نوع مقاله : مقاله پژوهشی
نویسندگان
1 دانشیار دانشکده مهندسی هوافضا- دانشگاه صنعتی شریف
2 دانشگاه تهران
3 دانشگاه صنعتی شریف، دانشکده مهندسی هوافضا
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Extraction of energy from water flow is among the renewable energy sources that have claimed a significant and growing share of electricity production. The high energy density and long daily operational duration are among the primary advantages of this source. Oscillating foils exhibit a combination of heaving and pitching motions, or a hybrid of both, alongside unsteady aerodynamic phenomena, vortex shedding and propagation, and dynamic stall at high angles of attack. The oscillating foil can operate in two distinct modes: harnessing energy from fluid flow or generating thrust. These modes depend on the flow regime and the kinematic and dynamic variables of the system. Each degree of freedom in the oscillating foil motion can be active, semi-active, or self-induced. If the foil moves by absorbing energy from the flowing fluid, it functions in energy extraction mode; if part of the foil motion energy is transferred to the flow, it operates in thrust generation mode. In the first scenario, a reduction in momentum occurs in the wake of the foil, whereas in the second scenario, an increase in momentum is observed. Additionally, an oscillating foil may operate in a combination of both energy extraction and energy transfer modes within different phases of its oscillation period. In energy-harvesting oscillating foils, the first mode should dominate over the second. In this study, a mechanism for energy harvesting from water flow has been simulated and investigated. This semi-active energy harvester system consists of a flapping hydrofoil that is connected to the generator by an arm. Imposing a prescribed pitch motion on the hydrofoil and generated hydrodynamic forces causes an induced heaving motion. The oscillatory plunging motion of the hydrofoil is transfearred to the generator through the arm. Dynamic modeling of the system, including the generator, hydrofoil, controller and actuator, is provided and the governing dynamic equations are derived. Two dimensional fluid flow simulations of the two-degree of freedom of the hydrofoil have also been conducted. To parametric study of the system, a set of effective and independent parameters of the problem has been identified. The effect of each parameters on the net output power is investigated. These independent parameters include the natural frequency ratio, the damping ratio, the effective angle of attack and the critical arm angle. The corresponding optimal values are 6.5, 0.9, 90 degrees, and 30 degrees, respectively. The output power harvested from the system is 770 watt.
کلیدواژهها [English]
)