Computational Fluid Dynamics Based Optimal Design of Vertical Axis Marine Current Turbines
Abstract Marine turbines are being increasingly used to harness kinetic energy of water and convert it into other useful forms of energy. Widespread commercial acceptability of these machines depends upon their efficiency. This largely depends upon the geometric features of the marine turbines such as number of blades, shape of blades etc. Researchers have been using experimental facilities to optimise these machines for maximum power generation. With the advent of advanced computational techniques, it has now become possible to numerically simulate the flow of water in the vicinity of marine turbines and monitor their performance output. In this work Computational Fluid Dynamics (CFD) based techniques have been used to analyse the effects of number of blades within the stator and rotor, of an in-house built Vertical Axis Marine Current Turbine (VAMCT), on the performance output of the turbine. Furthermore, an effort has been put forward towards better understanding of the flow structure in the vicinity of the blades during transient interaction between rotor and stator blades. This study provides vital information with regards to the flow sensors’ requirements and placements in order to monitor various blade configurations of a VAMCT in real world. The results of this study show that the torque output from a VAMCT is a strong function of blade configurations and there is a significant degradation in the performance output of marine turbines as the inequality between the number of rotor and stator blades increases. Hence, CFD has the potential to optimise the design of marine turbines and can be used as a potential modelling tool in the near future for on-line health monitoring of such systems.
Review of Various Designs and Development in Hydropower Turbines
— The growth of population, rising fossil fuel prices (limited and decreasing day by day), pollution problem due to use of fossil fuels and increasing electrical demand are important factors that encourage the use of green and renewable energy technologies. Among the different renewable energy technologies, hydro power generation (large and small scale) is the prime choice in terms of contribution to the world's electricity generation by using water current turbines. Currently, researchers mainly focused on design and development of different kind of turbines to capture hydropower to generate electricity as clean and reliable energy. This paper is a review of the status of research on water current turbines carried out to generate electricity from hydrokinetic energy especially in places where there is no electricity, but there is access to flowing water.
CFD Simulation and Experimental Validation of a Vertical Axis Turbine: Toward Variable Pitch Cross-Flow Marine Turbine for Maximizing Hydropower Extraction—The SHIVA Project
The paper describes the numerical simulation of a cross-flow axis water turbine, widely known as Darrieus turbine or VAWT. The numerical solver is the RANSE solver CFX. The method of resolution aims at calculating the instantaneous forces on the blades of such a turbine, and the energy produced. Due to the specific blade kinematics that can result of pitch variable systems and the complex flow particularly in the centre part of the turbine, a meshing strategy based on the mixing of both sliding or/and deforming mesh were used. Due to the moderate Reynolds number involved in such systems, various fluid models were used including laminar flow, fully turbulent model as k–ω SST model and a laminar-turbulent transition model. A convergence study was carried out for time step, which yielded to courant number lower than 5 and angular step below 1 ° with about 600.000 cells with y+ = 1 . Fixed pitch devices were simulated for comparison with experiments data available in the literature to validate the numerical model. The normal and tangential forces were compared for various flow conditions. The number of blades ranged from 1 to 3 , the Tip Speed Ratio ranged from 1.5 to 7.5 , the Reynolds number was about 4 ×10 4 . It was observed that the agreement between the experiments and the numerical results is very good with the turbulent model in all cases excepted for one low TSR case for which the blade section incidence is maximum. Next step will consist in running simulations with variable pitch.© 2011 ASME