Counter-rotating Wind Turbine Research Articles

Parametric Study on a Performance of a Small Counter-Rotating Wind Turbine

A small Counter-Rotating Wind Turbine (CRWT) has been proposed and its performance has been investigated numerically. Results of a parametric study have been presented in this paper. As parameters, the axial distance between rotors and a tip speed ratio of each rotor have been selected. Performance parameters have been compared with reference to a Single Rotor Wind Turbine (SRWT). Simulations were carried out with Computational Fluids Dynamics (CFD) solver and a Large Eddy Scale approach to model turbulences. An Actuator Line Model has been chosen to represent rotors in the computational domain. Summing up the results of simulation tests, it can be stated that when constructing a CRWT turbine, rotors should be placed at a distance of at least 0.5 D (where D is rotor outer diameter) or more. One can then expect a noticeable power increase compared to a single rotor turbine. Placing the second rotor closer than 0.5 D guarantees a significant increase in power, but in such configurations, dynamic interactions between the rotors are visible, resulting in fluctuations in torque and power. Dynamic interactions between rotor blades above 0.5 D are invisible.

Multiobjective Design Optimization of a Double-Sided Flux Switching Permanent Magnet Generator for Counter-Rotating Wind Turbine Applications

A counter-rotating wind turbine in which two sets of rotors rotating in opposite directions leads to the twice power density of the conventional turbines. Moreover, employing a high-power modern electric generator is another contributing factor in improving the performance of wind power generation systems. In this regard, double-sided flux switching permanent magnet generators, with ferrite magnet, are getting firm attention. In this regard, the concept and multiobjective design optimization procedure of this generator, connected with counter-rotating wind turbines, is proposed in this article. In order to achieve the optimum performance of the proposed generator, the design of experiments with Taguchi optimization is employed. In this method, although the effect of each design variable on the objective functions can be considered, selecting the best combination of control factors is not easy in the multiobjective optimization. Thus, a decision-making algorithm with the technique for order of preference by similarity to ideal solution is employed in order to select the best combination. Finally, the performance of the optimized counter-rotating double-sided flux switching permanent magnet generator will be evaluated by finite element modeling and experimental tests.

Experimental Study the Effect of Turbine Distance on Cross Flow Wind Turbine Performance in In-Line Configuration with Counter-Rotating Wind Turbine

Indonesia potentially has a wind energy sources that is 950 Megawatt. However, development of wind energy that has been implemented only reached 1.3 Megawatt or 0.13%. One of the studies that is being developed is using cross flow runner since it suitable with the condition in Indonesia, which has low wind speed and can catch wind from all direction. This study focuses on experiment using in-line configuration and expected to minimize reduce of torsion and to know the effect of power characteristic. Considered changes are made on distance between two turbines that is 1.5D; 2D; 2.5D in varied 5 m/s; 6 m/s; 7 m/s of wind speed. The research was carried out by using cross flow wind turbine with 200 mm in diameter and 200 mm in height in the wind tunnel. Based on this study, it can be concluded that the distance of turbine in in-line configuration with counter-rotating cross flow wind turbine affects the torsion and power coefficient.

A particle image velocimetry study of dual-rotor counter-rotating wind turbine near wake

This experimental work studied the flow characteristics in the near wake region behind dual-rotor wind turbines using two-dimensional particle image velocimetry. Two auxiliary rotors of 50% and 80% scale of the main rotor were installed upwind and operated in counter-rotating condition, which are compared to the conventional single-rotor turbine. In all the three configurations, a constant Reynolds number 9.5times 10^4 was applied, and all the rotors operated at a fixed tip speed ratio of 3.46. The mean and phase-averaged velocity fields were investigated together with the turbulence kinetic energy. It was found that the two auxiliary rotors do not result in a significantly different wake flow property. The configuration implementing the 50% auxiliary rotor sees a slightly better wake characteristics, in terms of weaker main rotor tip vortices and a counter-rotating swirling shear region at the mid-span behind the main rotor. The decay rates of the peak vorticity of the main rotor tip vortices and their circulation are found to follow an exponential manner.Graphic abstract

Numerical analysis on the performance of Dual Rotor wind turbine

This study investigates the aerodynamic performance of wind turbines aiming to maximize the power extracted from the wind. The study is focusing on the effect of introducing a second rotor to the main rotor of the wind turbine in what is called a dual rotor wind turbine (DRWT). The numerical study took place on the performance of small-scale model of wind turbine of 0.9 m diameter using S826 airfoil.
 Both the Co-rotating and Counter rotating configurations were investigated at different tip speed ratios (TSR) and compared with the performance of the single rotor wind turbine (SRWT). Many parameters were studied for dual rotor turbines. These include the spacing between the two rotors, the pitch angle of the rear rotor and the rotational speed of ratio rear to front rotor. Three-dimensional simulations performed and employed using CFD simulations with Multi Reference Frame (MRF) technique.
 The Co Rotating Wind Turbine (CWT) and Counter Rotating Wind Turbine (CRWT) found to have better performance compared to that of the SRWT with an increase ranging from 12 to 14% in peak power coefficient. Moreover, the effect of changing the pitch angle of the rear rotor on the overall performance found to be of a negligible effect between angles 0⁰ until 2⁰ degrees tilting toward the front rotor. On the other hand, the ratio of rotational speed of the rear rotor to the front rotor found to cause a further increase in the peak performance of the CWT and CRWT ranging from 3 to 5%.

Prediction of aeroacoustic performance of counter-rotating wind turbine by changing the rotational speed of front rotor

This study aims to investigate the aerodynamic and aeroacoustic performance of a counter-rotating wind turbine (CRWT) to define the effect of rotational wind speed of the front rotor on the sound pressure level of CRWT, using CFD simulation. For this purpose, NREL Phase VI wind turbine was considered as the single rotor, and validation of aerodynamic and aeroacoustic simulation has been carried out for the solver. Then, 3D simulation has been applied on single rotor and counter-rotating wind turbines to scrutinize the acoustic level of CRWT by changing the rotational speed of the front rotor. The unsteady flow simulation was carried out with the realizable k–e Reynolds-averaged Navier–Stokes turbulence model, and the calculated flow field data were utilized using Ffowcs Williams–Hawkings model for predicting the acoustic level at receiver location, defined based on the IEC61400-11 standard. The results show that increasing the rotational wind speed of the upstream rotor leads to augmenting the noise emitted from CRWT. On the other hand, for tip speed ratios (TSR) ranging from 6 to 12, with increasing the front rotor RPM, the power coefficient of CRWT enhances, while for the TSR more than 12, an inverse behavior has been observed and power coefficient declines along with increasing front rotor’s speed of revolution.

Analysis Effect Ratio of Rotation Rotors and Tip Speed Ratio (TSR) On The Variations of Distance Rotors Counter Rotating Wind Turbine (CRWT)

One important issue global is climate changes. The reduce climate changes one of them issue of the wind energy utilization is the energy conversion from wind energy. Conversion efficiency of the wind energy usable into productive power. Enhanced technology wind energy development CRWT. The purpose of this paper analysis of the effect ratio of rotation rotors and Tip Speed Ratio (TSR) on the variations rotor distance rotors CRWT. This research was carried out the development of previous research with airfoil series S826 blade modeling from NREL. This research used Gambit Software and solver using ANSYS (FLUENT CFD), used turbulent model k − ε realizable. Results of this research the variations parameters CRWT, distance 0.5-0.1 and show performance maximum wind turbine the rear rotor shows an increase power of the turbine ratio of rotation rotors and TSR.

Design and Simulation of a 1 DOF Planetary Speed Increaser for Counter-Rotating Wind Turbines with Counter-Rotating Electric Generators

The improvement of wind turbine performance poses a constant challenge to researchers and designers in the field. As a result, the literature presents new concepts of wind turbines (WTs), such as: counter-rotating wind turbines (CRWTs) with two coaxial wind rotors revolving in opposite directions, WTs with higher-efficiency and downsized transmission systems, or WTs with counter-rotating electric generators (CREGs). Currently, there are a few solutions of WTs, both containing counter-rotating components; however, they can only be used in small-scale applications. Aiming to extend the use of WTs with counter-rotating wind rotors (CRWRs) and CREGs to medium- and large-scale applications, this paper introduces and analyzes a higher-performance WT solution, which integrates two counter-rotating wind rotors, a 1 degree of freedom (DOF) planetary speed increaser with four inputs and outputs, and a counter-rotating electric generator. The proposed system yields various technical benefits: it has a compact design, increases the output power (which makes it suitable for medium- and large-scale wind turbines) and allows a more efficient operation of the electric generator. The kinematic and static computing methodology, as well as the analytical models and diagrams developed for various case studies, might prove useful for researchers and designers in the field to establish the most advantageous solution of planetary speed increasers for the CRWTs with CREGs. Moreover, this paper extends the current database of WT speed increasers with an innovative concept of 1 DOF planetary gearbox, which is subject to a patent application.

Numerical Analysis on Aerodynamic Performance of Counter-rotating Wind Turbine through Rear Rotor Configuration

Numerical analysis was conducted on the aerodynamic performance and the flow characteristics around the counter-rotating wind turbine or CRWT blade through rear rotor configuration using various rotor diameter ratios and distance ratios to the turbine blade through a CFD (Computational Fluid Dynamics) simulation. CFD simulation showed the normalized power coefficients of the front rotor, rear rotor, and combined rotor (CRWT) to the single rotor with a strong influence of the rear rotor configuration with the addition of tip speed ratio (TSR). A larger average normalized power coefficient takes place at D1/D2=1.0 with L/D1=0.75 by 1.221. It is about 22.1% increased to the SRWT for the given TSR range. Axial velocity contours and resultant velocity vectors around the CRWT blade with a diameter ratio of D1/D2 > 1.0 and a closer rotor distance provide a stronger bound vortex and strong separation around the rear hub blade with a tendency to increase from the hub to the tip blade at low TSR. The higher the TSR, the movement of tip vortex moves closer to the rear tip blade which has the effect of increasing the leakage flow in the area of D1/D2 < 1.0.

Numerical Study on the Performance Of 2-Bladed and 3-Bladed Counter Rotating Wind Turbines

Numerical Study on the Performance Of 2-Bladed and 3-Bladed Counter Rotating Wind Turbines

Numerical investigation on the performance of a small counter-rotating wind turbine

The article presents results of the investigation on the performance of a small counter-rotating wind turbine. Wind turbine has been simulated using Computational Fluid Dynamics methods. Actuator Line Model has been successfully used to represent rotors in computational domain. Parametric study has been carried out, taking into account changes in the tip speed ratio of the rotors while maintaining a constant distance between upwind and downwind rotor. Study results revealed noticeable increase in power coefficient for optimal configuration. Dynamic interaction between rotors has been investigated exposing no significant interference in both torque and power.

Evaluating Performance of Horizontal Axis Double Rotor Wind Turbines

The current work investigates experimentally the performance of a double rotor horizontal axis wind turbine (DRHAWT). A second rotor is added to the traditional horizontal axis wind turbine (HAWT). The second rotor will restore the residual energy left in the wake of the first rotor; hence, increasing the output of the original wind turbine. For this purpose, two arrangements are examined; the first arrangement uses the second rotor directly after the first rotor, where both rotate in the same direction (concurrent), and the second arrangement uses the second rotor, where the rotors rotate in different directions (counter current). Small models are built and tested in the Australian College of Kuwait (ACK) wind tunnel setup. For comparison purposes, the base line one rotor HAWT is tested alone, then the two double rotors arrangements are tested, and the results are presented here. Power output and efficiency of these three designs are calculated and discussed. The experimental results conveyed an increase in the efficiency of the double rotor turbines compared with the single rotor turbine. It is indicated that the efficiency of the single rotor design is merely 15%, which raises to 18.1% for the double rotor counter rotating wind turbine. The efficiency is observed to be slightly more for the counter current double rotor turbine compared with the concurrent design.

Experimental study of local pitch variations on electric power generated by counter rotating wind turbine with single generator without gearbox

Wind energy is one of the clean renewable energy that can be used as an alternative to reduce fossil fuel consumption. The aim of this research was to design and test the performance of counter-rotating wind turbine (CRWT) model corresponded with wind velocity and planned power output. The CRWT has two rotors with a diameter of 0.70 m comprised of NACA 4412 airfoils, which separated by axial distance of 0.3D and connected directly to each shaft of DC generator without a gearbox mechanism. In this research, local pitch (θp) of the rear rotor can be varied as followed (-10°, -5°, 0°, +5° and +10°). The data collection was done in a wind tunnel with a constant wind speed of 4 m/s, and given a load from bulb lamp started from 0 to 4.5 watt every 0.75 watts. The result shows that the local pitch +10° produced the highest rotation and electrical power generated. The highest electrical power generated at a local pitch +10° was at load 0.75 watt in amount of 1.057 watts or 23.55% higher than normal rotor (θp = 0°). At the same load, the lowest electrical power generated was at the local pitch -10° which only produced 0.598 watts.

Comparative analysis of 1DOF vs. 2DOF speed increasers for counter-rotating wind turbines

The paper presents a comparative study on the cinematic and static performance of a new type of planetary speed increaser for wind turbines. In this respect, the analytical modeling of the mechanical response for a counter-rotation wind system consisting of two identical counter-rotating wind turbines, an electric generator with fixed stator and a two-inputs one-output planetary speed increaser which can operate in two distinct situations: as a differential (2DOF) increaser (summing the input speeds) or as a monomobile (1DOF) increaser (summing the input moments) is obtained in the first part. For a numerical case study, the mechanical response of the wind system is simulated in the two stated functional situations, considering 1DOF vs. 2DOF speed increasers. The obtained results show a better energetic behavior of the 1DOF wind system as a result of a higher efficiency, but with a higher degree of load unevenness of the two wind turbines.

Numerical and Experimental Efficiency Evaluation of a Counter-Rotating Vertical Axis Wind Turbine

Numerical and Experimental Efficiency Evaluation of a Counter-Rotating Vertical Axis Wind Turbine

Numerical and Experimental Efficiency Evaluation of a Counter-Rotating Vertical Axis Wind Turbine

This paper investigates the concept of a concentric counter-rotating vertical axis wind turbine (VAWT), consisting of a two stage vertical H-type turbine with three blades on each stage. The model has an inner and an outer stage, rotating in opposition to each other. Both numerical and experimental tests have been performed in order to validate this new concept. Numerical analysis is based on the use of 2.5-dimensional, unsteady simulations using a DOF type of analysis which allows for the two stages to self-adjust their rotation speed. Sliding mesh conformal interfaces are defined between these subdomains to minimize numerical artifacts such as artificial relations or entropy changes. Fully turbulent URANS were carried out in Ansys Fluent software. One key outcome was the momentum coefficient for each stage at different tip wind speed values. Another, more qualitative, outcome is the analysis of vortex shedding, impingement and overall interaction between the stages at different positions and scenarios. Ultimately, the numerical results have been validated using a scaled experimental device which was analyzed in the wind tunnel at different free stream speeds.

CFD analysis of number of blades on the performance of counter rotating wind turbine designed using blade element momentum theory under transient condition

Unsteady CFD simulations on the effects of number of blades on counter rotating wind turbine (CRWT) were carried out in order to investigate the performance and the flow characteristics. In this paper, 2-bladed and 3-bladed CRWT were designed using Blade Element Momentum Theory (BEMT) which comprised of S833, S834, and S835 airfoils. As a comparison baseline, a SRWT model which have similar design with front rotor of the 3-bladed CRWT would be also investigated. It was found that the SRWT had the same rotational speed with the front rotor of the 3-bladed CRWT. There was about 10.24 % and 11.79 % rotational speed reduction of the rear rotor from the front rotor of 2-bladed CRWTs and 3-bladed CRWTs, respectively. Both of 2-bladed CRWT and 3-bladed CRWT have higher total power than SRWT, thereby generating more larger velocity deficits in the wake flow.

Flow-driven simulation on variation diameter of counter rotating wind turbines rotor

Wind turbines model in this paper developed from horizontal axis wind turbine propeller with single rotor (HAWT). This research aims to investigating the influence of front rotor diameter variation (D1) with rear rotor (D2) to the angular velocity optimal (ω) and tip speed ratio (TSR) on counter rotating wind turbines (CRWT). The method used transient 3D simulation with computational fluid dynamics (CFD) to perform the aerodynamics characteristic of rotor wind turbines. The counter rotating wind turbines (CRWT) is designed with front rotor diameter of 0.23 m and rear rotor diameter of 0.40 m. In this research, the wind velocity is 4.2 m/s and variation ratio between front rotor and rear rotor (D1/D2) are 0.65; 0.80; 1.20; 1.40; and 1.60 with axial distance (Z/D2) 0.20 m. The result of this research indicated that the variation diameter on front rotor influence the aerodynamics performance of counter rotating wind turbines.

Analysis Model of a Small Scale Counter-Rotating Dual Rotor Wind Turbine with Double Rotational Generator Armature

Dual rotor wind turbines have higher efficiency and they can harvest more energy compared to single rotor wind turbines. In this study a counter-rotating dual rotor wind turbine with double rotational generator armature is modelled with mechanical, aerodynamical and electrical components. The considered model includes permanent magnet synchronous generator (PMSG) and a drive train which represent the mechanical characteristics of the generator. In a dual rotor wind turbine the front rotor extracts some portion of energy from the wind therefore downstream of the front rotor the speed of the air is decreased. The air with reduced speed downstream of the front rotor acts as an inflow for the rear rotor. The speed of the residual wind downstream of the front rotor affects the power output of the dual rotor wind turbine. The resulting torque, aerodynamic power and also electrical power of the counter-rotating dual rotor wind turbine are simulated using MATLAB/Simulink software.

Investigation of Counter-Rotating Wind Turbine Performance using Computational Fluid Dynamics Simulation

Investigation of the dual rotor counter-rotating wind turbine (CRWT) performance using non-dimensional parameters of the rotor diameter ratio and the rotor axial distance ratio against the characteristics of power coefficient with tip speed ratio (TSR) as input parameters have been successfully carried through CFD simulation. CFD simulation used k-e turbulence realizable with hexahedral meshing to predict the CRWT performance to the rotor diameter ratio of D1/D2< 1, D1/D2 = 1 and D1/D2> 1 and rotor axial distance ratio with the s826 airfoil that has been applied to the single rotor wind turbine. The best CRWT performance obtained on the rotor diameter ratio of D1/D2 = 1.0 with the peak power coefficient of 0.5219 or increased to ∆Cp, max = 16.49% from the single rotor. CRWT performance through the addition of rotor axial distance ratio showed the power coefficient of the front rotor continued to rise closely to the single rotor performance while the rear rotor will continue to decline. However, the overall CRWT performance were relatively stable after the ratio of the distance Z/D1 = 0.5 with the peak power coefficient of 0.5348 or increased to ∆Cp, max = 19.37%.