How Can I Calculate The Thrust of a Given Propeller?

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    Propeller Thrust
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Discussion Overview

The discussion revolves around calculating the thrust of a given propeller, focusing on methods applicable to both model and full-size propellers. It includes considerations of theoretical frameworks, empirical testing, and computational fluid dynamics (CFD) in the context of aerospace and marine engineering.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant notes that calculating thrust is not straightforward and mentions the historical use of model testing and scaling for thrust values.
  • Another participant suggests using CFD for preliminary designs while acknowledging that model testing still has relevance.
  • A question is raised about the implications of assuming zero free stream velocity on thrust calculations.
  • One participant shares links to resources, indicating that while there are simplified theoretical frameworks available, the complexity of thrust calculations can vary based on specific needs.
  • Concerns are expressed regarding the simplicity of the NASA resource, particularly for RC airplanes, and the importance of free stream velocity in thrust determination.
  • Another participant critiques the thrust calculator for potentially being overly optimistic and suggests verifying information through RC enthusiast forums.

Areas of Agreement / Disagreement

Participants express differing views on the adequacy of simplified models and calculators for determining thrust, indicating that multiple competing perspectives exist regarding the complexity and accuracy of thrust calculations.

Contextual Notes

There are limitations noted regarding the assumptions made in thrust calculations, particularly the role of free stream velocity and the context of static versus dynamic thrust measurements.

Who May Find This Useful

This discussion may be useful for aerospace and marine engineers, hobbyists working with RC airplanes, and anyone interested in the principles of propeller thrust calculation.

sjmay
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I'd like to know how to calculate the thrust of any given propeller
 
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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.
 
What if I were to assume zero free stream velocity?
 
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.
 
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?
 
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
 

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