theory help

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Roopah Vi Tam - 29 May 2004 04:55 GMT

Hi there,

I am leading a study on a convertiplane and I need some theoretical
information regarding the propulsion: given a 2-blades hover of M=590 Kg
(1400lbs) with 2.55 m2 (27.5926 ft2) for both blades, my question is: At
what speed approximately must the rotor turn in order to generate enough
lifgt to hover the machine?

Does anybody know a site where I can find more info/courses about helicopter
propulsion?

THX all!

RVT

PS: I dunno if my question is in teh correct forum, but I hope nobody sees
an inconvenient :-(

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golfietis - 29 May 2004 07:25 GMT

Good day..

Generally rotor`s RPM is first parameter then you are calculating
helicopter`s aerodynamics. Normally rotor`s tip speed varies about 600-700
kph. So, you have rotor`s RPM for specific diameter. Now you have to choose
proper airfoil, which will generate requied amout of lifting force.

golfietis

Lithuania

> Hi there,
>
[quoted text clipped - 13 lines]
> PS: I dunno if my question is in teh correct forum, but I hope nobody sees
> an inconvenient :-(

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Roopah Vi Tam - 29 May 2004 08:21 GMT

just before I do the calculations, RPM stands for? (sorry: I am a beginner
in helicopter aerodynamics ...)

THX for all

RVT

> Good day..
>
[quoted text clipped - 25 lines]
> > PS: I dunno if my question is in teh correct forum, but I hope nobody sees
> > an inconvenient :-(

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golfietis - 29 May 2004 09:15 GMT

Yes,

for eg. you rotor diameter is 2 meters, and tip speed is 600 kph. Then you
rotor RPM will be:

RPM=Blade Tip Speed *60/Pi X Rotor Diameter

where Pi = 3.14

tip speed is this equanation is in m/s, rotor diameter - m,

golfietis

> just before I do the calculations, RPM stands for? (sorry: I am a beginner
> in helicopter aerodynamics ...)
[quoted text clipped - 33 lines]
> sees
> > > an inconvenient :-(

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golfietis - 29 May 2004 09:20 GMT

lets calculate your rotors RPM:

RPM=166 m/s*60/3.14*2 = 1592 RPM

and this is pnly first iteration of calculation - your rotor propertys will
later change depending of a lot of other parameters....

golfietis

Lithuania

> Yes,
>
[quoted text clipped - 50 lines]
> > sees
> > > > an inconvenient :-(

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Roopah Vi Tam - 29 May 2004 10:57 GMT

ok thanks I got it (RPM= round per minute: I was trying to understand that

:-o)

By the way, for the Blade Element Theory, how can calculate n for a NACA0014
for eg; where n is such that: lambda(r)=lambda(tip)*r^n ?

I need to know r(=y/R) for the airfoil...where can I find it?

THK beforehand

RVT

> lets calculate your rotors RPM:
>
[quoted text clipped - 65 lines]
> > > sees
> > > > > an inconvenient :-(

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golfietis - 29 May 2004 12:10 GMT

o man, I think you need to go to neariest technical library and find there
kind of "Helicopter aerodynamics"....

o use www.google.com

golfietis

> ok thanks I got it (RPM= round per minute: I was trying to understand that
> :-o)
[quoted text clipped - 80 lines]
> > > > sees
> > > > > > an inconvenient :-(

Reply to this Message

Philip Martin - 29 May 2004 10:59 GMT

> just before I do the calculations, RPM stands for? (sorry: I am a beginner
> in helicopter aerodynamics ...)

RPM = Revolutions Per Minute. Not kind of just specific to helicopters:o)

Phil Martin.

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Model Forum / Radio Controlled / Helicopters / May 2004

theory help