So I've been dabbling in prop design for a while, using Java Foil and Java Prop. My issue is that some results appear to be too good to be true and I don't understand why. I'm not an aerodynamicist or engineer and have only a high level understanding of the physics involved.
The specific issue that I'm having is that a propeller, designed for static operation, has a calculated FM far greater than 1 - 2.27 to be precise. This is obviously an impossible efficiency figure, but I don't know why.
What I've done is to take one of Martin Hepperle's airfoils, MH116 and re-analyze it in Java Foil for Re=100,000 and 200,000 as these are closer to the average operating condition across the radius stations of the blade. His default is Re=500,000. I export the polar and import into Java Prop.
The other Java Prop inputs are Number of Blades = 3, RPM = 3000, Diameter = .635m (25"), Spinner Dia. = .1m (4"), Velocity v: = .05 m/s (can't set to 0 because the equations break down), Power = 500W.
After tweaking angle of attack for best thrust I get a thrust figure of 100.39N. That's about 10.2kgf! If I plug that thrust figure into the ideal power equation I get 1135.7W for a 100% efficient actuator disk. 20.4g/W is also a nice number, but to get that at such an extremely high disk loading is just fantasy. I realize that there are limitations to this kind of analysis and design tool. However this error is so large that I am convinced that I am missing something.
I have emailed Dr. Hepperle, and he has been kind enough to respond to questions in the past. However I don't wish to bother him too much with amateur questions. So I hope to learn what I can from other resources. Can anyone help?
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Please see the document attached to the above post. It shows the majority of the Java Prop inputs and outputs in a mostly legible format.