Numerical and experimental analysis of a diffuser-augmented micro-hydro turbine

Abstract

In the current work, a micro-horizontal axis diffuser-augmented turbine (MHDT) system for renewable energy applications of marine or river stream systems is designed and analyzed through computational fluid dynamics (CFD) and experiment. A bare and diffuser-augmented turbines were applied to MHDT through full-scale experimental model tests, showing agreement with numerical results (the average deviation did not exceed a value of 6%) and verifying the reliability of the numerical method. Several diffuser-augmented turbines with varied camber (f) and angle of attack (α) were analyzed using ANSYS-Fluent. It is found that both f and α have a great impact on the hydrodynamic performance of a diffuser-augmented turbine, which can significantly enhance power and axial force levels and which affects the variation of the power coefficient curve. Additionally, diffuser performance is not only directly linked to its shape design but also to its interactions with the rotor. Critical interaction factors ac (the axial induction factor when a bare turbine and a diffuser-augmented turbine has the same CP at a tip speed ratio) based on the CFD results are proposed to offer a clearer explanation of the energy extraction performance of a diffuser-augmented turbine.