Готові списки джерел за темами / Double Multiple Streamtubes

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Добірка наукової літератури з теми "Double Multiple Streamtubes"

Автор: Grafiati

Опубліковано: 10 березня 2023

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Статті в журналах з теми "Double Multiple Streamtubes"

Paraschivoiu, Ion. "Double-multiple streamtube model for studying vertical-axis wind turbines." Journal of Propulsion and Power 4, no. 4 (July 1988): 370–77. http://dx.doi.org/10.2514/3.23076.

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Roy, Lalit, Kellis Kincaid, Roohany Mahmud, and David W. MacPhee. "Double-Multiple Streamtube Analysis of a Flexible Vertical Axis Wind Turbine." Fluids 6, no. 3 (March 13, 2021): 118. http://dx.doi.org/10.3390/fluids6030118.

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Vertical-axis wind turbines (VAWTs) have drawn increased attention for off-grid and off-shore power generation due to inherent advantages over the more popular horizontal-axis wind turbines (HAWTs). Among these advantages are generator locale, omni-directionality and simplistic design. However, one major disadvantage is lower efficiency, which can be alleviated through blade pitching. Since each blade must transit both up- and down-stream each revolution, VAWT blade pitching techniques are not yet commonplace due to increased complexity and cost. Utilizing passively-morphing flexible blades can offer similar results as active pitching, requiring no sensors or actuators, and has shown promise in increasing VAWT performance in select cases. In this study, wind tunnel tests have been conducted with flexible and rigid-bladed NACA 0012 airfoils, in order to provide necessary input data for a Double-Multiple Stream-Tube (DMST) model. The results from this study indicate that a passively-morphing VAWT can achieve a maximum power coefficient (Cp) far exceeding that for a rigid-bladed VAWT CP (18.9% vs. 10%) with reduced normal force fluctuations as much as 6.9%. Operational range of tip-speed ratio also is observed to increase by a maximum of 40.3%.

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Saber, E., R. Afify, and H. Elgamal. "Performance of SB-VAWT using a modified double multiple streamtube model." Alexandria Engineering Journal 57, no. 4 (December 2018): 3099–110. http://dx.doi.org/10.1016/j.aej.2018.07.009.

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Beri, Habtamu, and Yingxue Yao. "Double Multiple Streamtube Model and Numerical Analysis of Vertical Axis Wind Turbine." Energy and Power Engineering 03, no. 03 (2011): 262–70. http://dx.doi.org/10.4236/epe.2011.33033.

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Kumar, Palanisamy Mohan, Sudhakar Rao Rashmitha, Narasimalu Srikanth, and Teik-Cheng Lim. "Wind Tunnel Validation of Double Multiple Streamtube Model for Vertical Axis Wind Turbine." Smart Grid and Renewable Energy 08, no. 12 (2017): 412–24. http://dx.doi.org/10.4236/sgre.2017.812027.

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Bangga, Galih, Amgad Dessoky, Thorsten Lutz, and Ewald Krämer. "Improved double-multiple-streamtube approach for H-Darrieus vertical axis wind turbine computations." Energy 182 (September 2019): 673–88. http://dx.doi.org/10.1016/j.energy.2019.06.083.

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Cacciali, L., L. Battisti, and S. Dell’Anna. "Free Surface Double Actuator Disc Theory and Double Multiple Streamtube model for in-stream Darrieus hydrokinetic turbines." Ocean Engineering 260 (September 2022): 112017. http://dx.doi.org/10.1016/j.oceaneng.2022.112017.

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Hara, Yutaka, Takafumi Kawamura, Hiromichi Akimoto, Kenji Tanaka, Takuju Nakamura, and Kentaro Mizumukai. "Predicting Double-Blade Vertical Axis Wind Turbine Performance by a Quadruple-Multiple Streamtube Model." International Journal of Fluid Machinery and Systems 7, no. 1 (March 31, 2014): 16–27. http://dx.doi.org/10.5293/ijfms.2014.7.1.016.

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Ayati, Anis A., Konstantinos Steiros, Mark A. Miller, Subrahmanyam Duvvuri, and Marcus Hultmark. "A double-multiple streamtube model for vertical axis wind turbines of arbitrary rotor loading." Wind Energy Science 4, no. 4 (December 11, 2019): 653–62. http://dx.doi.org/10.5194/wes-4-653-2019.

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Анотація:

Abstract. We introduce an improved formulation of the double-multiple streamtube (DMST) model for the prediction of the flow quantities of vertical axis wind turbines (VAWT). The improvement of the new formulation lies in that it renders the DMST valid for any induction factor, i.e., for any combination of rotor solidity and tip speed ratio. This is done by replacing the Rankine–Froude momentum theory of the DMST, which is invalid for moderate and high induction factors, with a new momentum theory recently proposed, which provides sensible results for any induction factor. The predictions of the two DMST formulations are compared with VAWT power measurements obtained at Princeton's High Reynolds number Test Facility, over a range of tip speed ratios, rotor solidities, and Reynolds numbers, including those experienced by full-scale turbines. The results show that the new DMST formulation demonstrates a better overall performance, compared to the conventional one, when the rotor loading is moderate or high.

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Dyachuk, Eduard, and Anders Goude. "Simulating Dynamic Stall Effects for Vertical Axis Wind Turbines Applying a Double Multiple Streamtube Model." Energies 8, no. 2 (February 11, 2015): 1353–72. http://dx.doi.org/10.3390/en8021353.

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Більше джерел

Дисертації з теми "Double Multiple Streamtubes"

Wendler, Ernst Richard Georg. "Variations on the double-multiple streamtube model for Darrieus straight-bladed vertical-axis wind turbines to improve predictions of performance and flow expansion." Tesis, Universidad de Chile, 2014. http://repositorio.uchile.cl/handle/2250/132048.

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Анотація:

Magíster en Ciencias de la Ingeniería, Mención Mecánica
Ingeniero Civil Mecánico
El propósito del presente trabajo es formular una herramienta computacional de bajo costo que determine la potencia y la expansión de flujo de turbinas eólicas de eje vertical (VAWTs) tipo Darrieus. Esta herramienta puede ser útil para predecir el desempeño aerodinámico de VAWTs en ambientes urbanos o en granjas eólicas. En este trabajo se realizan variaciones en el modelo doble-múltiple tubos de corriente (DMS) para turbinas Darrieus de álabes rectos (SB-VAWTs) con el fin de mejorar las predicciones de desempeño aerodinámico y expansión del flujo. Se presentan los antecedentes generales y el marco teórico del modelamiento de las Darrieus SB-VAWTs. El caso de referencia está compuesto por las mediciones de campo de una Darrieus SB-VAWT de 12 kW (6 m de diámetro) encontradas en la literatura y las simulaciones computacionales bidimensionales realizadas en el software ANSYS Fluent 13.0. Se plantea y verifica una representación matemática de las líneas de corriente para modelar el promedio temporal de la expansión de flujo alrededor de SB-VAWTs. Se presenta una nueva formulación del modelo DMS basado en momentum con expansión de flujo. El desempeño aerodinámico y la expansión de flujo son calculados en MATLAB utilizando coeficientes aerodinámicos empíricos y los resultados de las simulaciones computacionales. Se propone una nueva formulación del modelo DMS basado en la conservación de energía mecánica. Ambas formulaciones estudiadas presentan problemas de convergencia para altas razones de velocidades de punta de álabe. Las predicciones de expansión de flujo se encuentran alejadas de las obtenidas en las simulaciones computacionales. Se cuantifica e interpreta el error de los modelos DMS basados en momentum y en energía al imponer la expansión obtenida por las simulaciones computacionales. A partir de los datos de fuerza en el sentido del flujo y la expansión de los tubos de corriente, se propone una ecuación alternativa para el balance de momentum lineal considerando un modelo de múltiples tubos de corriente. Dicha relación permite la convergencia y una buena estimación de la expansión del flujo para todas las velocidades de rotación de turbina estudiadas. Se recomienda como trabajo futuro el mejoramiento del cálculo de las fuerzas aerodinámicas basadas en coeficientes aerodinámicos empíricos considerando los efectos dinámicos.

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Brinck, Daniel, and Nicklas Jeremejeff. "The development of a vertical axis tidal current turbine." Thesis, KTH, Energiteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-134361.

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Globally the amount of electricity produced each year is increasing significantly. Between 1980 and 2010 the average increase was 407 billion kWh per year. To be able to meet this increasing electricity demand, without burdening the environment in a too large extent, the research and development of renewable energy production techniques is of great importance. In the light of this we wanted to dedicate our master thesis to help SubseaTechnology Scandinavia AB with the development of a vertical axis tidal current turbine. The project set out to do the initial design proposal of a 2 x 4 meter H-shaped Darrieus turbine by applying the Double Multiple Streamtube model. The optimization process was performed with the aid of MATLAB for four different foils. The study included two symmetrical foils; NACA 0012 and S-1046 together with two asymmetrical foils; S-1210 and E216. The parameters studied were the number of blades, chord length, tip speed ratio, fixed pitch and the operational range. In the project, effects such as blade to wake interaction, torque fluctuations etc. were also considered. From the simulations the two bladed turbine fitted with the S-1046 hydrofoil showed the highest performance but was struggling with an unfavorable oscillating torque. In the light of this the three bladed turbine fitted with the S-1046 hydrofoil with a chord of 0.13 m and an optimal tip speed ratio of 3.2 was determined. From the simulations the power coefficient reached 53.47 % for this case. This configuration also showed good performance in a relatively wide range of both tip speed ratios and free stream velocities. The model does not include several effects causing losses and the power coefficients calculated in this model are to be used as a comparison between the different turbine configurations and not as absolute values of performance. The simulations showed good potential for the use of asymmetrical foils in vertical axis turbines. The performance was evaluated for the upstream half of the turbine where the E216 foil exceeded the symmetrical foils in the range of ten percentage points.

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Gonzalez, Campos Jose Alberto. "Design and Experimentation of Darrieus Vertical Axis Wind Turbines." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1594690510943748.

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Chen, Chia-Hong, and 陳佳宏. "Investigation of 3-Dimensional Effect on Double Multiple Streamtubes Model." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/s9g9f3.

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Анотація:

碩士
國立中興大學
機械工程學系所
101
Costly computation cost and uncerrtainly accuracy are the important issue of CFD to predict aerodynamics of vertical-axis wind turbine. A mathematical modulus is the most effective method. Double-Multiple Streamtube Theory is the most accurate theory adopt by industries currently. For the continuity of the modification made by dynamic stall models, this paper focused on effect of the spanwise variation of the aerodynamics due to the vortex generated at wing tip on vertical wind turbines. To achieve this goal, the blade was divided spanwise into multiple streams layer, and the lifting line theory and Viterna & Corregian stall model was used to modified DMST in each stream layer. A computer program was written accordingly and a CFD was used as virtual wind tunnel to compare the effect at wind speed of 12 m/s with different tip speed ratio.

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Huang, Sin-Hun, and 黃信豪. "Investigation of Dynamic Stall Models on Double Multiple-Streamtubes Model Application." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/gzzfh9.

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BIANCHINI, ALESSANDRO. "Performance Analysis and Optimization of a Darrieus VAWT." Doctoral thesis, 2010. http://hdl.handle.net/2158/600180.

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Анотація:

Increasing research efforts are being devoted to understand where small-size wind turbines can effectively represent an alternative for delocalized power production and emissions reduction, particularly when applied in new installation contexts (e.g. the built environment). In current eolic research, Darrieus VAWTs are particularly appreciated, thanks to the possibility of producing small machines with high reliability and almost no noise. In addition, a wider range of design solutions can be exploited in order to obtain an appealing exterior design and consequently to reduce the visual impact of the installation. As a result, many efforts are being made to develop industrially-designed turbines with a reduced environmental impact and a competitive cost; moreover, in order to ensure an effective diffusion of small Darrieus turbines, the overall performance, and especially the start-up and transient behavior, still need to be improved. Within this context, pushed by several industrial Italian partners, interested in developing innovative Darrieus turbines, a multipurpose research activity was carried out. In particular, the research project was aimed at analyzing in depth the physics and the functioning behavior of small-size Darrieus turbines, whose design process is affected by several additional criticalities in comparison to that of greater machines or of more conventional horizontal-axis rotors. Inter alia, small rotors are in fact deemed to be affected by a reduced power capacity and by lacks of self-starting capabilities, mainly due to the their reduced dimensions (i.e. small swept areas, chord lengths and diameters) and to frequently unfavorable conditions (i.e. low towers heights and complex orography of the installation contexts). To this purpose, was preliminary undertaken a theoretical analysis of the physical fundamentals which regulate the functioning of Darrieus VAWTs, dedicated to highlight the critical characteristics of these machines and the relative impact of the main design parameters. Efforts were therefore directed to create a reliable numerical tool which could be able to effectively model the behavior of H-Darrieus turbines during both the normal functioning and the transient phases. Within this activity, a numerical code, denoted VARDAR, was developed on the basis of the Momentum Theory; more in details, a Double Multiple Streamtubes approach was exploited for the turbine modeling, together with the possibility to account for the dynamic stall of the airfoils during the revolution and the width expansion of the streamtubes. In addition, due to the relevant impact of the secondary and parasitic effects on the performance estimation of small VATWs, several original sub-models to account for these effects were purposefully developed; inter alia, specific models for the shadowing effect of the central tower and for the parasitic torque of the rotating struts were realized. Furthermore, an innovative numerical routine was created in order to to simulate the time-dependent functioning of the rotor under a generic oncoming wind, with particular reference to the startup transitory. All the theoretical conjectures and the developed numerical models have been experimentally validated by means of several extensive test campaigns in two large wind tunnels in Italy on properly deigned 1:1 scale models of H-Darrieus rotors with either two or three blades. An impressive agreement between experimental evidence and simulated data was constantly found and all the developed models were therefore satisfactorily validated. Moving from this theoretical background, the attention was focused on developing new aerodynamic solutions which could partially solve the main critical aspects in designing a new turbine. Within this context, a new aerodynamic airfoil was designed by means of a CFD optimization, aimed at improving the airfoil performance for the working conditions (i.e. Reynolds numbers and incidence angle) on board of a Darrieus rotor. The static polar curves of the new profile over the whole range of the angle of attack (0°-360°) were measured in the wind tunnel, achieving interesting results in terms of lift increase and stall angle delay. Specific analyses were also directed to evaluate the parasitic torque of non-aerodynamic structures during the revolution; by means of both numerical analyses and experimental tests, an extended experimental study was carried out to investigate the most convenient shapes of the turbine struts. In particular, different hulls geometries were compared in terms of torque detriment and of impact on the self-starting behavior of the machine. Finally, the experience collected during the research activity, was synthetized in two original theoretical studies. In the first analysis, the startup behavior of a three-bladed H-Darrieus turbine was investigated and the self-starting capabilities of the rotor were related to its main design parameters. In the second contribution, a new model to account for the virtual camber effect on the performance estimation of H-Darrieus rotors using the momentum theory was developed. In particular, a transition point, based on the flow field characteristics around the airfoil, has been highlighted, below which a different estimation of the virtual camber effect must be adopted to ensure a more realistic description of the first part of the characteristic curve of the machine: on the basis of experimental evidence, the proposed model seems to represent a necessary condition for a correct description of the transient behavior of the turbine, especially in the startup phase.

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Частини книг з теми "Double Multiple Streamtubes"

Ponta, Fernando, and Julian Seminara. "Double-Multiple Streamtube Model for Variable-Geometry Oval-Trajectory Darrieus Wind-Turbines." In World Renewable Energy Congress VI, 2308–11. Elsevier, 2000. http://dx.doi.org/10.1016/b978-008043865-8/50499-2.

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Тези доповідей конференцій з теми "Double Multiple Streamtubes"

Soraghan, Conaill E., William E. Leithead, Julian Feuchtwang, and Hong Yue. "Double Multiple Streamtube Model for Variable Pitch Vertical Axis Wind Turbines." In 31st AIAA Applied Aerodynamics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2013. http://dx.doi.org/10.2514/6.2013-2802.

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Marten, David, Alessandro Bianchini, Georgios Pechlivanoglou, Francesco Balduzzi, Christian Navid Nayeri, Giovanni Ferrara, Christian Oliver Paschereit, and Lorenzo Ferrari. "Effects of Airfoil’s Polar Data in the Stall Region on the Estimation of Darrieus Wind Turbine Performance." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56685.

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Анотація:

Interest in vertical-axis wind turbines (VAWTs) is experiencing a renaissance after most major research projects came to a standstill in the mid 90’s, in favour of conventional horizontal-axis turbines (HAWTs). Nowadays, the inherent advantages of the VAWT concept, especially in the Darrieus configuration, may outweigh their disadvantages in specific applications, like the urban context or floating platforms. To enable these concepts further, efficient, accurate, and robust aerodynamic prediction tools and design guidelines are needed for VAWTs, for which low-order simulation methods have not reached yet a maturity comparable to that of the Blade Element Momentum Theory for HAWTs’ applications. The two computationally efficient methods that are presently capable of capturing the unsteady aerodynamics of Darrieus turbines are the Double Multiple Streamtubes (DMS) Theory, based on momentum balances, and the Lifting Line Theory (LLT) coupled to a free vortex wake model. Both methods make use of tabulated lift and drag coefficients to compute the blade forces. Since the incidence angles range experienced by a VAWT blade is much wider than that of a HAWT blade, the accuracy of polars in describing the stall region and the transition towards the “thin plate like” behaviour has a large effect on simulation results. This paper will demonstrate the importance of stall and post-stall data handling in the performance estimation of Darrieus VAWTs. Using validated CFD simulations as a baseline, comparisons are provided for a blade in VAWT-like motion based on a DMS and a LLT code employing three sets of post-stall data obtained from a wind tunnel campaign, XFoil predictions extrapolated with the Viterna-Corrigan model and a combination of them. The polar extrapolation influence on quasi-steady operating conditions is shown and azimuthal variations of thrust and torque are compared for exemplary tip-speed ratios (TSRs). In addition, the major relevance of a proper dynamic stall model into both simulation methods is highlighted and discussed.

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Coiro, Domenico, Fabrizio Nicolosi, Agostino De Marco, Stefano Melone, and Francesco Montella. "Flow Curvature Effect on Dynamic Behaviour of a Novel Vertical Axis Tidal Current Turbine: Numerical and Experimental Analysis." In ASME 2005 24th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2005. http://dx.doi.org/10.1115/omae2005-67193.

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This paper presents a summary of the work done by the authors regarding the design, construction and test of vertical axis hydro turbines to exploit tidal currents. Double Multiple Streamtube (DMS) model and Vortex model have been used to predict turbines performances either with fixed blades or with self-acting variable pitch blades. Within the DMS model, VAWT and VAWT_dyn codes have been developed to analyze steady and dynamic performances; within Vortex model, VAT-VOR3D code has been developed. Theoretical analysis and numerical predicted performances have been compared and validated with experimental test results on both model and real scale turbines. A comparison between DMS and Vortex model results has been presented. Moreover, the recent activities in terms of numerical investigations on the flow curvature effects are presented.

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Hara, Yutaka, Takahiro Suzuki, Yuki Ochiai, and Tsutomu Hayashi. "Velocity Field Measurements in Wake of a Straight-Bladed Vertical Axis Wind Turbine." In ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-07002.

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Small vertical axis wind turbine (VAWT) is promising for the development of wind energy in the built environment due to its insensitivity to yaw. In general, computer codes based on the blade element and momentum (BEM) theory, which have much less calculation time than CFD codes, are used for design and performance prediction of wind turbines. However, the results on small VAWTs obtained by the BEM theory often do not accord with the experimental results due to the low Reynolds number, the dynamic stall effects, and so forth. The three-dimension nature of the flow field around the VAWT rotor may be one of the reasons for the discord. This study aims to elucidate the actual flow field around small VAWT. In this study, velocity field measurements were carried out in the wake of a small straight-bladed VAWT by using an ultrasonic anemometer. The measurements of the V and W velocity components showed the downwash and the blow-up, which proceeded toward the equator level and merged into the horizontal flow. Counter flow of the U component was also observed in the mainstream direction. The wake velocity profile simulated by using the Double-Multiple Streamtube (DMS) model based on the BEM theory showed a similar behavior to that of the measured wake. However, the high thrust coefficient estimated from the measured deficit in the U velocity component almost doubles the estimation by the BEM theory.

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Collu, Maurizio, Michael Borg, Andrew Shires, and Feargal P. Brennan. "FloVAWT: Progress on the Development of a Coupled Model of Dynamics for Floating Offshore Vertical Axis Wind Turbines." In ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-10717.

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In the present article, progress on the development of an aero-hydro-servo-elastic coupled model of dynamics for floating Vertical Axis Wind Turbines (VAWTs) is presented, called FloVAWT (Floating Vertical Axis Wind Turbine). Aerodynamics is based on Paraschivoiu’s Double-Multiple Streamtube (DMST) model [1] [2], relying on blade element momentum (BEM) theory, but also taking into account three-dimensional effects, dynamic stall, and unsteady wind profiles and platform motions. Hydrodynamics is modelled with a time domain seakeeping model [3], based on hydrodynamic coefficients estimated with a frequency analysis potential method. In this first phase of the research program, the system is considered a rigid body. The mooring system is represented through a user defined force-displacement relationship. Due to the lack of experimental data on offshore floating VAWTs, the model has initially been validated by taking each module separately and comparing it against known experimental data, showing good agreement. The capabilities of the program are illustrated through a case study, giving an insight on the relative importance of aerodynamics loads and gyroscopic effects with respect to hydrodynamic load effects.

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Marten, David, Juliane Wendler, Georgios Pechlivanoglou, Christian Navid Nayeri, and Christian Oliver Paschereit. "Development and Application of a Simulation Tool for Vertical and Horizontal Axis Wind Turbines." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-94979.

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A double-multiple-streamtube vertical axis wind turbine simulation and design module has been integrated within the open-source wind turbine simulator QBlade. QBlade also contains the XFOIL airfoil analysis functionalities, which makes the software a single tool that comprises all functionality needed for the design and simulation of vertical or horizontal axis wind turbines. The functionality includes two dimensional airfoil design and analysis, lift and drag polar extrapolation, rotor blade design and wind turbine performance simulation. The QBlade software also inherits a generator module, pitch and rotational speed controllers, geometry export functionality and the simulation of rotor characteristics maps. Besides that, QBlade serves as a tool to compare different blade designs and their performance and to thoroughly investigate the distribution of all relevant variables along the rotor in an included post processor. The benefits of this code will be illustrated with two different case studies. The first case deals with the effect of stall delaying vortex generators on a vertical axis wind turbine rotor. The second case outlines the impact of helical blades and blade number on the time varying loads of a vertical axis wind turbine.

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Goude, Anders, Emilia Lalander, and Mats Leijon. "Influence of a Varying Vertical Velocity Profile on Turbine Efficiency for a Vertical Axis Marine Current Turbine." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79406.

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Water currents in e.g. unregulated rivers and tides are a considerable renewable energy resource. The technology needed to harness the energy in these streams has not yet matured, but research and development are ongoing. In the present paper the power coefficient of marine current turbines using vertical axis turbines is considered. When the width and height of the turbine are kept constant, the Cp-λ curve will depend mainly on the solidity. However, since all natural channels have vertical velocity variations due to friction against the sea floor, this will also affect the efficiency. The double multiple streamtube model was used to study the power coefficient as a function of solidity and vertical shear profile. Three turbine cases were studied: one turbine vertically aligned, and two horizontally aligned turbines rotating with opposite direction. The results show that the difference depends both on how much the velocity varies over the velocity profile, and on the shape of the velocity profile, where a linear profile causes a lower Cp compared to a logarithmic profile. The difference was especially prominent at low tip speed ratios for the horizontally aligned turbines with different rotational direction.

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Chen, Jim Shih-Jiun, Zhi Chen, Saroj Biswas, Jiun-Jih Miau, and Cheng-Han Hsieh. "Torque and Power Coefficients of a Vertical Axis Wind Turbine With Optimal Pitch Control." In ASME 2010 Power Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/power2010-27224.

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Vertical axis wind turbines (VAWT) have been valued in recent years for their low manufacturing cost, structural simplicity and convenience of applications in urban settings. Despite their advantages, VAWTs have several drawbacks including low power coefficient, poor self-starting ability, negative torque and the associated cyclic stress at certain azimuth angles. Using pitch control ideas, our research is aimed at solving the above problems. In this study, a small-scale Giromill VAWT using three NACA-0015 airfoils with a cord length of 0.09 m and a wind turbine radius of 0.6 m is investigated. During each rotation, the angle of attack depends on the wind velocity, angular velocity and current azimuth angle for each turbine blade. Negative torques at certain angles are attributed to the inherent unsteady aerodynamic behavior at high angles of attack. Without optimal pitch control, the Double-Multiple Streamtube (DMS) model predicts negative torques at certain azimuth angles and very low power coefficients for tip speed ratios below 2.5. The unfavorable negative torques are eliminated using an optimal pitch control strategy, which maximizes the tangential force coefficients and thus the torque coefficients by iterations of all possible relative angles of attack for various tip speed ratios. As a result, the power coefficient is significantly improved especially at low tip speed ratios in the range of zero to three (λ = 0 – 3). Blade pitch control can also solve the self-starting problem and reduce the vibration of vertical axis wind turbines.

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Roy, Sukanta, Hubert Branger, Christopher Luneau, Denis Bourras, and Benoit Paillard. "Design of an Offshore Three-Bladed Vertical Axis Wind Turbine for Wind Tunnel Experiments." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61512.

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The rapid shrinkage of fossil fuel sources and contrary fast-growing energy needs of social, industrial and technological enhancements, necessitate the need of different approaches to exploit the various renewable energy sources. Among the several technological alternatives, wind energy is one of the most emerging prospective because of its renewable, sustainable and environment friendly nature, especially at its offshore locations. The recent growth of the offshore wind energy market has significantly increased the technological importance of the offshore vertical axis wind turbines, both as floating or fixed installations. Particularly, the class of lift-driven vertical axis wind turbines is very promising; however, the existing design and technology is not competent enough to meet the global need of offshore wind energy. In this context, the project AEROPITCH co-investigated by EOLFI, CORETI and IRPHE aims at the development of a robust and sophisticated offshore vertical axis wind turbine, which would bring decisive competitive advantage in the offshore wind energy market. In this paper, simulations have been performed on the various airfoils of NACA 4-series, 5-series and Selig profiles at different chord Reynolds numbers of 60000, 100000 and 140000 using double multiple streamtube model with tip loss correction. Based on the power coefficient, the best suitable airfoil S1046 has been selected for a 3-bladed vertical axis wind turbine. Besides the blade profile, the turbine design parameters such as aspect ratio and solidity ratio have also been investigated by varying the diameter and chord of the blade. Further, a series of wind tunnel experiments will be performed on the developed wind turbine, and the implementation of active pitch control in the developed turbine will be investigated in future research.

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Lundin, Staffan, Ma˚rten Grabbe, Katarina Yuen, and Mats Leijon. "A Design Study of Marine Current Turbine-Generator Combinations." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79350.

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Marine currents are an offshore source of renewable energy of increasing importance, with the development of technology for electricity generation from tidal currents or low-head river currents advancing at a quick pace. Two of the major components of a marine current power plant are the generator and the turbine. It is not sufficient to design these components separately, but a system approach, where the power plant is seen as one entity, must be taken to achieve best overall efficiency. In the present paper, the performance of three different combinations of direct-driven permanent magnet generator with cross-stream axis marine current turbine is examined numerically under the variation of water flow speed. The design case chosen is that of a shallow river or tidal channel, where the cross-sectional area limits the physical size of the power plant. The units are designed for a power output of 10 kW at a water current velocity of 1 m/s. Turbines for three different rotational speeds are considered, each in combination with a corresponding generator. The three turbine-generator systems are designed according to similar design criteria to allow for comparisons. The turbines are modelled using an in-house code, based on the double multiple streamtube model. Corrections are made due to the finite aspect ratio and tip losses of the blades. Experimental data for the lift and drag coefficients for different Reynolds numbers are used in the model. The generators are modelled using a FEM tool that has been validated with experimental results. The three generators are designed for the same nominal voltage and with a low load angle to allow for overload operation. The overall performance of each of the three systems is studied under varying flow velocity. The main conclusion is that all three machines exhibit essentially the same performance behaviour, which means that the choice of nominal operational speed for a power plant will not be a major design constraint. Turbines with higher rotational speed allow for a more compact generator design within the limits of the design parameters used in this study. However, this also entails certain mechanical constraints on the turbine. Due to the restricted cross-sectional area in the channel, it is clear that at least one of the three systems would have to be placed with the axis of rotation in a horizontal rather than vertical position.

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