How Can I Calculate The Thrust of a Given Propeller?

In summary, calculating the thrust of any given propeller is not a simple task. In the past, model propellers were tested and the values were scaled up, but now computational fluid dynamics is used for design purposes. However, model testing is still relevant. There have been developments in this area, such as the resources provided by NASA and RC enthusiast forums, but the complexity of the calculation depends on the specific parameters and needs of the propeller.
  • #1
sjmay
5
0
I'd like to know how to calculate the thrust of any given propeller
 
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  • #2
Not a simple calculation. In the past, model propellers were tested and the thrust values obtained were scaled up to full size units. Now, computational fluid dynamics (CFD) can be used for preliminary design purposes, but model testing has not been rendered entirely obsolete.
 
  • #3
What if I were to assume zero free stream velocity?
 
  • #4
I'd like to know how to calculate the thrust of any given propeller
You and about every aerospace and marine engineer in the World!
But there has been a lot of work on this a you can get good ballpark figures for specific configurations.
See:

http://www.grc.nasa.gov/WWW/k-12/airplane/propth.html
... simplified theoretical framework courtesy of NASA.

http://www.gobrushless.com/testing/thrust_calculator.php
... a simple thrust calculator for specific kinds of prop.

So... how complex it is depends on what you want to know for.
 
  • #5
The NASA link you sent me was very helpful, though it did seem a little too good to be true (the equations were very simple and easy to follow). I'm determining thrust for a propeller on a light RC airplane. In your second link, a specific thrust was given at a given altitude for a given RPM value. But isn't the free stream velocity also a critical parameter in determining propeller thrust?
 
  • #6
The NASA link is very simplistic - for an RC craft you want to guarantee more than you need and throttle back.
The thrust calculator seems a little optimistic - I think it is for static thrust only and they make a lot of assumptions.

You should check on RC enthusiast forums.

http://www.rcfaq.com/RPMSTATS/propfaq.htm
 

1. How can I calculate the thrust of a given propeller?

To calculate the thrust of a given propeller, you will need to know the diameter and pitch of the propeller, as well as the number of blades and the rotational speed. You can use the equation: Thrust = (0.0005 x Diameter x Pitch^3 x Number of Blades x Rotational Speed^2) / 1000.

2. What is the unit of measurement for thrust?

Thrust is typically measured in pounds (lbs) or newtons (N).

3. Is there a specific formula for calculating thrust or does it differ depending on the propeller?

There is a general formula for calculating thrust, as mentioned in the first question. However, there may be variations in the formula for different types of propellers, such as fixed-pitch or variable-pitch propellers.

4. How does the angle of attack affect the thrust of a propeller?

The angle of attack, which is the angle between the propeller blade and the oncoming air, can affect the thrust of a propeller. A higher angle of attack can increase the thrust, but too high of an angle can also cause the propeller to stall and decrease thrust.

5. Are there any other factors that can affect the thrust of a propeller?

Yes, in addition to the factors mentioned in the first question, other factors such as air density, airfoil shape, and blade surface roughness can also affect the thrust of a propeller. These factors may vary depending on the specific design and use of the propeller.

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