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One key factor in the exploitation of tidal energy is the study of interactions of turbines when working in tidal turbine farms. The Momentum Reversal and Lift (MRL) turbine is a novel cross flow turbine. The three blades rotate around a common central horizontal axis which is parallel to their own axis and perpendicular to the flow. The novelty of the MRL turbine is that it relies on the combination of both lift and momentum reversal (drag) for energy extraction. Scaled MRL turbine models of 0.164 m in diameter were used to characterise the flow in three different tidal array settings. Detailed maps of axial velocity profiles and velocity deficits downstream of the turbine are presented, enabling the visualisation of characteristic flow patterns. The results show that the MRL generates lower velocity deficits and turbulence intensities in the near wake than those associated with horizontal axis turbines. The downstream wake was not completely symmetrical which was related to the geometry of the device but also due to the flow developed in the flume. Amongst the three array configurations studied, a fence of turbines with the lowest separation provided the highest power output.

The experimental study was intended to investigate performance characteristics of three cross flow turbine model using nozzle roof curvature radius centered on shaft axis designed on the same flow rate, runner diameter and rotational speed which with each model having different runner width as well as its nozzle entry arc. The nozzle and runner width were designed as the fuction of the nozzle entry arc, the shorter pair of runner-nozzle the larger nozzle entry arc and vise versa. The nozzle entry arcs used in this experimental study were 75o, 90o and 120o. In addition, the three models having equal cross sectional area of nozzle entry. The three turbine nozzles were designed having roof curvature radius centered on shaft axis. The such nozzle roof curvature were expected to be able to deliver water in the better direction as well as its flow condition as the water entering the tubine runner. The experimental test rig consisted of the three turbine models, pump, piping systems, magnetic flow meter, and tachometer. The Flow rates, entered the turbine, supplied by the pump were measured by the magnetic flow meter. The power generated on the turbine shaft was determined by measuring the torsion forces detected by using a spring balance, and turbine speeds were detected by a hand held tachometer. The turbine performance characteristics are shown by the relation of efficiency versus flow rate, head, and specific speed; as well as the relation of efficiency versus velocity ratio and speed ratio. The velocity ratio was the ratio of runner pheripheral velocity to water jet velocity entering the runner; the speed ratio was the ratio of runner speed to water jet speed entering the runner. The results of the study indicate that best efficiency points increase as the nozzle entry arc decreases or on the other hand best effisiency points decrease as the nozzle entry arc increases. The results shows that the cross flow turbine using 75 and 90 degree entry arcs indicate efficiency and power higher than that of turbine with 120 degree nozzle entry arc.

A detailed wake analysis of two different turbine concepts is conducted to gain a fundamental understanding of the main energy recovery processes at play in each case. An axial-flow turbine and a cross-flow turbine are considered. Both operate near their respective optimal efficiency conditions in a uniform oncoming flow and at a Reynolds number of 10 7 . Three-dimensional Delayed Detached-Eddy Simulations (DDES) are carried out and the time-averaged Unsteady Reynolds-averaged Navier–Stokes (URANS) equations are used as a post-processing tool in order to assess the importance of the various contributions affecting the wake recovery quantitatively. It is found that the dominant mechanism is fundamentally different between the two turbine technologies. Indeed, while the axial-flow turbine's wake is strongly influenced by an instability phenomenon leading to a significant turbulent transport, the cross-flow turbine's wake recovery is found to be much more related to the mean spanwise velocity field. As a result, unlike the axial-flow turbine's wake dynamics which is highly dependent on the turbulent characteristics of the oncoming flow, the cross-flow turbine's wake is expected to be less sensitive to these turbulent characteristics but highly dependent on the geometric characteristics of the turbine such as the turbine's aspect ratio.

Corvis L Rantererung1, Titus Tandiseno2, Mika Mallisa3

In this paper, suitability analysis of cross-flow turbine and synchronous generator (SG) characteristics for very low head hydro power application is performed. The former is a commercial product from a selected turbine manufacturer while the SG is a new commercial product bought from the public market. Given the technical specifications of the turbine: minimum power is 10 kW, rotation is 300 rpm, outer diameter (Do) of runner is 0.3 m, the transmission ratio is 1: 5, its suitability when coupled with a generator was tested experimentally. The results show that the generator performance was not as expected. Voltage ripples and current waves were found to be quite high. Vibrations always occur on the V-belt when the load of generator is changed. The efficiency of the generator was found to be around 60.61%. The results are expected to become a technical procedure in testing the suitability between a turbine and a generator when they are coupled; regardless they are new products or the existing ones.

A considerable interest in exploiting tidal currents for power generation has led to extensive studies on this source of renewable energy. Turbines utilizing the marine streams consume the kinetic energy of the currents and convert it to mechanical energy. computational fluid dynamics (CFD) plays a major role in fluid flow–related studies. The present study deals with the key parameters which influence the turbine performance. The power, power coefficient (PC) and torque of the tidal cross-flow turbine (CFT) depends on several design parameters such as tip speed ratio (TSR), inlet and outlet blade angle, internal diameter, angle of attack, number of blades, and augmentation channel inlet area. The internal flow characteristic of the turbine has been studied for various cases. A standard CFT model with augmentation channel dimensions of 3.2 m×1.6 m is modeled with rotor having 30 blades, 464 mm length in radial direction and 3.2 m axial length, 300 inlet and radial outlet. The study reports the torque, power, and PC with channel under high as well as low tides. The boundary conditions taken are inlet velocity of 2.5 m/s, relative pressure of 0 Pa at outlet, and the reference pressure is atmospheric with walls modeled under free slip condition. Using pressure–velocity coupling scheme, SIMPLE and k-e turbulence model, the velocity vectors have been reported for both, high tide, and low tide. The model is validated with existing benchmarks and reasonable agreement is observed. A parametric study is reported by varying the internal diameter of the rotor and inlet blade angle. The plots of power, PC, and torque with TSR is presented and discussed.

ross flow turbines are widely used as turbines for driving micro-scale hydropower plants in rural areas, but their efficiency is still low because cross flow turbines only use one nozzle. The utilization of the potential energy of water is not optimal yet to be converted into pressure and kinetic energy of water in the nozzles with high water velocity hitting the turbine blades. The problem of cross flow turbines with one nozzle has an uneven flow of water to the turbine blades, and it is not effective in converting potential energy into power in the turbine. The purpose of this research is to develop a four-nozzle Cross Flow turbine and test its performance. The method used is to conduct experimental testing in a laboratory that tests the performance of a cross flow turbine using four nozzles. A cross flow turbine with four nozzles has better performance than a cross flow turbine using only one nozzle. The results obtained that the cross flow turbine with four nozzles where the water jets out of the nozzle is more evenly distributed and the flow of water enters the turbine blade runner, resulting in a good impulse reaction in the blades. The conclusion is that the performance of the four nozzle cross flow turbine is able to produce higher turbine rotation, power and efficiency.

This article presents a practical method for predicting the power output of cross-flow tidal/river turbines with wake interaction and channel blockage effects. In a turbine farm, the power generated by each rotor depends on the cube of the local velocity, which is influenced by the bottom topology, by other turbines’ wakes and also by finite channel cross sectional areas restricting wake expansion. Therefore, the accuracy of power predictions depends strongly on proper modelling of rotor wakes and the influence of the channel/river boundaries. This is a critical issue for the tidal and river kinetic turbine power industries because best practise for predicting energy yield has yet to be established, while project revenue streams are primarily a function of yield. This article introduces a simulation-based method to predict individual turbine and total farm power output with modest computational expense, named the tuned actuator cylinder approach (TACA). Rotors are represented in the simulations as momentum sink terms, using approximately 21 elements across their diameter, allowing for very fast simulations of multiple rotors. The model is tuned to match known (from experiments or high-fidelity blade-resolved simulation) thrust and power operational profiles for a particular turbine, with known inflow conditions. Once tuned, the TACA model can be applied to a wide range of turbine array configurations, and arbitrary flow environments. Thus, TACA is an appropriate tool for case-studies and/or optimization of turbine array layout at real-world tidal/river energy sites.

Cross-flow turbine is one of prime mover type that is simple, capable to extract water power and easy to be manufactured. The runner is working at 2 stages. The need of high momentum has lead researchers to design water nozzle, blades, as well as the set-up between nozzle and runner. High momentum water nozzle and cross-flow runner has been designed individually with the same design criteria. Unfortunately, experimental testing may not gain specific flow pattern inside the nozzle and the runner. The purpose of this study is to investigate the flow pattern inside the nozzle, runner using CFD method, Ansys 2019 R3 academic version. The CFD simulation done 3-dimensionally with 5 nozzle inlet velocity variations: 2 m/s, 3 m/s, 4 m/s, 5 m/s and 6,487 m/s. The fluid is assumed to be 1 phase, using mesh with 17.750 nodes, inlet fluid pressure 1,05 Pa, and temperature 24,85°C. The results showed that the lowest velocity and pressure for variation 1 at 1st stage (v1) = 6,65 m/s and (p1) = -11931,5 Pa, and the highest velocity and pressure at 1st stage (v5) = 21,72 m/s and (p5) = -127521 Pa. At 2nd stage, variation 1 and 5 resulting velocity (v1) = 1,78 m/s and (p1) 593,264 Pa, (v5) = 5,83 m/s and (p5) = 6360,32 Pa respectively. The main different of the flow pattern between 5 inlet velocity variations is the final flow thickness inside the runner get thicker at higher velocity, which is assumed to gain more rotational velocity.

Marine current energy is a clean energy source and is a solution to the problems faced by burning fossil fuels such as global warming and climate change. Once tapped, the useful shaft power can be converted into electrical energy. To make this practical, the designed energy converter should be capable of operating at low marine current velocities, it should be suitable for installation at locations that have low water depths and should have lower manufacturing, installation and maintenance costs. A ducted cross-flow turbine has all the above features and it will be suitable for Pacific Island countries (PICs) for extracting marine current energy. The ducted cross-flow turbine was designed, modelled and analyzed in commercial Computational Fluid dynamic (CFD) code ANSYS-CFX. The inlet and outlet duct sizes were optimized for maximum output. Before the analysis of full model, the CFD results were validated with experimental results. Simulations for the 1:10 ducted cross-flow turbine (having a diameter of 150 mm) were performed with 400,000 nodes, as increase in the grid size did not make much difference other than increasing the simulation time significantly. The maximum difference in the power coefficient between CFD and experimental results was 6%. Simulations were then performed for the full-scale prototype, which has a duct (nozzle) inlet of 3.5 m × 3.5 m and a turbine diameter of 1.5 m, at three freestream velocities of 0.65 m/s, 1.95 m/s and 3.25 m/s. Analysis of the prototype performance showed that the ducted cross-flow turbine can reach a maximum efficiency of 56% and can produce 21.5 kW of power at a current speed of 1.95 m/s and 103.6 kW at 3.25 m/s. The designed cut-off speed was 4 m/s.

In 2016, more than 1060 million people in the world lived in areas that are difficult to access, causing insufficient access to electricity. To overcome the problem, a pico hydro cross-flow turbine is considered to be a proper solution because it has a simple design, has few civil works, is easy to maintain, and can operate at a medium head with high variation of discharge. To increase the turbine's performance, this study aims to find the effect of blade depth on performance and to investigate the possibility of a cross-flow turbine being a reaction turbine. The CFD method was selected because it can represent the flow pattern in a turbine with more detail than other methods. The blade depth variation in this study consists of 0 mm, 3 mm, 6 mm and 9 mm, and the pressure inlet boundary conditions are varied with heads of 2.7 m and 5 m. The model turbulence RNG k-є standard has been used to predict turbulent flow. From the 2.7 m head, the average efficiency with the ratio U/V 0.42-0.5 produced by blade depth are: 0 mm is 41.9%, 3 mm is 45.8%, 6 mm is 34.4% and 9 mm is 36.7%. Meanwhile, the variations from the 5 m head are: 0 mm is 49.8%, 3 mm is 57.3%, 6 mm is 53.7% and 9 mm is 49.6%. A two-factor ANOVA without replication was performed to determine the relationship of blade depth to performance, and the results showed there is an effect because the F-critical was higher than F. In addition, the blade does not entirely convert the water's kinetic energy to power. Thus, the reaction turbine concept cannot be used in cross-flow turbines because there is no lift force produced by any blade in the two conditions.

The industrial sectors in Indonesia is currently growing very rapidly because it is supported by the development of technology in the field of manufacturing. One of the most frequently used machining operations in the manufacturing industry is welding operations. Welding operation is the most efficient and efficient method to combine two or more metal components. The product quality of welding can be obtained by using the production tool (fixture). The purpose of this research is to improve the quality of turbine runner product by using the welding fixture. The method was to design and make welding fixture of turbine runner welding, test the concentricity, straightness of the dish, the stability of the dish to the shaft, and the alignment of the blades to the shaft, and to analyze the deviation of measurement results. Based on the result of welding fixture design of cross-flow turbine runner component, a prototype welding fixture which can facilitate the assembling process of cross-flow turbine runner component was obtained. The conclusions of this research were: 1) The quality of the cross-flow turbine runner product can be increased along with the small geometrical deviation on cross-flow turbine runner using accelerator tool, 2). The maximum deviation of the runner disc placement to the axis of the axis on the 300mm diameter runner is 1.2mm and the runner of 200mm with diameter of 0.68mm, and 3). The assembling time of the turbine runner components is shorter using weld assembly tools with better accuracy.

The experimental study was intended to investigate characteristics of the cross flow turbine based to the three models designed on the same runner diameter with different runner length of each. The Flow rates were measured by magnetic flow meter, the forces were detected by using spring balance and turbine speeds were detected by tachometer. The performance characteristics are shown by the relation of Power and efficiency versus jet entry arc, as well as the relation of Power and efficiency versus ratio between diameter and width of runner. The study indicated that the efficiency of the models were slightly difference, the highest efficiency indicated by the turbine with the ratio between length of runner and the diameter of the runner was 2; It was corresponding to the 75 degree entry arc.

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.

To supply continuous and reliable power to the water monitoring systems and motorized control valves in urban water supply networks, the inline cross-flow turbine has been developed. This study aims to investigate the effects of different runner geometries on the performance of inline cross-flow turbines and to determine the optimal runner geometrical parameters. In this paper, a theoretical analysis of the working mechanism of a cross-flow runner is first performed to study the impacts of the runner geometry on turbine performance. Thereafter, several turbine models with different runner geometries are built and simulated to analyse the output power, water head reduction and torque generation at each runner stage. The results indicate that a good match between the flow inlet angle and blade outer angle notably enhances the turbine performance. Based on the results, the recommended optimal blade outer angle in this research is 30°. In addition, the results also show that the runner diameter ratio has a major impact on torque generation at the runner first stage. A lower runner diameter ratio leads to a higher output power, but the water head reduction is also higher. Based on the results, the suggested runner diameter ratio is 0.68. A numerical study on the number of blades indicates that when the number of blades increases from 20 to 24, the turbine output power considerably rises, and the maximum output power reaches 2285 W. However, if the blade number is further increased, the variation in output power is very slight. Thus, the proposed optimal blade number is 24. Based on the research results, the maximum turbine efficiency can reach 50.9% after runner optimization.

This study attempts to improve the efficiency of a given type of cross flow turbine by supplying air from air suction holes. A newly developed air supply method is adopted. CFD analysis of the cross flow turbine is carried out to investigate the performance and internal flow characteristics of the turbine in detail. The air layer prevents shock loss between water flow and axis and suppresses recirculation flow in the runner passage. Hence, it is necessary to measure the amount of air layer in the runner passage and examine its effect on the performance of the cross flow turbine. The result shows that the turbine efficiency has improved more as the newly developed air supply method is applied effectively.

Marine current energy is clean and reliable energy source. It can be alternative energy source to produce electricity if tapped with a suitable marine current energy converter. Pacific Island countries (PIC) like Fiji can reduce the amount of Fossil fuel used. However for most energy converters designed perform well at marine current velocities above 2m/s and it needs to be installed at depths of 20 – 40m also installation and the maintenance cost of such devise will be quite high if it needs to be installed in Fiji. Therefore a ducted cross flow turbine was designed, which can give desired output at minimum installation and maintenance cost. A dusted cross flow turbine has been design taking into account for its operating condition. The turbine was modelled and analyzed in commercial; Computational Fluid dynamic (CFD) code ANSYS-CFX. The code was first validated and with experiment results and finally performance analysis of full scale turbine was carried out. The designed turbine can have maximum efficiency of 56% producing rated power of 21kW; it produces 0.77kW at cut in speed of 0.65m/s.

Recently, the cross flow turbines attract more attention for their good performance over a large operating regime at off design point. This study employs a very low head cross flow turbine, which has open inlet duct and has barely been studied before, to investigate the performance of the cross flow turbine with air suction from the rear part of the runner. Unlike conventional cross flow turbines, a draft tube is attached to the outlet of runner to improve the turbine performance. Water level and pressure in the draft tube are monitored to investigate the influence of air suction. Torque at local blade passage of three parts of runner is examined in detail under the conditions of different air suction. Consequently, it is found that with proper air suction in the runner chamber, the water level in the draft tube gradually drops to Stage 2 of the runner and the efficiency of the turbine can be raised by 10%. Overall, the effect of air-layer on the performance of the turbine is considerable.

Obtaining electrical energy from water streams with velocities below one meter per second using hydrokinetic turbines presents an important challenge as it is significantly lower than the range of operations (higher than two meters per second) offered by units currently commercialized. This research goes one step further than the state-of-the-art studies regarding the degree to which energy extraction is influenced by the water flow blockage caused by turbines in water flows; presenting that blockage as a key factor in the procurement of electrical energy using hydrokinetic micro turbines from low-velocity flowing water. Primarily, it describes the design and characterization of a small vertical-axis cross-flow hydrokinetic turbine whose dimensions maximize the blockage of the water circulating in a channel at very low velocity. For the turbine characterization, a model has been tested experimentally in a water tunnel with different flow rates and complemented by simulations under the same conditions using an adjusted computational fluid dynamics model. The experimental tests contemplate the measuring of the turbine’s electrical power, hydraulic coefficient and rotational speeds. The simulations of the numerical model facilitate the procurement of the corresponding water pressure and velocity fields. Further analysis has allowed for a closer examination of the different type of forces exerted on the faces of the blades as well as their position. Upon even closer inspection there appear to be a variety of possible scenarios contingent on the turbine load.

Tidal current and wind energies have become dominant sources of renewable energies in the modern culture. In this work, the aerodynamic characteristics of a novel hybrid vertical axis turbine (VAT) have been studied in flow fields of water and air using CFD analyses. A parametric study was conducted on the hybrid rotor design with the goal of optimizing the solidity ratio to cover a wide operation range, increase initial torque and maintain high coefficient of power values. The hybrid turbine design with a solidity ratio of 0.5 demonstrated improvements to the self-startup feature and achieved the highest coefficient of power (Cp) values of 44.5% and 50% in air and water flows, respectively. The results were in favor of utilizing this design in flow fields of water and air as an enhancement to previous literature. Further studies are required to assess the aerodynamic properties of the model in 3D CFD analyses.

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

The performance and detailed near-wake characteristics of a vertical axis, cross-flow turbine (CFT) of aspect ratio 1 were measured in a large cross-section towing tank. The near-wake at one turbine diameter downstream was examined using acoustic Doppler velocimetry, where essential features regarding momentum, energy, and vorticity are highlighted. Dominant scales and their relative importance were investigated and compared at various locations in the measurement plane. Estimates for the terms in the mean streamwise momentum and mean kinetic energy equation were computed, showing that the unique mean vertical velocity field of this wake, characterised by counter-rotating swirling motion, contributes significantly more to recovery than the turbulent transport. This result sheds light on previous CFT studies showing relatively fast downstream wake recovery compared to axial-flow turbines. Finally, predictions from a Reynolds-averaged Navier–Stokes simulation with the commonly used actuator disk model were ...