vorteks yöntemleri neden gerekli

vorteks yöntemleri neden gerekli - L...

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L. Battisti e-mail: [email protected] L. Zanne S. Dell’Anna DIMS, Faculty of Engineering, Universita ` degli Studi di Trento, Via Mesiano 77, I-38050 Povo (TN), Italy V. Dossena e-mail: [email protected] G. Persico B. Paradiso Laboratorio di Fluidodinamica delle Macchine, Dipartimento di Energia, Politecnico di Milano, Via Lambruschini 4, I-20158, Milano, Italy Aerodynamic Measurements on a Vertical Axis Wind Turbine in a Large Scale Wind Tunnel This paper presents the first results of a wide experimental investigation on the aerody- namics of a vertical axis wind turbine. Vertical axis wind turbines have recently received particular attention, as interesting alternative for small and micro generation applica- tions. However, the complex fluid dynamic mechanisms occurring in these machines make the aerodynamic optimization of the rotors still an open issue and detailed experi- mental analyses are now highly recommended to convert improved flow field comprehen- sions into novel design techniques. The experiments were performed in the large-scale wind tunnel of the Politecnico di Milano (Italy), where real-scale wind turbines for micro generation can be tested in full similarity conditions. Open and closed wind tunnel con- figurations are considered in such a way to quantify the influence of model blockage for several operational conditions. Integral torque and thrust measurements, as well as detailed aerodynamic measurements were carried out to characterize the 3D flow field downstream of the turbine. The local unsteady flow field and the streamwise turbulent component, both resolved in phase with the rotor position, were derived by hot wire measurements. The paper critically analyses the models and the correlations usually applied to correct the wind tunnel blockage effects. Results highlight that the presently available theoretical correction models do not provide accurate estimates of the blockage effect in the case of vertical axis wind turbines. The tip aerodynamic phenomena, in par- ticular, seem to play a key role for the prediction of the turbine performance; large-scale unsteadiness is observed in that region and a simple flow model is used here to explain the different flow features with respect to horizontal axis wind turbines. [DOI: 10.1115/1.4004360] Keywords: VAWT, blockage, wind Tunnel, wind turbine, aerodynamic measurements, unsteady flows 1 Introduction In recent years a renewed interest has arisen on vertical axis concept in wind turbines (VAWT). In the urban environment, affected by highly turbulent flows and strong vertical velocity gra- dients, VAWT claims for several advantages: insensitivity to yaw, ability to withstand rapid changes of wind direction and to provide good performances also in skewed flows [ 1 ], low noise emission due to low tip speed ratios [ 2 ]. Finally the better integration in ar- chitectural projects also represents a key advantage.
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