1,720,965 research outputs found
Performance Study of Helical Darrieus Rotor
No full textNowadays, electrical power is crucial for all human activities. Several methods are available to produce the electrical energy. Small-scale hydropower is designated as a clean and renewable energy resource that maintain the biodiversity of natural environment. Hydrokinetic rotors are broadly classified based on the rotation axis into two major categories, horizontal axis hydrokinetic rotors and vertical axis hydrokinetic rotors. Although horizontal axis hydrokinetic rotors remain to be commercially appropriate for large-scale hydropower generation, vertical axis hydrokinetic rotors work at low water velocity and are suitable for small-scale hydropower production. Among the vertical axis water turbines, the Darrieus rotors make use for a specific implementation because they are economic and independent to the water direction. Therefore, many investigations have been realized to boost its efficiency. In this work, experimental tests realized in an irrigation canal were performed with a 3D printed Darrieus rotor. With the intention of the performance betterment of the studied rotor, a novel blade shape namely V-shaped blade was tested numerically using the commercial software ANSYS FLUENT 17.0. The maximum value of the power coefficient of the Darrieus rotor reaches 0.17 using twisted blades. However, using V-shaped blades, the highest value of the power coefficient gets at 0.185
Performance improvement of a novel combined water turbine
No full textNowadays, industrials and researchers are looking for renewable energy resources due to the increase of energy demand. Recently, the ability of combined turbines in harnessing energy from water current has increased their renewed interest. However, there still exist a big knowledge gap to select the optimal design of these turbines. In this paper, systematic studies of stand-alone helical Savonius and delta bladed Darrieus turbines were carried out using experimental methods as a precursor to analyze their roles in hybrid configuration. By varying the attachment angle, two hybrid configurations were tested experimentally. Using the optimal attachment angle, six hybrid configurations were investigated numerically based on the commercial software ANSYS FLUENT 17.0. From one configuration to another, only the design of the Savonius turbine was changed. The maximum power coefficient is found to be equal to 0.191 at tip-speed ratio of 0.63 using a helical bladed Savonius turbine with twist angle of 90°. However, the maximum power coefficient reaches 0.232 using a delta bladed Savonius turbine with the same twist angle. This optimization of the novel combined water turbine could be a solution to enhance the generated power
Performance Study of a Lucid Spherical Rotor
No full textNowadays, world population is growing very rapidly and need for electricity is rising. Due to adverse influence of non-renewable fuels exploitation on public health, global electricity need for renewable energies is predicted to rise. Hydraulic energy has got a growing interest as one of the clean and renewable energies. Cross flow turbines are more preferred in small-scale hydropower generations. Due to rising cost incurred in experimental studies of the design process of cross flow turbines, researchers have adopted numerical methods mainly CFD (Computational Fluid Dynamics) technique. In fact, the CFD method allows to find out the hydrodynamic specifics as well as the fluid stream behavior near a water rotor as that are hardly evaluated based on experimental tests. Within this study, one of the most used CFD package, the Ansys Fluent 17.0 has been employed to resolve the transient incompressible Reynolds-averaged Navier-Stokes equations and to analyze the impact of the dimension of the rotating domain on the numerical study of a Lucid water rotor. The validation of the numerical model with previous investigations has been fulfilled to choose the adequate rotating domain size. The hydrodynamic specifics of the flow near a Lucid spherical rotor (LSR) have been analyzed and discussed
Investigation of a helical Savonius turbine with a deflector system
No full textThe growing demand for renewable energy sources to meet electricity needs has underscored the importance of exploring new resources of renewable energy. Among the various alternatives, Helical Savonius rotors have emerged as one of the most widely used technologies for small-scale hydropower generation. Numerous studies have been conducted to investigate these types of rotors, particularly to enhance their power output. Despite existing research, there is still a need for modifications and proposals for new configurations of Savonius rotors. This paper presents a numerical study of a Savonius rotor equipped with a new design of a deflector. The results indicate that the highest power coefficient achieved is 0.1247 at a tip-speed ratio of 0.7 in the absence of a deflector system. The geometric parameters of the deflector are varied to identify the configuration that generates the highest power output. With the implementation of an optimal configuration for the new deflector system, the maximum power coefficient is improved to 0.168 at a tip-speed ratio of 0.7. Otherwise, the maximum power coefficient could be enhanced by 34% compared to the same configuration without a deflector. This significant improvement highlights the potential of the proposed design system
Numerical Model Parameters Impact on Savonius Wind Rotor Performance
Full text linkGlobal greenhouse gas emissions are mostly caused by the production of energy extracted from fossil fuels sources. Indeed, the use of renewable clean energy has become crucial to supply the world demand while protecting the planet. For many years, there has been a great deal of interest in wind energy because it is a clean, sustainable energy source. Because of its cheaper cost and independence from wind direction, the Savonius vertical axis wind rotor has the advantage of being suitable for certain implementations as an energy converter. Several studies have been carried out to increase its efficiency from this angle. This research work emphasizes on the Savonius wind rotor numerical model performances. The main goal is to explore the impact of setting the numerical model parameters on its aerodynamic and performance characteristics. Ansys Fluent software 17.0 was utilized to perform numerical simulations utilizing the unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. The mesh sizing, the turbulence model as well as the time step parameters were investigated. The numerical model validation was realized through published experimental findings available in the literature for an inlet wind velocity of 6 ms-1. Good accordance was obtained. Thus the numerical model with the selected parameters was relevant for further investigations. For a tip speed ratio λ=0.64 it gave a torque and power coefficients equal to 0.328 and 0.2, respectively
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Experimental and numerical investigation of Zephyr-type wind turbine
No full textThe search for more environmentally friendly energy sources has been prompted by growing environmental concerns. In this regard, wind energy can be an alternative viable source of energy for world electricity demand supply. Despite of their benefits in terms of simplicity of manufacture, independency on wind direction and good starting ability in turbulent flow, Savonius wind turbines as a vertical axis wind energy converter are not recommended for large-scale power generation because of their poor performances. This research emphasizes on the performance improvement of a Zephyr wind rotor (ZWR). Experimental tests were conducted in a wind tunnel for different Reynolds numbers. Maximum power coefficient of 0.074 was recorded for Re = 158,000 corresponding to V∞ = 10 m s−1 at a tip speed ratio of λ = 0.99. Numerical study was carried out with the use of Ansys Fluent 17.0 software through transient 3D simulations investigating the optimization of the ZWR rotor blades and stator vanes with the aim of performance betterment. Maximum power coefficient of 0.168 was found with 8-bladed ZWR with 12 stator vanes. Aerodynamic properties were also improved
Performance Improvement of a Drag Hydrokinetic Turbine
Full text linkHydropower is at present in many locations, among all the other possible renewable energy sources, the best one for net cost per unit power. In contrast to traditional installation, based on water storage in artificial basins, free flow river turbines also provide a very low environmental impact due to their negligible effect on solid transport. Among them, kinetic turbines with vertical axis are very inexpensive and have almost zero impact on fish and local fauna. In application to tidal waves and sea waves, where vertically averaged velocities have alternate direction, a Savonius rotor also has the advantage of being productive during the whole time cycle. In this work, the effect of an upstream deflector system mounted upstream of a twisted Savonius rotor inside a channel has been investigated through numerical simulations and experimental tests. Numerical simulations were carried on using the ANSYS FLUENT 17.0 software. Based on this numerical study, it is shown that the proposed deflector system has improved the power coefficient of the Savonius rotor by 14%. The utilization of this new design system is predicted to contribute towards a more efficient use of flows in rivers and channels for electricity production in rural areas
Effect of the Turbulence Model on the Computational Results of a Lucid Spherical Rotor
Full text linkDue to the excessive increase in the energy demand, renewable energy has become an alternative for electricity production for industrial and domestic needs. Water energy has received significant investment as a sustainable and clean energy source. Lucid spherical rotors, a kind of hydro-power converter, are cross flow rotors designed to be mounted within a pipeline in order to gather excess energy available in gravity-fed water pipelines. This paper focuses on the effect of the numerical model parameters choice, namely the turbulence model, on the Lucid spherical rotor hydrodynamic characteristics. Numerical simulations were carried out through Ansys Fluent software 17.0 using the unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. Four turbulence models: RNG k-ε, Realizable k-ε, SST k-ω and transition SST were tested. Performance characteristics in terms of torque and power coefficients in addition to hydrodynamic features of the flow around the considered rotor were analyzed. The adopted numerical model was validated based on previous experimental findings from the literature. It was found that the realizable k-ε model showed a good agreement with experimental results. Thus, it was adopted for the Lucid spherical rotor simulation. The obtained findings could provide further direction for researchers to use the Lucid spherical water turbine
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