Wind Impact Stress Evaluation of Rectangular Geometric Blades of Wind Turbine for Maximum Power Development in Nigeria

Mechanical Engineering

The study, wind impact stress evaluation of rectangular geometric blades of wind turbine for maximum power development in Nigeria, was successfully achieved. Researchers created geometrical wind turbine rectangular blade models with rotor using Autodesk inventor. Rectangular blades retained dimensions of 30mm by 6mm with thickness of 5mm. The rotor hub and shaft diameters were 60mm and 35mm with rotor height of 50mm respectively and shaft length of 80mm. A fillet radius of 2mm was adopted to de-concentrate stress acting at the hub and shaft rims. . Maximum average wind speed was used to compute wind site pressure and wind site load acting on each blade and was found to be 0.030N. Finite element simulation was run with rectangular blade geometry, using wind site load and turning moment of 6 N mm. Results showed that the Von Mises stress was found to be 0.211202 MPa. Since, yield strength of the assigned material is 250 MPa; it suggested that failure of rectangular blade due to wind yielding load is not possible under the given conditions. In addition, the 1st and 3rd principal stresses were found to be 0.153905 MPa and 0.029736 MPa respectively. These results indicated that the rectangular blade would fail due to tensile stress on wind impact rather than compressive stress; these results, further suggested that to improve reliability and stability of operation, excessive attack of wind/impact on rectangular blades along horizontal axis must be avoided, since stress was much along the horizontal axis. Stress concentration was found to be much at the, bonded heads and tails of blades, as well as rotor circumference. Also, the maximum displacement/deformation of rectangular blades due to wind impact load of 0.03N was found to be 0.0000547862 mm. This suggested that the rectangular blade geometry used showed lower deformation response and could improve service life of wind turbines. It was also found that the maximum induced stress was 0.0452271 MPa where as the ultimate tensile strength of material used for the rectangular blade was 540 MPa. This suggested that the rotor and blade designs were safe and not over stressed. Keywords ---- Impact stress, Wind, Rectangular geometry, Wind turbine, Wind load

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