scholarly journals Computational Fluid Dynamics Modelling and Simulation of an Inclined Horizontal Axis Hydrokinetic Turbine

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3151 ◽  
Author(s):  
Leidy Contreras ◽  
Omar Lopez ◽  
Santiago Lain
Keyword(s):  
Three Dimensional ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Navier Stokes ◽  
Main Stream ◽  
Transient Model ◽  
Drag Forces ◽  
Operation Conditions ◽  
Hydrokinetic Turbine ◽  
Inclination Angles

In this contribution, unsteady three-dimensional numerical simulations of the water flow through a horizontal axis hydrokinetic turbine (HAHT) of the Garman type are performed. This study was conducted in order to estimate the influence of turbine inclination with respect to the incoming flow on turbine performance and forces acting on the rotor, which is studied using a time-accurate Reynolds-averaged Navier-Stokes (RANS) commercial solver. Changes of the flow in time are described by a physical transient model based on two domains, one rotating and the other stationary, combined with a sliding mesh technique. Flow turbulence is described by the well-established Shear Stress Transport (SST) model using its standard and transitional versions. Three inclined operation conditions have been analyzed for the turbine regarding the main stream: 0° (SP configuration, shaft parallel to incoming velocity), 15° (SI15 configuration), and 30° (SI30 configuration). It was found that the hydrodynamic efficiency of the turbine decreases with increasing inclination angles. Besides, it was obtained that in the inclined configurations, the thrust and drag forces acting on rotor were lower than in the SP configuration, although in the former cases, blades experience alternating loads that may induce failure due to fatigue in the long term. Moreover, if the boundary layer transitional effects are included in the computations, a slight increase in the power coefficient is computed for all inclination configurations.

Performance study of twisted Darrieus hydrokinetic turbine with novel blade design

2021 ◽  
pp. 1-37
Author(s):  
Mabrouk Mosbahi ◽  
Mouna Derbel ◽  
Mariem Lajnef ◽  
Bouzid Mosbahi ◽  
Zied Driss ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Maximum Power ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Small Scale ◽  
Performance Study ◽  
Hydrokinetic Turbine ◽  
Blade Shape ◽  
Water Turbine ◽  
Water Canals

Abstract Twisted Darrieus water turbine is receiving growing attentiveness for small-scale hydropower generation. Accordingly, the need for raised water energy conversion incentivizes researchers to focalise on the blade shape optimization of twisted Darrieus turbine. In view of this, an experimental analysis has been performed to appraise the efficiency of a spiral Darrieus water rotor in the present work. To better the performance parameters of the studied water rotor with twisted blades, three novel blade shapes, namely U-shaped blade, V-shaped blade and W-shaped blade, have been numerically tested using a computational fluid dynamics three-dimensional numerical model. Maximum power coefficient of Darrieus rotor reaches 0.17 at 0.63 tip-speed ratio using twisted blades. Using V-shaped blades, maximum power coefficient has been risen up to 0.185. The current study could be practically applied to provide more effective employment of twisted Darrieus turbines and to improve the generated power from flowing water such as river streams, tidal currents, or other man made water canals.

scholarly journals Computation of Flow Past a Turbine Blade With and Without Tip Clearance

1991 ◽  
Author(s):  
W. R. Briley ◽  
D. V. Roscoe ◽  
H. J. Gibeling ◽  
R. C. Buggeln ◽  
J. S. Sabnis ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Main Stream ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Gas Generator

Three-dimensional solutions of the ensemble-averaged Navier-Stokes equations have been computed for a high-turning turbine rotor passage, both with and without tip clearance effects. The geometry is Pratt & Whitney’s preliminary design for the Generic Gas Generator Turbine (GGGT), having an axial chord of 0.5 inch and turning angle of about 160 degrees. The solutions match the design Reynolds number of 3x 106/inch and design inflow/outflow distributions of flow quantities. The grid contains 627,000 points, including 20 radial points in the clearance gap of 0.015 inch, and has a minimum spacing of 10−4 inch adjacent to all surfaces. The solutions account for relative motion of the blade and shroud surfaces and include a backstep on the shroud. Computed results are presented which show the general flow behavior, especially near the tip clearance and backstep regions. The results are generally consistent with experimental observations for other geometries having thinner blades and smaller turning angles. The leakage flow includes some fluid originally in the freestream at 91 percent span. Downstream, the leakage flow behaves as a wall jet directed at 100 degrees to the main stream, with total pressure and temperature higher than the freestream. Radial distributions of circumferentially-averaged flow quantities are compared for solutions with and without tip leakage flow. Two-dimensional solutions are also presented for the mid-span blade geometry for design and off-design inflow angles.

scholarly journals A Comparative Study on the Performance of a Horizontal Axis Ocean Current Turbine Considering Deflector and Operating Depths

2020 ◽  
Vol 12 (8) ◽  
pp. 3333
Author(s):  
Nauman Riyaz Maldar ◽  
Cheng Yee Ng ◽  
Lee Woen Ean ◽  
Elif Oguz ◽  
Ahmad Fitriadhy ◽  
...  
Keyword(s):  
Fluid Pressure ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Ocean Current ◽  
Power Coefficient ◽  
Cfd Simulations ◽  
Torque Coefficient ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Design ◽  
Current Turbine

Several different designs and prototypes of ocean current turbines have been tested over recent years. For every design test, emphasis is given to achieving an optimum power output from the flow. In this study, the performance of a Horizontal Axis Ocean Current Turbine (HAOCT) has been investigated using three-dimensional Computational Fluid Dynamics (CFD) simulations for three cases, namely, (1) a turbine without a deflector, (2) a turbine with a deflector, and (3) a turbine with a deflector operating at a higher fluid depth. The turbine design was modeled in DesignModeler software and simulations were carried out in commercial CFD software Flow-3D. The Torque Coefficient (Cm) and Power Coefficient (Cp) for the turbine have been investigated for a certain range of Tip-Speed Ratios (TSRs) in a flow velocity of 0.7 m/s. Furthermore, comparisons have been made to demonstrate the effect of the deflector on the performance of the turbine and the influence of a higher fluid pressure on the same. The results from the simulations indicate that the higher value of Cp was achieved for Case 2 as compared to the other two cases. The findings from the study indicate that the use of the deflector enhances the performance of the turbine. Furthermore, a higher fluid pressure acting on the turbine has a significant effect on its performance.

scholarly journals Investigation of an Innovative Rotor Modification for a Small-Scale Horizontal Axis Wind Turbine

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2649 ◽  
Author(s):  
Artur Bugała ◽  
Olga Roszyk
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Cfd Simulation ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Small Scale ◽  
Horizontal Axis Wind Turbine ◽  
Airflow Distribution

This paper presents the results of the computational fluid dynamics (CFD) simulation of the airflow for a 300 W horizontal axis wind turbine, using additional structural elements which modify the original shape of the rotor in the form of multi-shaped bowls which change the airflow distribution. A three-dimensional CAD model of the tested wind turbine was presented, with three variants subjected to simulation: a basic wind turbine without the element that modifies the airflow distribution, a turbine with a plano-convex bowl, and a turbine with a centrally convex bowl, with the hyperbolic disappearance of convexity as the radius of the rotor increases. The momentary value of wind speed, recorded at measuring points located in the plane of wind turbine blades, demonstrated an increase when compared to the base model by 35% for the wind turbine with the plano-convex bowl, for the wind speed of 5 m/s, and 31.3% and 49% for the higher approaching wind speed, for the plano-convex bowl and centrally convex bowl, respectively. The centrally convex bowl seems to be more appropriate for higher approaching wind speeds. An increase in wind turbine efficiency, described by the power coefficient, for solutions with aerodynamic bowls was observed.

Numerical Study on Impeller Performance of Mini Hydro Turbine

2015 ◽  
Vol 772 ◽  
pp. 552-555 ◽  
Author(s):  
Kyu Han Kim ◽  
Joni Cahyono
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Hydro Turbine ◽  
Pressure Distributions ◽  
Power Outputs

The aim of this paper is to numerically explore the feasibility of designing a Mini-Hydro turbine. The interest for this kind of horizontal axis turbine relies on its versatility. In the present study, the numerical solution of the discredited three-dimensional, incompressible Navier-Stokes equations over an unstructured grid is accomplished with an ANSYS program. In this study, a mini hydro turbine (3kW) has been considered for utilization of horizontal axis impeller. The turbine performance and flow behavior have been evaluated by means of numerical simulations. Moreover, the performance of the impeller varied in the pressure distribution, torque, rotational speed and power generated by the different number of blades and angles. The results trends are similar between the highest pressure distributions at the impeller also produced highest power outputs on 6 numbers of blades at impeller. The model has been validated, comparing numerical results with available experimental data.

Direct Numerical Simulation of Effects of Small Angle of Incidence on Honji Instability

2011 ◽  
Author(s):  
Kun Yang ◽  
Liang Cheng ◽  
Hongwei An ◽  
Ming Zhao
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Oscillatory Flow ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Angle Of Incidence ◽  
Navier Stokes Equations ◽  
Small Incidence ◽  
Inclination Angles

This paper concerns Honji instability generated around a circular cylinder in an oscillatory flow with a small oblique angle. In this study, direct numerical simulation has been conducted for an oscillatory flow past a stationary cylinder with small incidence angles (α) of 5° and 10° at KC number of 2 and β number of 200. The three-dimensional Navier-Stokes equations are solved using the Petrov-Galerkin finite element method. Flow structures around the cylinder are visualized through using streamlines, velocity vectors and vorticity contours. Honji instability has been captured at both chosen inclination angles. However Honji vortex pairs are asymmetric at α = 5° and 10° due to the inclination of the oscillation direction and can only be observed during the flow reversal. It is also found that the flow inclination appears to suppress the three-dimensional instability.

Numerical Analysis of Blockage Ratio Effect on a Portable Hydrokinetic Turbine

2016 ◽  
Author(s):  
Cosan Daskiran ◽  
Jacob Riglin ◽  
Alparslan Oztekin
Keyword(s):  
Free Stream ◽  
Numerical Study ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Power Coefficient ◽  
Stream Velocity ◽  
Blockage Ratio ◽  
Ratio Effect ◽  
Turbine Performance ◽  
Hydrokinetic Turbine

Three-dimensional steady state Computational Fluid Dynamics (CFD) analyses were performed for a pre-designed micro-hydrokinetic turbine to investigate the blockage ratio effect on turbine performance. Simulations were conducted using a physical turbine rotor geometry rather than low fidelity, simplified actuator disk or actuator lines. The two-equation k-ω Shear Stress Transport (SST) turbulence model was employed to predict turbulence in the flow field. The turbine performance at the best efficiency point was studied for blockage ratios of 0.49, 0.70 and 0.98 for three different free stream velocities of 2.0 m/s, 2.25 m/s and 2.5 m/s. Distinct blockage ratio results at a free stream velocity of 2.25 were compared to a previous numerical study incorporating the same rotor geometry within an infinite flowing medium. The pressure gradient between turbine upstream and turbine downstream for blocked channel flows elevated the turbine performance. The increment in blockage ratio from 0.03 to 0.98 enhanced power coefficient from 0.437 to 2.254 and increased power generation from 0.56 kW to 2.86 kW for the present study.

Analysis of the Effect of a Slotted Flap Mechanism on the Performance of an H-Darrieus Turbine Using CFD

2014 ◽  
Author(s):  
László Daróczy ◽  
Mohamed H. Mohamed ◽  
Gábor Janiga ◽  
Dominique Thévenin
Keyword(s):  
Three Dimensional ◽  
Vertical Axis ◽  
Operating Conditions ◽  
Horizontal Axis ◽  
Pollutant Emissions ◽  
Power Coefficient ◽  
Major Drawback ◽  
Systematic Analysis ◽  
Low Wind Speed ◽  
Low Efficiency

Wind energy represents nowadays a very important source of energy for many countries. It provides an efficient and effective solution to reduce fuel consumption as well as pollutant emissions. VAWTs (vertical axis wind turbines) were originally considered as very promising, before being superseded by the present, horizontal axis turbines. There is now a resurgence of interests for VAWTs, in particular Darrieus turbines. VAWTs like the H-rotor Darrieus turbine appear to be particularly promising for low wind speed conditions, but suffer from a low efficiency compared to horizontal axis turbines. Additionally, Darrieus turbines are not self-starting, which is a major drawback. The present paper introduces a new idea to improve the global performance of Darrieus rotors, relying on a slotted flap. Due to its low manufacturing costs and size, a two-bladed H-rotor with a radius of 2 meters was retained as a first application example. The blade airfoil relies on the S1046 profile, which was shown in previous studies to be superior under relevant operating conditions [1]. The solidity (Nc/R) of the rotor is kept at 0.25 for all the computations. In the first step a parametric geometry is created, where the end of the blade is converted into a slotted flap (with appropriate rounding). The main parameters are the distance between the main part of the blade and the flap (width of gap), the angle of the slot and the angle of the flap. In the second step a systematic analysis of the effect of those variables on the force and power coefficient is carried out using three-dimensional full factorial Design-of-Experiment with an in-house parameterization and optimization software. For each configuration, force and power coefficients are calculated for four different tip-speed ratios (including the value, where the S1046 profile without flap shows its maximal power coefficient). The evaluation of each configuration is performed using a commercial CFD software. The flow is assumed in this first study to be two-dimensional and unsteady. Turbulence intensities follow the relevant norms (DIN EN 61400). Finally the results are compared to each other and to the reference design (S1046 without flap) and conclusions are given regarding power coefficient and flap load.

scholarly journals Design and numerical analysis of an efficient H-Darrieus vertical-axis hydrokinetic turbine

2019 ◽  
Vol 13 (4) ◽  
pp. 6036-6058
Author(s):  
Ramirez D. ◽  
Rubio-Clemente A. ◽  
E. Chica
Keyword(s):  
Rural Communities ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Turbine Rotor ◽  
Power Coefficient ◽  
Stream Velocity ◽  
Ansys Fluent ◽  
Electrical Grid ◽  
2D Simulation ◽  
Hydrokinetic Turbine

Hydrokinetic turbines are one of the technological alternatives to generate and supply electricity for rural communities isolated from the national electrical grid with almost zero emission. The Darrieus turbine is one of the options that can be used as a hydrokinetic turbine due to its high power coefficient (Cp) and easy manufacture. In the present work, the design and hydrodynamic analysis of a Darrieus vertical-axis hydrokinetic turbine of 500 W was carried out. A free stream velocity of 1.5 m/s was used for the design of the blades. The diameter (D) and blade length (H) of the turbine were 1.5 m and 1.13 m, respectively. The blade profile used was NACA0025 with a chord length of 0.33 m and solidity () of 0.66. Two (2D) and three dimensional (3D) numerical analyses of the unsteady flow through the blades of the turbine were performed using ANSYS Fluent version 18.0, which is based on a Reynolds-Averaged Navier-Stokes (RANS) model. A transient 2D simulation was conducted for several tip speed ratios (TSR) using a k-ω Shear Stress Transport turbulence (SST) scheme. The optimal TSR was found to be around 1.75. Main hydrodynamic parameters, such as torque (T) and CP, were investigated. Additionally, 3 geometrical configurations of the turbine rotor were studied using a 3D numerical model in order to identify the best configuration with less Cp and T fluctuation. The maximum Cp average was 0.24 and the amplitude of Cp variation, near 0.24 for the turbine model with 3 blades of H equal to 1.13 m. On the other hand, for the turbine models with 6 and 9 blades of H equal to 0.565 m and 0.377 m, respectively, the maximum Cp averages were 0.51 and 0.55, respectively, and the amplitude of Cp variation, near 0.07 for the model with 6 blades and 0.17 for the model with 9 blades. This revealed that the hydrokinetic turbine with a geometrical configuration of 6 blades greatly improves the performance of the turbine due to this model has advantages compared to models with 3 and 9 blades, in terms of the reduction of their T curve fluctuation.

Experimental and Theoretical Studies for Improving the Performance of a Modified Shape Savonius Wind Turbine

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
W. A. El-Askary ◽  
Ahmed S. Saad ◽  
Ali M. AbdelSalam ◽  
I. M. Sakr
Keyword(s):  
Wind Velocity ◽  
Turbulence Model ◽  
Three Dimensional ◽  
Power Coefficient ◽  
Navier Stokes ◽  
Optimized Design ◽  
Percentage Increase ◽  
Aspect Ratios ◽  
Air Jet ◽  
Significant Performance

Abstract In this paper, measurements and computations are performed to study the performance of a 45-deg twisted Savonius rotor with a modified profile, at various overlap ratios (δ), aspect ratios (AR), and wind velocity (V). A free air jet test rig is used to carry out the experiments, while three-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) equations are used, in conjunction with the renormalization group (RNG) k–ɛ turbulence model, to perform the computations. The present experimental results successfully verify the simulation predictions obtained by the selected turbulence model. The RNG k–ɛ turbulence model has been chosen based on previous tests performed and published by the authors. Furthermore, both torque coefficient (CT) and power coefficient (CP) are numerically predicted at various tip speed ratios (λ) for overlap ratios (δ) ranging from 0.0 to 0.5, aspect ratios (AR) ranging from 0.75 to 3, and wind velocity values ranging from 4 to 18 m/s. Unlike the conventional rotor, the present twisted rotor with a modified profile produces significant performance improvement in the case of modified rotor without overlapping (δ = 0.0). Moreover, the peaks of CT and CP of the twisted rotor with the modified profile are enhanced with the increase in the aspect ratio. However, the percentage increase is noticed to be insignificant for AR greater than two. The maximum power coefficient (CPmax) for the twisted rotor with the modified profile and optimized design is 0.305 at a wind velocity of 6 m/s, with a performance gain of 75.3% compared to the conventional Savonius wind rotor which has CPmax=0.174.

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