Rotor blade thrust - torque and angular velocity

In summary, the conversation discusses the relationship between angular velocity, torque, thrust, and power in a propeller system. It is noted that rotational speed is linearly related to airflow while thrust is a square function of rotation rate. Torque is also a square function of rotation rate due to aerodynamic drag. The power required to turn the propeller is calculated as the product of angular velocity and torque, while the power available to move the plane is affected by the efficiency of the propeller. The conversation also mentions that the efficiency of the propeller can vary with different flight conditions, making it a non-independent variable. The equation presented is not useful for testing a model plane prop on a bench.
  • #1
ChromeBit
27
0
Imagine a motor, spinning a rotor blade around and around and around and around and around...

How does the angular velocity of the rotor blade, and the torque affect the thrust produced?
 
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  • #2
Rotational speed is linearly related to airflow and airflow velocity, thrust is a square function of rotation rate.

Torque is also a square function of rotation rate because torque comes from aerodynamic drag.
 
  • #3
If this were a prop attached to a plane...

Angular velocity * Torque = Powerprop

That's the power required to turn the propeller. The power available to move the plane is somewhat less due to the efficiency of the prop..

Powerplane = Powerprop * Effprop

A well designed propeller might achieve 80% efficiency (with lots of caveats) but it will only achieve that under certain flight conditions.

The power required to move the plane (non accelerating flight) is roughly..

Powerplane = Thrust * Velocityplane

So with some substitutions...

Thrust = Angular velocity * Torque * Effprop/Velocityplane

The problem is not all are independent variables. For example prop efficiency will change with plane velocity.

PS: This equation is no use for testing a model plane prop on a bench (the plane velocity in that case would be zero, among other problems).
 

1. What is rotor blade thrust?

Rotor blade thrust refers to the force produced by the rotor blades of a helicopter or wind turbine. It is the force that propels the rotor blades and the object they are attached to in the opposite direction.

2. How is rotor blade thrust calculated?

Rotor blade thrust is calculated by multiplying the mass of the air being moved by the velocity at which it is being moved. This can be represented by the equation T = ρAV^2, where T is the thrust, ρ is the air density, A is the area of the rotor blades, and V is the velocity of the air.

3. What is rotor blade torque?

Rotor blade torque is the twisting force produced by the rotor blades as they rotate. It is caused by the unequal distribution of lift on the blades and is necessary to counteract the rotational inertia of the blades.

4. How is rotor blade torque related to angular velocity?

Rotor blade torque is directly proportional to angular velocity. This means that as the angular velocity increases, so does the torque. This relationship can be represented by the equation T = Iα, where T is the torque, I is the moment of inertia, and α is the angular acceleration.

5. What factors can affect rotor blade thrust and torque?

Several factors can affect rotor blade thrust and torque, including the angle of attack of the blades, air density, and the shape and size of the blades. Other factors such as wind speed, blade pitch, and airfoil design can also play a role in determining the amount of thrust and torque produced by the rotor blades.

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