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This paper deals with the reactivation of three test benches of high, medium and low power electric generators for hydraulic energy conversion in the University of Carabobo Hydraulic Laboratory. The method involves three stages: i) Description of three high, medium and low power electric generators for hydraulic energy conversion, ii) Rehabilitation of three high, medium and low power electric generators for hydraulic energy conversion and iii) Evaluation of performance indexes of high, medium and low power electric generators for hydraulic conversion. The results indicate that for the low power electric generator, the position angle of the distributor blades is an experimental factor that has a significant effect on the response variables studied. With respect to the medium and high power electric generators, the most influential factor on operation and power generation is the flow supplied.

Model tests and model calculations are the most basic means currently available to study the characteristics of the axial-flow pumps and Kaplan turbines in a systematic manner. Large and medium-sized turbine units and axial-flow pumps must rely on model tests and model calculations to ensure the performances of prototype units before designing. The conversions between models and prototypes are mainly carried out through similarity criteria. However, it is difficult to meet all the similarity criteria in the model tests and the similarity conversions, and the hydraulic and cavitation performances of the model and the prototype are often different. In this paper, numerical calculations of shroud clearance cavitation are performed on both the prototype and model using different cavitation coefficients. The results indicate that the prototype and model have a similar clearance cavitation flow regularity when the cavitation coefficient changes, but they have different energy characteristics and cavitation characteristics. In cavitation conditions, the prototype has higher energy characteristics than the model and the critical cavitation coefficient is similar to the model. When the cavitation coefficient is higher than the critical cavitation coefficient, compared to the model, the blade cavitation performance of the prototype is worse, and the clearance cavitation and runner chamber cavitation are more serious. If the cavitation coefficient decreases to the device cavitation coefficient, the runner chamber of the prototype will cavitate, even though the model has not cavitated yet. The comparison of shroud clearance cavitation between the prototype and the model can be used as a reference for the accuracy of similarity conversion results between the model and the prototype. It also has a positive impact on the design and operation of the prototype.

Kaplan turbines, also known as movable propeller turbines, are attractive for power generation from water currents. They are controlled by guide vanes and runner blades, whose synergistic relationship plays an essential role in maintaining the stable operation of Kaplan turbine systems during transient process. Here we introduce a novel nonlinear dynamic model of a Kaplan turbine system with synergistic regulation by coupling the turbine, generator and governor. Sensitivity and stability analysis of the Kaplan turbine system are carried out based on EFAST method and stability theory. Effects of synergistic regulation on transient characteristic and stability of the Kaplan turbine system are investigated during transient process. Dynamics characteristic and stability region of the Kaplan turbine system suggest that transient performance improvement can be obtained by adjusting the synergistic relationship between the guide vanes and turning angle.

Mitigation measures for downstream migratory Atlantic salmon smolts (Salmo salar L.) at migration barriers usually turn out to be insufficient to enable safe and quick passage, probably due to a lack of knowledge about their behavioural responses. Combining manual 2D tracking with hydrodynamic modelling has been rarely performed but might be useful to highlight environmental factors influencing smolt behavioural tactics and the choice of a migration route. We investigated the smolt downstream migration at a hydropower plant that offers five migration routes, including a Kaplan turbine and a fish-friendly Archimedes screw. Four behavioural tactics were defined to describe the smolt expressed behaviour, which was mainly complex and hesitant. The majority of the smolts approached more than one migration route before crossing the site and the Kaplan turbine turned out to be the most approached route, contrary to the Archimedes screw. Hydrodynamic modelling highlighted that flow velocity and water depth were used as hydraulic cues in the selection of a migration route, as the smolts preferred higher flow velocities and water depths. The comprehension of the factors influencing the research behaviour at hydropower plants may be useful to design attractive mitigation measures and to guide the smolts efficiently towards safe routes.

In this study, numerical analysis is conducted to investigate the failure modes in Kaplan turbine. All necessary steps for Kaplan turbine failure analysis are presented in this work using the modal analysis computational approach. The modal behaver analysis is carried out on a model of an existing Kaplan turbine blade, which is based on the existing turbine used in Haditha hydropower plant in Iraq. This work investigates the modal behavior of the blade of interest, which aid in predicting structural damage initiation. The Kaplan turbine blade is designed using the commercial software ANSYS and SolidWorks. To simulate the blade in operation, the blade is fixed from one end, and all degrees of freedom are measured. Moreover, the turbine blade is moved and rotated to simulate multiple operational conditions. Both mode shapes and natural frequencies are predicted and analyzed using the two aforementioned commercial software and the numerical formula involving the arrest Lanczos method. It is clear from the results that the natural frequency of the specified mode shape does not match with the natural frequency of the runner blade. Hence, there is no failure due to resonance phenomenon in this specific Kaplan turbine. The future work must investigate other aspect of the failure modes in such turbine, such as unbalance dynamic loading. The Results obtained from this study will help study the different possibilities for detecting the failure of the Kaplan blade by examining the modal behavior of the blade.

This paper investigates the accuracy of Reynolds-averaged Navier-Stokes (RANS) turbulence modelling applied to complex industrial applications. In the context of the increasing instability of the energy market, hydropower plants are frequently working at off-design parameters. Such operation conditions have a strong impact on the efficiency and life span of hydraulic turbines. Therefore, research is currently focused on improving the design and increasing the operating range of the turbines. Numerical simulations represent an accessible and cost efficient alternative to model testing. The presented test case is the Porjus U9 Kaplan turbine model operated at best efficiency point (BEP). Both steady and unsteady numerical simulations are carried out using different turbulence models: k-epsilon, RNG k-epsilon and k-omega Shear Stress Transport (SST). The curvature correction method applied to the SST turbulence model is also evaluated showing nearly no sensitivity to the different values of the production correction coefficient Cscale. The simulations are validated against measurements performed in the turbine runner and draft tube. The numerical results are in good agreement with the experimental time-dependent velocity profiles. The advantages and limitations of RANS modelling are discussed. The most accurate results were provided by the simulations using the k-epsilon and the SST-CC turbulence models but very small differences were obtained between the different tested models. The precision of the numerical simulations decreased towards the outlet of the computational domain. In a companion paper, the pressure profiles obtained numerically are investigated and compared to experimental data.

The present study intends to investigate numerically the impact of: i) the fluid added mass, ii) the turbine rotational speed and iii) the variation of the runner blade bearing stiffness due to the turbine water head on the modal response of a reduced scale Kaplan turbine. The impact of each variable has been quantified by means of a series of numerical modal analyses of the turbine in vacuum and in water, and at rest and rotating. It has been found that the natural frequencies of the Kaplan turbine model are sensitive to all the variables investigated in the present paper, the added mass being the factor which has the greatest impact.

The problematic of pitting corrosion on blades of Kaplan turbine is discussed. Corrosion behaviour was observed during the first year of service. Material of the water turbine blades is martensitic stainless steel GX4CrNi13-4. Chemical composition and hardness of blades was measured, EDS analysis of corrosion products and microstructural evaluation on replicas were carried out. The main problem was found in heterogeneities in the cast microstructure and local disproportions in chemical composition. Influence of microbiologically induced corrosion and surface roughness is considered.

The rotor-stator interaction and the corresponding pressure fluctuations represent one of the sources of pressure and load fluctuations on the rotating parts of rotating machineries. The high-Reynolds flow is subject to rotation in the comparably large vaneless space of axial turbines, causing wake interaction and wake dissipation in this region. This increases the level of flow complexity in this region. This study examined the effect of the flow condition entering the spiral casing on the flow condition within the distributor and the runner and the physical source of pressure fluctuations exerted on the runner of a Kaplan turbine model. Simulations were performed within the water supply system, including the upstream tank, penstock, and the Francis turbines, the level of entering the spiral casing; the results were compared with laser Doppler anemometry (LDA) results. The results were considered as the inlet boundary condition for simulation of the turbine model from the spiral inlet to the draft tube outlet to investigate the flow condition within the distributor and the runner. The CFD simulations showed that the water supply system induces inhomogeneity to the velocity distribution at the spiral inlet. However, the flow condition does not affect the pressure fluctuations exerted on the runner blades due to the rotor-stator interactions. Moreover, the dominant frequencies exerted on the runner blades were accurately approximated although the amplitudes of the fluctuations were underestimated.

The paper presents a detailed hydromechanical analysis of the flow in horizontal Kaplan turbines, with a focus on the trajectory of the streamlines in the essential areas of the installation. The three-dimensional structure of the flow, the formation of vortices, the velocity distribution and the influence of the constructive parameters on the hydraulic performance are investigated. The study combines analytical methods with CFD simulations to identify the areas with energy losses and cavitation potential, providing hydromechanical optimization solutions. The results contribute to improving the design and operation of horizontal Kaplan turbines, with a direct impact on the efficiency and functional stability.