ANALYSIS OF THE MECHANICAL BEHAVIOR OF A COMPOSITE BLADE USED IN HYDROKINETIC TURBINES
Guilherme Vaz Ferreira1; Flaminio Levy Neto1; Miélle Silva Pestana1
1 Universidade de Brasília
doi:10.20906/CPS/COB-2015-0385
Resumo
The projections related to the world global demand of electricity show a very high growth in consumption in the coming decades. It has been show that this consumption will increase by 93 % in 2040, compared to the one in 2010. Currently, more than 60 % of the energy consumed comes from fossil fuels, which are limited resources and highly harmful to the environment as well as to human beings. In this context, the use of hydrokinetic turbines operating with the flow of the rivers is an excellent choice, as they have better predictability, relatively to wind turbines, and higher power density. The main objective of this work is the design and stress analysis of a composite blade to be used in a horizontal axis hydrokinetic turbine, which can generate up to 500 kW of electricity, with Tucurui's river flow, in Pará state. This turbine has a rotor with three blades and a nominal diameter of about 10 meters. Two types blades, subjected to the same load, were analyzed: (i) the first one manufactured with carbon/epoxy unidirectional reinforced prepreg laminas type AS4/3501-6; and (ii) the second one made with 6061-T6 aluminum alloy. The blades have the same external geometry, and are composed by two skins, one cylindrical spar and stringers. Results were obtained using ANSYS, reputed finite element analysis (FEA) software. Masters nodes and restrained equations were used to apply the hydrodynamic loading. The maximum failure index established for the composite and metallic blades were respectively 0.5, according to Tsai-Wu failure theory, and 0.5 according to von Mises yield criterion. The masses obtained for the composite and metallic blades were 221.87 kg and 709.16 kg, respectively. The maximun deflection at the blade tip were 5.65 cm for the composite blade and 2.45 cm to the metallic blade. Thus, the results obtained so far indicate that the carbon/epoxy blades can be significantly lighter but aluminum ones more rigid.
Palavras-chave: Hydrokinetic turbine blade; composite; finite element method; structural analysis