ducted fan
ducted fan
(OP)
Hello I'm looking for information all information is greatly appreciated
I need to greatest thrust using a combination of fans and blade size??? I would like to try and generate about a thousand pounds of thrust using the smallest diameter fans.
does using a series of fans in one duct generate more thrust in a smaller area ????? if so what size diameter fans could I use to generate a thousand lbs of thrust using any combination of fans to achieve my target thrust without going over 12" diameter????
thanks..
I need to greatest thrust using a combination of fans and blade size??? I would like to try and generate about a thousand pounds of thrust using the smallest diameter fans.
does using a series of fans in one duct generate more thrust in a smaller area ????? if so what size diameter fans could I use to generate a thousand lbs of thrust using any combination of fans to achieve my target thrust without going over 12" diameter????
thanks..





RE: ducted fan
and
mdot=rho*A*V (continuity equation)
So the crudest approximation is that 4000=V^2*rho*A
so V=sqrt(4000/1.2/.15^2/pi)
V=217 m/s
That is too close to the speed of sound to expect to get away without compressibility effects, which engine designers call Mach choking. Then add in realistic efficiency for ducted fans (60% at best), and the answer is more firmly no.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: ducted fan
and it's "ducTed".
another day in paradise, or is paradise one day closer ?
RE: ducted fan
thank you
RE: ducted fan
RE: ducted fan
The equations are all there
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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RE: ducted fan
if you try to sequence fans, first you need to carefully design them (I'm assuming you're using fixed pitch) as the downstream fan is working in a different airstream to the first fan. 40 lbs thrust is limited by the tip speed of the fan (and not the deltaV of the airflow), according to the trusty internet but you are still limited by sonic airflow inside the duct. I'd suggest setting the downstream fan to be contra-rotating. Multiple fans is starting to sound like a turbine, so research how these are designed.
If this is a homebuilt, build something and test it.
another day in paradise, or is paradise one day closer ?
RE: ducted fan
with such enthusiasm. I remember a lesson in school my science teacher said "The gift of knowledge is a privilege to be shared the ability to educate is a gift to be honored without prejudice"
I thank all of you for your serious reply's and well thought out advice.
You truly are a credit to higher education.
It was once said that Thomas Edison knew all there was to know about electricity then he met Nicola Tesla.
RE: ducted fan
another day in paradise, or is paradise one day closer ?
RE: ducted fan
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: ducted fan
All these equations apply to static thrust, if the aircraft is moving in the axial direction then the equations change slightly I think.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: ducted fan
As soon as I finish my research I will build my prototype I have a full machine shop CNC. machines, mills, lathes and a flow jet cutter equipment I have used most of my life I can make just about anything
I only asked a couple questions I promise I am not here to bother anybody sorry for bothering you/
I hope nobody else asks me to read the policies again its been mentioned 3 x now.
yes I have read the policies something I did not do when I joined.
I thought this site was about professionals helping each other?????
RE: ducted fan
Those are bylines, not specifically directed at you
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: ducted fan
The MQ-8 Firescout take-off weight is about 3x your desired thrust with a 27.5 ft diameter rotor.
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: ducted fan
another day in paradise, or is paradise one day closer ?
RE: ducted fan
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: ducted fan
https://en.wikipedia.org/wiki/Disk_loading
In particular, the relationship between disk loading and efficiency:
Most light-to-medium lift helicopters operate at less than 10 lbs per square foot, yielding an efficiency of over 12 lbs of lift (or thrust) per horsepower. A disc of 1' in diameter has an area of slightly less than 1 square foot (0.785 square feet) so 1000 lbs of thrust would imply a disk loading of almost 1300 lbs per square foot which would put the efficiency at less than 2 lbs of thrust per horsepower (6X worse). On the chart above, that's in between the zones of "Lift Fan" (like the F-35 joint strike fighter) and "Direct Lift" (like the Harrier.)
RE: ducted fan
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?