Numerical Study of a Novel Concept for Manufacturing Savonius Turbines with Twisted Blades

Abstract

This work presents a numerical study of the aerodynamic performance and the resulting flow field of two novel Savonius wind turbines with twisted blades. The novelty relies on the blade manufacturing process which is characterized by a ‘twisted cut’ through the central axis of a hollow cylinder (tube), followed by a partial twisted cut in the range of 90°. This approach does not require any expensive fabrication process such as blade molding and/or 3D prints, and, therefore, it can potentially mitigate the production costs. The main goal is to investigate the operational parameters and the overall performance of the presented devices, which are currently being operated in atmospheric conditions. For this purpose, three-dimensional simulations have been performed using the open-source CFD library OpenFOAM in order to solve the governing equations and for characterizing the main phenomena involved in the flow pattern. The Reynolds-averaged Navier–Stokes (RANS) approach together with the k − ω SST model were employed to reproduce the flow turbulence effects. This model is validated using wind tunnel measurements of the power ( C P ) and torque ( C M ) coefficients from a straight blade Savonius turbine. Unsteady simulations of the two turbine prototypes were investigated at different tip speed ratio TSR ( λ ) by varying the rotational speed of the rotor while keeping constant the free stream (rated) velocity V ∞ . The results were compared against the Savonius turbine employed for validating the model. Aerodynamic loads and general wake structure were studied at the optimal operational conditions as well. For the same turbine configurations, the new blade geometry improved the performance by 20–25% (at its optimal TSR), compared to the conventional straight blade Savonius rotor, as well as the reducing torque fluctuation.

Experimental Assessment of Suitability of Darrieus and Savonius Turbines for Obtaining Wind Energy from Passing Vehicles

“…Many research centres and wind turbine companies are working on solutions devoid of these drawbacks. A successful modification is the helical turbine [1,37,38] with a helical twist of the blades around the axis of rotation (Figure 7a). Reducing the variability of the driving torque during rotor rotation and increasing the driving torque is achieved by increasing the number of blades to five or even seven.…”

Review of Specific Performance Parameters of Vertical Wind Turbine Rotors Based on the SAVONIUS Type

“…A novel model of wind turbine was presented by Doerffer et al with a constructive solution involving twin rotors showing an efficiency of above 20% corresponding to wind velocity [97]. Following the operating performance increase, the twisted blade rotor model was analyzed, and the results show an improved performance of 20-25% at the optimal TSR compared to the conventional SAVONIUS rotor [98,99].…”

Computational Studies on the Effects of a Central Shaft and a Guiding Wall on the Savonius Hydrokinetic Turbine Performances

“…In fact, the domain size is described in terms of a proportion of a rotor diameter (Dr). The dimension of the domain was designed following the published literature such as, Mendoza et al (2020), Saad et al (2020), Yaakob et al (2010), and so on, to confirm negligible effects of domain walls on the SHKT performances. To assure of the negligible domain wall effect, the bigger the domain size, the better the simulated accuracy.…”