Numerical investigation of performance of a new type of savonius turbine
01 Dec 2012-
TL;DR: In this article, a Savonius turbine of VAWT type has been used to induce fire-whirls in laboratories, and the computational results show that the new design has a higher steady state angular velocity as well as higher coefficient of power than the conventional Savoni turbine.
Abstract: Wind energy is non-polluting and is freely available in many areas and is gaining popularity among researchers. Among wind turbines, Horizontal Axis Wind Turbines (HAWT) are more common compared to Vertical Axis Wind Turbines (VAWT) mainly because of their higher efficiency. However, Savonius turbine of VAWT type has many advantages over others such as simplicity in construction, lower cost of production, constancy of the output power regardless of the wind direction, and good starting torque at low wind speed. It is conceived that the efficiency of the Savonius turbines can be increased using industrial wasted heat primarily due to their structural similarity with the split chambers which are often used to induce fire-whirls in laboratories. This work deals with a basic design of such combined configuration and compares its efficiency with a conventional Savonius turbine. The computational results show that the new design has a higher steady state angular velocity as well as higher coefficient of power than the conventional Savonius turbine.
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02 Apr 2019
TL;DR: In this article, the performance of a SST type single and double stage Savonius rotor with holes at the end plates was investigated and the results showed that double stage turbines showed better performance than single stage turbines.
Abstract: In order to meet the growing demand for energy, wind energy can be one of the suitable options for generation of power Savonius rotor, a type of Vertical axis wind turbine has the ability to accept wind from any direction and it is a low speed turbine This makes it suitable in places where wind speed is relatively low and wind speed varies with season But the main drawback of it is its low power coefficient Thus, there is a need to improve its performance The present study deals with computational investigation of the performance of a SST type single and double stage savonius rotor having holes at end plates For designing and computational investigation, ANSYS-GAMBIT and ANSYS-WORKBENCH 19 software were used for comparison of power coefficient of both the rotors at different tip speed ratio Double stage turbines showed better performance than single stage turbine
2 citations
TL;DR: In this paper , the impact of circular cut-off end plates on the Savonius turbine performance was evaluated through turbine performance data on wind turbine angular speed, electric power, static torque, and efficiency.
Abstract: The Savonius turbine is widely used because it has a simple design. However, the Savonius turbine has a lower efficiency than the Horizontal Axis Wind Turbine (HAWT). Several studies have been conducted to increase the efficiency of the Savonius turbine. Turbine performance can be improved by reducing the negative vortex by creating a flushing effect. This experiment was conducted to determine the impact of circular cut-off end plates on the Savonius turbine. The research results are shown through turbine performance data on wind turbine angular speed, electric power, static torque, and efficiency. The wind turbines with circular cut-off endplates had higher angular velocities than conventional Savonius turbines. The angular velocity measurement is carried out when the turbine is unloading. Meanwhile, the electric power and static torque of a conventional turbine are more significant than a modified turbine. The measurement of electric power and static torque is carried out when the turbine is in a generator-loaded condition (loading).
Dissertation•
01 Jan 2015
TL;DR: In this article, the authors investigated the effect of possible design parameters on specific variables, including the conversion efficiency of thermal energy to kinetic energy, to determine some possible applications of the new, naturally-induced swirl generator.
Abstract: There are many free sources of energy around the globe. By investing in them, the world can reduce its dependence on fossil fuels and improve the quality of the environment. Waste heat is considered a hidden energy source and waste heat recovery creates a green energy source with low cost. In addition, natural thermal energy, such as geothermal and solar energy, is a low-cost sustainable heat source with large amounts emitted and produced annually. The stationary cylindrical split channel (where the cylinder is sliced in half along the axis and the two c-shaped halves are translated laterally), commonly used to induce a fire-whirl in the laboratory, is one device that can utilise these heat sources. This research investigates inducing swirl flow within a stationary cylindrical split channel with two identical slots (without using moving parts) using a hot air flow inlet at its base. The objectives of this research are: Firstly, to examine the generation of swirl flow in the split channel when the used heat source is a hot air flow inlet instead of fire. Secondly, to study the effect of possible design parameters on specific variables, including the conversion efficiency of thermal energy to kinetic energy, to determine some possible applications of the new, naturally-induced swirl generator.
This research was divided into experimental and computational components to accomplish the above objectives. First, a preliminary experiment using a fog machine was conducted to visualise the swirl smoke. This was followed by measurements of the generation of the swirl flow using a two-dimensional Particle Image Velocimetry system (2D PIV system). Olive oil particles were used as seeds and to collect the required measurements of velocity components for subsequent validation of the computational fluid dynamics (CFD) results. The scaling analysis was conducted to present the experimental and computational results in normalized form, and to investigate the scaling effect on the turbulence of the swirl flow. Moreover, thermocouples were used to measure the instantaneous temperatures. Second, the computational study was used to solve the continuity, momentum and energy equations in a steady-state condition, using the ANSYS 13.0-CFX software. The Shear Stress Transport model was used for the turbulence. Thermal radiation and heat transfer to the channel walls were ignored. The channel walls and the base of the domain were assumed to be smooth and non-slippery walls. All sides of the cubic domain, representing the surrounding air (with the exception of the bottom), were assumed to be open with an initial wind speed of zero. The ambient temperature was constant. The pressure boundary condition on the sides and top of the cubic domain was set to atmospheric pressure, which decreases with the height. The thermal properties of air changed with temperature and the transport properties were also functions of temperature, using the Sutherland formulas.
To prove the existence of swirl flow, both fog machine visualization and 2D PIV visualisation and measurements were used. The cylindrical split channel used throughout the experimental investigation had a height of 0.25 m and an internal diameter of 0.095 m. Furthermore, the diameter of the inlet at the base of the split channel was 0.03 m, the width of gap (the translation distance along the split) was 0.0115 m, and the depth of gap (the translation distance normal to the split, creating an overlap) was 0.01 m. The PIV measurements were taken for tangential and radial velocities at three different heights within the channel (33.5 mm, 125 mm and 240 mm), while the axial velocity component was measured for a plane including the centreline of the channel.
A three-dimensional CFD model of the swirl flow produced within the current experimental work was validated by the current PIV measurements. A parametric study was then conducted where design parameters such as the inlet temperature and pressure, all geometric quantities (all the sizes of the channel, holes and gaps) and the number of gaps were varied. The effects of these variations on the normalized centreline axial velocity, normalized centreline temperature, normalized centreline axial vorticity, normalized inlet and exit axial velocities, normalized inlet mass flow rate, entrainment ratio and conversion efficiency of thermal energy at the inlet to kinetic energy along the split channel were investigated. This parametric study was conducted on a cylindrical split channel having dimensions similar to Kuwana’s channel (Kuwana, Morishita, Dobashi, Chuah & Saito, 2011, Proceedings of the Combustion Institute, vol. 33, pp. 2425–2432). In this study, when one parameter was varied, the remainder were maintained constant.
The results from the smoke and PIV visualisation showed that a swirl flow was generated within the cylindrical split channel. The validation of the CFD showed that average relative deviations were 17.7% and 55.3% for the tangential and radial velocities at a height of 32 mm, while it was 49.56% for the axial velocity. The shapes of the profiles for each velocity component were reproduced by the CFD, but the large relative error in the radial velocity is due to its small magnitude, while the error in the axial velocity is due to an inability to predict the large increase and rapid decrease immediately downstream of the inlet. The scaling analysis produced 16 dimensionless groups representing the characteristic of the generated swirl flow. The parametric study for the channel similar to Kuwana’s channel showed that several reported variables affected the conversion efficiency of thermal energy to kinetic energy (
References
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TL;DR: In this paper, a helical Savonius rotor with a twist of 90° was proposed to decrease the variation in static torque from 0° to 360°, and the performance of the helical rotor with and without shaft was compared in an open jet wind tunnel.
258 citations
"Numerical investigation of performa..." refers background in this paper
...In this work, an innovative low cost technique is considered to increases the low efficiency of the conventional Savonius turbines [6,8] using industrial waste heat or natural heat sources....
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Journal Article•
242 citations
"Numerical investigation of performa..." refers methods in this paper
...A vertical axis wind machine proposed by Finnish Engineer Sigurd Savonius [11] is basically a drag type rotor....
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TL;DR: In this article, the authors presented a study, carried out with the help of the French Agency of Innovation (ANVAR), which deals with the conception of a small Savonius rotor (i.e. of low power) for local production of electricity.
237 citations
"Numerical investigation of performa..." refers background in this paper
...In this work, an innovative low cost technique is considered to increases the low efficiency of the conventional Savonius turbines [6,8] using industrial waste heat or natural heat sources....
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...A review of Savonius rotor advantages and disadvantages is presented in Menet [8]....
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...A review of Savonius rotor advantages and disadvantages is presented in Menet [8]....
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TL;DR: In this article, the aerodynamic performance and flow fields of Savonius rotors at various overlap ratios have been investigated by measuring the pressure distributions on the blades and by visualizing the flow fields in and around the rotors with and without rotation.
205 citations
"Numerical investigation of performa..." refers background in this paper
...The optimum overlap ratio (e/d) value has been found as 0.15 by Fujisawa [3], thus the gap distance (e) becomes 2.6 cm and the rotor diameter (D) is calculated as 32 cm. Experiments at an overlap ratio of 0.15 and an aspect ratio (H/D) of 1.0 have been reported to have a maximum power coefficient by Fujisawa and Gotoh [4] and Kamoji et al. [7]....
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...15 by Fujisawa [3], thus the gap distance (e) becomes 2....
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TL;DR: In this paper, the influence of the buckets overlap ratio of a Savonius wind rotor on the averaged moment and power coefficients, over complete cycles of operation, is discussed, based on the commercial software Star-CCM+.
190 citations
"Numerical investigation of performa..." refers background in this paper
...However, it generates power through the combined effect of drags and the lift forces [1]....
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