When the steam pressure drop occurs only in the stationary steam passages, the turbine is known as:

When the steam pressure drop occurs only in the stationary steam passages, the turbine is known as:

• A. An impulse turbine
• B. A reaction turbine
• C. A Parsons turbine
• D. A single stage turbine

Answer: (A)

In an impulse turbine, the steam’s pressure is allowed to drop mainly in stationary passages before the rotor. The high-pressure steam expands in fixed nozzles, turning into a high-velocity jet. As this jet strikes the rotor blades, it transfers energy through a change in momentum (impulse) rather than a further pressure drop across the moving blades. The rotor blades themselves see only a small pressure change; the work comes from pushing the steam to change its direction and speed. If the pressure were dropping mainly across the moving blades, it would be a reaction turbine, where energy transfer occurs through pressure changes in both stationary and moving blades. The term Parsons turbine refers to a historical design that combines features of both concepts, but the key trait described—pressure drop confined to stationary passages—points to an impulse turbine.

In an impulse turbine, the steam’s pressure is allowed to drop mainly in stationary passages before the rotor. The high-pressure steam expands in fixed nozzles, turning into a high-velocity jet. As this jet strikes the rotor blades, it transfers energy through a change in momentum (impulse) rather than a further pressure drop across the moving blades. The rotor blades themselves see only a small pressure change; the work comes from pushing the steam to change its direction and speed.

If the pressure were dropping mainly across the moving blades, it would be a reaction turbine, where energy transfer occurs through pressure changes in both stationary and moving blades. The term Parsons turbine refers to a historical design that combines features of both concepts, but the key trait described—pressure drop confined to stationary passages—points to an impulse turbine.