Hydro Turbine Runner Research Articles

Fault diagnosis of hydro-turbine runner based on improved masking signal method incorporate RLMD

Sediment erosion and foreign object impacts can cause irreversible damage to hydro-turbine runner. It is proposed to use the Improved Masked Signal method combined with the Robust Local Mean Decomposition method (IMS-RLMD) to denoise the acoustic vibrational signals collected from the hydro-turbine runner under normal operating condition, sediment-landed water flow condition, and foreign object impact condition. The IMS method reduces modal aliasing, which is easily occurred in the RLMD decomposition method, and achieves excellent signal denoised by efficiently screening the components. To validate the effectiveness of IMS-RLMD method, we use the Support Vector Machine optimized by the Grey Wolf algorithm (GWO-SVM) to identify the acoustic vibrational signals denoised by different methods. The accuracy of signal set processed by the IMS-RLMD method is 96.67 %, and the accuracy of original signal set and the signal set processed by the EMD, LMD, RLMD and VMD methods are 66.67 %, 75 %, 78.3 %, 86.67 % and 90 %. This result shows that the IMS-RLMD method is not only more suitable for denoising hydro-turbine acoustic vibrational signals, but also retains more effective features in the signals. Meanwhile, the LSTM and CNN models are set as the control group, and the identification results show that the identification method, GWO-SVM, and the denoising method, IMS-RLMD, are the best adapted solutions. Furthermore, it is found that the frequency spectrum of the acoustic vibrational signals changes significantly when foreign objects are washed into the runner or when sediment-landed water flow through the runner. This study provides an effective reference for the daily condition monitoring method of hydropower units and a valuable addition to the condition monitoring and fault diagnosis system of hydro-turbine.

A novel denoising method of the hydro-turbine runner for fault signal based on WT-EEMD

Sediment wear is a significant cause of hydro-turbine failure. The wavelet threshold and ensemble empirical mode decomposition (WT-EEMD) method is proposed to denoising the acoustic vibration signals of hydro-turbine runners under normal and sand-laden water flow conditions. Ensemble empirical mode decomposition (EEMD) is performed on the acquired signals, and the decomposed high-frequency intrinsic mode function (IMF) is denoised using wavelet threshold. A nonlinear threshold function is constructed instead of the traditional threshold function in the wavelet threshold algorithm. The experimental results show that the WT-EEMD method is superior to the EMD, EEMD, and wavelet threshold. Moreover, it was found that when the sand-laden water flows through the hydro-turbine, it causes a change in the frequency spectrum. This study can provide a reference for the study of sand avoidance operation of hydro-turbines and provide a valuable supplement to the existing condition monitoring and fault diagnosis system of hydroelectric generators.

CNC machining optimization of hydro-turbine runner blade based on VERICUT

Aiming at the problem of low production efficiency caused by the unreasonable setting of cutting parameters for CNC machining of hydro-turbine runner blade, the Force module of VERICUT software is used to analyze and compare the cutting force, the cutting power, and the material removal rate of the blade under different cutting parameters, find the cutting parameters that can give full play to the machining capacity of the machine tool, and use the optimization function of Force to automatically adjust the feed speed in the machining program. The test results show that after the optimization of cutting parameters, the production efficiency of the NC machining program is significantly improved, and the cutting power of the machine tool spindle is stable.

Investigation of High-Cycle Fatigue Properties of Wire Arc Additive Manufacturing 13Cr4Ni Martensitic Stainless Steel

As one of the widely used materials for hydro turbine runners, 13Cr4Ni martensitic stainless steels (13/4 MSS) manufactured by forging and wire arc additive manufacturing (WAAM), respectively, were selected for high-cycle fatigue tests, and the effects of microstructures and defect characteristics on fatigue mechanism were investigated. The results indicate that compared to the forged 13/4 MSS, the microstructure of the WAAM test piece is very fine, and the martensite units, consequently, are smaller in size. The yield strength and ultimate tensile strength are 685 MPa and 823 MPa for the forged specimen and 850 MPa and 927 MPa for the WAAM specimens, respectively. The fatigue strength of 107 cycles at room temperature is 370 MPa for forged specimens and 468 MPa for WAAM specimens. The predominant defect of the forged 13/4 MSS specimen is inclusion, and the fatigue initiates mainly at the surface and subsurface. While for the WAAM specimen, the most commonly found defects are pores, and the fatigue initiation is internal and at the subsurface. In addition, the fine microstructure, as well as the high strength and hardness, enable the WAAM material to have higher fatigue strength. In order to assess the effect of defects on fatigue performance, the stress intensity factor and El-Haddad model were adopted in the present study. It was found that the forged specimens with fish-eye (FIE) zones and the WAAM specimens with granular bright facet (GBF) zones have longer fatigue life. The fatigue strengths of the forged 13/4 MSS were therefore predicted by defect size. In contrast, the fatigue strengths of the WAAM 13/4 MSS were predicted by both defect and GBF sizes.

Approach to the Laboratory Modeling of the Flow Velocity Distribution behind a Hydro Turbine Runner. 1. Design of Swirlers Vanes

Approach to the Laboratory Modeling of the Flow Velocity Distribution behind a Hydro Turbine Runner. 1. Design of Swirlers Vanes

Approach to the Laboratory Modeling of the Velocity Distribution Behind a Hydro-Turbine Runner. 2. Verification of the Method

Approach to the Laboratory Modeling of the Velocity Distribution Behind a Hydro-Turbine Runner. 2. Verification of the Method

Effect of Preheat Temperature and Welding Sequence on the Temperature Distribution and Residual Stress in the Weld Overlay Repair of Hydroturbine Runner.

The hydroturbine runner is the core of the whole hydroelectric generating unit, which is employed to transform water energy into mechanical energy. In the process of service, the runner frequently suffers from abrasion due to erosion and cavitation. Defects are usually repaired by welding. To acquire suitable weld cladding repair process parameters, a combination of experimental and numerical simulation was applied to investigate the temperature and weld residual stress distribution in the repair zone under the different welding repair approaches. The results illustrate that the temperature and welding residual stress distribution of the blade and the shroud are out of symmetry, the temperature conduction rate is faster on the blade side, and the high-stress zone is predominantly concentrated in the weld and its adjacent area. When the preheating temperature is up to 150 °C, the peak value of welding residual stress reaches a minimum of 796.29 MPa. The welding sequence can adjust the distribution trend of welding residual stresses. The welding sequence of three-stage welding can effectively reduce the welding residual stresses near the shroud at the water outlet side of the blade. The results of the study will provide theoretical guidance for the welding repair of hydraulic turbine runners.

The relation between internal flow and loss mechanism of unshrouded runners

Abstract High efficiency, low-cost, and reliable hydraulic turbines are in high demand for hydroelectric power generation, especially in medium and small-scale power plants. The authors’ laboratory has been developing unshrouded, i.e., band-opened runners of turbines to meet the demand. Those runners feature highly efficient performance and less expensive manufacturing costs produced by cutting, not by casting. For the sake of developing further improved unshrouded runners, it is necessary to understand their loss mechanism in detail. Therefore, in this study, the internal flow and the loss mechanism are investigated experimentally and computationally, with two different specific speed hydro turbine runners. First, Euler’s theoretical head on each runner is discussed to identify if they are influenced by the distinct specific speed. It demonstrated that the low specific speed turbine consumes greater potential energy in centrifugal force. Secondary, the loss mechanism in the unshrouded runners is investigated. The result showed that the dominant loss is caused by a tip leakage vortex developed by the collision of a leakage flow at the tip clearance and a secondary flow.

RANS解析における水車ランナを模擬した翼列に発生する剥離予測精度の改善検討

The investigation of turbulence model in CFD using RANS model was carried out to improve the stall prediction accuracy. Decreasing the coefficient of eddy viscosity in k-ω SST turbulence model improved the prediction accuracy of the separating flow on a NACA631-012 blade, but it made the prediction accuracy of the non-separating flow worse. Thus, the modified turbulence model that decrease the eddy viscosity based on the adverse pressure gradient and GEKO turbulence model were applied to analysis of a NACA631-012 blade. As a result, both of these turbulence model improved the predection accuracy of the lift characteristic in a wide range of angles of attack. In addition, it was clarified that the separating flow on the blade simulating the hydro turbine runner can be predicted with high accuracy by using these turbulence model. It is expected that the modified turbulence model based on the pressure gradient and GEKO model will improve the performance prediction accuracy at off design operationg points in the analysis of hydro turbine runner.

Primena reverznog inženjeringa pri projektovanju radnog kola Peltonove turbine

The paper describes the innovative solution for revitalization of hydro turbines by using the techniques of reverse engineering and virtual production. The application of modern digital tools in developing, designing and producing shows substantial benefits in improving the existing hydro turbine. Model testing in these cases is not necessary to implement because as the basis is used the known geometry of existing hydro turbine runners and buckets. Digital tools allow a relatively easy way to develop new geometry, improve hydraulic performances of turbines and reach a greater level of usefulness with minimal costs. This paper aims to show optimized geometry and improvement of the Pelton turbine performance using the presented approach

Advanced Optimization Tools for Hydro Turbine Runner Design

The objective of this work is to show how advanced optimization tools can be used for hydraulic turbine design, taking the example of a Francis runner design (new or refurbishment project). The public test case considered corresponds to a R&D turbine model of specific speed Ns = 0.5, originally developed at the Hydraulic Machinery Laboratory (LMH) of École Polytechnique Fédérale de Lausanne (EPFL). Firstly, a standard Computational Fluid Dynamics (CFD) process is used to predict performances, in the form of efficiency and cavitation behaviour. It features structured mesh for distributor (stay vane and guide vane), runner and draft tube. Automatic scripts are created to run computations for several guide vane openings and rotation speeds, covering the whole range of operating conditions, and allowing to obtain numerical hill charts of efficiency and minimum pressure to predict the occurrence of cavitation. Secondly, some operating points are purposefully selected for the optimization and objectives are defined to maximize efficiency while constraints are set for preventing cavitation. To continue with, a parametric blade model is defined: 3D blade shape is obtained from blade to blade sections and a stacking law. Sections are defined by camber and thickness. Finally, a Surrogate Based Optimization (SBO) with Evolutionary Algorithm (EA) is used for searching a global optimum. Design of Experiment (DOE) techniques are employed to efficiently define a database. Dynamic monitoring, data-mining and visualization tools are used; including Leave-One-Out (LOO), Analysis of Variance (ANOVA) and Self-Organizing Maps (SOM), with the objective of facilitating surrogate reliability assessment and a comprehensive understanding of key factors of the problem studied. This methodology is tested iteratively with the Francis Runner Hydraulic design: a first optimization is run, analysed and used to define a second optimization that shows increased benefits in particular for Best Efficiency Point. The results are analysed from a hydraulic point of view to identify the benefits and effects of the last optimization.

Francis turbine electrohydraulic inlet guide vane control by artificial neural network 2 degree-of-freedom PID controller with actuator fault

Hydropower system has great attention due to the cheapest and simplest renewable power generation, available potential and environmental concern. Francis turbine has wide operating range compare to other hydro turbine runner. Electrohydraulic Francis turbine inlet guide vane system has advantages like, high power density, self-lubrication property, very good controllability and rugged. Francis turbine inlet guide vane system consists of inlet guide vane actuation system, ring inlet guide blade arrangement, and controller. The main challenges with the electrohydraulically actuated inlet guide vane system are nonlinear characteristic, parametric uncertainty, and external disturbances. Further with respect to the real-life application of the electrohydraulic actuator piston seal damage may occur due to fitting problem of the seal, impurities in the hydraulic oil, high temperature of the hydraulic oil and so on. Recently some researchers are reported on modelling accuracy, accurate controller design and stability analysis. In the present study mathematical model of the Francis turbine has been developed based on velocity diagram to capture effect of water flow dynamics on turbine power generation with the consideration of Euler’s equation of turbo machinery. Detailed mathematical model of the inlet guide vane actuating system has been integrated with Francis turbine model. Artificial neural network 2 degree-of-freedom proportional integral derivative controller has been developed for Francis turbine power/speed control. The controller performance has been studied with the consideration of actuator piston seal damage. The controller performance has been studied with 30%, 60%, and 90% step increase of power demand. The controller performance also has been studied with 0.005 and 0.05 Hz frequency sinusoidal power demand. The proposed controller performance has been compared with conventional proportional integral derivative controller through various performance indexes. The proposed controller performances also have been compared with recently reported work due to step increase of torque and step decreases of power demand.

Feature Selection for Monitoring Erosive Cavitation on a Hydroturbine

This paper presents a method for comparing and evaluating cavitation detection features - the first step towards estimating remaining useful life (RUL) of hydroturbine runners that areimpacted by erosive cavitation. The method can be used to quickly compare features created from cavitation survey data collected on any type of hydroturbine, sensor type, sensor location, and cavitation sensitivity parameter (CSP). Although manual evaluation and knowledge of hydroturbine cavitation is still required for our feature selection method, the use of principal component analysis greatly reduces the number of plots that require evaluation. We present a case study based on a cavitation survey data collected on a Francis hydroturbine located at a hydroelectric plant and demonstrate the selection of the most advantageous sensor type, sensor location, and CSP to use on this hydroturbine for long-term monitoring of erosive cavitation. Our method provides hydroturbine operators and researchers with a clear and effective means to determine preferred sensors, sensor placements, and CSPs while also laying the groundwork for determining RUL in the future.

Stability and sensitivity analysis of the bending-torsional coupled vibration with the arcuate whirl of hydro-turbine generator unit

The vibrational stability and the shafting vibration sensitivity to some parameters of the unbalanced rotor bending-torsional coupling vibration of the hydro-turbine generator unit (HTGU) with the arcuate whirl were investigated in this study. First, a novel mathematical model of the unbalanced rotor bending-torsional coupling vibration considering the arcuate whirl of the shafting for the HTGU was proposed. Second, the vibrational stability of the shafting was studied using the phase trajectory, Poincare map, and frequency spectrum. Third, the shafting vibration sensitivity to some parameters was observed using the parameter bifurcation diagrams. Some shafting vibration phenomena were investigated by comparing the dynamic characteristics of three models, and the phenomena showed that the vibration amplitude of the hydro-turbine runner and generator increased, the torsional vibration angle of the spindle decreased, the generator vibration and the torsional vibration of the spindle sensitivity range to the hydro-turbine runner mass eccentricity changed, and the angular speed that mutates the dynamic vibration characteristic of the HTGU decreased when considering the arcuate whirl. The shafting vibration became stable, but the hydro-turbine runner vibration sensitivity range to the generator mass eccentricity and the generator vibration sensitivity range to the hydro-turbine runner mass eccentricity changed when considering the torsional vibration of the spindle. The vibrations of the generator and hydro-turbine runner are sensitive to the torsional damping coefficient in some ranges, the vibrations of the hydro-turbine runner and the spindle are sensitive to the generator mass eccentricity in some ranges, and the vibrations of the generator and the spindle are sensitive to the hydro-turbine runner mass eccentricity in some ranges.

Dynamic maintenance planning of a hydro-turbine in operational life cycle

Life cycle assessment (LCA) has been an emerging feature of modern structural health monitoring techniques that aims at evaluating equipment degradation process and it can be used for development of dynamic maintenance plans. A novel framework based on LCA is proposed in this paper for dynamic maintenance planning of hydro-turbines. Using a Hidden Markov Model (HMM) and the inspection data of hydro-turbine runner cracks from actual operations, the transition probability matrix and sojourn time of different crack states are obtained. This is utilized for predicting the expected remaining useful life (RUL) and the formulation of maintenance intervals. Moreover, maintenance plans are developed from the influence of cracks in different states leading to critical conditions. The proposed method, as demonstrated in the case study, efficiently updates the maintenance intervals and reduces the likelihood of failure events. The results of this paper provide a valid maintenance framework for achieving higher operational safety of hydropower stations with minimal resource losses.

Effect of tangential absolute velocity at outlet on open flume turbine performance

To address the electricity crisis in Indonesia, the use of open flume pico hydro turbines is a potential solution because Indonesia has 19 GW of hydropower resources at mini, medium, and pico scales. There are two concepts for the design of an open flume pico hydro turbine runner: Euler and Nechleba. Euler’s concept recommends that the absolute tangential velocity at the outlet of the blade be zero to optimise power absorption. By contrast, Nechleba explains that to reduce flow separation at the outlet of the blade (separation can reduce efficiency), tangential absolute velocity at the outlet of the blade must not be zero. Accordingly, this study compares the performance of blades designed with these two concepts using a computational fluid dynamics method. The results showed that the maximum efficiency of the blade using the Euler concept was 70.08%, while the blade using the Nechleba concept was 74.39%. Based on the results, a runner design concept that assumes a non-zero tangential absolute velocity at the outlet of the blade is recommended for use in designing an open flume pico hydro turbine runner.

Investigation of the effect of gaps between the blades of open flume Pico hydro turbine runners

This study will analyze the impact of gap size in two different runners called runner A (five blades) and B (six blades) to provides recommendations in design and manufacture of open flume turbine runners so that maximize the conversion of kinetic and potential energy. There are three methods was used to investigate its: analytical method is used to design the turbine; experimental to determine the actual turbine performance; computational fluid dynamics (CFD) to study the physical phenomena and re-check the velocity triangle on the runner to validate the design and manufacturing process. Using the results obtained, gaps between the blades can alter the velocity vector on the outlet and unbalance the rotation of runner; this imbalance could cause cavitation. Then, the decreasing torque is assumed because water pressure in the draft tube is similar to atmospheric pressure. Two conditions must be satisfied to maximize the performance of the turbine: swirling flow is required after the water flows past the runner in order to minimize the radial velocity on the outlet so that the draft tube can function properly; the dimensions of the blade must be carefully selected to avoid the formation of gaps between the blades.

Correlation of the Sediment Properties and Erosion in Francis Hydro Turbine Runner

Sediment erosion is the main problem for the hydropower situated in South Asia and South America. Due to sediment erosion, hydropower in those areas cannot operate in their full potential. Sediment erosion is a significant problem in turbomachinery and associated with degradation of turbine performance. The sediment erosion removes the turbine material from its surface. It can cause fracture of the turbine, which leads to an economic loss. In this paper, the sediment properties and its influence on erosion have discussed. Sediment properties like shape, size, and concentration have a direct influence on erosion. The numerical analysis was conducted to visualize the erosion in Francis hydro turbine. The most vulnerable area for the sediment erosion in Francis hydro turbine has predicted. The precise prediction of the sediment erosion in the turbine is the difficult task due to the synergetic effect of sediment parameters (shape, size, concentration, hardness, velocity). The accurate and precise indication of the sediment erosion required both experimental and computational analysis. In this study, solid-fluid computational analysis has done to identify the susceptible area on runner blade and influence of sediment parameters on erosion.

Study of the velocity distribution influence upon the pressure pulsations in draft tube model of hydro-turbine

One of the mechanisms of generation of powerful pressure pulsations in the circuit of the turbine is a precessing vortex core, formed behind the runner at the operation points with partial or forced loads, when the flow has significant residual swirl. To study periodic pressure pulsations behind the runner the authors of this paper use approaches of experimental modeling and methods of computational fluid dynamics. The influence of velocity distributions at the output of the hydro turbine runner on pressure pulsations was studied based on analysis of the existing and possible velocity distributions in hydraulic turbines and selection of the distribution in the extended range. Preliminary numerical calculations have showed that the velocity distribution can be modeled without reproduction of the entire geometry of the circuit, using a combination of two blade cascades of the rotor and stator. Experimental verification of numerical results was carried out in an air bench, using the method of 3D-printing for fabrication of the blade cascades and the geometry of the draft tube of hydraulic turbine. Measurements of the velocity field at the input to a draft tube cone and registration of pressure pulsations due to precessing vortex core have allowed building correlations between the velocity distribution character and the amplitude-frequency characteristics of the pulsations.

Hydroturbine Runner Design and Manufacturing

This research describes a methodology for the parametric design, computational fluid dynamics (CFD) aided analysis and manufacturing of a Francis type hydro turbine runner. A Francis type hydro turbine consists of five components which are volute, stay vanes, guide vanes, runner and draft tube. The hydraulic performance of the turbine depends on the shape of the components; especially on the shape of the runner blades. The design parameters for the other components are affected by the runner parameters directly. Runner geometry is more complex than the other parts of the turbine. Therefore; to obtain accurate results and meet hydraulic expectations, CFD analyses and advanced manufacturing tools are necessary for the design and manufacturing of the hydro turbine runner. The turbine runner design methodology developed is presented using an actual potential hydraulic power plant in Turkey. Index Terms—CFD, francis turbine, runner, design and manufacturing.