Volume Flow of a Propeller

[BEMPE16524]

Hi All,

I'm sure there is a correct formula to calculate the volume flow rate.
But i just want to know if my common sense is generally correct or wrong.

Volume flow per revolution of a propeller = 3.142 x (radius of propeller)^2 x L (as in photo) x no. blade?

Thanks in advance.



R.Efendy

 

[zeusfaber]

Can't see it being proportional to the number of blades.

There's going to be an efficiency term (which could even be greater than one) as drag and swirl prevent the medium from travelling the full distance 'L' during one turn of the shaft, while some medium outside the swept diameter will also be delivered. I'd expect the number and shape of blades to have an effect on this term.

A.

 

[LittleInch]

Nother so simple.

Propellors are seriously odd things.

Try this for size

http://www.aerodynamics4students.com/propulsion/blade-element-propeller-theory.php

There's so many things which happen that can't be calculated.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BEMPE16524]

thanks for your help.
i think i get the idea.

Lift = 0.5 x rho x V^2 x A x CL where

rho = medium density
V = propeller speed
A = Nozzle area
CL = lift coefficient

So, if by any mean i have a thrust at specified RPM, i can find the propeller speed at average blade lenght (in this case is half)

E.g:
RPM = 1400,
Nozzle Diameter = 350mm
Area = 0.096m^2
No. of rev for 1 second, 1400/60sec = 23 rev

Average speed at half blade length:
Blade length = 350/2 = 175mm
Half blade length = 175/2 = 87.5mm
Circumference at half blade = 2 x 3.142 x 87.5 = 550 mm

V = 0.55m x 23 rev/sec = 12.65m/sec

m dot = mass flow rate
r = half nozzle diameter = blade length
Vp = propeller speed
A = nozzle area

m dot = r * Vp * A
= 1020kg/m^3 x 12.65 m/sec x 0.096 m^2
= 1241 kg/sec

Volume flow rate = (1241 kg/sec) / (1020 kg/m^3) = 1.217 m^3/sec

R.Efendy

 

[PNachtwey]

What about the pitch?
It is time for a internet search.
I am sure this has been worked out before.


Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com

http://forum.deltamotion.com/

 

[Jacc]

https://www.eng-tips.com/threadminder.cfm?pid=407

 

[BEMPE16524]

PNachtwey (Electrical)26 Jul 20 18:22
What about the pitch?
It is time for a internet search.
I am sure this has been worked out before.

not just the pitch, you should consider blade angle, twist angle, blade profile, hub diameter, blade friction, bla, bla, bla....

i just need a very basic estimation at the moment.

R.Efendy

 

[LittleInch]

Well that huge coupling in front of the propellor is going to have a big impact for starters.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[hydtools]

This book is in the public domain.

Ted

 

[BEMPE16524]

This book is in the public domain.

that is a one very good book. Thanks. I have more ideas to solve my proposal to a multi-million dollars project....

R.Efendy