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X Prize Clean Aviation: $10 million

by mheslep
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mheslep
#55
Jan21-10, 09:24 PM
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Quote Quote by Cyrus View Post
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
#56
Jan21-10, 09:36 PM
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http://www.allerc.com/z40all.htm

~1100W
mheslep
#57
Jan21-10, 09:44 PM
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Quote Quote by Cyrus View Post
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
#58
Jan21-10, 09:45 PM
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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.
Attached Thumbnails
PropNoise.jpg  
Cyrus
#59
Jan21-10, 09:46 PM
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Quote Quote by mheslep View Post
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
#60
Jan21-10, 09:48 PM
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So do the lithium batteries most of them use for power.
mheslep
#61
Jan21-10, 09:48 PM
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Quote Quote by FredGarvin View Post
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
#62
Jan21-10, 09:51 PM
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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
#63
Jan21-10, 10:31 PM
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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
#64
Jan22-10, 12:09 AM
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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
#65
Jan22-10, 11:28 AM
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Quote Quote by Cyrus View Post
Quick, something more pleasing to the ear: Laplace transforms, Bode Diagrams, Nyquist plots, PSD, Autocorrelations........
huh...wha?...hmmm.....
mheslep
#66
Jan22-10, 01:03 PM
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Quote Quote by FredGarvin View Post
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
#67
Jan22-10, 01:13 PM
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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
#68
Jan22-10, 01:29 PM
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Quote Quote by FredGarvin View Post
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?
mheslep
#69
Jan22-10, 01:47 PM
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Quote Quote by Cyrus View Post
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.
On the subject of prop/fan noise, I expect that his answer would concur w/ the article which he probably informed:

Quote Quote by SIAM
At up to 95 percent efficiency, electric motors are far more efficient than internal combustion engines, which only rate some 18 to 23 percent. This means electric aircraft are much quieter than regular planesóat some 150 meters, it is as loud as 50 decibels, or roughly the volume of a conversation, making it roughly 10 times quieter than current low-noise helicopters.
You gents suggested otherwise upthread, so first I want to run the numbers from Fred's Propeller and Fan Noise reference; then we can ask a more informed question.
FredGarvin
#70
Jan22-10, 02:08 PM
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That is not a proper statement. It should read that the ENGINE noise is lower, not the overall aircraft noise. You can not change the acoustic performance of a prop by changing the thing that drives it. The prop noise will still be there.
mheslep
#71
Jan22-10, 02:24 PM
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Quote Quote by FredGarvin View Post
That is not a proper statement. It should read that the ENGINE noise is lower, not the overall aircraft noise. You can not change the acoustic performance of a prop by changing the thing that drives it. The prop noise will still be there.
Right, the implication of the SIAM statement is that engine noise dominates in a helicopter w/ combustion engine. That's why I'm running down the prop noise alone. SIAM says its 50dbL at 150 M, a number that can be calculated (if I can define the terms )

Assumptions per prop:
B (blades) = 4
y = sideline distance = 450 ft
D = 6 ft
T = thrust = 300 lbs takeoff
W = shaft power = 30 HP
c0 = 1000 ft/s
zeff = 0.8

I want worse case, so I'm bypassing all the modal analysis and setting the sincx and Bessel functions to one.

Edit:Still need help on defining theta? It can't be zero or the SPL is zero.
Cyrus
#72
Jan22-10, 04:29 PM
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Quote Quote by FredGarvin View Post
That is not a proper statement. It should read that the ENGINE noise is lower, not the overall aircraft noise. You can not change the acoustic performance of a prop by changing the thing that drives it. The prop noise will still be there.
According to the article, they made rotors with lower tip speeds to reduce noise as well.


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