Ducted Fan Optimization

Blade element momentum theory (BEMT) is used to optimize the rotor blade geometry to maximize thrust for a given power available. Solutions are interated until power required equals power available.

• Rotor is assumed to be contained in duct - no tip losses calculated
• Natural exit area presumed - no thrust increase from expanded exit
• Constant induced velocity field along blade if possible
• Simple momentum theory equations are iterated to solve for thrust and induced velocity and shown for comparison

Rotor Properties Input

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Units: English / Metric

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Rotor Geometry

Rotor Diameter - D:
Hub Diameter - H:
Min Chord Length - c_min:
Max Chord Length - c_max:
Max Pitch - θ_max:
Min Pitch - θ_min:
Number of Blades - N_b:

Input Shaft

Rotor Rpm:
Power Available - P_a:

Airfoil Data

Airfoil Name:
Max 2D Angle of Attack (@Cl_max) - α_max:
Min 2D Angle of Attack (@-Cl_max) - α_min:
C_l versus α, Polynomial Fit Coef - C₁:
C_l versus α, Polynomial Fit Coef - C₂:
C_l versus α, Polynomial Fit Coef - C₃:
C_l versus α, Polynomial Fit Coef - C₄:
C_l versus α, Polynomial Fit Coef - C₅:
C_l versus α, Polynomial Fit Coef - C₆:
C_l versus α, Polynomial Fit Coef - C₇:
C_d versus α, Polynomial Fit Coef - D₁:
C_d versus α, Polynomial Fit Coef - D₂:
C_d versus α, Polynomial Fit Coef - D₃:
C_d versus α, Polynomial Fit Coef - D₄:
C_d versus α, Polynomial Fit Coef - D₅:
C_d versus α, Polynomial Fit Coef - D₆:
C_d versus α, Polynomial Fit Coef - D₇:

Reynolds Number Correction
Mach Number Correction

State

Vertical Climb / Farfield Inlet Velocity - V_c:

Analysis Parameters

Spanwise Analysis Points:
Chord Iteration Points:
Theta Iteration Points:
Maximum Iterations:
Tolerance (P_req to P_aval):

Note: Calculations take some time to complete. The browser will wait for a response from the server. Be patient.

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References

Stepniewski, W. Z. (1950). Introduction To Helicopter Aerodynamics, V1. Morton, Pa.

Leishman, J. G. (2008). Principles of Helicopter Aerodynamics. New York, NY.

Stepniewski, W. Z., Keys, C. N. (1984). Rotory-Wing Aerodynamics. Mineola, NY.

Johnson, W. (1980). Helicopter Theory. Princeton, NJ.

Weick, F. E. (1930). Aircraft Propeller Design. York, PA.

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