ScholarWorks@경상국립대학교

초록

The present study aimed to reveal the operation and flow characteristics of horizontally oriented hybrid hydrokinetic turbine rotors composed of Bach and H rotors. The computational fluid dynamics (CFD) technique was used in conjunction with the six degrees of freedom (SDOF) method to solve instantaneous flow field. The results indicate that at a tip speed ratio of 1.73, the highest power coefficient of 0.328 is obtained with the H(B) rotor, characterized by a Bach rotor encircled by the blades of an H rotor. For the H-B rotor, characterized by a Bach rotor arranged side by side with an H rotor, and the B-H-B rotor, which consists of Bach and H rotors arranged in series, their startup performance is similar, and their torque coefficients are about twice larger than that of the H (B) rotor. The rotational speed during the stable operation stage increases monotonically with the upstream flow velocity. The H(B) rotor features a shortest startup time of approximately 1.23 s at an upstream velocity of 2.8 m/ s. A compound wake is evidenced by the H-B and B-H-B rotors; the part of the wake corresponding to the Bach rotor inclines downward, whereas the wake of the H rotor meanders in the streamwise direction. In comparison, the wake of the H(B) rotor involves a relatively high velocity deficit.

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