Aerodynamics and Design for Ultra-Low Reynolds Number Flight
Aerodynamics and Design for Ultra-Low Reynolds Number Flight
Aerodynamics and Design for Ultra-Low Reynolds Number Flight
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Electro-mechanical Efficiency<br />
0.20<br />
0.15<br />
0.10<br />
FIGURE 6.16 Experimental <strong>and</strong> modeled efficiency of the 5mm Smoovy system.<br />
Chapter 6<br />
For a rotor with radically different thrust/power versus RPM characteristics, this single<br />
parameter model fails because it in effect is assuming that the torque-loading versus<br />
RPM is the same <strong>for</strong> all samples. The test cases considered are not identical in this<br />
respect but are close enough that the total deviation in efficiency at any RPM is<br />
approximately 1%.<br />
Power Test 1<br />
Power Test 2<br />
Quadratic Fit Model<br />
0.05<br />
15000 20000 25000 30000 35000<br />
RPM<br />
40000 45000 50000 55000<br />
The resulting power required <strong>for</strong> the four-blade 2.5cm diameter rotors is presented in<br />
Figure 6.17. The data <strong>for</strong> the small-hub version is directly obtained by experiment.<br />
Once again the per<strong>for</strong>mance of the small-hub version st<strong>and</strong>s out. The deflection of the<br />
rotor due to rotation unloads the rotor to such <strong>and</strong> extent that the power required is<br />
reduced almost to the zero-thrust base drag value. For the remaining cases, we see<br />
trends similar to those <strong>for</strong> the two-blade ten inch diameter rotor. The rapid analysis<br />
method predicted power compares well at lower RPM with increasing discrepancies as<br />
RPM is increased, reaching 15% at 50,000 RPM <strong>for</strong> the aluminum rotor, but closer to<br />
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