Explain the difference between impulse and reaction turbine.

The fundamental difference between impulse and reaction turbines lies in how the steam expands and transfers energy to the turbine blades. In an impulse turbine, the entire pressure drop of the steam occurs in the nozzles, which direct high-velocity jets of steam onto the turbine blades. The blades are curved to redirect the steam flow, and the force of the steam impinging on the blades causes the rotor to rotate. The pressure of the steam remains constant as it flows through the rotor blades. In contrast, in a reaction turbine, the pressure drop occurs gradually over both the stationary nozzles (or stators) and the moving rotor blades. The rotor blades are designed as airfoils, and they have converging channels. As the steam flows through these channels, it expands and accelerates, creating a reaction force that pushes the blades forward. Both impulse and reaction forces contribute to the turbine's rotation. Impulse turbines are typically used in single-stage applications or in the high-pressure stages of multi-stage turbines, while reaction turbines are commonly used in the low-pressure stages where large volumetric flow rates are encountered.