Ducted Fan Possibility?

[zephyrus66]

Hey all-- Ain't my area but want to start this project and need to know a but more about ducted fans. Is it feasible or efficient to make an aircraft/glider with a ducted fan(abt.18"-24"dia)powered by electric motor & battery? Thanks much for any tips.

 

[IRstuff]

Battery powered aircraft tend to need absurdly height lift-to-weight ratios, since the battery's power density is so poor compared to a fueled-engine. You can get some idea of the relative merits by looking at the toy market.

TTFN

FAQ731-376

 

[GregLocock]

Yes it is possible. However that is an enormous fan, it would need a large motor to power it, which implies a lot of batteries.

It would not be efficient, and it wouldn't glide very well.

If you want an full size electric glider, that is certainly possible. 20 years ago somebody built a solar powered glider and crossed the uSA in it.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[zephyrus66]

Thanks for your input guys. Ya it's definitely more in the theoretical stage right now. But with developing motor/controller technology from Raser tech.and promising developments with ultracapacitors from EEStor(supposedly can put out 52kWh and is being licensed for use by Zenn electric car co.) and carbon nanotubes, I think the notorious weight and energy limitations of batteries(ultracaps--more like it)seems to be quite rapidly disappearing. This kind of power I hope can allow me to keep the fan diameter down to around 24". And this kind of technology I hope will one day soon make this glider a practical reality. Below I pasted some specs from Raser's site of their motor and controller technology. And also info page on PESWiki on the EEstor ultracap. Let me know what you guys think, or if I'm just crazy and naive.

http://www.rasertech.com/monaco.html

http://peswiki.com/index.php/Directory:EEStor

Motor:
Motor Size: 8" long x 12.5" diameter
Power: 500 hp peak @ 6200 rpm
Weight: 147 lbs (67 kg)
Air Cooled
Note: Liquid Cooling Configuration Delivers higher performance

Controller:
Advanced Symetron 437 kW High Performance Drive
Size: 22.7" long, 12" high, 13.4" wide
98% efficiency rated
Proprietary Symetron software
Input rating: 200 to 400 V (DC); 312 V nominal/ 500 V maximum
Output rating: 350 VRMS continuous, 1250 ARMS peak
Frequency Range: up to 15,000 rpm

 

[GregLocock]

You forgot to add

supercapacitor

to supply 400kW for 1 minute

weight=2400 tons.

Bzzt

Thank you for playing

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IRstuff]

I think Greg exaggerated a bit. I got a whole hour with 1 ton of supercap:

500hp*hr/350Wh/kg = 1065kg, based on 52kWh/336lb

TTFN

FAQ731-376

 

[GregLocock]

Oops, yes, maths error. Wh/kg grumble grumble...



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IRstuff]

A ton is still non-trivial, considering that the same mass in gasoline will provide 500 hp for 36 hr.



TTFN

FAQ731-376

 

[berkshire]

While ducted fan systems tend to be somewhat inefficient.
There are battery powered self launching sailplanes.that use a 35 to 45 kw motor turning a slow turning propellor. Check the link for an example.

http://linuxdevices.com/articles/AT7732522579.html

B.E.

 

[IRstuff]

Right, but reading the article, the battery essentially has ~15min of life: 42kW/11kWh. It's ideal for a sailplane application, since it's only used intermittently to boost the plane when there are no thermals to be had.

TTFN

FAQ731-376

 

[berkshire]

IRstuff (Aerospace)
It does not even do that, it simply gets the aircraft to an altitude where it can use thermals or other lift.
After that its pretty much done.

The ducted fan idea in sailplanes/ gliders was explored in the 1970s and a couple of gasoline powered types were built in Germany, they used 4 vents to expose the duct for use. they did not do well and the idea was abandoned.
B.E.

 

[zephyrus66]

Wow --so when using that much power the craft gains that much weight in tons? So when the all electric powered Tesla Roadster's Electronics Module controls over 200 kW of electrical power during peak acceleration does it also gain this tonnage? I guess I just don't get how electronic systems with this much power work. Thanks again guys for the feedback.

Motor
Type designation 3-phase, 4-pole electric motor
Max net power 185kW
Max rpm 13,500
Efficiency 90% average, 80% at peak power
Torque see torque curve chart

http://www.teslamotors.com/efficiency/how_it_works.php

 

[GregLocock]

cars use a very small proportion of the motr's potential performance, most of the time.

Aircraft use a fairly high proportion of their motor's potential performance, continuously.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[berkshire]

zephyrus66 (Materials)
If you look at the drawings for this car off your web link, you will see that the battery takes up the entire space behind the seats. Lithium ion batteries are not light, how much do you think this would weigh?
B.E.

 

[IRstuff]

The data is hardly secret:

http://www.batteryuniversity.com/partone-5A.htm

The Li battery has an energy density 1/70 of gasoline.

http://www.cat.com/cda/files/192183/7/PEHJ0073.pdf

A truck battery has an energy density 1/317 of gasoline

The supercap cited earlier has an energy density 1/36 of gasoline.

TTFN

FAQ731-376

 

[zephyrus66]

Hey Berkshire,

I was hoping to keep it under 5 or 600lbs. Thanks for your response.

And Thanks alot Greg and IRstuff!! I really appreciate all your input.

 

[mjetbug]

hi zephyrus66,
this may sound a little wild....but have you thought of a multi-ducted-fan-litium-polymer-battery setup.
one of the biggest ducted-fan used on RC jet-models (120mm) gives you about 35lbs thrust per piece !!!

 

[WKTaylor]

Folks... for giggles...

An electric-powered ultralight is presented for sale at this website...

http://www.electraflyer.com/

Regards, Wil Taylor