Hydraulic Turbine Research Articles

Features of the precessing vortex control in the Francis turbine model via jet injection

The study elucidates the mechanisms involved in actively controlling vortex phenomena within hydraulic turbines, particularly prevalent during partial load operations, leading to severe pressure fluctuations within the draft tube. Employing laser Doppler anemometry alongside acoustic sensors, the research delves into the flow structure and pulsation characteristics within the conical section of a Francis hydraulic turbine model under the influence of supplementary control jets injected through the runner streamline body. It was observed that orientation of the control jet has a discernible effect on reduction in pressure pulsations emanating from the precessing vortex core (PVC). An optimal injection strategy for diminishing pressure fluctuations while maintaining high turbine efficiency is identified. The findings align with earlier theoretical predictions derived from linear stability analysis of flow perturbations.

Numerical Study of the Effect of Splitter Blades on the Flow-Induced Noise of Hydraulic Turbine

Numerical Study of the Effect of Splitter Blades on the Flow-Induced Noise of Hydraulic Turbine

Analysis of multi-criteria decision-making methods for selecting a regulation system for a modular hydraulic turbine

In the work, an analysis and selection of the power regulation system for a modular straight flow hydro turbine with a capacity of 250 kW for a small hydropower plant. Initial data consisted of empirically specified quality indicators in the form of expert assessments. During the analysis, several multi-criteria analysis methods were employed, including the fuzzy logic method, implemented using the Fuzzy Logic Toolbox extension within the MATLAB environment, as well as a method based on the principle of morphological combinatorics, with results analyzed using a radar diagram.

Experimental Implementation of Hydraulic Turbine Dynamics and a Fractional Order Speed Governor Controller on a Small-Scale Power System

Experimental Implementation of Hydraulic Turbine Dynamics and a Fractional Order Speed Governor Controller on a Small-Scale Power System

A Methodology for Designing a Fish-Friendly Turbine Rotor Applied to High-Power Generation

Most large hydropower facilities employing conventional hydraulic turbines, e.g., Francis, Kaplan, or Bulb turbines, etc., cause significant harm to fish, resulting in high mortality rates, during turbine operation. This results from strong injury-inducing mechanisms at the rotor, including shear stresses, pressure variations, and pressure drop through the rotor. The study outlines a methodology for designing a fish-friendly turbine that is suitable for high-power generation applications. This methodology for a hydraulic channel design within the turbine rotor was derived based on classical fundamental applications of a rotor design, supplemented by subsequent assessments that incorporate fish-friendly design parameters that have been documented in the existing literature. A spiral curve characterized by a linear angle variation between the rotor's inlet and outlet was employed to project the blade geometry. Here, the Göttingen hydrofoil series was used, while a second-order polynomial function guided the hub design. Both of these parametrizations sought to enhance the turbine's hydraulic efficiency. Minimum Absolute Pressure, Strain Rate, and Pressure Variation Rate intervals were established as assessment criteria for fish survival for certain species, as has also been previously explored in the literature. The findings were outlined in terms of hydrodynamic performance and flow behavior within the rotor. An improvement in hydraulic efficiency was observed, transitioning from a Preliminary Turbine geometry design to an Optimized Turbine Geometry design. The turbine rotor was optimized using Computational Fluid Dynamics (CFD) simulations, generated from a Design of Experiments (DOE). Modifications to the hydrofoil type, the sweep angle, and the trailing edge angle of the blades were all made, coupled with integrations of assessments considering fish-friendly parameters.

An optimized particle swarm optimization algorithm for turbine torque and generator load parameter identification

Hydraulic turbine control system is a complex system with strong nonlinearity and multiple variables. Therefore, in order to better control the turbine system, it is necessary to obtain the parameters of key components. Aiming at the limitation of the traditional particle swarm optimization algorithm in global search ability, mutation operator and dynamic inertia weight coefficient are introduced to enhance the search ability of the algorithm. In addition, in order to further improve the global search performance of the algorithm, this paper combines the optimized particle swarm optimization algorithm with genetic algorithm to form a hybrid parameter identification algorithm. The hybrid algorithm not only uses the fast convergence of particle swarm optimization (PSO), but also uses the global search advantage of genetic algorithm (GA) to realize efficient and accurate identification of turbine torque and load parameters. Through MATLAB2021a/Simulink simulation experiments, the application effect of the algorithm in the identification of turbine torque and generator load parameters is verified. The simulation results show that the optimized particle swarm optimization algorithm has significant advantages in the accuracy and robustness of parameter identification, and the identified parameters have a high degree of fitting with the actual measured torque and speed. This study not only provides a new optimization strategy for the parameter identification of turbine regulation system, but also provides an effective intelligent algorithm solution for the parameter identification of nonlinear system.

Application of Multiobjective Optimization Based on Modified SPEA2 Method for Tuning FOPID plus Second‐Order Derivative Controller in Hydraulic Turbine Governing System

The controller design and parameter tuning of the hydraulic turbine governing system are critical for ensuring stability and safety of operation. In this study, we propose a novel design of fractional‐order PID plus second‐order derivative (FOPID2D) controller design for the HTGS system. In addition, we develop a modified strength Pareto evolutionary algorithm II (MSPEA2) to optimize the design parameters with multiple objectives. By combining fractional calculus and second‐order derivative, the FOPID2D controller offers enhanced control flexibility compared to conventional PID controller. To achieve the Pareto‐front, we employ the proposed MSPEA2 method as an optimizer, which is further improved using a Uniform–Cauchy–Gaussian hybrid mutation strategy. We demonstrate its numerical quality and diversity superiority over the conventional method through test function results. The designed FOPID2D controller, along with PID, fractional‐order PID, and PID plus second‐order derivative controllers, is employed in the load disturbance experiments of the hydraulic turbine governing system. Consequently, the control effect of the proposed FOPID2D controller is validated by comparison with other controllers.

Robust tracking control for nonlinear fractional order delayed systems: Modified repetitive control approach

AbstractThis study focuses on the problem of perturbation suppression and tracking control of nonlinear fractional order systems with time‐varying delay. To simplify the control process for such systems, the Takagi–Sugeno fuzzy model is used to describe the nonlinear fractional order delayed systems. Additionally, a modified repetitive controller is applied to develop an output feedback technique for the proposed systems. To ensure system stability, the study establishes new delay‐dependent stabilization conditions using a novel Lyapunov–Krasovskii functional (LKF). These stability conditions are expressed in formation of linear matrix inequalities (LMIs) by adopting a frequency‐distributed model transformation and some slack matrices. The proposed method demonstrates that the system output can track the desired input with ignorable error, while effectively rejecting disturbances. Finally, the efficacy of the proposed method is evaluated through simulations of the modified Chua circuit and the hydraulic turbine governing system (HTGS).

A Study and Optimization of the Unsteady Flow Characteristics in the Last Stage Impeller of a Small-Scale Multi-Stage Hydraulic Turbine

The demand for small-size multi-stage hydraulic turbines is experiencing rapid growth due to the ongoing efforts towards energy conservation and emission reduction. On account of their compact structural design, these turbines feature a more intricate internal flow configuration, rendering them prone to the creation of low-pressure zones, resulting in vapor–liquid two-phase flow, accompanied by the development of intense vibrations and noise, thereby adversely affecting the safety and stability of turbine operations. Concurrently, an innovative method for analyzing flow fields has been formulated combined with two-dimensional frequency domain visualization technology and proper orthogonal decomposition, serving to establish a diagnostic and optimization framework for the unsteady flow structures within rotating machinery by considering the features related to frequency distribution, spatial distribution, and energy contributions. It was found that there are two main unsteady flow structures which are the areas with high risks of vaporization under this study condition. According to the flow characteristics of the analysis, an optimization scheme was proposed to improve the two-phase flow problem in the secondary impeller, and the preliminary results were satisfactory.

Visualization and Location Determination of Pit Initiation Sites in Martensitic Stainless Steel during Corrosion-Fatigue Cyclic Plastic Deformation

Low-carbon martensitic stainless steels, such as 13%Cr4%Ni, are widely used in manufacturing hydraulic turbine runners. High tensile strength steel, such as cast CA6NM or wrought S41500 martensitic stainless steel, has an acceptable resistance to corrosion and cavitation, and reduces the weight and cost while offering a more efficient design. During operation, the combined effect of cyclic loading (fatigue) and corrosion reduces the fatigue strength and can initiate cracks at localized corrosion surface defects.In this study, we determined the bulk and localized corrosion behavior of wrought (S41500) and cast (CA6NM) 13%Cr4%Ni stainless steel before and after plastic deformation.Susceptibility to pitting corrosion was studied using open circuit potential and potentiodynamic polarization measurements in 0.020 M NaCl. Localized corrosion behavior was studied using a scanning droplet cell (SDC) and oil immersed scanning electrochemical cell microscopy (OI-SECCM). The bulk and localized electrochemical measurements after different surface preparation methods (mechanical polishing, followed by etching or electro-etching in different media) were compared.The surface defects including micro-voids and inclusions of different types were characterized. The location of pit initiation was then determined using scanning electron microscopy and profilometry imaging. A three-electrode microcell with a working electrode of 1 mm² was designed and hyphenated with optical microscope to allow in situ tracking of pit initiation and growth. Chronopotentiometry and chronoamperometry controlled pit initiation, while optical microscopy demonstrated dynamic release of corrosion products and measured oxide repassivation kinetics.Finally, the in situ technique was developed further to include a microtensiometer fatigue apparatus to study the synergy effect between corrosion and fatigue. Location of pit initiation was compared with and without plastic deformation. Videos of pit initiation and growth will be presented.

Transient coupling modeling and dynamic response analysis of hydraulic turbine governing system and shafting system

To address the challenges posed by the connection of new energy sources to the grid, pumped storage power stations (PSPSs) are required to frequently engage in transient processes to maintain load balancing and regulate grid frequency. It remains difficult, however, to evaluate the transient characteristics of the hydraulic turbine governing system (HTGS) and shafting system because of the lack of suitable models. This study seeks to address this challenge by establishing a transient turbine model based on the surface-cluster method and the shafting system transient coupling model, accounting for hydraulic-mechanical-electrical factors. HTGS and shafting systems' dynamic response characteristics are investigated under two small oscillation processes and eleven closure laws of guide vanes (CLGVs). The findings reveal that the shafting system vibration increases with the load drop during small oscillation processes. Conversely, sudden load increases reduce shafting vibration and the change of vibration is related to the force of the blade. Moreover, the study identifies that under the fast-slow two-phase CLGV, the maximum relative head and rotor radial amplitude increase with decreasing guide vanes (GV) opening of the turning point, while the change in maximum relative speed is opposite. Under the slow-fast two-phase CLGV, the maximum head and speed increase with decreasing GV opening of the turning point, while the maximum radial amplitude of the rotor is the opposite. Finally, under all the three-phase CLGVs, the transient characteristics of the head, speed, and shafting vibration under close-close-close (CCC) CLGV are the best. The innovation of this paper is to provide a method to establish the transient coupling model of HTGS and shafting, and to study the stability and transient response characteristics of HTGU.

Minimization of the weight of the blade of the aerial installation by an adaptive hybrid optimization method

In various fields of engineering practice, such as turbine building, power engineering, elements of thin-walled structures are widely used, which operate under increased loads when interacting with air or water. These include blades of impellers of radial-axial and rotary-blade hydraulic turbines, blades of wind power plants. Designing highly efficient machines and structures with the required level of reliability requires determining their optimal characteristics. The article proposes an adaptive method for finding the minimum of an arbitrary smooth multivariable function. The method was used to solve the benchmark optimization problem of a function in the form of a valley. The essence of the proposed algorithm lies in the sequential approach to the bottom of the valley and the subsequent movement in the direction of decreasing the objective function. Comparison of the results of calculating the minimum point of the function is performed using both non-gradient and gradient methods, namely: Powell, Hook-Jeeves, the steepest descent method and the developed method. It was found that the effectiveness of the proposed method is greater than the usual search algorithms, but it is not without its drawbacks. The method is proposed that represents a number of hybrid methods, which form a hybrid coalition Proposed hybrid algorithm does not provide a satisfactory result in the "single" search. The search algorithm reaches a point where all the values of the function at the surrounding points are greater than the values at the obtained point, and the algorithm cannot overcome the barrier. To solve the problem, it is necessary to take the obtained point as a new starting point and repeat the algorithm for finding the minimum of the function, that is, use the multistart method. The proposed method was used to solve the problem of optimizing the blade of an air installation, which was reduced to the problem of unconditional optimization using the method of penalty functions, but the goal function had a significantly valley structure. The optimal values of section thicknesses were obtained, which made it possible to build a blade with improved characteristics.

Cavitation identification in a hydraulic bulb turbine based on vibration and pressure fluctuation measurements

Cavitation can lead to reduced efficiency, increased vibration and noise in hydraulic turbines. Accurate and rapid identification of cavitation states in a turbine is important. In this work, a test system has been constructed for a hydraulic bulb turbine, to synchronously obtain cavitation images on runner blades, vibrations on both the runner hub and the runner chamber, and pressure fluctuations on the draft tube of the turbine at different cavitation conditions. The multifractal characteristics of the collected signals obtained by using the multifractal detrended fluctuation analysis method have been analysed and compared in detail. It is found that the multifractal characteristics of the vibrations and pressure fluctuations depend strongly on the cavitation state. The multifractal strength of the pressure fluctuations in the draft tube is stronger than that of the vibrations on the runner, induced by cavitation. Furthermore, some multifractal parameters of vibrations and pressure fluctuations have been extracted and used for cavitation state identification in the turbine, which is important for safe operation of a turbine.

On the Vaneless Space Vortex Structures in a Kaplan Turbine Model Operating at Speed No Load

The growing installation of intermittent renewable energy sources is forcing hydraulic turbines to work more frequently at speed no load when dangerous vaneless space vortex structures and stochastic flow phenomena can occur. An experimental campaign has been performed in a reduced-scale Kaplan turbine model at speed no load for different combinations of guide vane and runner blade angles under non-cavitation and cavitation conditions. Several simultaneous vaneless space vortex structures, all of them inducing torsional rotor vibrations, have been observed. Nonetheless, only one of them has been found to dominate over the rest depending on the blade and guide vane angles. Off-board pressures, torques and vibrations as well as on-board strains have been measured to characterize their nature, intensity, dynamic behavior and induced structural response. Their precession frequencies have been found to depend on the discharge factor, the number of vortices and their location inside the vaneless space. Under cavitation conditions, their dynamic behavior has not been significantly altered but the induced structural response has increased at the low-pressure side of the turbine.

Analysis of Solid-Liquid Two-Phase Flow in the Area of Rotor and Tailpipe

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.

Multi-obective performance analysis of a wind power plant equipped with a PAT system

In conventional wind power plants, the wind turbine drives an electrical generator equipped with an AC/DC converter for battery charging purposes and with an inverter inverter to supply power to the grid / AC load. This approach exhibits some drawbacks like the energy losses associated to the power electronics and the cost and the waste management of the battery storage systems.To overcome such drawbacks, this work proposes a new plant scheme, where the battery system has been removed (or strongly reduced) and the storage task is accomplished by a pumping system equipped with a reversible hydraulic machinery which can operate both as centrifugal pump and a hydraulic turbine (called Pump as Turbine). In this scenario, when the wind velocity is quite high, the reversible hydraulic machinery, working as centrifugal pump, will store energy in the form of potential energy pumping fluid to an elevated water reservoir. On the contrary, in low wind conditions, the Pump as Turbine will operate as a hydraulic turbine, helping the wind turbine to overcome the external mechanical load. This solution results in a number of advantages: lower plant costs, longer Pump as Turbine life with lesser maintenance and reduced waste costs.The present work focuses on a multi-objective performance analysis of the proposed wind system power scheme. Specifically, this multi-objective sensitivity analysis will be addressed to the net potential energy stored by the reversible hydraulic machinery, the extracted wind energy and the torque supplied by the Pump as Turbine in hydraulic turbine mode. Such an analysis will considered as design variables the Pump as Turbine (centrifugal pump mode) specific speed (pump geometry), the gear box transmission ratio between the centrifugal pump and the wind turbine and the pump head. The aim of this analysis is to evaluate the design variables range which could lead to determine the set of the multi-objective wind systems optimal design.

$H_{\infty }$ Asynchronous Admissibilization for Nonlinear Singular Delayed Hybrid Hydraulic Turbine Governing Systems With Impulsive Perturbations

This article researches <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$H_{\infty }$</tex-math></inline-formula> asynchronous admissibilization for nonlinear singular delayed hybrid hydraulic turbine governing systems with impulsive perturbations. By exploiting Takagi-Sugeno (T-S) fuzzy technique, the fuzzy singular delayed hybrid hydraulic turbine governing system with impulsive perturbations is built, which can not only accurately and concisely describe the dynamic behaviors of the pipeline, but also resist damages for the hydraulic turbine system caused by sudden reasons. Then, the asynchronous fuzzy state feedback controller (FSFC) is designed by using parallel distributed compensation (PDC) technique, and the asynchronous mechanism (AM) between the modes of FSFC and the modes of controlled plant is depicted by a hidden Markovian model. By constructing an improved timer-dependent (T-D) Lyapunov-Krasovskii (L-K) functional, the new criteria about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$H_{\infty }$</tex-math></inline-formula> admissibilization for fuzzy singular delayed hybrid hydraulic turbine governing systems with impulsive perturbations can be acquired. The gains of asynchronous FSFC are expressed by solving linear matrix inequalities (LMIs). Impulsive operators are successfully generalized and extended from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbb {R}$</tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbb {R}^{n\times n}$</tex-math></inline-formula> , which makes the approach presented in this article more universal. Finally, the simulation results prove the correctness and availability of the method provided in this article.

Pumps as HPRTs

Using centrifugal pumps as hydraulic power recovery turbines (HPRTs) to maximize plant energy efficiency, profitability, and sustainability.

Pelton turbine jet flow investigations using laser Doppler velocimetry

Hydropower is a sustainable and clean renewable energy source. The Pelton turbine is an impulse type of hydraulic turbine and operates under high head and low discharge. It comprises an injector, which converts high-pressure water into kinetic energy as a high-speed free surface water jet that impinges on the runner generating power coupled with an electric generator. The water is highly accelerated in the nozzle, which produces turbulent kinetic energy in the jet flow. Before impinging on the runner, the surrounding air is entrained into the jet, which causes the jet dispersion. The effective conversion of water energy into mechanical energy and the quality of a jet depend significantly on the uniformity of the jet. However, the jet encounters instabilities and non-uniformity caused by secondary flow and turbulence. Jet surface and velocity distribution do not remain symmetric. Investigation of the jet's velocity profile and turbulence intensities is important to understand the flow behavior and improvements in the design of injector. In this study, the experimental investigation of the jet has been performed using the laser Doppler velocimetry (LDV) system. The turbulent intensity and instantaneous velocity of the jet are analyzed at different locations along the jet flow. The velocity wake zone occurs around the center of the jet, which diminishes in the axial direction of the jet, with non-dimensional jet velocities values 0.91, 0.92, and 0.94 at x/Do of 0.5, 1, and 2 for ∼98% nozzle opening. The secondary flow velocity magnitude is larger for 90°–60° injector jet flow than for 90°–50°. The jet velocity profile obtained from the LDV has been compared with computational fluid dynamics analysis.

Pumps as turbines for pumped hydro energy storage systems - A small-size case study

Pumped Hydro Energy Storage (PHES) technology has been used since early 1890s and is, nowadays, a consolidated and commercially mature technology. PHES systems allow energy to be stored by pumping water from a lower-to a higher-level reservoir. Subsequently, this energy can be released through a turbine placed in a penstock, which connects the two reservoirs, to produce energy. Although these plants have historically been employed at large power scales (in the order of hundreds of MW), in recent years, micro- and small-scale plants are becoming more interesting, due to their possibility of being integrated with renewable energy systems (RES) used in autonomous island grids. Capital costs associated with hydraulic machines used in PHES systems represent the most critical economic factor, which can be mitigated by using commercial centrifugal pumps in reverse mode (Pumps as Turbines, PATs) in place of small hydro turbines. These expected economic benefits must be weighed in each specific case study, with some drawbacks related to the use of PATs, mainly associated to a lower round-trip efficiency with respect to specifically designed pumps and turbines.In this work, a small-scale PHES plant has been studied coupled to an existent photovoltaic system for the integration in the electric grid of a small island in Southern Italy. Two different PHES outlines have been compared based on techno-economic considerations. The former is a typical PHES system composed of both pumps and a turbine, while the latter uses only an array of parallel pumps which work also in reverse mode. The analysis demonstrates the feasibility of integrating a photovoltaic and PHES plant, which results in a lower cost of electricity production, while PHES performance in the PAT-based outline results penalized by the lower efficiency of PATs with respect to the hydraulic turbine.