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Department of Mechanical Engineering Full time academic staff = 43 members

AERODYNAMIC MODELING OF WIND TURBINE BLADES AND LINEAR APPROXIMATIONS M. Mirhosseini , A. Sedaghat , and A.A . Alemrajabi Speaker: Dr Ahmad Sedaghat Department of Mechanical Engineering Isfahan University of Technology (IUT). Department of Mechanical Engineering

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Department of Mechanical Engineering Full time academic staff = 43 members

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  1. AERODYNAMIC MODELING OF WIND TURBINE BLADES AND LINEAR APPROXIMATIONSM. Mirhosseini , A. Sedaghat, and A.A. AlemrajabiSpeaker: Dr Ahmad SedaghatDepartment of Mechanical EngineeringIsfahan University of Technology (IUT)

  2. Department of Mechanical Engineering • Full time academic staff = 43 members • Technical staff = 18 members • Undergraduate students = 728 students • Postgraduate students = 230 MSc & 96 PhD students • Courses in Renewable Energies: Solar Energy, Wind Energy, Fuel Cells, Energy Conversion and Energy Managements, Tidal and Wave Energy • Facilities in wind energy: Wind tunnel 90 cmX90 cm, Water Channel 100 m, and wind anomometers

  3. Research in Renewable Energy at IUT • Feasibility studies in wind energy potentials in Iran (The potential energy of wind is estimated to be about 6500MW in Iran) • Design and manufacturing small innovative wind turbines: a three bladed helical vertical axis wind and water turbine, a two bladed horizontal axis magneous type turbine • Design and manufacturing water current turbines: Gorlov or DNA type, and VGOT type • Open jet wind tunnel testing • Nano-layers and Nano-fluids in Solar Energy applications • Hybrid power systems and fuel cells

  4. Orientation Turbines can be categorized into two overarching classes based on the orientation of the rotor Vertical Axis Horizontal Axis

  5. Calculation of Wind Power Power in the Wind = ½ρCpAV3 • Power in the wind • Effect of swept area, A • Effect of wind speed, V • Effect of air density,  • Power coefficient, Cp Swept Area: A = πR2 Area of the circle swept by the rotor (m2).

  6. ΩR V λ= Tip-Speed Ratio ΩR R Tip-speed ratio is the ratio of the speed of the rotating blade tip to the speed of the free stream wind. There is an optimum angle of attack which creates the highest lift to drag ratio. Because angle of attack is dependant on wind speed, there is an optimum tip-speed ratio Where, Ω = rotational speed in radians /sec R = Rotor Radius V = Wind “Free Stream” Velocity

  7. Performance Over Range of Tip Speed Ratios • Power Coefficient Varies with Tip Speed Ratio • Characterized by Cp vs Tip Speed Ratio Curve

  8. Maximum power coefficient Cp B: Number of blades Cl: Lift coefficient Cd: Drag coefficient λ: Tip speed ratio

  9. Airfoil Shape Just like the wings of an airplane, wind turbine blades use the airfoil shape to create lift and maximize efficiency.

  10. Lift & Drag Forces • The Lift Force is perpendicular to the direction of motion. We want to make this force BIG. • The Drag Force is parallel to the direction of motion. We want to make this force small. α = low α = medium <10 degrees α = High Stall!!

  11. Twist & Taper • Speed through the air of a point on the blade changes with distance from hub • Therefore, tip speed ratio varies as well • To optimize angle of attack all along blade, it must twist from root to tip Fastest Faster Fast

  12. Rotor Design for a 200kW wind turbine • Design is begun with choosing of variety parameters of rotor and an airfoil. • The primitive blade shape is determined using an optimum shape blade using Blade Element Momentum (BEM) theory by considering wake rotating, drag, tip losses and ease of manufacturing. • In our design, the RISØ type airfoils is used for a 200 kW wind turbine.

  13. Linearized Twist & Taper • Ease of manufacturing • Reduce costs

  14. Lift & Drag for linearized blade • Lift & Drag coefficients across the blade from root to tip of blade

  15. Power Coefficient v Tip Speed Ratio • Lower maximum power coefficient at lower tip speed ratio for the linearized blade

  16. Pitch Control vs. Variable speed • pitch control (left) • variable speed and constant rotational speed (right) • ωmax= 32.38 r/min

  17. Conclusions • The linear blade distribution of twist angle and chord maintains ease of manufacturing and reduce costs. • Wind tip speed ratio, nominal wind speed and diameter of rotor can be tuned for better performance. • The overall power coefficient CP is reduced to the value of 0.36 for the linear design and is merely recommended for small applications. • Pitch control system was used to calculate the annual power generation for the province of Semnan using this simplified linear rotor. • Works undergo for a general optimization combined with linear approximation.

  18. THANK YOU ALL!

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