ABSTRACT
The computational fluid dynamics (CFD) method with the Improved Delayed Detached Eddy Simulation (IDDES) turbulence model was adopted to investigate the effects of the external diffuser on the power performance and aerodynamic characteristics of a straight-bladed vertical axis wind turbine (VAWT). The behaviors of the diffuser with different types and size parameters were compared. The results showed that the external diffuser could improve the power performance of the VAWT and influence its aerodynamic characteristics. Different types of the diffuser could lead to a distinct effect. Appropriate size parameters of the diffuser could achieve the optimal power performance of the VAWT.
With the continuous depletion of fossil fuels and growing concern about environmental pollution, the utilization of renewable and clean energy has become an important issue for the development of sustainable society (Tummala et al., 2016). Wind energy is widely distributed and has achieved rapid progress in electricity production. For the past several decades, horizontal axis wind turbines (HAWTs) have been the main tool for wind energy conversion and dominated the commercial market. However, vertical axis wind turbines (VAWTs) have gained more attention in recent years due to their simpler structures and lower costs (Li et al., 2016).
Although VAWTs have broad application prospects, the unsatisfactory wind energy conversion efficiency limits their further development. Therefore, many researchers have tried to provide theoretical support for the performance improvement of the VAWT by studying its complex aerodynamics, and the computational fluid dynamics (CFD) method is the most popular numerical approach. Rezaeiha et al. (2018) studied the impact of tip speed ratio on the aerodynamic performance of a typical VAWT with Reynolds-averaged Navier-Stokes (RANS) method. It was found that the reduced tip speed ratio would strongly influence the dynamic load on the blade. Peng and Lam (2016) used the Large Eddy Simulation (LES) method to investigate the turbulence effects on the aerodynamics of the VAWT. The results showed that the turbulence could delay the appearance of dynamic stall by energizing the boundary layers. Lei et al. (2017) reported the differences between the Improved Delayed Detached Eddy Simulation (IDDES) and SST k-ω turbulence models in the aerodynamics prediction for a straight-bladed VAWT. The comparison indicated that the IDDES turbulence model could capture more realistic vortices around the blade.
