of the structural integrity, the stresses imposed on the reference runner due to the erosion were observed to be within the allowable stress even in the extreme case condition.
... The transport of sediment particles along with clean water goes through series of abrasive and erosive wear while flowing through the turbine components. Continuous abrasion and erosion in turbine components not only deteriorate the performance of turbine but also enhances frequent repair and maintenance of power plant [5] [7]. Different kinds of turbines specified by the power plant location with available head and flow are designed and developed around the globe. ...
Sediment erosion in hydraulic turbines are severe in case of hydropower plants operating in Himalayan Rivers of Nepal. Francis turbine components are heavily eroded while hard particles as quartz flow along with water through the water conduit in power plant. In Francis turbines, the runner blades where significant portion of hydraulic energy converts in mechanical energy are heavily eroded. This is due to complexity in fluid flow while operated at different operating conditions with sediment contained water. Conventional design of Francis turbines has overlooked on the effects of sediment erosion while considering optimum efficiency at all operating conditions. This paper examines multi-objective optimization of a reference 92 kW model Francis runner for minimizing sediment erosion effects. The model turbine studied in this paper is a scale down model turbine of Jhimruk Hydropower Plant, Nepal that is severely affected by sediment erosion. It was found that sediment erosion was reduced significantly at part load, full load and best efficiency point with improvement in hydraulic performance for model turbine utilizing multi-objective optimization on runner blade design.
... El desgaste por erosión es la pérdida de material debida al impacto repetido de partículas sólidas sobre una superficie y causa importantes pérdidas económicas en diversas industrias como la del petróleo y el gas, el transporte hidráulico y los procesos químicos [47]. De acuerdo con varios autores [2] [48] existen cuatro mecanismos básicos que generan un desgaste hidro abrasivo, estos son: erosión abrasiva, fatiga, deformación plástica y fractura frágil. La erosión abrasiva es causada por partículas que golpean la superficie del material en ángulos de baja incidencia, causando un efecto de corte que remueve el material. ...
... Por otro lado, el autor [2], establece tres divisiones que engloban los factores que influyen en la erosión por hidro abrasión: ...
... : [ 2 ] : Los errores más cercanos a 0 son los del modelo K-ω SST y K-ε Realizable, modelos que se observó una mejor predicción de la erosión. ...
The present work evaluates the influence of the conventional RANS turbulence models, being the K- ε (standard and realizable) and K- ω (standard and SST) on the erosion by solid particles in a Francis type turbine. In this way, these two different models are compared to define which one has a better numerical prediction of the erosion and the solid-liquid twophase flow. The methodology of this project starts with taking points of the different components of the Francis turbine using reverse engineering, then these points are corrected in order to be meshed using the commercial software TURBOGRID. Using real operating conditions of the San Francisco hydroelectric power plant, the simulation of the 3 components of the turbine (runner, guide vanes and fixed blades) is performed in the commercial software FLUENT. In addition, the simulation was validated by means of an experiment, which was successfully simulated in FLUENT software and with a meshing performed in ICEM. The results obtained show that the phenomenon was captured with a good approximation. Although the results of both models are quite similar, a better appreciation of the phenomenon is observed in the K- ω SST model, but this model requires a higher computational resource
... The intensity of erosion is determined by eroding particle properties such as silt size, hardness, and concentration. It is further affected by operating conditions such as water velocity, impingement angle, and the characteristics of the base material [5,6]. There are various studies carried out about the effect of silt erosion on the performance of hydraulic machines and some of them are discussed in this section. ...
The global energy demand is increasing due to an increase in economic growth and urbanization which is set to rise by 4.6% in 2021. A major part of this increasing energy demand is accomplished by fossil fuels which create environmental pollution. Hydropower is the most mature, reliable, and cost-effective source of energy. However, the operation and maintenance (O&M) of hydro turbines is the main concern. The flowing water carries the sediment which passes through the underwater parts and creates silt erosion problems. A number of correlations are available in the literature to predict the silt erosion in hydro turbines considering very few parameters. However, no study has been reported on the complete scenario on O&M of hydropower plants. Under the present study, an attempt has been made to develop correlations for the efficiency factor using Curve fitting, ANN, and Support Vector Machine (SVM) methods. It is found that the developed correlation for efficiency using the ANN method is more reliable than other techniques. It is found to predict the efficiency with R²-value as 0.999986 having an average absolute percentage error of 0.0124% at RMSE of 0.0874%. The developed correlation may be used for developing efficient O&M strategies for hydropower plants.
