What are the two main types of turbines mentioned?

• A. Impulse and Reaction
• B. Gas and Steam
• C. Radial and Axial
• D. Turbine and Compressor

Answer: (A)

Turbines are classified by how they transfer energy from the steam to the rotor. The two main types are impulse and reaction.

In an impulse turbine, the steam expands mainly in fixed nozzles before hitting the rotor blades. The rotor’s job is to redirect the high-velocity jet, so the work comes from the change in momentum of the steam. The pressure on the rotor stays nearly constant as the expansion happens in the nozzles. Pelton wheels are a classic example of this type.

In a reaction turbine, expansion occurs as the steam passes through both stationary and moving blades, so the blades themselves experience a pressure drop. The energy transfer comes from both pressure and velocity changes inside the blade rows, not just from redirecting a jet. Francis and Kaplan turbines operate on this principle.

Other terms like gas versus steam describe the working fluid, and radial versus axial describes the flow path, but they aren’t the main way turbines are categorized by how they transfer energy.