Conceptual design and experimental study of a flexible oscillating hydrokinetic turbine

Abstract

Harnessing the energy of deep ocean currents to power deep-sea observation equipment has emerged as a significant focus in recent years. Given the extremely low flow speeds in the deep sea, hydrokinetic turbines need to demonstrate reliable self-starting ability. A novel flexible oscillating hydrokinetic turbine is proposed in the present study to address this challenge. The advantage of the flexible oscillating hydrokinetic turbine lies in the ability to adjust the posture of the flexible blades to create optimal attack angles at different positions. Particle Image Velocimetry measurements are employed to reveal the internal flow field. The results indicate that the incoming flow through the turbine cavity induces two substantial deflections in the inflow and outflow regions, contributing to the generation of significant positive torque. The flexible blades can achieve suitable attack angles at various positions as per the expectations. Especially in the downstream region, the blades adopt a diversion state, thereby avoiding the generation of excessive negative torque. The parametric study was conducted through a water flume and a dynamic testing platform. The results indicate that when the number of blades is six and the installation angle of the blade frame is 20°, the power coefficient of the flexible oscillating hydrokinetic turbine reaches its maximum, exceeding 0.18. A full-process interdisciplinary simulation platform test showed that a flexible oscillating hydrokinetic turbine with a radius of 1 m can self-start in conditions as low as 0.1 m/s. At a flow speed of 0.5 m/s, the turbine can generate over 900 Wh of power per day, enough to power sensors or support an Autonomous Underwater Vehicle’s monthly cruise.