How does torque make a turbine rotor turn?

A turbine rotor turns because a moving fluid—such as steam—exerts a force on the attached vanes or blades in the tangential direction, creating the torque necessary for rotation. This process relies on the principle that when a mass of fluid changes its velocity, it exerts a force proportional to the rate of that change.12

The specific mechanism depends on the blade design:

• Impulse Blading: Stationary nozzles accelerate the fluid, increasing its kinetic energy. As this high-velocity fluid strikes the rotor blades, the energy is extracted to produce work without a pressure drop across the blades.2
• Reaction Blading: The fluid undergoes a pressure drop as it passes through both the stationary and rotating passages. This change in pressure exerts a net force in the tangential direction, which turns the rotor.2

In both cases, the rotor acts as a mechanical component that converts the fluid's energy into the rotary motion of the shaft. The blades must be aerodynamically shaped to manage these forces efficiently while withstanding centrifugal stresses.32