X Prize Clean Aviation: $10 million

mheslep

Quote by Cyrus

Want a PhD? Hehehe, honestly, I think its all empirical. The equations look like the NS equations: no closed form solutions.

Yes silly question but I thought some rough bounds could be put on the maximum noise. For instance, if 60HP is converted completely to audible sound (of course its not) how loud is that, assuming no resonance or amplification.

Cyrus

Quote by mheslep

Yes silly question but I thought some rough bounds could be put on the maximum noise. For instance, if 60HP is converted completely to audible sound (of course its not) how loud is that, assuming no resonance or amplification.

I'll ask someone I know about a relationship to noise. I think its something like the log of the disk loading.

Cyrus

Quote by mheslep

For illustration:

NEMA electric motor efficiency requirements
Power
(hp) Minimum Nominal Efficiency
1 - 4 78.8
5 - 9 84.0
10 - 19 85.5
20 - 49 88.5
50 - 99 90.2
100 - 124 91.7
> 125 92.4

I suspect the typical RC motor is 0.1 to 0.01 HP. You get the idea.
http://www.engineeringtoolbox.com/el...ncy-d_655.html

On takeoff, my motor would draw almost ~750W. The speed controller was rated at 100A max.

mheslep

Quote by Cyrus

On takeoff, my motor would draw almost ~750W. The speed controller was rated at 100A max.

What's rated power of the motor? That's a nice thing about electrics - they can peak well above rated (5x at least).

Cyrus

http://www.allerc.com/z40all.htm

~1100W

mheslep

Quote by Cyrus

http://www.allerc.com/z40all.htm

~1100W

I don't see efficiency or output power, only input, but its still impressive. 3kW/kg (input) continuous in 1.9" OD case. That compares to, say, 4kW/kg (output) in the much larger Tesla AC induction motor.

FredGarvin

You asked for it. I scanned this in from one of my references. The mB notation refers to the mth harmonic/mode and B is the number of blades. The rest should be somewhat decipherable.

Cyrus

Quote by mheslep

I don't see efficiency or output power, only input, but its still impressive. 3kW/kg (input) continuous in 1.9" OD case. That compares to, say, 4kW/kg (output) in the much larger Tesla AC induction motor.

Boy let me tell you, those guys get HOT.

FredGarvin

So do the lithium batteries most of them use for power.

mheslep

Quote by FredGarvin

You asked for it. I scanned this in from one of my references. The mB notation refers to the mth harmonic/mode and B is the number of blades. The rest should be somewhat decipherable.

Thanks Fred!

FredGarvin

BTW...This all stems from the basic wave equation. I sat through many a proofs showing this stuff and it is amazing to see just how much can be pulled from such a seemingly unimposing equation. You may want to look up Ffowcs Williams for a reference.

Cyrus

Bessel function, wave equations??? Eeeeuccccwkkkk!

Quick, something more pleasing to the ear: Laplace transforms, Bode Diagrams, Nyquist plots, PSD, Autocorrelations.......ahhhhhhhhhhh. I can breathe again, whew.

Cyrus

I'll tell you what, if you guys want to formulate a list of questions, I can email them to Dr. Moore and report back his answer. I'd prefer to keep the list short, so think of good ones.

FredGarvin

Quote by Cyrus

Quick, something more pleasing to the ear: Laplace transforms, Bode Diagrams, Nyquist plots, PSD, Autocorrelations........

huh...wha?...hmmm.....

mheslep

Quote by FredGarvin

So do the lithium batteries most of them use for power.

A good Li Ion is ~95% efficient on discharge at room temperature (unlike lead acid), so Cyrus's RC battery would shed 55W of heat on take off, probably 5W cruise. In a small package w/ no thermal path, yes I imagine that gets very hot. If so, RC'ers might consider measures to cool them, as running a Li Ion hot will degrade its lifetime.

FredGarvin

All of the ones I have used and seen have no external means for cooling other than some form of exposure to the outside air.

mheslep

Quote by FredGarvin

You asked for it. I scanned this in from one of my references. The mB notation refers to the mth harmonic/mode and B is the number of blades. The rest should be somewhat decipherable.

Think I have it all except for theta, the 'retarded radiation angle'??? I would expect the SPL is not isotropic, so maybe this is addresses the acoustic pattern?

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