Turbine Runner Research Articles

A Mathematical Model of the Hydrodynamic Pressure Acting on a Turbine Runner Blade under the Rotor-Stator Interaction Based on the Quasi-Three-Dimensional Finite Element Method

In this paper, a turbine runner blade under hydraulic excitation was taken as the object of study and the mathematical hydrodynamic pressure model of a turbine runner blade under the rotor-stator interaction was established using quasi-three-dimensional finite element model. The regularity of the distribution of the hydrodynamic pressure was then investigated. First, the quasi-three-dimensional finite element model of a runner blade was established using the quasi-three-dimensional theory. Next, according to the pressure distribution from the numerical simulation, the mathematical mean pressure model of a node was established using the relative pressure difference method; the pressure fluctuation was then established taking the rotor-stator interaction into consideration. Then, based on the mean pressure and the pressure fluctuation of a node, the mathematical hydrodynamic pressure model for any position of a runner blade was obtained. Finally, the feasibility of the mathematical model was verified by an example analysis, and the internal relationship between the hydrodynamic pressure and its hydraulic parameters and the structural parameters of the blade was revealed, which provides a theoretical basis for further study of the dynamic characteristics of turbine runner blades under the rotor-stator interaction.

On the use of neural networks for dynamic stress prediction in Francis turbines by means of stationary sensors

Nowadays, one of the major mechanical issues of hydraulic turbines and particularly Francis turbines are the failures produced by fatigue. Due to the massive entrance of new renewable energies such as wind or solar, hydraulic turbines have to withstand off-design conditions and multiple transients, which greatly increase the risk of fatigue failures. Fatigue damage and crack propagation models are based on the static and dynamic stresses on the turbine blades. Therefore, an accurate and realistic determination of these stresses is of paramount importance although it is yet a challenging task. Numerical simulations have still limitations when predicting static and dynamic stresses in the most harmful conditions such as deep part load conditions and transients, which are highly stochastic. The installation of strain gauges on the blades gives accurate stress measurement but it involves long and very expensive measurement campaigns, as the turbine runner is submerged, confined and rotating. In this paper we propose a neural network-based method to determine the magnitude of static and dynamic stresses based on the measurements of stationary sensors, which greatly reduces the complexity and costs of strain gauge testing. Inputs of the neural networks are selected based on previous experience monitoring Francis turbines. The trained network can be implemented in advanced monitoring systems that could continuously evaluate the stress level of the turbine and determine the risk of possible fatigue damage.

Limitations of Modern Diagnostic and Prognostic Systems for a Hydraulic Unit’s Health

Modern diagnostic systems for the hydraulic unit’s health play an important role in ensuring the reliability and safety of the hydroelectric power plant (HPP). However, they cannot provide timely detection of such dangerous operational defects as fatigue cracks. This article reflects two main reasons for this problem. The first one is a high level of the individuality of hydraulic units, which does not allow the effective use of statistical methods of information processing, including BIG DATA and MACHINE LEARNING technologies. The second is the fundamental impossibility to identify cracks in some key components of hydraulic units only on the basis of data analysis from a standard diagnostic system usually used at the HPP. Developed computational studies on the example of Francis turbines confirmed this. It is proposed to supplement the functionality of standard diagnostic systems with a prognostic block for an individual analytical forecast of the unit’s residual lifetime based on the calculated assessment of fatigue strength. This article presents the developed conceptual diagram and the demonstration version of the proposed analytical predictive system. The comparison of the standard vibration diagnostic system and the proposed solution as a tool for the early detection of cracks in a Francis turbine runner shows some advantages of the proposed approach.

Numerical investigation of unsteady characteristics of a pump turbine under runaway condition

The runaway condition is unsteady and is of significant importance in pump turbines. In this research, the shear-stress transport (SST) k-ω turbulence model is used to simulate the unsteady flow in the vaneless region and the runner of a prototype pump turbine. The characteristics of pressure fluctuations, vortex identification based on Q criterion and local entropy generation rate (LEGR) in the pump turbine under runaway condition are studied, and the relationships of these physical quantities in the vaneless region are determined. Internal flow research reveals the motion and transmission characteristics of vortices in the vaneless region and the runner. The results show that the vortices that move clockwise in the vaneless region are responsible for the flow separation, the increase of LEGR, and the generation of the characteristic frequency 1.4fn of these physical quantities (pressure fluctuations, Q criterion and LEGR). In runner, it is found that the characteristic frequency of pressure fluctuation is 3.6fn, which satisfies a linear relationship with the characteristic frequency 1.4fn in the vaneless region. The vortices, moving in the vaneless and runner region, interact with the blades of runner and mainly contribute to the pressure fluctuation characteristic frequency in the runner.

Можливості застосування електромеханічного обладнання для компенсації реактивної потужності та підвищення надійності електропостачання

У статті розглянуто систему електропостачання підприємства хімічної промисловості. При проектуванні таких систем необхідно проводити вибір найбільш доцільного варіанту використання електрообладнання. Вибір здійснюється на основі всебічного аналізу технічних і економічних показників. Розглянуто рішення щодо забезпечення безаварійної роботи енергосистеми, яка живить підприємство хімічної промисловості.Для компенсації реактивної потужності, яка споживається електроустановками промислового підприємства, можуть бути застосовані синхронні компенсатори, а також використовуються синхронні машини.

On the Evaluation of Mesh Resolution for Large-Eddy Simulation of Internal Flows Using Openfoam

The central aim of this paper is to use OpenFOAM for the assessment of mesh resolution requirements for large-eddy simulation (LES) of flows similar to the ones which occur inside the draft-tube of hydraulic turbines at off-design operating conditions. The importance of this study is related to the fact that hydraulic turbines often need to be operated over an extended range of operating conditions, which makes the investigation of fluctuating stresses crucial. Scale-resolving simulation (SRS) approaches, such as LES and detached-eddy simulation (DES), have received more interests in the recent decade for understanding and mitigating unsteady operational behavior of hydro turbines. This interest is due to their ability to resolve a larger part of turbulent flows. However, verification studies in LES are very challenging, since errors in numerical discretization, but also subgrid-scale (SGS) models, are both influenced by grid resolution. A comprehensive examination of the literature shows that SRS for different operating conditions of hydraulic turbines is still quite limited and that there is no consensus on mesh resolution requirement for SRS studies. Therefore, the goal of this research is to develop a reliable framework for the validation and verification of SRS, especially LES, so that it can be applied for the investigation of flow phenomena inside hydraulic turbine draft-tube and runner at their off-design operating conditions. Two academic test cases are considered in this research, a turbulent channel flow and a case of sudden expansion. The sudden expansion test case resembles the flow inside the draft-tube of hydraulic turbines at part load. In this study, we concentrate on these academic test cases, but it is expected that hydraulic turbine flow simulations will eventually benefit from the results of the current research. The results show that two-point autocorrelation is more sensitive to mesh resolution than energy spectra. In addition, for the case of sudden expansion, the mesh resolution has a tremendous effect on the results, and, so far, we have not capture an asymptotic converging behavior in the results of Root Mean Square (RMS) of velocity fluctuations and two-point autocorrelation. This case, which represents complex flow behavior, needs further mesh resolution studies.

American eel resilience to simulated fluid shear associated with passage through hydroelectric turbines

American eel (Anguilla rostrata) populations have declined within their native range along the eastern coast of North America due to factors such as commercial fishing, habitat alteration, and dams. American eel are catadromous fish species, and high mortality rates (>40%) have been observed for freshwater life-stage adult eel passing downstream through hydropower turbines. Lacerations and sectioning of fish have been observed downstream of turbines and these injuries are commonly associated with direct contact with the turbine runner, whether through blade strike or pinching and grinding. Exposure to fluid shear may also be a source of injury, however, little is known about American eel susceptibility to this physical stressor. Eels are considerably flexible when compared to other fish species and lack other morphological characteristics that would make them susceptible to fluid shear, such as protruding eyes, large scales, and large operculum. European eel, which have previously been tested for susceptibility to fluid shear, were found to be resilient. To determine if American eel are also resilient to fluid shear, forty American eel were exposed to a water jet, simulating severe fluid shear (strain rate > 800 s−1) that fish may experience when passing downstream through turbines. No immediate or delayed (48 h) signs of injury were observed after exposure to severe fluid shear. Based on this study, and a previous study conducted on American eel susceptibility to barotrauma, the source of injury and mortality of American eel passing through turbines is likely attributed to blade strike or pinching and grinding.

Improving reliability and efficiency of hydraulic turbines

The article deals with new design solutions to improve the operating process based on new design solutions and effectively use hydraulic turbines for heads up to 800-1000 m, expand the operating range relative to flow rates and heads with high energy and cavitation indicators and reliability of operation on varying modes that differ from the optimum operating mode.On the basis of complex experimental studies of the flow pattern in a water passage and, first of all, in the hydraulic turbine inlet for heads of 400-500 m, this article reveals the causes of increased energy losses. The energy losses are caused by large vortexes occurring in the spiral casing; they distort the flow directed to the runner of the hydraulic turbine. Several ways for improving the operating process are proposed, including new design solutions.The issues of improving the operating process of various types of hydraulic turbines are discussed. This is done by creating an angular momentum upstream the runner blades, which is necessary for optimum operation of the hydraulic turbine due to flow inlet using nozzle vanes located around of the runner inlet. The advantages of new types of hydraulic turbines and a more advanced operating process are illustrated by the hill diagram of this turbine.

Wind Turbine Bearing Incipient Fault Diagnosis Based on Adaptive Exponential Wavelet Threshold Function With Improved CPSO

Signal processing is of vital importance to the incipient fault diagnosis and the safety running of wind turbines. To adaptively eliminate noise and retain the underlying fault characteristic signal, an adaptive exponential wavelet threshold denoising method based on chaotic dynamic weight particle swarm optimization with sigmoid-based acceleration coefficients (SBAC-CDWPSO) is proposed in this paper. Firstly, a high-order continuous differentiable adaptive exponential threshold function (AETF) based on stein unbiased risk estimation is put forward to improve the defects of the traditional threshold functions. Secondly, the sine map and the sigmoid-based acceleration coefficients are applied for the velocity updating mechanism in particle swarm optimization (PSO). Meanwhile, the dynamic weight, the acceleration coefficient and the best-so-far position are introduced to update the new position with the previous position and the velocity in PSO. Moreover, the gaussian mutation strategy is added, which can effectively maintain the diversity of the swarm and get rid of local optimization. Thirdly, the SBAC-CDWPSO is used to optimize the threshold iteration process in AETF, which can greatly improve the iteration speed of the optimal threshold, and enhance the noise reduction effect. Experimental results showed that the signal-to-noise ratio of our proposed method was higher and the root mean square error was smaller comparing with the pre-existing algorithms. Moreover, wind turbine generator bearing fault diagnosis classification results illustrated that the fault diagnosis rate of the proposed denoising algorithm was up to 96.67%, indicating that the proposed method has great potential in the incipient fault diagnosis of wind turbine bearings.

Coherent Structures Decomposition of Flow Field in Francis Turbine Runner Under Different Working Conditions

Coherent Structures Decomposition of Flow Field in Francis Turbine Runner Under Different Working Conditions

Influence of Particular Design Parameters of Radial Guide Vane Cascades on Their Hydraulic Performance at Variable Speed Operated Francis Turbines

The design of radial blade cascades, with the intent to become turbine guide vanes, lies in the basis of satisfying turbine runner needs for a particular turbine design point of interest. For conventional turbine operation, the hydrodynamic parameters in the pre-runner space can be relatively easily estimated. For variable speed turbine operation at the constant head, these parameters change in a way that cannot be easily predicted using conventional techniques. In this paper, the guide vanes, as crucial turbine sub-system which needs to perform efficient runner flow feeding for these operating ranges, are numerically tested in various geometrical shapes and configurations, to observe the cascades behaviour, in a way of estimating which cascade configuration satisfies certain hydrodynamic and efficiency considerations of the operating points of interest. The criteria which the guide vanes need to meet are based on hydrodynamic parameters and expansion of the turbine operating range.

Welding and Thermal Spray Processes for Maintenance of Hydraulic Turbine Runners: Case Studies

Abstract: Hydraulic runners are susceptible to failures by cracks or wear by erosion, corrosion, or cavitation. The modern runners are fabricated in carbon steel and martensitic stainless steel. Arc welding processes normally do the repair of eroded areas, or cracked parts. Each material or type of repair needs specific criteria, procedures, and precautions to guarantee their success and prevent future issues, like the recurrence of the cracks or reduction of the useful life of the runner by modifications of the original material. Wear-resistant coatings are applied by welding or by thermal spray processes, considering this last one has no metallurgical interaction with the material of the runner, keeping the original properties of the material. For several years the companies Copel GeT, Lactec, UTFPR, and UFPR collaborate on the study of different techniques, methods, and processes to repair hydraulic runners, this work aims to present a short compilation, and examples of some results obtained applied on real runners.

Performance optimization of doubly-fed induction generator (DFIG) equipped variable-speed wind energy turbines by using three-level converter with adaptive fuzzy PI control system

The present paper aims at optimizing the performance of a Doubly Fed Induction Generator (DFIG) equipped variable-speed wind energy turbine in utility grid-connected mode. Since maximum power extraction and output power quality improvement are considered the main challenges for enormous scale variable-speed wind turbines to meet the worldwide demand for clean energy, this work has two contributions; the first concerns the use of the three-level converters to upgrade the output power quality of the wind energy turbine through reducing the total harmonic distortion (THD) of the currents delivered to the power grid, whereas the second contribution intends to design an adaptive proportional-integral (PI) control system for the rotor side converter (RSC) control. The proposed adaptive PI control system is designed by combining the intelligent and adaptive nature of fuzzy logic control (FLC) and the simpleness of the PI controller framework to effectively optimize the DFIG wind energy turbine performance. In the proposed control system, the PI controller's gains are adjusted in real-time by a supervisory system based on FLC according to the wind turbine running conditions. The adopted control scheme to controlling the RSC comprises two cascaded regulation loops for reaching the maximum power point tracking (MPPT), that intends to extract obtainable maximum power of the wind energy turbine. The internal regulation loop is applied to control the rotor current while the external regulation loop is employed to regulate the generator speed. To prove the efficiency of the three-level converter and performance of the proposed control system, simulation studies were performed utilizing MATLAB/Simulink software. The obtained results through simulation clearly show that research paper purposes are achieved and the performance optimization of the wind turbine is well done.

An Indirect Measurement Methodology to Identify Load Fluctuations on Axial Turbine Runner Blades.

Smooth integration of intermittent energy sources, such as solar and wind power, into the electrical grid induces new operating conditions of the hydraulic turbine by increasing the off-design operations, start/stops, and load variations. Therefore, hydraulic turbines are subject to unstable flow conditions and unfavorable load fluctuations. Predicting load fluctuations on the runner using indirect measurements can allow for optimized operations of the turbine units, increase turbine refurbishment time intervals, and avoid structural failures in extreme cases. This paper investigates an experimental methodology to assess and predict the flow condition and load fluctuations on a Kaplan turbine runner at several steady-state operations by performing measurements on the shaft in the rotating and stationary frame of references. This unit is instrumented with several transducers such as miniature pressure transducers, strain gages, and proximity probes. The results show that for any propeller curve of a Kaplan turbine, the guide vane opening corresponding to the minimum pressure and strain fluctuations on the runner blade can be obtained by axial, torsion, and bending measurements on the shaft. Torsion measurements on the shaft could support index-testing in Kaplan turbines particularly for updating the cam-curve during the unit operation. Furthermore, a signature of every phenomenon observed on the runner blade signals, e.g., runner frequency, rotating vortex rope components, and rotor-stator interaction, is found in the data obtained from the shaft.

PENGARUH JUMLAH SUDU PADA PROTOTYPE PLTMH DENGAN MENGGUNAKAN TURBIN PELTON TERHADAP EFISIENSI YANG DIHASILKAN

Turbine is a component that plays an important role as an energy converter to be ableto generate electricity in the Micro Hydro Power Plant (MHP). The turbine used in this prototypeis a Pelton tubine. The Pelton turbine is a type of impulse turbine consisting of two blades as aprelude receiver for water jets from the nozzles by utilizing high water heads even though thewater discharge is small. This research will discuss the effect of the number of blades on therotation produced by the Pelton turbine and generator so that it can be seen the voltage,current, power produced that affects the torque value and efficiency obtained on the prototypeMHP. This study aims to obtain a turbine runner with the number of blades that can produce thehighest efficiency, then a variation of the pelton turbine runner is made with different number ofblade parameters from the runner with the number of blades according to the calculationobtained from the reference. Variations in the number of blades used are 14 blades, 16 blades,18 blades, 20 blades, and 22 blades. The results showed that the addition of the number ofblades starting from the smallest caused the performance of MHP to increase, the highestoutput obtained was using a turbine runner with a number of 22 blades which resulted in aturbine rotation of 852.2 rpm before the generator coupled and 497.2 rpm after coupling thegenerator. Generator rotation is 2133.8 rpm, Generator Voltage is 15.72 volts, Generator poweris 33.7 Watts and Torque is 0.6 Nm. The efficiency value using a runner with a number ofblades 22 is 4.54%. The resulting efficiency value is very low because the MHP prototype in generation is less effective and uses a small generation capacity DC generator, so it cannotgenerate power as much as hydraulic power.

PENGARUH TEKANAN AIR DAN SUDUT NOZZLE TERHADAP KARAKTERISTIK OUTPUT PADA PROTOTYPE PLTMH DENGAN TURBIN PELTON

Pelton turbine is an impulse turbine that is different from other turbines where the peltonturbine utilizes a large high water fall (head), even with a small water discharge. The problemwith Pelton turbine is that the head is still difficult to control because this type of turbine uses ahigh head to rotate the turbine runner and there is no formula / equation to determine the angleof the nozzle which produces maximum output. Based on the problems described, it isnecessary to make a micro hidro power plant prototype using a pelton turbine with a laboratoryscale so that it can do the testing of the influence of water and the nozzle angle to obtainmaximum output results on a micro hidro power plant using a pelton turbine. The prototypetesting in this study used various water pressures, namely 5 psi, 9 psi, 13 psi, 17 psi, 21 psi,and 25 psi with nozzle angles, namely 60º, 75º, and 90º. Based on the results of the study, anincrease in the value of water pressure provided with an optimal nozzle angle will cause themicro hidro power plant performance to increase. The maximum output obtained is when thewater pressure is 25 psi with a nozzle angle of 90º which produces a turbine rotation of 917 rpmbefore the generator is coupled and 326 rpm after the generator is coupled, the generatorrotation is 1321 rpm, the generator voltage is 12.9 Volts, generator power is 30.96 Watt, torque is 0.98 Nm, and the highest efficiency occurs when the water pressure is 21 psi with a nozzleangle of 90º which is 3.91%.

Effects of Geometrical Parameters in Gravitational Water Vortex Turbines with Conical Basin

Gravitational Water Vortex Power Plant (GWVPP) is an appropriate means to convert kinetic energy of water to rotational mechanical energy at the very low head site. This study aims to establish a basic reference for the design of the runner for the Gravitational Water Vortex Turbine (GWVT) with a conical basin. Seven different geometrical parameters have been identified for runner design, and the effect of these parameters on the system efficiency has been studied numerically and experimentally. The effect of these parameters has been studied over the range of speed with torque. The results from performance tests of these runners suggest that runner height is the most significant parameter to be considered in the design of a turbine runner for GWVPP with a conical basin. The results show that the efficiency of GWVT has improved up to 47.85% as obtained from experiments.

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.

A Method for Automated Cavitation Detection with Adaptive Thresholds

Hydroturbine operators who wish to collect cavitation intensity data to estimate cavitation erosion rates and calculate remaining useful life (RUL) of the turbine runner face several practical challenges related to long term cavitation detection. This paper presents a novel method that addresses these challenges including: a method to create an adaptive cavitation threshold, and automation of the cavitation detection process. These two strategies result in collecting consistent cavitation intensity data. While domain knowledge and manual interpretation are used to choose an appropriate cavitation sensitivity parameter (CSP), the remainder of the process is automated using both supervised and unsupervised learning methods. A case study based on ramp-down data, taken from a production hydroturbine, is presented and validated using independently gathered survey data from the same hydroturbine. Results indicate that this fully automated process for selecting cavitation thresholds and classifying cavitation performs well when compared to manually selected thresholds. This approach provides hydroturbine operators and researchers with a clear and effective way to perform automated, long term, cavitation detection, and assessment.

Operational Modal Analysis of hydroelectric turbines using an order based likelihood approach

The purpose of this paper is to estimate hydroelectric turbine runner modal characteristics from experimental measurements coming from asynchronous regimes. This is achieved by investigating resonances generated by the interaction of a structural mode with harmonics of the rotating speed. Resonances are extracted using order tracking and processed with a Fast Bayesian algorithm in an ambient manner to estimate modal parameters and related uncertainties. Since data collection and effective processing of hydropower turbine field measurements is in its early stages, this paper lays some foundations in the treatment of transient regime measurements. A novelty in this approach lies in the use of a probabilistic identification tool in Order Based Modal Analysis (OBMA). A numerical experiment and a study from a hydroelectric Francis turbine field measurements are introduced to illustrate the method.