Transcript HW II – AE 6070 GA TECH

HW II – AE 6070
GA TECH
Michael Duffy
September 27th, 2006
Rotor Inflow Distribution
*Note the HW called for Momentum theory, however, I show the same results using BET (w/uniform inflow)
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Blade Element Theory (Empirical), K=1.1
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Blade Element Theory (Ideal),
K=1.0
λ, Inflow
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Assumptions
Ct = 0.008
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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)
Michael Duffy
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Blade Element Theory
(Twisted)
Blade Element Theory
(no twist)
AE 6070, HW 2
Sep. 23 th, 2006
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0
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x = r/R
* Note All data is provided in .xls file attached
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Cp/Sigma vs. Ct/Sigma
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*Note I take a slightly different approach then the HW calls for. First I use BEMT for all curves except the
BEMT w/ Prandtl tip losses
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
BEMT no tip losses
given in the hw example.
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Cp/Sigma
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Simple Moment Theory
BET w/no losses and uniform inflow
BEMT no tip losses
BEMT w/Prandtl tip losses
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Simple Moment Theory
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BET with no losses and uniform inflow
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Assumptions
Ct = 0.008
Cl = 5.7 a, Cd = 0.0087 – 0.02167 a + 0.4 a2
s = 0.1
tw = -8 degrees
Michael Duffy
B = 0.97
AE 6070, HW 2
k = 1.1
Cutout = 7%
Sep. 23 th, 2006
Cdo = 0.01 (for simple performance estimate)
a = 5.7 (per radian)
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Ct/Sigma
* Note All data is provided in .xls file attached
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