CFD Analysis of Savonious Rotor Wind Turbines using Ansys PDF

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Proceedings of the 2nd International Conference on Power Generation Systems and Renewable Energy Technologies (PGSRET) June 10-11, 2015, Islamabad, Pakistan CFD analysis of a Savonius Vertical Axis Wind Turbine Asad Muneer1*, Dr.Mohammad Bilal Khan1, Umer Bin Sarwar1, Zia Ahmad Khan1 1. National Uni...

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CFD Analysis of Savonious Rotor Wind Turbines using Ansys Ummee Krispy

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Proceedings of the 2nd International Conference on Power Generation Systems and Renewable Energy Technologies (PGSRET) June 10-11, 2015, Islamabad, Pakistan

CFD analysis of a Savonius Vertical Axis Wind Turbine Asad Muneer1*, Dr.Mohammad Bilal Khan1, Umer Bin Sarwar1, Zia Ahmad Khan1 1. National University of Sciences and Technology (NUST), Center for Advanced Studies in Energy (CAS-EN), Sector H-12, Islamabad, Pakistan *Corresponding Author’s Email: [email protected]

Abstract—Pakistan is among of the developing countries in the world that are facing energy crisis. The generation of electricity in Pakistan is shrinking due to an over reliance on fossil fuel resources and also due to the increasing demands for power and lack of efficiency. Due to this energy crisis, many countries have started the research and working in the renewable energy field. In the fields of renewable energy, wind energy is very attractive and has a very key role in the sustainable energy. The purpose of this research work is to analyze a Savonius Vertical axis wind turbine for low wind speed that is inexpensive and is made through easily available material to provide much needed electricity in Pakistan. This paper highlights the designing of the wind turbine and the effect on the blades. With the help of calculating values, 3D view of wind blades’ shape has been drawn in the Solid works software. With the help of the Solid works generated file, optimization of the behavior of wind above and below the turbine blades have been analyzed.

convert the solar energy to wind energy [2]. With this estimate the maximum global wind resource is approximately 1.22 x 1015 kWh/ year. The following figure shows the wind energy potential in global region.

Figure 1: wind energy potential in global region

Keywords—CFD; Ansys; Wind turbine

I. INTRODUCTION Wind energy is basically the derivation from solar energy through a thermodynamic process in which ground is heated by the sun, which results in an increased in temperature of the air above the ground[1]. The warm air rises up resulting in a pressure difference which causes cold air to rush in and to replace the hot air. As a result of this air motion wind is generated. Earth’s rotation affects the air motion as well. Also the different parts of the world are heated differently, which is essentially the function of latitude. So, due to the earth’s rotation and uneven heating of different regions wind speed is different in different regions. Assuming a solar constant of 1367 W/m2, the total energy present at the outer atmosphere is 1.53 x 1018 kWh/ year. About 2% of efficiency is required to

The Figure 1 shows that the darker the color of the region, wind speed will be higher and vice versa. The basic two types of wind turbines are Horizontal Axis Wind turbine and Vertical Axis Wind turbine, but this paper relates to the Vertical Axis Wind turbine in which main rotor shaft is positioned in such a way that it is perpendicular to the wind blades[2]. These turbines are used in such areas where wind direction is highly variable. In vertical axis wind turbines, the position of the generator and the gearbox is on the ground and are easily accessible for maintenance purposes. In Savonius vertical axis wind turbine, blades are arranged in such a shape that it appears an S-shaped type if viewed from above. Savonius turbine is a drag type device contains two or more scoops. If there are three scoops, savonius turbine always has a starting torque. The torque generation in vertical turbine is because of the drag force acting on the vertical cylinders[3].

Proceedings of the 2nd International Conference on Power Generation Systems and Renewable Energy Technologies (PGSRET) June 10-11, 2015, Islamabad, Pakistan

II. METHODOLGY The aim of this research was to analyze the savonius wind turbine by using different designing parameters.

this technique is being used widely and it has great significance for studying turbo machinery. This technique has a wide range of engineering applications[1]. CFD analysis was done with the help of a fluent software package. Open the Fluent, the first step was to import the geometry of blades from AutoCAD and generating it. Now read the mesh fluent file of the geometry for analyzing the fluent. This was done by choosing the mesh fluent file from the given list. The mesh now checks for errors and to understand the geometry[4]. When the mesh is loaded, the units of the grid are now checked to check the integrity of the meshing fluent. Now scaled the grid. In this case, the (SI) system was used.

Figure 2: Sketch of the Savonius Wind Turbine

Figure 2 shows the sketch of the savonius wind turbine in which ω is the angular speed, R is the radius of the wind blade. By using the different values of designing parameters regarding blade designing of the wind turbine, we can draw the solid model of wind blades. For this purpose, 3D view of wind blades’ shape has been drawn on the AutoCAD with calculated values. Figure 4: Import Geometry on ANSYS

Figure 4 shows the Imported Geometry from AutoCAD. Here we extruded the AutoCAD geometry in c rectangular box for the purpose of wind direction.i.e.inlet, outlet. After defining the mesh and unit systems for the problem, the next step was to define the models that were to be used for the simulation. First, the solver model was chosen[5].

Figure 3: Geometry of Blades on AutoCAD

Figure 3 shows the geometry of the savonius wind turbine blades drawn on AutoCAD by using different dimensions.

III. COMPUTATIONAL FLUID DYNAMICS SIMULATION Computational Fluid Dynamics, with the help of computers is used to indicate the numerical solution of the differential governing equations of fluid flows. In aerodynamics research,

In Fluent, the solver model can be chosen to be either pressure based or density based. The density model is typically used only for problems involving compressible flow, while the pressure based model is used for the majority of simulations. Since one of the assumptions for this problem was that the density of air was constant throughout the geometry, the pressure based model was selected.

Proceedings of the 2nd International Conference on Power Generation Systems and Renewable Energy Technologies (PGSRET) June 10-11, 2015, Islamabad, Pakistan

Figure 5: Meshing Geometry on ANSYS Figure 7: Iterations

Figure 6: Meshing in solvent Figure 8: Velocity Vectors

Figure 5 shows the meshing geometry on Ansys fluent and Figure 6 shows the meshing in solvent. Within the solver based model it was also necessary to define how the model varies with time; in other words whether it is steady or unsteady. For the first series of simulations, the steady state model was selected. After defining the models that were to be implemented in running the simulations, the next step was to define the material properties that would be used. The default material was air with standard properties at room temperature. These default properties were retained[6]. At this time, it was necessary to define the boundary conditions to serve as a basis for the computations that would be used to analyze the problem. After the necessary iterations were performed, it was possible to analyze the results. First, several planes were taken at various cuts over the meshed geometry. Contours and vector plots were then drawn over the cutting planes to get an idea of the physical properties over different locations within the geometry, most notably the velocity fields, pressure distribution[3].

Figure 9: Pressure Contours

IV. RESULTS AND DISCUSSIONS Figure 7 shows the no.of iterations done for solvent in fluent. Almost 50 iterations have been selected here for the convergence criteria but solution is converged at 30th iterations. When the solution is converged, then we can check the behavior of wind across the blades. Figure 8 shows the velocity vectors across the blades as we selected the wind speed as 3.5 m/sec[2]. Figure 8 of velocity vectors shows that the velocity on the blades is 3.5 m/sec because

Proceedings of the 2nd International Conference on Power Generation Systems and Renewable Energy Technologies (PGSRET) June 10-11, 2015, Islamabad, Pakistan

the velocity vectors going to be change from -3.34 e-02 light greenish to +3.34 e-02 yellow color.This means that pressure around the blades should be greater than the pressure above and below it and it can be seen from the Figure 9 where the pressure across the blades is lower and is -1.98 e-03 .

V. CONCLUSIONS The Savonius vertical axis wind turbine is ideally located at the top of the bridges. By using the designing parameters, fabrication of the blades and its demonstration can be easily analyzed. In Vertical axis wind turbine, these are the problems associated with the configuration, i.e. Self-starting and low initial torque and low coefficient of power[6]. With the help of CFD, configurations of a single wind blade or multiple blades can be visualized. The turbine drag coefficient increases with the increase in turbine area and decreases with the decrease in turbine area. The results give good agreement when compared with experimental published results. By using the ANSYS software, we can check the behavior of wind flow across the wind blades. VI. REFERENCES [1]

[2]

[3] [4]

[5]

[6]

M. M. Aslam Bhutta, N. Hayat, A. U. Farooq, Z. Ali, S. R. Jamil, and Z. Hussain, “Vertical axis wind turbine – A review of various configurations and design techniques,” Renewable and Sustainable Energy Reviews, vol. 16, no. 4, pp. 1926–1939, May 2012. M. S. Hameed and S. K. Afaq, “Design and analysis of a straight bladed vertical axis wind turbine blade using analytical and numerical techniques,” Ocean Engineering, vol. 57, pp. 248–255, Jan. 2013. T. Submitted, S. Id, W. Count, and C. Count, “Asad,” 2014. K. Suffer and R. Usubamatov, “Modeling and Numerical Simulation of a Vertical Axis Wind Turbine Having Cavity Vanes,” vol. m, 2014. M. H. Ali, “Experimental Comparison Study for Savonius Wind Turbine of Two & Three Blades At Low Wind Speed,” vol. 3, no. figure 1, pp. 2978–2986, 2013. J. Mccosker, “Design and Optimization of a Small Wind Turbine by,” no. December, 2012....