Simulating variable pitch crossflow water turbines: A coupled unsteady ONERA-EDLIN model and streamtube model

• Published in: Renewable energy Vol. 52; pp. 209 - 217
• Main Authors: Paillard, B., Hauville, F., Astolfi, J.A.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.04.2013; Elsevier; ELSEVIER
• Subjects: Applied sciences; Blades; Computer simulation; Darrieus; Dynamic stall; Dynamics; Energy; Engineering Sciences; Exact sciences and technology; Fluid flow; Fluids mechanics; Mathematical models; Mechanics; Momentum theory; Natural energy; Stall; Structural mechanics; Turbines; Unsteady; Variable pitch; Momentum theory; Darrieus; Dynamic stall; Variable pitch; Renewable energy; Stall; Crossflow; Models; Modeling
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2012.10.018

This article describes a new method for simulating unsteady hydrodynamics forces and moments on the blades of a crossflow ‘Darrieus’ turbine with active pitch variation. This method is based on the ONERA-EDLIN dynamic stall model, coupled with a momentum streamtube model to take into account the turbine interference on the flow. Both models are presented, and compared separately with experimental results for a pitching airfoil for the ONERA-EDLIN model; and for Darrieus turbine for the momentum theory. The model coupling is then detailed and compared with experimental data taken from the open literature [1] The turbine has 2 straight blades with a NACA 0012 section operating in water at a mean chord Reynolds number of 4 × 104 for tip speed ratio λ = 2.5, 5 and 7.5. Good agreement was found for average λ = 5, and qualitative agreement could be obtained at low and high λ, where dynamic stall effects and interference effects respectively are predominant. This is positive because λ = 5 is the closest value from the optimal power production point. Variable pitch is finally introduced in the model and several functions are tested in order to increase efficiency. A maximum increase of 53% on the power coefficient was found to occur with a sinusoidal law. ► Hybrid model for unsteady force and performance prediction on a crossflow Darrieus turbine. ► Based on the ONERA-EDLIN dynamic stall model, and a momentum « streamtube theory ». ► Pitch variation which results in power increase at very low or zero extra energy cost.