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HW II – AE 6070 GA TECH

HW II – AE 6070 GA TECH. Michael Duffy September 27 th , 2006. Rotor Inflow Distribution. *Note the HW called for Momentum theory, however, I show the same results using BET (w/uniform inflow). Blade Element Theory (Empirical), K=1.1. Blade Element Theory (Ideal), K=1.0. λ , Inflow.

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HW II – AE 6070 GA TECH

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  1. HW II – AE 6070GA TECH Michael Duffy September 27th, 2006

  2. Rotor Inflow Distribution *Note the HW called for Momentum theory, however, I show the same results using BET (w/uniform inflow) Blade Element Theory (Empirical), K=1.1 Blade Element Theory (Ideal), K=1.0 λ, Inflow Assumptions • Ct = 0.008 • Cl = 5.7 a, Cd = 0.0087 – 0.02167 a + 0.4 a2 • s= 0.1 • tw = -8 degrees • B = 0.97 • k = 1.1 • Cutout = 7% • Cdo = 0.01 (for simple performance estimate) • a = 5.7 (per radian) Blade Element Theory (no twist) Blade Element Theory (Twisted) x = r/R * Note All data is provided in .xls file attached

  3. Cp/Sigma vs. Ct/Sigma *Note I take a slightly different approach then the HW calls for. First I use BEMT for all curves except the Simple Curve. To simulate BET, I just adjust the twist to allow for uniform inflow. I also do not use the B factor for tip loss, rather I use the Prandtl tip loss factor which is dependent on the number of blades and thrust setting. Finally, I vary pitch to get different thrust settings and thus different Cp and Ct curves rather then varying sigma. I keep sigma fixed at ~0.1. Please keep this in mind when comparing to the curves given in the hw example. Simple Moment Theory BET w/no losses and uniform inflow BEMT no tip losses BEMT w/Prandtl tip losses Cp/Sigma Assumptions • Ct = 0.008 • Cl = 5.7 a, Cd = 0.0087 – 0.02167 a + 0.4 a2 • s= 0.1 • tw = -8 degrees • B = 0.97 • k = 1.1 • Cutout = 7% • Cdo = 0.01 (for simple performance estimate) • a = 5.7 (per radian) Ct/Sigma * Note All data is provided in .xls file attached

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