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Low/zero-head cross-flow turbines (LZH-CFT) possess vast potential in the field of renewable energy technology. This research presents a modified design of a cross-flow turbine specifically engineered to harness the untapped hydro-kinetic energy from low/zero-head water resources. Unlike traditional hydro turbines, the LZH-CFT leverages a cross-flow configuration to utilize the water flows of natural streams, making it an ideal solution for flow channels with low/zero head. The design is modified through ANSYS simulations by varying the rotor’s blade angles (from 0 to 90°) and 60° angle is found optimum. The prototype model of modified design is prepared and tested, which represents 62.5% RPM efficiency and provides double power as compared to the typical cross-flow turbine.

Crisis electricity was a crucial issue in the rural area. Crossflow turbine (CFT) in pico in pico scale is the best option for electricity provider for rural areas. Due to its usefulness and development of computer technology, computational fluid dynamics method application for CFT study becomes increasingly frequent. This paper compiles the implementation of the computational fluid dynamic (CFD) approach for CFT on a pico scale. Based on the literature, the Renormalization Group (RNG) turbulence model is recommended to predict the flow field that occurs in CFT because its error is lower than others turbulence models, the RNG error of 3.08%, standard of 3.19%, and transitional SST of 3.10%. Furthermore, six-degrees of freedom (6-DoF) is recommended because it has an error of 3.1% than a moving mesh of 9.5% for the unsteady approach. Thus, based on the review, the RNG turbulence model and 6-DoF are recommended for the CFT on the pico scale.

Indonesia is an agrarian country that continuously produces water, so it has the potential to develop a hydroelectric power plant. Computational Fluid Dynamic (CFD) application could be used to be an economical, quick, and efficient approach to improve the engineering design and turbine performance. This research aimed to find the effect of guide vane opening variations and total blades on cross-flow turbine performance using CFD simulation. This research used experimental modelling method with ANSYS program for turbine design with 22, 24, and 26 turbine blades and guide vane opening variations of 12°, 16°, 20°, 24°, and 36°. The data were collected by reviewing the simulation results after the numerical calculation process. The results showed that the cross-flow turbine performance was improving along with the increasing guide vane opening. The optimum turbine performance (power and efficiency) was obtained at 24° opening of guide vane and 26 total blades, producing 868.53 W power with 75.16% efficiency.

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

This study examines a cross-flow turbomachine designed for power generation in areas with limited discharge and head availability, focusing on sustainability, affordability, and ease of operation. It investigates how varying the number of blades in the runner affects turbine performance while keeping other design factors constant. Testing runners with 8, 12, 16, 20, and 24 blades under identical conditions reveal consistent RPM variations across different blade numbers for various parameter combinations. The study identifies a 12-blade configuration as optimal for electrification projects at selected sites. Experimental validation using the Taguchi technique confirms the reliability of the findings. Additionally, the research explores the turbine's performance under different nozzle tip elevations (18 cm, 16 cm, and 14 cm). The highest observed runner speed is 345 RPM for the 12-blade runner at an 8° angle of attack, with similar speeds recorded for the 24-blade runner under similar conditions. [ABSTRACT FROM AUTHOR]

Turbines are critical parts in hydropower facilities, and the cross-flow turbine is one of the widely applied turbine designs in small- and micro-hydro facilities. Cross-flow turbines are relatively simple, flexible and less expensive, compared to other conventional hydro-turbines. However, the power generation efficiency of cross-flow turbines is not yet well optimized compared to conventional hydro-turbines. In this article, a Computational Fluid Dynamics (CFD)-driven design optimization approach is applied to one of the critical parts of the turbine, the valve. The valve controls the fluid flow, as well as determines the velocity and pressure magnitudes of the fluid jet leaving the nozzle region in the turbine. The Non-Uniform Rational B-Spline (NURBS) function is employed to generate construction points for the valve profile curve. Control points from the function that are highly sensitive to the output power are selected as optimization parameters, leading to the generation of construction points. Metamodel-assisted and metaheuristic optimization tools are used in the optimization. Optimized turbine designs from both optimization methods outperformed the original design with regard to performance of the turbine. Moreover, the metamodel-assisted optimization approach reduced the computational cost, compared to its counterpart.

Low/zero-head cross-flow turbines (LZH-CFT) possess vast potential in the field of renewable energy technology. This research presents a modified design of a cross-flow turbine specifically engineered to harness the untapped hydro-kinetic energy from low/zero-head water resources. Unlike traditional hydro turbines, the LZH-CFT leverages a cross-flow configuration to utilize the water flows of natural streams, making it an ideal solution for flow channels with low/zero head. The design is modified through ANSYS simulations by varying the rotor's blade angles (from 0 to 90°) and 60° angle is found optimum. The prototype model of modified design is prepared and tested, which represents 62.5% RPM efficiency and provides double power as compared to the typical cross-flow turbine. [ABSTRACT FROM AUTHOR]

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 work examines the dynamic stall process and resulting wake features of cross-flow turbines under confined configurations using two computational modeling approaches, Reynolds-averaged Navier-Stokes (RANS) and large-eddy simulation (LES). Cross-flow turbines harvest energy from wind or water currents via rotation about an axis perpendicular to the flow and are a complementary technology to the more common axial-flow turbine. During their 360° rotation cross-flow turbine blades experience a cyclical variation in the angle of attack and velocity relative to the oncoming flow, leading to flow separation and reattachment, otherwise known as dynamic stall. The dynamic stall process causes an instantaneous loss in torque generation and unsteady force fluctuations which pose a challenge to accurate predictions of both the performance and the resulting unsteady flow field. This research compares RANS simulations to higher fidelity LES of a straight-bladed two-blade cross-flow turbine at a moderate Reynolds number (Rec = 45,000) in a confined configuration. The RANS model is shown to be very sensitive to confinement at the simulated tip speed ratio as it over-predicts power generation due to suppression of flow separation, while the flow field from LES matches well with the experimental validation. Results are compared with an unconfined configuration for which the RANS model successfully predicts a power curve; however, it displays significant differences in the evolution of flow structures such as premature shedding of the dynamic stall vortex and a lack of vortex diffusion during convection in the wake. [ABSTRACT FROM AUTHOR]

The mechanical power, total rotor drag, and near-wake velocity of a 1:6 scale model (1.075 m diameter) of the US Department of Energy's Reference Model vertical-axis cross-flow turbine were measured experimentally in a towing tank, to provide a comprehensive open dataset for validating numerical models. Performance was measured for a range of tip speed ratios and at multiple Reynolds numbers by varying the rotor's angular velocity and tow carriage speed, respectively. A peak power coefficient CP = 0.37 and rotor drag coefficient CD = 0.84 were observed at a tip speed ratio λ0 = 3.1. A regime of weak linear Re-dependence of the power coefficient was observed above a turbine diameter Reynolds number ReD ≈ 106. The effects of support strut drag on turbine performance were investigated by covering the rotor's NACA 0021 struts with cylinders. As expected, this modification drastically reduced the rotor power coefficient. Strut drag losses were also measured for the NACA 0021 and cylindrical configurations with the rotor blades removed. For λ = λ0, wake velocity was measured at 1 m (x/D = 0.93) downstream. Mean velocity, turbulence kinetic energy, and mean kinetic energy transport were compared with results from a high solidity turbine acquired with the same test apparatus. Like the high solidity case, mean vertical advection was calculated to be the largest contributor to near-wake recovery. However, overall, lower levels of streamwise wake recovery were calculated for the RM2 case-a consequence of both the relatively low solidity and tapered blades reducing blade tip vortex shedding-responsible for mean vertical advection-and lower levels of turbulence caused by higher operating tip speed ratio and therefore reduced dynamic stall. Datasets, code for processing and visualization, and a CAD model of the turbine have been made publicly available.

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 the Froude number variation that could mistakenly be ascribed to aspect ratio. This highlights the importance of a rigorous experimental design when exploring the effect of geometric parameters on cross-flow turbine performance. [ABSTRACT FROM AUTHOR]

In the electrical energy generation context in Colombia, the water resources represent the 64% of the potential generated according to UPME in the 2015 year; becoming into a solution to the growing energy demand and to the supply of energy in non-interconnected zones. The cross-flow turbines as Michell-Banki type, become an efficient and economically attractive choice. This paper shows the fluiddynamic performance of a laboratory’s model turbine under several operating conditions. The development of this analysis is supported by the results of experimental tests, uses the computational fluid dynamics as a tool for modelling, estimate, and analyse the turbine behaviour under different operating conditions, with ANSYS-Fluent software; the computational model considers the most important geometric aspects of the turbine and the opening percentage effect of the guide blade. The water flow through the rotor is approach through a turbulence model as κ – ε type. The numerical study results agree satisfactorily with the turbine performance observed in the laboratory.

Cross-flow turbines, also known as vertical-axis turbines, convert the kinetic energy in moving fluid to mechanical energy using blades that rotate about an axis perpendicular to the incoming flow. In this work, the performance of a two-turbine array in a recirculating water channel was experimentally optimized across 64 unique array configurations. For each configuration, turbine performance was optimized using tip-speed ratio control, where the rotation rate for each turbine is optimized individually, and using coordinated control, where the turbines are optimized to operate at synchronous rotation rates but with a phase difference. For each configuration and control strategy, the consequences of co- and counter-rotations were also evaluated. This is the first experimental cross-flow turbine array study to simultaneously address array geometry, control, and turbine rotation direction. Based on these results, we hypothesize how array configurations and control cases influence interactions between turbines and affect the performance of the array. [ABSTRACT FROM AUTHOR]

Recent experimental studies suggest that the usual way of measuring and predicting the efficiency of the cross-flow turbine do not describe the flow physics adequately. This verification led to the present investigation of some of the more relevant aspects related to the efficiency of this type of turbine. After presenting a detailed description of the rig used in the tests, the most adequate way of measuring the efficiency is discussed, including the specification of the proper datum used for the measurement of the head. Typical curves for the measured efficiency are shown, demonstrating that a peak efficiency of 84.8% is attainable with the cross-flow turbine, using new geometric relations, markedly different from those proposed by the present know-how in this field. Analysis of the experimental data seems to suggest that one of the reasons for the detected discrepancies is the assumption for the direction of the flow leaving the rotor. The consequences of the new physical insight are explored in this paper, leading to new theoretical relations for the efficiency evolution. It is demonstrated that the new theory describes reality better than previous analysis by comparing some of its predictions with experimental data. [ABSTRACT FROM AUTHOR]