# Calculating turbine RPM in a pipe with known air velocity and diameter

• matth6197
In summary, the conversation discusses the methods for calculating the turbine RPM in a closed pipe, taking into account factors such as air velocity, pipe diameter, resistive torque, and blade pitch. The participants also mention the need to consider the lift on each blade, the number of blades, and the effects of spinning blades on the incoming fluid.
matth6197
Hello,

I am trying to calculate the turbine RPM for a turbine in a closed pipe. I know the air velocity and pipe diameter. Can this be done?

Al-Layth
Welcome, @matth6197 !

The lighter the resistive torque or resistance at the shaft of the turbine the higher its rotational speed should be.

Is your turbine just a propeller or a fan blade. If so, then the pitch of the blades is the most significant factor in RPM.

Al-Layth and russ_watters
I hope somebody posts a detailed answer for how this calculation is done. I am dealing with a similar problem for wind turbines.

I expect you will somehow need to calculate the lift on each turbine blade multiply by the number of them and model it as a circular motion problem. but then you also need to take into account the change of lift per blade due to the fact the blade will spin, (whereas it was stationary at first) and also the effects of the spinning blades on the incoming fluid as well. All issues currently beyond my modelling abilities

## What is the formula for calculating turbine RPM in a pipe?

The formula for calculating turbine RPM in a pipe is: RPM = (V / D) * 231, where V is the air velocity in feet per minute and D is the diameter of the pipe in inches.

## What units should be used for the air velocity and pipe diameter?

The air velocity should be measured in feet per minute, and the pipe diameter should be measured in inches.

## Can this formula be used for any type of turbine?

Yes, this formula can be used for any type of turbine as long as the air velocity and pipe diameter are accurately measured.

## Are there any other factors that should be considered when calculating turbine RPM in a pipe?

Yes, other factors such as air density, temperature, and pressure should also be taken into account for a more accurate calculation. Additionally, the formula assumes that the air flow is steady and the turbine is operating at its maximum efficiency.

## Is this formula applicable for both horizontal and vertical pipes?

Yes, this formula can be used for both horizontal and vertical pipes as long as the air velocity and pipe diameter are measured at the same point in the pipe. However, for vertical pipes, the formula may need to be adjusted to account for the effects of gravity on the air flow.

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