Abstract
In this work, 3D models in classic configuration of Bach and Benesh rotor type, as well as models with modified blade pattern geometry were analyzed from the air circulation point of view inside the rotor enclosure in order to identify the operating parameters differences according to rotor geometric modified configuration. Constructive design aspects are presented, as well as results obtained from the virtual model analysis in terms of circulation velocity and pressure values which enhance rotor operation related to torque and power coefficients. The rotors design pattern is made according to previous results obtained by different researchers who have performed numerical analysis on virtual models and tests on the experimental rotor models using the wind tunnel. The constructive solutions are describing two-bladed rotor models, in four new designed constructive variants and analyzed using ANSYS CFX. The air velocity specific values, static and total pressure recorded at the rotor blade level are highlighted, that influence the obtaining of rotor shaft torque and power. Also torque coefficient (CT) and power coefficient (CP) values according with specific values of tip speed ratio (TSR) are presented for each analyzed case. The analysis results show higher power coefficient values for analyzed Bach V2 and Benesh V2 rotor modified models compared to the classic Bach and Benesh models for 0.3 TSR of 0.11–012 CP, 0.4 TSR of 0.18 CP (Benesh V2 model) and 0.27 CP at 0.6 TSR (Bach V2). The resulted values confirm that Benesh V2 model offers higher CP up to 5% at TSR 0.3, 2% at TSR 0.6 and 3% at TSR 0.4 compared to the Benesh classical model. The Bach V2 model offers 4% higher CP compared to the classic Bach model at TSR 0.6. Based on these results it is intended the further analytical and experimental research in order to obtain optimal rotor pattern.
Highlights
Following the CFD analysis, the specific results are obtained which are presented in terms of air circulation velocity and pressure at the rotor level for each analyzed case separately
The numerical results obtained for torque (CT) and power coefficient (CP) recorded for each analyzed model are obtained depending on different tip speed ratio (TSR) values
The results obtained for air velocity and pressure at the level of the analyzed fluid region containing the rotor show the current path-lines formed on the main flow direction from the inlet to the exit area, having changes within the rotor region, depending on the geometrical configuration of the blades
Summary
The force generated by the atmospheric air masses movement represent a considerable resource that currently is still underused at the global level in order to obtain energy.In time, multiple solutions have been developed that can capture the wind force and turn it into mechanical rotational energy at the axis of a rotor.From the constructive point of view, the main wind turbine types can be differentiated by the manner in which the rotor is positioned with the rotation axis in a horizontal direction defining the horizontal axis wind turbines (HAWT) or in vertical direction describing the vertical axis wind turbines (VAWT).In 1931, the Finnish engineer Siguard Savonius presented in detail the model of S-shaped in section view turbine rotor propeller, as a vertical axis rotor considered to be driven by drag forces (Abraham et al 2012) and the operating performance of the rotor is influenced by the constructive geometrical conditions and by the air circulation parameters [1].Energies 2020, 13, 2311; doi:10.3390/en13092311 www.mdpi.com/journal/energiesThe Savonius turbine rotor has many advantages over simple construction and low cost.The operation of the Savonius type rotor is independent of the wind direction, benefiting from easy starting with good torque values even at low wind velocities. Multiple solutions have been developed that can capture the wind force and turn it into mechanical rotational energy at the axis of a rotor. In 1931, the Finnish engineer Siguard Savonius presented in detail the model of S-shaped in section view turbine rotor propeller, as a vertical axis rotor considered to be driven by drag forces (Abraham et al 2012) and the operating performance of the rotor is influenced by the constructive geometrical conditions and by the air circulation parameters [1]. The operation of the Savonius type rotor is independent of the wind direction, benefiting from easy starting with good torque values even at low wind velocities
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