Analysis and optimization of vertical-axis and cross-flow turbines performance with numerical computations
This thesis has been directed by G. Balarac. and S. Barre & C. Bonamy. This work was supported by the company HydroQuest (CIFRE) and N. Guillaud was the industrial contact.
Abstract :
This thesis focuses on the analysis and optimization of the performances of a vertical-axis and cross-flow turbine (VAT) by means of numerical simulations. The highly
unsteady and turbulent nature of the flows involved inside a VAT makes their modeling complex. Several numerical methods with distinct turbulence approaches have
therefore been used in order to evaluate VAT performances. URANS simulations and Large-Eddy Simulations (LES) have been performed with OpenFoam and YALES2, respectively. To improve the VAT design, two lines of research were investigated. Initially, a single-rotor configuration was optimized using LES by studying two specific rotor geometries: a “classic” H-shape Darrieus rotor and an “innovative” rotor. This study provided a better understanding of the overall flow dynamics within a VAT according to the flow regime. Thanks to a local loss analysis, the performances gap between both rotors was quantified. A good agreement with experimental observations was found, in particular a gain of the “innovative” rotor of about +30% on the power coefficient (Cp). Secondly, several double-rotor configurations, each consisting of two counter-rotating rotors, were optimized through URANS simulations. Various geometric parameters (inter-axis distance, counter-rotational direction, central mast) were tested in order to maximize the total power extracted by the machine. A “synergy” effect was observed in twin-rotor configuration leading to a power gain of around +10% compared to a single-rotor VAT. A detailed flow analysis linked the optimal counter-direction with the turbine solidity. This work, carried out in
collaboration with the HydroQuest company, has then led to a local performance optimization, by directly modifying the design of the rotor and a more global enhancement on double-rotor configurations tending towards the optimization of a wind/tidal farm.
Membres du jury :
Mme. Sandrine AUBRUN, Professeure des Universités, École Centrale de Nantes, Examinatrice
M. Christophe CORRE, Professeur des Universités, École Centrale de Lyon, Examinateur
M. Éric GONCALVES, Professeur des Universités, ISAE-ENSMA, Rapporteur
M. Dominique THEVENIN, Professeur des Universités, Université de Magdebourg, Rapporteur
M. Guillaume BALARAC, Maître de Conférences, Grenoble INP, Directeur de thèse
M. Stéphane BARRE, Chargé de Recherche, CNRS, Codirecteur de thèse
M. Cyrille BONAMY, Ingénieur de Recherche, CNRS, Membre invité
M. Nathanaël GUILLAUD, Ingénieur R&D, HydroQuest, Membre invité