Air Pressure to Torque Question

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Discussion Overview

The discussion revolves around the relationship between air pressure and torque in a turbine system, specifically in the context of a personal project involving propulsion. Participants explore the theoretical implications of applying air pressure to turbine blades and the resulting torque produced.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Richard proposes that blowing air at 1000 psi through a turbine with one square inch paddles would result in 1000 lbs of torque, assuming no friction.
  • One participant clarifies that torque is a product of force and distance, suggesting that if 1000 pounds of force were applied at a radius of 1 ft, it would yield 1000 ft-lb of torque.
  • Another participant notes that the situation is more complex once the turbine is in motion, as the airflow speed and blade speed will affect torque.
  • Richard expresses interest in understanding how psi pressure translates to torque in a turbine system, indicating a desire to experiment with different methods of torque production.
  • One participant mentions that the initial torque may not be sustained once the airflow matches the blade speed, complicating the calculations further.
  • Richard inquires about online calculators or formulas to convert psi pressure on the turbine blades to horsepower.
  • A participant shares a link to a calculator but notes the importance of practical experimentation for accurate results.
  • Another participant suggests looking into a Pelton wheel, indicating that the force applied is related to the momentum change of the fluid striking the paddles.

Areas of Agreement / Disagreement

Participants express varying views on the relationship between air pressure and torque, with no consensus reached on the exact calculations or implications of airflow dynamics in a turbine system.

Contextual Notes

Participants acknowledge that the calculations are complicated by factors such as airflow speed, blade speed, and the specific design of the turbine, which may not be fully addressed in their discussion.

RSmith
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Hi Guys,

First time posting, sorry if this isn't the right place to post this kind of question. A personal project involving air pressure and propulsion has lead me to a question I hope somebody may know the answer to.

Imagine hypothetically you have a turbine that has paddles with a surface area of one square inch. It's held in an enclosed casing which has an inlet tube and an outlet tube - so if you blow through the inlet tube, the turbine spins and the air is explelled out of the outlet tube. A bit like a Turbocharger in a car. If you were then to blow air through the inlet tube at a pressure of 1000psi does that mean that the turbine would spin (friction on parts etc. excluded) with 1000 lbs of torque?

I figured this would be the case seeing as the paddles were 1 square inch and obviously psi is lbs per square inch.

Many thanks,



Richard
 
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Torque has a force and a distance so if the turbine had a radius of 1ft and you applied a force on the blade of 1000 pounds then you would have 1000 ft-lb of torque.
1000psi is quite high and 2ft diameter is large for a turbo!

Once it's moving the calculations are a little more complicated because it depends on the speed of the airflow and the speed of the blades.
 
Awesome. Yeah I know - the variables are quite drastic! I'm just experimenting with different methods of producing torque (as you probably guessed to something similar to a crankshaft in a car). I just wanted to know that the pressure in the air in lbs per square inch or lbs per square foot would equal out roughly to how much torque it would produce if blasted into a turbine system.
 
That's only the starting torque. Once the air is flowing into the turbine at the same speed as the blades are moving there is presumably no torque at all.
It's also going to be more complicated for real turbine shapes.
There are probably lots of resources on the web with figures for real units.
 
If that's the case would there be an online calculator / a formula to convert the psi pressure on the turbine blades to HorsePower?
 
Thanks! That looks v useful... I'll have to punch in some numbers.

The more I think about it though, I don't think anything anything will substitute for a good old fashioned practical experiment. I may have to set this test up over the weekend.
 
Last edited:

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