<p>In this research, an experimental investigation is carried out on a Savonius-resembling hybrid water turbine with unsymmetrical NACA 63415 aerofoil curvature segment and straight blade segment with the design features—aspect ratio, curved edge gap, blade side gap, and overlapping ratio. Various hydrodynamic performance metrics are examined for low stream-speeds (0.6–1&#xa0;m/s) generally observed in perennial rivers under different turbine load conditions. Taguchi design of experiments are performed for finding optimal combinations of design features, and optimized performance is also verified. Further, to analyse and corroborate the hydrodynamic performances, CFD analysis is performed to decipher flow structure around the blades, considering the same optimal design combinations. Results show that by increasing the blade side gap and overlapping while keeping the curve edge gap constant, the hydrodynamic performance can be enhanced. With optimal blade side gap 6.14%, overlapping ratio 20%, and aspect ratio 0.26, the turbine exhibited a maximum coefficient of performance (<i>Cp</i>) and torque coefficient (<i>T</i><sub><i>coeff</i></sub>) of 0.256 and 0.445, respectively, for a low stream-speed 0.8&#xa0;m/s. At the optimal blade side gap 6.14%, flow structure is well-developed contributed by the curve edge gap and overlapping flow in the straight blade portion. Additionally, high-intensity shear layers at the leading and trailing edges of the advancing and returning blades and reduced vortical region around the blades resulted in more thrust and higher performance of this design.</p>

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Experimental and fluid-flow structure analysis of a Savonius-resembling hybrid water turbine at low stream-speeds

  • Biswajit Nath,
  • Agnimitra Biswas,
  • Biplab Das,
  • Rahul Dev Misra

摘要

In this research, an experimental investigation is carried out on a Savonius-resembling hybrid water turbine with unsymmetrical NACA 63415 aerofoil curvature segment and straight blade segment with the design features—aspect ratio, curved edge gap, blade side gap, and overlapping ratio. Various hydrodynamic performance metrics are examined for low stream-speeds (0.6–1 m/s) generally observed in perennial rivers under different turbine load conditions. Taguchi design of experiments are performed for finding optimal combinations of design features, and optimized performance is also verified. Further, to analyse and corroborate the hydrodynamic performances, CFD analysis is performed to decipher flow structure around the blades, considering the same optimal design combinations. Results show that by increasing the blade side gap and overlapping while keeping the curve edge gap constant, the hydrodynamic performance can be enhanced. With optimal blade side gap 6.14%, overlapping ratio 20%, and aspect ratio 0.26, the turbine exhibited a maximum coefficient of performance (Cp) and torque coefficient (Tcoeff) of 0.256 and 0.445, respectively, for a low stream-speed 0.8 m/s. At the optimal blade side gap 6.14%, flow structure is well-developed contributed by the curve edge gap and overlapping flow in the straight blade portion. Additionally, high-intensity shear layers at the leading and trailing edges of the advancing and returning blades and reduced vortical region around the blades resulted in more thrust and higher performance of this design.