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Airfoil Design for a Helicopter rotor blade

Airfoil Design for a Helicopter rotor blade. Oct. 2002 Han Gil Chae. Overview. Introduction Aerodynamic Characteristics of a Rotor Blade Design Strategies Design Procedures Survey Optimization Methods Analysis Tools Flow Solvers Optimization Code Conclusions. Introduction.

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Airfoil Design for a Helicopter rotor blade

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  1. Airfoil Design for a Helicopter rotor blade Oct. 2002 Han Gil Chae

  2. Overview • Introduction • Aerodynamic Characteristics of a Rotor Blade • Design Strategies • Design Procedures Survey • Optimization Methods • Analysis Tools • Flow Solvers • Optimization Code • Conclusions

  3. Introduction Aerodynamic Characteristics of a Rotor Blade

  4. Angle of attack qtw = -8 deg, m = 0.25 When Rotation Meets Translation... • An airfoil section meets different speed of air Periodically. • Angle of attack changes Periodically. • Point design may not be optimum.

  5. Design Strategies Design Procedure Survey Optimization Methods

  6. Point Design : Airfoil from Cp Find an airfoil which meets given Cp distribution • May satisfy all the characteristics we want • Difficult to get the optimum Cp distribution

  7. Point Design : Airfoil from Cl, Cd Find an airfoil which gives the best Cl/Cd characteristics Single point Multi points • Easier than Cp • Possible worse performance at off-design points • May cause uneven surface

  8. Robust Design : Design for uncertainties Probability of change in design point is considered Single point Robust • Better way for rotor blade airfoil • Still dealing with static characteristics

  9. Dynamic Design : Near to the reality Dynamic characteristics are considered • The Best way for rotor blade airfoil • Requires an unsteady solver • Requires tremendous time

  10. Optimization Methods MGM • Restricted to design with Cp Numerical • Suitable for most applications • May cause unexpected results RSM • Suitable for time consuming codes • Limited design range

  11. Analysis Tools Flow Solvers Optimization Codes

  12. Analysis Tools in Hand Code Method Restriction Language XFOIL Panel Subsonic Steady Fortran Pablo Panel Subsonic Inviscid Steady Matlab S2d N/S Steady Fortran Potential Potential Steady Inviscid Fortran

  13. Analysis Tools : Validation CL CD CM NACA 0015, M=0.29, Re=1.59e6 CL/CD • XFOIL gives reasonable solution in seconds

  14. Analysis Tools : Validation Cp Distribution NACA 0012, M=0.63, a=2 deg NACA 0012, M=0.72, a=0 deg • Most of codes generate good solutions

  15. Optimization : Procedure • Steepest Ascent Method Find Steepest Direction Calculate Derivatives Calculate Object function Call XFOIL Modify Airfoil Shape Call XFOIL Compare for Minimum

  16. Optimization : Shape functions • Polynomial functions • Hicks-Henne functions

  17. Optimization : Valication • Symmetric Airfoil (NACA 64-015) Polynomial Hicks-Henne

  18. Optimization : Valication • Cambered Airfoil (NACA 64110) Polynomial Hicks-Henne

  19. Conclusions What was done Further study

  20. What was done • Design method survey - Robust design method were selected • Analysis tool survey - XFOIL were selected • Optimization method - Steepest Ascent • Validation • XFOIL gives reasonable results • Hicks-Henne Shape function gives better results

  21. Further Study • Basic sizing for reasonable M, Re and a • Random number generation for robust design • Modification of shape functions for T.E • Modification of optimization code

  22. Questions ? Thank you

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