A CFD analysis for novel close-ended deflector for vertical water turbines

Abstract

The effects of climate change are growing more and more evident, and this is caused by the increase in CO2 emissions. Fossil fuel exhaustion and the need for electricity in remote areas have encouraged researchers to advance and develop the renewable energy sector. One type of clean energy technology is vertical water turbines that have low efficiency. This paper aims to design and simulate a novel close-ended, guided deflector to improve the efficiency of vertical turbines. This research used the dynamic mesh technique to evaluate the concept after the deflector was designed, and a grid independence study, a boundary sensitivity study, and a timestep sensitivity study were implemented to ensure the accuracy of the results. Then, we used the sliding mesh model to determine the performance of four rotors. The results from the dynamic mesh model showed that the straight rotor with the proposed deflector was not suitable for operating in the deflector, and the concept is static and does not rotate. However, the others showed a valid concept in the proposed deflector. For the sliding mesh technique, the results indicated a common trend: all the rotors’ performances increased when tip speed ratio (TSR) increased, and the highest amount of the power coefficient (Cp) was found at higher TSRs, such as 1.3 and 1.4, with around 0.45 in the cross flow type. A three-dimensional simulation was conducted of the cross flow type with the proposed deflector, and a similar trend was found. Nevertheless, around a 5% difference was found between the 3D and 2D results for cross flow. The deflector can significantly improve the performance after 0.7 TSR to reach over 0.42 Cp at 1.3 TSR, whereas, without the deflector, the performance reduces to approximately 0.1 Cp at the same TSR.