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ABSTRACT In order to make clear the hysteresis behavior of biplane Wells turbine performance in deep stall condition, numerical investigations were made for the hysteretic characteristics in deep stall condition of biplane Wells Turbine. The numerical investigation was made by an unsteady three-dimensional Navier-Stokes numerical simulation. The calculated turbine unsteady performance show two characteristic loops. A counterclockwise hysteresis loop is observed in the unstalled condition and a clockwise hysteresis loop is observed in the deep stall condition. By dividing the torque and total pressure drop coefficient values between the one for upstream blade and the one for downstream one, it is found that the clockwise hysteresis loop can be seen only for the downstream blade. INTRODUCTION In the past two decades, worldwide efforts have been devoted to the development of energy conversion from ocean waves. One of the most applicable devices for wave energy is the combination of an Oscillating Water Column (OWC) as a primary converter and a self-rectifying air turbine as a secondary one (Fig.1). The Wells turbine is one of the most suitable air turbines for energy conversion from oscillating air flow. A lot of researches have been made for the Wells turbine and it has been found that the Wells turbine has hysteretic characteristics in an unsteady flow in unstalled condition (Inoue et al. (1987), Setoguchi et al. (1990) and Alcorn&Beattie (1998). These hysteretic characteristics should be clarified for the better design of the system for wave power conversion. Dynamic stall of an airfoil is well known as an unsteady aerodynamic phenomenon which has hysteretic characteristics, and a lot of researchers have reported many kinds of aspects of dynamic stall of an airfoil (Ericsson&Reding (1987), Shida et al. (1987), Carr (1988) and Leishman (1990)).
- Energy > Renewable > Ocean Energy (0.90)
- Transportation > Air (0.88)
- Health, Safety, Environment & Sustainability > Sustainability/Social Responsibility > Sustainable development (0.55)
- Health, Safety, Environment & Sustainability > Environment (0.55)
- Reservoir Description and Dynamics > Reservoir Simulation (0.49)
- Data Science & Engineering Analytics > Information Management and Systems (0.35)
ABSTRACT One of the main reasons for the wave energy generation not yet gaining popularity as a renewable energy source is the lack of work relevant to the design of a stand-alone wave energy power plant. The major issue in the design of such a plant feeding variable AC load and maintaining a regulated voltage and frequency at the output, concerns the control of the plant itself. In this work, an impulse turbine is used to convert differential air pressure due to oscillating water column into mechanical shaft power. A permanent magnet based alternator driven by this turbine generates variable voltage variable frequency AC, which is rectified to DC by a diode bridge. At the second stage, DC motor - alternator set converts this into fixed frequency, fixed voltage AC acceptable as a utility AC supply. Results obtained from a steady-state model simulated using MATLAB -Simulink are presented. Actual data recorded by the Indian wave energy plant have been used to validate the results. INTRODUCTION Due to increasing gap between the electrical energy generation and demand and due to the growing concern for avoiding pollution, renewable energy sources are becoming indispensable. The focus in this paper is on ocean wave energy conversion scheme. The average wave potential along Indian coast is around 5 to 10 kW per meter length of the wave crest (Ravindran. M, Jayashankar.V, Jalihal.P and Pathak.A.G, 1997). The Indian wave energy plant is situated near Vizhinjam in the state of Kerala and it is based on the OWC device. The construction of the caisson, i.e., the wave capturing chamber, is the basic factor which decides the amount of the pneumatic energy that can be extracted from the waves. Larger the dimensions of the caisson, larger will be the amount of the pneumatic energy extracted from the waves.