Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Actuator line method for diffuser-augmented turbines
Submission Author:
Matheus Nunes , DF
Co-Authors:
Matheus Nunes, Ramiro Bertolina, Antonio Brasil Junior, Taygoara Oliveira
Presenter: Matheus Nunes
doi://10.26678/ABCM.COBEM2023.COB2023-0530
Abstract
Diffuser-augmented turbines are an effective way of increasing power output in horizontal turbines. By surrounding the rotor with a diffuser, the incoming flow is accelerated, increasing the effective area over which the flow acts on the rotor blades. To further optimize the performance of these turbines, it is crucial to design the diffuser shape that generates the maximum power coefficient. However, current methods for diffuser optimization can be costly in terms of materials and time for evaluation. To address this issue, we propose a cost-effective approach using the Actuator Line Method. The methodology evaluates the turbine and diffuser as aerodynamic source forces over the flow, allowing the use of pure hex-core meshes since there is no real geometry. By leveraging actuator lines to model the diffuser and the turbine, our approach can achieve an improved convergence and the required accuracy in its computations at a significantly lower cost. Our research provides a comprehensive evaluation of the Actuator Line Method applied to diffuser-augmented turbines. It analyzes the performance of the S1223 profile for the diffuser, and the Hydro-K rotor, which are extensively studied geometries in the field. The lift and drag input data for these profiles have been obtained through basic panel methodology. Our study assesses the computational efficiency of the adjusted Actuator Line Method and its accuracy in predicting the power coefficient. To validate the methodology, we compare the numerical results of the actuator line method with full-geometry three-dimensional numerical analysis and wind tunnel tests from previous works. Results indicate that employing the Actuator Line Method on diffuser-augmented turbines reduces the computational time to less than 1% when compared to fully resolved geometries. Due to this efficiency, when coupled with the Blade Element Momentum methodology, this model can be used to design turbines along with their diffusers, leading to increased synergy and power output. The methodology accurately predicts the power coefficient at the diffuser-augmented turbine's operational point. However, at high tip-speed ratios, it overestimates the power output due to the Blade Element Momentum formulation's assumptions, which results in an imprecise near-wake description. Our research shows a promising approach for optimizing the diffuser shape for diffuser-augmented turbines, increasing power output and cost-effectiveness. Further studies are required to explore the Actuator Line Method's potential for diffuser-augmented turbines in more complex flow conditions.
Keywords
Actuator Line Methodology, Diffuser-augmented turbine, Computational fluid dynamics (CFD), wind tunnel experiments, Small turbine
