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Hydropower plants are a form of renewable energy resources, which comes from flowing water. The turbine is used to drive the generator then convert mechanical energy into electrical energy. The turbine wheel is located inside the turbine housing and the turbine wheel rotates the power shaft. One of the most used turbines is a cross-flow turbine. The pattern of water jet flowing throughout the empty space of the runner of the cross-flow turbine is influenced by the number of active runner blades pounded by water from the turbine nozzle. The difference in the flow patterns was believed having a relation to the performance differences of the three turbine models. The flow visualizations of water passing through the empty space of the cross-flow turbine runner were taken from the experimental study intended to investigate performance characteristics of three cross-flow turbine models designed on the same value of flow rates, runner diameters and rotational speeds; but each turbine model having different values of runner width as well as nozzle entry arc. Both of the nozzle and runner widths were designed as the function of the nozzle entry arc, therefore the shorter pair of runner-nozzle width the larger nozzle entry arc and vice versa. The flow visualizations of water passing on the turbine were studied using the empty space of the cross-flow turbine. The three models were tested on the same head and the same flow rate at the speed of 50, 100, 150, 250, 300 and 500 rpm. The photos of water flowing through the empty space in the turbine model runners were taken to find out the conditions of flow and the efficiency of the models was calculated to show the performance of the turbine. Images are taken within 10 cm and parallel to the turbine. The cross-flow turbine models were designed with 197 mm runner diameter of each and have the ratio of runner diameter to runner length of 1:2. One side of each turbine model end disk was made from transparent media named perspex facilitating the researcher to observe the water flow condition during flowing through inside the runner. The conditions of the flow of water passing through the empty space of turbine wheels were photographed using a Nikon camera equipped with a hallogen lamp having a power of 1000 watts to capture the difference of flow pattern among the three models of the turbine. The nozzle entry arcs used in this experimental study were 75o, 90oand 120o. In addition, the nozzle of each model has the same cross-sectional area and the roof of each was designed having roof curvature radius centered on the shaft axis. Such nozzle roof curvature was expected to be able to deliver water in the better direction as well as its flow condition as the water enters the turbine runner. The magnitude of the nozzle entry arc determines the number of active vanes pounded by the jet of water coming out of the nozzle, these conditions affect the pattern of water flow at the moment of passing through the empty space of the turbine wheel and then this flow pattern was believed to affect the performance characteristic of the cross-flow turbine. One side of each runner disk was made from Perspex, for the researcher to be able to observe the water flow condition during flowing through inside the runner.

This study looked at the effects of flow rates and guide vane angles on the performance of a cross flow turbine, which can be used to generate energy and hydraulic power with low head and low flow rates of water. A fluid dynamic analysis was performed on the cross-flow turbine with the aid of finite element techniques. The simulation was solved after validating the convergence of the provided model and its boundary conditions, with the outputs being the velocity profiles of the flow in the rotor and the pressure distribution on the rotor surface during its rotations. Experimental evaluation of the cross-flow turbine guide vane positions at a flow rate of 0.8, 0.6, and 0.5 m3/s was conducted, and it was discovered that a maximum turbine speed of 482 rpm and a generator speed of 1920 rpm were produced at the rotor shaft at a flow rate of 0.8 m3/s with a head of 25 m, and this data was validated by the results produced from the simulation. Doi: 10.28991/HIJ-2022-03-01-06 Full Text: PDF

Cross-flow turbines convert kinetic power in wind or water currents to mechanical power. Unlike axial-flow turbines, the influence of geometric parameters on turbine performance is not well-understood, in part because there are neither generalized analytical formulations nor inexpensive, accurate numerical models that describe their fluid dynamics. Here, we experimentally investigate the effect of aspect ratio - the ratio of the blade span to rotor diameter - on the performance of a straight-bladed cross-flow turbine in a water channel. To isolate the effect of aspect ratio, all other non-dimensional parameters are held constant, including the relative confinement, Froude number, and Reynolds number. The coefficient of performance is found to be invariant for the range of aspect ratios tested (0.95 - 1.63), which we ascribe to minimal blade-support interactions for this turbine design. Finally, a subset of experiments is repeated without controlling for the Froude number and the coefficient of performance is found to increase, a consequence of Froude number variation that could mistakenly be ascribed to aspect ratio. This highlights the importance of rigorous experimental design when exploring the effect of geometric parameters on cross-flow turbine performance., This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Hunt et al, J. Renewable Sustainable Energy 12, 054501 (2020) and may be found at https://doi.org/10.1063/5.0016753. Supplementary material can be found in the UW ResearchWorks archive at http://hdl.handle.net/1773/45618

This research computationally investigates the complex dynamic stall phenomena of a cross-flow turbine blade utilizing modal analysis to identify pertinent events within the cycle. The blade rotation perpendicular to the freestream generates a curved relative flow, a non-sinusoidal variation of relative flow speed and angle of attack, and the necessity of travelling through its own wake. These complexities have challenged traditional predictors of dynamic stall such as pitch rate, pitching moment, or relative angle of attack. To investigate these phenomena, aerodynamic loads and flow fields on the blade from large-eddy simulations are examined across two tip speed ratios. Proper orthogonal decomposition of the velocity fields is employed to analyze the spatio-temporal evolution of the dominant flow features. The modes' time development coefficients reveal a stronger representation of the flow at the higher rotation rate, capturing the trend of relative flow velocity magnitude and lift generation on the blade, along with critical events such as vortex formation and detachment. Additionally, mean power generation is enhanced by 40\% by applying a non-constant rotation rate (intracycle control or angular velocity control). The flow fields, supported by corresponding changes in the modal analysis, demonstrate that a delayed stall behavior is responsible for the additional power extraction. Finally, flow curvature, history effects, and induced flow are identified as significant factors that modify the dynamic stall onset and resulting force and moment curves as compared to non-rotating pitching or plunging foils.

A bi-axial cross-flow water turbine is numerically simulated to evaluate its performance with a view to carrying out experiments on a prototype. Two axes of rotation and a chain-pulley system allow for an innovative blade kinematics. Indeed, the angle of attack of the blades is constant over a portion of their trajectory. This is a sought-after characteristics but difficult to obtain for conventional cross-flow turbines. 2D URANS k-ω SST simulations are carried out. Experimental data from an oscillating airfoil case are used to validate the numerical simulation process. The impact of solidity for one-blade turbine and the impact of the number of blades at isosolidity are studied. The unbalance performance between the upstream and downstream parts of the turbine are also investigated.

A simplified model or Actuator disc (AD) model is often used to simulate a river hydrokinetic turbine instead of using geometry-resolved simulations to reduce computing resources and time requirements. However, it is crucial to specify accurate momentum source terms in the simplified model to accurately produce the drag force and power performance of a turbine, and to produce the proper wake characteristics. Although the AD model works on axial-flow turbines, it is not readily to be applied to crossflow turbines to accurately predict the wake structure. This paper presents the validation of the effective performance turbine model (EPTM), which is a method to simplify numerical representation of cross-flow turbines. The implementation of the EPTM is discussed and comparisons to laboratory results are presented. In addition, the effects of various array configurations and blockage ratios on the wake and power performance were investigated with the goal of providing guidance in laying out hydrokinetic turbine projects in rivers., 14th European Wave and Tidal Energy Conference, EWTEC 2021, September 5-9, 2021, Virtual, Online

Experiments were performed with a large laboratory-scale high solidity cross-flow turbine to investigate Reynolds number effects on performance and wake characteristics and to establish scale thresholds for physical and numerical modeling of individual devices and arrays. It was demonstrated that the performance of the cross-flow turbine becomes essentially R e -independent at a Reynolds number based on the rotor diameter R e D ≈ 10 6 or an approximate average Reynolds number based on the blade chord length R e c ≈ 2 × 10 5 . A simple model that calculates the peak torque coefficient from static foil data and cross-flow turbine kinematics was shown to be a reasonable predictor for Reynolds number dependence of an actual cross-flow turbine operating under dynamic conditions. Mean velocity and turbulence measurements in the near-wake showed subtle differences over the range of R e investigated. However, when transport terms for the streamwise momentum and mean kinetic energy were calculated, a similar R e threshold was revealed. These results imply that physical model studies of cross-flow turbines should achieve R e D ∼ 10 6 to properly approximate both the performance and wake dynamics of full-scale devices and arrays.

This paper explores the influence of blockage and free-surface deformation on the hydrodynamic performance of a generic marine cross-flow turbine. Flows through a three-bladed turbine with solidity 0.125 are simulated at field-test blade Reynolds numbers, O (10 5 –10 6 ), for three different cross-stream blockages: 12.5, 25 and 50 per cent. Two representations of the free-surface boundary are considered: rigid lid and deformable free surface. Increasing the blockage is observed to lead to substantial increases in the power coefficient; the highest power coefficient computed is 1.23. Only small differences are observed between the two free-surface representations, with the deforming free-surface turbine out-performing the rigid lid turbine by 6.7 per cent in power at the highest blockage considered. This difference is attributed to the increase in effective blockage owing to the deformation of the free surface. Hydrodynamic efficiency, the ratio of useful power generated to overall power removed from the flow, is found to increase with blockage, which is consistent with the presence of a higher flow velocity through the core of the turbine at higher blockage ratios. Froude number is found to have little effect on thrust and power coefficients, but significant influence on surface elevation drop across the turbine.

International audience; Un concept de turbine bi-axiale estétudié par simulation numérique. Inspiré du principe des turbines Darrieus, les extrémités des pales de cette turbine sont en liaison cinématique avec une chaîne, elle-même reliéeà deux poulies de même rayon. Chaque pale a donc un mouvement de translation dans une direction orthogonaleà la vitesse d'écoulement amont sur une partie de sa trajectoire. L'angle d'incidence constant sur ces portions permet d'atteindre des rendementsélevés pour une turbineà axe transverse. Les simulations URANS k-ω SST sont réaliséesà l'aide de OpenFOAM®v2006. Un maillage dynamique de type overset est mis en place et permet d'imposer la cinématique de la pale. Une validation du procédé de simulation est faite par comparaison avec des données expérimentales et numériques d'un cas d'aile oscillante. L'influence de la solidité sur le coefficient de puissance moyen et instantanné estétudiée pour des turbines mono-pale, ce qui revientàétudier l'influence de la longueur de corde. Lorsque la solidité augmente, la vitesse optimale d'entraînement de pale diminue et le Cp instantané maximal augmente.

Straight-bladed cross-flow turbines are computationally explored for harvesting energy in wind and water currents. One challenge for cross-flow turbines is the transient occurrence of high apparent angles of attack on the blades that reduces efficiency due to flow separation. This paper explores kinematic manipulation of the apparent angle of attack through intracycle control of the angular velocity. Using an unsteady Reynolds-averaged Navier-Stokes (URANS) model at moderate Reynolds numbers, the kinematics and associated flow physics are explored for confined and unconfined configurations. The computations demonstrate an increase in turbine efficiency up to 54%, very closely matching the benefits shown by previous intracycle control experiments. Simulations display the time-evolution of angle of attack and flow velocity relative to the blade, which are modified with sinusoidal angular velocity such that the peak torque generation aligns with the peak angular velocity. With optimal kinematics in a confined flow there is minimal flow separation during peak power generation, however there is a large trailing edge vortex (TEV) shed as the torque decreases. The unconfined configuration has more prominent flow separation and is more susceptible to Reynolds number, resulting in a 41% increase in power generation under the same kinematic conditions as the confined flow., 21 pages, 13 figures, submitted to: AIAA Journal

This paper describes the design and fabrication of runner blades for cross flow turbine is presented. In this paper, the cross flow turbine's runner is designed to produce 100 W electric powers from head of 4 m and the flow rate of 0.004 m ^3 s. For the given capacity and head of the turbine, the dimensions of runner diameter and width 265 mm and 132 mm is obtained respectively. The detail design calculation of the runner is described in this thesis. It is applicable to wide range of flow rate adjusting the runner length. The term hydropower refers to shaft power generated by converting potential and kinetic energy of power. By using water power, the generation of electrical power is well known and widely used throughout the world. In hydropower plant, water turbine is one of the most important parts for generating electricity. This paper is to fulfill the required electricity in rural area. Ma Thu Zar Win | Ma Myat Win Khaing | Ma Yi Yi Khin "Design and Fabrication of Runner Blades of Cross-Flow Turbine" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd27990.pdf

Large-scale hydropower plants have major impacts on surrounding environment. This is mostly because of flooding land for the reservoir which destroys forests, wildlife habitat, agricultural, and scenic lands (Union of Concern Scientists [2015]: Environmental impacts of hydroelectric power). Small-scale hydropower systems, on the other hand, can be used as a much environmental choice especially for independent rural electrification. Dam or barrage requirements for mini and micro turbines are fairly small and water is stored in forebay tanks. However, financial considerations dictates utilisation of more efficient turbine technologies than currently available small-scale turbines can offer. Cross flow turbines (CFT) of small-scale hydropower plants are highly environmental considering their production and maintenance, but unfavoured due to their difficulty in achieving adequate and sustainable efficiency. Furthermore, maintaining power quality of micro hydropower stations with island operation setup is difficult. In this study, response surface methodology (RSM) is applied to investigate and identify the operating conditions of a micro cross flow turbine. A quadratic model is developed through RSM and an experimental setup of CFT is established to investigate the combined effects of flow rate, head and guide vane angle parameters on the turbine performance. RSM analyses are performed for 50 Hz constant frequency as optimal working condition. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1506–1511, 2015

Cross-flow turbines are very efficient and cheap turbines that allow a very good cost/benefit ratio for energy production located at the end of conduits carrying water from a water source to a tank. In this paper a new design procedure for a cross-flow turbine working with a variable flow rate is proposed. The regulation of the head immediately upstream the turbine is faced by adopting a shaped semicircular segment moving around the impeller. The maximum efficiency of the turbine is attained by setting the velocity of the particles entering the impeller at about twice the velocity of the rotating system at the impeller inlet. If energy losses along the pipe are negligible, the semicircular segment allows always a constant hydraulic head and a constant velocity at the impeller inlet, even with variable flow rate. The decrease of the turbine efficiency along with the inlet surface reduction is first investigated; a design methodology, using also CFD simulations, is then proposed for both the cases of negligible and not negligible energy losses along the pipe.

This study presents a numerical investigation of a generic horizontal axis cross-flow marine turbine. The numerical tool used is the commercial Computational Fluid Dynamics package ANSYS FLUENT 12.0. The numerical model, using the SST k-w turbulence model, is validated against static, dynamic pitching blade and rotating turbine data. The work embodies two main investigations. The first is concerned with the influence of turbine solidity (ratio of net blade chord to circumference) on turbine performance, and the second with the influence of blockage (ratio of device frontal area to channel crosssection area) and free surface deformation on the hydrodynamics of energy extraction in a constrained channel.Turbine solidity was investigated by simulating flows through two-, three- and four-bladed turbines, resulting in solidities of 0.019, 0.029 and 0.038, respectively. The investigation was conducted for two Reynolds numbers, Re = O(10^5) & O(10^6), to reflect laboratory and field scales. Increasing the number of blades from two to four led to an increase in the maximum power coefficient from 0.43 to 0.53 for the lower Re and from 0.49 to 0.56 for the higher Re computations. Furthermore, the power curve was found to shift to a lower range of tip speed ratios when increasing solidity.The effects of flow confinement and free surface deformation were investigated by simulating flows through a three-bladed turbine with solidity 0.125 at Re = O(10^6) for channels that resulted in cross-stream blockages of 12.5% to 50%. Increasing the blockage led to a substantial increase in the power and basin efficiency; when approximating the free surface as a rigid lid, the highest power coefficient and basin efficiency computed were 1.18 and 0.54, respectively. Comparisons between the corresponding rigid lid and free surface simulations, where Froude number, Fr = 0.082, rendered similar results at the lower blockages, but at the highest blockage an increase in power and basin efficiency of up to 7% for the free surface simulations over that achieved with a rigid lid boundary condition. For the free surface simulations with Fr = 0.082, the energy extraction resulted in a drop in water depth of up to 0.7%. An increase in Fr from 0.082 to 0.131 resulted in an increase maximum power of 3%, but a drop in basin efficiency of 21%.

Minimizing wake losses in wind or marine hydrokinetic (MHK) turbine arrays is a crucial design consideration, as it has a large impact on overall energy production. To understand and mitigate these losses, interactions between turbine wakes must be accurately predicted, with near-wakes being especially important for cross-flow (or vertical-axis) turbines, given their affinity for close-spaced operation. As numerical models become more accurate, validation efforts will need to take into account scale discrepancies between the numerical and physical models and their real-world applications. One such important scaling parameter is the Reynolds number, and it remains unclear what level of confidence can be placed in models validated away from full-scale Reynolds numbers. In other words, what is the minimum acceptable scale mismatch for experimental validation at which models can be said to be "accurate enough?" To address this uncertainty, we investigated—experimentally and numerically—the effects of Reynolds number on the performance and near-wake characteristics of a 3-bladed cross-flow turbine. Mechanical power output and overall streamwise drag were measured in a towing tank at turbine diameter Reynolds numbers ReD = U∞D/ν = 0.3–1.3 × 10⁶, with performance becoming essentially Reynolds number independent at ReD = 0.8 × 10⁶, corresponding to an average blade chord Reynolds number Rec ≣ λU∞c/ν ≈ 2.1 × 10⁵. Detailed measurements of the near-wake one turbine diameter downstream were acquired via acoustic Doppler velocimetry for each Reynolds number case, showing very slight differences in the mean velocity, turbulence intensity, and Reynolds stress at the turbine mid-height plane, i.e., the near-wake statistics were less Reynolds number dependent than the turbine performance. The wake was also simulated using a 2-D Reynolds-averaged Navier–Stokes (RANS) model. The performance results show poor agreement with the experimental data, due to 2-D blockage and the neglecting of blade end effects, however, an increase in performance with Re is predicted. The CFD predictions for wake characteristics are reasonably accurate on the side of the turbine where blades are turning back into the direction of the flow, or where dynamic stall is occurring, but Reynolds number dependence is much more exaggerated compared with the experimental data. National Science Foundation CAREER Award Leslie S. Hubbard Marine Program Fund U.S. Department of Energy

The cross-flow turbine is unique due to the generation of power during two stages. The water flows through the rectangular cross-section nozzle and enters the runner, where the first stage power is generated. The water then flows diametrically through the center of the runner, before it hits the blades on the way out, generating the second stage power. This type of turbine is often used in small hydropower plants located in less-developed countries. The turbine has a simple design, which is economical and easy to manufacture. A cross-flow turbine manufactured by Remote HydroLight in Afghanistan was installed in The Waterpower Laboratory at The Norwegian University of Science and Technology in September 2008. During the fall of 2008, efficiency measurements were performed on the turbine. A maximum efficiency of 78.6% was obtained at 5 meter head. However, although the efficiency is high for a turbine with such a simple design, there is a desire to improve it for better utilization of the resources. An open question is if the flow through the runner behaves like the manufacturers of this turbine type claim. It is therefore of interest to investigate the flow pattern through the runner and the distribution of torque transferred during the two stages. This is the objective of this thesis. Two experiments are performed in this thesis. The objective of the first experiment was to visualize the flow through the runner with use of a high-speed camera. This required an extensive remodeling of the turbine in order to obtain a clear view of the flow. However, the high--speed camera had to be replaced by a single-lens reflex camera and stroboscopes, due to low quality pictures. The second experiment measured the torque transfer to the runner by the use of strain gages. The strain gages could not be calibrated within the time frame of this thesis, but a relative measure of the distribution of torque was obtained. During both experiments the efficiency was measured, but the main objective was to determine the flow pattern and torque transfer through the runner. The results show that the turbine works well for large nozzle openings. The water enters the runner close to the nozzle outlet, leading to a cross flow entering the inside of the runner at a short distance from the nozzle. This gives good conditions for the flow, as the direction of the absolute velocity when entering the second stage corresponds well with the blade inlet angle. At best efficiency point the second stage contributes to 53.7% of the total amount of torque transferred. With decreasing nozzle opening, the cross flow enters the inside of the runner further away from the nozzle. This give a direction of the cross flow which corresponds poorly with the inlet angle of the blades at the second stage, which increases the incidence losses and gives a lower efficiency.

Flow in a cross water turbine is more difficult to calculate than that of other shaft symmetry inflow type turbines, because the flow in the runner, that enters non-symmetrically from a nozzle, is unsteady even it is observed on the relative coordinate system. And the free surface in the runner also makes the analysis difficult. In this study, the flow in the runner and nozzle is solved simultaneously on the basis of absolute coordinate system. This flow is assumed to be unsteady Euler's one, and is analysed by MAC method. The time marching is made using implicit method of Crank-Nicholson and a new method of boundary condition on walls is developed.

International audience

The present work reports CFD based investigation of the effect of design parameters on the flow velocities of a cross flow turbine (CFT). Best described as an impulse type turbine with partial admission of air, cross flow turbines meet the demand for an efficient turbine to run at low head that is also easy to manufacture. The design of cross–flow turbine is unique due to the generation of power during two stages. This type of turbine is often used in small hydropower plants located in less–developed countries. The design parameters of CFT that can be varied to increase overall efficiency and power output of the turbine are water inlet angle, blade angle at inlet and outlet. In the present work the design parameters are varied for different nozzle openings and simulated using CFD. A full 3-D steady state flow simulation of the cross-flow turbine is performed including casing, runner and nozzle assembly.

The potential energy hidden in water resources is becoming more and more a significant economic value. The value of the hydroelectric energy is often magnified by the proximity of the turbine to pumps or other energy sinks owned by the same water manager. Cross-flow or Banki-Michel turbines are a very efficient and economic choice that allows a very good cost/benefit ratio for energy production located at the end of conduits carrying water from a water source to a tank. In the paper the optimum design of a cross-flow turbine is sought after, assuming a flow rate variable in time. Regulation of the discharge entering in the turbine is a key issue, which is faced adopting a shaped semicircular segment, moved inside the main case around the rotating impeller. The maximum efficiency of the turbine is attained by setting the velocity of the particles entering the impeller at about twice the velocity of the rotating system at the impeller inlet. If energy losses along the pipe are negligible, closing and opening the inlet surface with the semicircular segment allows always a constant hydraulic head and a constant velocity at the impeller inlet, even with different flow rate entering values. Observed reduction of the turbine efficiency along with the inlet surface reduction is first investigated; a design methodology, using also CFD simulations, is then proposed; finally, the same methodology is applied to a real site in Sicily, selected in the context of the HYDROENERGY P.O. - F.E.S.R. European project.

Human activities have adversely affected the Earth’s habitable environment. Carbon emissions and other greenhouse gas emissions are the primary cause of climate change and ozone layer depletion. In addition, the exponential decay of fossil fuel resources has resulted in the rising demand for renewable and environmentally-friendly energy sources. Wave energy is the most consistent of all intermittent renewable energy sources and offers a promising solution to our energy needs. This study focuses on harnessing offshore wave energy resources, specifically targeting offshore conditions with the highest energy density. A novel direct drive cross-flow turbine with an improved augmentation channel shape was designed and analyzed using commercial computational fluid dynamics software. The turbine’s base model reached a maximum efficiency of 54.3%, with 33.4 kW of power output at 35 rev/min and a 3.0 m head. Bidirectional flow simulations were carried out, and the peak cyclic efficiency was recorded at 56.8% with a 36.4 kW average power output. The nozzle entry arc angle of 150 degrees was found to be the most efficient, and the numerical simulation’s fully developed solution computed the flow behavior through the runner and nozzle under steady-state conditions.

In the last few decades, hydropower production has been moving toward a new paradigm of low and diffused power density production of energy with small and mini-hydro plants, which usually do not require significant water storage. In the case of nominal power lower than 20 kW and ultra-low head H (H < 5 m), Archimedes screw or Kaplan type turbines are usually chosen due to their efficiency, which is higher than 0.85. A new cross-flow type turbine called Ultra-low Power Recovery System (UL-PRS) is proposed and its geometry and design criteria are validated in a wide range of operating conditions through 2D numerical analysis computed using the ANSYS Fluent solver. The new proposed solution is much simpler than the previously mentioned competitors; its outlet flow has a horizontal direction and attains similar efficiency. The costs of the UL-PRS turbine are compared with the costs of one Kaplan and one cross-flow turbine (CFT) in the case study of the main water treatment plant of the city of Palermo in Italy. In this case, the UL-PRS efficiency is estimated using a URANS 3D numerical analysis computed with the CFX solver.

Cross-flow turbines have recently been proposed for energy recovery in aqueducts when the outlet pressure is greater than zero, owing to their constructive simplicity and good efficiency within a large range of flow rates and head drops. In the case of high head drop (higher than 150 m) and relatively small discharge (lower than 0.2 m3/s), the traditional design of these turbines leads to very small widths of the nozzle and the runner; as a consequence, friction losses grow dramatically and efficiency drops down to very low values. Standard Pelton turbines require zero outlet pressure and cannot be used as alternatives. A new counter-pressure hydraulic turbine for high head and low flow rate, called the High Power Recovery System (H-PRS) is proposed. H-PRS presents a different geometry to reduce friction losses inside the nozzle and the runner by widening the two external walls. Several curved baffles are proposed to guide the fluid particles inside the nozzle and to guarantee the right velocity direction at the inlet surface of the runner. Computational Fluid Dynamics (CFD) 3D transient analyses are carried out to measure H-PRS efficiency for different operating conditions and to compute its characteristic curve for different positions of the regulating flap.

Hydraulic turbines for energy recovery in wastewater treatment plants, with relatively large discharges values and small head jumps, are usually screw Archimedes or Kaplan types. In the specific case of a small head jump (about 3 m) underlying a rectangular weir in the major Palermo (Italy) water treatment plant, a traditional Kaplan solution is compared with two other new proposals: a Hydrostatic Pressure Machine (HPM) located at the upstream channel and a cross-flow turbine (CFT) located in a specific underground room downstream of the same channel. The fluid mechanical formulations of the flow through these turbines are analyzed and the characteristic parameters are stated. Numerical analysis was carried out for the validation of the HPM design criteria. The efficiency at the design point of the CFT and HPM are estimated using the ANSYS CFX solver for resolution of 3D URANS analysis. The strong and weak points of the three devices are compared. Finally, a viability analysis is developed based on several economic indicators. This innovative study with a theoretical formulation of the most suitable turbomachine characterization, the potential energy estimation based on hydraulic energy recovery in a real case study of a wastewater treatment plant and the comparison of the three different low-head turbines, enhancing the main advantages, is of utmost importance towards the net-zero water sector decarbonization.

Hydraulic turbines for energy recovery in wastewater treatment plants, with relatively large discharges and small head jumps, are usually screw or Kaplan types. In the specific case of a small head jump (about 3 m) underlying a rectangular weir in the major Palermo (Italy) treat-ment plant, a traditional Kaplan solution is compared with two other ones: a Hydrostatic Pres-sure Machine (HPM) located in the upstream channel and a cross-flow turbine located in a specif-ic underground room downstream the same channel.

Kedung Kayang waterfall is located on the border of Magelang and Boyolali regency of Central Java. The waterfall is 38 meters high, so it has the potential to be used as a micro hydro power plant (MHP). In designing the MHP, it requires some studies including hydrology, civil, mechanical, and electrical. The purpose of this research is to predict the water discharge, determine the potential of hydro power, selection of MHP sites, design of hydro turbine and electric generator. This research uses Penman Modification method to calculate evapotranspiration, Mock method to calculate water discharge, geographical mapping for MHP sites selection and cross-flow turbine design calculation. This paper presents the results of MHP design consist of MHP capacity, selection of MHP sites, penstock design, cross-flow turbine design and electric generator selection. The result showed that dependable water discharge is 0.143 m3 / sec, effective head is 19.5 meters, hydro potential is 27.33 kW, and electric power that can be produced is 18 kW, length and diameter penstock are 81,74 m and 26,77 m, hydro turbine used cross flow type with outer diameter of the runner is 17,17 cm, inner diameter is 11,45 cm and width is 59,16 cm. MHP site is located in Klakah village, Selo Sub-district, Boyolali District.

Cross-flow hydrokinetic turbines have sparked interest among fluid dynamicists for their potential for power enhancement in paired configuration. Following the first part of a laboratory-scaled turbine wake measurement project, this second part presents a monoscopic particle image velocimetry measurement of the near-wake of two cross-flow hydrokinetic turbines in six different counter-rotating configurations. The turbines operated in a small water flume at an average diameter-based Reynolds number of 2×104 with the incoming streamwise velocity of 0.316 m/s. The six configurations included two turbine separation distances, two turbine phase angles differences, and two different relative incoming flow angles. Similar to the observation of the single turbine configurations in part I, a correlation between flow field structures and the corresponding power output was observed. Effects of each parameter of the counter-rotating configurations are further discussed, which suggest guidelines for setting up multiple devices in a power farm. This article is accompanied by all full numeric data sets and videos of the results.

Recent developments in marine hydrokinetic (MHK) technology have put the cross-flow (often vertical-axis) turbines at the forefront. MHK devices offer alternative solutions for clean marine energy generation as a replacement for traditional hydraulic turbines such as the Francis, Kaplan, and Pelton. Following previous power measurements of laboratory-scaled cross-flow hydrokinetic turbines in different configurations, this article presents studies of the water flow field immediately behind the turbines. Two independent turbines, which operated at an average diameter-based Reynolds number of approximately 0.2×105, were driven by a stepper motor at various speeds in a closed circuit water tunnel with a constant freestream velocity of 0.316 m/s. The wakes produced by the three NACA0012 blades of each turbine were recorded with a monoscopic particle image velocimetry technique and analyzed. The flow structures with velocity, vorticity, and kinetic energy fields were correlated with the turbine power production and are discussed herein. Each flow field was decomposed into the time averaged, periodic, and random components for all the cases. The results indicate the key to refining the existed turbine design for enhancement of its power production and serve as a baseline for future comparison with twin turbines in counter-rotating configurations.

International audience; Oscillating hydrofoils were installed in a water tunnel as a surrogate model for a hydrokinetic cross-flow tidal turbine, enabling the study of the effect of flexible blades on the performance of those devices with high ecological potential. The study focuses on a single tip-speed ratio (equal to 2), the key non-dimensional parameter describing the operating point, and solidity (equal to 1.5), quantifying the robustness of the turbine shape. Both parameters are standard values for cross-flow tidal turbines. Those lead to highly dynamic characteristics in the flow field dominated by dynamic stall. The flow field is investigated at the blade level using high-speed particle image velocimetry measurements. Strong fluid–structure interactions lead to significant structural deformations and highly modified flow fields. The flexibility of the blades is shown to significantly reduce the duration of the periodic stall regime; this observation is achieved through systematic comparison of the flow field, with a quantitative evaluation of the degree of chaotic changes in the wake. In this manner, the study provides insights into the mechanisms of the passive flow control achieved through blade flexibility in cross-flow turbines.

A cross-flow turbine was tested to determine the magnitude of the fluid forces on the blades. The tangential and radial forces and the torque were measured on a test blade. Because the runner was made of plexiglas, the flow and the effects of the incidence angle at various speeds were observed. The pattern of blade loading over a revolution was measured over a range of heads from 1.0 to 2.6 m. The maximum forces were found to occur just before the blade leaves the nozzle exit. The experimental forces agree reasonably well with the results of a control volume analysis. Two figures are provided, by which the designer may determine the tangential and radial forces for any geometrically similar machine. Master of Science

The Model of Fluid Dynamics Computation (CFD) aims to obtain cross-tubine flow in microhydro tubes. The parameters used to determine the cross flow turbine power are the blade angle, the number of cross runner blades and the head tube as the production house. Computational Fluid Dynamics (CFD) is software that can load integral and partial equations into discrete algebraic equations (addition, multiplication, multiplication and division) that can be used with the help of computers to find solutions for sources and times. In the era of technology, the development of the Computational Fluid Dynamics (CFD) program is very fast making this method a trend in various fields of industry that utilizes a comparison of pure experimental data and pure theory. The study of turbine cross flow power on microhydro tubes shows 1213 Watt power on the parameters of blade number 16, blade angle of 150 and 200 at head 4 meters.

Hydropower plants are a form of renewable energy resources, which comes from flowing water. The turbine is used to drive the generator then convert mechanical energy into electrical energy. The turbine wheel is located inside the turbine housing and the turbine wheel rotates the power shaft. One of the most used turbines is a cross-flow turbine. The pattern of water jet flowing throughout the empty space of the runner of the cross-flow turbine is influenced by the number of active runner blades pounded by water from the turbine nozzle. The difference in the flow patterns was believed having a relation to the performance differences of the three turbine models. The flow visualizations of water passing through the empty space of the cross-flow turbine runner were taken from the experimental study intended to investigate performance characteristics of three cross-flow turbine models designed on the same value of flow rates, runner diameters and rotational speeds; but each turbine model having different values of runner width as well as nozzle entry arc. Both of the nozzle and runner widths were designed as the function of the nozzle entry arc, therefore the shorter pair of runner-nozzle width the larger nozzle entry arc and vice versa. The flow visualizations of water passing on the turbine were studied using the empty space of the cross-flow turbine. The three models were tested on the same head and the same flow rate at the speed of 50, 100, 150, 250, 300 and 500 rpm. The photos of water flowing through the empty space in the turbine model runners were taken to find out the conditions of flow and the efficiency of the models was calculated to show the performance of the turbine. Images are taken within 10 cm and parallel to the turbine. The cross-flow turbine models were designed with 197 mm runner diameter of each and have the ratio of runner diameter to runner length of 1:2. One side of each turbine model end disk was made from transparent media named perspex facilitating the researcher to observe the water flow condition during flowing through inside the runner. The conditions of the flow of water passing through the empty space of turbine wheels were photographed using a Nikon camera equipped with a hallogen lamp having a power of 1000 watts to capture the difference of flow pattern among the three models of the turbine. The nozzle entry arcs used in this experimental study were 75o, 90o and 120o. In addition, the nozzle of each model has the same cross-sectional area and the roof of each was designed having roof curvature radius centered on the shaft axis. Such nozzle roof curvature was expected to be able to deliver water in the better direction as well as its flow condition as the water enters the turbine runner. The magnitude of the nozzle entry arc determines the number of active vanes pounded by the jet of water coming out of the nozzle, these conditions affect the pattern of water flow at the moment of passing through the empty space of the turbine wheel and then this flow pattern was believed to affect the performance characteristic of the cross-flow turbine. One side of each runner disk was made from Perspex, for the researcher to be able to observe the water flow condition during flowing through inside the runner., Гидроэлектростанции являются одной из форм возобновляемых источников энергии, поступающей из проточной воды. Турбина используется для запуска генератора и преобразования механической энергии в электрическую. Колесо турбины расположено внутри корпуса турбины и вращает приводной вал. Одной из наиболее распространенных турбин является турбина поперечного потока. На характер струи воды, протекающей через полость ротора турбины поперечного потока, влияет количество активных лопастей ротора, о которые бьется вода из сопла турбины. Считалось, что различие в характере потока связано с различиями в производительности трех моделей турбин. Визуализации потока воды, проходящей через полость ротора турбины поперечного потока, были взяты из экспериментального исследования рабочих характеристик трех моделей турбины поперечного потока, рассчитанных на одни и те же значения расхода, диаметров ротора и скоростей вращения, но каждая модель турбины имеет разные значения ширины ротора и дуги входа сопла. Ширина сопла и ротора рассчитана как функция дуги входа сопла, поэтому чем меньше ширина пары ротора и сопла, тем больше дуга входа сопла и наоборот. Визуализации потока воды, проходящей через турбину, были изучены с помощью полости турбины поперечного потока. Три модели были испытаны с одинаковым напором и с одинаковым расходом на скорости 50, 100, 150, 250, 300 и 500 об/мин. Были сделаны снимки воды, проходящей через полость роторов модели турбины, для определения условий потока, и была рассчитана эффективность моделей для отображения производительности турбины. Изображения сделаны в пределах 10 см и параллельно турбине. Модели турбины поперечного потока были спроектированы с диаметром ротора по 197 мм каждый и отношением диаметра ротора к длине ротора 1:2. Одна сторона каждого торцевого диска модели турбины была сделана из прозрачного материала Перспекс, что облегчало исследователю наблюдение за режимом потока воды во время протекания внутрь ротора. Условия потока воды, проходящей через полость турбинных колес, были сфотографированы с помощью камеры Никон, оснащенной галогеновой лампой мощностью 1000 Вт для фиксации разницы в характере потока между тремя моделями турбины. Дуги входа сопла, используемые в данном экспериментальном исследовании, составляли 75°, 90° и 120°. Кроме того, сопло каждой модели имеет одинаковую площадь поперечного сечения, а крышка имеет радиус кривизны, центрированный по оси вала. Ожидалось, что такая кривизна крышки сопла сможет доставлять воду в лучшем направлении, а также в режиме ее потока, когда вода поступает в ротор турбины. Величина дуги входа сопла определяет количество активных лопастей, о которые бьется струя воды, выходящая из сопла. Эти условия влияют на картину потока воды в момент прохождения через полость колеса турбины. Предполагалось, что данный режим потока влияет на рабочие характеристики турбины поперечного потока. Одна сторона каждого диска ротора была сделана из Перспекса, чтобы исследователь мог наблюдать за режимом потока воды во время прохождения внутрь ротора, Гідроелектростанції є однією з форм поновлюваних джерел енергії, що надходить з проточної води. Турбіна використовується для запуску генератора і перетворення механічної енергії в електричну. Колесо турбіни розташоване всередині корпусу турбіни і обертає привідний вал. Однією з найбільш поширених турбін є турбіна поперечного потоку. На характер потоку води, що протікає через порожнину ротора турбіни поперечного потоку, впливає кількість активних лопатей ротора, об які б'ється вода з сопла турбіни. Вважалося, що відмінність в характері потоку пов'язане з відмінностями в продуктивності трьох моделей турбін. Візуалізації потоку води, що проходить через порожнину ротора турбіни поперечного потоку, були взяті з експериментального дослідження робочих характеристик трьох моделей турбіни поперечного потоку, розрахованих на одні і ті ж значення витрати, діаметрів ротора і швидкостей обертання, але кожна модель турбіни має різні значення ширини ротора і дуги входу сопла. Ширина сопла і ротора розрахована як функція дуги входу сопла, тому чим менше ширина пари ротора і сопла, тим більше дуга входу сопла і навпаки. Візуалізації потоку води, що проходить через турбіну, були вивчені за допомогою порожнини турбіни поперечного потоку. Три моделі були випробувані з однаковим напором і з однаковим витратою на швидкості 50, 100, 150, 250, 300 і 500 об/хв. Були зроблені знімки води, що проходить через порожнину роторів моделі турбіни, для визначення умов потоку, і була розрахована ефективність моделей для відображення продуктивності турбіни. Зображення зроблені в межах 10 см і паралельно турбіні. Моделі турбіни поперечного потоку були спроектовані з діаметром ротора по 197 мм кожен і відношенням діаметра ротора до довжини ротора 1:2. Одна сторона кожного торцевого диска моделі турбіни була зроблена з прозорого матеріалу Перспекс, що полегшувало досліднику спостереження за режимом потоку води під час протікання всередину ротора. Умови потоку води, що проходить через порожнину турбінних коліс, були сфотографовані за допомогою камери Нiкон, оснащеної галогеновою лампою потужністю 1000 Вт для фіксації різниці в характері потоку між трьома моделями турбіни. Дуги входу сопла, що використовуються в даному експериментальному дослідженні, становили 75°, 90° і 120°. Крім того, сопло кожної моделі має однакову площу поперечного перерізу, а кришка має радіус кривизни, центрований по осі вала. Очікувалося, що така кривизна кришки сопла зможе доставляти воду в кращому напрямку, а також в режимі її потоку, коли вода надходить в ротор турбіни. Величина дуги входу сопла визначає кількість активних лопатей, об які б'ється струмінь води, що виходить з сопла. Ці умови впливають на картину потоку води в момент проходження через порожнину колеса турбіни. Передбачалося, що даний режим потоку впливає на робочі характеристики турбіни поперечного потоку. Одна сторона кожного диска ротора була зроблена з Перспекса, щоб дослідник міг спостерігати за режимом потоку води під час проходження всередину ротора

The epileptic power supply in most rural areas in Nigeria and its attendant negative impact on the economy of the Nation, Agricultural productivity and huge rural emigration, is a serious source of concern. This necessitated the development of two hydro-power turbines powered by the overflow (which was rather considered a waste) from University of Ilorin (UNILORIN) dam. A portion of the overflow was channeled into a Polyvinyl Chloride(PVC) pipe and the flow rate was calculated to be 0.017m3/sec using the bucket method. The change in elevation between the overflow and the point of usage was reported to be 4m. The flow (Q) and Head (h) were typical values for many streams and rivers in different rural areas of Nigeria, hence its suitability and adoption for this study. Two turbines viz: Pelton Wheel (PW) and Cross Flow (CF) were developed and tested. The PW generated a speed of 538.4rpm and a torque of 46.2kNm at off load condition while the CF generated a speed of 330.1rpm and a torque of 39.07kNm at the same condition. During loading – when the alternator had been connected to the turbine - the PW turbine speed and torque became 392.0rpm and 36.5kNm respectively, while that of the CF became 197.7rpm and 25.0kNm respectively. A belt and pulley mechanism was used to deliver the rotational speed to the alternator and this increased the alternator speed from the PW and CF turbines to 1768.6rpm and 879.24rpm respectively. The speed from the PW was enough to power the alternator as the alternator only requires 1500rpm to function optimally. The PW was thus adjudged the most suitable for use.

Hydrokinetic turbines, which convert the kinetic energy of flowing water into electrical energy, are increasingly being deployed in arrays, much like multiple wind turbines are commonly organized into a wind farm. Deploying multiple devices in an array can increase the amount of energy produced from a site and tends to make project economics more favourable. Despite growing interest in hydrokinetic turbine arrays, relatively few researchers have studied arrays and limited information exists concerning the character of the turbulent flows within arrays and methods for optimizing array layout, particularly for cross-flow turbines. This paper presents results from a set of experiments conducted in a current flume in which the wakes produced by a single cross-flow turbine and pairs of identical cross-flow turbines were measured in detail. Two different ambient turbulence intensities were studied so that the effect of turbulence level on wake recovery could be quantified. The velocity data has been analyzed to identify the mean velocity and the turbulence intensity in the turbine wake(s). These experiments form one component of a larger study that aims to develop numerical methods and guidelines to help project developers optimize the design of turbine arrays., On cover page: Marine Renewables Canada: 2018 Conference Proceedings, Marine Renewables Canada, Nov. 21-28, 2018, Halifax, Nova Scotia

The purpose of this experiment is to know the influence of a single guide vane position and angle to the performance of a cross-flow wind turbine. The cross-flow wind turbine was positioned at the discharge outlet of a cooling tower model to harness the discharged wind for electricity generation. A guide vane was used to enhance the rotational speed of the turbines for power augmentation. Various position and angle of attack of the guide vane were tested in this experiment. To avoid negative impact on the performance of the cooling tower fan and to optimize the wind turbine performance, the turbine position on the discharge wind stream was also studied. The result showed that cross-flow wind turbine with a guide vane attached at the right position had a higher coefficient of power than cross flow turbine without guide vane. A crossflow wind turbine with the guide vane at the position of 150 mm from the center and 30° angles had the highest coefficient of power of 0.49. Comparing to the wind turbine without guide vane, the coefficient of power of the cross-flow wind turbine was increased about 84.3%.

Efficiency and powerimprovement of cross-flow turbines harnessing rivers and ocean water energy isa key issue. Therefore, in this paper, we present the results of an experimental investigation on the effects of the blades orientation ona cross-flow water turbineperformance. Four similar test models (same dimensions and blades) bur for different blades orientation angle i = 1.75 °, 4.5 °, - 1.75 ° and - 4.5 ° have been tested to evaluate theperformance of this vertical axis water turbine (VAWT), for several water flow velocities V varying from0.3 to 0.59 m/s, which correspond to a water free flow Reynolds number of 2.08 104 to 4.36 104. An analysis of theseexperimental results has shown that the best performance (biggest power andpower coefficient) was obtained for the test model with its blades orientationangle set to 1.75 ° and the worst performance was given for the test model bladesorientation of -4.5 °. A comparison of the present results with those obtained in aprevious experimentation for a similar test model but with i = 0 °, has shown that the test model with its blades orientation angle fixed to1.75 °, furnished relative increases of optimum mechanical power and ofcorresponding power coefficient respectively as much as 82 % and 67 % withrespect to the results for i = 0 °, at a flow velocity equal to 0.37 m/s.While, the test model, with negative angle of -4.5 °, gave smaller generatedpower and power coefficient with corresponding relative decreases of about 49 %and 36 % with respect to those obtained for the test model with its bladesfixed at 0 °.

This paper is the third of three, which describe the procedures and results for a set of experiments on various configurations of the Transverse Horizontal Axis Water Turbine (THAWT), which is a horizontally orientated variant of the Darrieus cross-flow turbine. Tests were conducted in the combined wind, wave and current tank at Newcastle University on a 0.5 m diameter rotor, while the flow depth and velocity were varied over a range of realistic Froude numbers for tidal streams. Various configurations of the device were tested to assess the merits of varied blade pitch, rotor solidity, blockage ratio and truss oriented blades. Experiments were carried out using a speed-controlled motor/generator, allowing quasi-steady results to be taken over a range of tip speed ratios. Measurements of power, thrust, blade loading and free surface deformation provide extensive data for future validation of numerical codes and demonstrate the ability of the device to exceed the Lanchester-Betz limit for kinetic efficiency by using high blockage. This paper covers the instrumentation, hydrodynamic performance and loading of the truss bladed variant of the THAWT device. The first paper covers the experimental setup and hydrodynamic performance of the parallel bladed rotor and the second paper covers the instrumentation and hydrodynamic loading of the parallel bladed rotor. © 2013 Elsevier Ltd.

This paper is the second of three, which outline the procedures and results for a set of experiments on various configurations of the Transverse Horizontal Axis Water Turbine (THAWT), which is a horizontally orientated variant of the Darrieus cross-flow turbine. Tests were conducted in the combined wind, wave and current tank at Newcastle University on a 0.5m diameter rotor, while the flow depth and velocity were varied over a range of realistic Froude numbers for tidal streams. Various configurations of the device were tested to assess the merits of varied blade pitch, rotor solidity, blockage ratio and truss oriented blades. Experiments were carried out using a speed controlled motor/generator, allowing quasi-steady results to be taken over a range of tip speed ratios. Measurements of power, thrust, blade loading and free surface deformation provide extensive data for future validation of numerical codes and demonstrate the ability of the device to exceed the Lanchester-Betz limit for kinetic efficiency, by exploiting high blockage. This second paper covers the instrumentation and analysis for the structural loading for the parallel bladed variant of the THAWT device. The first paper covers the experimental setup and hydrodynamic performance of the parallel bladed rotor, and the third paper covers both performance and loading of the truss configured THAWT device. © 2013 Elsevier Ltd.

This paper is the first of three, which outline the procedures and results for a set of experiments carried out on various configurations of the Transverse Horizontal Axis Water Turbine (THAWT), which is a horizontally orientated variant of the Darrieus cross-flow turbine. Tests were conducted in the combined wind, wave and current tank at Newcastle University on a 0.5 m diameter rotor, while the flow depth and velocity were varied over a range of realistic Froude numbers for tidal streams. Various configurations of the device were tested to assess the merits of varied blade pitch, rotor solidity, blockage ratio and truss oriented blades. Experiments were carried out using a speed controlled motor/generator, allowing quasi-steady results to be taken over a range of tip speed ratios. Measurements of power, thrust, blade loading and free surface deformation provide extensive data for future validation of numerical codes and demonstrate the ability of the device to exceed the Lanchester-Betz limit for kinetic efficiency by using high blockage. This paper covers the experimental procedures and results for the hydrodynamic performance for the parallel bladed variant of the THAWT device. The second paper covers the hydrodynamic loading of the parallel bladed rotor and the third covers both hydrodynamic performance and loading of the truss configured THAWT device. © 2013 Elsevier Ltd.

A numerical and experimental study was carried out for validation of a previously proposed design criterion for a cross-flow turbine and a new semi-empirical formula linking inlet velocity to inlet pressure. An experimental test stand was designed to conduct a series of experiments and to measure the efficiency of the turbine designed based on the proposed criterion. The experimental efficiency was compared to that from numerical simulations performed using a RANS model with a shear stress transport (SST) turbulence closure. The proposed semi-empirical velocity formula was also validated against the numerical solutions for cross-flow turbines with different geometries and boundary conditions. The results confirmed the previous hydrodynamic analysis and thus can be employed in the design of the cross-flow turbines as well as for reducing the number of simulations needed to optimize the turbine geometry.

The dissertation investigates the approach of open source hardware and its potential for a “post-growth” transformation of society, which, from an environmentalist perspective, seems necessary. Hereby it elaborates the paradigm shift attached to the idea of open source, compares them with living systems in nature and practically contributes to the open source movement in the field of rural electrification. By doing so, it compares renewable energy technologies for rural electrification from the perspective of open source applicability. The practical output hereby is the design of an open source licensed hydro power turbine, called “Pico Cross Flow”. The dissertation covers the hydraulic and mechanical design as well as the manufacturing of a prototype and the testing at the hydrodynamic laboratory of the University of Viena, La disertación investiga la idea de “open source hardware” (hardware de código abierto) y su potencial para una transformación social de "post-capitalismo", la cual, desde una perspectiva ambientalista, parece necesaria. Se elabora el cambio de paradigma asociado a las ideas de código abierto, se compara con los sistemas vivos en la naturaleza y prácticamente contribuye al movimiento de fuente abierta (open source) en el campo de la electrificación rural. El resultado práctico es el diseño de una turbina hidroeléctrica licenciado código abierto, denominada "Pico Cross Flow". La parte práctica de la disertación abarca el diseño hidráulico y mecánico, así como la fabricación de un prototipo y las pruebas en el laboratorio hidrodinámico de la Universidad de Viena.

This paper presents theoretical results of flow simulations, performed on cross-flow type turbine of 8.25 kW, and also the results obtained on the improved turbine, with modified shapes for the rotor, case, and guiding palette.

Adaptive control strategies utilizing preview information of upstream velocity are promising approaches for enhancing performance and reducing loads on hydrokinetic turbines. A control scheme relating a turbine's characteristic performance curve and rotation rate to an optimal torque setpoint is implemented experimentally and in simulation for a laboratory‐scale helical cross‐flow turbine. Energy extraction performance for schemes employing adaptive/preview techniques is compared to performance under constant speed and non‐adaptive control. Results in simulation indicate significant improvement over constant speed operation and modest improvement over non‐adaptive strategies. Experimental results for adaptive strategies are comparable to non‐adaptive strategies, due to uncertainty in instantaneous performance curves. U.S. Department of Energy University of Washington Royalty Research Fund

Sandia National Laboratories recently released an open source code for design and analysis of axial‐flow and cross‐flow marine and hydrokinetic (MHK) turbines, CACTUS (Code for Axial and Cross‐flow TUrbine Simulation), and has initiated an outreach effort to promote its use among MHK researchers and developers. Our aim in this paper is to summarize the recent developments in CACTUS, and present model performance evaluation results that demonstrate CACTUS's potential use as a design and optimization tool for marine hydrokinetic turbines. We present several model validation tests to evaluate the model's ability to predict MHK turbine performance. The results show both the potential use of CACTUS as a design tool and its current limitations. At least two more model validation tests are planned for 2014 as part of this effort: scaled model tests of DOE's Reference Model 1(RM1) and Reference Model 2 (RM2) turbines in 2014 at the University of Minnesota's St. Anthony Falls Laboratory (SAFL). U.S. Department of Energy Wind and Water Power Program

With key applications in marine renewable energy. the vertical axis water turbine can use current or tidal energy in an eco-friendly manner. However, it is difficult to reconcile optimal performance of hydrokinetic turbines and compliance wilh the aquatic environment as the main drawback of the turbines is the formation of non-linear flow structures caused by the unsteady movement of the blades. Eddies in the flow are advected and can interact with other blades, which leads to a reduction in power output. To limit this phenomenon, the turbines operate at high speeds, which are likely to reduce the shaft power. High speeds of rotational so forbid the passage of aquatic animais, and are the cause of a suction effect on the sediments.The objective of this thesis work is twofold. First, it aims to develop a blade pitch control to get the flow adjusted around the blade profile at any given flow configuration by incorporatin.g the profile's motion with respect to incident flow. Such a system intends to achieve the objective of operating at reduced speeds without vortical releases, which should allow achieving a high torque without causing damage to the environment.This thesis work is mainly carried out in three phases. ln the first phase, the irrotational flow over an arbitrary profile is formulated using conforma] mapping. Prospective potential flow application on the basis of Couchet theory (1976) is involved in the development of a control law that decides the blade pitching in a constant circulation framework. In the second phase, a numerical validation of the developed analytical work is presented using CFD to examine how the theoretical fomulation can be effectively applied to Darricus turbines. In the final phase, two prototypes are developed, one is classical Darrieus turbine with fixed blades, and other is the turbine with pitching blades for experimental measurements of performance as well as flow fields(by PIV) in order to validate the computational results.; L'étude développée dans cette thèse concerne le contrôle des performances et des lâchers tourbillonnaires au cours du cycle de rotation d'une hydrolienne à axe vertical de type Darrieus. L'élaboration d'une famille de lois de commande d'incidence de pales exploitant le principe de conservation de la circulation autour de profils en mouvement permet ici le contrôle du fonctionnement de l'hydrolienne ainsi que la maîtrise de son sillage tourbillonnaire afin de préserver l'environnement.L'écoulement 2D est simulé à l'aide du solveur incompressible de Star CCM+ afin de mettre en évidence l'effet de ce type de contrôle sur le rendement de la turbine pour différents points de fonctionnement. Ce modèle CFD a été utilisé pour améliorer l'analyse analytique en ce qui concerne l'extraction de l'énergie, la compréhension de l'écoulement autour de l'hydrolienne et le contrôle des tourbillons générés. La nouveauté de cette étude est l'élaboration de lois de commande de pales d'hydrolienne, basées sur des valeurs constantes et transitoires de la circulation, afin d'augmenter la puissance de la turbine tout en garantissant un contrôle efficace de la vorticité et ainsi prévenir de l'interaction entre les tourbillons et les pales. Une bonne comparaison est réalisée entre les résultats analytiques et numériques concernant les forces hydrodynamiques.En outre, une campagne d'essais a été menée afin d'acquérir des mesures quantitatives sur une hydrolienne de type Darrieus à pales fixes en terme de puissance, mais aussi des résultats qualitatifs pertinents comme la visualisation de l'écoulement autour des pales à différentes positions et pour différents points de fonctionnement. La mise en place complète d'un système PTV pour les mesures qualitatives et les étapes de traitement sont discutées et les divers paramètres obtenus à partir des études CFD sont validées en utilisant ces résultats PIV.L'étude expérimentale dans la présente recherche appo11e des informations détaillées sur les gradients de pression et de vitesse, les contours de vorticité et le critère Q qui ont servi à valider les visualisations obtenues numériquement.

With key applications in marine renewable energy. the vertical axis water turbine can use current or tidal energy in an eco-friendly manner. However, it is difficult to reconcile optimal performance of hydrokinetic turbines and compliance wilh the aquatic environment as the main drawback of the turbines is the formation of non-linear flow structures caused by the unsteady movement of the blades. Eddies in the flow are advected and can interact with other blades, which leads to a reduction in power output. To limit this phenomenon, the turbines operate at high speeds, which are likely to reduce the shaft power. High speeds of rotational so forbid the passage of aquatic animais, and are the cause of a suction effect on the sediments.The objective of this thesis work is twofold. First, it aims to develop a blade pitch control to get the flow adjusted around the blade profile at any given flow configuration by incorporatin.g the profile's motion with respect to incident flow. Such a system intends to achieve the objective of operating at reduced speeds without vortical releases, which should allow achieving a high torque without causing damage to the environment.This thesis work is mainly carried out in three phases. ln the first phase, the irrotational flow over an arbitrary profile is formulated using conforma] mapping. Prospective potential flow application on the basis of Couchet theory (1976) is involved in the development of a control law that decides the blade pitching in a constant circulation framework. In the second phase, a numerical validation of the developed analytical work is presented using CFD to examine how the theoretical fomulation can be effectively applied to Darricus turbines. In the final phase, two prototypes are developed, one is classical Darrieus turbine with fixed blades, and other is the turbine with pitching blades for experimental measurements of performance as well as flow fields(by PIV) in order to validate the computational results.; L'étude développée dans cette thèse concerne le contrôle des performances et des lâchers tourbillonnaires au cours du cycle de rotation d'une hydrolienne à axe vertical de type Darrieus. L'élaboration d'une famille de lois de commande d'incidence de pales exploitant le principe de conservation de la circulation autour de profils en mouvement permet ici le contrôle du fonctionnement de l'hydrolienne ainsi que la maîtrise de son sillage tourbillonnaire afin de préserver l'environnement.L'écoulement 2D est simulé à l'aide du solveur incompressible de Star CCM+ afin de mettre en évidence l'effet de ce type de contrôle sur le rendement de la turbine pour différents points de fonctionnement. Ce modèle CFD a été utilisé pour améliorer l'analyse analytique en ce qui concerne l'extraction de l'énergie, la compréhension de l'écoulement autour de l'hydrolienne et le contrôle des tourbillons générés. La nouveauté de cette étude est l'élaboration de lois de commande de pales d'hydrolienne, basées sur des valeurs constantes et transitoires de la circulation, afin d'augmenter la puissance de la turbine tout en garantissant un contrôle efficace de la vorticité et ainsi prévenir de l'interaction entre les tourbillons et les pales. Une bonne comparaison est réalisée entre les résultats analytiques et numériques concernant les forces hydrodynamiques.En outre, une campagne d'essais a été menée afin d'acquérir des mesures quantitatives sur une hydrolienne de type Darrieus à pales fixes en terme de puissance, mais aussi des résultats qualitatifs pertinents comme la visualisation de l'écoulement autour des pales à différentes positions et pour différents points de fonctionnement. La mise en place complète d'un système PTV pour les mesures qualitatives et les étapes de traitement sont discutées et les divers paramètres obtenus à partir des études CFD sont validées en utilisant ces résultats PIV.L'étude expérimentale dans la présente recherche appo11e des informations détaillées sur les gradients de pression et de vitesse, les contours de vorticité et le critère Q qui ont servi à valider les visualisations obtenues numériquement.

This paper presents analytical bounds for blade–wake interaction phenomenona occurring in rotating cross-flow turbines for wind and tidal energy generation (e.g. H-rotors, Darrieus or vertical axis). Limiting cases are derived for one bladed turbines and extended to the more common three bladed configuration. Additionally, we present a classification of the blade–wake type of interactions in terms of limiting tip speed ratios. These bounds are validated using a high order h / p Discontinuous Galerkin solver with sliding meshes. This computational method enables highly accurate flow solutions and shows that the analytical bounds correspond to limiting blade–wake interactions in fully resolved flow simulations.

In hydropower, the exploitation of small power sources requires the use of small turbines that combine efficiency and economy. Banki-Michell turbines represent a possible choice for their simplicity and for their good efficiency under variable load conditions. Several experimental and numerical tests have already been designed for examining the best geometry and optimal design of cross-flow type machines, but a theoretical framework for a sequential design of the turbine parameters, taking full advantage of recently expanded computational capabilities, is still missing. To this aim, after a review of the available criteria for Banki-Michell parameter design, a novel two-step procedure is described. In the first step, the initial and final blade angles, the outer impeller diameter and the shape of the nozzle are selected using a simple hydrodynamic analysis, based on a very strong simplification of reality. In the second step, the inner diameter, as well as the number of blades and their shape, are selected by testing single options using computational fluid dynamics (CFD) simulations, starting from the suggested literature values. Good efficiency is attained not only for the design discharge, but also for a large range of variability around the design value.

The paper refers to the numerical analysis of the internal flow in a hydraulic cross-flow turbine type Banki. A 3D-CFD steady state flow simulation has been performed using ANSYS CFX codes. The simulation includes nozzle, runner, shaft, and casing. The turbine has a specific speed of 63 (metric units), an outside runner diameter of 294 mm. Simulations were carried out using a water-air free surface model and k-εturbulence model. The objectives of this study were to analyze the velocity and pressure fields of the cross-flow within the runner and to characterize its performance for different runner speeds. Absolute flow velocity angles are obtained at runner entrance for simulations with and without the runner. Flow recirculation in the runner interblade passages and shocks of the internal cross-flow cause considerable hydraulic losses by which the efficiency of the turbine decreases significantly. The CFD simulations results were compared with experimental data and were consistent with global performance parameters.

Modern wind farms comprised of horizontal-axis wind turbines (HAWTs) require significant land resources to separate each wind turbine from the adjacent turbine wakes. This aerodynamic constraint limits the amount of power that can be extracted from a given wind farm footprint. The resulting inefficiency of HAWT farms is currently compensated by using taller wind turbines to access greater wind resources at high altitudes, but this solution comes at the expense of higher engineering costs and greater visual, acoustic, radar and environmental impacts. We investigated the use of counter-rotating vertical-axis wind turbines (VAWTs) in order to achieve higher power output per unit land area than existing wind farms consisting of HAWTs. Full-scale field tests of 10-m tall VAWTs in various counter-rotating configurations were conducted under natural wind conditions during summer 2010. Whereas modern wind farms consisting of HAWTs produce 2 to 3 watts of power per square meter of land area, these field tests indicate that power densities an order of magnitude greater can potentially be achieved by arranging VAWTs in layouts that enable them to extract energy from adjacent wakes and from above the wind farm. Moreover, this improved performance does not require higher individual wind turbine efficiency, only closer wind turbine spacing and a sufficient vertical flux of turbulence kinetic energy from the atmospheric surface layer. The results suggest an alternative approach to wind farming that has the potential to concurrently reduce the cost, size, and environmental impacts of wind farms., In press at Journal of Renewable and Sustainable Energy