What is the Most Efficient Blade Design for an Air Driven Turbine?

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Discussion Overview

The discussion centers around the most efficient blade design for an air-driven turbine, specifically aimed at achieving high torque with minimal air volume. Participants explore various design considerations, applications, and the characteristics of air flow relevant to turbine performance.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that the optimal shape of a turbine blade depends on the characteristics of the air and the intended application, comparing it to wing design.
  • There is a proposal that maximizing torque may require a blade design that operates at lower speeds, potentially favoring a centrifugal fan design over a traditional propeller.
  • One participant emphasizes the need for additional specifics regarding size, weight, and cost constraints to provide a more tailored response.
  • A later reply questions whether the original poster's needs might be better met with a compressed air motor rather than a turbine, suggesting a vane type motor as a possible alternative.
  • Another participant expresses skepticism about the feasibility of creating a pneumatic tool at home, recommending the modification of existing devices instead.
  • Participants discuss the importance of gear reduction in achieving high torque, with some arguing that high RPM and power output may be more critical than initially suggested.

Areas of Agreement / Disagreement

Participants express differing views on the best approach to turbine design, with no consensus reached on the optimal blade shape or whether a turbine or motor is more suitable for the intended application.

Contextual Notes

Participants note limitations in the original question's clarity and the need for more specific design criteria to guide the discussion effectively.

zydubion
What is the most efficient shape of an air driven turbine?

I want to achieve the greatest possible torque with the lowest volume of air.

I hope I am posting this in the correct place. If not, any
links would be helpful. Thank you very much.
 
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It depends entirely on the characteristics of the air you are sending through it. Essentially a turbine blade is a wing - and the best shape of a wing depends on the intended flight envelope. So what exactly are you trying to do?

High torque would probably mean getting the most from the air volume you can at low speed. So something the shape of a fan might be best. But that will also mean relativly low power output.
 
That is a very broad question.

You'll need to list a few more specifics.

Size/weight restrictions?
Cost constraints?
What type of project is it being used for?
etc.
 
The application is for a small shop tool. The diameter of the turbine would be approximately 1.5 inches, while thickness should be less than 1/4 inch. Compressed air will enter the outer edge of the turbine via a nozzle. The output of the turbine will be interconnected to a substantial gear reduction and finallly to the work.
 
Look at it logically.

For maximum torque you want the blade to turn as slowly as possible, because of the torque/speed tradeoff, so you want a turbine with the maximum diameter. A propeller type blade is designed to turn fast, so that isn't what you're looking for. You basically need a cenrifugal fan, but operating as a turbine. You can arrange to discharge the air through only part of the perimeter of the turbine to match the load characteristics.
 
Originally posted by Tyger
Look at it logically.

For maximum torque you want the blade to turn as slowly as possible, because of the torque/speed tradeoff, so you want a turbine with the maximum diameter. A propeller type blade is designed to turn fast, so that isn't what you're looking for. You basically need a cenrifugal fan, but operating as a turbine. You can arrange to discharge the air through only part of the perimeter of the turbine to match the load characteristics.
You're right, except that while he THINKS he needs high torque, what he really needs is high rpm and power output. The reduction gear takes care of the torque. But in any case, I'm not sure a pneumatic tool is something that can really be made at home.
 
Originally posted by zydubion
The application is for a small shop tool. The diameter of the turbine would be approximately 1.5 inches, while thickness should be less than 1/4 inch. Compressed air will enter the outer edge of the turbine via a nozzle. The output of the turbine will be interconnected to a substantial gear reduction and finallly to the work.

from Russ
But in any case, I'm not sure a pneumatic tool is something that can really be made at home.

I agree. I would try to modify an existing device before re-inventing the wheel. There are plenty of pneumatic tools available for consideration. I would bet that one of them already fits the design criteria; ie. pressure, flow, [the total work required], in addition to considerations like the maximum duty cycle; and some other factors like maximum momentary toque and impulse, speed, etc.
 
From his further description it sounds like he needs a compressed air motor, such as used in a garage, which is a vane type motor, and not a turbine at all.
 
Perhaps I posted my original question incorectly. Sorry. What I should have said was that I am looking for a blade design that provides the greatest efficiency within the air motor or turbine itself. I want high torque at the air motor output and will of course increase that torque signigicantly via the gear reduction. I am looking for the most efficient use of the input air via a proven blade design. Your reply posts are appreciated.
 

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