Numerical Investigation of Lucid Spherical Cross-Axis Flow Turbine with Asymmetric Airfoil Sections and the Effect of Different Parameters of Blades on Its Performance

The numerical investigation has been performed on the cross-axis-flow lucid spherical turbine. This type of cross-axis flow turbine generates moments through the forces acting on its blade cross-sections. To evaluate its power and performance, a three-dimensional simulation procedure was performed. The experimental results of Bachant and Wosnik have been used to verify the numerical predictions. The spherical lucid model turbine which they examined had ۴ blades with NACA ۰۰۲۰ section and ۱۶cm chord length. Drag and power coefficients were used to compare the data for the water inlet velocity ۱m/s and different non-dimensional tip-speed-ratio (inlet velocity / linear rotating velocity of the blade). This paper has selected two airfoil sections, NACA ۲۴۱۲ and NACA ۶۴(۳)۴۱۸, to design the turbine blades. The influence of four effective blade parameters, inclusive of profile section type, chord length, number of blades, and blade twist angles, on turbine performance over a wide range of tip speed ratios, is investigated. It can deduce that the power coefficient has increased up to ۲۲% for NACA ۲۴۱۲ compared to the experimental test. Also, the three-bladed turbine possesses the best results among all models. For this model, the power coefficient increased by ۱۲% and ۷۱% for NACA ۲۴۱۲ and NACA ۶۴(۳)۴۱۸ sections, respectively. The twist of the blades increases the power coefficient by ۱۹% and ۳۱% for NACA ۲۴۱۲ and NACA ۶۴(۳)۴۱۸ sections inside the channel respectively. Increasing the blade chord length causes to increase in power coefficient of up to ۱۲% for NACA ۲۴۱۲ section compared to the experimental test.

کلیدواژه ها:

Lucid spherical turbine ، Drag coefficient ، Power coefficient ، Helical turbine ، Asymmetric airfoils