Search

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.

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.

An experimental investigation was conducted to study the effects of some geometric parameters of runners and nozzles (e.g., diameter ratio and throat width ratio) on the efficiency in the cross-flow turbines, by varying of ratio of inner-to-outer diameters of runners and gate openings of two different turbine nozzles under different heads. In this study, four different types of runners (170 mm outer diameter, 114 mm width) were designed and manufactured to investigate the effects of the ratio of inner-to-outer diameters of runners on the turbine efficiency. Each runner had 28 blades and the ratios of inner-to-outer diameters of runners were 0·75, 0·67, 0·58 and 0·54, respectively. The runners were denoted with the numbers 1, 2, 3 and 4, and nozzles A and B. The blade inlet and outlet angles were selected as 30° and 90°. Nozzles A and B were of rectangular cross-sectional channels. Nozzles outlet angles of two solid walls of 16° were measured from the circumferential direction. The performance parameters namely output power, efficiency, runaway speed, reduced speed and power for different nozzle/runner combinations were investigated by changing head range from 8 to 30 m, the nozzle A-runner combinations (A–1, 2, 3, 4) and from 4 to 17 m, the nozzle B-runner combination (B–2) at different gate openings. The results of the present study clearly indicated that there was a negligible difference (e.g., 3% in total between 0·54 and 0·75 diameter ratio) in the efficiency of turbine for different diameter ratios and heads, and that the highest efficiency was obtained as 72% for A–2. © 1998 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this work, an experimental analysis of the performance of a cross-flow turbine, commonly referred to as a Michell–Banki turbine (MBT), is carried out for small-scale hydropower production in rural areas located in developing countries to support their social and economic development activities. The study investigates how the efficiency of the MBT is influenced by the presence or absence of a nozzle, along with variations in the internal guide vane (GV) and its angle. The runner had 26 blades that were arranged symmetrically in the periphery between two circular plates. The designed MBT had the ability to generate a maximum of 100 W of power at a water flow rate and a head of 0.009 m3/s and 0.6311 m, respectively. The experimental tests were carried out using a hydraulic bench. The turbine efficiency without the inner GV was found to be higher than that of the turbine with the inner GV; i.e., it was found that the utilization of the GV did not enhance the efficiency of the MBT due to the occurrence of a choking effect. A maximum hydraulic efficiency of 85% was achieved in the turbine without an inner GV in comparison with the efficiency achieved (77%) with this device and an optimum opening angle of the GV of 24° (75% of opening). In this regard, the GV design should be carefully carried out to improve the MBT efficiency. Additionally, the effect of the GV shape on the MBT performance should be experimentally investigated to obtain a more general judgment regarding the role of this device. [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

Most of the major micro hydro power plants in Nepal uses Crossflow turbine for power generation which are manufactured locally. However, efficiency of these turbines has not been tested and verified. In this research, Cross flow turbine designs were obtained from local manufacturers. Efficiencies of these turbines were determined using simulation under steady state condition. Efficiencies were verified using the data from the installation site where these designs were used. Different Cross flow turbine models were prepared by varying the curvature radius of the blade and the ratio of inner to outer radius of the runner. The efficiencies of such models were determined using simulation. [ABSTRACT FROM AUTHOR]

Cross-flow turbine is one of the leading turbines to harness the hydropower potential in micro-hydro power schemes. In spite of having a simple structure, low maintenance, and low initial investment, this turbine suffers the problem of low efficiency due to unguided flow in the runner cavity. In the present study, an attempt has been made to enhance the performance of cross-flow turbine by attaching hydrofoils shaped (symmetrical and unsymmetrical) guiding mechanism. The effectiveness of the placement of guide vane was examined numerically in terms of turbine efficiency and flow field distributions. The performance of the modified turbine was compared with the turbine having no guide vane. The position and placement angle of the guide vanes were also investigated to find the suitable position of the guide vane in the runner cavity. The turbine with symmetrical and unsymmetrical guide vane yields its maximum efficiency corresponding to vane angle of 55° and 45°, respectively, placed at the 'right' position (toward nozzle) for both types of guide vanes. The maximum efficiency of the turbine was observed as 80.1% and 79.9% corresponding to symmetrical and unsymmetrical guide vanes, respectively. Further, the flow field distribution inside the turbine runner and in the vicinity of the guide vane has been observed. It has been visualized that placement of the guide vane minimizes the water recirculation with the streamlined flow for smooth entry to the second stage of the runner. The reduction in turbulence and vortices generation results in the improvement of turbine efficiency for similar operating conditions. [ABSTRACT FROM AUTHOR]

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.

An open-source 2D Reynolds-averaged Navier–Stokes (RANS) simulation model was presented and applied for a laboratory-scaled cross-flow hydrokinetic turbine and a twin turbine system in counter-rotating configurations. The computational fluid dynamics (CFD) model was compared with previously published experimental results and then used to study the turbine power output and relevant flow fields at four blockage ratios. The dynamic stall effect and related leading edge vortex (LEV) structures were observed, discussed, and correlated with the power output. The results provided insights into the blockage effect from a different perspective: The physics behind the production and maintenance of lift on the turbine blade at different blockage ratios. The model was then applied to counter-rotating configurations of the turbines and similar analyses of the torque production and maintenance were conducted. Depending on the direction of movement of the other turbine, the blade of interest could either produce higher torque or create more energy loss. For both of the scenarios where a blade interacted with the channel wall or another blade, the key behind torque enhancement was forcing the flow through its suction side and manipulating the LEV.

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.

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.

While studies on horizontal axis tidal turbines are plentiful, those on ducted twin vertical axis alike HydroQuest's turbines are lacking. For such a device, both the relative counter-rotation direction of the rotors and the tripod base geometry upstream are different between ebb and flood tide. Consequently, this paper analyses the effect of the two opposed flow directions on the hydrodynamic performance and on the wake of the turbine. The study is based on experimental measurements at a 1/20th scale in Ifremer's wave and current flume tank. The hydrodynamic performance of the model are characterised over a wide range of operating points with the turbine installed on a tripod and on a monopile base. In addition, the 3D wake of the turbine is thoroughly analysed in the two flow directions using 3-component laser Doppler velocimetry. Overall, the drag and the maximum average power coefficient are not affected by the current direction but the optimal tip speed ratio is 7 % lower during ebb with 1.5 times higher power fluctuations compared to flood tide. Besides, the wake of the two rotor columns interact differently depending on the flow direction, leading to a 30 % faster surface averaged velocity recovery in the flood tide configuration. The observed effect of flow direction provides a better knowledge of twin vertical axis turbine wake interactions and highlights the impact of the gravity base geometry on the development of the overall turbine wake. This paper also provides a wide experimental database for the validation of numerical models applied to ducted twin-vertical axis tidal turbines. • Ebb and flood tides modelled experimentally in a tank by turning the turbine around. • Twin vertical axis turbine (2-VATT) mean power is barely affected by the flow direction. • Gravity based 2-VATT power fluctuation and wake development depend on base geometry. • Rotors wake merging distance and recovery depend on the counter-rotation direction. [ABSTRACT FROM AUTHOR]

With the aim of finding efficient solutions for cross flow turbine (CFT) bi-directional diffusers able to harvest non perfectly rectilinear tidal currents, a 2D CFD analysis of ducted CFTs was carried out with focus on the effects of diffuser shape and yaw angle. The HARVEST hydrofoil shaped diffuser, equipped with a pair of counter-rotating turbines, and a bi-directional symmetrical diffuser were compared in terms of coefficient of power (CP), torque ripple, overall thrust on diffuser and wake characteristics. Slightly better CP were predicted for the symmetrical diffuser, due to the convergent walls that address the flow towards the blade with a greater attack angle during early and late upwind and to the viscous interactions between the turbine wakes and strong vortices shed by the diffuser. A CP’s extraordinary improving resulted when yaw increased up to 22.5° for the hydrofoil shaped and up to 30° for the symmetrical diffuser. Similar behaviour in yawed flows also occurred in case of a ducted single rotor, demonstrating that it is a characteristic of CFTs. The insertion of a straight throat in the diffuser design proved to be an effective way to mitigate torque ripple, but a CP loss is expected.

This article proposes an experimental apparatus design to measure the power of a cross-flow marine hydrokinetic turbine system operating in a laboratory water tunnel. Data, from one Hall sensor output signal, was processed to capture the three types of torque exerted on the turbines: mechanical loss, brake, and hydrodynamic torque. The method was then applied to compare the power of a twin turbine system in different counter-rotating configurations. Controlled by a hysteresis brake, the tip-speed-ratio was varied in a constant freestream velocity of 0.316 m/s. While the braking torque was independent of the speed, the mechanical loss was found to depend on the system rotational speed and the amount of mass mounted on the mechanical support. In a counter-rotating configuration, the turbines were synchronized through a pair of spur gears and timing pulleys. Operating at the average chord based Reynolds number of 8000, each turbine had three NACA0012 blades mounted at 15∘ pitch angle. The power coefficient results of 8 turbine configurations showed the tendency of power enhancement of counter-rotating configurations due to blade interaction and increase in blockage ratio. Comparison of the results suggested direct application in a river flow scenario and manipulation of the blade interaction for optimal power production.

The cross-flow turbines cover from the point of view hydraulic power the running domain of some well-known turbines such as Pelton, Francis or Kaplan. This type of turbine has a simple construction, long life and low execution cost, which makes it very suitable for on and off grid small to medium hydro power plants. It is quite difficult to establish an exact theoretical dynamic model for this type of turbines, due to the complex flow phenomenon (bi phase flow water and air). In order to obtain the exact dynamic behavior of the hydraulic machine, experimental dynamic identification will be done. In automation, the dynamic properties, represent the fundamental characteristic of the object which must be regulated. When the dynamic properties of the regulated object are obtained experimentally, we analyze the characteristics of the transient regime, which appears because of the application at the system inlet of some stochastic or deterministic signals (sine waves for our case). The hydraulic turbine is modeled as an informational quadrupole having the inlet parameters the movement of the wicket gate and the turbine head and outlet parameters the torque and the speed. In this paper it will be presented the frequency modelling of the cross-flow turbine and the validation of the mathematical model through experimental dynamic identification. [ABSTRACT FROM AUTHOR]

A cross-flow wind turbine has a high torque coefficient at a low tip speed ratio; therefore, it is a good candidate for a self-starting turbine. This study aims to investigate the best configuration between guide vanes and cross-flow vertical axis wind turbine. The experiment test was carried out to determine the turbine with the highest power coefficient. The cross-flow turbine has 14, 18, and 22 blades with using 6,10 and 14 blades of guide vane (GV) was developed in this study, employing 15°, 25°, 35°, 45°, 55°, 65°, and 75° of tilt angles in fifth different wind speed conditions 4 m/s, 6 m/s, 7.5 m/s, 9.20 m/s, and 11 m/s. The turbine has 22 blades with 14 GV blades at 55° of tilt angle blades producing more remarkable turbine performance improvement than other blades. The highest power coefficient (CP) of cross-flow using 14 GV blades at 55° was 0.0162 at 0.289 TSR, which increased around 59% of the turbine's performance using GV. [ABSTRACT FROM AUTHOR]

The aim of this investigation is to develop an open type cross-flow turbine for environmental friendly nano-hydraulic turbine utilizing extra-low head waterfall. A relative position between the runner and the waterfall is one of the important factors for turbine efficiency. More often, it is necessary to precisely adjust this distance according to changes of the flow rate. In this study, we focused on the influence of the horizontal and vertical position of the runner on performance. First, the effect on the performance of the horizontal relative position between the runner and the falling water is verified. Next, two condition of the vertical relative position are concerned; one is the clearance between the runner and the water surface of the pool, the other is that between the runner and the solid surface as the runner placed closer to the ground or the riverbed. The result highlights that the horizontal relative position was an effect on the power performance. When the solid surface is presented under the runner, the performance is not effected when the water thickness is equivalent to 7.5% or more. On the other hand, when water surface is presented below the runner, the clearance between them has insignificant effect on the performance even though the runner underside is partly submerged. [ABSTRACT FROM AUTHOR]

Recently, small hydropower attracts attention because of its clean, renewable and abundant energy resources to develop. Therefore, a cross-flow hydraulic turbine is proposed for small hydropower in this study because the turbine has relatively simple structure and high possibility of applying to small hydropower. The purpose of this study is to investigate the effect of the turbine's structural configuration on the performance and internal flow characteristics of the cross-flow turbine model using CFD analysis. The results show that nozzle shape, runner blade angle and runner blade number are closely related to the performance and internal flow of the turbine. Moreover, air layer in the turbine runner plays very important roles of improving the turbine performance.

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. [ABSTRACT FROM AUTHOR]

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.

Both scientific and industrial communities have a growing interest in marine renewable energies. There is a wide variety of technologies in this domain, with different degrees of maturity. This study focuses on two models of a mast-free vertical axis Darrieus tidal turbine with the objective of characterizing the effect of vertical confinement, rotor configuration, and fluid–structure interactions on their performances in free-surface flows. The first model comprised four straight rigid blades maintained by circular flanges on both ends of the rotor and the second model is equipped with free-ended interchangeable blades attached to a single upper flange. Two configurations of the second model mounted with either rigid or flexible blades were used, first for comparison with the dual-flange turbine, then in order to address the effect of fluid–structure interactions on the turbine performances. While the single-flange models exhibit a significantly lower efficiency at all operating points, it is observed that the use of flexible blades tends to enhance turbine performances at low Reynolds numbers. The flow topology obtained from PIV measurement at selected operating points is discussed with respect to the performance of each turbine model in order to highlight the role of the dynamic stall and blade–vortex interactions. [ABSTRACT FROM AUTHOR]

The energy potential of low-head water can be exploited by using the horizontal axial flow to produce rotation in the turbine, which is then converts it into electricity in the generator. The types of blades that are commonly used are propeller types, cross-flow types, and Kaplan types. In this research, a prototype of micro-hydro power plant with a capacity of 20 W will be developed, which utilizes the potential of water flow with a head < 0.5 m. This research begins with observing water flow, including flow characteristics and parameters such as speed, head, and available discharge. The next step is to design the power plant, which includes the design of a very low head horizontal axial turbine, turbine structure and accessories, turbine blade rotor, power transmission system, generator selection, and control system. The manufacture of the main components of the turbine, reservoir, diffuser, etc., is carried out before integrating the entire micro hydropower system. The result shows the physical model of the very low-head turbine prototype produces power at the highest Head (0.4 m) of 11.02 W, while at the same Head, the computational fluid dynamic (CFD) results produce the most significant power with 13.55 W. [ABSTRACT FROM AUTHOR]

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 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 computational fluid dynamics simulations, is then proposed for both the cases of negligible and not negligible energy losses along the pipe. [ABSTRACT FROM AUTHOR]

A better understanding of the flow field of the cross-flow turbine (CFT) will be useful in its design and operation. As far as is known, no comprehensive study carried out relating to the effect of Reynolds number to turbulent shear stress, shear wall, energy kinetic turbulent, dissipation rate and Reynolds stress, and the occurrence of vortices around the runners of the CFTs. This study was designed to investigate the flow field in the nozzle and runner of the CFT using computational fluid dynamics (CFD) method. CFD methods were chosen because they can visualize detailed flow patterns that other methods cannot. The setups used in the CFD method such as two-dimensional unsteady simulations, six degrees of freedom features, shear stress transport k-ω turbulent model, and pressure-based solver. Based on results, for the nozzle, the shape of the velocity profile shows that the highest momentum flux occurs at the end of the nozzle, near the runner. Distribution of shear wall was highest at the base and tip of the nozzle; it was lowest at the centre. The turbulent kinetic energy profile at the nozzle was proportional to the turbulent boundary layer profile, Reynolds stress and eddy viscosity. This indicated that nozzle shape affects the momentum flux; therefore, good nozzle geometry can transfer the maximum water energy into the blade. The nozzle's optimum geometry can be achieved by discharge and direction, optimizing velocity magnitude. This minimizes energy loss due to friction between the stream, vortex and mass of wasted fluid. For the runner, the highest turbulent kinetic energy, dissipations rate and Reynolds stress were located at the runner. Not all the water's energy converted into mechanic energy because the part of that energy was used in mixing between water and air. The establishment of lift force on the active blades was not caused by the flow field that crosses the upper part of the blade, but by the momentum of water that hit the lower part of the blade. A vortex formed due to separation of the flow from the blade significantly affected the runner's performance rather than rotational flow (air phase) in the CFT. [ABSTRACT FROM AUTHOR]

Abstract Cross-flow turbine blades operate in an unsteady environment over large ranges of angle of attack and Reynolds number, often enduring dynamic stall. The hydrodynamics are further complicated because the circular orbit of the blades changes their effective curvature. In order to address these technical challenges with modeling cross-flow turbines, this article presents a novel dynamic stall model with flow curvature correction. The dynamic stall model extends Beddoes-Leishman dynamic stall theory, including several effects such as proper asymptotic behavior at large (∼90°) angles of attack, influence of reduced-pitch rate on the stall angle, dynamics of the flow separation point, and changes in effective camber due to flow curvature. Further, the model enables rapid hydrodynamic analysis of cross-flow turbines using free vortex methods. Important design parameters such as blade thickness and camber are explicitly accounted for in the model, which enables parametric study of turbine configurations and therefore makes the model useful for system-level turbine optimization. Numerical predictions are validated by experimental data for several cases, including ranges of blade profile, toe angle, solidity, and tip speed ratio. Highlights • A dynamic stall model in discrete vortex method was implemented for cross flow turbines. • Experimental data was acquired for a two blade test cross flow turbine. • The analytical model results were compared with published and experimental data. [ABSTRACT FROM AUTHOR]

The presented article brings general overview of CFD analysis of two cross-flow turbine types (a classical impulse turbine and a reaction turbine). The author focuses his attention mainly on the discussion of differences in flow patterns in the outflow section of these turbines, because this element exerts significant impact on performance properties of the turbine. The article presents a comparison of computations and experimental results of the cross-flow turbine manufactured by IMP PAN. The analysis was performed by means of a computer program Fluent 5.0TM for a twodimensional example.